Impact of reservoir characteristics on the well spacing of sandstone geothermal reservoir: A case study of Jiyang Depression

The reinjection exploitation of hydrothermal resources is a recognized method of sustainable exploitation. The well space between the production and reinjection well is an essential issue because the thermal breakthrough in production well is the main negative impact during reinjection. The migration of reinjection water in the geothermal reservoir depends on the permeability of the reservoir, constrained by the geothermal reservoir characteristics. In this study, A numerical model using the Petrasim software with Tough2, as the core as well as reservoir data of each typical geothermal field in Jiyang depression, was established. The impact of the reservoir porosity and permeability and the thickness of a single sand layer on the migration of reinjection water and temperature field in the geothermal reservoir were analyzed systematically. The simulation results revealed that the reservoir porosity had a minor impact on the reinjection of the geothermal reservoir, including the reinjection pressure and the spacing of production and reinjection wells. The reservoir permeability affected the reinjection pressure, and then controlled the reinjection performance of the geothermal reservoir, while it had no impact on the spacing of production and reinjection wells. The sand layer superposition combination had a minor impact on the reinjection pressure of the geothermal reservoir. The distance of the horizontal migration of reinjection water in the multilayer stacked thin sand layers was longer, and the range of temperature influence was larger. Thus, it is necessary to expand the well space between production and reinjection well. This study is of significance for the stable operation of geothermal development projects.