低渗透油藏直井体积压裂产能评价新模型

体积压裂在低渗透油藏中应用广泛,产能评价是体积压裂优化设计的基础,对提高体积改造效果有重要意义。基于直井体积压裂的复杂裂缝改造特点及流动特征,将储层划分为三个区域:主裂缝区、改造区和未改造区,结合椭圆流与线性流建立了低渗透油藏直井体积压裂的渗流模型。针对低渗透油藏非线性渗流特征,推导出了低渗透油藏直井体积压裂三区耦合产能公式,产能公式计算出来的结果与现场数据对比误差小于6%。依据鄂尔多斯盆地某特低渗透油藏的基本参数,绘制了在不同影响因素下的产能曲线,分析了主裂缝导流能力、改造区体积大小、基质渗透率对产能的影响,结果表明:产能随主裂缝导流能力的增大而提高,生产压差越大提高速率越快;储层压裂改造体积越大,产能越高,但主缝长达到一定值后增产效果不明显;压裂缝与储层条件必须匹配才能达到最佳的增产效果。

A New Productivity Evaluation Model of Volume Fracturing for Vertical Well in Low Permeability Reservoirs

Volume fracturing is widely used in low permeability reservoirs, and productivity evaluation is the basis for optimal design of volume fracturing, which is important for enhancing the effect of fracturing. Based on the fracture characteristics of volume fracturing and flow characteristics, the seepage model of volume fracturing for vertical well in low permeability reservoirs is established by combining elliptic flow and linear flow. According to the different fluid flow patterns in the reservoirs, three zones are divided: the primary fracture, ESRV(Effective Stimulated Reservoir Volume) and UnSRV(Un-Stimulated Reservoir Volume). Based on the nonlinear seepage characteristics of low permeability reservoirs, the coupling productivity equation of volume fracturing for vertical well in low permeability reservoirs is deduced. And the influence of the primary fracture conductivity, ESRV and the permeability of the matrix on the productivity was analyzed. The results show that the productivity increases with the increase of the primary fracture conductivity. The greater producing pressure drop, the greater the effect of the primary fracture conductivity on productivity. The larger the volume of ESRV is, the higher the productivity is. After the length of the primary fracture reaches a certain value, the stimulation effectiveness is not obvious. Pressure fractures and reservoir conditions must be matched in order to achieve the best yield.