Structural Features of Geothermal Field from Magnetotelluric Survey in Northern Central Region of Vietnam

Abstract

The first result of Magnetotelluric survey for geothermal investigation in Vietnam is conducted in 2013 and presented. The fifteen MT data collected mainly between 0.001-5000 Hz by MTU 2000 equipment is of useful quality and provides good control on the surface layers in two high hot water 75-105◦C areas Bang (Quang Binh province) and Da Krong (Quang Tri province) belong Northern-Central region of Vietnam. It means that reliable modeling should be possible to a depth of 10,000 m depending on resistivity distribution. The data was processed and modeled using an improved modeling method by WinGlink software. The resulting 1D and 2D models show a high–very low–very high resistivity sequence with depth. The second layer is a very conductive layer distributing at a depth range from 1.2 – 3.5 km and is interpreted as the reservoir that has thermal convection and hot fluids contained in its fractures and pores. The resistive basement is a hot and solid magmatic intrusion and is interpreted as a heat source that produces a conductive heat flow towards the reservoir. As a result, the shallow resistivity model of the areas is in a good correlation with the geological features. This result allows explain the common conceptual resistivity model which has been presented for the geothermal reservoirs.