ABSTRACT. Concerns about global warming have motivated research and field projects for geologic sequestration of carbon dioxide by its injection into unmineable coal seams. We report x-ray CT measurements of coal heterogeneities and high-permeability regions in coal, bulk compressibilities and carbon dioxide concentration gradients produced by its diffusion through the coal matrix. Gravimetric measurements performed to examine the accuracy of the CT measurements of carbon dioxide concentrations also are discussed.
KEYWORDS: coal, heterogeneities, compressibilities, carbon dioxide, sorption
The study of coal by X-ray computerized tomography almost certainly began in 1982 (Maylotte et al., 1982). Since then, about twenty other studies have appeared.
In recent years, X-ray CT studies of coal frequently have been motivated by the potential for sequestration of carbon dioxide to reduce atmospheric concentrations of this greenhouse gas (White et al., 2005). Injection of carbon dioxide into coal seams may also lead to enhanced production of coalbed methane. For sequestration, the two technical parameters of most interest are the sequestration capacity, that is, how much carbon dioxide can be “stored” in a seam of coal, and the injectivity, ...