Study On Shale Gas Seepage Model Considering Discrete Cracks And Migration Law

Shale gas has becoming the key research object of energy development in China,as a new kind of clean energy.Occurrence mechanism,migration law and development method of shale gas are all different from conventional oil and gas reservoir.Because of the particularity of shale gas reservoir,horizontal well and hydraulic fracturing technology have being the main mining technology in the commercial exploitation of shale gas.In order to controlling the cost of fracturing in a high efficiency mining,the optimum design of fractured fracture parameters becoming more and more is important.In this paper,we based on the development mechanism of shale gas,studied on the effect of the natural fracture,especially the fracturing fracture in shale gas mining.The following conclusions are obtained:(1)Based on a large number of domestic and foreign literatures,we have studied accumulation mechanism,migration mechanism and yield increasing mechanism about shale gas,and discussed the flow law of shale gas.Considering the effect of desorption,diffusion and slippage on the process of shale gas migration,based on the dual medium,considering the advantage of reducing and processing the discrete cracks,a shale gas seepage model considering discrete fractures was established.(2)The presence of natural fractures in shale reservoir was formed in the fracture network,when a small number of natural fracture reservoirs in the connected directly,and indirectly connected most of the natural fractures.In shale gas mining process,with the increase of the number of natural fractures,pressure drop area becomes larger in shale reservoirs the distribution of natural fracture,the more connectivity will become better between the cracks in the reservoir,seepage for shale gas in the reservoir.With the increase of natural crack width,influence on the pressure in the reservoir is increasing gradually.(3)Reservoir pressure influenced by the the connectedness of fractures.It is the fracturing fracture,connected with the natural cracks.The influence of each fracture on the change of reservoir pressure is limited.It will occur interaction phenomenon,when the fracture distance is too small.Because fracturing fracture opening the greater conductivity in shale.As we know,the fracture’s flow capacity is limited,so the fractures’ width is not as widely as possible.In the practical engineering of shalegas,we should optimize a reasonable optimization of the width of fracturing fractures.