Magnetotelluric And Transient Electromagnetic Imaging For Geothermal Resources In Arus-Bogoria Area In Kenya

ABSTRACT

Details of the Earth’s subsurface are largely obscured because it’s difficult to make direct observation of the Earth’s subsurface. Geophysical exploration methods, however, provide a means of remotely examining the Earth’s subsurface. This study therefore seeks to image for geothermal prospects in Arus-Bogoria area using Magnetotelluric (MT) and Transient Electromagnetic (TEM) methods. MT method has the greatest exploration depth whereas TEM has the best resolution at shallow depths. MT and TEM measurements were conducted in Arus-Bogoria geothermal prospect area and the resulting data analyzed and interpreted. The MT data were corrected for static shift using TEM data from stations in their proximity and an integrated data set obtained. WinGlink interpretation software was used to perform 1D inversion on the TEM and MT data and the results obtained used to plot iso-resistivity maps and crosssections for Occam inversion at different elevations to describe the resistivity distribution. Two-dimensional resistivity models were generated using five profiles cutting across the study area. The results from the resistivity analysis indicate that the hotter reservoir conditions are to the Northwest (NW) around Molo Sirwe area. This area is potentially a good high-temperature area. This may well be the upflow of the geothermal system. Resistivity distribution confirms a possible geothermal system up flowing to the NW and is structurally controlled. TEM imaging shallower depth indicates a small irregular relatively resistive anomalous body that may be gas reservoirs; this may explain the numerous gas emitting holes in Mukuyuni area. The potential area determined using resistivity anomaly is about 36 km2 to the west of the study area. More infill data however need to be collected. Feasibility studies to be conducted to determine whether the naturally existing hot springs and gas reservoirs are commercially viable.