Application of Composite Models in Low-Permeability Unconventional Reservoirs Stimulated by Hydraulic Fractures: Considering Coupled Heterogeneity-Geomechanics-Sorption-Rarefied Flow Processes

Low-permeability unconventional formations (including tight sandstone and shale formations) are rising geological candidates for hydrocarbon recovery with and without carbon sequestration. Horizontal wells coupled with multiple hydraulic fracturing treatments are widely applied to increase the fluid extraction out of or injectivity into low-permeability formations. In addition to hydraulic fractures, formation heterogeneity, formation and hydraulic fracture stress-sensitivity, gas sorption kinetics and rarefied flow all have significant influences on the fluid flow and transport in unconventional formations. Numerical modelling of these coupled processes suffers from non-convergence problems and high computation cost. In this study we developed a semi-analytical composite methodology-dividing the formation into elementary regions, modelling coupled process in each region and coupling the results of regions for final formation-scale models. The composite methodology is advantaged in fast calculation and full consideration of aforementioned processes. We constructed various composite models with different process parameters and created type curves of fluid rates (of fractured horizontal wells) vs. time. We applied type curves to match production data of fractured horizontal wells and estimated unknown information of hydraulic fractures, formation stress-sensitivity and formation permeabilities.