A model for changes in coalbed permeability during primary and enhanced methane, recovery

摘要: The natural fracture network of a dual-porosity coalbed reservoir is made up two sets orthogonal, and usually subvertically oriented, cleats. Coalbed permeability has been shown to vary exponentially with changes in the effective horizontal stress acting across cleats through cleat-volume compressibility, which analogous pore compressibility porous rocks. A formulation for coalbeds during primary methane recovery, includes Langmuir type curve shrinkage term, proposed previously. This paper presents new version by making direct link between volumetric matrix strain amount gas desorbed. resulting model can be extended readily account adsorption-induced swelling as well enhanced recovery involving injection an inert or mixture into seams. validated against recently published pressure-dependent multiplier representative San Juan basin at post-dewatering production stages. then applied successfully history matching micropilot test flue (consisting mainly CO{sub 2} N{sub 2}) Fenn Big Valley,more » Alberta, Canada.« less