Stochastic modeling of fluid flow in the simulation and quantification of fracture initiation and propagation in the oil carbonate reservoirs during water injection

Abstract

Water injection into oil carbonate reserves can lead to fracture initiation and propagation, which can be modeled using a stochastic fluid flow model. Crack initiation and propagation due to water injection are investigated using numerical simulations in a carbonate oil reservoir. An accurate, comprehensive 2D model of fracture propagation can be created using stochastic Brinkman optimal control with uncertain inputs. Because fluid movement determines the spread of the oil front, we observed that fracturing was distinct from the spread of oil. Fracture tip oil saturation correlates strongly with saturation early on, showing that pressured oil is mostly filling up the fractures. An oil-filled gap has formed between the crack’s oil front and the crack’s top, which is later filled by reservoir gas. Additionally, a substantial volume of oil is seeping from the reservoir. Because of the discrepancy between the fracture volume and the volume of water injected into the fracture, a simple assumption that the fracture is saturated with pressured oil in the reservoir cannot accurately calculate the fracture length. Water injection is a set of many failure processes in which pressure consistently drops when the failure occurs, but the fluctuation decreases as the fracture length increases, so we identify pressure fluctuation under constant water injection (for pushing oil in Enhanced Oil Recovery methods) to illustrate flow-geomechanical responses.