Rift Zones as a Case Study for Advancing Geothermal Occurrence Models

Abstract

To search efficiently for blind geothermal systems, general geographic regions must first be identified based upon gross characteristics which together imply favorable heat flow, fluid flow, and permeability. Geothermal occurrence models seek to strategically identify those promising locations to focus exploration efforts and investment. In so doing, such models can increase the expected success rate of exploratory drilling, reduce risk, and attract investment. Among the most promising tectonic settings for blind geothermal systems are rift zones. Rift zones occur where lithospheric plates are thinned by tectonic extension and convection at zones of upwelling hot material. The continued supply of magma to this separation zone increases heat flow and thermal energy at shallower depths than in other tectonic settings. Given the inherent qualities of rift zones, the frequency of geothermal anomalies should be relatively high, making them attractive targets when searching for blind hydrothermal resources. Geothermal occurrence models specify characteristics (e.g., rock type, stress field, fault geometry, hydrology, local volcanism, etc.) that indicate where to find a blind resource within a rift zone. In this paper, we review literature contributions to the development of geothermal occurrence models and explore rift zones as a case study for their application. We identify the key data and analytical tools that are necessary to advance these models to effectively and efficiently inform regional-scale resource assessment.