缝洞型油藏斜井三孔双渗试井分析模型

Tri-Porosity and Dual-Permeability Well Test Analysis Model for Inclined Wells in Fractured-Vuggy Reservoirs

缝洞型油藏的基质、裂缝和溶洞之间存在流体窜流,且基质和裂缝同时向井筒供给流体,假设油藏顶底不渗透、侧向无穷大、储集层水平等厚,建立了斜井试井分析理论模型。利用拉普拉斯变换、分离变量等方法得到了拉普拉斯空间下的试井模型解析解,通过Stehfest反演获得了井底压力解。利用受模型参数控制的试井分析样版曲线,开展了流动阶段识别及曲线敏感性分析。典型的斜井三孔双渗试井样版曲线反映出早期径向流阶段、线性流阶段、溶洞向裂缝窜流阶段、溶洞向基质及基质向裂缝窜流阶段等8个主要的流动阶段。井斜角、裂缝与储集层渗透率比等参数取值对试井样版曲线特征影响显著。

In fractured-vuggy reservoirs,there is cross flow between the matrix,fractures and cavities,and the matrix and fractures supply fluid to the wellbore at the same time.Assuming that the reservoir is horizontal,equal in thickness,impermeable at top and bottom,and infinite laterally,a theoretical model of well test analysis for inclined wells was established.The analytical solution of the model in the Laplace space was obtained by means of Laplace transform and variable separation,and the solution of the bottom hole pressure was obtained through Stehfest inversion.Type curves controlled by model parameters for well test analysis were used for flow stage identification and curve sensitivity analysis were conducted.The tri-porosity and dual-permeability well test type curves of inclined wells reflect 8 main flow stages,including early radial flow stage,linear flow stage,cavity-to-fracture cross flow stage,cavity-to-matrix cross flow stage and the matrix-to-fracture stage,etc.The values of parameters such as inclination and fracture-reservoir permeability ratio obviously influence the characteristics of the well test type curves.