| Abstract |
VOI quantifies how relevant any particular information source is, given a decision with a highly uncertain outcome; VOI can be used to justify the purchase of collecting additional data when exploring for geothermal resources. Previously, a value of information (VOI) methodology using synthetic data for the exploration geothermal problem was presented (Trainor-Guitton et al., 2013a; 2013b). The synthetic data was used to estimate a reliability measure of the proposed, additional information (which is geophysical data in our example) and should account for possible errors from non-unique geophysical inversions and model interpretations. Evaluating the reliability of geophysical method to decipher key spatial subsurface features is relatively straightforward with synthetic data since many different “true” subsurface models can be tested. Now we present VOI evaluation that utilizes “calibrated” field data to estimate the reliability of magnetotellurics (MT). The field data is considered calibrated as production parameters have been observed that are approximately collocated with the geophysical data. Specifically, we consider 1D electrical resistivity models that have been constructed from MT data, which are within 100m from steamflow, effective permeability and well pressure data. Typically, MT data are used to detect the electrically conductive clay cap which can be indicative of geothermal alteration occurring just above the resource. Therefore, the interpretation of 1D resistivity models into 3D surfaces will be critical in evaluating the effectiveness of the MT technique to detect electrically conductive targets that can be indicative of potential geothermal resources, representative of the well data (steamflow, permeability and pressure). We will present several alternative interpretations that will highlight the challenges and advantages of using field data to estimate the value of geophysical information. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC. |