Fracture delineation and monitoring of geothermal and coal seam gas areas using magnetotellurics

Abstract

New ways of energy production through the use of coal seam gas plays and geothermal hot dry rock and hot sedimentary aquifer systems pose challenges in identifying and monitoring fluid in the subsurface. We propose the use of the magnetotelluric (MT) method to image static and dynamic fluid distributions in the subsurface exhausting the contrast in electrical conductivity between resistive host rock and conductive fluid-filled, porous rock. Base line MT measurements provide reference transfer functions and inverse models to characterise the electrical conductivity distribute on which is linked with bore hole and other geophysical data to obtain knowledge about fluid distribution at depth. The reference models are used to accurately forward model fluid injection or extraction temporally and spatially. This work shows results from fluid injections at a hot dry rock system at Paralana, South Australia, and its applicability to other geothermal and coal seam gas systems.