Geology
Frontier Observatory for Research in Geothermal Energy
Utah FORGE Geology
The Utah FORGE EGS reservoir occupies a volume of 4.6 km3 (1.1 mi3) that is entirely hosted by hot (>175°C) crystalline granitoid, ranging from granite to diorite in composition. From an engineering and physical perspective, these rocks form a relatively homogeneous unit made of intergrown coarsely crystalline quartz and alumino-silicate minerals that have very low chemical reactivity and low solubility. The reservoir rock is endowed with a complex and relatively dense network of fractures having a wide range of orientations. The reservoir is very tight, with very low porosity and permeability, and there is no evidence of modern hydrothermal fluid. The only producible water is restricted to aquifers hosted in shallow basin-fill alluvium that overlie the EGS reservoir, and this water represents outflow from the Roosevelt Hot Springs system that lies >3 km (1.9 miles) to the east. That this water is abundant, non-potable, and of geothermal origin, fulfils a water resource requirement for future injection-production testing at the Utah FORGE site.
Links to geology data and information can be found below:
General Geology
- Utah FORGE Area Geology Map: This archive contains a geology map of the general Roosevelt Hot Springs region, both in PDF and ArcGIS geodatabase formats, that was created as part of the Utah FORGE project. There is also a report on the geology of the central Mineral Mountains adjoining the Utah FORGE site.
- UGS Interactive Geoscience Map: This is a link to the Utah Geological Survey's Utah FORGE Interactive Geoscience Map. The map layers include information on geology, geography, subsurface temperatures, seismicity, gravity and groundwater. Instructions for using the interactive map and a legend for the interactive map can be found on the map.
- Leapfrog 3D Geologic Movie: This is a 3D geological movie of the Utah FORGE area created with Leapfrog Geothermal 3D modelling software. The movie shows the Utah FORGE site, wells, seismic and lithologic cross-sections, and rock unit tops. This illustrates the thick crystalline granitoid EGS reservoir.
- Geology Map and GIS Data as of 2020 This archive contains a geology map of the general Roosevelt Hot Springs region, both in PDF and ArcGIS geodatabase formats, that was created as part of the Utah FORGE project.
- Geology Maps of Utah This is a link to Utah geology maps in both pdf and GIS formats. This includes the geology of the Utah FORGE area. This site is maintained by the Utah Geological Survey.
- Area Rock Properties This is an Excel spreadsheet that contains rock properties from several wells in the Utah FORGE study area. This includes a map of the wells.
- X-Ray Diffraction Data: This dataset contains X-ray diffraction (XRD) data taken from wells and outcrops as part of the DOE GTO supported Utah FORGE project located near Roosevelt Hot Springs. It contains an Excel spreadsheet with the XRD data, a text file with sample site names, types, and locations in UTM, Zone 12, NAD83 coordinates, and a GIS shapefile of the sample locations with attributes.
- Well 56-32 Sludge XRF This is an Excel spreadsheet containing the results of X-ray fluorescence from well 56-32 sludge samples. The instrumentation used was a Olympus Vanta M series handheld XRF analyzer. A glass (SiO2) "blank" was analyzed at the beginning and end of each sample batch to detect contamination within the instrument. The standard 2711A was analyzed at the beginning and end of each sample batch to detect drift in instrument precision over time. Material was analyzed in a plastic cup with a prolene thin film cover for minimal interference.
Geomechanics
- Triaxial Test Data and Summary from EGI labs Six samples were evaluated in unconfined and triaxial compression, their data are included in separate excel spreadsheets, and summarized in the word document. Three samples were plugged along the axis of the core (presumed to be nominally vertical) and three samples were plugged perpendicular to the axis of the core. A designation of "V"indicates vertical or the long axis of the plugged sample is aligned with the axis of the core. Similarly, "H" indicates a sample that is nominally horizontal and cut orthogonal to the axis of the core. Stress-strain curves were made before and after the testing, and are included in the word doc. The confining pressure for this test was 2800 psi. A series of tests are being carried out on to define a failure envelope, to provide representative hydraulic fracture design parameters and for future geomechanical assessments. The samples are from pre-FORGE project well 52-21, which reaches a maximum depth of 3581 ft +/- 2 ft into a gneiss complex.
- Well 58-32 Stress Logging Data This spreadsheet consist of data and graphs from deep well 58-32 stress testing from 6900 - 7500 ft depth. Measured stress data were used to correct logging predictions of in situ stress. Stress plots shows pore pressure (measured during the injection testing), the total vertical in situ stress (determined from the density logging) and the total maximum and minimum horizontal stresses. The horizontal stresses were determined from the DSI (Dipole Sonic Imager) and corrected to match the direct measurements.
Geochemistry
- Soil Helium R/RA Data This is a Helium isotope R/RA values from the Utah FORGE area near Roosevelt Hot Springs.
- Soil Carbon Dioxide Data These are data from soil CO2 flux surveys done in the Utah FORGE study area near Roosevelt Hot Springs. Concentration is in units of ppm and is the final concentration of CO2 in the chamber after the up-to-2-minute flux measurement. Flux is in units of grams of CO2 per m^2.
Well 58-32 Well 78-32 Well 78B-32 Well 68-32 Well 56-32 Well 16A(78)-32 Well 16B(78)-32 Wells General