Injection strategies in an enhanced geothermal system based on discrete fractures model

In this investigation, injection and recovery strategies are studied in order to improve the performance of an Enhanced Geothermal System with multiple fractures. The three-dimensional heterogeneous reservoir intercepted by three inclined discrete fractures is modeled under transient conditions with the finite element method. Numerical results show that the produced fluid temperature and the extracted heat are affected, the fluid flows through preferred paths and the premature thermal breakthrough is avoided. The produced fluid temperature increases slowly the first 9.8 - 20.1 years according to the considered scenario and decreases with the production time. Under the conditions in this paper, the best performance is obtained by injecting the fluid in the fourth layer of the reservoir over 100 m. For a volumetric flow rate of 1501/s and a fluid injection temperature of 60 degrees C, a better option is obtained for an average electrical power of 9.66 MWe and the reservoir flow impedance is 0.222 MPa/(kg/s). The average production temperature after 40 years of operation time is 166 degrees C, it is thus reduced by 1.13%, which is acceptable. The sensitivity analysis of fracturing parameters indicates that the increasing of the fracture aperture leads to the decrease of the effective electric power.