Application of magnetotelluric sounding in the exploration of geothermal resources in Banqiao Sag of the Bohai Bay Basin, China

The Banqiao Sag possesses a substantial potential for geothermal resources, yet the geothermal geological research in this area remains limited. This study aims to explore the stratigraphic structure and subsurface fault distribution of the Banqiao Sag using magnetotelluric sounding (MT) method. In this method, two NE-SE survey lines were set up, comprising 39 measuring points with a total length of 9 km. After field data collection, processing, inversion and interpretation, three faults (including the major controlling Cangdong Fault) were identified and are basically consistent with the regional tectonic framework. Combined with the comparison of regional geological data, the strata are divided into the Quaternary, Neogene, Paleogene, Mesozoic, Paleozoic and Meso-Neoproterozoic from top to bottom, and the MT inversion results are basically consistent with the burial depths of the strata encountered in drilling. On this basis, two geothermal wells were designed and drilled to a vertical depth of 1630 m, yielding a water flow of 89 m 3 /h with a temperature of 51 °C. These results well verified the practicability and effectiveness of MT method in geothermal resource detection in Banqiao Sag of Bohai Bay Basin. • The improved for geothermal exploration of porous sandstone. • Adaptive regularization inversion method and the TM+TE mode were employed for two-dimensional inversion. • Prediction of the bottom boundary depths of each formation and drilling verification.