Preliminary Reservoir Model MC252
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Transcript of Preliminary Reservoir Model MC252
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Preliminary Reservoir Model MC252
6-July-2010
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DRAFT
Outline
• Modelling approach & purpose
• Input Data & Model
− Rock & Fluid Properties
− Layering
− Aquifer Support
• Results
• Impact on “tubing head” pressure
• Conclusions & Future Directions
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DRAFT
Model Approach & Purpose
• Model constructed to address impact of crossflow of M57B & M56A gas sands during “top kill”
− Response of observed pressures
− GOR variation with time
• Request to investigate whether depletion was consistent with known pressures below BOP
• Requested to avoid making any conclusions regarding likely rates
− Role of flowrate investigation team
• Approach
− Simple: tight timing, multiple unknowns
− Single layer per reservoir (M57B to M56F, with intervening shales)
− 10 x 12 x 17; no structure
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DRAFT
Input Data
• Data provided by GoMx Reservoir Team
• Rock Properties
− Developed from MC252 logs
− Permeability
− 275 mD in main M56E sand
− 397 mD in M56A gas/oil sand (only 2.5’)
− 86 – 110 mD in other oil sands
− Compressibility:
− Cr: 6 x10-6 psia-1
− Cw: 3 x10-6 psia-1
− Cf: ~13 x10-6 psia-1
− Fluid properties generated by EoS; volatile, near critical fluid
• tubing performance matched to GAP / Prosper work of T. Liao, A. Chitale & M Gokdemir
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DRAFT
Macondo
M56 Sand Fairway
Net Sand Thickness, ft.
Porosity, %
Aquifer Size
44 13 1.5x44 17 2.0x66 17 2.9x
9500 acre Aquifer
Net Sand Thickness, ft.
Porosity, %
Aquifer Size
44 13 1.9x44 17 2.5x66 17 3.7x
12400 acre Aquifer
9500 acres
2900 acres
9500 acres
2900 acres
Macondo RF – Aquifer Size
Largest Aquifer Size – used as base case (will minimise depletion)
Oil Accumulation110 mmstb = 258 mmrb
Aquifer = 992 mmrb
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DRAFT
Depletion at Various Offtake Rates
04/20/2010 04/30/2010 05/10/2010 05/20/2010 05/30/2010 06/09/2010 06/19/2010 06/29/2010 07/09/2010 07/19/2010 07/29/2010 08/08/2010 08/18/2010 08/28/201010600
10800
11000
11200
11400
11600
11800
12000
(PS
IA)
PAVH
PAVH M56E GoMReview25 PAVH M56E GoMReview35 PAVH M56E GoMReview50 PAVH M56E GoMReview60 PAVH M56E GoMReview70
• Base Model 3.8x Aquifer• Skin = 10, except at 70 mbd• From 20-April to 1-July• Pressure increase from Aquifer influx
M56E Main Oil Sand
25 mbd
35 mbd
50 mbd
60 mbd
70 mbd
initial pressure
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DRAFT
Impact of Aquifer Size
04/20/2010 04/30/2010 05/10/2010 05/20/2010 05/30/2010 06/09/2010 06/19/2010 06/29/2010 07/09/2010 07/19/2010 07/29/201010400
10600
10800
11000
11200
11400
11600
11800
12000
AV
ER
AG
E P
RE
SS
UR
E (
WT
BY
HC
PV
) (P
SIA
)
PAVH
PAVH M56E GoMReview35 PAVH M56E GoMReview35x0_GoMReview35x0
• 35 mbd Case
• No aquifer depletes additional 800 psi
• Larger impact with higher flowrates
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DRAFT
Depletion Response @wellbore
• PIE gives similar results to VIP− Constant compressibility (too low)− Single phase
• Pwf drops ~8 psi/day (for 35mbd case)
• Lack of observed depletion could be due to fixed seafloor pressure and large orifice
Macondo M1 Shut-In
0. 500. 1000. 1500. 2000.
-100
00.
