Productivity Analysis of Fractured Wells in Low -permeability Naturally Fractured Reservoirs

By using the elliptical flow model and the law of mass conservation, this paper presents a mathematical model for transient flow of a well with a finite-conductivity vertical fracture in low-permeability naturally fractured reservoirs. Effects of threshold pressure gradient are considered. Type curves of productivity performance are generated. Effects of threshold pressure gradient, storage capacity ratio, interporosity flow parameter, fracture conductivity and skin effect are analyzed. From the analysis of the result, it is shown that the type curve of productivity performance can be divided into three different flow regimes, fracture's flow regime, interporosity's flow regime and system's radial flow regime. The bigger the threshold pressure gradient is, the lower the productivity is. The bigger the storage capacity ratio is, the higher the productivity is. The bigger the interporosity flow parameter is, the earlier interporosity flow happens. The bigger the fracture conductivity is, the higher the productivity is. The worse the skin effect is, the lower the productivity is. Finally, the application to a vertically fractured well in low-permeability naturally fractured reservoirs is demonstrated. This will significantly improve our understanding of the productivity performance of fractured wells in low-permeability naturally fractured reservoirs.