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December 11, 2017

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USGS explores hot rocks for geothermal potential on Oregon Indian Reservation

by KYLIE WILLIAMS on November 30, 2017 APPLIED

Scientists and students from the USGS meet with members of the Confederated Tribes of the Umatilla Indian Reservation during fieldwork in June 2017[Click to enlarge]

Scientists and students from the USGS meet with members of the Confederated Tribes of the Umatilla Indian Reservation during fieldwork in June 2017.

USGS potential fields team members gather at a World Relative Gravity Reference Network (WRGRN) base station.

USGS potential fields team members gather at a World Relative Gravity Reference Network (WRGRN) base station. This base station was used to calibrate measurements collected during the field survey.

USGS summer student, Zachary Palmer from Colorado School of Mines, makes friends with a local between taking gravity measurements and collecting samples on the Umatilla Indian Reservation.

USGS summer student, Zachary Palmer from Colorado School of Mines, makes friends with a local between taking gravity measurements and collecting samples on the Umatilla Indian Reservation.

[Click to enlarge]

Shown above is the Umatilla study area and profile lines.


[Click to enlarge]

Profile 1 and 2: 2D potential field models displaying magnetics and gravity data and geologic interpretations. The two profiles crossed the Hawtmi and Waihatya fault zones and identified multiple faults and dikes that were not mapped on the existing geologic map.

In a remote corner of northern Oregon lies a complex fault zone: a nexus of faults concentrating regional stress in the area. The system is not yet well understood, geologically speaking, and in the last 100 years several earthquakes recorded immediately to the north, in southern Washington state, let locals know that the area is seismically active. While earthquake risk is a concern, it also indicates that the area is prime geothermal country, with the potential for local communities to harness this renewable energy resource for energy independence.

“We find natural geothermal systems tend to occur in these areas of complex fault interaction,” explains Jonathan Glen, Research Geophysicist with the U.S. Geological Survey (USGS) Energy program, “Places where you get active deformation can lead to the generation of permeability, and permeability is a key factor in the development of a geothermal system.”

Permeability, in the form of faults and fractures, provides a “plumbing system” for the hydrothermal waters to move through, says Glen. These waters are the medium used to carry the heat from the rocks deep below to the surface. Without a fracture system for fluids to interact with heat from the rock, there is not a viable geothermal resource.

This area of northern Oregon is home to the Confederated Tribes of the Umatilla Indian Reservation (CTUIR). In recent years, the CTUIR observed how their neighbors to the southwest - The Confederated Tribes of the Warm Springs Reservation – explored the geothermal potential under their reservation. So, the CTUIR partnered with the USGS and industry partner, AltaRock Energy, to apply for funding from the U.S. Bureau of Indian Affairs and Energy Trust of Oregon. The trio were granted the funds to assess the geothermal resources under the Umatilla Indian Reservation.

“The CTUIR are interested in what geothermal resources exist, and how the resources might be used,” says Glen, “For example, what temperatures are accessible at different depth? Are the temperatures high enough for electricity generation, or direct use opportunities?”

Hot, fractured rocks hold enormous potential to supply direct heat or generate electricity for communities, particularly those located off the grid. Geothermal energy is increasingly being used to wean remote communities off diesel generators, and onto cleaner, cheaper, local sources of heat and electricity.

“Heat at lower temperatures from within the earth can be used directly to heat buildings, including greenhouses for growing plants, drying crops, heating water at fish farms, or driving industrial processes, like pasteurizing milk,” explained Glen, “Higher temperature sources can be used at power plants to produce electricity, and the left-over heat can be used directly.”

Glen is part the Geothermal Resource Investigation Project (GRIP) within the USGS Energy program, a multidisciplinary team of about 30 people working together to study geothermal systems, perform geothermal assessments, and develop new field and analytical tools for geothermal research.

In mid-2017, two summer interns joined GRIP to work on the Umatilla geothermal project: Benjamin Grober and Zachary Palmer. Grober, a final year geology undergraduate student at Western Illinois University, and Palmer, graduate student at the Colorado School of Mines, received internships through the National Association of Geoscience Teachers. Grober was jointly supported by an internship through the USGS Student Interns in Support of Native American Relations Program.
“My role in the project was to help out with the gravity survey,” said Grober, “We took gravity measurements at specific locations around the entire Indian Reservation. It’s a remote area, sparsely populated with lot of large ranches and rough terrain. It was very difficult getting to some of the places we needed to but the scenery was beautiful.”

Palmer, Grober’s field partner for the summer, said, “The area is extremely faulted and folded and many of the faults aren’t actually visible at the surface. We were trying to map those folds and faults to determine where would be the best place to find the geothermal fluids.”

The investigation included potential field (gravity and aeromagnetic) surveys, Light Detection and Ranging (LiDAR), magnetotellurics (MT), and paleomagnetics. Palmer and Grober used a gravimeter to record relative gravity at over 1300 locations across the area, collected hand samples for rock property measurements, including density and magnetic susceptibility and drilled oriented paleomagnetic cores for magnetic remanence. The students used the field measurement to constrain 2D potential field models in Oasis montaj, provided as part of Geosoft’s Education Program, and created a 2D potential field model using the GM-SYS Modelling extension.

“Using post-processed gravity and magnetic data, we created 2D models from two profile lines perpendicular to major faults in the region,” said Grober, “The models allowed for accurate depictions of geologic units and structures in the subsurface.”

The two profiles crossed the Hawtmi and Waihatya fault zones and identified multiple faults and dikes that were not mapped on the existing geologic map. The models will be further refined and constrained by the addition of the MT and LiDAR data.

“The students are geologists, not geophysicists, so they learned geophysics on the job,” said Glen, “It’s been a great opportunity for them to get experience with everything from sampling, to processing, to modelling in Geosoft.”

The surveys and fieldwork completed in 2017 are a significant first step toward assessing the geothermal potential lying beneath the Umatilla Indian Reservation. Further exploration and drilling temperature gradient holes will help determine if a suitable reservoir exists, is commercially viable, and accessible to help make the reservation energy-independent.


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