1000
0.30
000.
Time (hours)
rat
es S
TB
/D
Macondo M1 Shut-In
0. 500. 1000. 1500. 2000.
4000
.60
00.
8000
.10
000.
pres
sure
PS
I
2010/07/12-1800 : OIL
skin=10
skin=20
skin=30Pwh=4,100 psi
Min. Head
Possible Impactof Seafloor Orifice
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
4,000 5,000 6,000 7,000 8,000
Flowing BH Pressure
Dep
th, f
tTV
Dss
Sea = 2270 psi + P
max P=1,340
BOP P=10 psi
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DRAFT
Conclusions
• Actual reservoir depletion dependent on:
− Flowrate
− Oil column size
− Aquifer
• Limited depletion observed in wellhead could be controlled by non-reservoir mechanisms
− Large orifice
− Flowpath / choke between BOP & reservoir
− Broken gauge
− Crossflow
• Largest uncertainties: flowrate and pressure drop
BOP
LMRP
2270 psiambient
4365 psi6/26/10
M5611850 psiinitial pressure
Containment Cap
M57 Gas Sand
18” ShoeM110 Sand
expected crossflow
crossflow with rupture disk failure
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DRAFT
Back-Up
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DRAFT
Difference between Aquifer & H/C Pressure
04/20/2010 04/30/2010 05/10/2010 05/20/2010 05/30/2010 06/09/2010 06/19/2010 06/29/2010 07/09/2010 07/19/2010 07/29/2010 08/08/2010 08/18/2010 08/28/201011200
11300
11400
11500
11600
11700
11800
11900
(PS
IA)
GoMReview35 PAVH PAVT
This line includes the aquifer
This line is only the hydrocarbon
PAVH M56E PAVT M56E
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DRAFT
Match to “Tubing Performance”
• Flowpath is a major (priniciple?) source of THP uncertainty
• Various cases considered:
− Annular flow
− Casing flow
− Annular + casing flow
• VIP wellbore modelling capability limited in comparison with Prosper / Gap
− Matched lift with simple tubing string
− Equivalent diameter & roughness
Match to Prosper
2900
3100
3300
3500
3700
3900
4100
4300
0 10000 20000 30000 40000 50000 60000
Flow Rate, stb/dP
res
su
re D
rop
in
Tu
bin
g
Tony
VIP
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DRAFT
Influences on Observable Shut-In Pressure
High Wellhead Pressure
• Limited crossflow
• Well integrity above 18” shoe
− small leak into small zone
• Large aquifer
• Lower production (higher skin)
Low Wellhead Pressure
• Integrity failure (crossflow into M110)
• Smaller aquifer
• Higher production (& lower skin)
At Shut-In
Rising THP
• Fluid Segregation
− Only if Pthp < 6,650psia
− Increase would begin at low rates or at flow cessation
• Reservoir Response (radius of investigation)
− Aquifer size will influence Pfinal
• Cessation of crossflow (pressure equilibration)
Falling THP
• Wellbore temperature equilibration (cooling)
• Large leak with limited inflow
After Shut-In
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DRAFT
MBal Results for Various Aquifers
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Key Conclusions wrt SIWHP
BOP
LMRP
2270 psiambient
4365 psi6/26/10
M5611850 psiinitial pressure
Containment Cap
M57 Gas Sand
18” ShoeM110 Sand
expected crossflow
crossflow with rupture disk failure
Can we detect this scenario?
• Leak off will not be detectable (constant charge from M56)
• Crossflow at 18” shoe would be detectable if “large enough”
• Max Qo through 6 disks: 6000 bpd
• Would manifest itself as a lower than “anticipated” SI BOP pressure
• Uncertainty in SI BOP pressure is driven by aquifer & rate
• Impact of crossflow:• Reservoir fluid fills the M110,
charging it above fracture capacity• Possible broach to surface
• M110 sand is small (5’ thick), in one scenario could fill to fracture pressure in 10 days (resvr flow > 32mbd).