Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming

RI0220. (with Colorado Geological Survey). Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming, by W. R. Kaiser, A. R. Scott, D. S. Hamilton, Roger Tyler, R. G. McMurry, Naijiang Zhou, and C. M. Tremain. 151 p., 85 figs., 9 tables, 1994. Print.


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Technical Perspective and Results
Coalbed methane production has been established in the Sand Wash Basin. Large coal resources, gas shows during drilling of coal beds, and high gas contents in some coals triggered initial development along the basin margins. Results to date have been disappointing. Coalbed wells have yielded little gas and large volumes of water. In the absence of a regional analysis, neither production data nor the basin's ultimate coalbed methane potential could be fully evaluated. Thus, the need arose for an integrated geologic and hydrologic study of the basin to provide the framework for evaluating development properties and the rationale for future exploration.

Large coal resources occur in the Upper Cretaceous Williams Fork Formation and lower Tertiary Fort Union Formation in the eastern part of the Sand Wash Basin. These coals are mainly subbituminous to high-volatile B bituminous and have average gas contents of less than 200 ft³/ton. (<6.24 m³/t). Coalbed methane resources total 101 Tci (2.86 Tm³) and are 24 Tcf (680 Bm³) at shallow drilling depths of less than 6,000 ft (<1.830 m). More than 87 percent of them are in the Williams Fork. The basin's cumulative gas:water ratio is approximately 15 ft³/bbl (2.7 m³/m³). To date, low gas content and high water production have limited coalbed methane activity in the basin. Steep structural dip and coal distribution have restricted exploration to the eastern margins of the basin. Prospective Williams Fork and Fort Union coals, respectively, lie basinward in association with the Cedar Mountain fault system and westward along Cherokee Arch into the Powder Wash field area. High productivity requires that permeability, ground-water flow direction, coal distribution and rank, gas content, and structural grain be synergistically combined. That synergism explains prolific and marginal production in the San Juan and Sand Wash Basins, respectively. On the basis of a comparison between the basins, a basin-scale coalbed methane producibility model is proposed whose essential elements are: ground-water flow through thick coals of high rank and high gas content orthogonally toward no-flow boundaries and conventional trapping of gas along them.

Keywords: hydrology, coabed methane, Sand Wash Basin, Colorado, Wyoming


CONTENTS
STRUCTURAL AND STRATIGRAPHIC SETTING

TECTONIC EVOLUTION, STRATIGRAPHIC SETTING, AND COAL FRACTURE PATTERNS OF THE SAND WASH BASIN

by Roger Tyler and C. M. Tremain

Abstract

Location

Tectonic Evolution

Stratigraphic Setting

     Structural and Stratigraphic Settings of Coal-Bearing Formations

        Iles and William Fork Formations

        Almond Formation

        Lance Formation Fort Union Formation

        Wasatch Formation

        Green River Formation

Faults, Folds, and Fracture Patterns

     Faults and Folds

     Fracture Patterns

     Cleat Types

     Face-Cleat Strikes from Outcrop Observations

     Cleat Spacing and Fracture Swarms

     Cleat Mineralization

Stress Regime

Conclusions

FIGURES

1. Tectonic map of southwestern Wyoming and adjacent states showing the major tectonic elements of the Greater Green River Basin and the location of the Sand Wash Basin

2. Coal-bearing stratigraphic and confining units in the Sand Wash Basin and surrounding subbasins of the Greater Green River Basin

3. Location of the Sand Wash Basin relative to the Western Interior Seaway

4. Structure map contoured on the base of the Williams Fork Formation, Mesaverde Group, Sand Wash Basin, showing face-cleat trends

5. Structure map contoured on the top of the Williams Fork Formation, Mesaverde Group, Sand Wash Basin, showing face-cleat trends
6. Structure map contoured on the base of the Fort Union Formation, Sand Wash Basin, showing cleat trends

