This paper presents a predictive technique for simultaneous determination of capillary pressure and relative permeability characteristics of coalbed methane reservoir specimens. The technique utilizes a systems-response model of transient fluid production data from a modified porous-plate experiment. The model consists of(1) a modified Langmuir-type equation for the extrapolation of transient laboratory production data to capillary equilibrium, (2) a one-dimensional, two-phase, dual porosity simulator, and (3) an automatic parameter estimation routine based on the Levenberg-Marquardt non-linear optimization scheme. Different modules of the model are integrated to determine capillary pressure and relative permeability characteristics as well as cleat pore volume of coal specimens.

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