Integrated 3D Geophysical Inversion and Geological Modelling for Improved Geothermal Exploration and Drillhole Targeting

Abstract

Choosing where to drill a geothermal well is perhaps the most important decision made in a geothermal exploration program. In this paper, we describe an improved exploration methodology that makes more effective use of existing exploration datasets, integrates all data in three dimensions, constrains data against one another, and employs a quantitative and comprehensive approach to selecting drill targets. The methodology has been adapted from the mining industry where it has found great success. An important component of the proposed approach involves 3D inversion of multiple geophysical datasets, in both unconstrained and constrained forms, as a way of delineating rock domains in the subsurface. The method culminates in the construction of a 3D Common Earth Model which is consistent with all datasets. Such a model provides the platform for further analysis, interpretation, hypothesis-testing, and ultimately, informed selection of drill targets. A quantitative drill targeting approach that utilizes specific exploration criteria is also presented. We argue that implementation of this approach in the geothermal sector will improve exploration programs and result in increased drilling success.