7. Map of tectonic elements in the Sand Wash Basin

8. Structural cross section through the Cedar Mountain fault system, drawn on the Mesaverde Group, Sand Wash Basin

9. Stress province map showing major stress province boundaries in the vicinity of the Sand Wash Basin

TABLES

1. Coal mine faults in the Sand Wash Basin

2. Cleat and fracture observations in the Sand Wash Basin

3. Cleat mineralization in the Sand Wash Basin

UPPER CRETACEOUS MESAVERDE GROUP

STRATIGRAPHY AND COAL OCCURRENCE OF THE UPPER CRETACEOUS MESAVERDE GROUP, SAND WASH BASIN

by Douglas S. Hamilton

Abstract

Introduction

Genetic Approach to Stratigraphic Analysis

Genetic Stratigraphy of the Upper Mesaverde Group

     Comparison with Traditional Stratigraphy

Coal Occurrence of the Upper Mesaverde Group

     Coal Identification

     Coal Seam Continuity

Williams Fork Genetic Depositional Sequences

     Unit 1

            Depositional Systems

            Coal Stratigraphy

            Coal Distribution

            Geological Controls on Coal Seam Occurrence

     Unit 2

            Depositional Systems

            Coal Stratigraphy

            Coal Distribution

            Geological Controls on Coal Seam Occurrence

     Unit 3

            Depositional Systems

            Coal Stratigraphy

            Coal Distribution

            Geologic Controls on Coal Seam Occurrence

     Unit 4

            Depositional Systems

            Coal Stratigraphy

            Coal Distribution

            Geologic Controls on Coal Seam Occurrence

Almond Genetic Depositional Sequence

            Depositional Systems

            Coal Stratigraphy and Distribution

             Geologic Controls on Coal Seam Occurrence

Conclusions

FIGURES

10. Stratigraphy of the Sand Wash Basin

11. Genetic stratigraphy of the upper Mesaverde Group in the eastern Sand Wash Basin

12. Northwest-southeast cross section of the upper Mesaverde Group, Sand Wash Basin, illustrating genetic stratigraphy of the Williams Fork Formation and coal occurrence

13. North-south cross section of the upper Mesaverde Group, eastern Sand Wash Basin

14. Density profile of typical Williams Fork coals

15. Net-sandstone map of Unit 1,Williams Fork Formation

16. Net-coal-thickness map of Unit 1, Williams Fork Formation

17. Net-sandstone map of Unit 2, Williams Fork Formation

18. Isopach of the Unit 2 coal seam

19. Net-coal-thickness map of Unit 2, Williams Fork Formation

20. Cross section of the Unit 2 coal

21. Percent-sandstone map of Unit 3, Williams Fork Formation

22. Net-coal-thickness map of Unit 3,Williams Fork Formation

23. Percent-sandstone map of Unit 4, Williams Fork Formation

24. Net-coal-thickness map of Unit 4, Williams Fork Formation

25. Percent-sandstone map of the Almond Formation

26. Net-coal-thickness map of the Almond Formation

COAL RANK, GAS CONTENT, AND COMPOSITION AND ORIGIN OF COALBED GASES, MESAVERDE GROUP, SAND WASH BASIN

by Andrew R. Scott

Abstract

Thermal Maturity

Gas Content

Sorption Isotherms

Gas Composition

Origin of Coalbed Gases

Conclusions


FIGURES

27. Correlation between vitrinite reflectance and coal Btu

28. Vitrinite reflectance profiles for the Sand Wash Basin

29. Vitrinite reflectance profiles using depth versus vitrinite reflectance for Mesaverde coals in the Sand Wash Basin

30. Mesaverde coal rank map

31. Histogram of ash-free Mesaverde gas contents

32. Gas content profile for the Sand Wash Basin Mesaverde coals

33. Relation between gas contents determined at room (STP conditions) and reservoir temperatures

34. West-east cross section showing the changes in gas content and gas composition between different Mesaverde coal beds 35. Adsorption isotherms for Mesaverde coalbed gases

36. Composition of Mesaverde coal bed gases

37. Variation of carbon dioxide content with gas dryness index (C1/C1-5) values

HYDROLOGIC SETTING OF THE UPPER MESAVERDE GROUP. SAND WASH BASIN

by Andrew R. Scott and W. R. Kaiser

Abstract

Introduction

Hydrostratigraphy

Hydrodynamics

Potentiometric Surface

Pressure Regime

Hydrochemistry

Regional Flow

Conclusions

FIGURES

38. Depth versus pressure plot for Mesaverde DST data from the Sand Wash Basin

39. Location of study areas, Mesaverde head data, and coalbed methane fields

40. Upper Mesaverde potentiometric-surface map

41. Mean annual precipitation, topography, and major drainage in the Sand Wash Basin

42. Mesaverde pressure-elevation plots for pressure analysis, Areas 2, 3, and 6

43. Structural-contour map of the top of the Williams Fork Formation in the Sand Wash and Washakie Basins

44. Southwest-northeast cross section across the geopressured-hydropressured,transition zone

45. West-east cross section through Washakie Basin

46. Mesaverde chlorinity map

47. Mesaverde total dissolved solids map

PALEOCENE FORT UNION FORMATION

STRATIGRAPHY AND COAL OCCURRENCE OF THE PALEOCENE FORT UNION FORMATION, SAND WASH BASIN

by Roger Tyler and R. C. McMurry

Abstract

Introduction

Lithostratigraphic Zones and Units

Fox Hills Sandstone

Lance Formation

Massive Cretaceous and Tertiary (W) Sandstone Unit

Fort Union Formation

Wasatch Formation

Sandstone and Coal Occurrence of the Fort Union Formation

Lower Coal-Bearing Unit

Gray-Green Mudstone Unit

Basin Sandy Unit

Upper Shaly Unit

Geologic Controls on the Occurrence of Paleocene Fort Union Formation Coal Beds, Sand Wash Basin

     Syntectonic Controls on Upper Cretaceous and Early Tertiary Sedimentation

Conclusions

FIGURES

48. Type log and stratigraphic nomenclature of the Paleocene Fort Union Formation, Sand Wash Basin. and the occurrence of coal

49. Northwest-southeast stratigraphic cross section A-A' of the Paleocene Fort Union Formation, Sand Wash Basin, illustrating operationally defined stratigraphic units and coal occurrence

