STATE OF THE ART OF GEOTHERMAL ENERGY SYSTEM ENHANCEMENT: A LITERATURE REVIEW

Abstract

The application of hydraulic fracturing in geothermal reservoirs requires the con- sideration of aspects related to temperature, geology, and in-situ stresses. This research com- pares the application of hydraulic fracturing for geothermal purposes in Rotliegend sand- stones of sedimentary origin in the North German Basin with that of a Granodiorite reservoir in the Pohang site in South Korea. Furthermore, some recommendations are proposed for the application of hydraulic fracturing in Ecuadorian plays for thegeneration of geothermal en- ergy. The basement reservoirs have a hard structure and are prone to pre-existing natural fractures, especially in reservoirs for geothermal purposes, because they normally have active tectonism due to their location. In contrast, sedimentary reservoirs are not necessarily in areas with active tectonism and their more ductile structure does not make them prone to natural fractures, but their temperature gradient should be analyzed to verify their feasibility. The stress analysis, the coefficient of fracture conductivity (FCD), the Folds of Increase (FOI) and the temperature gradient are complementary factors for determining the economic via- bility of geothermal reservoirs. Consequently, the application of hydraulic fracturing in geo- thermal reservoirs requires the analysis of Sv (overburden) stress, Sh1 (horizontal 1) stress, Sh2 (horizontal 2) stress, temperature, FCD, and FOI. This is particularly true for the Chachimbiro Ecuadorian geothermal reservoir, where there is high temperature and active tectonism.