Numerical simulation of seepage and heat transfer in single fractured rock mass of geothermal reservoirs

Abstract:

Study of the percolation and heat transfer in fractured rock mass of geothermal reservoirs is of great significance to the exploitation of geothermal resources in hot dry rocks. In this paper， based on a hot rock dry geothermal project， the numerical simulation software of COMSOL Multiphysics is used to study the mechanism of seepage and heat transfer in single fractured rock mass of geothermal reservoirs， with analysis made of the influence of fluid injection velocity and temperature on the temperature field of rock mass and on the geothermal project of hot dry rocks. It is found that the influence of fluid parameters on the rock mass temperature field is mainly reflected in two aspects： influence on the disturbed region and amplitude of the rock mass temperature field， and influence on the time needed for the rock mass temperature field to reach the steady state. Increase of the fluid injection rate will reduce the system service life and the total outlet normal heat value during the service life. When considering the total outlet normal heat flux， there exists an optimal fluid injection rate， which is 0.011m/s in this study. Increase of fluid injection temperatures will increase the service life of the system and the total normal heat flux and total heat at the system outlet. This study provides a theoretical basis for the development and utilization of hot dry rock self-heating resources and a reference basis for the design of engineering operation parameters.

Key words:geothermal reservoir;single fracture;seepage and heat transfer;fluid parameters;numerical simulation;hot dry rock development