Incorporating Geological Constraints into Geophysical Inversion Models: A Case Study from Ohaaki Geothermal Field

Abstract

Geophysics plays a vital role in geothermal exploration, mapping and monitoring. Potential field data, gravity and magnetics, are used to reveal deep geological structure and provide rock property information that help to locate and characterize geothermal systems. However, the inherent ambiguity of potential field data adds uncertainty that makes modelling and interpretation more challenging. In this paper we present a workflow that reduces modelling uncertainty by incorporating prior geological information that constrains the inversion toward a geologically interpretable result. A case study from the Ohaaki Geothermal Field is presented that demonstrates how the non-uniqueness of gravity modelling is reduced by use of a geologic reference model incorporated into the inversion objective function. The workflow is applicable to geophysical data from any geothermal field that has a drilling derived geological model.