The Utility of Full Tensor Gradiometry in Geothermal Resource Mapping: An example from the Basin and Range Province of Nevada

Summary Faults play a key role in heat transport and permeability within extensional setting convective type geothermal plays. While faults can act as seals or conduits to fluid flow, their identification is paramount to the evaluation and assessment of geothermal resources. Identification of faults relies heavily on surface expression or seismic reflection and/or refraction methods. Gravity data is also utilized to identify basin geometry, which will often indicate location of faults with high displacement if density contrast of a sufficient magnitude is present. Full Tensor Gradiometry measures the directional gradients of the gravity field, allowing the interpreter to quantify subtle changes in density contrast associated with faulting, provided sufficient magnitude and offset are present. Full Tensor (Gravity) Gradiometry (FTG) data acquired over the Crescent Valley geothermal field in Nevada reveals previously unmapped faults and identifies their relationship to the regional structural framework. Intersections of faults are additionally identified through lineament extraction methodologies, which in turn contribute to the identification of favourable geothermal prospects. Additionally, 2D modelling of FTG and seismic reflection data can be used quantitatively to assess permeability of shallow sedimentary units.