煤层气井压裂裂缝参数优化新方法

A NEW MODEL FOR OPTIMAL FRACTURE PARAMETERS DETERMINATION FOR FRACTURING IN CBM WELLS

以往煤层气井压裂缝参数优化方法没有考虑压后裂缝渗透率变化和压裂规模的影响。基于支撑剂指数法,考虑压后动态裂缝渗透率,建立了与压裂规模相关的裂缝参数优化数学模型。通过双重迭代求解得到了最优压裂规模下的最佳裂缝参数,并绘制了不同煤层渗透率和压裂规模下的裂缝参数优化图版。计算结果表明,压裂规模并非越大越好,存在最优规模;煤层压裂裂缝内非达西流动使最优缝长减小,最优缝宽增大。该方法应用简便,优化结果更准确、合理,对煤层压裂改造具有一定指导意义。

The effects of the fracture permeability produced after fracturing and fracturing scale are not considered in previous fracture parameter optimization methods for CBM wells. For the realization of fracture parameters optimization for fractured CBM wells,based on proppant index method,considering the effects of dynamic change of fracture permeability,a mathematical model is set up which is related with fracturing scale. With the multiple iteration method,the optimal fracture parameters can be obtained under optimal fracturing scale conditions. And fracture parameters optimization chart is drawn for different coal seam permeability and fracturing scale. The result shows that there is an optimal value for proppant volume to gain maximum productivity after fracturing. The more severe non-Darcy flow effect in the fracture,the smaller optimal fracture length is,and the larger the optimal fracture width is. The method is simple to use,and the optimization results are more accurate and reasonable. So it can be used to guide fracturing for CBM well.