Geomechanical attributes of reconstituted Indian coals under carbon dioxide saturation

Geologic sequestration of anthropogenic greenhouse gases into deep geological reservoirs like coal seams has caught attention worldwide. The potential of coal to adsorb CO₂ and preferentially release methane partly offsets the cost of capture, transport and storage of the gases. For such projects, it is important to understand the influence of geomechanical properties of coal on cap rock integrity and long term safety. However, coal being highly heterogeneous from basin to basin, seam to seam, and those within the seam, it is difficult to determine the properties of the complete seam. This makes it difficult to characterize and understand the coal properties for developing ideal models for optimization of sequestration process and generating useful correlations. Therefore, in this study, reconstituted bituminous coals were used in the laboratory experiments to overcome the problem of heterogeneity. It was found that the mechanical properties of reconstituted coal like density, strength, etc. were quite homogenous as compared to the natural samples. The samples were tested for their geomechanical attributes after sustained exposure in a carbon dioxide environment. The saturated strength of coal were nearly 3–4% lesser than the strength of intact reconstituted coal specimens. This study may be very useful and extended for further investigation on coals overcoming the difficulty of the heterogeneity.