Coals in the Late Cretaceous Laramie Formation and Early Tertiary Denver Formation hold some intrigue for coalbed methane potential by virtue of their measured gas contents and heating values, shallow depths, and areas of reasonable thickness and continuity.
Over the past 140 years, more than 300 historic mines were developed in the Denver Basin. The vast majority of them were underground mines in the Laramie Formation coals from which approximately 130 million tons of subbituminous coal was mined. Now that newly developed completion technologies are allowing commercial production from shallow, low rank coals, even the Denver Formation lignitic coals may be prospective.
The great diversity in coalbed methane plays proves that there are various reservoir characteristics critical to the successful methane production from low rank coals. Preliminary analyses of coal data collected by mining companies, combined with data collected from gas, oil, and water wells drilled in the Denver Basin, strongly suggests that further research and testing is required to demonstrate the economic feasibility of a coalbed methane play in the basin. In the meantime, the Colorado Geological Survey has compiled a GIS coalbed methane database that captures the data contained in numerous hardcopy publications released over the past twenty years. The GIS ArcView ™ format allows easy manipulation of important data such as isopach and structure maps, log cross sections, desorbtion and heating value data, locations of historic mines, coal analyses from those mines, and calculated gas content values.
Careful consideration must be paid to the shallow aquifers which surround these coals and into which thousands of water wells have been drilled. Regulatory and environmental factors will play vital roles in determining the producing potential for coalbed methane wells.