A TECHNICAL REPORT ON STUDENTS’ INDUSTRIAL
WORK EXPERIENCE SCHEME (SIWES)
UNDERTAKEN AT PAN OCEAN OIL CORPORATION PLOT 13/14 LIGALI AYORINDE AVENUE, VICTORIA ISLAND, LAGOS, NIGERIA. BY ADIE UNIMKE CHINONSO (14/ENG05/029) SUBMITTED TO THE DEPARTMENT OF MECHANICAL & MECHATRONICS ENGINEERING COLLEGE OF ENGINEERING, AFE BABALOLA UNIVERSITY, ADO-EKITI, NIGERIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF BACHELOR OF ENGINEERING (B.ENG) IN MECHATRONICS ENGINEERING
SEPTEMBER, 2017.
CERTIFICATION This is to certify that this work titled Students’ Industrial Work Experience Scheme (S IWES) was undertaken at Pan Ocean Oil Corporation by Adie Unimke Chinonso with matriculation number 14/ENG05/029 and the report was submitted to the Department of Mechanical & Mechatronics Engineering, College of Engineering, Afe Babalola University, Ado-Ekiti.
____________________
______________________
Engr. Musa Mohammed
Signature & Date
Supervisor
____________________
_______________________
Engr. Prof. A. A. Aderoba
Signature & Date
Head of Department Mechanical & Mechatronics Engineering
i
CERTIFICATION This is to certify that this work titled Students’ Industrial Work Experience Scheme (S IWES) was undertaken at Pan Ocean Oil Corporation by Adie Unimke Chinonso with matriculation number 14/ENG05/029 and the report was submitted to the Department of Mechanical & Mechatronics Engineering, College of Engineering, Afe Babalola University, Ado-Ekiti.
____________________
______________________
Engr. Musa Mohammed
Signature & Date
Supervisor
____________________
_______________________
Engr. Prof. A. A. Aderoba
Signature & Date
Head of Department Mechanical & Mechatronics Engineering
i
DEDICATION I dedicate this report to the Almighty God, for seeing me through the period of attachment, and to my Parents: Mr & Mrs U. A. Adie for their love, support and encouragement.
ii
ACKNOWLEDGEMENT I would like to acknowledge the Almighty God for making it possible to successfully complete my industrial training at Pan Ocean Oil Corporation, and my parents for their love, support and encouragement. I also wish to acknowledge the university for giving me the opportunity to participate in the Students’ Industrial Work Experience Scheme (SIWES) and giving me the opportunity to work at Pan Ocean Oil Corporation. Finally, I would like to acknowledge my industrial based supervisors, Mr Azubuike Umeoduagu, Mr Frederick Roman and Mr Collins Akinkugbe for their guidance and support, and the entire staff of the company.
iii
ABSTRACT The Students’ Industrial Work Experience Scheme (SIWES) is a skill training programme designed to expose and prepare students of tertiary institutions for the industrial work situation they are likely to encounter after graduation. This SIWES report gives details about all the work carried out and the relevant experience gained at Pan Ocean Oil Corporation, Lagos. The six-month program involved majorly gaining the theoretical knowledge concerned with the operations of a flow station, operating principle of wellheads, manifolds and gravity separators. The second part of the training involved working at the production department of the OML 98 flow station at Ogharefe, Delta State, where monitoring operations involving monitoring abnormal wellhead pressure, restarting failed wellheads, monitoring gravity separators, carrying out crude oil sampling, BS&W analysis and API gravity calculations on said samples, crude oil metering and export, oil skimming operations were carried out. This report gives detailed information on all the areas afore mentioned, and defines clearly the experience gained throughout the course of the program, along with the challenges encountered and various recommendations.
