Current and Planned Activities
Utah FORGE Site, Milford, UT
June 30, 2020
next update due September 30, 2020
Utah FORGE has been established to develop, test, and improve the technologies and techniques required to develop EGS-type geothermal resources. The following summarizes the current and planned activities at the Utah FORGE site, and it includes an overview of the drilling program for the year and a description of the various types of scientific and environmental monitoring.
Note that in the following, Covid 19 related travel restrictions prevented GPS and Gravity data measurements in the first quarter of 2020.
View of the Utah FORGE site in early 2020, showing drill pads, power line supply, and the planned site of the field office. Well 58-32 is the deep pilot well that can be used to deploy downhole instruments during 2020-2021 stimulations. Well 68-32 is dedicated to seismic monitoring with a permanently installed geophone and accelerometer at depths of 921-925 ft. Well 78-32 is instrumented with a Silixa DAS cable including a Constellation fiber cemented in the annulus of the 5 ½” casing to 3268 ft. Downhole instruments can be deployed in the casing. 56-32 will be drilled in late 2020 or early 2021. A Silixa DAS cable, including a Constellation fiber, will be cemented in the annulus of the 9 5/8” casing to a depth of 4500 ft before running and cementing the 5 1/2 “ casing
Drilling of the first of two deep deviated wells, 16A(78)-32, will begin in the second half of 2020. This well will serve as the injection well for the injection-production well pair that will form the heart of the laboratory. The well will be drilled vertically to 5,940 ft and then steered to the east-south east (105o) to a measured depth of approximately 10,800 ft and a true vertical depth of 8,480 ft. Temperatures at this depth will be close to 440 oF (226 oC). Full specifications are described in the Provisional Synopsis of Drilling Procedures for Well 16A(78-32).
Scientific and Environmental Monitoring
Scientific monitoring is directed at establishing a background understanding of a range of geoscientific parameters and their secular variation with time in the lead up to drilling and stimulation campaigns. These include seismicity, ground movement, gravity, magnetotellurics (MT), and groundwater compositions and piezometric levels.
Seismicity is monitored using both the regional UUSS and local Utah FORGE seismic networks. Seismometer and earthquake locations, event waveforms, and continuous waveforms are available via the University of Utah Seismograph Stations. Since the installation of the local broadband array in Phase 2A, 283 earthquakes (M -0.99 to 1.89) have been located, 86 during the past quarter. Events beneath the Mineral Mountains to the east and southeast of the Utah FORGE site continue to be detected. No earthquakes have been recorded within the Utah FORGE footprint. An archive of datasets pertaining to the 2019 stimulation in well 58-32 is hosted by the University of Utah Center for High-Performance Computing (CHPC).
Ground movement is being evaluated through two independent methods comprising high precision repeat surveys of GPS monuments and analysis of InSAR interferograms. The GPS monitoring network consists of 20 equispaced monuments covering the Utah FORGE footprint and extending over an area of 15 km2. Surveying activities commenced in 2019 and are carried out on a quarterly basis. The preliminary results from surveys in 2019 suggest several mms of vertical and lateral movement related possibly to seasonal effects, and this is the subject of ongoing analysis. By contrast, the analysis of InSAR interferograms from 2016 onward indicates there has been no detectable ground movement at millimeter scale.
A 4D microgravity survey began in early 2019 in order to benchmark surface and subsurface elevations prior to Phase 3 drilling and stimulation campaigns. Microgravity stations are collocated with GPS deformation benchmarks and use the same location survey data. Surveys are undertaken quarterly basis. The focus of current activities is comparative analysis of GPS survey results and InSAR analysis to check seasonal variance and to evaluate possible changes in the groundwater elevation.
New high-quality tensor MT data at 122 sites, including the vertical magnetic field and utilizing ultra-remote referencing, have been acquired over the project area. These have been merged with MT data from the adjacent EGI SubTER and Play Fairway projects, with the whole survey covering >300 km2. The results will be used to delineate the densities of faults and fractures in crystalline basement rocks, to define the heat sources, and to derive baseline 3D resistivity structure for later MT monitoring of temporal changes in resistivity structure following well stimulation in the EGS reservoir. Currently, the MT data obtained under subcontract to Quantec Geoscience has received final QC, and the finite element modeling is underway.
Groundwater data around the Utah FORGE site has been collected to determine the piezometric levels and compositional variability. Field measurements in 2020 are designed to obtain and survey new groundwater wells that have been drilled on the distal periphery of the Utah FORGE project area. Plans to drill a dedicated groundwater monitoring well on the site is a low priority for 2020.