Coalbed methane potential of the Seelyville Coal Member in Indiana

By

Drobniak, A., M. Mastalerz, N. Eaton, and J. Rupp

Indiana Geological Survey, Indiana University, 611 North Walnut Grove, Bloomington, IN 47405

     The Seelyville Coal Member, Linton Formation (Pennsylvanian) is one of the most extensive and thick coals in Indiana. Because of its high ash and sulfur content, however, it has become less attractive for mining. Currently, it is being considered as a major target of coalbed gas exploration in Indiana because it is relatively thick (from 1 to more than 9 feet) and occurs at depth up to 1400 feet.

     Coal thickness, seam depth, rank, and gas content have been used to evaluate the coalbed gas potential of the Seelyville Coal. Coal rank has been determined based on the heating value (Btu/lb, daf basis) and vitrinite reflectance. Gas content was mapped using values calculated from Kim’s formula (1977). The calculated values have been compared to available direct determinations of gas content.            

     In Indiana, coal rank increases southwestwardly tower the center of the Illinois Basin.  Exceptions to this trend occur in some parts of Vigo and Greene Counties where coal rank is higher. Calculated gas contents generally follow the trend in rank increase, with the values ranging from 25 scf/ton in Vigo County to 333 scf/ton in some parts of Posey County. Measured values of the gas content tend to be lower that the calculated values, which could be related to gas depletion either at shallow depth or in zones associated with porous clastic rocks.