iv
TABLE OF CONTENTS CERTIFICATION ........................................................................................................................... i DEDICATION .................................................. .............................................................................. ii ACKNOWLEDGEMENT ................................................... .......................................................... iii ABSTRACT ................................................................................................................................... iv TABLE OF CONTENTS ................................................................................................................ v LIST OF FIGURES ..................................................................... ................................................. vii LIST OF TABLE .................................................................................. ....................................... viii CHAPTER ONE ............................................................................................................................. 1 INTRODUCTION .......................................................................................................................... 1 1.1
Background of SIWES ......................................................................................................... 1
1.2
Objectives of SIWES ........................................................................................................... 1
1.3
Log Book ............................................................................................................................. 2
1.4
Pan Ocean Oil Corporation (POOC) ................................................... ................................. 2
1.4.1
History and scope of work .................................................. .......................................... 2
1.4.2
POOC gas plant ............................................................................................................ 3
1.5
Safety Equipment and Precautions ...................................................................................... 4
CHAPTER TWO ............................................................................................................................ 5 LITERATURE REVIEW ............................................................................................................... 5 2.1
Introduction .......................................................................................................................... 5
2.2
Process Overview................................................................................................................. 5
2.3
Onshore ................................................................................................................................ 7
2.4
Main Process Sections ......................................................................................................... 8
2.4.1
Wellheads ..................................................................................................................... 8
2.4.1.1
Description of christmas tree................................................................................. 8
2.4.2
Manifolds/Gathering .................................................. ................................................. 10
2.4.3
Separation ................................................................................................................... 10
2.4.3.1
Test separators and well test................................................................................ 11
2.4.3.2
Production separators .......................................................................................... 11
2.4.4
Gas compression ................................................ ......................................................... 12
2.4.5
Metering, storage and export .............................................. ........................................ 13
2.5
Reservoir and Wellheads ................................................................................................... 14 v
2.6
Early Production Facility (EPF)......................................................................................... 14
2.7
Valves ................................................................................................................................ 14
2.7.1
Check valve ................................................................................................................ 14
2.7.2
Gate valve ................................................................................................................... 15
2.7.3
Butterfly valve ................................................... ......................................................... 16
CHAPTER THREE ...................................................................................................................... 17 MONITORING OF FLOW STATION OPERATIONS .............................................................. 17 3.1
Monitoring Wellhead Pressure .......................................................................................... 17
3.2
Oil Metering and Export ................................................... ................................................. 18
3.3
Sampling Analysis of Crude Oil ........................................................................................ 19
3.3.1
Method of performing BS&W analysis ................................................ ...................... 20
3.3.2
Method of calculating API gravity of a sample .......................................................... 21
3.3.3
Method of Correcting Observed API using National Standard Petroleum Oil Tables23
3.4
Crude Oil Skimming .......................................................................................................... 23
CHAPTER FOUR ............................................. ............................................................................ 25 EXPERIENCE GAINED AND CHALLENGES ENCOUNTERED .......................................... 25 4.1
Experience Gained ......................................................................................................... 25
4.2
Challenges Encountered ................................................ ................................................. 25
CHAPTER FIVE .......................................................................................................................... 26 CONCLUSION AND RECOMMENDATIONS ......................................................................... 26 5.1
Conclusion ................................................... ................................................................... 26
5.2
Recommendations .......................................................................................................... 26
REFERNCES ................................................................................................................................ 27 APPENDIX .............................................. ..................................................................................... 28
vi
LIST OF FIGURES FIGURE
TITLE
PAGE
1.1
Personal Protective Equipment
4
2.1
Oil and gas production overview
6
2.2
Typical Wellhead Schematic
9
2.3
Gravity Separator
10
2.4
Cross Section of a gravity separator
11
2.5
Array of LP (Low Pressure), HP (High Pressure),
12
IP (Intermediate Pressure) and test separators 2.6
Check Valve
16
2.7
Gate Valve
16
2.8
Butterfly Valve
17
3.1
Restarted Wellhead
15
3.2
Metering at LACT unit
16
3.3
Crude sample after centrifugal action
18
3.4a
Method of reading the hydrometer
19
3.4b
Method of reading the hydrometer
19
3.5a
Hydrometer inside crude oil
20
3.5b 3.6
Reading temperature from the hydrometer Crude oil skim pit
vii
20 21
LIST OF TABLE Table 1
Units of Measurement
viii
28
CHAPTER ONE INTRODUCTION 1.1 Background of SIWES The Students’ Industrial Work Experience Scheme (SIWES) is a skill training programme designed to expose and prepare students of tertiary institutions for the industrial work situations they are likely to encounter after graduation. The scheme also affords the students the opportunity of familiarizing themselves with the needed experience in handling equipment and machineries. The scheme was initiated in 1973 by the Industrial Training Fund (ITF). It is a tripartite programme involving the students, the Universities and Industries. It is a Federal Government of Nigeria funded programme. It is jointly coordinated by the ITF and the National Universities Commission (NUC). The importance and benefits of this programme, short in period as it may be, cannot be over emphasized. It provides the students an opportunity to visualize and even practice the theories and principles they have learned in classroom. The training gives the students a potential workforce, a light into the demands of the labour market. This experience serves as an eye -opener to the students as well as a guide to decision making and choice of career (ITF, 2003).
1.2 Objectives of SIWES According to ITF (2003), the objectives of the scheme include the following: i.
It provides students the opportunity to apply the theoretical principles taught in school in real job situation. This leads to better understanding of the subject matter.
ii.
It affords students the opportunity to interact with a larger spectrum of people in industrial setup, which is different from campus life. Hence, this helps personality and maturity development.
iii.
It enables the students to prepare for the future world of work. This is an opportunity for them to peep into the future and determine how much they are ready for it.
iv.
It helps the students in developing intellectual skills as they are often left on their own to take technical decisions, analyse complex interdisciplinary problems and proffer appropriate solutions, applicable to real solutions. 1
1.3 Log Book This is the booklet for recording daily and weekly activities by the students, the industrial based supervisor is required to endorse the log book every week as well as the institutional supervisor is to sign the log book during supervision. The training logbook clearl y states the training objectives. It emphasizes and shows one’s personal observations and interest in the training, one’s capability on problem solving and the ability to comment and make suggestions for improvement in a constructive and professional manner.
