Research on deep geothermal resource exploration based on the wide field electromagnetic method: a case study in the Xuwen area

Abstract

Deep geothermal resources possess significant potential and promising application prospects, serving as an ideal supplement to the existing energy system. However, the exploration and efficient utilization of these resources remain challenging due to the complexity of subsurface geological structures and the limitations of conventional electromagnetic methods. This study addresses these challenges by presenting an innovative application of the Wide Field Electromagnetic Method (WFEM) for the exploration of deep geothermal resources in the Xuwen area. By strategically deploying four survey lines, the study collected comprehensive data, which were processed using advanced inversion techniques to derive resistivity cross-sections. These cross-sections provided fundamental insights into the subsurface electrical layer characteristics, revealing distinct geoelectric structure layers and the spatial distribution of granitic masses. The results clearly demonstrate that the resistivity cross-sections obtained through the WFEM distinctly outline the geoelectric-structure-layer framework of the 'Quaternary and Neogene – Paleogene, Cretaceous, and Paleozoic – basement granites' system. Additionally, these cross-sections accurately represent the geological structure characteristics of the Xuwen Bulge, Maichen Depression, Liushagang Bulge, Wushi Depression, and Qishui Bulge. Furthermore, the granites buried between 1800 m and 4900 m are mainly found in specific locations: along GY1 from station 0–8000 m and from station 18,000 to 51,000 m, along GY2 from station 6000 to 15,600 m, and encompassing GY3 and GY4. These findings provide a solid foundation for selecting favorable target areas for deep geothermal resources and strategically planning the locations for geothermal wells.