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 subsystems 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.