JET Manual 38 version 2_1_4298920_01.pdf

JET Manual 38 WPS-Basic Laboratory Training and Fluid QA/QC Reference: Version: Release Date: EDMS UID: Produced: Owner: Author:

InTouch content ID# 4298920 2.1 15-Oct-2014 1656171227 15-Oct-2014 16:46:35 WS Training & Development Lisette Anabella Garcia Sanchez

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Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.

PPCG, WS, SFE, JET Manual 38

WS Training & Development\Lisette Anabella Garcia Sanchez\InTouch content ID# 4298920\2.1\Release Date:15-Oct-2014\EDMS UID: 1656171227\Produced: 15-Oct-2014 16:46:35

JET Manual 38 / Legal Information

Legal Information Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved. This work contains the confidential and proprietary trade secrets of Schlumberger and may not be copied or stored in an information retrieval system, transferred, used, distributed, translated or retransmitted in any form or by any means, electronic or mechanical, in whole or in part, without the express written permission of the copyright owner. Trademarks & Service marks Schlumberger, the Schlumberger logotype, and other words or symbols used to identify the products and services described herein are either trademarks, trade names or service marks of Schlumberger and its licensors, or are the property of their respective owners. These marks may not be copied, imitated or used, in whole or in part, without the express prior written permission of Schlumberger. In addition, covers, page headers, custom graphics, icons, and other design elements may be service marks, trademarks, and/or trade dress of Schlumberger, and may not be copied, imitated, or used, in whole or in part, without the express prior written permission of Schlumberger. A complete list of Schlumberger marks may be viewed at the Schlumberger Oilfield Services Marks page: http://markslist.slb.com Marks of Schlumberger include but may not be limited to CLEAN SWEEP*, ClayACID*, ClearFRAC*, DAD*, DGA*, EB-Clean*, EZEFLO*, FracCADE*, GelSTREAK*, LCA*, MSR*, MaxCO3 Acid*, NARS*, OCA*, OilSEEKER*, PCM*, POD*, SDA*, SXE*, SuperX*, ThermaFRAC*, VDA*, YF GO*, YF*.

Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


JET Manual 38 / Document Control

Document Control Owner:

WS Training & Development

Author:

Lisette Anabella Garcia Sanchez

Reviewer:

Samuel Danican, Sylvie Daniel; Olesya Levanyuk, Bruce MacKay, Salim Taoutaou

Approver:

Fabricio Moretti, Steve Uren

Contact Information Name: LDAP Alias:

WS Training & Development WS-PPC-TechCom

Revision History Version Date

Description

Prepared by

2.1

15-Oct-2014 Updated chemical name.

2.0

28-Aug-2012 Document updated as per ticket 5774619 and Author: Lisette Anabella Garcia transferred to EDMS. Sanchez

1.0

05-Jun-2007 Initial release of the manual.

Author: Daphne Chang (TechCom)

Author: WS Training & Development



iv

JET Manual 38 / Table of Contents

iv

Table of Contents Foreword

________________________________________________________

viii

1 1.1

Introduction ____________________________________________________ Learning Objectives __________________________________________

1-1 1-1

2 2.1 2.2 2.3 2.4

Safety Considerations __________________________________________ Personal Protective Equipment _______________________________ Emergency Equipment _______________________________________ Chemical Spills ______________________________________________ Key Service Quality Requirements (KSQR) ____________________

2-1 2-1 2-2 2-2 2-3

Laboratory Truck and Technician

_______________________________

3-1

4 4.1 4.2 4.3

QA on Location ________________________________________________ Water Tests __________________________________________________ Gel Tests ____________________________________________________ Other QA Tasks while Pumping _______________________________

4-1 4-1 4-2 4-3

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12

Typical Laboratory Tests _______________________________________ Water Analysis _______________________________________________ Linear Fluid Viscosity ________________________________________ Vortex Closure ______________________________________________ Fracturing Fluid Crosslink Delay _____________________________ Static Gel Break Test ________________________________________ HPHT Gel Rheology Tests ___________________________________ Fracturing Sand Sieve Analysis ______________________________ Proppant Turbidity Test ______________________________________ Silt Turbidity Test ____________________________________________ Proppant Sphericity and Roundness Test _____________________ Fluid Compatibility with Resin-Coated Proppants (RCP) Test ___ Vapor Pressure Test _________________________________________

5-1 5-1 5-13 5-14 5-16 5-18 5-20 5-22 5-25 5-26 5-27 5-28 5-29

3

6 6.1 6.2 6.3 6.4 6.5 6.6 6.7

Hydraulic Fracturing Fluids ____________________________________ 6-1 Preparing Linear Gel Fluids ___________________________________ 6-1 Preparing YF100HTD Fluids __________________________________ 6-2 Preparing YF100FlexD Fluids _________________________________ 6-4 Preparing YF800HT Fluids ___________________________________ 6-6 Preparing YF100LG Fluids ___________________________________ 6-8 Preparing YF100LGD Fluids _________________________________ 6-10 Determining Crosslink Delay Time ___________________________ 6-12



v

JET Manual 38 / Table of Contents

6.8 6.9 6.10 6.11

v

Preparing ThermaFRAC Fluids ______________________________ Preparing YF GO V Fluids ___________________________________ Preparing SuperX Emulsion (SXE) ___________________________ Preparing ClearFRAC XT Fluids _____________________________

6-12 6-15 6-17 6-18

7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8

Preparing Matrix Acidizing Fluids ______________________________ Preparing Hydrochloric Acid (HCl) _____________________________ Mixing Intensified Acid _______________________________________ Mixing ClayACID _____________________________________________ Mixing Mud Acid _____________________________________________ Mixing Organic Mud Acid _____________________________________ Preparing Organic ClayACID _________________________________ Preparing Alcoholic Acid ______________________________________ Mixing Dynamic Acid Dispersion (DAD) ________________________

7-1 7-1 7-2 7-3 7-5 7-7 7-8 7-9 7-9

8 8.1 8.2 8.3

Quality Assurance/Quality Control (QA/QC) Practices __________ Fracture Fluid QA/QC ________________________________________ Acidizing fluid QA/QC ________________________________________ Fluid Additives QA/QC _______________________________________

8-1 8-1 8-3 8-4

References

9-1

9 10

_____________________________________________________

Check Your Understanding

____________________________________


10-1


vi

JET Manual 38 / List of Figures

List of Figures 2-1 2-2 3-1 3-2 3-3 5-1 5-2 5-3 5-4 6-1 6-2

Key Service Quality Requirements for Fracturing ____________________ 2-4 Key Service Quality Requirements for Matrix Acidizing _______________ 2-5 Field Laboratory Truck _____________________________________________ 3-1 Field Quality Assurance/Quality Control (QA/QC) Kit _________________ 3-2 Laboratory Technician Hard at Work ________________________________ 3-3 HACH DR/2000 Spectrophotometer with Two Sample Cells __________ 5-5 High-Pressure, High-Temperature (HPHT) Viscometers _____________ 5-20 ASTM Standard Sieves and Sieve Shaker__________________________ 5-23 Sphericity Versus Roundness _____________________________________ 5-27 Sample Linear Gel_________________________________________________ 6-1 Sample Crosslinked Gel ___________________________________________ 6-4


vi


vii

JET Manual 38 / List of Tables

List of Tables 5-1 5-2 5-3 6-1 6-2 7-1 7-2 7-3 7-4 7-5 7-6 7-7

Alkalinity Indicators ________________________________________________ 5-7 Specific Gravity (SG) of Fluid Versus Amount of Sample _____________ 5-7 Recommended Sieve Sizes for Fracturing Sands ___________________ 5-24 Quantities of J511 in YF100 LGD __________________________________ 6-11 J518 and Activator for YF GO V gel ________________________________ 6-16 Acid Systems Most used by Schlumberger __________________________ 7-1 Dilutions of Concentrated Hydrochloric acid _________________________ 7-2 Formulations for ClayACIDs ________________________________________ 7-5 Formulations for Low-Temperature ClayACIDs_______________________ 7-5 Mud Acid Formulations_____________________________________________ 7-6 OCA Formulations _________________________________________________ 7-8 Conditions for Using OCA Formulations _____________________________ 7-8


vii


viii JET Manual 38 / List of Tables viii

Intentionally Blank

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i

JET Manual 38 / Foreword

Foreword New releases of this document supersede any other version. The most current version of the document is in www.InTouchSupport.com. If you have a printed copy, check the "Release Date" against the content in InTouch to be sure you have the most current version. This document is OBSOLETE when printed.


i

Well Services, PPCG, PPC, foreword


1-i

JET Manual 38 / Introduction

1

Introduction

1.1

Learning Objectives

____________________________________________


1-i

1-1


1-1


1

1-1

Introduction PPCG, WS, SFE, JET Manual 38

Stimulation treatments restore or enhance the productivity of a well. Fracturing treatments occur above the fracture pressure of the reservoir formation to create a highly conductive flow path between the reservoir and the wellbore. Matrix treatments occur below the reservoir fracture pressure to restore the natural permeability of the reservoir following damage to the near-wellbore area. The stimulation fluid is a critical component of the stimulation treatment. In fracturing, the fracturing fluid function is to open the fracture and to transport propping agent along the length of the fracture. In matrix stimulation, the main acid function is to etch the formation, creating highly conductive paths (wormholes), or removing damage. To ensure the fluid, proppant and acid pumped are of the best quality and to maintain the quality during the treatment, the laboratory technician must perform a variety of tests. This module introduces basic field and laboratory tests that employees performing the fluid tests should know.

1.1

Learning Objectives The objective of this manual is to introduce you to Well Productivity Services (WPS) basic laboratory training and fluid quality assurance/quality control (QA/QC). After reading this manual, you should be able to do the following: • Perform water analyses. • Understand Fann® Model 35 viscometer operation and perform gel viscosity measurement. • Understand the vortex closure test. • Perform the fracturing fluid crosslink delay test. • Perform the static gel break test. • Understand Fann Model 50-type viscometer operation and perform an HPHT gel rheology test. • Perform sand sieve analysis. • Prepare hydraulic fracturing fluids. • Prepare matrix acidizing fluids. • Understand fracturing fluids QA/QC.



1-2


Note Although the Fann brand is stated here, Chandler (3500 or 5550) or Grace (M5600) instruments may also be used. Refer to specific Chandler or Grace instrument manual for operating details.


1-2


2-i

JET Manual 38 / Safety Considerations

2 2.1 2.2 2.3 2.4

2-i

Safety Considerations Personal Protective Equipment _________________________________ Emergency Equipment _________________________________________ Chemical Spills ________________________________________________ Key Service Quality Requirements (KSQR) _____________________


2-1 2-2 2-2 2-3


2-1


2

2-1

Safety Considerations PPCG, WS, SFE, JET Manual 38

All employees working in a stimulation laboratory must follow specific rules and procedures to prevent injuries and loss of equipment. All Well Services (WS) and Oilfield Services (OFS) safety standards must be complied with. All personnel must comply with WS QHSE Std 24: Laboratory Operations, InTouch content ID# 3313702.

2.1

Personal Protective Equipment Proper personal protective equipment (PPE) should be worn while working in the laboratory. • Eye protection – Safety glasses with fixed side shields are required at all times as minimum eye protection (this requirement does not apply to offices, restrooms, or other protected areas not in the laboratory working area). – Indirect vented chemical goggles must be worn when handling chemicals such as cement, unless these chemicals are in sealed containers. – Face shields must be worn when handling hot liquids, acids, or liquids that are under pressure, or working with flammable liquids where the flash point is less than 100 degF [38 degC]. – Visitors must wear safety glasses with side shields and laboratory coats while in the laboratory work areas. • Protective clothing – Laboratory coats with long sleeves must be worn as the minimum protective clothing. – Rubber or plastic protective aprons must be worn, depending on the type of chemical. Read the material safety data sheet (MSDS) for each chemical for the protective clothing requirements. – Types of clothing that allow exposure to a large area of skin must not be worn in a laboratory (e.g., sleeveless tops, short skirts, or short pants).



2-2


2-2

• Other requirements – Safety boots are not required in the laboratory. Shoes that provide protection from liquids must be worn, such as a leather shoe that covers the foot. Sandals and open shoes are not permitted. – Gloves must be worn when handling chemicals, according to the MSDS. Refer to SLB QHSE Standard S003 (Personal Protective Equipment), InTouch content ID# 3260259, for more information.

2.2

Emergency Equipment Every WS laboratory must have the following emergency equipment available: • at least one eyewash station and one emergency shower • fire extinguishers that are easily accessible in case of fire • a complete first aid kit • fire blankets available in any laboratory where tests are performed with flammable liquids • Chemical spill control kits; the kits must include rubber gloves, absorbent material or spill booms, disposal bags or containers with labels. • easy access to exits so that personnel can leave the laboratory in case of a fire • emergency numbers and procedures displayed at the entrance to the laboratory.

2.3

Chemical Spills The following lists the precautions that must be taken for chemical spills. • Each laboratory and laboratory field van must be equipped with the spill disposal kit.



2-3


2-3

• A spill response plan should be prepared that follows this general outline: – Make sure all personnel are removed from the area. – If flammable or combustible fluids are used, shut off or remove all possible sources of ignition. – Stop the chemical discharge. – Apply absorbent material to control all free liquids and place any material into a disposal container found in the spill disposal kit. – Add a label to the disposal container that shows the contents and date. – Place the container with other chemicals ready for disposal. – Report the spill to the health, safety, and environment (HSE) representative. • Chemicals must not be put into a sink drain or any drain that is connected to a sewer or waste water drainage system. • All drain pipes must comply with local regulations. The contents of all drains must be analyzed every 12 months. The data must be recorded and kept on file. The Schlumberger mercury-free policy prohibits mercury anywhere in the laboratories; this includes a prohibition of mercury thermometers.

2.4

Key Service Quality Requirements (KSQR) The Well Services - Key Service Quality Requirements (KSQR), InTouch content ID# 4147783, detail the steps that must be taken to ensure that fracturing (Figure 2-1) and matrix acidizing (Figure 2-2) jobs are performed right the first time. It is crucial to follow these requirements for successful job preparation and execution. Additionally, base fluid laboratory testing and proppant testing must be done for ALL jobs as per Key Service Quality Testing Requirements (Fluids and Proppant), InTouch content ID# 3051128. KSQRs are periodically reviewed and updated. Refer to the respective InTouch pages for the latest KSQRs. The job must be pumped as designed. Any deviation from original job procedure requires that SLB QHSE Standard S010 (MOC and Exemptions), InTouch content ID# 3260269, and SLB QHSE S010, WS Appendix: Exemptions, InTouch content ID# 3999148 be followed.



2-4


Figure 2-1: Key Service Quality Requirements for Fracturing


2-4


2-5


Figure 2-2: Key Service Quality Requirements for Matrix Acidizing


2-5


3-i JET Manual 38 / Laboratory Truck and Technician

3

Laboratory Truck and Technician

Private


3-i


3-1

JET Manual 38 / Laboratory Truck and Technician

3

3-1

Laboratory Truck and Technician PPCG, WS, SFE, JET Manual 38

A laboratory truck (Figure 3-1) or similar dedicated laboratory unit, equipped with basic fluid quality testing tools (Figure 3-2) must be present at the job site during a fracture treatment.

Figure 3-1: Field Laboratory Truck



3-2


3-2

A

D B

E

C

N

F

G

M Field QA/QC kit L

K

I

H

J

Figure 3-2: Field Quality Assurance/Quality Control (QA/QC) Kit

Key: • A: Mud balance • B: Water bath • C: Balance • D: Digital titrator • E: Retort kit • F: Hydrometers, graduated cylinders, syringes, flasks, beakers, sample bottles • G: Stopwatch • H: Process controlled rheometer • I: Variable speed mixer • J: Emulsion stability meter • K: Conductivity meter, remote laser thermometer, dry probe pH meter • L: Bacteria luminometer • M: Reagents • N: Production screen tester



3-3


3-3

Fluid samples gathered from the field blending equipment, or frac tanks if batch mixed, are checked for quality control. On land-based fracture treatments, the fluid is most often mixed in a PCM* (precision continuous mixer) and supplied to a POD* (programmable optimum density) blender. The QA that can be performed with this truck in the field laboratory ensures that the treatment is executed as designed. Simple QA steps can greatly increase the odds of success for a hydraulic fracturing treatment. The laboratory technician (Figure 3-3): • works under the direction of the job supervisor to collect samples and perform fluid quality control • must understand the principles of stimulation and fluid rheology • must be able to calculate and prepare solution concentrations and additives • checks the quality of the water before gel is prepared • collects samples for testing and troubleshoots all problems of hydration, gel loading or crosslinking.

