Understanding a Stratigraphic Hydrothermal Resource – Geophysical Imaging at Steptoe Valley, Nevada

Project lead: Sandia National Laboratories (Paul Schwering)

GBCGE project personnel: Dr. James Faulds (PI); Dr. Bridget Ayling; Elijah Mlawsky

Project collaborators: Utah Geological Survey; Geologica Geothermal Group, Inc.; Fervo Energy; Pacific Northwest National Laboratory; United States Geological Survey

Project duration: 18 months: October 1, 2020 – March 30, 2023

Funding agency: U.S. Department of Energy Geothermal Technologies Office

Project goal: Understand the permeability and thermal characteristics of a sedimentary-hosted (i.e., stratigraphic) system in Steptoe Valley, Nevada, with the goal of informing an optimized strategy for subsequent exploration and development for this resource and analogous resources. Sedimentary-hosted geothermal resources may be present in multiple basins in the eastern Great Basin region due to elevated regional heat flow and prevalent thick sections of Paleozoic carbonates, Jurassic sandstones and limestones, and permeable basin-fill sediments. In Steptoe Valley the Paleozoic carbonates that may constitute the reservoir are deformed by several episodes of Paleozoic to Quaternary tectonism. Deformation generates both compartmentalization and conduits (e.g., open connected fractures) that affect heat flow and the geometry of the resource, controlling how the resource may be developed.

Project activities include characterizing the structure and stratigraphy of Steptoe Valley to constrain the stratigraphic reservoir in the context of resource development via collecting new geophysical data and reviewing information from pervious geothermal and oil and gas exploration in the basin. Additionally, conceptual and thermal modeling is being conducted to evaluate the geothermal resource potential: this includes collecting water samples for chemical analysis. In September 2021, Bridget Ayling and Nick Hinz spent a few days collecting water samples at Steptoe, visiting cold springs that discharge along the edges of the basin. The goal is to evaluate fluid mixing relationships in the valley, evaluate the characteristics of a possible thermal fluid, and explore geothermometry indications.

Map of Steptoe Valley showing location of water samples and temperature measurements
Distribution of wells with water geothermometry and measured temperature data (maximum measured temperature of each well is shown), the structural target areas and late Cenozoic faults on a gravity model (CBA) base draped over a hillshade. Well temperatures are from a broad range of well depths (e.g., TG holes of <150 m deep to petroleum exploration wells > 2 km deep) and cannot be compared relative to each other without the depth data. Wells are shown here to show XY spatial extent of these data coverage. Figure from Hinz et al., 2020.
Photo showing water sampling equipment beside a cold spring in a valley
Sampling water for chemical analysis from one of the cold springs in Steptoe Valley, September 2021. The yellow box is a portable sampler that uses a peristalic pump to collect a water sample.
Photo of Paul Schwering and Nick Hinz standing beside one of the abandoned oil and gas exploration wells in central Steptoe Valley, eastern NV.
Paul Schwering and Nick Hinz stand beside one of the abandoned oil and gas exploration wells in central Steptoe Valley.
Photo of Nick Hinz and Dr. Carmen Winn collecting a water sample for chemical analysis from one of the cold springs along the range-front at Steptoe Valley, September 2021.
Nick Hinz and Dr. Carmen Winn assist in collecting a water sample for chemical analysis from one of the cold springs along the range-front at Steptoe Valley, September 2021.

Publications to date:

  • Hinz, N.H., Faulds, J.E., Coolbaugh, M.F., Hardwick, C., Gwynn, M., Siler, D.L., Queen, J., Ayling, B.F., (2020), Play Fairway Analysis of Steptoe Valley, Nevada: Integrating Geology, Geochemistry, Geophysics, and Heat Flow Modeling in the Search for Blind Resources. Transactions, Geothermal Resources Council annual meeting, October 19-23, 2020. https://www.geothermal-library.org/index.php?mode=pubs&action=view&record=1034240

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