Two Basic Problems for Hot Dry Rock Reservoir Stimulation and Production

Abstract

A numerical analysis is made for heat extraction from a geothermal reservoir in a naturally fractured rock mass. We consider in particular two issues: long-term prediction of fluid temperature around a single fracture and the initial stages of fracture development in a naturally fractured rock. For the first problem, the evolution of outlet fluid temperature is considered as a function of time and injection rate. The rock temperature around a single fracture in the reservoirs is also calculated. The second problem is motivated by the fact that injection pressure is highly dependent on the details of fracture geometry near the borehole. High treatment pressure are associated with the formation of opening mode hydraulic fractures in naturally fractured rock and recent result that can explain the origin of these pressures are applied here to the problem of high injection impedance at pressures below the jacking pressure.