Page 300 - Geothermal Energy Systems Exploration, Development, and Utilization
P. 300

276  5 Geothermal Reservoir Simulation
                               The model couples mechanical deformation and alteration of fracture parameters
                               with state of the art fluid parameter functions dependent on pressure, temperature,
                               and salinity for heat capacity, conductivity, viscosity, and density. The effects of
                               the coupling on the reservoir productivity characteristics and potential reservoir
                               damage were investigated to assist in the identification of optimal heat recovery
                               schemes for the long-term economical operation. Preferential flow paths and
                               hydraulic short cuts dependent on the geomechanical and thermal stress release
                               behavior were predicted for overexploitation.

                               5.6.2.2 Development of Preferential Flow Paths due to Positive Feedback Loops in
                               Coupled Processes and Potential Reservoir Damage
                               The effect of the coupling of the processes investigated, led to systematic and
                               localized changes in the flow and transport characteristics, systematic in terms
                               of the progressive development of the phenomena and localized in terms of the
                               impact at specific locations. This led to the development of preferential flow paths
                               (Hicks et al., 1996; Su et al., 2001; Zheng and Gorelick, 2002) and geometrical
                                                         Flow            Plan view of
                                                                       dipole flow paths







                                                  Injection           Extraction


                                                                         Vertical slice
                                  3800
                                 Depth (m)  4000


                                  4200

                                     −400      −200        0       +200      +400
                                                      x direction (m)



                                          0    4     8   12     16  20   23
                                                Temperature difference (°c)
                               Figure 5.21  Hydromechanical coupling, the reservoir is
                               more permeable under the lower stress conditions at the
                               top of the reservoir than the higher stress conditions at the
                               base of the reservoir. (Please find a color version of this
                               figure on the color plates.)
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