Figure 3-3: Laboratory Technician Hard at Work



4-i

JET Manual 38 / QA on Location

4 4.1 4.1.1 4.1.2 4.2 4.3

4-i

QA on Location Water Tests ____________________________________________________ Iron Concentration Test _______________________________________ Bicarbonate Concentration ___________________________________ Gel Tests _______________________________________________________ Other QA Tasks while Pumping ________________________________


4-1 4-1 4-2 4-2 4-3


4-1


4

4-1

QA on Location PPCG, WS, SFE, JET Manual 38

The following are quality assurance (QA) tasks that must be performed on location before pumping the stimulation treatment.

4.1

Water Tests Note Laboratory personnel must ensure that reagents, buffers, and chemicals are in date, and that all pH meters must be calibrated before use. Tests must be performed on the mix water for: • temperature • pH • specific gravity (SG) • iron concentration • bicarbonate concentration. You will need a sample of water from each tank (3 to 5 L). At least 1 L of water should be reserved in case additional testing is necessary in the district laboratory after the fracture, such as in the case of a screenout. Test the water parameters to ensure that they are within the range of acceptable values for the fluid pumped.

4.1.1

Iron Concentration Test Perform this test using a HACH iron test kit as follows: 1. Insert the iron color disk into the comparator. 2. Fill a clean color test tube to the 5-mL mark, add the chemical packet to the tube and shake to mix. An orange color will develop if iron is present. 3. Insert the tube of prepared sample into the right top opening of the comparator.



4-2


4-2

4. Fill the other color viewing tube with an untreated water sample. Place it in the left top opening of the color comparator. 5. Hold the comparator up to a light source and view through the openings in front. Rotate the disc to obtain a color match. Read the mg/L iron (Fe) concentration through the scale window. 6. If the concentration is greater than 10 mg/L, perform another test with a diluted sample as follows: a. Use a 1-mL sample of water to be tested and 4 mL of distilled or deionized (DI) water. b. Follow the procedure in Steps 1 through 5, but multiply the results by 5.

4.1.2

Bicarbonate Concentration To test for bicarbonate concentrations: 1. Measure 100 mL of undiluted sample into a 300-mL glass beaker. 2. Insert a clean delivery tube into the titration cartridge (1.6N H2SO4). Attach the cartridge to the titrator body. 3. Hold the digital titrator with the cartridge tip pointing down. Turn the delivery knob to eject air and a few drops of titrant. 4. Reset the counter to zero and wipe the tip. 5. Add the contents of one Bromocresol green-methyl red indicator powder packet to the glass beaker and swirl to mix. 6. Titrate with sulfuric acid to a light pink color. As the titration progresses, the colors will change from light greenish blue-gray to light pink. 7. Record the value shown on the digital titrator as the total bicarbonate (the units are in mg/L as CaCO3).

4.2

Gel Tests The linear gel must be tested before beginning the job. A linear gel sample prepared with the actual water and chemical samples on location must be mixed and analyzed before job fluid mixing commences. Use the procedure detailed in Section 6.1: Preparing Linear Gel Fluids, to check the viscosity of the gel using the Fann® 35-type viscometer and compare the tested viscosity and temperature with the expected ranges. When this sample meets the specification, begin initial mixing with the PCM or GelSTREAK* and perform the following tests. 1. Measure the pH of the linear gel and record it. Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


4-3


4-3

2. Divide the linear gel into two beakers of 250 mL each. 3. Make a crosslinked solution using the volumes recommended in laboratory testing procedure. Ensure you check the specific gravity and pH of activator and specific gravity of the breaker sample. 4. Start the mixer at a low speed and add the chemicals. 5. Measure and record the time it takes for the fluid to have a vortex closure in the mixer and the time it takes for the fluid to have a good hang lip (crosslink). 6. Test and record the pH of the crosslinked fluid. 7. For borate fluid systems only: Perform a shear test of the fluid by submitting it to high speeds in the mixer and ensuring that the fluid will heal itself after shear. 8. Perform a breaker test at bottomhole temperature (BHT). Use concentrations dictated by the latest laboratory report to add the correct amount of breaker to a beaker of crosslinked gel. Place the sample into a water bath at bottomhole temperature. Test and record the time until the gel starts to break.

4.3

Other QA Tasks while Pumping The following are common QA tasks while pumping: • Throughout the job, linear gel should be continually checked for viscosity to confirm the proper gel loading. • Samples should be taken from the outlet of the blender or fracture pumps to test the delay time of the crosslinked fluid as well as pH, temperature, BHT stability, and break testing (water bath). • The physical quantities of all liquid and dry additives should be continually checked throughout the job and compared to the designed amount to be pumped.



5-i

JET Manual 38 / Typical Laboratory Tests

5 5.1 5.1.1 5.1.1.1 5.1.1.2 5.1.1.3 5.1.2 5.1.3 5.1.4 5.1.4.1 5.1.4.2 5.1.5 5.1.5.1 5.1.6 5.2 5.2.1 5.3 5.4 5.5 5.6 5.7 5.7.1 5.7.2 5.8 5.9 5.10 5.11 5.12

5-i

Typical Laboratory Tests Water Analysis _________________________________________________ Testing pH, Specific Gravity, and Turbidity _____________________ Testing pH _______________________________________________ Testing Specific Gravity ___________________________________ Testing Turbidity __________________________________________ Testing Alkalinity (Indicator Method) ___________________________ Testing Chloride _____________________________________________ Testing Calcium and Magnesium ______________________________ Testing Calcium __________________________________________ Testing Magnesium _______________________________________ Testing Sulphate, Barium, Iron, and Potassium ________________ Testing Iron (HACH Method) _____________________________ Testing Sodium (Calculation Method) _________________________ Linear Fluid Viscosity _________________________________________ Determining Water-Base Fluid Linear Gel Viscosity ____________ Vortex Closure ________________________________________________ Fracturing Fluid Crosslink Delay ______________________________ Static Gel Break Test __________________________________________ HPHT Gel Rheology Tests _____________________________________ Fracturing Sand Sieve Analysis _______________________________ Sampling Techniques _______________________________________ Sand Sieve Analysis (Modified API Method) __________________ Proppant Turbidity Test _______________________________________ Silt Turbidity Test ______________________________________________ Proppant Sphericity and Roundness Test _____________________ Fluid Compatibility with Resin-Coated Proppants (RCP) Test __ Vapor Pressure Test ___________________________________________


5-1 5-2 5-2 5-3 5-4 5-6 5-7 5-8 5-8 5-9 5-10 5-11 5-12 5-13 5-13 5-14 5-16 5-18 5-20 5-22 5-23 5-24 5-25 5-26 5-27 5-28 5-29


5-1


5

5-1

Typical Laboratory Tests PPCG, WS, SFE, JET Manual 38

Several tests are commonly performed at the district laboratory before the job. For details and procedures on the required tests for each type of stimulation job, refer to Stimulation District Lab Procedures, InTouch content ID# 5563263, and Key Service Quality Testing Requirements (Fluids and Proppant), InTouch content ID# 3051128. Typical laboratory tests include: • Water analysis • Linear fluid viscosity • Vortex closure • Fracturing fluid crosslink delay • Static gel break test • HPHT gel rheology • Fracturing sand sieve analysis • Proppant turbidity test • Silt turbidity test • Proppant sphericity and roundness • Fluid compatibility with resin-coated proppants (RCP) • Vapor pressure test

5.1

Water Analysis The oil industry uses water analysis for quality control, formation identification, compatibility studies, and environmental evaluations. The following procedures have been developed to perform the necessary water analyses. • pH testing (meter) and temperature • specific gravity (SG) testing (hydrometer and SG bottle method) • turbidity testing (HACH method)



5-2


5-2

– total dissolved solids (TDS) (by gravimetric analysis) – ion concentrations (e.g., chlorides, calcium, magnesium, sulfate, iron, etc.)

5.1.1

Testing pH, Specific Gravity, and Turbidity You will need the following items to test water for pH, specific gravity, and turbidity: • pH meter and calibration solutions • SG bottle • balance • filtering apparatus and accessories (filter paper, vacuum pump and funnel assembly).

5.1.1.1

Testing pH The normal pH range for brines is between 6 to 8. A low pH may indicate spent acid, whereas a high pH may indicate contamination by mud, filtrate or bacteria. Some of the constituents that control the pH of water are dissolved solids, precipitation of iron, carbon dioxide, bicarbonate, borate, and hydrogen sulfide. The pH of water can strongly affect the hydration of a polymer and mechanism of some crosslinking reactions. It should be tested using pH paper and more preferably a digital pH meter. pH paper is appropriate for a quick check on most fluids, providing the paper is not beyond its shelf life and has not been exposed to extreme heat or sunlight. The pH paper test procedure is very simple: 1. Dip a piece of pH paper into the water sample. 2. Match the color of the paper with the chart on the package of pH paper. For a more accurate reading, a pH meter should be used: 1. Calibrate the pH meter as described in the pH meter manual. 2. Shake the water sample to homogenize it. 3. Insert the pH probe into the water sample. 4. Read the pH on the meter screen after the reading stabilizes. Check the temperature. Record the pH and temperature.



5-3


5-3

Note • The closer the pH is to 8.0, the slower the gel will hydrate. • If the pH is close to or equal to 8.0, it is recommended to buffer with acid. • If the pH is above 8.0, the water must be buffered. • If buffering the tank, add 1 galUS 36% HCl per 20,000 galUS and check the pH. If the pH is at or above 7.5, add HCl by the quart until the pH is below 7.5. 5.1.1.2

Testing Specific Gravity Specific gravity is the ratio of the weight of material to the weight of water, or the density of the material to the density of water. Freshwater has a specific gravity of 1.000. The higher the specific gravity, the heavier the liquid will be. Specific gravity can be used to differentiate hydrocarbons (condensate) from water. A hydrometer is used to measure specific gravity. There are two different procedures that can be performed to test water for specific gravity: the hydrometer procedure and the SG bottle procedure. Hydrometer procedure (the preferred method in the field): 1. Fill a graduated cylinder with the fluid to be tested. Use a 100-mL cylinder for a 7-in hydrometer and 250-mL cylinder for a 12-in hydrometer. 2. Carefully drop the hydrometer into the liquid with a slight spin. 3. Read the value for specific gravity where the top of the fluid intersects one of the lines on the hydrometer. 4. The value for specific gravity should be corrected for temperature by using the temperature correction table (rule of thumb: Add 0.0002 to the SG for every degree above 60 degF). HCl strength can also be determined from its specific gravity and compared to the chart in the acid strength chart found in the Field Data Handbook. Use this equation to relate API (American Petroleum Institute) gravity to specific gravity:

SG =

141.5 131.5 + API

AP1 =

141.5 −131.5 (SG ) SG



5-4


5-4

Note The higher the API gravity, the lighter the fluid. SG Bottle procedure: To determine the SG using the SG bottle:

Note Clean everything you used for this test with deionized (DI) water. 1. Weigh the empty SG bottle and record the weight as W1. 2. Fill the bottle with DI water until water runs out of the capillary and cap it. 3. Weigh the bottle containing DI water and record the weight as W2. 4. Clean the bottle to be used for the water sample three times, fill it with the water sample, and cap it. 5. Weigh the bottle containing the water sample and record the weight as W3. Calculate the SG of the sample water from the formula:

SG = 5.1.1.3

W 3 − W1 W 2 − W1

Testing Turbidity Make sure you use unfiltered water for this test. To test water for turbidity: 1. Switch on the HACH DR/2000 spectrophotometer (Figure 5-1) and enter the method number 750.



5-5


Figure 5-1: HACH DR/2000 Spectrophotometer with Two Sample Cells

2. Adjust the wavelength to 450 nm for this test. 3. Fill a clean sample cell with 25 mL of the water sample and another clean sample cell with 25 mL of DI water. 4. Insert the DI water sample cell into the cell holder and close the shield. 5. Press ZERO to zero the machine. 6. Place the sample cell with the sample water into the holder and close the shield. 7. Press READ/ENTER to obtain the FTU water turbidity. 8. Turn off the HACH DR/2000 and clean up the cells with DI water. Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.

5-5


5-6


5.1.2

5-6

Testing Alkalinity (Indicator Method) Fluids should be tested for alkalinity; bicarbonates, carbonates, and hydroxide can all increase alkalinity. Bicarbonate measurement is very important for fracture fluid quality control. Fracturing fluids require various bicarbonate concentrations depending on the specific fluid. High bicarbonate concentrations will tend to slow gel hydration and delay fluid crosslink. If high bicarbonate concentrations are encountered, the fluid may be treated with calcium chloride (S001), which will react with bicarbonate ion. Calcium carbonate will precipitate, thereby reducing the dissolved bicarbonate concentration. The precipitate will not interfere with the fluid. The other reason to determine the bicarbonate concentration is to identify the water source. High bicarbonate concentrations may be characterized by a high pH or be an indication of carbonates present in the water. Most formations do not contain carbonates or hydroxides. If a water sample contains carbonates and/or hydroxide, it may be a clue to a problem in the customer’s well, possibly indicating the presence of some drilling mud contamination. To test the alkalinity, use a 50-mL sample regardless of the specific gravity. Then: 1. Add 3 drops of phenolphthalein indicator. If the sample did not turn pink, the sample does not contain carbonates or hydroxide. Continue with Step 2. If the sample did turn pink, continue to Step 5. 2. If the sample did not turn pink, add ½ dropper of methyl purple. 3. Titrate with 0.1N HCl or 0.0164 N HCl to the purple endpoint. 4. Calculate the bicarbonate concentration: • For 0.1N HCl, bicarbonate (mg/L) = mL of 0.1N HCl x 122 • For 0.0164N HCl, bicarbonate (mg/L) = mL of 0.0164N HCl x 20

Note These equations are valid only for 50-mL samples. 5. If the sample did turn pink after Step 1, titrate with 0.1 N HCl until the pink color disappears. The amount of 0.1N HCl used will be P in the calculations. 6. Add 3 drops of methyl purple.



5-7


5-7

7. If the sample turns green, titrate with 0.1 N HCl to the purple endpoint. The total amount of 0.1 N HCl used in both titrations will be T in the calculations. 8. Perform the calculations indicated in Table 5-1. Table 5-1: Alkalinity Indicators Indicator

Bicarbonate

Carbonate

Hydroxide

P <1/2T

T-2P

2P

None

P = 1/2T

None

2P

None

P> 1/2P

None

2(T-P)

2P-T

P = T

None

None

T

where: P = amount of 0.1 N HCl required to titrate sample to a colorless endpoint after adding phenolphthalein T = amount of 0.1 N HCl required to titrate samples to a colorless endpoint after adding phenolphthalein plus the amount of 0.1 N HCl required to titrate sample to the purple endpoint after adding of methyl purple bicarbonate (mg/L) = mL of 0.1N HCl x 122 carbonates (mg/L) = mL of 0.1N HCl x 60 hydroxides (mg/L) = mL of 0.1N HCl x 34.

