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针对储层与井身的不同距离,建立不同流动速度的线性-非线性渗流的Darcy-Brinkman流场数学模型,采用数值模拟的方法分析了裂缝半长、裂缝条数、裂缝宽度对煤层气流速的影响规律.研究结果表明:随着裂缝半长、条数、宽度的增加,压裂面积增大,增大了井身与裂隙的接触面积,增加了气体排泄的面积,同时储层压强差梯度增大,促使更多的流体流进井口内,从而使煤层气的流速增加.对于相同地质条件的煤层气藏,裂缝半长、条数、宽度并不是越大越好,通过正交试验得出裂缝参数对压裂井产能影响的重要性依次为裂缝条数、裂缝半长、裂缝宽度.因此合理改变裂缝参数有利于提高煤层气流速,控制压降速率和增大压降范围.
According to the different distance between reservoir and wellbore, a Darcy-Brinkman flow field mathematical model of linear-nonlinear seepage flow with different flow velocities is established. The influence of half length of crack, number of cracks and width of crack on the velocity of coalbed methane .The results show that with the increase of half length, number and width of fractures, the fracturing area increases, which increases the contact area between well bore and fractures and increases the area of gas discharge, meanwhile, the difference of reservoir pressure As the gradient increases, more fluid will flow into the wellhead and the flow rate of coalbed methane will increase.For a CBM reservoir with the same geological conditions, the crack length is not longer, the number of strips and the width are not as good as possible. Through orthogonal experiments The importance of fracture parameters to fracturing well productivity is followed by the number of fractures, the length of fracture and the width of fracture, so changing the fracture parameters reasonably can improve the velocity of CBM, control the pressure drop rate and increase the pressure drop range.