Kristin HPHT LysarkKfoury2012

Kristin HPHT Gas Condensate Field: challenges, remedial actions & strategy to improve hydrocarbon reserve

Moussa Kfoury NTNU - Trondheim, 24.10.2012

Outline • Harsher environments classification • Challenges in HPHT field

• Kristin field overview • Challenges & remedial actions in Kristin N

• Improve hydrocarbon reserve

E

• Summary W

S


• Kristin field overview • Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve • Summary

Field with high/extreme/ultra “P/T” Why do we need to develop field in harsher environment? 240

Mobile Bay others

Statoil

Temperature (degC)

220

Fandango

Singa

200

Jade

Thomasville

McLean

Franklin Elgin

Shearwater 22/25a Kessog Arun Gyda

160 Ula

Marnock

Smørbukk

Cook

Devenick

Smørbukk sør Tyrihans

GFg

Kvitebjørn

Ceuta Block C,D,E Malossa

Puffin Rhum

Tengiz

Braemar Kingfisher Beinn

Crathes

Lacq Eugene Island

North Ossum

500

Trecate

Egret Kristin

Morvin

Lille Frigg

400

Erskine

Thunder Horse

120

100 300

Heron

Huldra

Kotelnevsko

Ekofisk

Brae Mallard

Halley

Trestakk

140

Appleton

Judy

Norphlet

Tuscaloosa West Elgin Gleneig

Mary Ann

180

East Lost Hill

Shearwater Triassic

Block 823

600

700

800

900

Pressure (bar)

1000

1100

1200

1300

1400

Harsher environments classification The decline of conventional hydrocarbon resources reserves pushed oil and gas industry to drill in unconventional resources as in harsher environments at high pressures and high temperatures (HPHT) Pressure

Temperature

K psi

Bar

°C

°F

High

10-15

689 - 1034

150-180

200-350

Extreme

15-20

1034 - 1379

180-204

350-400

Ultra

20-30

1379 – 2068

204-260

400-500




Challenges in HPHT field Completion

Logging Seal & Barriers

Drilling Stimulation

Wellbore integrity

Workover Extending Well life

Core measurement reliability

Fluids blockage Scale precipitation Sand Production Pressure depletion

Downhole equipment Reliability & durability




Kristin field overview • Offshore field: Kristin 6°20'

• Location: Norway • Hydrocarbon: Gas Condensate

65°15'

6°40'

7°00'

3

• 25 x 5 Km

PL134B 1

• Water depth: 350 m

Morvin

Smørbukk 2 6

6506/11

65°00' 3

Kristin SEMI

Kristin

PL257

PL199

5A

5

N Erlend

M

1 7

W

E

Ragnfrid N

64°45'

6A

6

Ragnfrid S

6°20'

Lavrans 2 4

D-Prospect 6406/2 F-Prospect

6°40'

7°00' Fig.1

Kristin field overview • Discovery Dec 1996 • 3 appraisal wells followed in 1997-1998 • Plan for development and operations (PDO) Nov 2001 • Start of drilling production wells Aug 2003 • Production start-up Nov 2005 • Tyrihans production start Jul 2009 (tie-in to Kristin SEMI) • Expected to produce till 2030-2035 • Early-Middle Jurassic • Reservoir: Sandstone • Formations: Garn, Ile and Tofte

“Fair to poor properties” “Good properties” “Good to fair properties”

Kristin field overview • HPHT (Pr~910 bar, T~170°C) • Saturation pressure (G-I/T)~ 398/422 bar • OGIIP~ 71.5 GSm3 • OCIIP~ 70.3 MSm3 • GOR (G/I/T)~ 856/1092/1436 sm3/sm3

• Pure natural decline driver mechanism • 12 producers (5 commingled Garn/Ile) • The plan is to produce till 2030-2035 • Kristin has produced @Sep. 2012 • 21.5 Gsm3 of Gas (remaining is 12 Gsm3) • 19.1 Msm3 of Oil (remaining is 5.9 Msm3)

?

The main question is:

• How to ensure or even how to improve hydrocarbon reserve?

Facilities & production constraints Facilities • Semisubmersible Platform (Kristin SEMI) • 4 subsea templates with 4 well slots per template • 2 templates with two 10” ID flowlines • 2 templates with only one 10” ID flowline • Separator (well testing)

Production constraints • Flowline: 7 Msm3/d • Kristin SEMI: 18.6 Msm3/d of Gas • Kristin SEMI: 20.0 Ksm3/d of Condensate • Kristin SEMI: 8.0 Ksm3/d of Water

«Kristin phase envelope»

Fluids PVT

Reservoir initial condition

• Once pressure drop below dew point, condensate will start banking near wellbore area • Today, yearly fluid sampling are collected from different flowlines for PVT/allocation purposes and to follow composition evolution along production life of the field (for instance: lean gas development, heavy components left in reservoir)

Tofte

Garn Ile




Challenges in Kristin field There are many daily challenges in Kristin field. This presentation will highlight a piece of some challenges: • Rapid Pressure Decline • Scale Precipitation • Fluids Banking • Sand Production • Seal Loss (Leakage)

Rapid pressure decline (1/2) Garn Fm.

Tofte Fm.

Ile Fm.

