Production analysis of multifractured horizontal wells with composite models: Influence of complex heterogeneity

Multi-linear analytical models are of high computational convenience to simulate the fluid production out of low-permeability unconventional (tight and shale) reservoirs stimulated with multifractured horizontal wells (MFHWs). But multi-linear models cannot accurately describe the flow behavior in such reservoirs since the fluid flow around hydraulic fracture tips is not linear flow. This creates barriers for the multi-linear models to consider pressure/stress-dependent fracture and reservoir characteristics. In addition, multi-linear models in the literature cannot consider or fully consider heterogeneity conditions including the reservoir heterogeneity and well completion heterogeneity. In this study, a composite model is developed to model the fluid flow in unconventional reservoirs with MFHWs under various heterogeneity conditions. In the composite model, the reservoir is divided into sub-systems and each sub-system is further divided into flow regions. The fluid flow in one flow region can be simply linear, radial or source/sink flow. The composite model considers the pressure/rate distribution characteristics beyond fracture tips with fast calculations. The composite model is applicable to one or combinations of the following three heterogeneous conditions-fractured horizontal wells with heterogeneous completions, reservoir heterogeneity around the horizontal well and reservoir heterogeneity around a hydraulic fracture. The model's applicability in heterogeneous reservoirs is demonstrated by the comparison with the trilinear-flow model, five-region model and numerical solutions. In this study solutions of the composite model are utilized to analyze two sets of production data from fractured horizontal wells in heterogeneous conditions.