Integrated 3D Modeling of Structural Controls and Permeability Distribution in the Patua Geothermal Field, Hazen, NV

Abstract

The Patua Hot Springs (Patua) geothermal prospect operated by Gradient Resource Inc. is situated at the southern end of the Hot Springs Mountains near Hazen, Nevada. The project area is located roughly 40 miles east of Reno, NV and 10 miles east of the town of Fernley. Over the course of exploration and resource development at Patua, multidisciplinary data sets have been acquired and subsequently integrated into a 3D model focused on faulting and permeability distribution in the Patua geothermal field. A base concept in the generation of the 3D model is the extensively documented phenomena of Walker Lane strike slip faulting and Basin and Range extensional tectonics, commonly referred to as the Walker Lane Transition. This incorporation of regional stress and strain as it applies to project scale phenomena has resulted in a better understanding of permeability structure. Data sets used in generation of the 3D model include field mapping of faults and hydrothermal alteration, 2D seismic reflection profiles, borehole seismic surveys, MT, gravity, open hole geophysical logs, borehole imaging logs, lithology logs, brine chemistry, core sample analysis and reservoir pressure data. These sets of geophysical data and published geodetic data were jointly considered with direct measurements of a broad variety for the purpose of constraining the interpretation of structure and to aid in delineating permeable fractured pathways within the Patua reservoir. Interpretation and correlation of roughly 42 miles of 2D seismic reflection data using field mapping, aerial photography, and evident geomorphology indicates the structural controls on geothermal upwelling are sets of NE-striking Riedel Shears propagating from an approximate N70W striking, left stepping segment of the Walker Lane that traverses the project area. This structure is a southern segment of the Pyramid Lake Fault and separates the Hot Springs Mountains from the Virginia Range to the south.