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TRANSCRIPT
Panteha Ghahri
Guillaume Berthereau
Estimated Fluid Contact Using Material Balance Technique &
Volumetric Calculation Improves Reservoir Management Plan
1
• Objective
• Gryphon Reservoir-Overview
• The proposed approach(Material Balance
Modelling & Volumetric Calculation)
• Comparison the calculated fluid contacts with
4D seismic and simulation model
2
Outline
• Estimate WOC & GOC for Gryphon area using
an analytical approach
• Direct measurement of the fluid contacts is costly and sometimes can be very challenging.
• It is also useful to validate the simulation model
3
Objective
•Production started from 1993
•Original oil column 190 ft
•Heavy Oil (21 deg API) Viscous oil (6 cP)
•Long tail end production at high watercut
•Long term plan to produce across a floating facility (first permanently moored FPSO)
•Developed exclusively with horizontal production wells
•Aquifer well to provide compatible injection water/large connected aquifer
•Water & gas much more mobile than the oil in the reservoir
4
Gryphon reservoir overview
Gas+ Oil Production Gas Injection
Aquifer Influx + Water Injection
Very Limited/Aquifer
Index
WOC
GOC
WOC
GOC
The Original Oil Rim Thickness
Gas+ Oil Production
(Gas Movement)
Moved GOC
Moved WOC Moved GOC
Moved WOC
5
Material balance modelling Gryphon and nearby field
6
Material balance & volumetric calculation
Gas, 1-Swi
Oil, 1-Swi
Water
Water, Sor
Oil, 1-Swi
Oil, 1-Swi-Sgr
Gas, 1-Swi
Initial Current
7
Material balance & volumetric calculation
•Material Balance Calculation • Oil Produced: 121 MMbbl
• Oil left inside the water zone:14% of STOIIP
• Oil moved up to Gas zone:10% of STOIIP
• Remaining Oil: 47% of STOIIP
8
WOC & GOC vs. Time
5200
5300
5400
5500
5600
5700
5000 5500 6000 6500 7000 7500 8000 8500 9000
Co
mp
leti
on
Inte
rva
l o
f w
ells
(T
VD
ss
)
WOC-1993
WOC-2011
Data from last test:GOR =402
WOR=89%PI=178
GOC-2011GOC-1993
9
Well position vs. WOC & GOC
W1
W2
10
Completion interval vs. WOC & GOC and WOR%
11
Completion interval vs. WOC & GOC and GOR
• The strategy is to keep the existing wells placed within the
oil rim by controlling the movements of the GOC & WOC.
• The WOC movements are controlled by re-injecting produced water
into the aquifer or the reservoir.
• The GOC movements are controlled by re-injecting the gas into the
gas cap and operating the wells at a GOR limit.
• Well performance data, 4D seismic, simulation modelling and
analytical calculation are used to monitor contact movements. This
understanding is applied to optimize new well placements.
12
Reservoir management strategies
4D modelling
Shale
Shale
Gas bearing Sand
Oil bearing Sand
Brine bearing Sand
(1990) Acoustic impedance (2011)
No signal in shale
No signal in shale
2011-1990
syn
theti
c
Co
lou
red
in
versio
n
• 4D observed theoretically only due to fluid movement (no significant pressure change)
• Fluid movements over Gryphon: • Gas into oil (due to production): softening • Water into oil (due to production): hardening • Oil into gas (water injection): hardening
Aco
usti
c im
ped
an
ce
Hard
enin
g
Soft
enin
g
4D (2011-1990): seismic Sum +ve amplitude
2011-1990 (CI Full stack) oGOC / oOWC
Hardening
Polygon used for initial STOIIP calculation
• Polygon used to calculate
STOIIP, input to material
balance
• 4D showing water movement
into the oil leg due to:
• production
• water injection
4D (2011-1990): seismic / simulation model Sum +ve amplitude
2011-1990 (CI Full stack) oGOC / oOWC
Column height (water in oil leg)
2011-1990
Hardening
Polygon used for initial STOIIP calculation
• Decent qualitative match
between simulation model and
4D seismic
4D and fluid sections
Hard
enin
g
Soft
enin
g
oGOC
oOWC
Moved OWC
HC
• Generally reasonable quantitative match between moved OWC from the simulation model
and 4D seismic
Moved contact comparison: material balance and simulation model
Original Simulation model* Material balance
GOC 5541 5514 (Sgas90%) , 5518 (Sgas70%) 5519
OWC 5731 5638 - 5545 5631
* Average of the moved OWC given by the simulation model
• Very similar moved GOC from simulation model and material balance (error within vertical resolution)
• The moved OWC between simulation model
and material balance are in alignment.
Moved OWC (Sim. model)
Multi-scale injectites
5619.00’ 5622.00’ 5625.00’ 5628.00’
5628.00’ 5631.00’ 5622.00’ 5625.00’
DYKE
DYKE INJECTION BRECCIA
DYKE
Feeder dyke system
DYKE
Stepped discordant
base
July 2, 2013
• Remobilisation of the turbidites sandstone in early Frigg times
• Creation of multi scale (from core to seismic scale) injection wings
• Below seismic resolution injectites may account for a significant volume, more than expected
T Sele
T Balder
Adapted from Hurst and Cartwright
• Water and gas oil contacts has been calculated using material balance and
volumetric calculation
• Contacts from material balance were compared with those observed from the
simulation model:
• Moved OWC from the simulation reasonably matches 4D
• Moved OWC from material balance and simulation model are in alignment
• The difference is possibly associated to missing sand volume unresolved by
seismic (below seismic resolution injectites)
• Material balance can be used, in addition to well performance evaluation, 4D
seismic and simulation modelling, to monitor the contact movements
effectively. Results can be used to control well operations and placement of
new wells.
19
Conclusion
• The authors would like to thank the partner
Sojitz for its approval to present this work.
•We also would like to thanks our colleges who
support us during this study, Steve Milner,
Hope Okhuoya, Miguel Orta, David Kirby,
Duncan Chedburn, Doug Smith, Tim Heijen
and Fabrizio Conti.
20
Acknowledgment