BEST PRACTICES FOR MULTI-ZONE COALBED METHANE COMPLETIONS

摘要

The Powder River Basin, located in northeast Wyoming, and southeast Montana, has been the location of the nation's fastest growing development of coal bed natural gas (CBNG). Production of CBNG, to date, from the tertiary-age Fort Union Formation has been in the east and central portion of the basin, near Gillette, Wyoming, with recent development efforts targeting the deeper basin center. Of the 17,000 CBNG wells in the PRB, over 9,600 produce less than 30 mcf/day. CBNG operators in the PRB are now attempting to implement multizone completions, since they are experiencing a low success rate using the current practice of single-seam completions (while bypassing several thinner seams). While multizone completions should enhance economic gas production, reservoir conditions in the PRB, which tend to be shallow, undersaturated coals of highly variable critical desorption pressure (CDP) and gas content (GC) surrounded by water-bearing aquifers, have not proven suitable for multizone completions. To date, results from multizone completions have not been widely favorable.