عنوان مقاله [English]
Hot Dry Rock geothermal reservoirs differ considerably from conventional geothermal reservoirs which exist only in the geologically privileged regions. In fact, HDR reservoirs are artificially created reservoirs which can be considered at any accessible depth of the Earths crust with a suitable volume of hot dry rock. One of the main characteristics of HDR reservoirs is enough permeable paths to allow water flow in the region between injection and production boreholes. Hydraulic stimulation is a technique employed to create these permeable paths in such regions. A pair of wells is drilled into the rock, terminating several hundred meters apart. Water is circulated down the injection well and through the HDR reservoir, which acts as a heat exchanger. The fluid then returns to the surface through the production well and, thus, transfers the heat to the surface as steam or hot water. Knowledge of the shape, size and permeability of the fractured zone created by stimulation is important for assessment of the feasibility of the project and determination of the optimum relative locations of the injection and production borehole. Improving permeability allows the system to reduce its hydraulic resistance. This operational hydraulic parameter, which is called impedance, measures the pressure amount required to force water at unit flow rate through the reservoirs. Another important parameter called the water loss rate is the difference between the rates of water injected and produced. Since stimulation experiments conducted at great depths are very expensive, numerical modeling can play a significant role. In this research, the hydraulic and mechanical response of jointed rock mass in a HDR reservoir is treated under high pressure hydraulic injections using a distinct element code. The code is capable of considering Hydro-Mechanical coupling. A parametric study on different joint specifications is carried out to illustrate how the impedance and water loss rate are varied.