Joint geophysical-petrological-lithological inversion to determine geothermal potential and subsurface temperature

High-quality maps of the geothermal gradient are essential when assessing the geothermal potential of a region. However, determining geothermal potential is a challenge in regions where direct measurements of in situ temperature and thermal property information are sparse (e.g. Ireland). Significant risk reduction is required to understand the heat resources before they can be fully exploited. Furthermore, individual geophysical methods are sensitive to a range of parameters, not solely temperature.

We determine the geothermal gradient by inverting seismic, in addition to other geophysical, lithological and petrophysical input datasets, directly for temperature. The temperature maps obtained for Ireland so far are within error of direct borehole temperature measurements, providing confidence in the results (Chambers et al. EarthArXiv 2024 and in review). We further develop the joint geophysical-petrological thermochemical workflow used by introducing lithology and transient thermal effects to the inversion. Additionally, gravity data will be integrated into the island scale model to refine the 3D crustal structure, and hence the subsurface temperatures.

We initially focus on new subsurface temperature models of Ireland with uncertainty where the multi-parameter output models fit the input data and reveal the thermal structure within the crust and mantle, including the upper-crustal geothermal gradient. We then will look at the new applications of the methodology at the local scale, in particular at Krafla, Iceland, for a local geothermal powerplant application and the integration of melt to the inversion. The new workflows have potential, to be used as a resource to investigate geothermal regions worldwide.