Simulation of Fracking Fracture Cleaning as Oil Is Displaced from the Fracking Fracture Region

Abstract

this paper studies oil displacement from a porous reservoir with water. It is assumed there is a fracking fracture near the production well. It is known that as a viscous fluid is displaced by a less viscous fluid, the Saffman–Taylor instability occurs: the less viscous fluid breaks through the layer of the fluid being displaced, forming so-called “viscous fingers” (channels). After such a channel is ruptured and connected to a production well, the oil quality (i.e., the fraction of hydrocarbons in the production fluid) deteriorates dramatically. The paper describes the simulation and numerical modeling of viscous fluid unstable displacement from a porous medium. The displacement is modeled with Darcy’s law also considering capillary effects. The Brooks–Corey model is used to estimate the relative phase permeabilities. A fracking fracture is modeled as an area with elevated porosity and permeability. We consider the fracking fracture cleaning from the fracking fluid: a reservoir area filled with fracking fluid around the fracture is modeled; then the fluid is displaced with lower viscosity oil. The process is unstable and the displacement is uneven, so some of the fracturing fluid may remain inside the reservoir.