Study on the migration characteristics of temporary plugging agents in hot dry rock fractures considering ambient temperature field variations

An enhanced geothermal system (EGS) is a crucial method for extracting geothermal resources. Enhancing the efficiency and recovery capacity of EGS hinges on the essential use of temporary plugging and diversion fracturing technology. Consequently, studying the migration patterns of temporary plugging agents within hot dry rock (HDR) fractures is crucial. However, existing research on the movement of temporary plugging agents in HDR fractures often neglects the influence of ambient temperature changes. These variations significantly impact the degradation and migration of particles. This study uses computational fluid dynamics and the discrete element method to analyze how changes in the ambient temperature field affect the temperature within fractures and the movement of temporary plugging agents. The study introduces three dimensionless numbers: dimensionless temperature change T, dimensionless time t, and dimensionless position X, to evaluate the migration behavior of temporary plugging agents. It also explores the effects of temporary plugging fracturing fluid injection rate, viscosity, and branch fracture structure on the migration of temporary plugging agents. Results indicate that when t = 2 and X = 1, the temperature change T without considering HDR temperature field changes is 13.55%; with temperature field changes, T is 7.44%, resulting in a simulation difference of 82.12%; Within the simulation parameter range, as the injection rate of temporary plugging fracturing fluid increases, the dimensionless temperature change T decreases; as the viscosity of temporary plugging fracturing fluid increases, the dimensionless temperature change T initially decreases and then stabilizes; the branch fracture structure has a great influence after the branch.