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
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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
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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
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
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
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)
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
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
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
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