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Transcript of Understanding Waterflood Behavior and EOR - connectivity...Understanding Waterflood Behavior, ......
Connectivity Analysis; Understanding Waterflood Behavior,
Connectivity for EOR Analysis
Richard Baker
September-2012
Jackson Hole Wyoming
Outline
• Executive Summary
• Background/What are we trying to do?
• Target Identification (communication analysis)
• Controlling “hot streak” flow
• Conclusions
Executive Summary I
• Examination of 12 waterflooded fields and over 2000
injector-producer pairs (1400 well pairs in sandstones)
– We studied the nature of heterogeneity between wells using
communication analysis (connectivity analysis)
• Flow in these waterflooded fields is controlled by two
components;
– Waterflood Induced Fractures
– Matrix controlled flow
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Results of communication analysis work
(connectivity);
• Stress orientation western Canada
– controlling flow is typically NE-SW
– Examining the early water breakthrough plots and injectivity
analysis indicates the presence of fracture flow at early
times
• At late times, good reservoir management and shear
failure often mitigates the effect of on trend fractures
• Waterflood Induced Fracture (Geomechanics) is important
factor controlling flow
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BACKGROUND/WHAT ARE WE
TRYING TO DO?
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EOR selection Typically select on fluid type, lithology
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Waterflood
Gas flood CO2
Chemical flooding
Understand how fluids flow
in reservoir
What are we trying to do? The need to
differentiate these two cases is critical
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Fracture or small
volume hot streak
Khot streak>>
Kmatrix (50 times)
Matrix dominated flow +
Large volume in hot streak
Khot streak>
Kmatrix (2-10 times)
Why???
8 © 2012 Baker Hughes Incorporated. All Rights Reserved.
Fracture or small
volume hot streak
Khot streak>>
Kmatrix (50 times)
Matrix dominated flow +
Large volume in hot streak
Khot streak>
Kmatrix (2-10 times)
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http://www.worldatlas.com/webimage/
countrys/na.htm
Figure 1: North American Stress Orientation Map18
(stars ae field locations annotated by authors)
WHAT ARE WE DOING?
• Study of 1400 well pairs in sandstone in Western Canada
(waterflooded) 2000 pairs in total
• Connectivity or communication analysis
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• General experience in
North America is that
induced Waterflood
Fractures control flow
more than we think
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Objectives of Work
• . A key question though is; what type of heterogeneity
controls flow? Is it matrix flow, induced hydraulic fracture
flow or both?
SPE 161177
Analysis of Flow and the Presence of Fractures and Hot Streaks in Waterflood Field Cases
Richard Baker, Tim Stephenson, Crystal Lok, Predrag Radovic, Robert Jobling, Cameron McBurney,
• How can we control injected fluid if we have a
combination of induced hydraulic fractures + matrix flow?
WHAT ARE WE DOING?
CONNECTIVITY/
COMMUNICATION ANALYSIS
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What are we doing?
Figure 18: Types of Communication Strengths
Map view
1 2
3
What are we doing?
15
Light blue water injection rates
Dark blue water production rates
Green Oil rates
How do we use production data
to determine pathways?
Example of Watercut map used as
surveillance data from Beliveau SPE Time (days)
Short term data
long term data
Objective of Communication Analysis
Map of communicating well pairs
We want to identify key wells that communicate
What was done?
• We examine 1400 well pairs in sandstone reservoirs
under waterflood in WCSB using communication analysis
method
Figure 1: North American Stress Orientation Map18
(stars are field locations annotated by authors)
Five waterfloods in non
fractured high permeability
Sandstone reservoirs
Successful waterfloods
None of the waterfloods are
considered to be naturally fractured
Early Waterflood Behavior
• The stress orientation
controlling flow is typically
NE-SW in western
Canada. Examining the
early water breakthrough
plots and the hall plots
indicates the presence of
fracture flow.
