Distinguished Lecture: "Coalbed Methane and Shale Gas: Insight from the Illinois Basin, USA"

Dr. Maria Mastalerz
Senior Scientist, Indiana Geological Survey

Pennsylvanian high volatile bituminous coals and the Devonian/Mississippian New Albany shales along with their associated gases have been studied using petrological, geochemical, and isotopic techniques to determine gas origin, timing of gas generation, and controls on gas distribution. Our study used gas and co-produced water samples from commercial coalbed methane (CBM) and shale gas-producing wells in the eastern part of the Illinois Basin in Indiana. Gas compositional and isotopic data indicate that CBM from coals at depths of up to 213 m (700 feet) is predominantly of microbial origin and contains less than 1 percent by volume of thermogenic gas.  Microbially generated CBM volumes show large variations across distances of hundreds of meters between and within individual coal seams, and no relationship exists between gas volumes and coal depth.   We suggest that these variations are either related to microbial extent of methanogenesis or to the degree of preservation of the gas. This, in turn, suggests that cleat and fracture characteristics of coal have a strong influence on the CBM distribution.  In the same area, gas from the New Albany Shale occurs at depths of up to 823 m (2700 feet) and ranges in origin from dominantly microbial to dominantly thermogenic. The type of gas from the New Albany Shale is controlled by depth, maturity, and salinity of formation water. Deeper, more mature and associated with higher-salinity water shales are associated with thermogenic gas, whereas shallower, less mature and lower-salinity shales tend to host microbial gas. Organic carbon content and the micropore volume of the New Albany shales serve as excellent predictors for microbial or thermogenic gas contents as long as there is no gas leakage due to the presence of conducting faults or shallow depths.

Maria Mastalerz holds M.S. degree (1981) in geology from Wroclaw University, Poland and Ph.D. degree (1988) in mining geology from Silesian Technical University, Poland. She was a postdoctoral fellow and a research associate at Department of Geological Sciences of the University of British Columbia, Vancouver, Canada, from 1990 till 1994. She has been employed as a senior scintist/coal geologist at the Indiana Geological Survey, Indiana University, since 1994, and is a member of Graduate Faculty of the Department of Geological Sciences since 1997.

Mastalerz’s area of expertise is coal geology, organic petrology and geochemistry. She has edited two books, several special volumes, and published more than 130 research papers.  She has been an Associate Editor for International Journal of Coal Geology since 1996. She is a recipient of several national and international awards, including the Geological Society of America Gilbert Cady Award for distinguished contribution to coal geology and Organic Petrology Award given by International Committee for Coal and Organic Petrology.