New ground-breaking advances are currently being made at the Utah Frontier Observatory for Research in Geothermal Energy – the Utah FORGE – using methods borrowed from the oil and gas industry for unconventional hydrocarbon development. Recently, geothermal history was made when Utah FORGE successfully completed the first of two highly deviated deep wells in the hot, hard granite that will form the geothermal reservoir.
Utah FORGE is an underground research laboratory funded by the U.S. Department of Energy. Managed by the Energy and Geoscience Institute at the University of Utah, the project site is located in south-central Utah near the town of Milford in rural Beaver County. The laboratory’s purpose is to provide a facility where the tools and technologies required for creating, sustaining and managing enhanced geothermal system reservoirs can be tested under reservoir conditions. EGS reservoirs provide the opportunity to utilize geothermal energy anywhere in the world.
Conventional geothermal reservoirs occur in hot, permeable rock. Production wells are commonly drilled to less than about 10,000 feet and deviated at angles of less than about 40 degrees from vertical. At greater depths, permeabilities typically decrease, and wells needed to produce large quantities of hot water are not cost-effective.
Permeability in EGS reservoirs must be artificially created or enhanced by opening existing fractures or creating new ones. Highly deviated wells provide the greatest access to the fractured volume that is created between the wells. The recent drilling at Utah FORGE represents the first time a well-optimized EGS production well was completed specifically for geothermal applications. The well was drilled vertically to 5,938 feet, deviated at a 65-degree angle from vertical and then continued along this trajectory for a total length of 10,987 feet. The well ultimately reached a true vertical depth of 8,561 feet. Preliminary measurements indicate temperatures will exceed 228 degrees Celsius (442 degrees Fahrenheit). The well was drilled and completed in 84 days. This well’s successful completion is a first for the geothermal industry and demonstrates that drilling large diameter, long subhorizontal laterals in granite is achievable.
By 2022, the primary assets of the Utah FORGE laboratory will comprise:
- A pair of highly deviated wells in hot granite – one for injection and one for production from the stimulated fractured reservoir. The second deviated well will be drilled in 2022 and will be parallel to the first well. Following completion of the production-injection pair, the reservoir will be created, and circulation tests initiated.
- A state-of-the-art seismic monitoring network, including surface seismometers and four deep monitoring wells, drilled to depths of 1,000, 3,200, 7,500 and 9,000 feet.
- Two deep wells for testing tools and technologies required to establish and sustain continuous fluid flow and energy transfer from an EGS reservoir.
Emphasis will be placed on improved drilling techniques, drill bit design, isolation tools, stimulating fractures from cased wells, fracture imaging technologies, managing induced seismicity and reservoir characterization.
Over the next several months, Utah FORGE will analyze the geophysical and image logs from the first deviated well and the 9,000-foot seismic monitoring well. These data will be used to develop a plan for stimulating the toe of the deviated well in the latter half of 2021. These tests will determine the stress conditions through short-term injection experiments. The stimulation will be monitored with distributed acoustic seismic cables, geophone strings in the monitoring wells, permanent surface seismometers, and a surface nodal array.
Continuous monitoring of seismic activity by the University of Utah Seismograph Stations has detected no seismicity related to the drilling activities. Seismicity across Utah, including at the Utah FORGE site, can be followed in near real-time at Quake.Utah.edu.
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