Microcosmic gas adsorption mechanism on clay-organic nanocomposites in a marine shale

Marine sourced clay minerals and organic matter enrichment as clay-organic nanocomposites within shale has attracted attention because of their changeable surface areas, nanoporosity, and methane adsorbability. Here marine shale samples were used to investigate the characteristics of clay-organic nanocomposites and their impact on gas adsorption response. The results show that organic nanolayers mainly occur as nanometer intercalations with clay nanolayers. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images provide direct evidence of the parallel aligned clay-organic nanocomposites with an approximate thickness of each organic and clay nanolayer and the positive correlations between their morphology, occurrence, and relative content. However, such clay-organic interactions are significantly damaged by structural deformation, accompanied by a weakening in gas adsorption capacity. We suggest that the naturally occurring structures that hydrocarbon molecules are attached or resided in fine-grained marine shales are predominantly associated with clay-organic nanocomposites, which play an important role as adsorption carriers. Moreover, the clay-organic association may be an effective mechanism of gas adsorption. These observations and investigations could challenge the common perception that discrete kerogen and clay minerals are the major components for gas adsorption. (C) 2020 Elsevier Ltd. All rights reserved.