Considering the effects of both steady and unsteady desorption of Coal Bed Methane(CBM),two kinds of dual-porosity unsteady seepage models are developed,including pseudo-steady cross-flow model and dual-porosity unsteady cross-flow model.The two models are solved by finite volume method and their characteristic curves are analyzed by considering different geological parameters.The calculation results show that both steady desorption and unsteady desorption of CBM delay the propagation of pressure wave;the increase of CBM desorption coefficients makes the pressure draw down slowly in the coalbed,it manifests the increase of boundary distance in pressure and pressure derivative curve.For different coalbeds,when either the cross-flow flow coefficient or the fracture storage coefficient is oversize,the dual-porosity media characters in theoretical curves will be covered up.The fact is consistent with the field test data which are difficult to appear the dual-porosity media characters.Therefore the root of the problem is discovered based on the research,while the field test data is hard to show the dual-porosity media characters.
; 刘曰武
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