Transcript Presalt Hydrocarbon Systems Project overview / Status Update

Upstream Research
Recognizing Reservoir Compartments on
Geologic and Production Timescales in DeepWater Reservoirs: An Example from Genesis
Field, Gulf of Mexico
M. L. Sweet and L. T. Sumpter
ExxonMobil Upstream Research Co.
M.L. Sweet Lafayette Geological Society
Outline
• What is Connectivity?
• Genesis Field Background
• Observations of Pre-Production Fluid
Contacts
• Production Timescale Pressure Changes
• Conclusions
M.L. Sweet Lafayette Geological Society
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What is Connectivity?
•
Common fluid contacts and /or pressure gradients


•
King (1990)
Ainsworth (2005)
Continuity between injectors and producers – waterflood
sweep efficiency

•
Smalley and Hale (1996)
Vrolijk et al. (2005)
Sand to sand connection in geologic models


•
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Stiles and Magruder (1992)
Common hydrocarbon fluid properties

Smalley and Hale (1996)
 The definition of connectivity depends in part on the
timescale of interest
M.L. Sweet Lafayette Geological Society
Geologic Time-Scale Connectivity
•
Describes the pre-production fluid distribution in a field
established over geologic time
 Timescale - tens of thousands to millions of years
•
Compartments can be defined by structural and/or
stratigraphic elements
Structurally Controlled Fluid Contacts
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Stratigraphically Controlled Contact
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Production Timescale Connectivity
•
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Related to changes in fluid contacts and pressure caused by
production
 Short timescale (hours to years)
 Lateral and vertical permeability changes due to fault juxtaposition, low permeability
fault rocks, facies changes and/or diagenesis
•
Need to integrate surveillance data (down-hole pressure gauges,
4D seismic, production logging) with geologic interpretation.
8,000
0 psi draw-down
350 psi draw-down
7,000
Pressure (psi)
6,000
Pressure builds up
after the well was shut-in
5,000
4,000
`
3,000
A14 Max SIBHP
A3 Max SIBHP
2,000
A5 Max SIBHP
1,000
01/04
11/03
09/03
07/03
05/03
02/03
12/02
10/02
08/02
06/02
04/02
02/02
12/01
M.L. Sweet Lafayette Geological Society
10/01
08/01
06/01
04/01
02/01
12/00
10/00
08/00
06/00
04/00
02/00
12/99
10/99
08/99
06/99
04/99
02/99
Time
Genesis Field – Background
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Field Background
N
• Deepwater Gulf of Mexico - 2600 ft water depth
• Green Canyon Block 160, 161, and 205
• Discovered 1988, operated by Chevron
• Production started November, 1999
Genesis Field
• 25 wells and sidetracks, 3D seismic
SCHEMATIC
CROSS SECTION
• Down-hole
pressure
gauges in most production wells
WEST
EAST
205 #1
Geologic Background
• 20-25east dip
• 1,300’ oil column
• 24-40API gravity
• Depth: 12,000’-15,000’
NEB 1
• Three-way structure against salt in a mini-basin
NEB 2
• Pleistocene-age, deepwater sands
NEB 3U
• Neb reservoirs main production targets
NEB 3
• Vertical and lateral variability of sand content
• Several small throw faults cut the reservoir
1000’
Compartmentalization is primarily a
14,200
SCALE:
14,800
TD: 15,146’
function of stratigraphic complexity
1000’
M.L. Sweet Lafayette Geological Society
Neb 3 Reservoir
Neb 3 well log cross-section
•
Patchy amplitude pattern and abrupt
lateral thickness and facies changes
 Greater compartmentalization?
•
Erosion at base of Neb 3
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Neb 3 Amplitudes on Neb 3 structure
Neb 3 Environment of Deposition
Core Photographs from Neb 3
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•
Abundant rip-up clasts and amalgamated,
massive sand beds (Ta)
•
Thick blocky sand change laterally into
thinner laminated sands
•
Abrupt lateral thickness changes
•
Erosion at base of Neb 3
Tb
Ripups
Ta
Neb 3 is the deposits of a laterally and
vertically amalgamated, erosionallyconfined channel complex
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Outcrop of An Erosionally Confined Deepwater
Channel-Complex
