考虑非达西效应的致密气藏裂缝参数优化设计

为了实现致密气藏裂缝参数优化设计,考虑非达西效应对裂缝渗透率的影响,引入有效渗透率,对传统的支撑剂指数进行了修正;然后,利用边界元法,作出表征无因次采气指数、支撑剂指数和裂缝有效导流能力之间关系的图版,拟合出f函数;最后,通过迭代获得最优裂缝参数和裂缝导流能力,形成了以采气指数为目标函数、考虑非达西效应的致密气藏裂缝参数优化设计方法.利用苏里格气田某致密气藏的数据,对比分析了是否考虑非达西效应对裂缝参数优化设计的影响.结果表明,考虑非达西效应后,支撑剂指数为不考虑非达西效应时的1/5,有效导流能力为不考虑非达西效应时的1/3,最优缝长缩短了1/5,最优缝宽增大了1/4.研究结果表明,利用修正支撑剂指数可以进行致密气藏裂缝参数的优化设计,利用该方法优化的缝长和缝宽与修正前相比分别缩短和增宽,设计结果更加准确. 

Optimization of Fracture Parameters for Tight Gas Reservoir Considering Non-Darcy Effect

In order to determine the optimum design of the fracture parameters for tight gas reservoirs,effective permeability was introduced to modify the conventional proppant number considering the impact of non-Darcy effects on fracture permeability and conductivity.The boundary element method was used to make a chart which represented the relationship among the non-dimensional gas productivity index,the proppant number and the effective fracture conductivity,and then obtained an equation of f function.Next,the optimal parameters and conductivity of the fracture network were obtained through iterations of the algorithm,and formed an optimization method of fracture parameter in tight gas reservoir which considered non-Darcy effect and taken gas productivity as objective function.The data of tight gas reservoir in Sulige block was used to analyze the impact of non-Darcy effect on the optimization of fracture parameters.The results showed that,when considering non-Darcy effect,the proppant number was 20 percent of that without considering it,and the effective fracture conductivity was 33 percent,the optimal fracture length was reduced by 20 percent,and the width of fracture increased by 25 percent.In conclusion,the optimal design of tight gas reservoir fracture parameter can be calculated by revising the proppant number,which resulted in shorter and wider.