Recent peer-reviewed publications from the GBCGE team

July 30, 2021

The GBCGE team contributed to several peer-reviewed publications in 2021 related to our current research projects.

  1. The first paper to be released presents research led by Kurt Kraal, a PhD student in the Center, and evaluates the relationship between hydrothermal alteration, fractures and permeability at the Fallon FORGE EGS site in Churchill County. His paper can be downloaded for free here. Key findings from this work include:
    • A 2481 m-deep EGS observation well (21−31) was drilled at the Fallon FORGE site in early 2018 to further verify the geology and rock properties of the proposed EGS reservoir formations.
    • Borehole data from well 21−31 were evaluated and integrated, including drill cuttings and sidewall cores (petrographic, XRD, hyperspectral), wireline geophysical logs (e.g., gamma, neutron porosity, resistivity, sonic scanner), borehole imagers (FMI, BHTV), and pressure and temperature logs.
    • Our findings indicate that hydrothermal alteration and veining is found throughout the entire pre-Miocene interval of well 21−31, and includes epidote mineral assemblages that suggest past temperatures >250 °C.
    • Overall lithologic variability is high, with volcanic, intrusive, metamorphic, and sedimentary rocks present in the lower 700 m of the well. Natural fractures are abundant throughout the pre-Miocene section, but are more frequent in the felsic intrusive and felsic volcanic lithologies and appear optimally oriented for reactivation via hydraulic stimulation.
    • Injection test results indicated an injectivity index of 0.025 L/min/kPa, which is an order of magnitude lower than a typical threshold for commercial wells. Analytical modeling of injection test results indicate that the majority of the well is low permeability (< 10−16 m²), with some discrete, localized zones of higher permeability (∼ 10 -12 m², less than 0.5 percent of the pre-Miocene (deep) section intersected by the well).

Kraal, K.O., Ayling, B.F., Blake, K., Hackett, L., Perdana, T.S.P., (2021). Linkages between hydrothermal alteration, natural fractures, and permeability: Integration of borehole data for reservoir characterization at the Fallon FORGE EGS site, Nevada, USA. Geothermics, Vol. 89. https://doi.org/10.1016/j.geothermics.2020.101946

Visit the Fallon FORGE and Hyperspectral characterization project pages for more information.

  1. The next paper to come out this year was led by post-doctoral scholar Cary Lindsey and presents the results of a geothermal play fairway analysis that we completed in northwest Argentina. This work was completed in collaboration with partners from the Servicio Geologico Minero Argentina (SegemAR) – Argentina’s national geological survey as part of our International Geothermal Capacity-Building project. The paper can be downloaded for free here. Key findings from this work include:
    • Evidence layers were grouped to model the spatial distribution of three primary geological attributes of a geothermal system: heat, permeability, and fluid. Datasets used to create these evidence layers included hot springs, fluid geothermometry, age and distribution of volcanism, hydrothermal alteration, regional fault information along with their kinematics and approximate age of most recent rupture, type and location of structural settings, and earthquakes.
    • Spatial statistical methods were used to model and weight the distribution of these evidence layers, including distance buffers, point statistics, and weighted sum functions.
    • Resulting favorability models were created using the veto (product) and voter (sum) methods, and both models indicate highest geothermal potential in Cerro Tuzgle/Aguas Calientes/Tocomar and west Coranzulí.

Lindsey, C., Ayling, B. F., Asato, G., Seggiaro, R., Carrizo, N., Larcher, N., Marquetti, C., Naon, V., Conde-Serra, A., Faulds, J. E., Coolbaugh, M. F., (2021). Play fairway analysis for geothermal exploration in north-western Argentina. Geothermics, Vol. 95. https://doi.org/10.1016/j.geothermics.2021.102128

Visit the International Geothermal Capacity Building home page for more information about this project.

  1. GBCGE researchers Jim Faulds and Bridget Ayling collaborated on a review paper for Nature Reviews – Earth and Environment that discusses the geological controls on successful utilization of geothermal resources for power generation. The paper can be accessed here (journal subscription required).

Jolie, E., Scott, S., Faulds, J. E., Chambefort, I., Axelsson, G., Gutiérrez-Negrín, L., Regenspurg, S., Ziegler, M., Ayling, B. F., Teklemariam, M., Richter, A., (2021). Geological controls on successful utilization of geothermal resources for power generation. Nature Reviews Earth & Environment. https://doi.org/10.1038/s43017-021-00154-y

  1. The most recent peer reviewed publication involves work led by Jason Craig, former MSc student in the Center. The paper presents the results of a regional to local-scale application of geothermal play fairway analysis in Nevada, which culminated in drilling and the discovery of a new blind geothermal system at Gabbs Valley in Nevada. The paper can be viewed here.

Key findings from this work include:

    • Multiple datasets suggest the presence of a blind geothermal system, including collocated intersecting gravity gradients, a magnetic-low, low-resistivity, a 2-m temperature anomaly, and geothermometry temperature estimates of 130–140 °C obtained from water samples collected from nearby agricultural wells.
    • Six 150 m-deep temperature-gradient holes were drilled to target the geophysical and thermal anomalies. The maximum bottom-hole temperature measured was 124.9 °C.
    • Power capacity estimates based on resource conceptual models of the geothermal system suggest a median (P50) capacity of ∼16 MWe (megaWatts electric).

Craig, J. W., Faulds, J.E., Hinz, N.H., Earney, T.E., Schermerhorn, W.D., Siler, D.L., Glen, J.M., Peacock, J., Coolbaugh, M.F., DeOreo, S.B., (2021), Discovery and analysis of a blind geothermal system in southeastern Gabbs Valley, western Nevada, USA. Geothermics, Vol. 97.  https://doi.org/10.1016/j.geothermics.2021.102177 

Visit the Nevada Play Fairway project: Phase 3 project page for more information about this project.

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