Tom Wilson Department of Geology and Geography West Virginia University Morgantown, WV

1. Developing a strategy for CO2 EOR in an unconventional reservoir using 3D seismic attribute workflows and fracture image logs ACTIVITY & ELEMENT2.651.070.001.511 FAULT AND FRACTURE ZONE DETECTION AND REDUCED ORDER FRACTURE MODEL DEVELOPMENT FOR RISK ASSESSMENT TomWilson Department of Geology and Geography West Virginia University Morgantown, WV Tom Wilson, Department of Geology and Geography

2. Overview • Reservoir characterization is developed using analysis of 3D seismic and fracture image logs and seismic attribute workflows for fracture driver development to distribute fracture intensity throughout the reservoir. • Analysis of fracture image logs reveals that the dominant open fracture trend within the reservoir is coincident with present-day SHmax. • Outcrop analogs and satellite observations are used to develop model distributions of fracture length, height and spacing • Fracture intensity driver is developed using a combination of seismic discontinuities and directional curvature (orthogonal to SHmax). • Reservoir compartmentalization is interpreted. • A strategy for CO2 EOR is proposed that incorporates placement of injection and production laterals along compartment boundaries and roughly orthogonal to SHmax. Tom Wilson, Department of Geology and Geography

3. Location of study area and reservoir structure Tom Wilson, Department of Geology and Geography

4. Dip line views of structure Wall Creeks Morrison Alcova Goose Egg Tensleep Madison Basement Tom Wilson, Department of Geology and Geography

5. Fracture characterization using image logs. Open fractures in seal, reservoir and in total SHmax Tom Wilson, Department of Geology and Geography

6. Open fracture trends in the reservoir by well and for all wells SHmax Tom Wilson, Department of Geology and Geography

7. Field analogs of seismic discontinuities Fracture Zone 280’ Fracture Zone

8. Defining fracture parameters-Fracture height distribution Tom Wilson, Department of Geology and Geography

9. Higher power implies lower probability of higher fractures -1.61 -2.18 -1.62 Tom Wilson, Department of Geology and Geography

10. Spacing distributions estimated in Freemont Canyon Tom Wilson, Department of Geology and Geography

11. Variations of fracture intensity in the reservoir Tom Wilson, Department of Geology and Geography

12. Fracture length distributions from World view ½ meter resolution imagery Outcrop viewed from opposite side of canyon Tom Wilson, Department of Geology and Geography

13. Local fractures mapped using WorldView imagery Tom Wilson, Department of Geology and Geography

14. Fracture length distributions(from WorldView imagery) Tom Wilson, Department of Geology and Geography

15. Seismic discontinuity length distribution Tom Wilson, Department of Geology and Geography

16. Aperture distributions – log normal with some power law behavior for apertures above ~0.05 mm Tom Wilson, Department of Geology and Geography

17. Seismic discontinuity detection workflow Discontinuity detection workflow components A variety of post-stack processing workflows have been developed as part of this research. Multiple workflows are usually tested and compared. Some example discontinuity detection workflows are shown at left. Often, discontinuities can be significantly enhanced simply by taking the absolute value of the seismic trace or taking a trace derivative followed by taking it’s absolute value. Low pass filtering is sometimes required to reduce high-frequency noise. Tom Wilson, Department of Geology and Geography

18. Comparison of amplitude and enhanced seismic data In general, data prep is an iterative process Tom Wilson, Department of Geology and Geography

19. The derivative enhances high frequency content and introduces a 90o phase shift Tom Wilson, Department of Geology and Geography

20. Absolute value doubles apparent spectral content Tom Wilson, Department of Geology and Geography

21. Extracted discontinuities Tom Wilson, Department of Geology and Geography

22. NE oriented discontinuities are interpreted to arise from right lateral transpressional shear S1 Fault Tom Wilson, Department of Geology and Geography

