Analysis of Fracture Parameters and Hydraulic Fracturing in an Enhanced Geothermal System Using Discrete Fracture Network Modeling
AuthorRashid, Harun Ur
Mining and Metallurgical Engineering
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An exploration for Enhanced Geothermal System (EGS) focuses on blind hidden reserves. As a result precise characterization and modeling of the subsurface formation at potential development sites are essential. Since EGS reservoirs have low matrix permeability, fractures often provide the only flow path between the injection and production wells. Therefore, the performance of an EGS is primarily defined by the generated fracture networks. A model was created using Golder Associate’s software FracMan@ with the data of a potential EGS site in Nevada. Then discrete fracture network (DFN) modeling was used to simulate sensitivity of hydraulic fracturing simulation, to compare three well patterns (conventional, loop-hole and micro-hole well patterns), to analyze the effect of stress on flow rate, to perform a hydro-mechanical coupling, and critical stress analysis and to study fracture twisting near the wellbore. The result from hydro-mechanical coupling showed that the conductivity of the system changes when it is subjected to differential effective normal stress. In addition, the permeability of the system was analyzed as a function of flow rate and differential stress conditions. Among the three studied well patterns loop-hole and micro-hole well patterns were more efficient for energy extraction than the conventional well pattern. Also, fracture pore pressure, the intensity of pre-existing natural fractures and the inclination of well trajectory also found to be critical in a hydraulic fracturing operation. This study provides a better understanding of the parameters that influence the performance of a fractured system and simulation designs of hydraulic fracturing. Moreover, this work aims to increase the efficiency of extracting energy from an EGS. This is achieved by providing a better solution to hydraulic fracturing, and well pattern selection. Furthermore, the findings will contribute to the improvement of resource extraction from other fractured systems like shale gas or oil reservoir. Lastly, the results will be helpful in carbon dioxide sequestration in a fractured reservoir.