Capacity Analysis Of Low-permeability Coal Seam Gas-pressure Cracking Wells Considering Fluid-solid Coupling Effects

China's coal bed gas resources is very rich, and it's development potential is huge, but the occurrence conditions is low permeability, low saturation, low reservoir pressure characteristics, with complex geological conditions and have many influence factors for productivity, the change of stress will also lead to the change of permeability in the mining process. Therefore, this paper establish the seepage flow mathematical model considering fluid-solid coupling effect near wellbore according to the theory of elastic mechanics and fluid mechanics in porous medium, and analysis the sensitivity of layer parameters which influence coal bed methane production capacity, and put forward coal bed gas reservoir productivity evaluation method considering fluid-solid coupling effect, so as to provide theoretical basis for the rational proration of coal bed gas reservoir field.The main research results are as follows:(1) Research the impact factors of the fracture well productivity from the aspects of engineering and geology, through the contrast analysis, put reservoir permeability, storage layer pressure, reservoir thickness and half-length of hydraulic fractures, number of hydraulic fractures as the main influence factors of coal bed gas fractured well productivity.(2) Establish mathematical model of coal bed gas desorption, diffusion and seepage and the permeability change model considering the change of reservoir characteristics such as increase of reservoir effective stress and coal matrix shrinkage when fluid is discharged and coal bed gas is desorbed in the process of coal bed gas exploitation.(3) Establish conceptual model by CMG, then analysis the sensitivity of various factors for the production of common horizontal wells and fractured horizontal wells, put the maximum daily gas production, daily gas production after ten years, and cumulative gas production of ten years as the evaluation index, analysis the different production between common horizontal wells and fractured horizontal wells, provide reference for fracturing implementation.(4) On the foundation of actual geological coal reservoir model in JinCheng of ShanXi province establish the single horizontal well and two branches horizontal well, analysis of the law of production capacity caused by fluid-solid coupling effect, we find that the cumulative gas production of ten years increased by more than 7% for fractured horizontal well and fracturing two branch horizontal well when considering the fluid solid coupling effect.