Resistivity Imaging of Geothermal Resources Using 1D and 3D MT Inversion Case Study Suswa Volcano Kenya


Raymond Mwalugha Mwakirani
Geothermal Development Company


ABSTRACT

In this study, we investigate the geothermal potential over the Suswa geothermal prospect through correlation of 1D and 3D resistivity models. Magnetotellurics (MT) and Transient electromagnetics (TEM) is commonly used to help target geothermal wells and assess resource capacity in potential areas because it can image the low resistivity, low permeability smectite clay that caps most geothermal reservoirs. MT and TEM data obtained from earlier surveys since 1999 to 2013 will be re-processed and interpreted using 1D and 3D inversions. Usually 1D interpretation is easy to obtain and is always representative to shallow depths while 3D is computer intensive and a costly task to perform though with the development MT interpretation codes and advancement in computer hardware, 3D electromagnetic data interpretation can be perfomed. The assumption in 1D inversion is that resistivity varies only with depth while in 3D resistivity varies in all directions hence it can give high resolution images of structures within a geothermal system. Mainly 1D inversion has always been used due to limitation in computer hardware to perform 3D inversion, but due to developments in computational hardware a workflow for 3D inversion will be set and carried out and the results from the inversion interpreted in form of resistivity maps and cross sctions. This will be accomplished using a 3D inversion algorithm. This research is supposed to explain the differences in results and come up with general recommendations for effective MT resistivity imaging of geothermal resources, 1D inversion is expected to have a better resolution at shallower depths and 3D invesrion is expected to give a better resolution at deeper portion where the geological structures varies in all directions. This will provide reliable information about the presence, location, and size of geothermal systems in Suswa prospect.


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