Discrete-Element-Method/Computational-Fluid-Dynamics Coupling Simulation of Proppant Embedment and Fracture Conductivity After Hydraulic Fracturing

Abstract

Summary In this paper, an integrated discrete-element-method (DEM)/computational-fluid-dynamics (CFD) numerical-modeling work flow is developed to model proppant embedment and fracture conductivity after hydraulic fracturing. Proppant with diameter from 0.15 to 0.83 mm was modeled as a frictional particle assembly, whereas shale formation was modeled as a bonded particle assembly by using the bonded-particle model in PFC3D (Itasca Consulting Group 2010). The mechanical interaction between proppant pack and shale formation during the process of fracture closing was first modeled with DEM. Then, fracture conductivity after the fracture closing was evaluated by modeling fluid flow through the proppant pack by use of DEM coupled with CFD. The numerical model was verified by laboratory fracture-conductivity experiment results and the Kozeny-Carman equation. The simulation results show that the fracture conductivity increases with the increase of proppant concentration or proppant size, and decreases with the increase of fracture-closing stress or degree of shale hydration; shale-hydration effect was confirmed to be the main reason for the large amount of proppant embedment.