Numerical Simulation Research Of Shale Gas Flowing In Multi-scale Pore

The development and utilization of shale gas would alleviate the shortage of traditional fossil energy,which is a focus problem in the study of development of oil and gas all over the world.Considering about nano-scale porosity,the kinds of reservoir of shale gas,and different kinds of flow characteristics.Based on the SEM image of core of shale,the equivalent model of microstructure of the shale rock is constructed by using the model of capillary beam.Then getting permeability of shale after calculating.At the same time,the permeability when considering adsorption effect was calculated.The result shows that the permeability when considering adsorption effect will be lowwer than without adsorption.And then based on the Langmuir adsorption isotherm equation,discrete fracture network model,and the law of conservation of mass.We deduced respectively mathematical model including single-phase of gas and double-phase of water and gas in the matrix and cracks pore.Finally the dual medium mathematical model of seepage shale gas can be gotten.Then the model and parameters would be analyzed by using Comsol software,contrastive analysis can be done by changing the parameters of geology and artificial modification.In the section of geology,the traditional double medium model is compared with discrete fracture network(DFN)model.The simulation result shows that DFN model is better than Warren-Root model.In the section of parameters of artificial modification,the number of cracks,opening of cracks as well as the length of cracks are analyzed.The results show that with the increasing of number,opening and length,the speed of gas production also increases.However,as for a fixed gas pool,the degree of influence would decrease.As for a long term development,the length is the most important.In addition,the influence of development of shale gas of gas-water two-phase flow is also considered.The results show that when there is water,it would be more difficult for gas to flow.Near the wellhole and cracks,there would be ‘water wall',which will impede the flow of gas further.