Abstract: A T-H-M (thermal-hydraulic-mechanical) coupling mechanical model considering the effect of thermal convection and thermal conduction is built to study the influence of fracture-network spacing on temperature of reservoir rock mass during water injection for HDR geothermal reservoirs. Taking the horizontal well with multiple-fracture-network geothermal development as an example, the fracture-network and its surrounding rocks are regarded as an equivalent porous medium, the coupling of H-M coupling and thermal convection is achieved by the secondary development of ABAQUS. The simulation results show that the temperature change of the reservoir rock mass falls into three stages during water injection:in the initial temperature maintaining stage, the rock mass temperature remains initial, and there is no effect of different fracture-networks spacings on the temperature of overall reservoir rock mass; in the temperature rapid declining stage, the temperature decline of the reservoir rock mass shows a negative exponential with the water injection time, and the fracture-network spacings are positively correlated with the temperature of reservoir rock mass; the third stage is the temperature slow and steady declining stage, at the beginning of this stage, the relationship between the fracture-network spacings and the temperature of reservoir rock mass are consistent with that in the temperature rapid declining stage, however, at the end of this stage, the fracture-network spacings are negatively correlated with the temperature of reservoir rock mass. In space, the smaller the fracture-network spacing, the greater the gradient temperature changes of reservoir rock mass in the area where rock mass temperature is high; while the smaller the fracture-network spacing, the smaller the gradient temperature changes of reservoir rock mass in the area where rock mass temperature is low.

Key words: hot dry rock geothermal reservoirs, thermal-hydraulic-mechanical coupling mechanical model, numerical simulation, fracture-network spacing