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Capistrano Formation near San Clemente, CA
Channel-fill sandstones
Overbank mudstones
From Mike Farrell ExxonMobil Research Co.
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Neb 3 Pre-Production Connectivity
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Pressure–Depth Plot From RFT
11800
Oil Gradient = 0.31 psi/ft
161-1st2 Neb 3
True Vertical Depth Subsea (ft)
161-1st3 Neb 3
12300
161-1 Neb 3
Neb 4 falls on Neb 3 oil line
160-1 Neb 3
A2 drilled prior to production,
no movement
205-1 Neb 3
12800
205-3 Neb 3
161-1st3 Neb 3
test
13290 ft OWC
13300
205-A2 Neb 3
205-3 Neb 4
13800
Water Gradient = 0.5 psi/ft
7800
7900
8000
8100
8200
8300
8400
8500
8600
8700
8800
8900
9000
Pressure (psig)
Common oil-water contact, oil and
aquifer gradients = one pre-production
compartment
Neb 3 Top Structure Map
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Neb 3 Production Time-Scale Connectivity
Down-hole pressure
9,000
Each new well falls on pressure
decline trend of the earlier wells
8,500
8,000
A3 - 550 psi drawn-down
7,500
A4 - 550 psi drawn-down
7,000
Pressure (psi)
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6,500
Wells watered out as aquifer
moved up-dip
A12st2 - 1500 psi drawn-down
6,000
A1st3 - 2400 psi drawn-down
5,500
5,000
4,500
A2 Max SIBHP
4,000
A3 Max SIBHP
3,500
A4 Max SIBHP
3,000
A1st3 Max SIBHP
2,500
10/03
08/03
06/03
04/03
01/03
11/02
09/02
07/02
05/02
03/02
01/02
11/01
09/01
07/01
05/01
03/01
01/01
11/00
09/00
07/00
05/00
03/00
01/00
11/99
09/99
07/99
05/99
03/99
01/99
Time (month/year)
Well A-2 Production from Neb 3 Reservoir
25
Oil
20
Water
Gas
15
20
15
10
10
5
5
0
0
99 99 99 00 00 00 01 01 01 02 02 02 03 -03 -03
y
n- y- p- n- y- p- n- y- p- n- y- p- np
Ja Ma Se Ja Ma Se Ja Ma Se Ja Ma Se Ja Ma Se
Time
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Gas Rate (MCF/D)
Oil & Water Rate (kB/D)
25
On production time-scales Neb 3
behaved as one reservoir
connected to a common aquifer
Neb 1 Reservoir
Seismic Amplitudes on
Neb 1 Structure Map
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Neb 1 Isopach Map
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Neb 1 Well Log Cross-Section
•
Continuous amplitude pattern, limited
lateral thickness and facies changes
 Greater connectivity?
•
Erosion at base of Neb 3
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Neb 1 Environment of Deposition
Core Photographs from Neb 1
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•
Thinly-interbedded sand and mud with
abundant ripple-laminations (Tc)
•
Thicker wells have barrel-shaped log
motif with suppressed gamma and
resistivity. Thinner well have a sharpbase cleaning-up log motif
•
Conformable base of Neb 1
1 Foot
Tb
Ta
Tc
Neb 1 is the deposits of a
channel-levee complex
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Channel-Levee System Quaternary Amazon Fan
50 m
Levees
HARPs
After Pirmez et. al., 1997
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Neb 1 Pre-Production Connectivity
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Pressure–depth plot from RFT
11800
Oil Gradient 0.31 psi/ft
161-1st2 Neb 1
True Vertical Depth Subsea (ft)
161-1st3 Neb 1
12300
161-1 Neb 1
12800
160-1 Neb 1
205-A2 drilled pre-production
no water movement
12995' OWC in north
205-1 Neb 1
12850' OWC in south
13300
161-1st3 Neb 1
test
205-A2 Neb 1
Water Gradient 0.5 psi/ft
13800
7900
8000
8100
8200
8300
8400
8500
8600
8700
8800
Pressure (psig)
At least two separate oil-water contacts
and oil gradients = two or more preproduction compartments
Top Structure Map on Neb 1
M.L. Sweet Lafayette Geological Society
Neb 1 Production Timescale Connectivity
Down-hole pressure
8,000
0 psi draw-down
•New wells came on production
at or near virgin pressure
350 psi draw-down
7,000
•Some wells (A14) showed
rapid pressure decline
Pressure (psi)
6,000
Pressure builds up
after the well was shut-in
5,000
4,000
•Slower pressure decline in the
A5 well suggests aquifer
support
`
3,000
A14 Max SIBHP
A3 Max SIBHP
2,000
A5 Max SIBHP
1,000
01/04
11/03
09/03
07/03
05/03
02/03
12/02
10/02
08/02
06/02
04/02
02/02
12/01
10/01
08/01
06/01
04/01
02/01
12/00
10/00
08/00
06/00
04/00
02/00
12/99
10/99
08/99
