A high-resolution numerical well-test model for pressure transient analysis of multistage fractured horizontal wells in naturally fractured reservoirs

Abstract

In this study, a high-resolution numerical well-test model based on hybrid discrete fracture methods for pressure transient analysis of multistage fractured horizontal wells in naturally fractured reservoirs is proposed. Given the complexity of gridding for a numerical transient model, a new type of hybrid grid system honoring complex geometries of high-velocity transient flow near wellbore and hydraulic fractures is developed. Meanwhile, the methods of identifying fracture intersections in 3D unstructured space, transmissibility corrections and stochastic fracture network generation algorithm are proposed to greatly improve the accuracy and efficiency of capturing the pressure transients in complex fracture networks. After comparison with the well-test software KAPPA, it shows that the model can not only accurately reproduce the complex 3D convergence of flow regimes but also has a much better computational performance. Then, the type curves of a multistage fractured horizontal well with complex fracture networks and the sensitivity analysis of nonuniform properties of fracture networks are developed and analyzed in detail. The results show that the early-time horizontal radial flow and dip are positively related to the properties of natural fractures, and the fluid contribution and pressure distribution mainly depend on fracture connectivity rather than fracture number. The orthogonal fracture connections can result in stronger fluid supply and less fracture interference. Besides, the fracture linear flow and first/second bilinear flow are mainly affected by hydraulic and natural fractures, respectively. Finally, it proves that the proposed model can be much more efficient than KAPPA in history match for well-test data by an actual fractured field case.