1.4 Pan Ocean Oil Corporation (POOC) Pan Ocean Oil Corporation Nigeria Limited is an indigenous Exploration and Production Company with investments and operating interests in the Nigerian oil and gas industry. The Company is governed by a board of directors with proven integrity and driven by a dynamic management team with broad knowledge and experience in the oil and gas industry.
1.4.1
History and scope of work
Pan Ocean Oil Corporation (POOC) was incorporated as an Exploration and Production company in 1973. Soon after, Oil Prospecting License (OPL) 70/71 which was originally granted to Delta Oil Company was framed out to Pan Ocean Oil Corporation Incorporated of New York. In December 1975, OPL 70/71 was converted to Oil Mining Lease (OML) 98. Pan Ocean commenced crude oil production in August 1976 at the Ogharefe field of OML 98 which is situated in the northern fringe of the Niger Delta region of Nigeria. Pan Ocean has been in a Joint Venture with the Nigeria National Petroleum Company (NNPC) in respect of OML 98. As a Joint Venture (JV) partner, the NNPC has 60 percent working interest in OML-98 while Pan Ocean has 40 percent. Through strategic planning, aggressive exploration and production activities and tenacity, Pan Ocean acquired the Oil Prospecting License 275 during the 2008 bid round. In 2009, Pan Ocean signed a Production Sharing Contract (PSC) with the NNPC on Oil Prospecting License (OPL) 275.
2
The company commenced crude oil production at the Ogharefe field (OML 98) with an initial production of about 11,000bpd in 1976. The field penetrates several formations including the Benin, Agbada and Akata formations. She started production in 1976, with cumulative oil production amounting to about forty-five million barrels from the thin reservoir sands asso ciated with the Northern Depositional Belt of the Niger Delta. Over 47 wells have been drilled in OML 98. The company acquired Oil Prospecting License 275 (OPL 275) during the 2008 bid round. OPL 275 was contracted to Pan Ocean under a Production Sharing Contract (PSC) with the NNPC.
Pan Ocean is the operator of OML98 which is a Joint Venture with the Nigeria National Petroleum Company (NNPC). As part of its strategic growth initiative, Pan Ocean acquired and signed a Production Sharing Contract (PSC) with the NNPC on OML 147 (previously OPL 275).
1.4.2
POOC gas plant
The Ovade-Ogharefe gas processing plant is a trail blazing initiative in gas development. The plant has a production design capacity of 130MM SCF/D (million standard cubic feet per day. The Ovade-Ogharefe Gas Processing Plant is designed to provide for the allocated gas supply of 65mmcf/d to Egbin power station, a subsidiary of the Power Holding Company of Nigeria (PHCN). The plant will further supply LPG (liquefied petroleum gas) to the Nigerian domestic market when fully completed. Pan Ocean signed the Gas Sales Aggregation Agreement with the Federal Government and Egbin power station, subsidiary of PHCN in June 2010. Pan Ocean has developed and completed the 130MMSCF/D Ovade-Ogharefe natural gas processing plant. In 2009, became one of the few companies to sign on to the Carbon Credits scheme offered by the Clean Development Mechanism (CDM) in the Kyoto Protocol and currently remains the largest registered carbon-emission reduction project in West Africa.
3
1.5 Safety Equipment and Precautions Pan Ocean Oil Corporation is very concerned when it comes to safety in and out of site. On the work site, safety is even a more serious business than the job itself. To ensure safety of workers, environment and equipment, certain rules were put in place. Some of these rules include: i.
Work with a valid work permit when required.
ii.
Do not walk under a suspended load.
iii.
Conduct gas tests when required.
iv.
While driving, do not use your phone and do not exceed speed limits.
v. vi.
Do not smoke outside designated smoking areas. Verify isolation before work begins and use the specified life protecting equipment.
vii.
No alcohol or drugs while working or driving.
viii.
Obtain authorization before entering a confined space.
ix.
Wear your seat belt.
x. xi. xii.
Obtain authorization before overriding or disabling safety critical equipme nt. Protect yourself against a fall when working at height. Follow prescribed journey management plan.
Aside the above, the company also has a strong PPE policy (Figure 1.1). The company’s “NO PPE, NO ENTRY” policy holds for all workers on site.
