High-pressure methane adsorption behavior on deep shales: Experiments and modeling

Understanding methane adsorption behavior on deep shales is crucial for estimating the original gas in place and enhancing gas recovery in deep shale gas formations. In this study, the methane adsorption on deep shales within the lower Silurian Longmaxi formation from the Sichuan Basin, South China was conducted at pressures up to 50MPa. The effects of total organic carbon (TOC), temperatures, clay minerals, and moisture content on the adsorption capacity were discussed. The results indicated that the methane excess adsorption on deep shales increased, then reached its peak, and finally decreased with the pressure. The excess adsorption data were fitted using the adsorption models, and it was found that the Dubinin-Radushkevich (D-R) model was superior to other models in predicting the methane adsorption behavior. The methane adsorption capacities exhibited strong positive correlations with the TOC content and negative relationships with clay minerals. The methane excess adsorption decreased with the temperature, while the opposite trend would occur once it exceeded some pressure. The presence of the moisture content on deep shales sharply decreased the methane adsorption capacities, and the reduction of the adsorption capacity decreased with the pressure. The moisture would occupy the adsorption sites in the shale pores, which could result in the methane adsorption capacity that decreased.

Automated summary

The study found that methane adsorption on deep shales is influenced by various factors, including total organic carbon content, temperature, clay minerals, and moisture content. The TOC content is positively correlated with methane adsorption capacity, while the clay mineral content is negatively correlated. Increasing temperature decreases methane adsorption capacity, but the trend may reverse at certain pressures. The presence of moisture significantly reduces methane adsorption on deep shales, with the reduction in adsorption capacity decreasing as pressure increases.