The influences of composition and pore structure on the adsorption behavior of CH4 and CO2 on shale
2021
Wang, Xiangzeng | Zhou, Junping | Sun, Xiao | Tian, Shifeng | Tang, Jiren | Shen, Feng | Wu, Jinqiao
CO₂ enhanced shale gas recovery (CO₂-ESGR) has attracted extensive attention as it can improve the shale gas recovery efficiency and sequestrate CO₂ simultaneously. In this study, the relationship between mineral composition, pore structure, CH₄ and CO₂ adsorption behavior as well as selective adsorption coefficient of CO₂ over CH₄ ([Formula: see text]) in marine and continental shales at different temperatures was investigated. The results illustrated that shale with higher total organic carbon (TOC), higher clay minerals and lower brittle mineral contents has a larger micropores and mesopores volume and specific surface area. TOC content was positively correlated with fractal dimension Df. Both CH₄ and CO₂ adsorption capacity in shale have positive correlations with TOC and clay mineral content. CO₂ adsorption capacity of the all the tested shale samples were greater than CH₄, and the [Formula: see text] of shale were larger than 1.00, which indicated that using CO₂-ESGR technology to improve the gas recovery is feasible in these shale gas reservoirs. A higher TOC content and in shale corresponding to a lower [Formula: see text] due to the organic matters show stronger affinity on CH₄ than that on CO₂. Shale with a higher brittle mineral content corresponding to a higher [Formula: see text], and no obvious correlation between [Formula: see text] and clay mineral content in shale was observed due to the complexity of the clay minerals. The [Formula: see text] of shale were decreased with increasing temperature for most cases, which indicated that a lower temperature is more favorable for the application of CO₂-ESGR technique.
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