PDO

PDO

PDO

Measured Measured

Measured

1. Over-prediction of permeability in Garn due to well bias; 2. Over-prediction of GIIP due to depth conversion uncertainty; 3. Over-prediction of permeability in Tofte Fm. water-leg (well bias); 4. Poor or reduced horizontal/vertical transmissibility;

5. Faults or even sub-fault with low transmissibility; 6. Scale precipitation

PDO: Plan for Development & Operation (2001)

Rapid pressure decline (2/2) Implications: • Yearly production target could not be reached; • Less Proved Developed (PD) & Proved UnDeveloped (PUD) hydrocarbon reserves;

• Challenges to sustain production once pressure drop below saturation pressure; • More problematic to drill new infilling wells in a depleted reservoir Kristin Gas Production [Sm3/d] 18000000 Current Model with HM PDO Model

16000000

Action: Build a reliable model

14000000 12000000 10000000 8000000 6000000 4000000 2000000 0 01.01.2005

28.09.2007

24.06.2010

20.03.2013

15.12.2015

10.09.2018

06.06.2021

PDO: Plan for Development & Operation (2001)

02.03.2024

27.11.2026

23.08.2029

19.05.2032

Scale precipitation (1/3) • Components in the liquid phase come out of solution (precipitation) caused by − chemical reactions

− change in temperature and/or pressure − change in composition of the liquid i.e. change in system equilibrium • Organic (wax, asphaltene, naphtenate) • Inorganic (calcium carbonate, barium sulphate, strontium sulphate, calcium sulphate, iron sulphide, iron oxide, sodium chloride)

Scale precipitation (2/3) What kind of challenging problems could occurred?

• Scale as deposits − Near wellbore formation damage − Reducing flow paths in perforation tunnels, gravel packs − Scale bridges in tubing − Pump failures - ESP motor overheat, seizure of propeller and additional rod loads − Safety valve, choke, other valves operation • Scale particles as in suspension

− Plug filter − Plug formation − Oil & water separation efficiency - OIW

Scale precipitation (3/3)

Restoring gas production after A remedial treatment 

Action: Scale squeeze

Fluids banking (1/2) • Condensate accumulates near wellbore area up to reach the critical saturation allowing fluid to be mobile phase • Relative permeability to gas drop during production; Producer Hydrocarbon fluids near wellbore area (below dew point):

1. ~Mobile Gas, Mobile Condensate 2. Mobile Gas, Condensate buildup 3. Mobile Gas 1 2 3

Perforated interval

Fluids banking (2/2) • Relative permeability to gas drop during production due to reduction of gas saturation;

PI 

Action: • Solvent treatment allows to reach a neutral wettability helping to produce back blocked fluids (condensate + brine from scale treatment) and thus to increase relative permeability to hydrocarbon near wellbore area as well productivity

Kabs.Kr .H  r  .B. ln e  S   rw 

Sand production (1/2) • Sand production is affecting wellbore stability, downhole installation, erosion of tubing, damaging chokes, increasing pressure drop as chocking lines and thus reducing production; • Main challenge is to compute maximum oil/gas rate allowing sand production within certain limits without penalizing field production and without compromising on safety; • Sand production mechanism can be summarized: − Shear failure induced by fluid pressure drawdown; − Tensile failure caused by high hydrocarbon production rates; − High stresses due to completion cause the formation to fail (in compression)

J. Wang et al., Prediction of Volumetric Sand Production and Wellbore Stability Analysis of a Well at Different Completion Schemes, Taurus Reservoir solution Ltd, ARMA/USRMS 05-842, 2005

Sand production (2/2) • Each well contains one acoustic and one erosive sand sensor at the well head downstream the choke. • One acoustic sand sensor is located on each of the 6 flowlines topside. • A sand trap is located on the line from the test manifold for sampling • Yearly sand injection calibration campain (done for 2012)

Action: Monitor sand and choke back well if needed

Different producers in Kristin

Seal loss (1/2) A sudden drop of annulus pressure not sustained even after operating XOV (Cross over valve) indicates a leakage and loss of one barrier • Immediate action is to shut the well and ensure a XOV

stable and safe condition

operated

• Start investigation on the leakage location

WHP

• Schedule an intervention plan (LWI) to restore the barrier by setting a retrievable plug • Define a plan to re-complete the well if NPV ~ 90 bar

still positive

Annulus Pressure

Seal loss (2/2) • Seal loss could be traduced by a build-up or draw down of annulus pressure (reservoir pressure & kind of leakage); • Seal loss impact wellbore stability and integrity; • Seal loss means Workover (recompletion) as production delay (not honoring yearly target);

• Rapid pressure drop in HP reservoir have a major impact on:

− Subsidence; − Rock compaction and thus production reduction (permeability); − Wellbore stability, mainly casing deformation or break (acting on seal), due to increase of horizontal strain as differential displacement




Improve hydrocarbon reserve To sustain or even to improve hydrocarbon reserve, it require: • a good understanding of field/well behavior at mid-long term; • real time monitoring of well behavior and take rapid action to remediate any reduction of production; • avoiding cross-flow or differential depletion • devoloping reliable downhole monitoring system; • extend well life using available stimulation techniques (hydraulic frac, RDS, solvent) • drill new producers in depleted reservoir (to improve drill steering)




Summary • To improve hydrocarbon reserve, many petroleum companies started producing from harsher and unconventional resources

Presentation: Kristin HPHT Gas Condensate Field

Moussa Kfoury, Ph.D [email protected] www.statoil.com

Kristin HPHT LysarkKfoury2012

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