The document summarizes a simulation study on the effects of well spacing, permeability anisotropy, and the Palmer and Mansoori model on coalbed methane production. The study used a dual-porosity simulation model to analyze gas production from a single coal seam under different well spacing and configurations. It found that closer well spacing increased production rates and recovery. Placing wells along the direction of higher permeability in anisotropic reservoirs also improved recovery. The Palmer and Mansoori model, which accounts for matrix shrinkage and cleat compression, impacted predicted production rates and should be considered in coalbed methane simulations.

1. Simulation Study of The Effect of Well Spacing, Permeability Anisotropy, and Palmer and Mansoori Model on Coalbed Methane Production Ismail Zulkarnain Harold Vance Department of Petroleum Engineering. Texas A&M University 25 th July, 2005

5. US Coalbed Methane Resource 5 “ Coalbed methane activity is increasing in the U.S., the world leader in reserves and production, due to recent high gas prices and dwindling conventional gas supplies” Walter B. Ayers

6. US Coalbed Methane Resource 5 Proved Reserves 18,743 bcf US Production (2003) 1600 bcf 8% of US dry gas production

8. CBM and Conventional Natural Gas 7 Typical Conventional Natural Gas CBM Depth 150 to 3000m 150 to 1500m Water Rates may increase during production Rates typically decreases during production life Well Spacing Normally, 1 well per square mile but density may be increased 2 to 8 wells per square mile Gas Storage Stored in macropores or fractures Stored as adsorbed gas on the coal matrix

10. Reservoir Characteristics of Coal 9

12. Schematic of Coalbed Methane Well 11 PUMP GAS COAL WATER CEMENT OVERBURDEN Water (Sand, shale, and thinner coal beds) PUMP MAY BE SET IN COAL RATHER THAN IN RAT HOLE

13. Adsorption and Desorption (Sorption) in Coal 12

14. Langmuir Theory of Single Molecule Adsorption 13

15. Reservoir Mechanism 14 Coalbed Adsorption Phenomenon

16. Reservoir Mechanism 15

24. Simulation Details 23

25. Relative Permeability Curves 24

26. Well Spacing Effect 25

27. 80 acre spacing

28. 40 acre spacing

29. 80 acre spacing

31. 20 acre spacing

32. 80 acre spacing

33. Well Spacing Effect Comparison of an 80 acre well and a 40 acre well 27

34. Simulation scenarios 28 y = 1866.76 ft x = 1866.76 ft 80 acre-Isotropic Reservoir A y = 1320 ft x = 1320 ft 40 acre-Isotropic Reservoir B

35. Gas rate (scf/day) per well basis 29

36. Water rate (bbl/day) per well basis 30

37. Comparison of 80 acre spacing, 40 acre spacing, 20 acre spacing, and 5 acre spacing on an 80 acre reservoir 31

38. 32 Reservoir model y = 1866.76 ft x = 1866.76 ft Isotropic-Square Reservoir System 80 acre

39. Simulation scenarios 33 80 acre reservoir with 20 acre spacing A B C D 80 acre reservoir with 80 acre spacing 80 acre reservoir with 40 acre spacing 80 acre reservoir with 5 acre spacing

40. Gas rate (scf/day) per field basis 34

41. Water rate (scf/day) per field basis 35

42. RF Gas (fraction) per field basis 36

43. RF Water (fraction) per field basis 37

44. RF Water (fraction) per field basis 38

45. Permeability Anisotropy 39

47. 41 Problem Statement y x Anisotropic - Reservoir System Permeability in x-direction is higher than permeability in y-direction Butt Cleats Face Cleats

48. 42 Reservoir model y = 1866.76 ft x = 1866.76 ft Anisotropic-Square Reservoir System (k X =1 md and k Y =0.01 md)

52. Gas rate (scf/day) per field basis 46

53. Water rate (scf/day) per field basis 47

54. RF Gas (fraction) per field basis 48

55. RF Water (fraction) per field basis 49

56. Tabulated results (Well configuration) 50

57. Palmer and Mansoori Theory 51

59. 53 Cleats compression k Overburden pressure coal matrix fracture (a) Before cleats compression (b) After cleats compression

60. 54 Matrix shrinkage Width of cleats after shrinkage Coal matrix after shrinkage Width of cleats before shrinkage Coal matrix before shrinkage Fractures/cleats Coal matrix Coal matrix Coal matrix k

61. 55 Palmer and Mansoori model Cleats Compression Matrix Shrinkage

62. 56 Palmer and Mansoori model

63. 57 Palmer and Mansoori model

64. 58 Palmer and Mansoori model It has an implication on the gas production:

65. Sensitivity Analysis on Palmer and Mansoori Model Parameters 59

67. Young’s modulus 61

68. 62 Young’s modulus

69. 62 Young’s modulus, E

70. 62 Poisson Ratio, ν

71. 62 Bulk modulus, K

72. 62 Young’s modulus, E

73. 62 Young’s modulus, E

74. 63 Young’s Modulus

75. Poisson’s Ratio 64

76. Poisson’s Ratio 65

77. 66 Poisson’s Ratio

78. Strain Maximum 67

79. Strain Maximum 68

80. 69 Strain Maximum

83. Nusantara Archipelago, Indonesia-Southeast Asia Thank You

84. Simulation Study of The Effect of Well Spacing, Permeability Anisotropy, and Palmer and Mansoori Model on Coalbed Methane Production Ismail Zulkarnain Harold Vance Department of Petroleum Engineering. Texas A&M University 25 th July, 2005

86. RF Gas (fraction) per well basis

87. RF Water (fraction) per well basis

88. Tabulated Result

89. Young’s modulus

90. Young’s modulus

91. Poisson’s ratio

92. Poisson’s ratio

93. Strain maximum

94. Strain maximum

95. Reservoir Model 30 ft 1866.76 ft 1866.76 ft

96. Transformation (Wattenbarger and Arrevallo) Simulation: Isotropic-Rectangular Reservoir System (k = 0.1) x = 590.32 ft y = 5903.2 ft b y = 1866.76 ft x = 1866.76 ft Anisotropic-Square Reservoir System (k X =1 md and k Y =0.01 md) a

99. Dual Porosity (Warren and Root) (a) (b)

100. Diffusion and Flow of Methane (a) (b) (c)

101. Scenario A y-direction/low permeability x-direction/high permeability

102. Scenario B y-direction/low permeability x-direction/high permeability

103. Scenario C y-direction/low permeability x-direction/high permeability