Figure 1.1: Personal Protective Equipment
4
CHAPTER TWO LITERATURE REVIEW 2.1 Introduction Oil has been used for lighting purposes for many thousands of years. In areas where oil is found in shallow reservoirs, seeps of crude oil or gas may naturally develop, and some oil could simply be collected from seepage or tar ponds. But it was not until 1859 that Edwin Drake drilled the first successful oil well, with the sole p urpose of finding oil. The Drake Well was located in the middle of quiet farm country in north-western Pennsylvania, and began the international search for an industrial use of petroleum. Soon, oil had replaced most other fuels for motorised transport. The automobile industry developed at the end of the 19th century, and quickly adopted oil as fuel. Gasoline engines were essential for designing successful aircrafts. Ships driven by oil could move up to twice as fast as their coal powered counterparts, a vital military advantage. Gas was burned off or left in the ground. Despite attempts at gas transportation as far back as 1821, it was not until after the World War II that welding techniques, pipe rolling, and metallurgical advances allowed for the construction of reliable long distance pipelines. Resulting in a natural gas industry boom. At the same time the petrochemical industry with its new plastic materials quickly increased production, even now gas production is gaining market share as LNG provides an economical way of transporting the gas from even the remote sites. With oil prices of about 50 dollars a barrel or more, even more difficult to access sources have become economically viable. Such sources include tar sands in Venezuela and Canada as well as oil shales. Synthetic diesel (syndiesel) from natural gas and biological sources (biodiesel, ethanol) has also become commercially viable. These s ources may eventually more than triple the potential reserves of hydrocarbon fuels. (Håvard, 2009).
2.2 Process Overview The following illustration (Figure 2.1) gives a simplified overview of the typical oil and gas production process 5
Figure 2.1: Oil and Gas Production Overview (Håvard Devold, 2009).
6
At the left side, we find the wellheads. They feed into production and test manifolds. In a distributed production system, this would be called the gathering system. The remainder of the diagram is the actual process, often called the Gas Oil Separation Plant (GOSP0. While there are oil or gas only installations, more often the well-stream will consist of a full range of hydrocarbons from gas (methane, butane, propane etc.), condensates (medium density hydrocarbons) to crude oil. With this well flow we will also get a variety of unwanted components such as water, carbon dioxide, salts, sulphur and sand. The purpose of the GOSP is to process the well flow into clean marketable products: oil, natural gas or condensates. Also included are a number of utility systems, not part of the actual process, but providing energy, water, air or some other utility to the plant. (Håvard, 2009).
2.3 Onshore Onshore production is economically viable from a few dozen barrels of oil a day and upwards. Oil and gas is produced from several million wells world-wide. In particular, a gas gathering network can become very large, with production from thousands of wells. Several hundred kilometres/miles apart, feeding through a gathering network into a processing plant. For the smallest reservoirs, oil is simply collected in a holding tank and picked up at regular intervals by tanker truck or railcar to be processed at a refinery. But onshore wells in oil rich areas are also high capacity wells with thousands of barrels per day, connected to a 1,000,000 barrels or more a day gas oil separation (GOSP). Product is sent from the plant by pipeline or tankers. The production may come from many different license owners, therefore metering and logging of individual well-streams into the gathering network are important tasks. Recently, very heavy crude, tar sands and oil shale have become economically extractable with higher prices and new technology. Heavy crude may need heating and d iluents to be extracted. Tar sands have lost their volatile compounds and are strip mined or can be extracted with stream. It must be further processed to separate bitumen from the sand. These unconventional reserves may contain more than double the hydrocarbons found in conventional reservoirs. (Håvard, 2009).
7
2.4 Main Process Sections The main process sections of a typical oil and gas production process is summarised below:
2.4.1
Wellheads
The wellhead sits on top of the actual oil or gas well leading down to the reservoir. A wellhead may also be an injection well used to inject water or gas back into the reservoir to maintain pressure and levels to maximise production. Once a natural gas or oil well is drilled, and it has been verified that commercial viable quantities of natural gas are present for extraction, the well must be ‘completed’ to allow for the flow of petroleum or natural gas out of the formation and up to the surface. This process includes strengthening the well hole with casting, evaluation the pressure and temperature pf the formation, and then installing the proper equipment to ensure an efficient flow of natural gas from the well. The well flow is controlled with a choke. We differentiate between, dry completion (which is either onshore or on the deck of an offshore structure) and subsea completions below the surface. The wellhead structure, which is often called a Christmas tree, must allow for a number of operations relating to production and well workover. Well workover refers to various technologies for maintaining the well and improving its production capacity. (www.marginalwells.com).
2.4.1.1 Description of christmas tree A typical christmas tree composed of a master gate valve, a pressure gauge, a wing valve, a swab valve and a choke is shown in Figure 2.2. The functions of these devices are explained in the following paragraphs. At the bottom we find the casing head and casing hangers. The casing is screwed, bolted or welded to the hanger. The tubing hunger is used to position the tubing correctly in the well. Sealing also allows christmas tree removal with pressure in the casing. The master gate valve provides full opening to the tubing so that specialised tools may be run through it. It is capable of holding the full pressure of the well safety for all anticipated purposes. 8
The pressure gauge is laced above the master valve before the wing valve. The wing valve can be a gate or ball valve. When shutting in the well, the wing gate or valve is normally used so that the tubing pressure can be easily read. The swab valve is used to gain access to the well for wireline operations, intervention and other workover procedures. The variable flow choke valve is typically a large needle valve. Its calibrated opening is adjustable in 1/64 inch increments (called beans). It is simply a built-in restriction that limits flow when the wing valve is fully open. (Håvard, 2009).
