Integrated Fracture and Reservoir Model for Well Spacing Optimization in Unconventional Reservoirs With 3D Natural Fractures

Abstract

This study presents a new workflow by integrating a robust 3D hydraulic fracture propagation model in conjunction with reservoir simulation through the embedded discrete fracture model (EDFM). Specifically, the hydraulic fracture model is applied to simulate more realistic fracture geometry considering 3D geomodel with rescue format and 3D natural fractures. Multiple wells with varying well spacing are considered. After fracture simulation, the predicted hydraulic fractures, activated natural fractures, and non-activated natural fractures are easily transferred to the reservoir simulator. The EDFM method can accurately and efficiently deal with the 3D complex fractures. It can avoid the complex gridding process and low computational efficiency of the traditional local grid refinement method. Based on long-term performance of different scenarios with varying well spacing, the optimal well spacing is determined. The new workflow was applied to optimize well spacing in a real shale gas case with 3D geomodel and natural fractures. The geomodel with rescue format, 3D natural fracture, 3D non-uniform distribution of stress and rock properties are all honored in the fracture model. Two horizontal wells with varying well spacing of 200 m, 300 m, and 400 m with actual completion data were considered and simulated. Subsequently, the same reservoir and fracture model was used to perform production simulation for 20 years. The distribution of heterogenous properties in matrix was considered. By comparing the estimated ultimate recovery of different well spacing scenarios, the optimal well spacing was identified. This work, for the first time, performs well spacing optimization by coupling fracture model and reservoir model considering more realistic geomodel and fracture system. This new workflow significantly improves the accuracy and efficiency of well spacing optimization process in unconventional oil and gas reservoirs compared to the traditional workflow presented in the literature.