5.1.3

Testing Chloride The chloride test is generally used to determine if the sample is formation fluid or treatment fluid. Fracturing fluids today can contain 2% KCl. The chloride content of a 2% potassium chloride solution should be approximately 9,600 mg/L. The chloride test can also be used to determine if a sample is spent acid. The characteristics of spent acid are a high chloride content and a pH of approximately 3.0 to 6.0. 1. Check SG to determine the proper sample size according to Table 5-2. Table 5-2: Specific Gravity (SG) of Fluid Versus Amount of Sample Specific Gravity

Amount of Sample, mL

1.000 to 1.003

50

1.003 to 1.020

10

1.020 and over

1

2. Dilute sample to 50 mL with distilled or DI water.



5-8


5-8

3. Add 3 to 4 drops of potassium chromate. 4. Titrate to the orange/red endpoint with 0.1N silver nitrate. Note If a sample contains H2S (it will have a rotten egg smell), heat the sample in a fume cupboard until the odor is eliminated. 5. Perform the following calculation:

Cl (mg / L ) =

3, 545 x mL of silver nitrate sample size (mL)

For concentrations of silver nitrate other than 0.1N, use this calculation:

Cl (mg / L ) =

5.1.4

mL of silver nitrate x normality of silver nitrate x 35, 500 sample size (mL)

Testing Calcium and Magnesium The following sections describe how to determine the calcium and magnesium content in the water. Magnesium and calcium are the most common sources of hardness in produced waters; any other components that may contribute to total hardness are negligible.

5.1.4.1

Testing Calcium Most produced water will have less than 15,000 mg/L of calcium. If higher concentrations of calcium are encountered, the water is almost certainly from a limestone or dolomite formation that has recently been acidized. If you suspect you might have an acid sample, check the chlorides and compare it to values int the table on chloride discussion. If less than 15,000 mg/L calcium is detected, continue the water analysis. To determine the calcium content: 1. Determine the correct sample size. The sample size depends on the SG of the fluid (refer to Table 5-2). 2. Dilute the sample (if less than 50 mL) to 50 mL with distilled water. 3. Add 3 to 4 drops NH4OH. 4. Add 2 scoops of Calver® II hardness reagent.



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5-9

5. Titrate with 0.025 M EDTA (ethylenediamine tetraacetic acid) to the blue endpoint. 6. Perform the following calculations:

Ca (Mg / L ) =

mL of 0.025 M EDTA used x 1, 000 sample size (mL)

For EDTA concentrations other than 0.025 M, use this equation:

Ca (Mg / L ) =

5.1.4.2

mL of EDTA x Molarity of EDTA x 40, 100 sample size (mL)

Testing Magnesium The magnesium test used (standard titration method) is a test for total hardness. This test assumes that the water hardness is due to dissolved magnesium and calcium only. Generally, the magnesium concentration is used for total dissolved solids (TDS) calculations to identify the water source. However, high magnesium is generally due to a recent acid treatment of a dolomite formation. The following standard titration method requires that calcium be determined before calculating the magnesium concentration. Subtract the calcium concentration from the total hardness and assume the remaining hardness is due to magnesium. Follow this procedure. 1. Determine the correct sample size. 2. Dilute to 50 mL with distilled water. 3. Add 3 to 4 drops NH4OH. 4. Add 2 scoops of Univer II hardness reagent. 5. Titrate with 0.025 M EDTA to the blue endpoint.

Note This test is for the total hardness. To find the amount of 0.025 M EDTA for magnesium, subtract the number of mL of 0.025 M EDTA used to determine calcium. This difference is the number of mL of 0.025 M EDTA used to determine the magnesium. 6. Perform the following calculation:



5-10


Mg (mg / L ) =

5-10

((mL of 0.025 M EDTA for Mg ) − (mL EDTA for Ca )) x 606 sample size (mL)

For EDTA concentrations other than 0.025 M, use this equation:

Mg (mg / L ) =

5.1.5

((mL of 0.025 M EDTA for Mg ) − (mL EDTA for Ca )) x M of EDTA x 24, 340 sample size (mL)

Testing Sulphate, Barium, Iron, and Potassium To test the quantity of sulfate, barium, iron, and potassium in the sample using the HACH DR/2000 spectrophotometer, you will need the following items: • HACH DR/2000 with accessories • DI water • SulfaVer® Reagent Powder Pillow for SO42• BariVer® 4 Reagent Powder Pillow for Ba2+ • FeroVer® Iron Reagent Powder Pillow for Fe2+/Fe3+ • potassium I/II/III reagent, for K+ • water sample. Follow this procedure. 1. Switch on the HACH DR/2000. Repeat Steps 2 through 14 for each contaminant being tested for. 2. Enter the appropriate stored program number (680 for sulphate, 20 for barium, 265 for iron, and 950 for potassium). 3. Rotate the wavelength dial until the display shows 450 nm for sulphate or barium, 510 nm for iron, or 650 nm for potassium. 4. Press READ/ENTER. 5. Pour 25 mL of sample into the sample cell. 6. Add the contents of appropriate reagent powder pillow to the sample cell (the prepared sample). Swirl to dissolve. 7. Press SHIFT TIMER. 8. When the timer beeps, fill another sample cell (blank) to 25 mL of sample with DI water. Place it into the cell holder and close the light shield. 9. Press ZERO to zero the machine.



5-11


5-11

10. Within a few minutes after the timer beeps, place the prepared sample into the cell holder. Close the light shield. 11. Press READ/ENTER. 12. Record the reading. 13. Dilute the sample if the reading flashes (over limit) and repeat the above procedures. To determine the quantity of the contaminant, use the following equation. Contaminant content (mg/L) = HACH DR/2000 reading × dilution factor (if any)

5.1.5.1

Testing Iron (HACH Method) When high iron is encountered in fracture fluid mix water, Breaker J218 (ammonium persulfate) will have an accelerated effect. In high iron environments, J218 may cause premature breaking of the fracture fluid. In addition, high iron content will interfere with the crosslinking of the fracture fluid, resulting in poor crosslink integrity. The maximum iron concentration for fracturing water ranges from 8 to 25 mg/L, depending on the fluid. During acid treatments ferric iron (Fe3+) is the major concern. When ferric iron reaches approximately 2,000 ppm in the acid system and is not 100% reduced, emulsion or sludging may be encountered. Commonly total iron is considered to be a ratio of 3:1 or 5:1 ferrous to ferric iron. The dissolved iron concentration may need to be determined after an acid job or be monitored during pickling of tubulars. In those cases much higher iron concentration would be expected. Monitoring iron concentration in returned spend acid and returned pickling acid will aid Schlumberger and the customer in determined adequate iron control for future acid treatments. • If pH is between 1 and 7 test the sample with an iron strip to determine a general range of iron concentration. • If iron concentration is zero ppm this test is sufficient. • If iron concentration is above approximately 10 ppm (10 mg/L) but below 25 ppm (25 mg/L), use the HACH Color Comparator Kit No 187. You will need a CHEMetrics kit if pH is below 1.0. Follow this procedure to determine the iron content.



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5-12

1. Fill the dilutor snapper cup to the 25 mL mark with iron-free water. 2. Fill the microtest tube halfway with your sample. 3. Holding the VACUette almost horizontally, touch the tip to the contents of the microtest tube. The tip fills completely by capillary action. 4. Completely immerse the VACUette tip into the contents of the dilutor snapper cup. Snap the tip of the ampule and wait until the VACUette fills up. The sample fills the ampoule and begins to mix with the reagent.

Note A small bubble of inert gas will remain in the ampoule to facilitate mixing. 5. Remove the VACUette from the dilutor snapper cup. Mix the contents of the VACUette by inverting it several times, allowing the bubble to travel from end to end each time. 6. After 1 minute, use the appropriate comparator to determine the level of iron in the sample.

5.1.6

Testing Sodium (Calculation Method) To determine the sodium content of the water using the results of the tests described in Sections 5.1.1 through 5.1.5, use this equation: mg/L of Na+ = 23 × (A/35.5 + B/61 + C/60 + D/17 – E/56 – F/137 – G/24 – H/40 –I/39) where: A = chloride (mg/L) B = bicarbonate (mg/L) C = mg/L of carbonate (mg/L) D = mg/L of hydroxyls (mg/L) E = mg/L of iron (mg/L) F = mg/L of barium (mg/L) G = mg/L of Magnesium (mg/L) H = mg/L of calcium (mg/L) I = mg/L of potassium (mg/L).



5-13


5.2

5-13

Linear Fluid Viscosity To determine the viscosity of linear fluids (including water-based fracturing fluids, gelled oils, and gelled acids), the Fann® Model 35 rheometer (Fann 35) is primarily used. Follow these practices to calibrate the rheometer: • Perform a full calibration the Monday of each week or each 75 hours of operation, whichever comes first. • The rheometer must be cool and clean. • The rheometer must agree with the calibration oil chart to within ±1 cP (±1 mPa·s). • If the rheometer does not calibrate, then service the unit or send out for repair as instructed by the instrument manual. • After each test, do the following: – Take off rotor and bob. Clean each piece with soap and water. – Wipe off the shaft with a damp cloth in a down motion. Do not press against the shaft-up motion pushes fluid up the shaft. – Reassemble unit ensuring that each piece is finger tight. Tightening the bob or the rotor too much can damage the shaft and torque transducer.

5.2.1

Determining Water-Base Fluid Linear Gel Viscosity To determine water-base fluid linear gel viscosity, you will need the following items: • Fann 35 viscometer with appropriate parameters (speed factor, R-B factor and spring factor) • rotor and bob • Fann 35 sample cup • fracturing fluid • thermometer • water sample.



5-14


5-14

The approach is to hydrate the polymer following the procedures in the Fracturing Materials Manual Volume I, Volume II and Volume III: Fluids, InTouch content ID# 4223817, sample the fluid, load the fluid into the Model 35 sample cup, and record the bob deflection at different rotor rotational speeds. Generally 6 rpms are available: 3, 6, 100, 200, 300, 600 rpm. 1. Power on the Fann 35. 2. Install the rotor and bob if they are not in there already. 3. Fill the sample cup to the mark with fracturing fluid. 4. Place the sample cup on the stage. The three pins on the bottom of the cup sit in three holes on the stage. 5. Raise the stage until the sample cup is at the mark on the rotor. 6. Set the Fann 35 to the desired shear rate. Note Shift gears only when the instrument is running. 7. Let the dial come to a steady reading and record the reading. 8. Measure and record the fluid temperature. 9. Compare the reading with the appropriate hydration curve. All laboratories and laboratory trucks should have the hydration curves onsite; you can also find them in the Fracturing Materials Manual Volume I, Volume II and Volume III: Fluids, InTouch content ID# 4223817. • Allow the gel to hydrate for an additional 10 minutes if the viscosity is 95% of the nominal value. • Verify that the pH and water temperature are within the prescribed limits. • Add polymer in 2-lbm/1,000 galUS increments if the viscosity is still low after 10 additional minutes of hydration and the pH and water temperature are within specification.

5.3

Vortex Closure Vortex closure is one method for estimating a crosslink time, as are the crosslink delay temperature and crosslink delay time tests. But, whereas the crosslink delay temperature or crosslink delay time tests indicate the time or temperature required to achieve a lipping fluid, the vortex closure test simply indicates the onset of viscosity development (and rarely coincides with full crosslinking). There are three distinct fluid behaviors during a vortex closure test: Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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5-15

1. The first is the linear fluid behavior. This is the initial state of the fluid and is characterized by a deep vortex. 2. The second is the viscosity increase that results in vortex closure, but does not stop fluid circulation in the blender cup. 3. The third behavior is fluid crowning, which is the formation of a dome of fluid over the center of the blender cup (over the blades). This is the point at which the fluid no longer completely circulates in the blender cup. It indicates crosslinking has occurred and an elastic lipping material has formed. It is important to determine the time to both vortex closure and fluid crowning during a vortex closure test.

Note Continuing to shear the fluid after vortex closure will degrade the thermal stability and appearance of the gel. Therefore, you must prepare a new fluid sample for breaker tests or for baseline fluid performance characterization; do not use the same fluid sample from which the vortex closure and crowning times are determined. You will need the following items to perform the vortex closure test: • Waring blender • timer • fluid to be tested, including all additives • crosslinker to be tested. To perform the vortex closure test: 1. Prepare 250 mL of the base fluid (KCl or L064, surfactants, stabilizers, and buffers for polymer fluids; the fracturing oil and the recommended additives for gelled oils). Include all additives except the crosslinker. 2. Add the base fluid to a 1-L glass Waring blender cup. Adjust the mixing speed to develop a deep vortex. The top of the blade nut should just be visible, but the flats of the blade should be covered in the fluid. 3. Simultaneously add the crosslinker/activator package and start a timer. 4. Record the time at which the vortex closes. At vortex closure, the fluid will still be circulating in the blender and will appear to fold away from the blender sides into the center of the cup. There may still be a depression in the fluid surface at the center of the cup, but the vortex that remains is very little.



5-16


5-16

5. Continue mixing the fluid. Record the time at which the fluid surface stops moving and forms a small dome at the center of the blender cup. This time is the crowning time.

5.4

Fracturing Fluid Crosslink Delay Crosslinking is a chemical reaction allowing a continuous, three-dimensional structure to form in a fluid under the right conditions. Crosslinking reactions are delayed to reduce friction pressure during pumping and to reduce the time a crosslinked fluid is exposed to high shear rates. Most metal-crosslinked polymer fluids are irreversibly destroyed when they are exposed to high shear rates after crosslinking. The delay between adding the crosslinkers and the actual crosslinking is the crosslink delay time. Any factor that affects the dissolution rate (such as temperature, concentration, shear rate, particle size distribution) will change the crosslink delay. Typically, fluids that use dissolving particles are time delayed. It is also possible to add additives that affect the interaction between the crosslinker and the polymer until the fluid temperature increases. The temperature at which crosslinking will occur is called the crosslinking delay temperature. You will need the following items to test the crosslinking delay and the crosslinking delay temperature: • Waring blender • 4 plastic cups • glass beaker • pH meter • thermometer • timer • fluid sample. There are numerous ways to determine the crosslink delay time and crosslink delay temperature of hydraulic fracturing fluids. Unfortunately, the most commonly employed methods are highly subjective. This JET manual outlines the basic procedures used for these subjective tests.



5-17


5-17

Note Be careful to follow this procedure exactly. Subtle differences in the initial conditions and the mixing steps will change the results. Sample preparation You will repeat the following steps to prepare samples for the crosslink delay time and the crosslink delay temperature tests. 1. Prepare 250 mL of the fracturing fluid following the procedure given in the relevant section of the Fracturing Materials Manual.

Note Do not add the last ingredient (typically the crosslinker and/or buffer) until the initial fluid temperature and pH are measured. 2. Measure and record the fluid temperature and pH. 3. Add the last ingredient, the crosslinker and/or buffer, to the fracturing fluid and mix in the Waring blender at 2,000 rpm for 30 seconds. The crosslink delay time measurement starts as soon as the last ingredients are added to the fluid; record this time. Measure the final fluid pH during this step. Crosslink delay temperature Follow this procedure to determine the crosslink delay temperature. 1. Transfer the entire contents of the blender cup into a glass beaker. Place the beaker into a microwave oven and heat the fluid for 10 seconds. 2. Remove the cup and briefly stir the fluid with a thermometer at a rate similar to whipping eggs with a whisk. Then, allow the thermometer to equilibrate with the fluid and record the temperature. Take 15 seconds or less for this mixing and temperature measurement step. 3. Repeat Steps 1 and 2 as necessary. Record the temperature at which the following three characteristics are evident. a. Initially, the fluid begins to thicken. It may remain linear or it may become stringy and cling to the thermometer. However it manifests this stage, the fluid is now substantially more viscous than the linear gel was. Some call the temperature at which this point is reached the initial crosslink temperature.



5-18


5-18

b. The fluid can support a pencil-thick tongue hanging off the edge of the beaker. The temperature at which it is possible to pull the tongue back into the beaker is the crosslink temperature. This is the temperature that should be used for designing the crosslink delay temperature for the treatments. c. The fluid eventually becomes dry (usually) and can support a broad, thick tongue hanging off the edge of the beaker. The temperature at which this occurs is the full dry crosslink.

