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

• Improve hydrocarbon reserve

• Summary

N

W

E

S

Outline

• Harsher environments classification

• Challenges in HPHT field

• Kristin field overview

• Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve

• Summary

Field with high/extreme/ultra “P/T”

Mobile Bay

East Lost Hill

Norphlet

Thunder Horse

Thomasville

Gleneig

Shearwater Triassic

Tuscaloosa West Elgin

Ceuta

Elgin

Franklin

Trecate

Shearwater

Block C,D,E

Malossa

Erskine

Tengiz

Block 823

Crathes

22/25a

Eugene Island

Heron

Egret Appleton

Kessog

Statoil

Puffin

Brae

others

Rhum

Jade

Kingfisher Kvitebjørn

Beinn

GF g

Mary Ann

McLean

Singa Fandango

Mallard

Cook

Lille Frigg

Halley

Devenick

Braemar Huldra

Marnock

Lacq

North Ossum

Kotelnevsko

Arun

Smørbukk

Gyda

Ula

Smørbukk sør

Ekofisk

Tyrihans

Morvin

Judy

Trestakk

100

120

140

160

180

200

220

240

300 400 500 600 700 800 900 1000 1100 1200 1300 1400

Pressure (bar)

Te

mp

era

ture

(d

eg

C)

Kristin

Why do we need to develop field in harsher environment?

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

Outline

• Harsher environments classification

• Challenges in HPHT field

• Kristin field overview

• Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve

• Summary

Challenges in HPHT field

Drilling

Completion

Seal & Barriers

Wellbore integrity

Logging

Core measurement

reliability

Downhole equipment

Reliability & durability

Extending Well life

Pressure depletion Sand Production

Scale precipitation

Workover

Stimulation

Fluids blockage

Outline

• Harsher environments classification

• Challenges in HPHT field

• Kristin field overview

• Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve

• Summary

Kristin field overview • Offshore field: Kristin

• Location: Norway

• Hydrocarbon: Gas Condensate

• 25 x 5 Km

• Water depth: 350 m

7°00'

65°00'

65°15'

64°45'

6506/11

6

Smørbukk

Kristin

6406/2

Erlend1

6°20' 6°40' 7°00'

6°20' 6°40'

3

5

2

4

6

7Lavrans

PL199

Fig.1

5A

Ragnfrid S

PL134B

Morvin

PL257

2

1

3

6A

Ragnfrid N

D-Prospect

F-Prospect

N

M

W E

Kristin SEMI

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

Fluids PVT • 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

Reservoir

initial condition

«Kristin phase envelope»

Outline

• Harsher environments classification

• Challenges in HPHT field

• Kristin field overview

• Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve

• Summary

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)

PDO: Plan for Development & Operation (2001)

PDO PDO PDO

Measured Measured

Measured

Garn Fm. Ile Fm. Tofte Fm.

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

Rapid pressure decline (2/2)

PDO: Plan for Development & Operation (2001)

Kristin Gas Production

[Sm3/d]

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

16000000

18000000

01.01.2005 28.09.2007 24.06.2010 20.03.2013 15.12.2015 10.09.2018 06.06.2021 02.03.2024 27.11.2026 23.08.2029 19.05.2032

Current Model with HM

PDO Model

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

Action:

Build a reliable model

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)

Producer

1

2

3

Hydrocarbon fluids near wellbore area (below

dew point):

1. ~Mobile Gas, Mobile Condensate

2. Mobile Gas, Condensate buildup

3. Mobile Gas

Perforated

interval

• Condensate accumulates near wellbore area up to reach the critical saturation

allowing fluid to be mobile phase

• Relative permeability to gas drop during production;

Fluids banking (2/2)

Sr

rB

HKKPI

w

e

rabs

ln..

..

• Relative permeability to gas

drop during production due to

reduction of gas saturation;

• 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

Action:

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

stable and safe condition

• Start investigation on the leakage location

• Schedule an intervention plan (LWI) to restore the

barrier by setting a retrievable plug

• Define a plan to re-complete the well if NPV

still positive

WHP

Annulus

Pressure

~ 90 bar

XOV

operated

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

Outline

• Harsher environments classification

• Challenges in HPHT field

• Kristin field overview

• Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve

• Summary

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)

Improve hydrocarbon reserve

Outline

• Harsher environments classification

• Challenges in HPHT field

• Kristin field overview

• Challenges & remedial actions in Kristin

• Improve hydrocarbon reserve

• Summary

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

mkfo@statoil.com www.statoil.com