Connectivity Analysis; Understanding Waterflood Behavior, Connectivity for EOR Analysis. Richard Baker September-2012 Jackson Hole Wyoming

Transcription

1 Connectivity Analysis; Understanding Waterflood Behavior, Connectivity for EOR Analysis Richard Baker September-2012 Jackson Hole Wyoming

2 Outline Executive Summary Background/What are we trying to do? Target Identification (communication analysis) Controlling hot streak flow Conclusions

3 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 Baker Hughes Incorporated. All Rights Reserved.

4 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 Baker Hughes Incorporated. All Rights Reserved.

5 BACKGROUND/WHAT ARE WE TRYING TO DO? Baker Hughes Incorporated. All Rights Reserved.

6 EOR selection Typically select on fluid type, lithology Waterflood Gas flood CO2 Chemical flooding Understand how fluids flow in reservoir Baker Hughes Incorporated. All Rights Reserved.

7 What are we trying to do? The need to differentiate these two cases is critical Fracture or small volume hot streak K hot streak >> K matrix (50 times) Matrix dominated flow + Large volume in hot streak K hot streak > K matrix (2-10 times) Baker Hughes Incorporated. All Rights Reserved.

8 Why??? Fracture or small volume hot streak K hot streak >> K matrix (50 times) Matrix dominated flow + Large volume in hot streak K hot streak > K matrix (2-10 times) Baker Hughes Incorporated. All Rights Reserved.

9 Figure 1: North American Stress Orientation Map 18 (stars ae field locations annotated by authors) countrys/na.htm Baker Hughes Incorporated. All Rights Reserved.

10 WHAT ARE WE DOING? Study of 1400 well pairs in sandstone in Western Canada (waterflooded) 2000 pairs in total Connectivity or communication analysis Baker Hughes Incorporated. All Rights Reserved.

11 Baker Hughes Incorporated. All Rights Reserved. General experience in North America is that induced Waterflood Fractures control flow more than we think

12 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 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?

13 WHAT ARE WE DOING? CONNECTIVITY/ COMMUNICATION ANALYSIS Baker Hughes Incorporated. All Rights Reserved.

14 What are we doing? Figure 18: Types of Communication Strengths Map view

15 What are we doing? Light blue water injection rates Dark blue water production rates Green Oil rates 15

16 How do we use production data to determine pathways? long term data Short term data Example of Watercut map used as surveillance data from Beliveau SPE Time (days)

17 Objective of Communication Analysis Map of communicating well pairs We want to identify key wells that communicate

18 What was done? We examine 1400 well pairs in sandstone reservoirs under waterflood in WCSB using communication analysis method Five waterfloods in non fractured high permeability Sandstone reservoirs Successful waterfloods None of the waterfloods are considered to be naturally fractured Figure 1: North American Stress Orientation Map 18 (stars are field locations annotated by authors)

19 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.

20 Early Waterflood Behavior Water breakthrough usually occurred in a on trend direction (NE-SW) On trend NE-SW Water cut Off trend NE-SW NW-SE Time

21 INJECTOR ANALYSIS Baker Hughes Incorporated. All Rights Reserved.

22 Monthly Injection Pressures vs. Injection Rates over Two Year Period; VRR~1 Reservoir Theoretical Pressure line constant Based on Darcy s flow constant res. pressure Wellhead Injection Pressure Injection Rate

23 Injection Pressures vs. Injection Rates over Two Year Period; VRR~1 Reservoir Pressure constant Fracture pressure ~ KPA ( ) psi/ft x600 m KB Banding same ~pressures ( Kpa) Theoretical line Based on Darcy s flow Injection Rate

24 Hall Plot; Evidence of Induced Fractures Injection pressure Injection rate Hall integral Injection rate drops by ½ but injection pressure is constant

25 Entire Field Late Stage Analysis 1 mile Early stage waterflood (NE/SW)

26 Zoom in Portion of Field What has happened? Partial conversion to line drive but also Communication is now East- West 1 mile

27 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.

28 What is happening???? Early Stages; Map View Off trend well On trend well NE-SW Good initial response Water cut rise first

29 What is happening???? Early Stages; Map View Off trend well Water movement initially NE-SW On trend well NE-SW Watered out Or injector

30 What is happening???? Late Stage Waterflood; Map View Off trend well On trend well NE-SW Watered out Or injector Growth in fractures On trend well NE-SW Watered out Or injector

31 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

32 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

33 So what can we do with this knowledge? Decrease injection pressures Change producer into injectors (streamline patterns) Gel treatment/polymer

34 SASKATCHEWAN Sandstone thickness=3-4 M μ oil ~350cP μ polymer =7cP API ~13 HISTORY MATCHED ~90 WELLS ON WATERFLOOD SIMULATION STUDY

35 Field BC Perm=15 D Perm=1 md

36 Oil Production non rate control Waterflood Polymer 20% Slug Polymer Gel Method Incremental RF Ultimate RF Waterflood 27% Polymer Flood 5 32% Gel Treatment 3 30% Gel Treatment w/ Polymer Flood 11 38%

37 40 Series Series waterflood alone polymer flood alone gel alone polymer flood +gel

38 Comparison of Communication Analysis with Waterflood Case (Blind test)

39 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 P inj P frac extension At late times, good reservoir management and shear failure fracture often mitigates the effect of on trend fractures c

40 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, June 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, June Baker Hughes Incorporated. All Rights Reserved.