Transport mechanism of temporary plugging agent in complex fractures of hot dry rock: A numerical study

Abstract

Hydraulic fracturing with temporary plugging agents is one of the most promising technologies to improve the thermal efficiency of deep geothermal reservoirs. Understanding the migration and plugging mechanism of temporary plugging agents in artificial fractures is the key to successful fracturing operations. However, there is currently a lack of understanding of the high temperature effect on the migration of temporary plugging agents in fractures. Therefore, based on the Eulerian-Lagrangian description framework, this paper uses the computational fluid mechanics (CFD)-discrete element method (DEM) two-way coupling algorithm to establish a multiphase flow model for the migration of temporary plugging agents in complex fractures. We carried out relevant numerical simulation research and compared with the experimental results. Numerical simulation results show that the main factors affecting the migration of temporary plugging agent include formation temperature, fracture complexity, viscosity of carrier fluid, mass concentration of temporary plugging agent, flow regime of the carrier fluid, and inter-particle friction coefficient. Among these factors, the high temperature effect reduces the amount of temporary plugging agent entering complex branch fractures, thus weakening the plugging efficiency of temporary plugging agent for branch fractures. However, the adverse effect of high temperature on plugging can be overcome by increasing the injection rate of temporary plugging agent and increasing the width of the fracture to improve the plugging efficiency of branch fractures. The numerical results provide important theoretical and practical significance for the design scheme of temporary plugging and diverting fracturing in hot dry rock.