Comparison of Lost Gas Projections in Coalbed Methane

Noel B. Waechter, George L. Hampton, III, and James C. Shipps, Hampton, Waechter & Associates, LLC and John P. Seidle - Sproule Associates, Inc., Denver, CO

Presented at the AAPG Rocky Mountain Section Meeting -Rocky Mountain Natural Gas 2004, Denver Colorado August 9 to 11, 2004


Linear projections for estimating lost gas were first applied to coal cores by the U.S. Bureau of Mines in the early 1970’s, and have been used widely by the coalbed methane industry since that time. The observed linearity to early parts of some desorption curves may be related to temperature disequilibrium and concomitant increases in diffusion rates as coals warm back up to reservoir temperature inside the canisters. The authors examine three examples of upper Cretaceous coal and demonstrate that with increasing lost gas times, polynomial fits for lost gas provide more consistent and more accurate estimates of lost gas.