Development of formation-evaluation technology for coalbed methane. Annual technical report, December 1990-December 1991

Geophysical well log data can be used to estimate coal formation parameters necessary to optimize gas production in a reliable and cost-effective manner. The ability to estimate the methane resource and forecast production are critical keys in planning and developing commercial coalbed gas reservoirs. The report illustrates methods of obtaining seam thickness, coal quality (proximate analysis), gas content, and permeability using well log data. The size and frequency dependence of mechanical properties measurements acquired from core, log, and well tests are discussed. An understanding of how these reservoir mechanical properties are related impacts the design of stimulation treatments. The reliability of core measurements must be fully understood since these data are used as 'ground truth' for the evaluation of logging measurements and in development of the interpretation model. Coal core measurements are being evaluated for repeatability, accuracy and applicability to the oil and gas industry (since many measurements were developed for the mining industry). A parametric study was used to provide a tool to investigate the relative impact of variations of coalbed methane properties on the accuracy of well performance predictions. The study will be combined with expected variations of coalbed properties to construct a ranking of properties that canmore » be used to prioritize formation evaluation efforts.« less