Figure 2.2: Typical Wellhead Schematic (Håvard, 2009). 9
2.4.2
Manifolds/Gathering
Onshore, the individual well streams are brought into the main production facilities over a network of gathering pipelines and manifold systems. The purpose of these pipelines is to allow set up pf production “well sets” so that for a given production level, the best reservoir utilization, well flow composition (gas, oil, waster) etc. can be selected from the available wells.
2.4.3
Separation
Some wells have pure gas production which van be taken directly to gas treatment and/or compression. More often, the well gives a combination of gas, oil and water and various contaminants which must be separated and processed. The production separators come in many forms and designs, with the classical variant being the gravity separator (Figure 2.3).
Figure 2.3: Gravity Separator (Håvard, 2009).
In gravity separation, the well flow is fed into a horizontal vessel. The retention period is typically 5 minutes, allowing the gas to bubble out, water to settle at the bottom and oil to be taken out in the middle. The pressure is often reduced in several stages (high pressure separator, low pressure separator etc.) to allow controlled separation of volatile components. A sudden pressure reduction might
allow
flash
vaporization
leading
(www.glossary.oilfield.slb.com, 2017)
10
to
instability
and
safety
hazards.
2.4.3.1 Test separators and well test Test separators are used to separate the well flow from one or more wells for analysis and detailed flow measurement. In this way, the behaviour of each well under different pressure flow conditions can be defined. This normally takes place when the well is taken into production and later at regular intervals, typically 1-2 months and will measure the total and component flow rates under different production conditions.
2.4.3.2 Production separators The main separators used at the flow station were gravity types. The pressure is often reduced in several stages, in this instance, three stages are used to allow the controlled separation of volatile components. The idea is to achieve maximum liquid recovery and stabilized oil and gas and to separate water. The retention period is typically 5 minutes, allowing the gas to bubble out, water to settle at the bottom and oil to be taken out in the middle as shown in Figure 2.4. At the inlet, there is a slug catcher that will reduce the effect of slugs (large bubbles or liquid plugs). However, some turbulence is desirable as this will release gas bubbles faster than a laminar flow. At the end, there are barriers up to a certain level to keep back the separated oil and water. The main control loops are the oil level control loop controlling the oil flow out of the separator on the right, and the gas pressure loop at the top. Those loops are operated by the control system. (www.doe.gov, 2017).
Figure 2.4: Cross Section of a Gravity Separator (Håvard, 2009). 11
The Figure 2.5 shows an array of the gravity separators used at OML 98 flow station.
Figure 2.5: Array of LP (Low Pressure), HP (High Pressure), IP (Intermediate Pressure) and Test Separators
2.4.4
Gas compression
Gas from a pure natural gas wellhead might have sufficient pressure to feed directly into a pipeline transport system. Gas from separators has generally lost so much pressure that it must be recompressed to be transported. Turbine compressors gain their energy by using up a small proportion of the natural gas that they compress. The turbine itself serves to operate a centrifugal compressor, which contains a type of fan that compresses and pumps the natural gas through the pipeline.
Some compressor stations are operated by using an electric motor to turn the same type of centrifugal compressor. This type of compression does not require the use of an y of the natural gas from the pipe; however, it does require a reliable source of electricity nearby. The compression includes a large section of associated equipment such as scrubbers (to remove liquid droplets) and heat exchangers, lube oil treatment etc. Whatever the source of the natural gas, once separated from crude oil (if present) it commonly exists in mixtures with other hydrocarbons; principally ethane, propane, butane, and pentanes. In
12
addition, raw natural gas contains water vapour, hydrogen sulphide (H2S), carbon dioxide, helium, nitrogen, and other compounds. Natural gas processing consists of separating all of the various hydrocarbons and fluids from the pure natural gas, to produce what is known as 'pipeline quality' dry natural gas. Major transportation pipelines usually impose restrictions on the natural gas that is allowed into the pipeline. That means that before the natural gas can be transported it must be purified. Associated hydrocarbons, known as ‘natural gas liquids’ (NGL) are used as raw materials for oil refineries or petrochemical plants, and as sources of energy. (Håvard, 2009).
