Depletion-induced stress change in a hydraulically bounded reservoir with multistage fractured horizontal wells

Multistage fractured horizontal wells (MFHW) in unconventional reservoirs usually experience long transient flow period and sharp production decline. Poroelastic effects have significant impact on the in-situ stress state. Field observations have confirmed stress evolution as pore pressure changes during production. However, measured data could only reveal the induced stress change phenomenon but are limited to systematically characterize the spatio-temporal stress evolution. In the development of unconventional reservoirs with MFHW, theoretical models of predicting the depletion-induced stress change become important to optimize enhanced oil recovery (EOR) planning and prevent fracture closure with proper completion design. This paper proposes a boundary element method (BEM) to simultaneously model transient fluid flow and the induced stress change of MFHW in a hydraulically bounded reservoir with no flow boundaries. Benchmarking is performed by comparing this work with analytical solutions available in linear poroelasticity and well-known commercial software in well testing. Modeling results show that production from the MFHW reduces pore pressure and the total compressive stress. The depletion-induced stress components on fractures show transient characteristics which are consistent with the linear, transitional, radial, and boundary dominated flow regimes commonly identified in well testing. Effects of fracture properties and fracture interference on the spatio-temporal stress evolution are clearly shown on the log-log plots of derivative responses of depletion-induced stress components versus time. The stress path (Δσh/Δp), which describes the induced minimum horizontal stress per unit pore pressure change monitored at the well, shows characteristic trends over time on the modeling results. The typical stress path monitored at the well may change with time and become non-linear with pore pressure change.