Early Waterflood Behavior
• Water
breakthrough
usually occurred in
a on trend
direction (NE-SW)
Water cut
Time
On trend NE-SW
Off trend NE-SW
NW-SE
INJECTOR ANALYSIS
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Monthly Injection Pressures vs. Injection
Rates over Two Year Period; VRR~1
Reservoir Pressure constant Theoretical line
Based on Darcy’s flow constant res. pressure Wellhead
Injection
Pressure
Injection
Rate
Injection Pressures vs. Injection Rates over Two
Year Period; VRR~1 Reservoir Pressure constant
Theoretical line
Based on Darcy’s flow
Banding behavior
@ same ~pressures
(3000-4000 Kpa)
Fracture
pressure
~ 4 300 KPA
(0.75-0.43) psi/ft
x600 m KB
Injection
Rate
Hall Plot; Evidence of Induced Fractures
Injection pressure Injection rate
Injection rate drops by ½ but
injection pressure is constant
Hall integral
Entire Field Late Stage Analysis
1 mile
Early stage waterflood (NE/SW)
Zoom in Portion of Field
1 mile
What has happened?
Partial conversion to line drive
but also
Communication is now East- West
Rose Diagram of Entire Fields Connectivity
The rose plots generated by the communication analysis tool
indicate no preferential flow direction in late stage waterfloods,
this indicates; 1) matrix flow and/or 2) shear failure fractures.
What is happening???? Early Stages; Map
View
Off trend well
On trend well
NE-SW Good initial
response
Water cut rise
first
What is happening???? Early Stages; Map
View
Off trend well
On trend well
NE-SW
• Watered out
Or
• injector
Water movement initially
NE-SW
What is happening???? Late Stage Waterflood;
Map View
Off trend well
On trend well
NE-SW
• Watered out
Or
• injector
On trend well
NE-SW
• Watered out
Or
• injector
Growth in
fractures
Mental Model Check
Injection pressure constant (2-3 times injection rates)
Initial communication in stress direction; NE-SW (on
trend)
Late stage communication in off trend direction
Either simple matrix flow
Or
– Shear fractures (constant wellhead injection pressure)
Probably both
Recap Targeting Study
• In 10-50% of the wells we see strong communication
between individual injectors and producer probably via
fractures
• Flow in these waterflooded fields is controlled by two
components;
– Fracture and/or high permeability matrix flow (hot streaks)
– Matrix controlled flow
So what can we do with this
knowledge?
Decrease injection pressures
Change producer into injectors
(streamline patterns)
Gel treatment/Polymer
SIMULATION STUDY
SASKATCHEWAN
Sandstone
thickness=3-4 M
μoil~350cP
μ polymer=7cP
API ~13
HISTORY MATCHED ~90 WELLS ON WATERFLOOD
Field BC
Perm=15 D
Perm=1 mD
Waterflood Polymer 20% Slug Polymer Gel
Oil Production non rate control
Method Incremental
RF
Ultimate RF
Waterflood 27%
Polymer Flood 5 32%
Gel Treatment 3 30%
Gel Treatment w/
Polymer Flood
11 38%
0
5
10
15
20
25
30
35
40
waterfloodalone
polymer floodalone
gel alone polymer flood+gel
Series 1
Series 1
Comparison of
Communication
Analysis with
Waterflood Case
(Blind test)
Conclusions
• Flow in these waterflooded fields is controlled by two components;
– Waterflood Hydraulic Induced Fractures (not NFR)
– Matrix
• Examining the early water breakthrough plots and injection pressures
and rates indicates the presence of fracture flow at early times
– Pinj≈ Pfrac extension
• At late times, good reservoir management and shear failure fracture
often mitigates the effect of on trend fractures
c
Background references
• Richard Baker, Tim Stephenson, Crystal Lok, Predrag Radovic, Robert
Jobling, Cameron McBurney; “Analysis of Flow and the Presence of Fractures
and Hot Streaks in Waterflood Field Cases”
• Heffer, K., Zhang, X., Koutsabeloulis, N., Main, I., Li, L., “Identification of
Activated (Therefore Potentially Conductive) Faults and Fractures Through
Statistical Correlations in Production and Injection Rates and Coupled Flow –
Geomechanical Modelling,” presented at SPE Europe Annual Conference
and Exhibition held in London, United Kingdom, 11-14 June 2007.
• Heffer, K., Greenhough, J., Main, I.G., Zhang, X., Hussein, A.M.,
Koutsabeloulis, N., “Low-cost Monitoring of Inter-well Reservoir
Communication Paths Through Correlations in Well Rate Fluctuations: Case
Studies From Mature Fields in the North Sea,” presented at SPE
Europec/EAGE Annual Conference and Exhibition held in Barcelona, Spain,
14-17 June 2010
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