2.4.5
Metering, storage and export
Most plants do not allow local gas storage, but oil is often stores before loading on a vessel, such as a shuttle tanker taking oil to a larger tanker to a crude carrier. Offshore production facilities without a direct pipeline connection generally rely on crude storage in the base or hull, to allow a shuttle tanker to offload about once a week. A larger production complex generally has an associated tank farm terminal allowing the storage of different grades of crude to take up changes in demand, delays in transport etc. Meering stations allow operators to monitor and manage the natural gas and oil ex ported from the production installation. These emplooy specialised meters to measure the natural gas or oil as it flows through the pipeline, without impeding its movement. This metered volume represents a transfer of ownership from a producer to a customer (or another division within the company) and is therefore called Custody Transfer Metering. It forms the basis for invoicing the sold product and aslo for production taxes and revenue sharing between partners and accuracy requirements are often set by governmental authorities. A metering installation typicall consists of a number of meter runs so that one meter will not have to handle the full capacity rnage, and associated prover loops so that the meter accuracy can be tested and calibrated at regular intervals. (setxind.com, 2017)
13
2.5 Reservoir and Wellheads There are three main types of conventional wells. The most co mmon is an oil well associated gas. Natural gas wells are drilled specifically for natural gas, and contain little or no oil. Condensate wells contain natural gas, as well as a liquid condensate. This condensate is a liquid hydrocarbon mixture that is often separated from the natural gas either at the wellhead, or during the processing of the natural gas. Depending on the type of well that is being drilled, completion may differ slightly. It is important to remember that natural gas, being lighter than air, will naturally rise to the surface of a well. Consequently, lifting equipment and well treatment are not necessary in many natural gas and condensate wells, while for oil wells many types of artificial lift might be installed, particularly as the reservoir pressure falls during years of production. (Håvard, 2009).
2.6 Early Production Facility (EPF) An early production facility is a complete facility to produce oil and gas and dispose of the produced water. This facility is usually located on land, but barge facilities are also becoming common. The size range is usually between 5,000 to 60,000 barrels per Early production facilities are becoming very important to the oil companies due to the necessity to get a field or some part of a field on line and producing in a minimum amount of time. (www.glossary.oilfield.slb.com, 2017)
2.7 Valves The following valves were used at the OML 98 flow station at Ogharefe.
2.7.1
Check valve
This is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Typically, the check valve is designed for and can therefore be specified for a specific cracking pressure. (www.usplastic.com, 2017). 14
Figure 2.6: Check Valve (www.usplastic.com, 2017).
2.7.2
Gate valve
Gate valves are actuated by a threaded stem which connects the actuator (e.g. hand wheel or motor) to the gate. They are characterised as having either a rising or a non-rising stem, depending on which end of the stem is threaded. Rising stems are fixed to the gate and rise and lower together as the valve is operated, providing a visual indication of valve position. The actuator takes the form of a nut which is rotated around the threaded stem to move it. Non-rising stem valves are fixed to, and rotate with, the actuator, and are threaded into the gate. They may have a pointer threaded onto the upper end of the stem to indicate valve position, since the gate's motion is concealed inside the valve. Non-rising stems are used underground or where vertical space is limited. (www.stoneleigh-eng.com, 2017)
Figure 2.7: Gate Valve (www.stoneleigh-eng.com, 2017)
15
2.7.3
Butterfly valve
Butterfly valves are most simple yet versatile valves. The y are quarter turn operated valves which are commonly used in multiple industries for varied applications. Quarter turn operation ensures quick operating of the valve. In the open condition there is minimum obstruction to the fluid flow through the valve as the flow passes around the disc aerodynamically. This results in very less pressure drop through the valve. Due to its unique mode of operation, the valve can be actuated easily without requiring high torques and wear and tear. Due to lack of friction, use of bulky actuators can be avoided. (www.forbesmarshall.com, 2017).
Figure 2.8: Butterfly Valve (www.forbesmarshall.com, 2017).
16
CHAPTER THREE MONITORING OF FLOW STATION OPERATIONS During the course of the industrial training program at Pan Ocean Oil corporation, The Student worked as an intern in the Production Department of the OML 98 flow station at Ogharefe, Delta state. The department was in charge of monitoring the production processes of the flow station. The activities monitored include: i.
Monitoring wellhead pressure
ii.
Oil metering and export
iii.
Sampling analysis of crude oil
iv.
Monitoring crude oil skimming operations.
Before working on different areas, the student was required to have basic concepts employed in monitoring operations in the flow station.
3.1 Monitoring Wellhead Pressure Since the flow station was situated onshore, the wellheads employed involved d ry completion. The wellhead has an equipment mounted at the opening of the well to regulate and monitor the extraction of hydrocarbons from the underground formation. This also prevents oil or natural gas leaking out of the well, and prevents blow-outs due to high pressure formation. Formations that are under high pressure typically require wellheads that can withstand a great deal of upward pressure from the escaping gases and liquids. it was made known that a typical wellhead consisted of three components: the casing head, the tubing head, and the Christmas tree. During wellhead monitoring, it was discovered that the pressure of a particular well was below its normal operating pressure. The work carried out at the wellhead was completely mechanical and is summarised below: i. ii.
First, aligning a sub-surface valve in order to resume wellhead operation. Before this was achieved, the valve had to be realigned by applying pressure at the top of the well head.
iii.
