Evaluation of coalbed-methane reserves involves different techniques

Abstract

The gas-production mechanisms in coalbeds are significantly different than in conventional reservoirs. Because of this and other reasons, coalbed methane is considered an unconventional gas resource. According to the authors, when evaluating a prospective coal-bed methane site, there is no substitute for site-specific information systematically gathered from wells as a site is developed. The first few wells are the key link in site characterization. A sizeable collection of information can be constructed with regional geologic data and logging coring, and testing of one well. This information can be used to help make sound decisions about the production potential and economic viability of the site, design hydraulic-fracture treatments, and provide the preliminary lay-out and spacing of the field. Conventional and specialized methods, including well logging, core desorption and analysis, and well testing, are available to collect this information. The STEP (short term permeability test) is discussed as are other well tests. Reservoir simulation is presented as the most reliable method of prediction.