Numerical Analysis of Permeability Changes for Clogging and Microcracks Induced by the Invasion of Fracturing Fluid

Abstract

Summary Hydraulic fracturing can produce a main fracture and increase flow efficiency. It can also result in the invasion of fracturing fluid, which can produce clay swelling. The invasion can block the pores and throats in the porous media and damage matrix permeability, while it can also induce microcracks under certain conditions. This study developed a numerical model to evaluate the permeability change induced by the invasion. Both pore-throat clogging and microcracks are integrated into the model. The numerical model coupled a flow model based on the pore-scale network method (PNM), a solid model, and a permeability evaluation model. The solid model and permeability evaluation model are based on our microcrack performance model reported previously. We validated the flow model by analytical results and the coupled model by previous experiments of the soaking test. Simulation results show that the invasion can decrease the permeability for the clogging effect and increase the permeability for the microcrack generation. The generation of microcracks can greatly increase the permeability even with the clogging effect for clay swelling. Our simulation results indicated that rock properties can affect the effect of clogging and microcracks on permeability. This study provides an approach for the selection of fracturing fluid and the design of fracturing fluid flowback. This is crucial for the understanding of the invasion on permeability and can serve as a guide for fracturing operations.