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| Application of fractal theory in nonequilibrium adsorption model of coalbed methane |
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| DOI：10.7511/jslx20083077 |
| KeyWord:coalbed methane,dual media,fractal dimension,regular perturbation,Laplace transform |
| ZHANG Xian-min TONG Deng-ke |
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| Abstract: |
| Most of gas stored in coalbed methane reservoirs exists in adsorbed state rather than in free state,therefore the study on gas flow in coalbed methane reservoirs is of great importance.However,conventional mathematical models of coalbed methane were based on Euclid Geometry and difficult to describe the complexity of pore structure and the irregularity of shape.In this paper,in consideration of the double porosity,the adsorption effect of coal beds and the deformation of media,new unsteady percolation models based on Fick's second law were established by introducing fractal parameters to describe the complexity of pore structure in coal beds.Owing to the strong nonlinearity of new flow equations,models combining various boundary conditions were solved by use of regular perturbation method and Laplace transform,and the zero-order perturbation solution were obtained through Laplace numerical inversion.The change rules of dimensionless pressure along with the changes in parameters were discussed,and typical pressure curves were drawn up through new models.All of these results have provided a theoretical basis and new well test models for coalbed methane reservoir development. |
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