23. Incorporating possible influence of curvature on dominant fracture aperture Maximum directional curvature orthogonal to the dominant open fracture set & SHmax. SHmax Tom Wilson, Department of Geology and Geography

24. Potential compartmentalization within the reservoir suggested by production distribution 5 yr cumulative production (Smith, 2008) Log 10 yr cumulative production Tom Wilson, Department of Geology and Geography

25. Volume probe through combined discontinuity and directional curvature volume Tom Wilson, Department of Geology and Geography

26. Composite driver development • Discontinuities and directional curvature were extracted from 3D seismic. • Conditional statements were used to zero-out high-scoring discontinuities and isolate positive curvature. • Only regions with positive curvature were incorporated in the intensity driver. • Discontinuity and curvature parameters were upscaled into a model grid and combined to produce an intensity driver that could be used to control the distribution of fractures in the reservoir. Tom Wilson, Department of Geology and Geography

27. Intensity distribution Tom Wilson, Department of Geology and Geography

28. Drilling strategy producer Production lateral injector CO2 injection lateral Dominant open fracture trend SHmax SHmax Tom Wilson, Department of Geology and Geography

29. Workflow integration Continued from Discontinuity Detection Workflow Image log Field analog 3D seismic Derived 3D Discontinuity Volume Analyze Distributions of Dominant Open Fracture Trends Examine directional Curvature at Scale of Seismic Discontinuities Incorporate Analysis of Field Data to Help Constrain Length, Height and Spacing Distributions Estimate Aperture Distribution Identify potential for compartmentalization Determine Orientation of Shmax from Drilling Induced fractures or Breakouts Manipulate Attribute Values to Highlight Low and High Permeability regions in Reservoir Upscale and Combine to Provide Fracture Intensity Driver Develop DFN Tom Wilson, Department of Geology and Geography

30. Novel aspects of the approach • The new driver addresses the possibility that NE oriented higher-score discontinuities may represent low permeability zones that could compartmentalize the reservoir; and, • use of maximum directional curvature orthogonal to the more prevalent N76oW hinge-oblique open fracture set in the reservoir focuses on that curvature component that could enhance apertures of the dominant fractures set. Curvature in this direction acts in tandem with the orientation of SHmax inferred from induced fractures observed in the fracture image logs to enhance permeability in the N76W trend. Tom Wilson, Department of Geology and Geography

31. Recent paper and meeting preparations Developing a strategy for CO2 EOR in an unconventional reservoir using 3D seismic attribute workflows and fracture image logs: Paper submitted for presentation at the Annual SEG meeting, Sept., 2013, Thomas H. Wilson, National Energy Technology Laboratory and West Virginia University; Valerie Smith, Schlumberger Carbon Services, and Alan Brown, Schlumberger NExT, 5p. Characterization of Tensleep reservoir fracture systems using outcrop analog, fracture image logs and 3D seismic: Abstract submitted for presentation at the Annual AAPG Rocky Mountain Section meeting, Thomas H. Wilson, National Energy Technology Laboratory and West Virginia University; Valerie Smith, Schlumberger Carbon Services, and Alan Brown, Schlumberger NExT Tom Wilson, Department of Geology and Geography

32. Future work1. carry through to simulation, or Seismic analysis Image log analysis Reservoir Engineering Field analog Bring in additional field observations: Alcova and Granite Mountain Anticlines Devise methods for incorporating results from seismic analysis into FRACGEN model Bring in production data Develop DFN in FRACGEN Bring in reservoir parameters (Smith, 2008) Incorporate in ROM Simulation and history matching Tom Wilson, Department of Geology and Geography

33. Future work2. carry through to simulation in alternative unconventional reservoir The reservoir characterization workflows presented here can be extended to other reservoirs as needed to support NETL priorities. DFN’s, although not presented as part of today’s discussions, have been developed for numerous reservoirs. The methodologies are adaptable and can be readily applied to new settings given sufficient data. Tom Wilson, Department of Geology and Geography