| Abstract |
Quantification of geological knowledge is critical in successful exploration and identification of geothermal reservoirs. Quantitative geology is expressed by 3D geological models, which are essential for an integrated approach in geothermal technology. Most 3D geological models are developed from subsurface data, such as seismic and well data. With this study, we present a 3D geological model developed primarily from surface data, specifically a detailed geological map. The study area is located along the east flank of the Wassuk Range and south end of Walker Lake basin in west-central Nevada. The technique of 3D geological mapping involves digitizing of the geological map and selected cross sections, concatenating these scattered data with a digital elevation model by using a spline algorithm called the minimum tension technique. In the first step, a 3D fault model was developed, revealing the complex fault pattern of a graben structure in 3D space. Stratigraphic horizons were delineated after the fault blocks were defined. The final 3D structural model has been validated using 3D seismic data, which were integrated into part of the geological model. Conversely, the 3D geological model helped to validate interpretations of the 3D seismic data. Temperature, gravity, and well data were also integrated into the geological model to better understand the structural controls of this particular geothermal system. Stress field determination was carried out by analysis of fault slip data. We apply the PTB method for stress field calculation and validate the derived stress field by fluctuation histograms and simulations of calculated versus measured shear stress vector. With emphasis on fault behavior in the current stress field, we calculated shear and normal stress distribution along the mapped faults to discriminate between faults of high dilation and high slip tendency. Faults with high dilation tendency might primarily channel thermal fluids, thus providing favorable targets for geothermal exploitation. Based on this collective understanding, drill site selection and well path planning has been quantitatively defined. Our case study shows how conventional geological maps can be employed to develop 3D structural geological models. We call this method 3D geological mapping, which can be used elsewhere provided geological maps are available. |