New maps of conductive heat flow in the Great Basin, USA: Separating conductive and convective influences

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Geothermal well data from Southern Methodist University and the U.S. Geological Survey (USGS) were used to create maps of estimated background conductive heat flow across the Great Basin region of the western United States. These heat flow maps were generated as part of the USGS hydrothermal and Enhanced Geothermal Systems resource assessment process, and the creation process seeks to remove the influence of hydrothermal convection from the predictions of the background conductive heat flow. The heat flow maps were constructed using a custom-developed iterative process using weighted regression, in which convectively influenced outliers were de-emphasized by assigning lower weights to measurements with heat flow values further from the estimated local trend (e.g., local convective influence). The local linear weighted regression algorithm is two-dimensional locally estimated scatterplot smoothing where smoothness was controlled by varying the number of nearby wells used for each local interpolation. Three maps resulting from conductive heat flow models are detailed in this paper, highlighting the influence of measurement confidence. The three maps use either: measurements from all wells with equal weight (no confidence weights), or one of two different published categorization methods to de-emphasize low-quality measurements; one categorization method graded thermal gradient quality, the other categorization method graded thermal conductivity quality. Each map is an estimate of background conductive heat flow as a function of reported data quality, and a point coverage is also provided for all wells in the compiled dataset. The point coverage includes an important new attribute for geothermal wells: the residual, which can be interpreted as the departure of a well from the estimated background heat flow conditions, and the value of the residual may be useful in identifying the influence of fluids (hydrothermal or groundwater) on conductive heat flow. Of the three maps presented, the map that de-emphasized the impact of wells with low-quality thermal gradient measurements appears to perform best because it did not incorporate many of the wells in the Snake River Plain that do not penetrate the aquifer and are therefore very unlikely to reflect true conductive conditions.

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Publication type Conference Paper
Publication Subtype Conference Paper
Title New maps of conductive heat flow in the Great Basin, USA: Separating conductive and convective influences
Year Published 2023
Language English
Publisher Stanford Geothermal Workshop
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 13 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Proceedings, 48th Workshop on Geothermal Reservoir Engineering
Conference Title 48th Workshop on Geothermal Reservoir Engineering
Conference Location Stanford, California
Conference Date February 6-8, 2023
Country United States
Other Geospatial Great Basin
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