Three-dimensional audio magnetotelluric imaging of the Yangyi geothermal field in Tibet, China

Abstract

The Yangyi geothermal field in southern Tibet has enormous potential for geothermal energy development. It is the high-temperature geothermal field at the highest elevation in the world, and the second largest high-temperature geothermal field in China. The total planned installed capacity of the geothermal power station is 32 MW. At present, no detailed three-dimensional (3D) geophysical survey has been carried out in the Yangyi geothermal field, and in-depth research is urgently needed. The main goal of our geophysical exploration is to study the geothermal structure of this region. In this study, the audio magnetotelluric (AMT) data of 85 stations were collected in the Yangyi geothermal field. The average distance between the stations was about 500 m, and the dimensions of the exploration area were 6 × 7 km. First, we analyzed the magnetotelluric data using the phase tensor method to qualitatively estimate the dimensionality of the subsurface resistivity structure. Then, by performing 3D inversion of 85 AMT data with relatively high quality, the 3D resistivity model from the surface to a depth of 2 km was determined, the high-temperature hydrothermal system under the Yangyi geothermal field was displayed for the first time. In addition, the main characteristics of the geothermal system were identified, and the genetic mechanism of the geothermal system was discussed based on the geological information and borehole data.