06/99
04/99
02/99
Time
On production time-scales Neb 1 has multiple compartments.
Some of these compartments are connected to the aquifer and
others are not. Seismic and well data suggest that these
compartments form due to poor connection between channelfill and levee deposits.
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Pressure Transient Analysis
A3
A14
A2
A18
Neb 1 Isopach map showing location of channel axis (blue), gamma ray
Logs and 4 well used in pressure-transient analysis (A3, A14, A2 and A18)
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Pressure-Time Plot For Neb 1 Wells
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A2
6000
A18
5000
Pressure [psia]
A3
4000
3000
A14 was shut-in while A2, A18 and A3 were producing. Pressure increase
suggests separate compartment.
2000
A14
5/8/04
5/9/04
5/10/04
5/11/04
5/12/04
Pressure-Time
Plot [psi] vs Time [hr]
Pressure [psia], Pressure/Time
[psi/hr], Pressure
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5/13/04
Well Test Analysis of A14 Data
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A14
Well A14 pressure transient response is best match by the well being in a narrow
channel within a weak connection to a larger volume (levee?)
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Reservoir Architecture of Neb 1 and Neb 3
Well connected
Poorly connected
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Stratigraphic Controls on Reservoir Performance
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Dynamic
Static pressure Pressure
Compartments Compartments
Multiple
Channel/levee
Neb 1
Multiple
Multiplechannels
separated
/baffled from
levees
Multiple
Semi-amalgamated
channels - Neb 2
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Pressure
Depletion
Aquifer
Pressure
Depletion
Aquifer
Single
Amalgamated
channels - Neb 3
Drive
Mechanisms
Single
Aquifer
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Results of Genesis Connectivity Analysis
•
Log and seismic data from the Neb 3 reservoir suggested greater potential for
compartmentalization, however fluid contact and pressure data suggested a
common oil-water contact.
•
Production data has shown a good connectivity on a production timescale
within the Neb 3 oil column and between the oil column and the aquifer.
•
Neb 1 appeared less variable from log and seismic data, however fluid
pressure and contact data suggested multiple compartments. Continuous
monitoring of down-hole pressure showed an even higher degree of
compartmentalization on a production timescale.
•
Neb 3 and Neb 1 have a similar structural style, but were deposited in
different deep-water environments suggesting that stratigraphy is the main
control on connectivity.
–
–
Good connectivity within erosionally confined channel complexes.
Poor connectivity between channels and levees.
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Conclusions
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• Analysis of fluid contacts in the context of a field’s
structural and stratigraphic framework gives an
indication of pre-production compartments that can
have a major impact on development planning and
identification of infill drilling opportunities.
•
With production another level of compartmentalization
may become apparent. Integration of surveillance data
with an understanding of the reservoir geology is
required to define these production timescale
compartments and use this knowledge to guide
reservoir management.
M.L. Sweet Lafayette Geological Society
Acknowledgements
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ExxonMobil and Genesis Field partners Chevron and BHP Billiton gave
permission to present this talk.
Mike Maitland, Cherie Lee and Diane Schwetz (ExxonMobil Production
Co.) for their insights into Genesis Field and for their help in getting
data for this paper released.
Sephir Arbabi and Jane Shyeh (ExxonMobil Research Co.) provided
pressure transient analysis of the Neb1 well test data.
ExxonMobil Research Co. Connectivity Team: Peter Vrolijk, John
Snedden, Amanda Mosola, Chuck Kiven, Sofie Nollet, Ryan
Ruppert, Ellen Meurer and Ilsa Kirsher.
M.L. Sweet Lafayette Geological Society