50. West-east stratigraphic cross section B-B' through TI 2N of the Paleocene Fort Union Formation, Sand Wash Basin, illustrating operationally defined stratigraphic units and coal occurrence of the lower coal-bearing unit

51. West-east stratigraphic cross section C-C' through T1ON of the Paleocene Fort Union Formation, Sand Wash Basin, illustrating operationally defined stratigraphic units and coal occurrence of the lower coal-bearing unit

52. Location of stratigraphic cross sections A-A' to E-E' (figs. 49, 50, 51, 57, and 58) in the Paleocene Fort Union Formation, Sand Wash Basin

53. Net-sandstone-thickness map of the massive CretaceousiTertiary (Kill sandstone unit, Sand Wash Basin

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

55. Net-sandstone percentage map of the lower coal-bearing unit, Fort Union Formation, Sand Wash Basin

56. Maximum-sandstone-thickness map of the lower coal-bearing unit, Fort Union Formation, Sand Wash Basin

57. Detailed west-east stratigraphic cross section D-D' through TI 2N of the lower coal-bearing unit, Paleocene Fort Union Formation, Sand Wash Basin, illustrating occurrence of coal packages 1 and 2

58. Detailed north-south stratigraphic cross section E-E' between R92W and R93W of the lower coal-bearing unit, Paleocene Fort Union Formation, Sand Wash Basin, illustrating occurrence of coal packages 1 and 2

59. Maximum-coal-thickness map of the lower coal-bearing unit. Fort Union Formation. Sand Wash Basin

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

61. Coal-isopleth map of the lower coal-bearing unit, Fort Union Formation, Sand Wash Basin

62. Net-mudstone-thickness map of the gray-green mudstone unit, Fort Union Formation, Sand Wash Basin

63. Net-sandstone-thickness map of the basin sandy unit, Fort Union Formation, Sand Wash Basin

64. Block diagrams showing the stratigraphic development of the Fort Union Formation, Sand Wash Basin

COAL RANK, GAS CONTENT, AND COMPOSITION AND ORIGIN OF COALBED GASES, FORT UNION FORMATION, SAND WASH BASIN

by Andrew R. Scott

Abstract

Thermal Maturity and Gas Content

Coal Rank

Gas Content

Gas Composition

Origin of Coalbed Gases

Conclusions

FIGURES

65. Fort Union vitrinite reflectance profiles relative to elevation and depth

66. Coal rank map for the base of the Fort Union

67. Histogram of gas content values for Fort Union coal samples

68. Gas content profiles for Fort Union coals

69. Adsorption isotherms for Fort Union coal samples

70. Gas content determined at room and reservoir temperatures

HYDROLOGIC SETTING OF THE FORT UNION FORMATION. SAND WASH BASIN

 by Andrew R. Scott and W. R. Kaiser

Abstract

Introduction

Hydrostratigraphy

Hydrodynamics

Potentiometric Surface

Pressure Regime

Hydrochemistry

Regional Flow

Conclusions

FIGURES

71. Pressure-depth plot for Fort Union DST data, Sand Wash Basin
72. Fort Union pressure-analysis areas and DST well locations

73. Equivalent fresh-water heads and pressure gradients in the lower coal-bearing unit, Fort Union Formation
74. Fort Union pressure-elevation plots for four pressure-analysis areas

75. Distribution of vertical pressure gradients by well, Fort Union Formation

76. West-east hydrochemical cross section, Sand Wash Basin

77. Equivalent fresh-water heads and pressure gradients in the upper shaly unit, Fort Union Formation

RESOURCES AND PRODUCTION

RESOURCES AND PRODUClBlLlTY OF COALBED METHANE IN THE SAND WASH BASIN

by W. R. Kaiser, Andrew R. Scott, Naijiang Zhou, Douglas S. Hamilton, and Roger Tyler

Abstract

Introduction

Resources

Production

Controls on Production

Producibility

Conclusions

FIGURES

78. Gas content profiles and equations used for in-place gas and coal resource calculations

79. Initial water potentials, Williams Fork and Fort Union coals

80. Geologic and hydrologic characterization of the Williams Fork Formation

81. Geologic and hydrologic characterization of the Fort Union Formation

82. Interplay of geologic and hydrologic controls

83. Key geologic and hydrologic controls

84. Geologic and hydrologic comparison of the San Juan and Sand Wash Basins

85. Schematic cross-sectional ground-water flow,San Juan Basin

TABLES

4. Coalbed methane resources of the Sand Wash Basin

5. Coal resources of the Sand Wash Basin

6. Coalbed methane resources in the Williams Fork Formation

7. Coal resources in the Williams Fork Formation

8. Cumulative gas and water production

9. Coal and gas resources in the Sand Wash Basin based on depth to the base of the coal-bearing unit

ACKNOWLEDGMENTS

REFERENCES


Citation
Kaiser, W. R., Scott, A. R., Hamilton, D. S., Tyler, Roger, McMurry, R. G., Zhou, N., and Tremain, C. M., 1994, Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 220, 151 p.