5.5

Static Gel Break Test The static gel break test determines the time at which the gel breaks enough to flow back. A gel is usually considered broken enough to flow back when it has degraded to a viscosity of 20 cP (20 mPa·s) at the required temperature. This test is important for the field operation that does not have high-pressure, high-temperature (HPHT), gel break test equipment. You will need the following items to perform the static gel break test for any temperature: • 1,000 mL jar with cap • 200-mL high temperature bottles • HPHT fluid-loss cell and heating jacket • Fann 35 rheometer with proper accessories • water bath with temperature control • thermometer • stopwatch • gel and breaker sample. Follow this test procedure for temperatures less than 100 degF [38 degC]. 1. Prepare the base gel. 2. Place the required amount of breaker solution into the linear gel before adding the crosslinker solution. Dissolve J218 or J481 into a small amount of water; use equivalent amounts of J218 and J481 if J475 and J490 encapsulated breaker are used and refer to FMM Vol III - Section 4: Breakers and Breaker Aids, InTouch content ID# 4879459, for the encapsulated breaker release rate. 3. Crosslink the gel according to fluid preparation procedures that are published for that particular gel.



5-19


5-19

4. Preheat the water bath to the required temperature. 5. Pour 500 mL of gel into the jar. Replace the cap. 6. Place the jar containing the gel in the water bath to bring the sample to the required temperature. Stir it slowly while heating, to accelerate the crosslinking process. Start the timer when the temperature reaches the indicated bottomhole temperature (BHT). 7. Tighten the cap. Shake the jar vigorously every 30 minutes and visually observe the viscosity. 8. Install the Fann 35’s rotor, bob, and sample cup. Heat the sample cup. 9. Take enough of the gel from the jar to fill the sample cup and place it into the heated sample cup. 10. Place the thermometer into the sample. Watch the thermometer closely. Start testing the fluid viscosity at 170 s-1 as quickly as possible when the fluid temperature is at the required temperature (the BHT). The Fann 35 does not have heating capabilities, so the sample should be heated to BHT in the water bath. 11. Continue the process in Step 3 until fluid viscosity reaches 20 cP (20 mPa·s). Record the time required to reach this viscosity, which is the static gel break time. Follow this test procedure for temperatures greater than 100 degF [38 degC], using a HPHT fluid-loss cell. 1. Prepare the base gel. 2. Place the required amount of breaker solution into the linear gel before adding the crosslinker solution. Dissolve J218 or J481 into a small amount of water; use equivalent amount of J218 and J481 if J475 and J490 encapsulated breaker are used, and refer to FMM Vol III - Section 4: Breakers and Breaker Aids, InTouch content ID# 4879459, for encapsulated breaker release rate. 3. Crosslink the gel according to the fluid preparation procedures. 4. Preheat the heating jacket to the required bottomhole static temperature (BHST). 5. Place the crosslinked gel into the bottle and finger tighten the cap. Put the bottle with the sample into the HPHT cell containing the proper level of oil just below the bottle cap connection, to avoid oil getting into the bottle and contaminating the fluid. Keep the whole cell assembly vertical while putting the bottle into the HPHT cell. 6. Place the HPHT cell assembly with bottle/oil heating medium into the heating jacket; again, keep all components vertical. 7. Start the timer when the HPHT cell temperature reaches the indicated BHT. Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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5-20

8. Visually observe the viscosity of the fluid by cooling down the cell and taking out the bottle at the expected breaking time. Using your laboratory experience, determine whether it has broken or not. If it does not break, repeat the test with more breaker.

5.6

HPHT Gel Rheology Tests The following breaker tests are to be completed to generate or verify an appropriate breaker schedule and verify fluid stability at temperature. 1. Control fluid (fluid without breaker) at PAD stage BHT. 2. PAD fluid (with breaker, when applicable) at PAD stage BHT. 3. Additional stage testing (different stages/breaker loadings/BHTs) sufficient to successfully generate or verify a breaker schedule. A Fann Model 50-type viscometer is used for performing a crosslinked gel breaking test when a BHT above 100 degF [38 degC] is required (refer to Figure 5-2).

Figure 5-2: High-Pressure, High-Temperature (HPHT) Viscometers. Left to right: Fann 50, Chandler 5500 and Grace M5600

You will need the following items to perform this test: • High-pressure, high-temperature (HPHT) viscometer, e.g., Fann Model 50-type viscometer with appropriate parameters (speed factor, R-B factor, and spring factor). • Rotor and bob 5 or bob 5X; different bobs will have different shear rate ramps. For example, shear rate ramp corresponds to 118 rpm, 88 rpm, 59 rpm, 88 rpm, and 118 rpm with a B5 bob.



5-21


5-21

• fracturing fluid sample. To perform the HPHT gel rheology tests:

Note These steps could vary with different types of viscometers. 1. Power on the viscometer and its computer. 2. Supply water and nitrogen (N2) (usually at 450 psi (3,105 kPa) (or 800 psi (5,520 kPa) for encapsulated breakers)) after the machine is calibrated properly. 3. Prepare the crosslinked fracturing fluid as described in the specific fracturing fluid laboratory preparation procedures. 4. Activate the viscometer computer program and select Operating Menu, then Heat Bath. Type in the required temperature to start preheating the oil bath. 5. Place about 26 mL (for a bob 5) of the crosslinked gel inside the rotor cup, followed by the required amount of breaker. 6. Place approximately 26 mL more of the crosslinked gel into the rotor cup. 7. Screw the bob counterclockwise to the shaft until it is finger tight. 8. Slowly screw the rotor containing the sample to the expansion fitting until it is finger tight. 9. Take off the cover of the oil bath and close the glass door. 10. Go to the Operating Menu, and then Custom (or API). The API ramp should be one of the following: • 118 rpm (100 s-1) • 88.5 rpm (75 s-1) • 59 rpm (50 s-1) • 29.5 rpm (25 s-1) • 59 rpm (50 s-1) • 88.5 rpm (75 s-1) • 118 rpm (100 s-1) 11. Choose bob 5, interval stir rate (118 rpm), and final temperature set point. 12. Click Initial test in the operating menu followed by Yes and OK to go to ASCII FILE and report printout. Choose the options you need.



5-22


5-22

13. Follow the screens through until Perform Test appears; click it. (The instrument will automatically run until the program finishes and prints out the results. If you want to stop the machine during testing, go to the operating menu and select Shut down.) 14. Click the file on the top of screen and find the Reprint report. Click it to print out the report manually. 15. Allow the machine to cool down below 100 degF [38 degC]. Release the pressure and close the water line. 16. Disassemble the rotor cup and bob gently and clean them up using the recommended cleaner. 17. Turn on the nitrogen to 10 to 20 psi (69 to 138 kPa) to get all excess water or gel residue out of the expansion fitting. 18. Spray some WD40 on the shaft to lubricate the bearing. Use a paper towel to wipe the moisture and gel off the shaft very gently (do not press against the shaft). Clean everything used and cover the oil bath. 19. Turn off the machine and release the pressure in the main nitrogen line.

5.7

Fracturing Sand Sieve Analysis The sand used as a proppant must be analyzed for size of the grains. You will use a series of sieves that are stacked in a specified order; refer to Figure 5-3.



5-23


5-23

Figure 5-3: ASTM Standard Sieves and Sieve Shaker

5.7.1

Sampling Techniques A proper sampling ensures that a representative sample of the fracturing sand is obtained for quality control testing. • Delivery samples – Nine samples per railroad car and three samples per truck load are needed, and five samples per 100,000 lbm (45,359 kg) when on location. – When the proper number of samples are obtained, combine the samples for one test. • Conveyor belt samples – Sand falling from a conveyor belt into a truck or railcar should be allowed to flow for at least 2 minutes before catching sample; wait 2 minutes after the start of each compartment when catching location samples.



5-24


5-24

– Place the sampling device in the stream of sand with its longitudinal axis perpendicular to the flowing sand. Move the sampling box at a uniform rate from side to side in the sand stream. Several samples should be extracted at uniform intervals through the body of sand and combined for a representative sample. • Alternate sampling method (non-API) If a flowing sample is not possible or desired, then a grain thief may be used to obtain a sample. It is recommended to catch at least three samples whenever possible and combine them for testing.

5.7.2

Sand Sieve Analysis (Modified API Method) This method has been modified to meet specific criteria requested by clients. This method exceeds the API recommended practice for sand sieve analysis. 1. Refer to ISO 13503-2 (Petroleum and natural gas industries – Completion fluids and materials – Part 2: Measurement of properties of proppants used in hydraulic fracturing and gravel-packing operations) or Table 5-3 to determine the recommended sieve sizes used in testing designated sand sizes. Table 5-3: Recommended Sieve Sizes for Fracturing Sands Fracturing Sand Size Designations USA Sieves Recommended 6/12

8/16

12/20

16/30

20/40

30/50

40/70

70/140

4

6

8

12

16

20

30

50

6

8

12

16

20

30

40

70

8

12

16

20

30

40

50

100

10

14

18

25

35

45

60

120

12

16

20

30

40

50

70

140

16

20

30

40

50

70

100

200

Pan

Pan

Pan

Pan

Pan

Pan

Pan

Pan

2. Establish an accurate weight (WT) of the 100 g split sample to within 0.1 g. 3. Make sure that all sieves are completely cleaned with the manufacturer-recommended brush. Weigh each sieve accurately and record the weights. 4. Stack the sieves in order of increasing mesh size from bottom to top, with the pan on the bottom.



5-25


5-25

5. Pour the sample onto the top sieve and place the sieve set plus the pan in the test sieve shaker. Cover the sieves and tighten the sieve set. 6. Power on the sieve shaker for 10 minutes. 7. Remove each sieve and weigh each sieve separately with its contents. Weigh the pan as well.

Note Remember to brush off the particles from the bottom of each sieve into the next size sieve before weighing either. 8. Calculate the percent by weight of the total sand sample retained on each sieve and the pan. To calculate the percentage by weight of the sand falling within the designated sieve sizes, use these equations: • weight of the retained sand (WR) = sieve weight after shaking – sieve weight before shaking • wt % of the total sand sample retained on each sieve = WR/WT x 100. 9. For fracturing proppants, a minimum of 90 wt % of the tested proppant sample (96.0% for gravel packing) shall be pass the coarse designed sieve and be retained on the fine designated sieve. Not over 0.1% of the total tested proppant sample shall be larger than the first sieve size in the nest specified in Table 5-3 and not over 1.0% of the total tested proppant sample shall be smaller than the last designated sieve size. Note The cumulative weight should be within 0.5% of the sample weight used in the test; if not, the sieve analysis must be repeated using a different sample. 5.8

Proppant Turbidity Test The turbidity test is performed to determine the cleanliness of the fracture sand (amount of fines present). You will need the following equipment and materials to perform the proppant turbidity test: • sand sample • distilled or DI water • glass medicine bottle graduated to 100 mL with cap • black felt tip permanent marker Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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5-26

• small funnel to pour sand into medicine bottle. To perform the proppant turbidity test: 1. Mark the flat side of the bottle with an X using the black felt tip marker. 2. Fill the bottle to the 20-mL mark with sand. 3. Add distilled water to the 100-mL mark and secure cap. 4. Shake the bottle vigorously for 20 seconds. 5. In a well-lit area, hold the bottle at arms’ length with the flat side away from you. If the X can be seen clearly, the sand passes the turbidity test. If the X is barely distinguishable or cannot be seen, the sand fails the test.

Note After the turbidity test is complete, check the pH of the sample; if the pH is above 6.0, the sand will be acceptable for YF*100 and YF200 series fluids. 5.9

Silt Turbidity Test Turbidity in water is the result of suspended clay, silt, or finely divided inorganic matter being present. The HACH DR/2000 spectrometer measures the optical property of the suspension, providing a turbidity value for the tested proppant sample. The turbidity of the tested proppant sample should be 250 (FTU) formazine turbidity units or less. You will need the following items to perform the silt turbidity test: • HACH DR/2000-type spectrometer • sample vials • 6-oz or larger, plastic-capped, wide-mouth bottle • syringe/pipette • DI water • proppant sample. To perform the silt turbidity test: 1. Measure 20 mL of dry proppant sample and 100 mL of DI water in a 6-oz wide-mouth bottle, mix well, and allow to stand for 30 minutes. 2. Shake the bottle vigorously by hand for 45 to 60 shakes in 30 seconds. Allow it to stand for 5 minutes.



5-27


5-27

3. Switch on the spectrometer. 4. Dial the method number 750 and set the wavelength to 450 nm. 5. Zero the FTU using DI water in the test vial. 6. Using a syringe or pipette, extract 25 mL of water-silt suspension from near the center of the water volume. 7. Place the water-silt suspension in the test vial. 8. Determine the sample turbidity in FTU and record.

5.10

Proppant Sphericity and Roundness Test Particle sphericity is a measurement of how closely a sand particle or grain approaches the shape of a sphere. Grain roundness is a measure of the relative sharpness of grain corners, or of grain curvature. Figure 5-4 illustrates these concepts. The test method is specified by ISO 13503-2 (Krumbein and Sloss visual estimation method).

Figure 5-4: Sphericity Versus Roundness

You will need the following equipment to test for sphericity and roundness:



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5-28

• optical microscope Heerbrugg, Model Wild M3 or scanning electron microscope (SEM), Phillips, Model XL30 • sample sticker/platform • proppant sample. To test for sphericity and roundness: 1. Stick 20 or more grains of proppant on the glass plate platform for electronic scanning electron microscope (ESEM). 2. Switch on the optical microscope. Refer to the SEM analysis for ESEM startup procedures. 3. Adjust the magnification until a clear picture of proppant particles appears. 4. Compare the shape of the particles visually with the standard chart (refer to ISO 13503-2) and determine the sphericity and roundness of each particle. 5. Record the average of the above reading as the sphericity of the proppant sample.

5.11

Fluid Compatibility with Resin-Coated Proppants (RCP) Test Laboratory testing is performed to determine the compatibility of RCP with fracturing fluids. You will need the following items to test the fluid's compatibility with the RCP: • pH meter • water bath • Waring blender • linear gel sample • all additives • RCP sample • fluid not exposed to RCP. To test the fluid’s compatibility with the RCP: 1. Prepare 500 mL of linear gel plus all additives except crosslinker. The crosslinker is not added for zirconate crosslinked fluids to prevent shear degradation during compatibility test.



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5-29

2. Measure pH using the pH meter. 3. Add 10 ppa (lbm of proppant added) of RCP, and mix for 30 seconds at a mixer speed that creates a vortex without significantly entraining air. 4. Place the mixture in a water bath at 150 degF [66 degC] for 30 minutes. 5. After 30 minutes, remove the mixture from the bath and mix for 30 seconds more. Stop blender and allow proppant to settle to bottom of container. Note Allow fluid to cool before continuing. 6. Transfer 250 mL of fluid (without proppant) into a clean blender. 7. Measure pH using the pH meter. 8. Add crosslinker and perform the benchtop and rheology tests described here, or use the Fracturing Materials Manual. Follow the relevant quality control standard procedures. 9. Compare fluid properties and rheology profile with that of a fluid not exposed to RCP. Viscosities measured on a Fann 50-type rheometer should be similar for fluids prepared with and without RCP exposure (typically within 100 cP (100 mPa·s) for same test conditions). 10. If a loss in viscosity is observed, fluid performance may be improved by increasing the crosslinker concentration. However, if significant loss in viscosity is observed—the fluid is not stable and looks broken—then that fluid is not compatible with that RCP.

5.12

Vapor Pressure Test The Reid method is used to determine the vapor pressure of petroleum products. This method offers the type of data commonly requested for the field.