Said pressure was applied by first opening the top of the well head and moving water into the christmas tree. 17
iv. v.
Thereafter, high pressure gas was pumped into the water to try realign the valve. After reopening the valve, the wellhead became operational, and the recorded pressure was back to operational.
Figure 3.1: Restarted Wellhead
3.2 Oil Metering and Export I was involved in metering produced oil at the NPDC (Nigerian Petroleum Development Company) LACT (Lease Automatic Custody Transfer) unit. Partners, authorities and customers all calculate invoices, taxes and payments based on the actual product shipped out. Often custody transfer also takes place at this point, which means transfer of responsibility or title from the producer to a cus tomer, tanker operator or pipeline operator. When working at the LACT unit, the procedure for metering are described below: i.
The quantity of oil (in bbl.) produced is checked at the LACT unit, every 4 hours. For 24 hours of the day.
ii.
The quantity of oil read from the meter is recorded with an orifice meter.
iii.
This is how the company is able to know how much crude oil is being transported to the export terminals. (refer to Figure 3.2).
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It is important to calculate quantity of produced oil because the pipelines running to the export lines are used by different oil producing companies simultaneously, therefore, measurement has to be made for one particular company in other for payment to be made. Before payment is made at the export terminal, it is assumed that crude is 100% processed, and still contains some amount of water. Therefore, the need for sampling analysis is required.
Figure 3.2: Metering at LACT unit
3.3 Sampling Analysis of Crude Oil The following factors play a significant role in affecting both the quality and quantity of crude oil. As such it is crucial that the LACT Unit be able to accurately gauge and track these:
Temperature – The temperature of the crude oil affects its overall volume as the fluid expands or contracts in response to temperature change. However, the way temperature affects crude oil is not uniform across all crude oil because the crude oil itself is not uniform. Instead different levels of API gravity will cause the temperature to have a more or less significant effect on the crude oil.
API Gravity – API Gravity refers to American Petroleum Institute gravity. This is measurement developed by the American Petroleum Institute which describes how heavy or light crude oil is in 19
relation to water. If the API gravity is more than 10 then the crude is light and will float on water. If the API gravity is less than 10 the crude is heavy and will sink. API gravity determines how much the crude is worth because light crude will produce a higher yield of gasoline or diesel when it is refined.
Basic Sediment & Water – Basic Sediment & Water, typically abbreviated BS&W refers to the sediment, water content, and emulsion in the production stream. Naturally since these are impurities, and not part of the actual merchantable oil, they must be carefully measured and factored into the value accordingly. LACT units are typically equipped with BS&W probes to collect the data and BS&W monitors to store and manager the data, but the NPDC LACT unit at OML 98 had no equipment for calculating BS&W. Therefore, it was calculated manually.
3.3.1
Method of performing BS&W analysis
Procedure involved in calculating BS&W can be summarised as follows: i.
Samples collected from the LACT unit are called emulsion, and are collected in a plastic container.
ii.
The sample was then transferred into a 100 ml test tube, and toluene was added to act as a de-emulsifier.
iii.
The sample was transferred into a centrifuge where it was spun at about 3000 rev/min for 5 minutes, in order to separate the oil and water content.
iv. v. vi.
The final separated sample is shown in Figure 3.3 The water and oil percentage were respectively recorded. He sample was filtrated using a filter paper and the volume of the sand residue was recorded.
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Figure 3.3: Crude Sample after Centrifugal Action
3.3.2
Method of calculating API gravity of a sample
Before calculating API gravity, we should be able to read the hydrometer. The correct method of reading the hydrometer is illustrated in Figures 3.4a and 3.4b. the sample of oil is placed in a clear glass jar of cylinder and the hydrometer carefully immersed in it to a point slightly below that to which it naturally sinks and is then allowed to float freely. The reading should not be taken until the oil and the hydrometer are free from air bubbles and are at rest. In taking the reading, the eye should be placed slightly below the plane of the surface of the oil (Figure 3.4a) and then raised slowly until this surface becomes a straight line (Figure 3.4b). the point at which this line cuts the hydrometer scale should be taken as the reading of the instrument (Figure 3.4b).
Procedure involved in calculating API gravity of a sample are summarised as follows: i. ii.
Samples were collected hourly from the LACT unit. Each sample is emptied into a measuring cylinder, and hydrometer is placed into said cylinder. (Figure 3.5a).
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iii.
When the hydrometer becomes stable in the liquid, the API gravity is read from the API scale of the hydrometer, and the temperature is read immediately after removing the hydrometer from the sample (as shown in Figure 3.5b).
iv.
In reading the temperature scale accurately care must be taken that the line of sight is perpendicular to the thermometer scale in orfer to avoid parallax.
Figure 3.4a
Figure 3.4b
(Method of Reading the Hydrometer)
`
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Figure 3.5a: Hydrometer Inside Crude Oil
Figure 3.5b: Reading Temperature from the Hydrometer
v.
