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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