Note Warning: Keep heat and ignition sources away from the test. You will need the following items to perform the vapor pressure test: • sample to be tested



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5-30

Note Sample should be handled carefully to minimize vapor loss. • water bath, adjustable from 100 to 140 degF [38 to 60 degC] • For details on the Reid vapor pressure tester, refer to ASTM232-82. To perform the vapor pressure test: 1. Unscrew the testing chamber at its midsection and inspect the O-ring seal. 2. Transfer 25 to 30 mL of sample to the bottom half of the testing chamber and then quickly screw the upper and lower halves together. 3. Immerse the apparatus into the water bath and start heating. Heat bath slowly so that the sample temperature remains close to the bath temperature. 4. Using the Reid vapor pressure tester, record the vapor pressure of the sample when the temperature is 100 degF [38 degC]. Note the exact temperature and pressure when taking a reading. Be sure to shake the test chamber vigorously before each reading to ensure that the validity of the sample has been maximized. 5. Continue heating and record the vapor pressure when the bath temperature reaches 130 degF [54 degC]. Note the exact temperature and pressure at the time of the reading. 6. Discard the sample and thoroughly wash the apparatus with water. 7. To find the vapor pressure, plot pressure versus temperature of the data collected. Extrapolate to obtain the exact pressure at 100 and 130 degF [38 and 54 degC] for reporting.



6-i

JET Manual 38 / Hydraulic Fracturing Fluids

6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.8.1 6.8.2 6.9 6.10 6.11

6-i

Hydraulic Fracturing Fluids Preparing Linear Gel Fluids ____________________________________ Preparing YF100HTD Fluids ____________________________________ Preparing YF100FlexD Fluids ___________________________________ Preparing YF800HT Fluids ______________________________________ Preparing YF100LG Fluids _____________________________________ Preparing YF100LGD Fluids ___________________________________ Determining Crosslink Delay Time ____________________________ Preparing ThermaFRAC Fluids ________________________________ Determining Crosslinking and Delay Times ___________________ Determining RCP/ThermaFRAC Fluids Compatibility __________ Preparing YF GO V Fluids _____________________________________ Preparing SuperX Emulsion (SXE) _____________________________ Preparing ClearFRAC XT Fluids _______________________________


6-1 6-2 6-4 6-6 6-8 6-10 6-12 6-12 6-14 6-14 6-15 6-17 6-18


6-1


6

6-1

Hydraulic Fracturing Fluids PPCG, WS, SFE, JET Manual 38

These hydraulic fluids are the fluids that the engineer designs for a particular job. They must be tested in the laboratory before pumping the job. These procedures explain how to prepare the fluids.

6.1

Preparing Linear Gel Fluids The linear gel (Figure 6-1) can be prepared for all water-base fluids in this way.

Figure 6-1: Sample Linear Gel

To prepare the linear gel, follow this generic procedure. 1. Measure 500 mL of deionized (or field) water into a 1-L Waring blender cup. 2. Add either 167 lbm/1,000 galUS (20 kg/m3) KCl or 2 galUS/1,000 galUS (2 L/m3) L064. You may need to stir until well mixed, depending on the specific fracture fluid. 3. Adjust the fluid pH if necessary, as per the manual guidelines for your specific fluid.



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6-2

4. Add the required amount of polymer to the blender, running at a speed to create a vortex down to the blades. 5. Continue to stir at lower rate to prevent inclusion of air bubbles in the gel. Allow some time for the gel to hydrate. 6. Measure viscosity at 100 rpm on a Fann® 35 with R1-B1 at 80 degF [27 degC].

6.2

Preparing YF100HTD Fluids The WideFRAC 100HTD (YF*100HTD) fracturing fluids are water-base systems comprising a refined guar gelling agent crosslinked by a borate-type crosslinker. These fluids are designed for batch- or continuous-mix operations. YF100HTD fluids can be used at temperatures ranging from 125 to 325 degF [52 to 163 degC]. To prepare YF100HTD, you will need the following items: • Waring blender equipped with variable transformer • blender jar • graduated cylinder and syringes • timer • magnetic stirrer • 1L-glass bottle • pH meter • thermometer • Fann® 35-type viscometer. You will also need the proper additives. The additives in a typical YF140HTD system can include the following (concentration amount for 500 mL): • M117 Potassium Chloride: 167 lbm/1,000 galUS (10 g) • M275 Microbiocide: 0.45 lbm/1,000 galUS (0.027 g) • J353 High-Temperature Gel Stabilizer: 10 lbm/1,000 galUS (0.6 g) • EZEFLO* F103 Surfactant: 1 galUS/1,000 galUS (0.5 mL) • J424 Water Gelling Agent: 40 lbm/1,000 galUS (2.4 g) • L10 Crosslinker: 7.5 lbm/1,000 galUS (0.45 g) • M2 Caustic Soda (activator): 15 lbm/1,000 galUS (0.9 g) Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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6-3

• J450 Stabilizer: 1 galUS/1,000 galUS (0.5 mL) • J480 YF100HTD Crosslinker Delay Agent in concentration to be determined • EB-Clean* J490 HT Encapsulated Breaker in concentration to be determined. Prepare the YF100HTD according to the following procedure. 1. Prepare linear gel: Pour 490 mL of water into the mixing cup. Stir with low speed. 2. Add 10 g of KCl and 0.027 g of M275 into the mixing cup. 3. Add 2.4 g of J424 slowly into the cup and control the stir rate to allow the polymer to disperse. 4. Increase the stir rate after the polymer disperses to hydrate faster. Hydrate the gel for 30 to 60 minutes. 5. While the gel is hydrating, weigh 0.6 g of J353 and dissolve it in a small amount of water. 6. Check the fluid temperature and pH of the gel. The pH should be 6 to 8. 7. Check the fluid viscosity to see if it is in the range specified in the Fracturing Materials Manual specification. Refer to the Fann 35 test procedures in Section 5.2: Linear Fluid Viscosity. 8. Prepare the crosslinker: Put 3.7 mL of water into a glass bottle. Stir using magnetic stirrer. 9. Weigh 0.9 g of M002 and add slowly into the bottle while stirring.

Note Warning: There is a significant risk of boiling the water as the reaction is exothermic, when adding M002 at the concentration more than 2 lbm per gallon of water. Using U028 (the liquid form of caustic) is preferable whenever possible as it eliminates the risk of boiling the water. 10. Measure 0.45 g of L010 and add it into the bottle while stirring. 11. Add the required amount of J480 slowly while stirring, until dissolved. 12. Place 0.5 mL of J450 into the bottle. 13. Age the crosslinker solution for 60 minutes. 14. Crosslink the gel Adjust the stirring speed to create a vortex to the tip of the stirrer. Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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6-4

15. Add J353 solution and 0.5 mL of F103 into the mixing cup and mix 1 minute. 16. Add the prepared crosslinker into the linear gel and start timing. 17. Record the time to reach the vortex closure as the vortex closure time. 18. Check the time until hang-lip happens and record this time as the hang-lip time. 19. Check the pH of the crosslinked gel and record.

Figure 6-2: Sample Crosslinked Gel

6.3

Preparing YF100FlexD Fluids The WideFRAC 100FlexD (YF100FlexD) fracturing fluids are water-base systems comprising a refined guar gelling agent crosslinked by a borate-type crosslinker. These fluids are designed for batch- or continuous-mix operations. YF100FlexD fluids can be used at temperatures ranging from 175 to 275 degF [79 to 135 degC]. To prepare YF100FlexD fluid, you will need the following equipment and materials: • Waring blender equipped with variable transformer • blender jar • graduated cylinder and syringes • timer Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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6-5

• magnetic stirrer • 1L-glass bottle • pH meter • thermometer • Fann 35-type viscometer. The following additives are often used in a typical YF100FlexD fluid (concentration amount for 500 mL). Check that these or any others indicated are in stock. • M117 Potassium Chloride: 167 lbm/1,000 galUS (10 g) • M275 Microbiocide: 0.45 lbm/1,000 galUS (0.027 g) • J353 High-Temperature Gel Stabilizer: 10 lbm/1,000 galUS (0.6 g) • J580 Water Gelling Agent: 40 lbm/1,000 galUS (2.4 g) • U028 Activator: 2 galUS/1,000 galUS (1 mL) • J604 Crosslinker: 3 galUS/1,000 galUS (1.5 mL) Follow this procedure to prepare the YF845HT. Prepare the linear gel: 1. Pour 490 mL of water into the mixing cup. Stir with the Waring blender on low speed. 2. Leaving the blender on, add 10 g of KCl and 0.027 g of M275 into the mixing cup. 3. Add 2.4 g of J424 slowly into the cup and control the stir rate to allow the polymer to disperse. 4. Increase the stir rate after the polymer disperses to obtain a faster hydration and hydrate the gel for 10 to 20 minutes. 5. While the gel is hydrating, weigh 0.6 g of J353 and dissolve in approximately 2 mL of water. 6. Check the fluid temperature and pH of the gel. The pH should be 6 to 8. 7. Check the fluid viscosity to ensure it is in the specified range as given in Section 2.5: Appendix A: Viscosity of various WaterFRAC fluids in section 1.1 - WaterFRAC 100 (WF100) Fracturing Fluids in the FMM Volume I: Water-Based Fluids Section 1 – Linear Fluid Systems manual, InTouch content 5769214.



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6-6

8. After the gel hydrates to meet the specification, add the J353 solution and then 0.5 mL of F103 surfactant into the linear gel, in that order. Stir the gel for approximately 2 minutes, and then check the pH again. Prepare the delay agent solution: Add 0.9 g of J511 in the beaker and top-up with approximately 10 mL of distilled water. Crosslink the gel: 1. Adjust the stirring speed to create a vortex so as to see the blade nut and add the J511 solution to the base gel. 2. Add 1 mL of U028 activator. 3. Check pH of base gel. The pH should be between 11 and 12. Note High bicarbonate water will tend to buffer the final pH lower, so the pH rise upon adding U028 will be slightly less. 4. Lastly Add 1.5 mL of J604 crosslinker into the linear gel and start the timer. 5. Record the time to reach the vortex closure as the vortex closure time. 6. Check the time until hang-lip happens and record this time as the hang-lip time. 7. Stop blender after 5 minutes if no vortex closure is observed. 8. Check the pH of the crosslinked gel and record.

6.4

Preparing YF800HT Fluids YF800HT fluids are temperature-activated, zirconate-crosslinked, water-base fluids that use carboxymethylhydroxypropyl guar (CMHPG) as a gelling agent. Crosslinker J515 is used to crosslink the fluids. There are two fluid designs: • YF800LPH (pH 4 to 5) for temperatures from 100 to 250 degF [38 to 121 degC] • YF800HT (pH 9 to 9.5) for temperatures from 275 to 350 degF [135 to 177 degC]. To prepare YF800HT, you will need the following equipment and materials: • Waring blender equipped with variable transformer Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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6-7

• jar • graduated cylinder and syringes • pH meter • thermometer • Fann 35-type viscometer. The following additives are often used in a typical YF845HT (concentration amount for 500 mL). Check that these or any others indicated are in stock. • M117 Potassium Chloride: 167 lbm/1,000 galUS (10 g) • M275 Microbiocide: 0.45 lbm/1,000 galUS (0.027 g) • J353 High-Temperature Gel Stabilizer: 10 lbm/1,000 galUS (0.6 g) • EZEFLO F103 Surfactant: 1 galUS/1,000 galUS (0.5 mL) • J916 CMHPG Slurry: 10.1 galUS/1,000 gaUS (5.05 mL) • L401 Stabilizing Agent: Used to adjust to pH 6.5 to 7.0 • J464 Buffering Agent: 10 lbm/1,000 gaUS: (0.6 g) • M002 (2% caustic soda solution as activator): 10 galUS/1,000 gaUS (5 mL) • J450 Stabilizer: 1 galUS/1,000 gaUS (0.5 mL) • J515 Crosslinker: 0.7 galUS/1,000 gaUS (0.35 mL) Follow this procedure to prepare the YF845HT. 1. Pour 490 mL of water into the mixing cup. Stir with the Waring blender on low speed. 2. Leaving the blender on, add 10 g of KCl and 0.027 g of M275 into the mixing cup. 3. Measure 5.05 mL of polymer slurry (J916) and add slowly into the cup. Control the stir rate to allow the polymer to disperse. 4. Add L401 while checking the pH of the fluid until the pH is 7.0. Record the pH. 5. Increase the stir rate to obtain faster hydration and hydrate for 30 minutes. 6. Check the fluid viscosity to ensure it is in the specified range. Record the linear viscosity against Fracturing Materials Manual specification, the pH (6.9 to 7.1), and the temperature. 7. While the gel is hydrating, weigh 0.6 g of J353 and 0.6 g of J464. Dissolve each using approximately 2 mL of water, in separate containers.



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6-8

Note The J464 solution will be used later in this procedure. 8. After the gel hydrates to meet the specification, add the J353 solution and then 0.5 mL of F103 surfactant into the linear gel, in that order. Stir the gel for approximately 2 minutes, and then check the pH again. 9. Crosslink the gel: Heat the water bath to approximately 194 degF [90 degC] or use a microwave oven (the recommended practice) for homogeneous heating. 10. Add J464 solution, M002 (2%), 0.5 mL of J450, and 0.35 mL of J515 into the linear gel. Check the pH after adding each component. 11. Continue to mix the fluid at a vortex to the tip of the stirrer for 30 seconds after adding the J515. Check the fluid pH. 12. Split the prepared mixture into two equal parts of approximately 250 mL. You will use one part to perform the crosslinking test and the other part to perform the Fann 50 test. 13. Begin the Fann 50 test as soon as possible after mixing the fluid in Step 11. The time between the end of the fluid mixing and beginning the Fann 50 test should not be more than 5 minutes. 14. To perform the crosslinking test, place the beaker containing 250 mL of prepared gel into the water bath or microwave. 15. Shake the fluid frequently to avoid a temperature gradient from the wall of the beaker to the center of the fluid. Check the crosslink every 15 to 30 seconds (adjust the time more frequently while using the microwave; especially when close to the desired temperature) while testing the fluid temperature by thermometer. Record the fluid temperature when there is a noticeable resistance to the thermometer moving into/out of the fluid.

6.5

Preparing YF100LG Fluids The WideFRAC 100LG (YF100LG) fracturing fluids are water-base systems comprising a refined guar gelling agent crosslinked by a borate crosslinker. They are prepared from the WaterFRAC 100 (WF100) fluids. YF100LG fluids are designed to crosslink quickly. The vortex closure of these fluids is 5 to 10 seconds, which allows uniform mixing of all components before becoming viscous. The crosslink is fairly mature in another 10 to 20 seconds. You will need the following equipment and materials to prepare the YF100LG solution:



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6-9

• Waring blender • blender cup • graduated cylinders • disposable syringes • pH meter or paper • Water Gelling Agent J424 or Guar Polymer Slurry J877. 1. Prepare YF100LG solution: Add Crosslinker L10 at 1.2 to 2.2 lbm/1,000 galUS of WF100 fluid (0.144 to 0.264 g L010/L) depending on the temperature. For adding small quantities, a stock solution of L010 can be prepared by mixing 2.3965 g of L010 to 100 mL of distilled water; 1 mL of L010 stock solution per 200 mL of WF100 = 1 lbm L010/1,000 galUS WF100. 2. Prepare crosslinker activator solution: The pH stabilizer (activator solution) for fracturing temperatures less than 175 degF [79 degC] contains J494 at 12 lbm/1,000 galUS (1.4 kg/m3) of YF fluid and M003 at 5 lbm/1,000 galUS (0.6 kg/m3) of YF fluid. This is called a 12-5 solution. The preferred way to add the J494 and M003 to the fluid is to prepare a 14 to 20% (wt/wt) aqueous solution and meter it in the blender. To prepare a 16% (wt/wt) 12-5 solution, first place 19 mL of deionized water in a small glass beaker on a magnetic stirrer. 3. Slowly add 2.55 g of J494 to the vortex. 4. Slowly add 1.06 g of M003 to the vortex. Continue mixing for 15 to 20 minutes until the solids dissolve. The specific gravity of a 16% (wt/wt) solution at 75 degF [24 degC] is 1.131 g/cm3. An addition rate of 11.3 mL/1,000 mL of linear gel is equivalent to 12 lbm J494 and 5 lbm M003/1,000 galUS of fluid. 5. Prepare breaker solution: A stock solution of J218 can be prepared by adding 2.3965 g of J218 to 100 mL of distilled water. Then, 1 mL J218 stock solution per 200 mL of WF100 = 1 lbm J218/ 1,000 galUS WF100. 6. Prepare 500 mL of WF100 base gel. 7. Add L010 to the base gel and mix at low speed for 1 minute, checking to ensure that air is not trapped in the gel. 8. If J218 breaker is required, add the required amount to the vortex and mix for 1 minute. 9. Set the mixer speed to 1,900 to 2,000 rpm and add 5.65 mL of the J494:M003 activator solution to the vortex. A vortex closure of 10 to 15 seconds should be observed. 10. After 30 seconds, stop the mixer and transfer the fluid to a beaker. The fluid should be fully crosslinked.



