| Title | Joint Inversion of Temperatures in a Synthetic Geothermal Field Using Mt, Clay Alteration Models, and Geothermal Reservoir Simulation |
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| Authors | D. Dempsey, J. O’Sullivan, S. Pearson |
| Year | 2016 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Joint inversion, magneto-telluric, clay alteration, resistivity, geothermal reservoir simulation. |
| Abstract | Joint inversion seeks to assimilate multiple data streams with the goal of constraining the spatial distribution of some subsurface quantity. In this paper, we demonstrate a joint inversion approach that utilizes magneto-telluric (MT) survey data and a downhole temperature profile to infer the subsurface temperature distribution in a geothermal system. Specifically, we focus on interpreting the low resistivity anomaly associated with a hydrothermally altered clay clap, which, given an understanding of the clay formation temperature range, carries information about the contemporary temperature field. The workflow we develop here involves: (i) simulating natural-state temperatures in a geothermal system, (ii) a model for hydrothermal alteration, (iii) forward simulation and (iv) subsequent inversion of MT surface observations, (v) modelling of collocated resistivity and downhole temperature profiles, which is then (vi) extrapolated to obtain an inferred temperature distribution away from the borehole. The workflow is demonstrated for the synthetic test case of a simple geothermal system. Inferred temperatures resulting from the joint inversion agree well with the true values in the vicinity of the clay cap but worsen rapidly outside the lateral extent of this region. |