Coal stockpile at the Bowie Mine #2, Delta County, Colorado, June 2004. Photo credit: Chris Carroll for the CGS.

Fossil Fuels

Colorado has a long history of fossil fuel production from coal to petroleum and natural gas to coalbed methane and oil shale. Current detailed statistics may be found under the US Energy Information Administration’s Colorado Energy Overview.

Coal extraction has a long and complex history in Colorado. The estimated value of Colorado coal production in 2017 was $623 million. Although coal production slightly increased in 2017, the overall decreasing trend in coal production is due primarily to the nationwide increased use of natural gas and renewable energy. The state fell from the 11th largest coal producer in 2015 to the 13th in the U.S. in 2016. Colorado coal is mostly bituminous and sub-bituminous—with both underground and surface mines currently in operation on the Western Slope—and is characterized as of high heat, low sulfur, low to medium ash, and low mercury content.

Coalbed methane (CBM) is natural gas produced from subsurface coal deposits. Much of the technology uses standard well-drilling and production techniques. The primary difference is the total usage of water in the process. In most cases, water must be pumped out of the formation in order to allow the methane that is adsorbed onto the coal particles to escape and travel to the surface via extraction wells.

Typical natural gas wells reach a peak and then begin a volumetric decline in production relatively rapidly. Coalbed methane wells behave differently. They increase in production for a long time as more and more water is removed from the strata. Decline in production does not usually begin until late in the life of the well.

As of 2008, Colorado was responsible for more than one-fourth of all coalbed methane produced in the United States and we have the largest reserves of CBM. Coalbed methane output accounted for about one-half of Colorado’s natural gas production at that time.

Oil forms from kerogen, a mixture of organic compounds in sedimentary rocks. It is most abundant in shales. Shales are analyzed and characterized as potential “source rocks” for oil based largely on their TOC (total organic content).

Colorado has the world’s largest resources of oil shale, by far. Oil shale is actually the rock marlstone which contains kerogen, a precursor to oil. The kerogen must be heated to more than 750 degrees to convert it into oil because it was never buried deeply enough for nature to convert the kerogen to oil.

People have been trying to economically produce oil from this rock for more than a century. Indeed, the CGS issued a report in 1921 entitled, Oil Shales of Colorado. Thus far, despite another significant burst of activity in the 1980s, technological and economic conditions have not combined to support a sustained oil shale industry in the state.