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6-10

11. Check the pH of the crosslinked fluid. It should be 9.6 to 9.9 at ambient temperature. If it is not, you may have contaminated additives and will need to repeat the test with fresh additives.

6.6

Preparing YF100LGD Fluids WideFRAC 100LGD (YF100LGD) fracturing fluids are water-base systems containing a refined guar gelling agent (20 to 50 lbm/1,000 galUS (2.4 to 6.0 kg/m3)) crosslinked with a borate crosslinker. YF100LGD fluids can be batch mixed or continuous mixed. YF100LGD fluids are prepared from any of the WaterFRAC 100 (WF100) fluids. Addition of crosslinker, activators and a delay agent converts the WF100 fluid to the corresponding YF100LGD fluid. To prepare the YF100LGD solution, you need the following equipment and materials: • Waring blender • blender cup • graduated cylinders • disposable syringes • pH meter or paper • Water Gelling Agent J424 or Guar Polymer Slurry J877. 1. Prepare crosslinker: Mix the crosslinker solution according to the specific requirements. The crosslinker solution is made up of the following (values are for 1,000 mL): • water (4.5 to 7 galUS/1,000 galUS) • L010 at 5.5 to 9.0 lbm/1,000 galUS WF100 fluid: (0.659 to 1.078 g L010/L) depending on temperature • activator M002: (10 to 20 lbm/1,000 galUS (1.12 to 2.24 g) or U028 • Stabilizer J450: typically 1 galUS/1,000 galUS (if required) (1 mL) • L010: 7 lbm/1,000 galUS (0.84 g) • M002: 16.5 lbm/1,000 galUS (1.98 g). This example solution (before the J450 is added) has a specific gravity of 1.304 at 24 degC [−4 degC] and therefore will have an addition rate of 7.8 galUS/1,000 galUS (or 7.8 mL/1,000 mL), calculated as follows: Crosslinker rate = (weight of crosslinker solution/1,000 galUS)/(8.34 x SG) = [(6 x 8.34) + 7 + 16.5]/(1.304 x 8.34) = 6.8 galUS/1,000 galUS with 1 galUS/1,000 J450 Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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6-11

= 7.8 galUS/1,000 galUS (1.56 mL/200 mL)

Potential Severity: Serious Potential Loss: Personnel Hazard Category: Temperature

M002 must not be mixed at the concentration higher than 2 lbm per gallon of water as there is a significant risk of boiling the water at these concentrations. Using U028 (the liquid form of caustic) is preferable whenever possible as it eliminates this risk. 2. Mix crosslinker delay solution:The concentration of the delay agent J511 depends on the polymer concentration, mix water temperature, and the desired crosslink time. The minimum J511 concentration required to prevent syneresis (overcrosslinking) at room temperature for approximately 12 hours is 10 lbm/1,000 galUS (1.2 kg/m3). J511 is readily soluble in water. The addition of NaOH at about 1 lbm/1,000 galUS (0.12 kg/m3) prevents bacteria from deteriorating the J511 solution (resulting in ~pH 10). Aqueous solutions with 30 to 70% J511 present can be employed. To prepare a 30% solution containing 2.79 lbm/galUS (0.33 kg/m3) J511, add 0.02 g of J511 to 70 mL of water and mix until it is dissolved. 3. Add 30 g of J511 and continue mixing until all solids dissolve. Table 6-1 can be used as a guideline for adding various quantities of J511. Table 6-1: Quantities of J511 in YF100 LGD Desired Concentration J511, lbm/1,000 galUS

Equivalent to galUS of 30% J511/1,000 galUS of WF100

Equivalent to mL of 30% J511/200 mL of WF100

10

3.6

0.72

15

5.4

1.08

20

7.2

1.44

25

8.9

1.78

30

10.7

2.14

4. Prepare breaker solution: Prepare a breaker solution by adding 2.3965 g of J218 or J481 to 100 mL of distilled water. 1 mL J218 or J481 stock solution per 200 mL of WF100 = 1 lbm J218 or J481/1,000 galUS WF100.



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6.7

6-12

Determining Crosslink Delay Time To determine the crosslink delay time with various concentrations of J511 present: 1. Place 200 mL of the prepared WF100 fluid into a Waring blender jar and record the fluid temperature. 2. Start mixing at 2,000 rpm; this speed should produce a vortex. 3. Inject the delay agent and mix for 2 minutes. 4. Inject the crosslinker solution and start the stopwatch simultaneously. 5. Vortex closure is defined by the crosslinked gel covering the blade nut. Record the time elapsed between injecting the crosslinker solution and vortex closure. 6. Stop the blender and pour the gel into a 250-mL beaker. Start the stopwatch. 7. Pour the fluid from one 250-mL cup to another until 80% crosslink is achieved. The 80% crosslink is defined by the floppy gel easily retracting into the cup and showing no adhesion to the wall of the cup when the gel is poured. Also, notice if the crosslinked gel can be fractured during the floppy test. Record the time elapsed from vortex closure to 80% crosslinking. 8. Continue pouring the crosslinked gel from cup to cup every 15 seconds until 100% crosslinking is achieved. The 100% crosslink is defined as when the crosslink gel is poured from cup to cup, the fluid comes out in one solid mass with minimal elongation.

6.8

Preparing ThermaFRAC Fluids The ThermaFRAC* fluids were designed to reduce operational complexity as compared to previous high-temperature fluids. Further, the crosslinker component is designed with both an early (low temperature) crosslink and a secondary, zirconium-based crosslink that activates at a higher temperature, typically after the fluid has exited the perforations. The early crosslink occurs on a slightly delayed basis, with viscosification to a lipping condition occurring over approximately 3 minutes at ambient temperatures. The secondary crosslink occurs typically between 125 and 135 degF [52 and 57 degC]. This approach develops early viscosity while protecting the polymer from irreversible shear damage when transiting the tubulars, which will allow a more viscous final gel when the secondary crosslinker activates.



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6-13

You will need the following equipment and materials to prepare ThermaFRAC fluids: • Waring blender equipped with variable transformer • blender jar • graduated cylinder and syringes • pH meter • thermometer • Fann 35 • microwave • titrator • 0.1N HCl • methyl orange indicator • phenolphthalein indicator • DI water • Orion Model 130A conductivity meter • fluid additives and resin-coated proppant (RCP). To prepare ThermaFRAC fluids: 1. Check the pH of the water. It should be 6 to 8; adjust by HCl or NaOH if not in this range. 2. Pour a small amount of water into the mixing cup. Stir with low speed. Add D175 if required. 3. Add required J598 into the mixing cup. 4. Measure the polymer slurry and add it slowly into the mixing cup. Control the stir rate to allow the polymer to disperse. 5. Increase the stir rate to hydrate the gel faster, and hydrate for about 10 to 15 minutes. Check the pH of the fluid while adding J488 until the fluid pH is less than 7.0; record the pH and the amount of J488 needed to reach this pH. 6. To ensure complete hydration, the viscosity of the base gel is measured using a Fann 35 rheometer (or equivalent) with a R1 rotor and B1 bob combination and a spring factor of 0.2. The apparent viscosity at 511 s-1 (300 rpm) is compared with the recommended viscosity values in the hydration chart in the Fracturing Materials Manual. 7. Continue mixing for another 5 minutes until the viscosity meets the specification.



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6.8.1

6-14

Determining Crosslinking and Delay Times To determine the crosslink delay time with ThermaFRAC fluids: 1. Fill blender with 250 mL of the prepared linear gel; shear at low speed. 2. Add J596 solution, and J599 solution, and M002 into the linear gel. Check the pH after adding each component. 3. Continue to mix the fluid at a vortex (to the tip of stirrer) for 20 to 30 seconds. 4. Check and record the fluid pH. 5. Split the prepared mixture into two equal parts. You will use one part to perform the crosslinking test and the other part to perform the Fann 50 test. 6. Start the Fann 50 test as soon as possible after mixing the fluid. The time between the end of mixing the fluid and beginning the Fann 50 test should not be more than 5 minutes. 7. To perform the crosslinking test, place a beaker containing 150 mL of prepared gel into the microwave oven. 8. Check the crosslinking every 5 to 10 seconds while testing the fluid temperature by thermometer. 9. Write down the fluid temperature when there is a noticeable resistance to the thermometer moving into/out of the fluid (100% crosslinked). This temperature should be less than 120 degF [49 degC] for better fluid stability.

Note J599 functions as both a high pH buffer and high-temperature stabilizer, reducing the number of additives required. Until late in the treatment, J599 is used alone when clay stabilizer M117 is used, or in conjunction with M002 when J598 is used. 6.8.2

Determining RCP/ThermaFRAC Fluids Compatibility To determine the compatibility between the ThermaFRAC fluid and the RCP: 1. Fill the blender cup with 250 mL of the prepared linear ThermaFRAC gel. 2. Add the required amount of J599 solution and M002 and mix at low speed. 3. Add 1 ppa (lbm proppant added) RCP to the blender; increase mixing speed for deep vortex to shear for 2 to 3 minutes. 4. Add J596 solution into the blender in the last few seconds during shearing. 5. Let the mixture settle for about 2 minutes. Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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6-15

6. Mix at 1,500 rpm for 3 to 5 minutes. 7. Decant the clear part of the mixture. Check the pH to make sure it is in the range of 9.2 to 9.5. If it is not, adjust with J599 or M002 to meet the pH requirement and record the amount of J599 added and the final pH. 8. Put approximately 150 mL of the gel into the beaker and place it into the microwave oven to determine the crosslink temperature according to the procedure in Section 6.8.1: Determining Crosslinking and Delay Times. Change the concentration of J464L and repeat the procedure if the crosslink temperature does not meet the specification of less than 120 degF [49 degC]. Otherwise, go to the next step. 9. Put approximately 35 mL of the fluid into a beaker and add the required breaker to perform the Fann 50 tests. 10. Increase the amount of proppant added for the FracCADE* design to check all loadings (for example, 2, 4, 6, 8, 10, and 12 ppa). Repeat Steps 1 through 9 to obtain a detailed relationship between the RCP loading and the gel crosslinking/gel stability.

6.9

Preparing YF GO V Fluids YF GO* V is a gelled, oil-base fluid used as a fracturing fluid for the treatment of water-sensitive formations. Diesel, kerosene, condensate, and a wide variety of crude oils can be used to prepare YF GO V. You will need the following equipment and materials to prepare the YF GO V: • disposable syringes • glass or plastic beakers • magnetic stirrer • balance • Waring blender • Fann 35 viscometer • graduated measuring cylinders • water bath • J518 oil gelling agent • C108 Activator • J474 breaker To prepare the YF GO V:



6-16


6-16

Note If J602 is to be used, mix 1.44 g of J602 solid in 10 mL of deionized water until it dissolves. This solution is equivalent to J602L. 1. Mix J602L and J601 at a ratio of 1:5 by volume. Place a small glass beaker on the magnetic stirrer and add the following additives: • J518: 9 mL • C108: 4 mL: Allow this solution to mix for at least 30 minutes. 2. Place 1 L of the base fluid, usually diesel, in a Waring Blender and start mixing at 2,000 rpm. Create a vortex down to the blades. The base fluid is diesel normally containing <0.5% water because the system is water sensitive. 3. Simultaneously add the desired quantity of J518 and the activator to the edge of the vortex. The quantities required to produce 7, 9, or 11 galUS of gel per 1,000 galUS of diesel (7, 9, or 11 mL/1,000 mL) are listed in Table 6-2. Table 6-2: J518 and Activator for YF GO V gel J518, mL/1,000 mL Diesel

Activator, mL/1,000 mL Diesel

7

3

9

4

11

4.5

4. Mix at 10,000 rpm for 10 minutes. 5. Transfer the gel to a Fann 35 cup and measure viscosity developed at 170 s-1 Adjustments to the gelling agent and activator concentrations to achieve the desired viscosity can be made knowing that: • increasing the activator concentration (with a constant gelling agent concentration) leads to quicker gelation but less viscosity stability with time at the upper end of the temperature range • increasing the gelling agent concentration (with a constant activator concentration) causes slower gel development but improved gel viscosity stability at higher temperatures.



6-17


6.10

6-17

Preparing SuperX Emulsion (SXE) SuperX* Emulsion (SXE*) is a viscous, highly retarded, concentrated acid system designed for use in matrix acidizing or acid fracturing of carbonate formations. SXE is an oil-external phase emulsion formed with a 70:30 hydrochloric acid-to-oil ratio, stabilized with an emulsifier. Hydrochloric acid (HCl) concentrations ranging from 15 to 28% may be used. SXE is designed for batch-mix operations; however, continuous-mix operations can be performed by following the procedures provided in the field mixing procedures section. The temperature range of SXE is 75 to 350 degF [23 to 177 degC] and emulsion breakout times can be customized by varying the emulsifying agent U108 loading as needed. U108 replaces both U080 (low temperature emulsifier for SXE) and U103 (high temperature emulsifier for SXE-HT).

Note Caution: Goggles, rubber gloves, and a protective covering, apron, face shield, must be worn when mixing acids. Always work under a fume hood when preparing acids.

Note Warning: Always add concentrated acid to water. Do not add water to the acid because the resulting heat could make the acid boil up onto your skin or eyes. You will need the following equipment and materials to prepare SXE: • 350-mL glass beakers • syringe • 15-mL glass tubes • magnetic stirrer • PMC hot-plate stirrer with speed adjustment • Fann 35 with Hastelloy bob/sleeve and fluid cup • kerosene or diesel • HCl, 7.5 to 28% • A262 Corrosion Inhibitor



6-18


6-18

• U108 Emulsifying Agent • glass rod • 2% KCl. To mix the SXE: 1. Add 140 mL of HCl into glass beaker and mix with the magnetic stirrer at a speed high enough to produce a vortex with the stirrer bar. Add the A262 corrosion inhibitor as required and mix until homogeneous. 2. Place another beaker on the mixing plate and place 60 mL each of kerosene and U108 into the beaker to mix thoroughly with a vortex tip to the bottom of the beaker. 3. Use a syringe to drop the acid and inhibitor mixture into the oil and U108 mixture while stirring with the tip of the vortex to the beaker bottom. 4. Increase the mixing speed as high as the mixer can mix, after adding all acid mixture into the oil mixture, for about 15 to 20 minutes. 5. A stable emulsion system should be prepared. Place a small sample of the emulsion into a 15-mL glass tube to observe for 10 minutes. No separation will be evident if the emulsion is an oil-external stable emulsion. Another way to check the oil-external property is to obtain a drop of emulsion using the glass rod and drop it into a 2% KCl solution in a 15-mL glass tube. If an oil-external emulsion forms, the drop will remain and slowly settle down to the tube bottom; otherwise, the drop will disperse quickly into the solution. Some commercial diesel is contaminated and not suitable for SXE preparation. If you are having difficulty forming a stable oil-external emulsion, change the source of the oil. 6. When you obtain a stable oil- external emulsion, check the rheology using the Fann 35 with the Hastelloy bob/sleeve combinations.

