致密气藏多段压裂水平井非稳态复合产能模型

Transient and compound productivity model for multi-fractured horizontal well in tight gas reservoir

根据致密气藏压裂后的地质特征,将致密气藏分为压裂区和未压裂区,压裂区为三重孔隙结构,未压裂区为双重孔隙结构;建立了致密气藏多段压裂水平井产能复合计算模型,通过拉普拉斯变换求解得到了多段压裂水平井产能计算公式,绘制了典型无因次产量曲线;通过新旧模型对比,分析了未压裂区对产能的影响,并对相关参数敏感性进行了分析。实例计算表明:流体流动可划分为人工裂缝中线性流动、人工裂缝和压裂区天然裂缝系统双线性流动、压裂区基质系统单线性流动、未压裂区基质和裂缝双线性流动、未压裂区基质控制线性流动、边界控制流动等6个阶段;无因次产量qD随参数ξ(渗透率比)及η(裂缝导流能力比)减小而增大,参数η值越小,未压裂区基质控制线性流动时间越长,边界流出现时间越晚。

Based on the tight gas reservoir geological characteristics after fracturing, the tight gas reservoir is divided into unfractured zone and fractured zone, fractured zone is regarded as the triple medium and unfractured zone is regarded as the dual medium. A new composed productivity calculation model for multi-stage fractured horizontal well in tight gas reservoir has been established to analyze the productivity characteristics of tight gas reservoir. The typical curve of normalized production versus normalized time has been figured and the new model has been compared with the old model to analyze the effects of unfractured zone on the productivity, and the sensibilities of different parameters have also been analyzed. The results show that the fluid flow can be divided into six stages： linear flow in artificial fracture, bilinear flow in natural fracture and fractured zone, single linear flow in matrix system of fractured zone, bilinear flow in matrix and fracture of non-fractured zone, linear flow controlled by the matrix system of non-fractured zone and the boundary flow. Normalized production qDincreases with the decrease of ξ and η. The smaller the parameter value of η is, the later the linear flow time controlled by the matrix system of non-fractured zone is. Meanwhile, the time of the boundary flow delays for the smaller η.