Monday, 3 November, 2025/Edition 83

A recent issue of AAPG Bulletin focuses on geothermal power. Globally, the United States, Indonesia, the Philippines, Turkey, New Zealand, and Kenya are major producers of geothermal energy. Nevertheless, in the United States, geothermal power accounts for merely 0.4 percent of electric generation, so there is huge potential for expansion. This week, we’ll take a look at some new studies of geothermal power in the Great Basin and Texas.

Rasoul Sorkhabi

Editor, Core Elements

Geothermal Power in Nevada and Utah

James St. John/Wikimedia Commons

An article by researchers at the University of Nevada, Reno offers a resource model for the Northern Granite Springs Valley (NGSV) in northwestern Nevada.

Study area: NGSV, also called the Adobe Flat, contains thermal anomalies and extensional faults and has been described as a blind geothermal prospect since the late 1970s.

What researchers did: The researchers used geological, geophysical, thermal, and fluid chemical data to construct play fairway maps.

What they found:

• The study indicates a power-capable geothermal resource in NGSV estimated between 3.7 and 35.6 megawatt electrical (MWe), with a P50 estimate of 11.5 MWe.

• These correspond to a power density of three to eight MWe per square kilometer with a P50 estimate of 4.9 MWe per square kilometer.

• These estimates are for a reservoir area of 2.4 square kilometers, temperatures of 140–160 degrees C at 1.2-kilometers of depth.

In another study in Utah, Ted Morgan and colleagues report on Mesozoic siliciclastic strata for sedimentary geothermal exploration.

What they did: The researchers measured porosity and permeability of 164 rock samples and examined their petrography in thin sections.    

What they found: Researchers identified three siliciclastic units of Early Jurassic age as prospective sedimentary reservoirs:

1. The Springdale Member of the Kayenta Formation (40 meters thick) with a median porosity of 15.7 percent and a permeability of 18.8 millidarcy
2. The Moenave Formation (90 meters) with a median porosity of 15.1 percent and a permeability of 10.2 millidarcy
3. The Shurtz Tongue of the Navajo Sandstone (90 meters) with a median porosity of 11.4 percent and a permeability of 6.4 millidarcy

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Geothermal Favorability for Hydrothermal Power in the Great Basin

USGS is updating some of its previous assessments around geothermal potential. Source: Christopher C. Skinner/Energy Resources Program.

An article in Geothermics offers favorability maps for hydrothermal power resource in the Great Basin, in the southwestern United States.

Background: This work is part of the USGS’ effort to update their 2008 assessment of conventional hydrothermal resources for the western United States.

What they did: The study utilized 16 datasets as evidence layers, including:

• Conductive heat flow, magnetic field, isostatic gravity, and basement depth

• Distance to the nearest Quaternary fault and magmatic activity

• Shear and dilation strain rates, strain-rate tensor, and seismic density

• Electrical rock conductance at various depth intervals from the surface to 200 kilometers at the mantle  

Favorability model:

• The researchers then used the XGBoost machine learning algorithm by adding stepwise adding estimators (decision tree branches) with the goal of refining predictions with each new estimator.

• They used Monte Carlo cross-validation based on 1,200 realizations to provide a robust median value favorability map.

What they found: The study offers a new and improved map for conventional hydrothermal favorability for the Great Basin.

• According to the new model, 15 of 28 power-producing systems are in the top one percent of predictions.

• The new favorability map also puts 26 out of 28 power-producing systems above the 80th percentile.

• The new model does not perform well for very small or very low-temperature power-producing systems.

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 Geothermal Power in Texas 

Zack Frank/Shutterstock.com

Researchers from The University of Texas at Austin have published an integrated geothermal resource assessment and techno-economic analysis of the Presidio County in southwest Texas.

Study area: Presidio County is located west of Big Bend National Park and contains multiple fault-bounded basins—a characteristic of the Basin-and-Range province.

The researchers divided the area into three regions based on regional geology and thermal gradients:

1. The border region, a five-kilometer-wide strip along the United States/Mexico border and close to the Rio Grande Rift with a shallow Precambrian basement

2. The Interior Region, the largest in areal size, with a geothermal gradient of 29 °C per kilometer

3. Big Bend in the southeast corner of Presidio County, which remains relatively unexplored

What they did: The researchers used bottomhole temperature data from 101 wells, core samples, well logs and mud logs, and bouguer gravity and magnetic data.

What they found: Researchers created Monte Carlo simulations for heat in-place resource and electricity output for the three regions for these stratigraphic sections:

• Precambrian basement (made up of quartzite, granite and rhyolite)

• Paleozoic-Mesozoic sediments (carbonates with a mean thickness of 1,500 meters)

• Cenozoic rocks (mainly basalt about 1,400 meters thick)

The Precambrian basement, buried at depths of 2,400–6,000 meters below the surface, has the highest heat producibility; however, the basement rocks have little or no porosity and may require hydraulic fracturing.

Baker Hughes’ Study of Geothermal Power in Texas Gulf Coast

K. McCarthy of Baker Hughes presented a geothermal play fairway analysis of the Texas Gulf Coast at the recent Society of Petroleum Engineers’ 2025 convention in Houston.

What they did:

• Researchers used data from hundreds of thousands of boreholes in Texas and the Gulf Coast.

• They then created common-risk segment maps for source rock presence, charge access, reservoir presence, reservoir quality, and seal capacity.

What they found:

• The data with low risk and high prospectivity lie at depths of 8 kilometers or greater, indicating temperatures in excess of 300 °C.

• Economic electricity generation is possible within depths of 4 kilometers and temperatures greater than 120 °C.

• Near-surface geothermal resources, at depths of 3 kilometers or less, are generally less than 150°C in Texas.

Why it matters: Texas is home to hundreds of thousands of oil and gas wells. Geothermal power can be co-produced in oil and gas fields and added to the state’s energy portfolio.

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