Coupled geomechanics and compositional fluid flow modeling for unconventional oil and gas reservoirs

The integration of geomechanics with multi-phase, multi-component fluid flow in porous media has several applications in the upstream oil and gas industry. It can be applied for both near wellbore and reservoir scale problems in different reservoir types. The development of a 3D geomechanics and compositional flow model coupled with fracture growth capability is presented. The partial differential equations in the reservoir, fracture and well domain are solved in a coupled manner. The model is validated/verified for different physics such as fracture growth, stress around a fracture and well, phase behavior, multiphase flow, compressible flow and poroelasticity. The model is then applied to problems specific to low permeability shale and tight reservoirs, however, the model is very general and can be applied to any subsurface hydrocarbon or water reservoir. Propagation of multiple fractures using different fluids such as slickwater, gases and foams is studied using field scale examples. The impact of variables such as fluid compressibility, viscosity, wellbore volume, reservoir permeability, stress/tensile strength ratio, and poroelasticity on fracture geometry, breakdown and shut-in behavior is investigated in detail. Production from a well and the resulting stress changes are calculated in dry gas, gas condensates, black oil and volatile oil reservoirs. Permeability changes associated with an increase in effective stress on fractures and reservoir rock are shown to have a significant impact on decline rates. The impact of water evaporation and subsequent salt precipitation on productivity in shale gas reservoirs is evaluated. A sensitivity study is performed for variables such as capillary pressure, fracture spacing, reservoir permeability, initial brine saturation, reservoir temperature and well operating BHP. A method of fluid injection (water or gas) in depleted parent wells (known as pre-loading) to minimize damage due to frac-hits is studied. The stress and pressure changes due to fluid injection are shown to be dependent on injection fluid and reservoir fluid type, injection rates and the fracture geometry in parent wells. The compositional and geomechanical effects in a Huff-n-Puff gas injection IOR process in tight oil reservoirs are investigated. The additional recovery and increase in GOR after several Huff-n-Puff cycles is shown to be a function of reservoir and injected fluid composition and hysteresis in permeability as a function of effective stress.