Geothermal/Geology and Minerals

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Geothermal Geology and Minerals

Geology and Minerals
Present, Potentially Affected

Geologic surveys must be conducted before plant construction can occur. The United States Geological Survey agency houses geological overviews of the United States, however for a specific area evaluation, each state has a geological survey agency to conduct site reviews. This comprehensive survey gathers data on several categories. A few categories are the following:

  • Geophysics: This test reveals available resources.
  • Physiography: This refers to the terrain’s texture, rock types, geologic structure and history of those structures.
  • Lithology: This pertains to an individual rock’s grain size, composition, mass, color and texture.
  • Hot Springs: This test gathers water chemistry data.
  • Thermal Conductivity: Measurements from several rock units show where the best site to drill is located.
  • Temperature: Borehole and gradients are evaluated for their underground temperatures.
  • Digital Geologic Mapping: 3D Seismic Mapping indicates where the natural resource is and how much of it exists. Topographical maps show an area’s contouring.
  • Phisher location: Finding these small slits in the bedrock shows geologists where wells can best access the natural resource.
  • Depth of Bedrock: These are the measurements between boreholes
  • Heat flow: This compares the heat transfer between test wells.
  • Seismic Risk: Fault line placement, phishers and bedrock types determine how susceptible an area is to earthquakes.

Geology and Minerals Impacts & Mitigation

Drilling activities pose risks above and below the surface level. Mitigating these impacts can elongate reservoir access and reliability.

Enhanced Geothermal Systems (EGS): The increased number of wells for injection and production increases the underground resources impacted. This also increases the probability of agitating existing minerals available for future mining.

To mitigate these impacts, slimhole drilling creates wells that are only 4-6 inches in diameter. Traditional geothermal exploration wells are 8-12 inches in diameter, making slimhole drilling an efficient option for reducing the land needed for well pads. If this alternative is not possible, existing wells not needed for production will remain inactive.

Seismic risk is also present. Fluid reinjection is known to cause subsidence or land surface sinking. To mitigate seismic effects of EGS, seismic monitoring programs equate for structural damage, noise pollution, and current regulations in place.

Industrial and metallic minerals: Sand, Gravel, clay and stone used for construction can agitate industrial and metallic minerals suited for mining. These minerals include, but are not limited to: copper, silver, cobalt, palladium, platinum, rhodium, ruthenium, iridium, and osmium, barite, garnet, bentonite, kaolinite, phosphates, diatomite, borax, gypsum, and potash. To minimize impacts, site assessment can indicate what minerals make up the bedrock. Slimhole drilling also decreases the area of impact.

Factors Affecting Geology and Minerals

Inhibiting factors include the following:

Land closures: Geothermal resources are considered a “fluid mineral resource” by the Bureau of Land Management (BLM) and the Fish and Wildlife Service (FWS) just like oil and gas, therefore, when restrictions on “leasable fluid minerals” exist, geothermal exploration and development is not allowed.

Geothermal on mining claims: It is possible to have mining and geothermal exploration occur on the same land simultaneously. Fill materials require a permit for both parties. All outstanding conflicts will be resolved with mining constituents and geothermal personnel via the BLM.