A semi-analytical water content model for pressure transient analysis of fractured horizontal well with complex fracture networks

Due to the tiny pore structure and dense lithology of tight oil reservoir, many complex fracture networks are generated during fracturing operation. The fluid flow behavior in the complex fracture networks is complicated due to the variation of water content in the formation and fracture networks. Therefore, it is critical important to propose well test models characterizing the fluid flow in the complex fracture networks. Based on the assumption of orthogonal fracture networks, we developed a novel semi-analytical water content model to predict the pressure transient behavior of the fractured horizontal well. The water content in complex fracture networks and formation system, the finite conductivity of fractures and fracture interferences were considered in the model. Results show that the pressure curves of the proposed model add two stages including the fluid feed flow period and the pressure interference period compared to the conventional fractured horizontal well with single vertical fractures. Main fracture conductivity mainly influences the fracture linear flow period and the feed flow period of the pressure curves. The secondary fracture conductivity has major effect on the stage of the fluid feed capacity from the secondary fractures to the main fractures. The water content in reservoir system mainly influences the linear flow period and pseudo radial flow period in the formation system, while the water content in fracture system has major effect on the fluid feed flow period of the curves. The main fracture length mainly influences the fracture flow stage and formation linear flow stage of the pressure curves, while the secondary fracture length mainly influences the fluid feed flow stage and the fracture pseudo radial flow stage of the pressure curves. This study provides guidance for the development and dynamic monitoring of fractured horizontal well with water content varying in the fracture networks and formation.