Illinois Coal Gas Update- Cradle to Production
Morse, David G., Ilham Demir, Thomas R. Moore
Illinois State Geological Survey, Champaign, IL
Development of coalbed methane resources typically proceeds in a predictable way with multiple decision points. Illinois is in the very early evaluation stage for both mine gas and seam gas projects. At the beginning of 2004, 7 to 10 mmcf/d from a multi-well, mine gas project was the only commercial CMM in Illinois. Indiana has one 30-well field, the only commercial seam gas in the Illinois Basin to date.
Seam gas efforts in Illinois have expanded from initial gas content and permeability testing of coals to production pilots. Gas contents vary from coal to coal, area to area and with depth. Typical values range from 60 to 90 scf/ton (dmmf), but values as high as 170 to 200 scf/ton have been measured. No public permeability data has been published in scientific literature although informal operator values range from 1.8 to 300 md.
CBM drilling activity has been accelerating. In Illinois alone in 2003, 30 CBM-related wells were permitted, four times that in 2002. At the same time there were 16 new CMM wells. At the start of 2004, there were at least four confidential multi-well pilots.
Optimal stimulation design remains a hurdle to overcome. Most wells have been conventionally cased, perforated and hydro-fraced with varying amounts and sizes of sand injection rates. New techniques designed to avoid damaging the coal will be tried, such as air drilling, nitrogen fracs, and horizontal or multilateral wells. Results from these new techniques could kick the play wide open.
AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004