6.11

Preparing ClearFRAC XT Fluids ClearFRAC* fracturing fluids are water-base systems comprising a viscoelastic surfactant (J590), a rheology modifier J589 and a brine. Full fluid viscosity is achieved once the surfactant is completely dispersed in the brine. Viscosity develops rapidly without shear degradation. ClearFRAC fluids can be batch mixed or continuous mixed. Maximum fluid temperature is 265 degF [129 degC]. You will need the following equipment and materials to prepare a ClearFRAC solution:



6-19


6-19

• Waring blender equipped with variable transformer • blender jar • graduated cylinder and syringes • timer • pH meter • thermometer • Fann 35 • additives commonly used in ClearFRAC systems (example concentration amount in 500 mL): – M117 Potassium Chloride: 333 lbm/1,000 galUS (20 g) or L064: 2 galUS/1,000 galUS (1 mL). – J590 gelling agent: 30 galUS/1,000 galUS (15 mL). – J589: 5 lbm/1,000 galUS (0.3 g) To prepare a ClearFRAC solution: 1. Pour 500 mL of water into the blender jar and stir. 2. Test the fluid temperature. 3. Add 20 g of KCl and dissolve it. Then, add 0.3 g of J589 and dissolve it. 4. Create a vortex to the tip of the stirrer. Slowly add J590 into the mixture. The amount of J590 used will depend on the desired viscosity. 5. Stir the mixture until the vortex closes. 6. Place the mixture into the water bath at 70 to 80 degF [21 to 27 degC] to get the foam out. The fluid should become clear. Alternatively, the fluid can be centrifuged to remove entrained air. 7. Check the fluid temperature and pH. 8. Check the fluid viscosity to see if it is in the specified range.



7-i

JET Manual 38 / Preparing Matrix Acidizing Fluids

7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8

7-i

Preparing Matrix Acidizing Fluids Preparing Hydrochloric Acid (HCl) _____________________________ Mixing Intensified Acid _________________________________________ Mixing ClayACID _______________________________________________ Mixing Mud Acid _______________________________________________ Mixing Organic Mud Acid _______________________________________ Preparing Organic ClayACID ___________________________________ Preparing Alcoholic Acid _______________________________________ Mixing Dynamic Acid Dispersion (DAD) ________________________


7-1 7-2 7-3 7-5 7-7 7-8 7-9 7-9


7-1


7

7-1

Preparing Matrix Acidizing Fluids PPCG, WS, SFE, JET Manual 38

Matrix acidizing fluids are used in acidizing treatments. Table 7-1 shows the acidizing systems most used by Schlumberger. Table 7-1: Acid Systems Most used by Schlumberger Major Application

Acid Systems

Carbonate Acidizing

Hydrochloric acid

Sandstone Acidizing

Mud acid ClayACID* Organic mud acid Organic ClayACID

Gas Well

Alcoholic acid Gas well acid Gas well Mud acid

Retarded Acid

DAD* Acid SXE*

Gelled Acid

LCA* DGA*

BDA Mud Removal

MSR* NARS*

Organic Damage Removal

CLEAN SWEEP*

Scale Dissolving

CAS U104/U105/U106/U820/U821

Perforating Acid

Aqueous acetic acid Formic acid Perforating acid

Diverting Systems

SDA*, VDA*, OilSEEKER*, MaxCO3 Acid*

The following sections describe how to prepare laboratory samples of some of these acid systems.

7.1

Preparing Hydrochloric Acid (HCl) The maximum concentration of commercial HCl is 36%. Table 7-2 lists the hydrochloric acids most used in the oilfield industry. Use this table to prepare 1,000 mL of different dilutions of HCl from 36% HCl.



7-2


7-2

Table 7-2: Dilutions of Concentrated Hydrochloric acid HCI Acid Strength, %

36% HCl Needed, mL

Density, g/cc

28

751

1.141

20

507

1.099

15

379

1.074

10

247

1.049

7.5

183

1.036

5

120

1.024

To prepare 1,000 mL of any concentration of HCl: 1. Place approximately 200 mL of water in a 1,000-mL volumetric flask. 2. Add the required quantity of concentrated HCl (refer to Table 7-2) into the flask very slowly. Note Caution: Heat and odor will be released. It is strongly recommended that this procedure be performed in a fume hood.

Note Caution: Always remember to add acid to water. Never add water to acid. 3. Finish filling the flask to the graduated line indicating 1,000 mL. 4. Cap the flask and shake it a few times upside down over a sink or in the fume hood.

7.2

Mixing Intensified Acid Intensified acid is a regular inhibited HCl (generally 15%) with 33.8 lbm/1,000 galUS Y001 (0.25%) added.



7-3


7-3

Note Y001 is ammonium bifluoride, which combines with water to form HF acid. It is often used in initial cleanup as well as in dolomitic limestones containing a certain amount of silica. As much as 50% more reaction occurs between intensified acid and dolomitic limestone at surface conditions. The increase is less pronounced at elevated temperatures. Field results also confirm the value of intensified acid as a cleanup treatment in dolomitic limestone formations. A side reaction product of CaF2 precipitate could cause damage. You will need the following equipment and materials to mix intensified acid: • plastic beaker large enough to hold the acid, inhibitor, and Y001 Note No glass should be used. • magnetic stirrer • HCl base acid • required inhibitor • Y001 (33.8 lbm/1,000 galUS). To mix intensified acid: 1. Place the required amount of HCl base acid with the required amount of inhibitor into a plastic beaker. 2. Stir the solution until homogeneous with the magnetic stirrer. 3. Add the required amount of Y001 (33.8 lbm/1,000 galUS) slowly. 4. Stir the mixture until the solution becomes clear.

7.3

Mixing ClayACID ClayACIDs from Schlumberger are designed specifically for acidizing sensitive sandstone formations. They not only provide good stimulation, but also provide permanent stabilization of clays and other fines, eliminating water sensitivity and the mobility of migratory fines. ClayACIDs slowly release hydrofluoric acid (HF)



7-4


7-4

from the hydrolysis of fluoboric acid (HBF4) and can penetrate a much greater distance from the wellbore before spending than mud acid can. There are four formulations of ClayACID presented here: • Full-strength ClayACID • Full-strength ClayACID LT (low-temperature formulation) • Half-strength ClayACID • Half-strength ClayACID LT. ClayACIDs are the only acid formulations that require shut-in time. One reason is that they slowly release HF, limiting the amount of HF available at any one time. Another reason for shut-in time is the unique feature of borosilicate, a reaction product, to coalesce and form a coating on undissolved particles. This coating of borosilicate will cement the affected clays and fines in place, thus severely limiting further clay migration in the contact area. ClayACIDs are generally used from 130 to 300 degF [54 to 149 degC], but ClayACID LT is only used from 100 to 130 degF [38 to 54 degC]. You will need the following equipment and materials to mix ClayACIDs: • glass beaker • magnetic stirrer • DI water • Y001 • HCl. To mix a ClayACID, refer to Table 7-1 and Table 7-2 for additives and quantities. Each formulation prepares 1,000 mL of ClayACID.

Note To prepare ClayACID properly, the additives must be added in the order listed in the table (from top to bottom); otherwise, a precipitate will form.

Note Y006 and L010 have the same composition and can directly replace each other.



7-5


7-5

Table 7-3: Formulations for ClayACIDs Ingredients

Full-Strength ClayACID, H813 (SG 1.096)

Half-Strength ClayACID, H913 (SG 1.047)

Water, mL

680

843

Y001, g

120

60

35% HCI, mL

194

97

Y006, g

60

30

Table 7-4: Formulations for Low-Temperature ClayACIDs

7.4

Ingredients

Full-Strength ClayACID, H813 (SG 1.096)

Half-Strength ClayACID, H913 (SG 1.047)

Water, mL

545

772

Y001, g

120

60

35% HCI, mL

336

168

Y006, g

60

30

Specific Gravity (SG)

1.121

1.047

Mixing Mud Acid Mud acid is a mixture of inhibited HCl acid and hydrofluoric acid. Mud acid can not only dissolve the minerals that HCl acid can dissolve, but it can also dissolve siliceous minerals presented in most sandstone formations.

Note Calcium, magnesium, sodium, and potassium brines can react with HF acid to form insoluble precipitates. Do not use any of these for mixing the solution. You will need the following equipment and materials to mix mud acids: • plastic beaker • magnetic stirrer • water • Y001 • HCl. Table 7-5 lists the additives and quantities required to prepare some of the most common mud acid formulations.



7-6


7-6

Note Caution: Because of the safety issues associated with concentrated HF acid, it is strongly recommended to mix the mud acid with the quantities of Y001 inhibitor listed in Table 7-5. Table 7-5: Mud Acid Formulations Concentration

36% HCI, mL

Y001, g

Water, mL

Density, g/cc

4% HCI – 0.5% HF

110

7.2

885

1.022

6% HCI – 0.5% HF

160

7.2

835

1.032

8% HCI – 0.5% HF

210

7.2

785

1.041

8% HCI – 0.5% HF

210

7.2

785

1.041

8% HCI – 1% HF

220

15

770

1.045

10% HCI – 1% HF

270

15

720

1.054

6% HCI – 1.5% HF

180

24

804

1.041

7.5% HCI – 1.5% HF

220

24

764

1.048

10% HCI – 1.5% HF

290

24

694

1.061

12% HCI – 1.5% HF

340

24

644

1.070

10% HCI – 2% HF

300

30

680

1.065

12% HCI – 3% HF

380

48

588

1.085

To prepare mud acid according to Table 7-5:

Note Caution: Wear safety goggles, protective clothing, and rubber gloves. Work in a fume hood.



7-7


7-7

1. Place the appropriate quantity of freshwater in a plastic beaker.

Note Do not use seawater, oilfield brine, calcium, magnesium, potassium, or sodium chlorides to prepare mud acid. 2. Add the required amount of Y001. Mix using a magnetic stirrer until the Y001 has dissolved completely. 3. Add the required quantity of concentrated HCl slowly. Mix until clear.

Note Caution: Heat will be generated! Be sure always to add acid to the water—never add water to the acid. 7.5

Mixing Organic Mud Acid Organic mud acid is a mixture of 9% formic acid (HCO2H; also called L036) and 3% HF acid. It is more easily inhibited, has a lower reaction rate, and has less tendency to form asphaltic sludge than HCl acids. Organic mud acid is recommended for use in high-temperature matrix acidizing and wellbore damage removal in both sandstone and carbonate reservoirs where extended inhibition time is expected and asphaltic sludges are formed when the formation contacts HCl acids.

Note Warning: Both Y001 and L036 can cause severe eye and skin burns. Wear the proper PPE. You will need the following equipment and materials to mix 1,000 mL of an organic mud acids: • 1,000-mL plastic beaker • magnetic stirrer • freshwater



7-8


7-8

• A272 inhibitor as required • Y001: 48 g • 36% HCl: 72 mL • L036: 90 mL. Follow this procedure to mix organic mud acid. 1. Add approximately 500 mL of freshwater to the plastic beaker. Set magnetic stirrer to a speed high enough to form a vortex. 2. Add A272 and mix thoroughly. 3. Add the Y001 into the beaker slowly and stir until totally dissolved. 4. Add the HCl acid and L036. Stir until the mixture is homogenous. 5. Fill up the container to the 1,000-mL line with freshwater.

7.6

Preparing Organic ClayACID An organic ClayACID (OCA*) system is used for acidizing sandstones containing high silt/clay content and for HCl-sensitive formations. It reduces secondary precipitation and fines migration after the treatment. It can remove formation damage caused by clay and other aluminosilicate minerals, and it can be used for high temperature applications. Table 7-6 and Table 7-7 list two OCA formulations (OCA-R and OCA-HT) and the conditions under which they should be applied. Table 7-6: OCA Formulations Component

OCA-R, %

OCA-HT, %

HCl

5

1.5

J285

5

5

L001

13.4

10

Y001

5

2

Y006

2.5

1.2

Table 7-7: Conditions for Using OCA Formulations Conditions

OCA-R, %

OCA-HT, %

>300 degF

–

*

<300 degF, silt/clay>30%

*

–

>5% Zeolite

–

*



7-9


7-9

Conditions

OCA-R, %

OCA-HT, %

<5% Zeolite

*

–

>5% Chlorite

–

*

<5% Chlorite

*

* Fluid applicable under this condition. – Fluid not applicable under these conditions.

7.7

Preparing Alcoholic Acid Alcoholic acid is a mixture of acid (HCl or mud acid) and alcohol (F003 or K046). Adding alcohol into the acid: • lowers the surface tension • increases the vapor pressure and improves postclean up effectiveness • retards the acid reaction rate and improves success in acidizing low to medium permeability dry gas formations • slightly accelerates the corrosion rate. The concentration of alcoholic acid mixtures indicates the volume percentage of each additive in the acid. For example, an 80:20 alcoholic acid mixture is prepared by mixing 800 mL of acid (e.g., 15% HCl) and 200 mL of alcohol.

Note When the mixture mentioned in the text is prepared, there is a volume loss of 10 mL. 7.8

Mixing Dynamic Acid Dispersion (DAD) A dynamic acid dispersion (DAD*) is an acid outside-phase emulsion stabilized with dispersing agent F103. The dispersion simultaneously dissolves the minerals and removes the oily paraffinic deposits. The dispersion can be prepared with various acids and hydrocarbon solvents. HCl and P121 (toluene) are the most common. Ratios of acid: hydrocarbon can be made from 10 to 50%. Usually 15 galUS/1,000 galUS (15 Lm3) of F103 of acid is used to stabilize the emulsion. You will need the following equipment and materials to mix a DAD: • Waring blender Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


7-10


7-10

• 1,000-mL glass beaker • HCl acid • Corrosion Inhibitor A262 is the inhibitor of choice, except when L036 is used when Organic Corrosion Inhibitor A272 is used • P121. To mix a DAD:

Note Caution: The fumes are hazardous. Prepare the DAD under a fume hood or use appropriate precautions. Wear all appropriate PPE. 1. Prepare 450 mL of 15% HCl acid. Add appropriate corrosion inhibitor for suitable protection time. 2. Place 50 mL of P121 in a Waring blender cup. Add the required quantity of F103. Set the speed on the blender to create a vortex down to the blades of the blender. Mix for 3 minutes. 3. Continue mixing while slowly adding acid through the hole in the blender cup lid. Add a volume equal to the volume of the P121 and the F103 mixture prepared in Step 2. 4. Increase the speed of the Waring blender to around 1,000 rpm. Mix for 10 minutes. An oil-outside phase dispersion should form. The fluid will have some viscosity and may stick to the sides of the blender cup. This is the seed batch dispersion. 5. Continue mixing slowly, and steadily add the acid solution through the hole in the blender lid to the seed batch. The emulsion should invert to become acid-outside phase. The fluid should wet the sides of the blender cup and easily drain down the sides of the cup. 6. Mix 15 minutes more at 1,000 rpm.

Note The DAD cannot be stored for long durations.



8-i

JET Manual 38 / Quality Assurance/Quality Control (QA/QC) Practices

8

8.1 8.2 8.2.1 8.2.2 8.2.3 8.2.4 8.3 8.3.1 8.3.2

8-i

Quality Assurance/Quality Control (QA/QC) Practices Fracture Fluid QA/QC __________________________________________ Acidizing fluid QA/QC __________________________________________ Acid Strength Determination Test _____________________________ Total Iron Content by Spectrophotometry, Titration, or HACH ____ Compatibility Tests ___________________________________________ Corrosion Tests ______________________________________________ Fluid Additives QA/QC _________________________________________ LGD Crosslinker Test _________________________________________ U028 Test ___________________________________________________


8-1 8-3 8-3 8-4 8-4 8-4 8-4 8-4 8-5


8-1


8

8-1

Quality Assurance/Quality Control (QA/QC) Practices PPCG, WS, SFE, JET Manual 38

All fluids used in stimulation treatments must be tested to ensure quality and conformance with the design requirements. The following sections describe quality assurance/quality control (QA/QC) procedures for these tests.

