Depletion caused by the production of parent wells in shale oil reservoirs leads to pressure and stress changes. These changes can result in interwell interference between parent wells and subsequent infill wells. The effect of faulted zones on these changes has not been thoroughly quantified in previous studies. This study employs a coupled flow and geomechanics model based on finite element methods. It also considers the existence of a reverse fault zone. The model is validated with an analytical solution to the reservoir compaction problem. Depletion-induced pressure and stress changes in the hanging wall, in the footwall, and in the faulted zone are calculated. Subsidence, stress, induced stress change, and reorientation of the principal stress are also quantified and discussed. The effect of depletion on the stability of the fault is quantified as well. Results show that the stress anomalies prior to depletion can inhibit the legacy production-induced stress evolutions, and the permeable faulted zone can also facilitate the porous media flow and the induced mechanical responses. The study can provide a reference for the understanding of depletion-induced pressure and stress changes in faulted shale oil reservoirs and for the determination of candidate infill well locations.
Infill well drilling and fracturing have become a key strategy in the development of shale oil reservoirs worldwide. Before the drilling and fracturing of infill wells, legacy production in parent wells usually alters stress fields in payzones, and these depletion-induced stress changes in shale oil reservoirs are closely related to frac hits and interwell interference in shale oil reservoirs, which largely affect the efficiency of infill well development. In shale oil reservoirs with the presence of geological structures such as faults, the stress evolution and its effect on infill well fracturing can become more complicated, since the presence of faults can increase the heterogeneity in stress fields and faults can be more permeable than the rock matrix. To better understand the stress evolution and infill well fracturing mechanisms in faulted reservoirs, it is important to characterize the in-situ stress states in faulted regions and to quantify the stress evolution caused by depletion.