Colorado Geological Survey
1801 Moly Road, Golden, Colorado, United States

The Colorado Geological Survey (CGS) is a non-regulatory state government agency situated within the Colorado School of Mines. We provide a wide range of science-driven services—this website being one—bringing the best of Colorado geoscience to the public.

Our Mission

To help reduce the impact of geologic hazards on the citizens of Colorado; to promote responsible economic development of mineral and energy resources; to provide geologic insight into water  resources; and to proffer sound geologic advice and information to a variety of constituencies.

Energy

Colorado has abundant energy resources—from renewables: wind, solar, hydroelectricity, and geothermal; to fossil fuels: oil, natural gas, coal; along with uranium. The state presently generates electricity from a combination of coal, natural gas, and, increasingly, renewable sources. Geology plays an important part in locating appropriate sites and raw materials for many energy resources, as well as determining safe disposal sites for the waste products of energy development.  The CGS performs a lead role in conducting the geological research that informs energy resource development across the state. Scientific studies that the CGS has run on a state-wide or location-specific basis include geologic mapping of potential oil- and gas-bearing rock formations, understanding geothermal heat flows, and the (historical) characterization of coal reserves. The CGS is not a resource regulatory agency, rather, it provides an important research platform to support other state agencies that do regulate the use of public resources. Every year, the CGS publishes an annual report on the state of the mineral and energy industry in Colorado and historically produced a range of reports on oil and gas, oil shale, coalbed methane, uranium, and geothermal resources. We also prepare an annual chapter on the mineral and energy sectors of Colorado’s economy for CU-Boulder’s Leeds School Business Economic Opportunity Forum annual forecast.

Geothermal

Geothermal energy, or heat from the earth, is an excellent resource. It is sustainable, works 24/7, and has a minimal carbon footprint. One should be clear when discussing geothermal energy about which type is being discussed: direct use, electrical generation, heat pumps, or enhanced geothermal systems (EGS).

Historically, Colorado has been considered to have geothermal resources suitable only for direct-use applications. Until very recently, Colorado’s geothermal potential for generating electrical power has been assigned little promise. This appears to be based more on a lack of study, rather than on sound science.

Prior to 2000, the CGS published 33 reports on various aspects of Colorado’s geothermal energy resources. With today’s improved technology, we are taking another look at our geothermal resources and are in the process of issuing revised and updated maps. It is exciting to see a number of companies actively looking at the potential for generating electricity from geothermal in several parts of the state.

Geothermal means, literally, earth-heat (Greek: geo + therme). Heat is a form of energy. Geothermal heat becomes an energy resource when we can use the heat to our advantage. It is an excellent resource that is sustainable, works 24/7, and has a minimal carbon footprint. Most of the Earth’s heat is deep inside the Earth, beyond the reach of technology to extract. At relatively shallow depths, depending on the temperature, the heat may be economically extracted and used.  At shallow depths the Earth may be used as a heat reservoir. In terms of magnitude, the Earth receives more than a thousand times more energy from the Sun than is lost from its internal reserves. However, the solar energy is lost back to space on a daily and seasonal basis. Except for small microclimates around hot springs and active volcanoes, the Sun controls the temperature of Earth’s surface and this temperature generally decreases with latitude from the equator to the poles and with elevation. Soil and rocks are poor conductors of heat and below around seven feet (2 m) below the surface, the annual and seasonal variations in surface temperature are damped out and the temperature is steady at approximately the mean annual ground surface temperature. Although this temperature is defined by the solar energy balance, it is soil and rock properties that make this zone good for use as a heat reservoir. Ground-source heat pumps (or geoexchange heat pumps) use this zone for heat storage and retrieval.  Where subsurface temperatures are significantly hotter than the surface temperatures heat may be extracted for surface use. This situation would occur where the geothermal gradient increases the temperature above the surface temperature. This difference may be only a few degrees, or even a few degrees above winter surface temperature for some direct use applications, to a few hundred degrees Celsius for geothermal electricity generation.  A further requirement for “elevated” subsurface temperatures to be a resource is that there must a mechanism by which the heat can be brought to the surface. For some resources the mechanism may be natural, such as hot springs or artesian (naturally flowing) wells. Other sites may require the drilling of a well and pumping. At many sites high subsurface temperatures are found but the rocks lack sufficient permeability (pathways for fluid flow). These rocks may require artificial fracturing or down-hole heat-exchangers to extract the heat. Research on new technologies to extract heat from potential geothermal reservoirs is continuing.  Areas in Colorado that are prime for new geothermal exploration include the Rico Dome structure in southwest Colorado, Mount Princeton Hot Springs, Waunita Hot Springs, and the San Luis Valley. These exploration targets represent potential sites with high heat flow. There are currently no geothermal electrical power generating facilities in Colorado.

Coal