The Application of a Coalbed Methane...Model in Defining Coalbed Methane

RI0244. The Application of a Coalbed Methane Producibility Model in Defining Coalbed Methane Exploration Fairways and Sweet Spots: Examples from the San Juan, Sand Wash, and Piceance Basins, by Roger Tyler, A. R. Scott, W. R. Kaiser, and R. G. McMurry. 59 p., 37 figs., 1 table, 1997. Print.

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About This Publication
This report applies a basin-scale coalbed methane producibility model in defining fairways and sweet spots in three coal basins in the United States.

ABSTRACT
The Bureau of Economic Geology, The University of Texas at Austin, has developed a basin-scale coalbed methane producibility and exploration model based on a decade of Gas Research Institute-supported research performed in the San Juan, Sand Wash (Greater Green River), and Piceance Basins and on reconnaissance studies of several other producing and prospective coal basins in the United States. In this report we discuss the application of the producibility model in defining coalbed methane exploration fairways and sweet spots in coal basins in the United States. The producibility model also has direct application to worldwide coalbed methane exploration and development. The model indicates that tectonic and structural setting, depositional systems and coal distribution, coal rank, gas content, permeability, and hydrodynamics are controls critical to coalbed methane producibility. Simply knowing a basin's geologic and hydrologic characteristics will not lead to a conclusion about coalbed methane producibility, however, because it is the interplay among geologic and hydrologic controls on production and their spatial relation that governs producibility. High producibility requires that the geologic and hydrologic controls be synergistically combined. That synergism is evident in a comparison of the prolific producing San Juan Basin and marginally producing Sand Wash and Piceance Basins, where high productivity is governed by (1) thick, laterally continuous coals of high thermal maturity; (2) adequate permeability; (3) basinward flow of ground water through coals of high rank and gas content orthogonally toward no-flow boundaries (regional structural hingelines, fault systems, facies changes, permeability contrasts, and/or discharge areas); (4) generation of secondary biogenic gases; and (5) conventional and hydrodynamic trapping along those boundaries to provide additional gas beyond that generated during coalification. Understanding the dynamic interaction among these key geologic and hydrologic controls is the basis for delineation of exploration fairways in frontier basins and for targeting "sweet spots" in basins with established production.

Keywords: coalbed methane producibility model, exploration fairways and sweet spots, Piceance Basin, San Juan Basin, Sand Wash Basin

CONTENTS

Abstract

Introduction

Coalbed Methane Producibility Model

Screening Multiple Basins for Coalbed Methane Potential

      An Example of Selecting a Frontier Basin for Future Coalbed Methane Exploration and Development
          Criteria for Multibasin Screening and Evaluation

     An Example of a Multibasin Screening and Evaluation Exercise

          Greater Green River Basin

          Piceance Basin

          Powder River Basin

          Raton Basin

      Multibasin Comparison

Geologic and Hydrologic Basin Analysis Used to Identify Controls on Coalbed Methane Producibility

    San Juan Basin

         Tectonic and Structural Setting

         Depositional Setting and Coal Distribution

         Coalification and Burial History

         Hydrodynamics and Permeability

         Gas Content

     Sand Wash Basin

          Tectonic and Structural Setting

          Depositional Setting and Coal Distribution

          Coalification and Burial History

          Hydrodynamics and Permeability

          Gas Content

     Piceance Basin

          Tectonic and Structural Setting

          Depositional Setting and Coal Distribution

          Coalification and Burial History

          Hydrodynamics and Permeability

          Gas Content

Application of the Producibility Model in Defining Exploration Fairways and Sweet Spots in the
San Juan. Sand Wash. and Piceance Basins

     San Juan Basin

     Sand Wash Basin

     Piceance Basin

Conclusions

Acknowledgments

Conversion Chart

References

Figures

1. Coal basins and coalbed methane resources of the United States

2. Geologic and hydrologic controls on the producibility of coal gas

3. Basin comparison for coalbed methane model development

4. Sorption isotherms showing relation between gas content, pressure, and temperature

5. Conceptual model for high coalbed methane producibility

6. Coalbed methane exploration and development flow chart

7. Structure map (Huerfanito Bentonite) and face-cleat strikes, San Juan Basin

8. Fruitland net-coal map, San Juan Basin

9. Southwest-northeast stratigraphic cross section A-A' (D-20), from gamma-ray geophysical logs, San Juan Basin

10. Depositional model of Fruitland coal beds, San Juan Basin

11. Fruitland coal-rank map, San Juan Basin

12. Fruitland potentiometric-surface map and area of artesian overpressure, San Juan Basin

13. Coal stratigraphy of the Sand Wash Basin

14. Structure map, contoured on base of Williams Fork Formation, and face-cleat trends, Sand Wash Basin

15. Net-coal map, genetic unit 1, lower coal-bearing interval, Williams Fork Formation, Sand Wash Basin

16. Net-coal-thickness map of the lower coal-bearing unit, Fort Union Formation, Sand Wash Basin

17. Mesaverde coal-rank map, Sand Wash Basin

18. Upper Mesaverde potentiometric-surface map, Sand Wash Basin

19. Structure map contoured on top of the Rollins-Trout Creek Sandstone Members, Piceance Basin

20. Topographic map of the Piceance Basin

21. Face-cleat strikes and domains in the Mesaverde Croup and Wasatch Formation coal beds, Piceance Basin

22. Maximum horizontal stress orientations in the Piceance Basin area

23. Net-coal-thickness map of genetic units 1 through 3, Williams Fork Formation

24. Coal-rank map of the Cameo coal group from measured and calculated data

25. Schematic diagram showing importance of thrust faulting to regional hydrogeology

26. Williams Fork potentiometric-surface map, Piceance Basin

27. Vertical pressure gradients by study area

28. Pressure-elevation plots for study area 11 along the Divide Creek Anticline and study area 2 in White River field

29. Characteristics of key geologic and hydrologic controls. overlapping in the Rocky Mountain foreland basins, western United States

30. Geologic and hydrologic characterization of the Fruitland Formation, San Juan Basin

31. South-north cross-sectional view of ground-water flow, Fruitland-Pictured Cliffs and Tertiary aquifer systems, San Juan Basin

32. Fruitland pressure and temperature gradients and ground-water flow in the high-productivity fairway

33. Geologic and hydrologic characterization of the Williams Fork Formation, Sand Wash Basin

34. Southwest-northeast cross-sectional view C-C' of ground-water flow, Williams Fork Formation, Sand Wash Basin

35. Geologic and hydrologic characterization of the Williams Fork Formation, Piceance Basin

36. Northwest-southeast cross-sectional view B-B' of ground-water flow, Williams Fork Formation, Piceance Basin

37. Exploration target areas, Piceance Basin

Table

1. Summary of coalbed methane criteria critical to coal basin assessment


Citation
Tyler, Roger, Scott, A. R., Kaiser, W. R., and McMurry, R. G., 1997, The Application of a Coalbed Methane Producibility Model in Defining Coalbed Methane Exploration Fairways and Sweet Spots: Examples from the San Juan, Sand Wash, and Piceance Basins: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 244, 59 p.