Integration of Seismic, Gravity and MT Survey for Geothermal Exploration

Abstract

Geothermal is a sustainable, clean and renewable source of energy. This energy is available round the clock with no pollution. With the increasing use and demand of energy around the world Geothermal emerges as a solution in terms of renewable form of energy. Naturally erupting geothermal resources are seen around the world which can be made of use as a source for generation of energy such as electricity. Exploration methods are necessary to understand the subsurface structures, possibilities of a geothermal reservoir and pin pointing the best possible spot for exploiting the geothermal source. In India Dholera, Unai and Gandhar are found to be the probable prospects for geothermal energy. This report deals with the exploration aspects for geothermal energy at Dholera. Exploration methods such as Seismic, Gravity and MT have been used at Dholera. An integration of the three exploration methods is done to understand the structures and delineate the geothermal reservoir, to understand the density variations, the resistivity’s and bed thickness. Seismic study for shallow depth was done using Microsoft Excel by plotting time-distance graphs inferring the number of layered problem we have and manually calculating the thickness of the bed along with its velocities. Gravity survey indicates the variations of the gravity values i.e. density values over different stations. With the help of the contour plot of gravity data we can postulate the possible geothermal reservoir. 2D MT survey deals with the resistivity of the sub surface. The resistivity distribution at 3km depth shows a low resistivity zone sandwiched between high resistivity zones indicating magmatic reservoir possibility. This result was also supported with the gravity survey result. At D2_12 MT station, 7000 meters below sea level, low resistivity zone has been identified possibility of hot water reservoir which may be due to the heat from the magmatic reservoir.