A Discrete Model for Pressure Transient Analysis in Discretely Fractured Reservoirs

Abstract

Summary Natural fractures are of great significance to the management of petroleum resources, groundwater, and carbon sequestration. Given that many naturally fractured reservoirs have poorly connected fractures, the traditional dual-porosity model like Warren and Root’s model is not reasonable for pressure transient analysis in these reservoirs. Therefore, the objective of this study is to develop a new discrete model (DM) in discretely fractured reservoirs based on a semianalytical approach. The DM comprises three domains: wellbore-connecting (WC) fractures and/or wellbore-isolating (WI) fractures, and matrix. The DM is verified by case studies with numerical simulators for four kinds of discretely fractured reservoirs with (1) WC fracture networks, (2) WI fracture networks, (3) WC and WI fractures, and (4) WI fractures. Results indicate that the pressure transient behaviors in discretely fractured reservoirs can be classified into three types: WC fracture networks, WC and WI fractures, and WI fracture (networks). The special flow regimes of WC fracture networks are fluid supply and pseudoboundary dominated flow. For WC and WI fractures, the special flow regimes are bilinear flow, linear flow, and isolated fracture effect. The early pseudoradial flow and isolated fracture effect (“V-shaped” or “dip”) are the special flow regimes of WI fracture (networks), and they are similar to traditional dual-porosity models like the Warren and Root model. However, the source of “V-shaped” in DM is quite different from that in the Warren and Root model. This paper gives a new insight into the well testing in discretely fractured reservoirs.