8.1

Fracture Fluid QA/QC The following tests are required: • Perform API (American Petroleum Institute) water analysis on all location water samples. Analysis will include pH, chloride, carbonate, bicarbonate, and iron concentrations. • Perform silicate analysis for all ThermaFRAC*, YF*800HT and YF800LpH fluids. Silicates should be less than 25 ppm (25 mg/L). • Perform bacteria analysis upon request. Bacteria should be less than 3,000,000 counts per L. • Test all concentrated KCl tanks for total hardness. Total hardness should be less than 400 ppm (400 mg/L). • Test all unfamiliar water sources (e.g., pond or lake water) for total hardness. Total hardness should be less than 400 ppm (400 mg/L). • Total hardness strips can be used to analyze the hardness of water. If the total hardness strips indicate values of 425 or greater, use the HACH kit for more accurate determination. The strips are not reliable for high concentrations. • Perform sand sieve analysis on all proppant samples. Of the proppant, 90% must fall within the screen size specified for that proppant for a particular job. Typically, you should have five proppant sample for every 100,000 lbm (45,359 kg) of proppant. • Check field additives for pH, appearance and odor. pH paper may be used for additives, but if a problem is observed, double check the additive with the pH meter.



8-2


8-2

• Prepare a base gel for each fracture tank and check (i.e., if there are six tanks, then six linear gel tests must be performed). The base gel viscosity must fall within the acceptable range before ANY rheological characteristics are measured. Fluid pH will also be checked with a pH probe to ensure the proper pH range (6.0 to 8.0) for polymer hydration. • Verify crosslinked gel properties (pH measured using a pH probe, initial crosslink temperature, and gel lip test) for each fracture tank before measuring rheological properties. The initial crosslink temperature should be within 2 degF of the requested value. • Evaluate the crosslinked gel viscosity using composite water samples and a Fann® 50-type rheometer at 100 s-1. Note If there are fewer water samples than requested Fann tests, then do not use composite samples. • Composite samples are to be prepared using no more than three water samples for a single composite sample (i.e., composite 1 can be made up of samples from tanks 1, 2, and 3, while composite 2 can be made up of samples from tanks 4, 5, and 6, but no composite can be made up of samples from 4 or more water samples). Use different composite samples for different Fann runs to be sure that all water samples are tested. Use 52-mL samples and ISO 13503-1 procedures unless otherwise specified. Note 45-mL samples can be used when bob-climb problems are observed. Perform tests for 20 minutes longer than the job pump time. • Perform break tests with live active breakers using a Fann 50-type rheometer. When using encapsulated breakers, 800-psi (5,520 kPa) overburden pressure is preferred to minimize nonrepresentative release of breaker (450 psi (3,105 kPa) is the minimum pressure regardless of breaker type). To minimize testing, crosslinked gel can be tested with the appropriate amount of encapsulated breaker and be considered similar to those in the absence of breaker, provided the coating is stable at test temperature. • The current rule of thumb for determining the lifetime of a fracturing fluid is the time at which the viscosity falls below 100 cP (100 mPa·s) at a shear rate of 100 s-1 (300 cP (300 mPa·s) at a shear rate of 40 s-1, or 80 cP (80 mPa·s) at a shear rate of 170 s-1), or below a requested level.



8-3


8-3

• Location water should be used for determining break times. Source water can be used if location water is not available with sufficient time for laboratory testing. In such case, a test should be performed with location water to verify test results. • Problems with laboratory testing should be communicated with senior laboratory personnel and the stimulation department. – Changes in the fluid design or problems with the testing must be communicated to the laboratory manager and the fracturing department. – If the laboratory cannot correct poor test results, the fracturing department must be notified directly. The laboratory report should include results, description of problem, and likely source/solution of problem. High rheology data (e.g., in excess of 1,500 cP (1,500 mPa·s) for nonramp or nonspike data) may indicate overdesign of fracturing fluid and the fracturing department should be notified. The fracturing fluid design test results will be plotted on a standard format. The report will be sent to the field or sales engineer requesting the tests.

8.2

Acidizing fluid QA/QC The following requirements are defined in the Key Service Quality Testing Requirements (Fluids and Proppant), InTouch content ID# 3051128, for acid fluid systems. Refer to Stimulation District Lab Procedures, InTouch content ID# 5563263, for steps on how to perform each of those tests.

8.2.1

Acid Strength Determination Test This verification test is to be carried out if the Certificate of Analysis (CoA) by lot number or batch number of every container or delivery of HCl acid received from supplier(s) is not available or cannot be verified. All of the following laboratory tests are required to determine hydrochloric acid concentration in acid concentrate: 1. specific gravity test by hydrometer 2. acid content test by titration with sodium hydroxide 3. chloride content test by titration with silver nitrate.



8-4


8-4

Note The estimated acid concentration of all three tests must agree (±1 wt % HCl) and must be consistent with the nominal HCl concentration of the supplied product. For blended HCl, perform the specific gravity test AND titration test to determine hydrochloric acid concentration at the location to meet final design concentration. 8.2.2

Total Iron Content by Spectrophotometry, Titration, or HACH Total iron content in the raw acid should not exceed 10 ppm (10 mg/L) when received from supplier. For blended acid Total iron content should not exceed 200 ppm (200 mg/L).

8.2.3

Compatibility Tests Compatibility tests should be completed prior to the treatment when crude/condensate/water or any formation fluid sample is available, at a district laboratory. Compatibility testing should be completed within 24 hours of receipt of crude sample.

8.2.4

Corrosion Tests Corrosion tests have to be conducted for unique tubular, temperatures and times that are not covered in the manuals.

8.3

Fluid Additives QA/QC Field additives must be checked for pH, appearance, and odor. pH paper may be used for additives, but a properly calibrated pH meter is preferred. If a problem is observed, double check with the pH meter. The pH should fall within the range. Typical values can be found on each product manual and can also be verified in Quality Assurance (https://ocpqa.slb.com/login.cfm) database. If additive problems are suspected, then measure conductivity and specific gravity. Measure conductivity for all crosslinkers and titrate all buffers and activators to determine actual concentration.

8.3.1

LGD Crosslinker Test You will need the following equipment and materials to test LGD crosslinker: Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


8-5


8-5

• beaker • Orion Model 130A conductivity meter • local water • LGD crosslinker. To test LGD crosslinker: 1. Prepare a standard LGD crosslinker solution of 0.7 ppg (lbm/galUS) L010, 0.5 gpg (galUS/galUS) U028, and 0.45 gpg water, using the local water. 2. Measure the conductivity of the test solution using an Orion Model 130A conductivity meter. Prepare a standard curve of conductivity reading versus temperature. 3. Measure the conductivity on the field-prepared LGD crosslinker solution. 4. Compare the conductivity of the field-prepared LGD crosslinker solution with the standard curve. For this test solution, if the conductivity at 70 degF [21 degC] is 220 mS, the specific gravity should be 1.22. Complete an additional check of the specific gravity to verify the field sample.

8.3.2

U028 Test You will need the following equipment and materials to test the quality of a U028 fluid: • beaker • DI or distilled water • U028 sample • 0.1N HCl acid • phenolphthalein indicator. To test the quality of a U028 fluid: 1. Dilute 1 mL of U028 sample to approximately 50 mL using distilled or deionized water. 2. Add 3 drops (0.25 mL) of phenolphthalein indicator (pink to colorless endpoint). 3. Titrate with 0.100 N HCl to the clear/colorless endpoint. 4. Calculate concentration of U028: 0.100 N HCl (mL) = % U028



8-6


The fluid is acceptable if the concentration of U028 is within ±10% of specification. The field engineer can adjust the field U028 add rate based on the concentration.


8-6


9-i JET Manual 38 / References

9

References

Private


9-i


9-1

JET Manual 38 / References

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References PPCG, WS, SFE, JET Manual 38

These sources will provide more information on stimulation laboratory procedures. • WS QHSE Std 24: Laboratory Operations, InTouch content ID# 3313702 • Well Services - Key Service Quality Requirements (KSQR), InTouch content ID# 4147783 • Fracturing Materials Manual Volume I, Volume II and Volume III: Fluids, InTouch content ID# 4223817 • Matrix Materials Manual, InTouch content ID# 4013354 • Stimulation Client Support Lab Procedures and Information (WPS CSL), InTouch content ID# 3948499.



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Check Your Understanding

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JET Manual 38 / Check Your Understanding

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Check Your Understanding PPCG, WS, SFE, JET Manual 38

1. Choose all true statements regarding eye protection in the laboratory. a. Safety glasses with fixed side shields are required at all times as minimum eye protection (does not apply to offices, rest rooms, or other protected areas not in the laboratory working area). b. Indirect vented chemical goggles must be worn when handling chemicals such as cement, unless these chemicals are in sealed containers. c. Face shields must be worn when handling hot liquids, acids, or liquids that are under pressure, working with flammable liquids where the flash point is less than 100 degF. d. Visitors must wear safety glasses with side shields while in the laboratory work areas. e. All of the above are true. 2. Select two correct statements regarding protective clothing in the laboratory a. Laboratory coats with long sleeves must be worn. b. Rubber or plastic protective aprons must be worn, depending on the type of chemical. Read the MSDSs for the protective clothing requirements. c. Types of clothing that allows exposure to a large area of skin can be worn in a laboratory, e.g., sleeveless tops, short skirts, or short pants. d. Safety boots are not required in the laboratory. Shoes that provide protection from liquids must be worn, such as a leather shoe that covers the foot. Sandals and open shoes are not permitted. 3. Which of the following quality assurance tasks should be done on location before pumping? a. Check the amount of water in each tank, take water sample from each tank, and test the samples. b. Test linear gel viscosity from the outlet of the PCM*/GelSTREAK*. c. Check all the amounts of additives; recalculate to make sure enough for the job is available. d. Test the crosslinker and all additives. e. All of the above are true. 4. Which of the following quality assurance tasks should be performed during pumping?



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a. Throughout the job, the linear gel should be continually checked for viscosity and temperature to confirm the proper gel loading of the gel. b. Samples should be taken from the outlet of the blender or fracture pumps to test the delay time of the crosslinked fluid as well as pH, temperature, bottomhole temperature stability, and break testing (water bath). c. The physical quantities of all liquid and dry additives should be continually checked throughout the job to compare to the designed amount to be pumped. d. All of the above should be done. 5. Choose the correct statement regarding API gravity. a. The equation relating specific gravity to API gravity is

SG =

141.5 131.5 + API

b. The higher the API gravity, the heavier the fluid. c. The higher the API gravity, the lighter the fluid. d. Both a and c are true. e. None of the above is true. 6. Which statement regarding pH is incorrect? a. The normal pH range for brines is between 6 to 8. b. The normal pH range for fracture fluids is 11 to 12. c. A low pH may indicate spent acid. d. A high pH may indicate contamination by mud or filtrate. 7. Which statements are true regarding specific gravity? a. Specific gravity is the ratio of the weight of material to the weight of water, or the density of the material to the density of water. b. The higher the specific gravity is, the heavier the liquid is. c. Specific gravity can be used to differentiate hydrocarbons (condensate) from water. Freshwater has a specific gravity of 1.000. d. A hydrometer is the device used to measure specific gravity. e. All of the above are true. 8. Alkalinity tests include: a. SG and pH tests b. Bicarbonates, carbonates, and hydroxide test c. All of the above are true.



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d. None of the above are true. 9. Choose all correct statements about bicarbonates. a. Bicarbonates are very important for fracture fluid quality control. b. Fracturing fluids require various bicarbonate concentrations, depending on the specific fluid. c. High bicarbonates will tend to slow gel hydration and delay fluid crosslinking. d. High bicarbonate levels may be characterized by a high pH or be an indication of carbonates present in the water. e. All of the above are true. 10. Choose the correct statement(s) regarding carbonates and hydroxides. a. Most formations contain high levels of carbonates or hydroxides. b. If the water sample contains carbonate and/or hydroxide, it may be a clue to a problem in the customer’s well, possibly indicating the presence of some drilling mud contamination. c. Most oilfield waters will contain only bicarbonates, but occasionally carbonate and/or hydroxide will be present. d. None of the above are true. 11. Choose the correct statement about chloride. a. Most fracture fluids today comprise 2% KCl. b. The chloride content of a 2% KCl solution should be approximately 9,600 mg/L. c. The chloride test can also be used to determine if a sample is spent acid. d. All of the above are true. 12. How would you identify H2S in the sample? a. The water sample is very cloudy. b. The sample smells like rotten eggs. c. The sample has large particles floating in it. d. None of the above are true. 13. The hardness tests include a test for: a. Sulfur and magnesium b. Calcium and magnesium c. Calcium and potassium d. Sodium and potassium 14. Choose all true statements regarding iron.



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a. When high iron is encountered in fracture mix water, breaker J218 (ammonium persulfate) will have an accelerated effect. b. In high iron environments, J218 may cause premature break of the fracturing fluid. c. High iron content will interfere with the crosslinking of the fracturing fluid, resulting in poor crosslink integrity. d. The maximum iron concentration for fracture water ranges from 8 to 25 ppm, depending on the fluid. e. All of the above are true. 15. Which instrument is used to determine viscosity of linear fluids? a. Spectrophotometer b. Fann® Model 35 rheometer (Fann 35) c. Hydrometer d. None of the above 16. What is the vortex closure test? a. The vortex closure test indicates the onset of viscosity development, and rarely coincides with full crosslinking. b. The vortex closure test indicates full crosslinking. c. None of the above are true. 17. What are three distinct fluid behaviors during a vortex closure test in the order in which they occur? 1. Fluid crowning, which is the formation of a dome of fluid over the center of the blender cup (over the blades). This is the point at which the fluid no longer completely circulates in the blender cup. 2. Viscosity increase that results in closure of the vortex, but does not stop fluid circulation in the blender cup. 3. Linear fluid behavior, characterized by a deep vortex a. 1, 2, 3 b. 2, 3, 1 c. 3, 2, 1 d. 1, 3, 2 18. Which statement is true regarding the static gel break test? a. The static gel break test tests for the time at which the gel breaks enough to flow back. b. A gel is usually considered broken enough to flow back when it has degraded to a viscosity of 20 cP at the required temperature.



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c. This test is important for the field operation that does not have high-pressure, high-temperature (HPHT) gel break test equipment. d. All of the above are true. 19. What instrument is used to perform a crosslinked gel breaking test when a bottomhole temperature is above 100 degC? a. A Fann Model 35 type rheometer b. A Fann Model 50 type rheometer c. A Waring blender d. None of the above 20. What is the proppant turbidity test used for? a. To determine the shape of the sand b. To determine the cleanliness of the fracture sand (amount of fines) c. To determine the toughness of the sand d. None of the above 21. Which statement is true about the fracturing fluids? a. The WideFRAC 100HTD (YF*100HTD) fracturing fluids are water-base systems comprising a refined guar gelling agent crosslinked by a borate-type crosslinker. b. YF800HT fluids are temperature- activated, zirconate-crosslinked waterbase fluids that use CMHPG as a gelling agent. c. YF GO* V is a gelled, oil-base fluid used as a fracturing fluid for the treatment of water-sensitive formations. Diesel, kerosene, condensate, and a wide variety of crude oils can be used to prepare YF GO V. d. All of the above are true. 22. Which is true about SXE* (SuperX* Emulsion)? a. SXE is a viscous, highly retarded, concentrated acid system designed for use in matrix acidizing or acid fracturing of carbonate formations. b. SXE is an oil-external phase emulsion formed with a 70:30 HCl-to-oil ratio, stabilized with an emulsifier. c. HCl concentrations ranging from 15 to 28% may be used. d. The temperature range of SXE is 75 to 350 degF. e. All of the above are true. 23. Which of the following systems are most used for carbonate acidizing? a. CLEAN SWEEP* b. HCl c. Mud acid, ClayACID* Private Copyright © 2014 Schlumberger, Unpublished Work. All rights reserved.


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d. None of the above 24. Which of the following systems are most used for sandstone acidizing? a. DAD*, SXE b. HCl c. Mud acid, ClayACID d. None of the above 25. What is mud acid? a. A mixture of clay acid and acetic acid b. A mixture of inhibited HCl acid and hydrofluoric acid c. A mixture that can not only dissolve the minerals that HCl acid can dissolve, but can also dissolve siliceous minerals presented in most sandstone formations d. b and c e. None of the above 26. What does DAD stand for? a. Diluted acid dispersion b. Dynamic acid dispersion c. Diffusion additives dispersion d. None of the above


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JET Manual 38 version 2_1_4298920_01.pdf

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