Carbon Dioxide and Methane Sequestration in Organic-Rich Shales: Nanoscale Insights into Adsorption and Transport Mechanisms

Abstract

Shales are clastic sedimentary rocks consisting mainly of clays, quartz, calcite, and fragments of organic matters. The latter is present as finely dispersed inclusions within the shale matrix. Organic matters, also known as kerogen, are microstructures with their petrophysics being characteristically different from other constituents in the shale matrix. Despite their existence as micro- and nanoscale constituents, kerogen is capable of storing a significant amount of gas in the sorbed form due to its relatively large surface area. Kerogen can be created on a computational platform to delineate crucial reservoir aspects such as porosity, pore size distribution, adsorption behavior, and self-diffusivity. Kerogen's characteristics were found to be characteristically different from typical sedimentary rocks. These properties are crucial in the assessment of kerogen's storing capacity. In this study, several kerogen prototypes were formed to evaluate the microporous media of organic-rich shales for their potential of sequestrating greenhouse gases such as methane and carbon dioxide. To add to the discourse on the kerogen assessment, a concise review of the well-known storage and transport models was summarized and presented. These models are different from the classical ones applied to the typical porous media. Additional parameters accounting for the non-Darcian transport and the storage of sorbed fluid are used.