Water circulation rates in a geothermal field: a study of tritium in the Beppu hydrothermal system, Japan

AbstractIn this paper, we present an analysis using unsupervised machine learning (ML) to identify the key geologic factors that contribute to the geothermal production in Brady geothermal field. Brady is a hydrothermal system in northwestern Nevada that supports both electricity production and direct use of hydrothermal fluids. Transmissive fluid-flow pathways are relatively rare in the subsurface, but are critical components of hydrothermal systems like Brady and many other types of fluid-flow systems in fractured rock. Here, we analyze geologic data with ML methods to unravel the local geologic controls on these pathways. The ML method, non-negative matrix factorization with k-means clustering (NMFk), is applied to a library of 14 3D geologic characteristics hypothesized to control hydrothermal circulation in the Brady geothermal field. Our results indicate that macro-scale faults and a local step-over in the fault system preferentially occur along production wells when compared to injection wells and non-productive wells. We infer that these are the key geologic characteristics that control the through-going hydrothermal transmission pathways at Brady. Our results demonstrate: (1) the specific geologic controls on the Brady hydrothermal system and (2) the efficacy of pairing ML techniques with 3D geologic characterization to enhance the understanding of subsurface processes.

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A well-preserved,ca250 m.y. old, geothermal field in central Spain: shallowest traces of a much larger hydrothermal system

Applied Earth Science ◽

10.1179/aes.2002.111.2.119 ◽

2002 ◽

Vol 111 (2) ◽

pp. 119-122

Author(s):

J. Lillo ◽

R. Oyarzun

Keyword(s):

Hydrothermal System ◽

Geothermal Field ◽

Central Spain

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Constraining temperature at depth of the Kakkonda geothermal field, Japan, using Bayesian rock-physics modelling of resistivity: Implications to the deep hydrothermal system

Geothermics ◽

10.1016/j.geothermics.2021.102316 ◽

2022 ◽

Vol 100 ◽

pp. 102316

Author(s):

Kazuya Ishitsuka ◽

Yusuke Yamaya ◽

Norihiro Watanabe ◽

Yosuke Kobayashi ◽

Toru Mogi ◽

...

Keyword(s):

Hydrothermal System ◽

Rock Physics ◽

Geothermal Field

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Integrating Stable Isotopes with Mean Residence Time Estimation to Characterize Groundwater Circulation in a Metamorphic Geothermal Field in Yilan, Taiwan

Water ◽

10.3390/w14010097 ◽

2022 ◽

Vol 14 (1) ◽

pp. 97

Author(s):

Ching-Huei Kuo ◽

Pi-Yi Li ◽

Jun-Yi Lin ◽

Yi-Lin Chen

Keyword(s):

Stable Isotopes ◽

Residence Time ◽

Mean Residence Time ◽

Circulation Model ◽

Time Estimation ◽

Geothermal Field ◽

Water Circulation ◽

Temporal And Spatial Distribution ◽

Rock Interaction ◽

Δ18o And Δd

This paper presents a water circulation model by combing oxygen and hydrogen stable isotopes and mean residence time (MRT) estimation in a high-temperature metamorphic geothermal field, Tuchen, in Yilan, Taiwan. A total of 18 months of oxygen and hydrogen stable isotopes of surface water and thermal water show the same variation pattern, heavier values in summer and lighter values in the rest of the year. A shift of δ18O with a relative constant δD indicates the slow fluid–rock interaction process in the study area. Two adjacent watersheds, the Tianguer River and Duowang River, exhibit different isotopic values and imply different recharge altitudes. The seasonal variation enabled us to use stable isotope to estimate mean residence time of groundwater in the study area. Two wells, 160 m and 2200 m deep, were used to estimate mean residence time of the groundwater. Deep circulation recharges from higher elevations, with lighter isotopic values, 5.9‰ and 64‰ of δ18O and δD, and a longer mean residence time, 1148 days, while the shallow circulation comes from another source with heavier values, 5.7‰ and 54.4‰ of δ18O and δD, and a shorter mean residence time, 150 days. A two-circulation model was established based on temporal and spatial distribution characteristics of stable isotopes and the assistance of MRT. This study demonstrates the usefulness of the combined usage for further understanding water circulation of other various temperatures of metamorphic geothermalfields.

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