3.3.3
The specific gravity of the sample can be calculated using the formula below:
= (141.5 )− 131.5
Method of Correcting Observed API using National Standard Petroleum Oil Tables
The result gotten from calculating the API is called the observed API value because it is gotten at an observed temperature which is not the standard temperature: 60 degrees Fahrenheit. The aim of achieving the corrected API is to calculate the API value at 60 degrees Fahrenheit. In other to calculate the corrected API value, the use of National Standard Petroleum Oil Tables is required.
3.4 Crude Oil Skimming Crude oil skimming is a secondary method of reducing water after separation is done. I was stationed at the skim pit present at the OML 98 flow station. Main work carried out here involved monitoring the skimming of crude oil. 23
Skimming is a process of removing of crude from a mixture of oil and water by pumping more water into the pit, causing the oil to float above the mixture and gradually leave the surface (skimmed). The skim pit is shown in Figure 3.6.
Figure 3.6: Crude oil Skim Pit
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CHAPTER FOUR EXPERIENCE GAINED AND CHALLENGES ENCOUNTERED 4.1 Experience Gained Having gone through the industrial training, the following are the experiences gained during the course of the program: i.
Gained knowledge of the operating principle of gravity separators, the separation techniques and control system employed in monitoring these operations.
ii.
Ability to perform basic sediment and water (BS&W) analysis of crude oil samples.
iii.
Ability to calculate API gravity of crude oil samples.
iv.
Gained an understanding of oil metering and calculation of oil production in barrels
v.
Achieved quality competence and behaviour in the site regarding safety rules and the application of them.
4.2 Challenges Encountered The following challenges were encountered during the program: i.
More time was spent learning the theoretical aspect of the work, instead of gaining first hand practical experience on the field.
ii.
There was no adequate planning by the company to include interns in the day-to-day site activities that would have provided the necessary work experience.
iii.
It was difficult to adapt to the site environment.
iv.
Due to short amount of time spent on site, the interns were not given detailed exposure and explanation of site operations, but were merely given a general overview of site operations.
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CHAPTER FIVE CONCLUSION AND RECOMMENDATIONS 5.1 Conclusion Following the successful completion of the SIWES program, the following conclusion were drawn: i.
The program provided an avenue to acquire hands-on experience with sensors and electrical components.
ii.
It provided good opportunity to apply their educational knowledge in real world situations there by bridging the gap between theory and practical.
iii.
It provided good opportunity to apply their educational knowledge in real world situations there by bridging the gap between theory and practical.
iv.
It also created an opportunity for social interaction with different categories of students in different institutions thereby encouraging everlasting friendship.
v.
Finally, it is a good training ground for future challenges.
5.2 Recommendations Having gone through the six months industrial training, the following are suggestions to improve the effectiveness of SIWES: i.
The school should provide adequate exposure to real work situations as backups for theoretical work so students will not be strangers to work situations during the program.
ii.
School should aid in finding IT placement for students in relation to their field specialization.
iii.
Government should endeavour to improve business relationships with companies that employ interns, as a way of adding importance to the scheme, in reality.
iv.
Students or trainees should learn to comport themselves well in these companies so as not to send a bad signal which may discourage such companies from accepting future interns. 26
REFERNCES Butterfly Valve. Available at https://www.forbesmarshall.com/fm_micro/news_room.aspx?Id=seg&nid=145 21/09/2017 Check valve. Available at https://www.usplastic.com/catalog/item.aspx?itemid=85515&catid=489. Retrieved on 21/09/2017. Gate valve. Available at http://www.stoneleigh-eng.com/knifevalve.html. Retrieved on 21/09/2017 Håvard Devold, (2009). Oil and gas production handbook. Oslo: ABB, pp.5-6. ITF (2003). Students Industrial Work-Experience Scheme in Human Resource Development in Nigeria. Industrial Training Fund, Jos Nigeria. National Standard Petroleum Oil Tables produced by National Bureau of Standards approved by American Petroleum Institute (March 4, 1936). Oklahoma State, Marginal Well Commission, Pumper’s Manual. Available at http://www.marginalwells.com/MWC/pumper_manual.htm. Retrieved on 16/09/2017. Sampling analysis of crude oil. Available at http://setxind.com/upstream/the-important-role-lactunits-perform-in-the-petroleum-industry/ Retrieved on 16/09/2017. Schlumberger Oilfield Glossary. Available at http://www.glossary.oilfield.slb.com/ Retrieved on 20/09/2017. The Story of Oil in Pennsylvania. Available at http://www.priweb.org/ed/pgws/history/pennyslvania/pennsylvania.html. Retrieved on 16/09/2017. US department of energy. Available at http://www.doe.gov/ Retrieved on 18/09/2017. US geological survey. Available at http://www.usgs.gov/ Retrieved on 18/09/2017.
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