SOTEM exploration and reservoir structure analysis of Yangbajain geothermal field, Xizang

The Yangbajain geothermal field in Xizang is a worldwide famous high-temperature geothermal field, and has been explored and exploited for more than four decades. Unfortunately, the shallow geothermal resources are gradually exhausted, thus it's urgent to explore deep high temperature geothermal resources for geothermal power generation or increasing installed capacity. It's well known that comprehensively understanding the distribution of faults and the upwelling channels of geothermal fluids are of great value for exploiting the deep high-temperature geothermal resources. Therefore, we have carried out the short-offset transient electromagnetic (SOTEM) explorations with six survey lines in Yangbajain geothermal field, and further obtained the electrical structures within the depth of 2 km by analyzing the inversion profiles. Combined with the currently existing cognition of the structural geology, geophysics, geochemistry and drillings, we got some brand-new understandings as follows. Firstly, fault F14 is the main channel for geothermal fluid migration from the north to the south of the geothermal field. Secondly, the upwelling channel of deep geothermal fluid appears in the sulfur ditch in the north while the underlying basement with poor permeability near the China-Nepal Highway blocks the lateral flow of the deep geothermal fluid from the north to the south. Thirdly, there is a low-resistance in the deep part of the south area, gathering atmospheric precipitation and ice snow melt water from Tang Mountain, and has weak connection with the existing shallow thermal reservoir. Finally, it's difficult to effectively take measures to maintain the thermal storage pressure and extend the exploitation period of geothermal field in the south of the geothermal field.