Magnetotelluric characterisation of the Habanero geothermal EGS project - initial results on fluid injection monitoring and regional geology

Abstract

Magnetotelluric data has been collected across the Habanero geothermal site in the Cooper Basin, South Australia, in view of delineating the crustal structure underneath the geothermal area and to monitor fluid injection of the Habanero 3 borehole. Two surveys have been carried out. Initially, two perpendicular profiles have been established, each about 20km long, to obtain 2D profiles across the Habanero site. The aim is to estimate the sediment thickness to allow for constrained 3D forward modelling for fluid injection scenarios. Furthermore, the broadband data with periods up to 1000 s allows a view into the crust. Geochemical data from the Mound Springs shows that the seeping water contains a minor component of mantle CO2. MT can be used to image the fluid pathways if such a connection exists. The results will be compared to recent findings from fluid pathways in the Lake From embayment a few hundred km south of the Cooper Basin. Additionally, initial results from the fluid injection monitoring experiment of the Habanero 3 borehole will be shown. In November 2012, fluids were pumped at depth of around 4km for a period of two weeks. The fluids exceed the amount introduced into the Paralana EGS in July 2011, however a pre-existing fluid reservoir from a prior fluid injection exists. We report on surface MT response changes due to the fluid reservoir at depth.