A review on geothermal wells: Well integrity issues

Geothermal energy is an important potential and a strategic area for developing activities regarding renewable energy and future studies. It involves a great potential and a main role in the worldwide energy sector, particularly electricity generation. Nevertheless, the role of geothermal electricity in today's world is not dominant in comparison to other renewable energy sources like solar PV and wind power. Though Enhanced Geothermal Systems (EGS) greatly includes the potential for power generation, the EGS technology feasibility should be further studied. Numerous studies exist to investigate the energy production feasibility (heat and electricity) from such resources focusing on drilling processes. Today, the geothermal projects are mainly focused on completion operations and drilling research area, in which it is possible to reduce the costs considerably by suitable design. To drill a geothermal well, the drilling operations are quite similar to the petroleum industry. Though, the different aspects of geothermal drilling will make it more challenging and complex than the oil and gas well drilling. The type of resource and the formation type of resource is the big differences. Normally, fissures and fractured hard volcanic rocks contain geothermal resources, however, porous media of sedimentary formations comprises oil and gas resourses. Petroleum and geothermal well drilling have different geological and physical features including rock types, reservoir pressure, temperature, well and casing design as well as the well completion program. Hence, in this paper, it is tried to present the most common issues in geothermal well drilling operations and to introduce the potential for the future research areas. (C) 2020 The Author(s). Published by Elsevier Ltd.