The Utah Frontier Observatory for Research in Geothermal Energy, funded by the U.S. Department of Energy, is taking a “crucial next step … for making enhanced geothermal systems technologies commercially viable” according to Joseph Moore, principal investigator of Utah FORGE.
Representatives of FORGE announced recently that they have begun drilling their second highly deviated deep well. The new well will mirror an existing injection well about 300 feet away drilled between October 2020 and February 2021.
Milford is the nearest town, with a population of about 1,500. Located in southwestern Utah, it is about three and a half hours from Las Vegas, Nev. The site is located on the western flank of the Mineral Mountains in the north Milford Valley.
The new well will serve as the production well of the two-well doublet during the creation and growth of the reservoir, Moore said.
According to the Department of Energy, a naturally occurring geothermal system, known as a hydrothermal system, requires three key elements to generate electricity: heat, fluid and permeability (when water can move freely through the underground rock).
In many areas, however, the underground rock is hot but there is not enough natural permeability or fluids present. In those cases, an enhanced geothermal system can be used to create a human-made reservoir to tap that heat for energy.
In an EGS, fluid is pumped deep underground and becomes heated by the deep rock. Then it is pumped back to the surface and used to generate electricity.
“The drilling program includes the testing of new tools and techniques, including the application of fiber-optic cables at high temperatures,” said Moore.
Later this year, they plan to stimulate the injection and production wells to create the fractures that will connect them and begin interwell circulation tests.
“The newly created EGS reservoir must be able to provide heat to the circulating water without significant temperature declines. We expect the fracture networks controlling permeability to be dynamic – some fractures will close and others will open but overall, the fracture network must remain permeable over the lifespan of the project,” Moore explained.
Technological Advancement
One of the goals of the Utah FORGE project is to develop technologies for long-term heat extraction and reservoir permeability.
The Department of Energy has set a goal of 90,000 megawatts by 2050 at a cost of $45 per megawatt-hour.
“In order to achieve these milestones, we need to de-risk the tools and technologies needed for widespread adoption of enhanced geothermal systems,” said Moore. “As a research laboratory, our role is to facilitate the testing and refining of those tools and technologies. Utah FORGE is currently the only lab in the world where companies can test their tools and improve technologies.”
The Utah FORGE is not required to produce electricity, but Moore said they might generate power for their operations if suitable equipment can be obtained.
While the tools and technologies used in EGS were developed in the oil and gas industry, many of them have to be redesigned or adapted to this new environment.
“We have discovered that many of the tools developed for the oil and gas industry cannot withstand the high temperatures encountered in our deep wells. Temperatures at the toe of the injection well reach 227 degrees Celsius. New tools, such as packers, plugs and seismic monitoring equipment must be designed and ‘de-risked’ before they can be used for commercial EGS applications,” explained Moore.
In April of last year, they we stimulated existing fractures in three zones in the injection well by pumping water under pressure into them. The technology, Moore explained, is similar to creating permeability in unconventional oil and gas reservoirs. However, unlike water recovered from unconventional hydrocarbon reservoirs, which must be transported to permitted injection sites, water produced by geothermal wells is re-injected back into the reservoir rocks and used over and over again.
Social License to Operate
While the goal is “green energy,” the path to that goal often holds environmental challenges. Moore said these questions were examined carefully and transparently before the project began.
“Prior to initiating Utah FORGE drilling activities, extensive geological, biological and archeological surveys were conducted. The results of these surveys were reviewed by the appropriate regulatory agencies. These agencies concluded there would be no adverse environmental impacts due to Utah FORGE site activities.
“The local communities have embraced the concept of EGS and have been supportive of Utah FORGE activities. All questions raised by the community have been addressed with complete honesty. These discussions began long before any work was done.” he said.
Next Steps
Like the injection well, the upper part of the well will be drilled vertically through approximately 4,550 feet of sediments at which point it will penetrate hard crystalline granite. At about 5,600 feet, the well will be gradually steered at a five-degree angle for each 100 feet until it reaches an inclination of 65 degrees from its vertical point. The total length of the well will be approximately 10,700 feet with the “toe” – or the end of the well – reaching a vertical depth of 8,265 feet. The temperature at this depth will be 440 degrees Fahrenheit.
“In the future, water will be pumped into the injection well, travel through the reservoir of tiny fractures that we previously opened, absorb the heat from the hard, hot crystalline granite, and then be pumped up through this new production well to the surface. This will help us capture the enormous energy potential beneath our feet and bring low-cost, environmentally green and renewable energy across the United States,” Moore said.
Once the well is completed, a series of tests will be run to continue facilitating the development of the EGS reservoir and its long-term connectivity. Additional tests will also include determining the stress conditions through short-term injection experiments, during which microseismicity will be carefully monitored.
“We monitor microseismicity for several reasons. Learnings from previous EGS tests, have shown that reservoir creation involves drilling the first well, determining where the reservoir will form and then drilling the production well. The locations of microseismic events determined from test stimulations in the first well gives us the best indication of where the reservoir will form and where to drill the production well. Once the two wells are drilled, microseismic events provide the most accurate means of monitoring the evolution and growth of the reservoir,” Moore explained.
Moore said the Utah FORGE site is currently the only field-scale research laboratory of its kind in the world where tools and technologies required for commercial utilization of EGS can be tested.
“Several companies are already developing commercial EGS projects and have obtained power purchase agreements for the sale of the produced electricity. We expect growth of commercial EGS projects to move forward quickly within the next seven to 10 years,” Moore added.