Coalbed Methane in the Forest City Basin

May 1993

"Coalbed methane has long been considered a hazard and is well known as a 'greenhouse' gas that is vented directly to the atmosphere from many sources. As the United States considers its options for energy mix in the next century, and as environmental policies curtail venting, understanding of the occurrence and distribution of energy gases such as methane and its coproducts will become increasingly important. Coalbed methane in the Forest City basin may provide a potentially significant contribution to the Nation's future energy needs."

Brenda Pierce, U.S. Geological Survey

A coalbed methane industry in the Forest City basin may be of significant economic value.

Coalbed methane as an exploited energy resource in other parts of the country has proven to be of great economic value to regional and local governments, and hence to the Nation. Local land owners in the four-State area of Missouri, Kansas, Iowa, and Nebraska, also may receive economic benefit since most of them have retained their mineral rights. An increasing level of interest from coalbed methane producers has spurred interest in the Forest City basin as a potential producer of commercial quantities of methane.



Coalbed methane is a clean-burning fuel often found in economic quantities in coals of many ranks.

Methane produced in coal is a byproduct of the coalification process in which plant material is converted to coal, and much of the gas that is generated is retained within the coal matrix. Although minor differences in geologic conditions alter production methods, coalbed methane is produced, transported, and used in nearly the same way as is natural gas produced from conventional gas and petroleum fields. Large quantities of coalbed methane are presently produced from deep coals in the Black Warrior basin of Alabama and the San Juan basin of Colorado and New Mexico.



U.S. Geological Survey (USGS) studies demonstrate that significant coal resources are present in the Forest City basin.

The USGS, in cooperation with the State geological surveys of Missouri, Kansas, Iowa, and Nebraska, conducted a preliminary assessment of geological information in the Forest City basin. This assessment was necessary because insufficient geological data were available in the deep coals to accurately evaluate the potential for coalbed methane in the basin. Based on analytical test results, drill cores, and geophysical logs, this study concluded that the basin contains substantial amounts of coal in numerous beds that are too deep and too thin to be mined for their coal content by conventional methods. Methane analyses performed on samples from 11 coals taken from beds in Kansas and Missouri confirm that coalbed methane is present. This conclusion is also supported by reports of excessive methane occurrence (explosions) in shallow, now-abandoned underground coal mines in Missouri, and the presence of regional and local geological features that displace coal-bearing rock units, perhaps increasing coal rank.



USGS scientists examined coal quality and rank, and coalbed methane composition on samples taken from selected coal beds.

Although the amount of these data is insufficient for a thorough assessment of the coalbed methane potential, the data collected indicate that methane is present in the basin, and provide reasons for additional study. The rank of the coals studied in the Forest City basin, as determined by detailed analytical techniques, in combination with the gas analyses, is a promising indicator for coalbed methane production and storage, and therefore production.



USGS in cooperative studies use oil and gas well data to assess coal resources.

A large number of oil and gas wells have been drilled in the Forest City basin that are useful for estimating the distribution and amount of coal. Kansas has over 1,000 wells drilled to at least 275 meters (900 feet), and an additional 4,000 wells have reached shallower total depths. Missouri has well logs from about 5,000 wells; Nebraska has nearly 600 wells in their portion of the basin; and Iowa provides several hundred well logs from its portion of the Forest City basin. Analysis of well data will establish a better correlation of coal beds and indicate areas of thicker coal beds. Cores of coal beds can be taken in appropriate locations and tested for methane composition and quantity and for coal chemistry.



USGS studies confirm that geologic conditions in the Forest City basin are favorable for coalbed methane.

If coalbed methane is found to be present in commercial quantities in the Forest City basin, then these deep coals would represent a significant energy source. Geologic similarities with the Black Warrior basin include depth of coal with methane potential, numerous thin coal interspersed with thin sequences of sandstone, shale, and limestone, and equivalent geologic age of the coal and surrounding rocks. Initial indications are that coal rank is somewhat lower in the Forest City basin than in the Black Warrior basin.

For More Information:

Email: bpierce@usgs.gov

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Maintained by L. Friedrich Last updated 20-Oct-1997