A Two-Phase Rate Transient Analysis Method for Hydraulically Fractured Reservoirs with Different Fracture Geometries

Summary We developed a two-phase rate transient analysis (RTA) method for hydraulically fractured reservoirs, focusing on the evaluation of fracture parameters and the characterization of fracture dynamics across different fracture geometries. This method introduces a semi-analytical model that incorporates a shape factor to generalize the analysis from a single fracture geometry to various geometries, accounting for variations in fracture shape distribution and ensuring a more comprehensive representation of fracture characteristics. By accommodating different geometries, the model improves accuracy in permeability evaluation and enhances its applicability to various reservoir conditions. The model solutions under variable production conditions are derived using Duhamel’s principle. The accuracy of the two-phase flow model was validated by comparing the interpreted results of fracture pore volume (PV) and fracture permeability with the set values in a commercial numerical simulator. To demonstrate the advancement and applicability of our model, two field case studies are presented. First, a shale oil well from the Eagle Ford Formation was analyzed using both radial fracture model and linear fracture model. Subsequently, a tight oil well in China was evaluated by integrating microseismic data revealing an asymmetric two-wing fracture geometry, where production data were interpreted with a linear fracture model and an asymmetric fracture model. The results demonstrate that different fracture geometries yield minimal discrepancies in initial fracture volume estimates (variation <10%) but significant divergence in initial fracture permeability (>15% difference). The findings indicate that while the difference in fracture PV between the models is small, the fracture permeability varies significantly. This highlights the critical importance of selecting a model that accurately represents the actual fracture geometry to ensure precise permeability analysis. Unlike traditional RTA methods, which often assume a specific fracture geometry (e.g., rectangular fracture), this approach expands its applicability by accommodating various fracture geometries (e.g., radial, asymmetric two-wing, and rhombic). This advancement enhances the method’s practical relevance and offers theoretical insights for the development of unconventional oil and gas reservoirs. The model supports diverse fracture geometries, whereas existing two-phase flow analyses are limited to idealized rectangular shape. By incorporating shape factors, our approach significantly broadens applicability to different fracture geometries determined through comprehensive analysis of geological data, geophysical interpretations, and well location constraints.