Molecular insight into competitive adsorption of methane and carbon dioxide in montmorillonite: Effect of clay structure and water content

Understanding methane/carbon dioxide partitioning in clay nano- and meso-pores with constant reservoir composition molecular dynamics modeling

“…These results are in agreement with recent GCMC simulation studies of CO 2 /CH 4 adsorption in the interlayers of Na-montmorillonite at 318 K and P fluid = 0 to 300 bars. 48 Importantly, the CO 2 /CH 4 ratios at small pore sizes (o23.0 Å) are in excellent agreement with the selectivity parameters obtained from recent GCMC simulation studies at similar thermodynamic conditions (323 K and P fluid = 100 bar). 49 The probability density profiles (PDPs) of CO 2 and CH 4 in the pores perpendicular to their surfaces show that the changes in their concentrations with pore thickness are due to preferential sorption of CO 2 and structuring of the fluid near the pore surfaces (Fig.…”

“…The results parallel the preference of other inorganic shale components (e.g., calcite and quartz) for CO 2 relative to CH 4 , suggesting that for oxide and oxysalt materials, CH 4 adsorption is relatively weak and its filling of pores bounded by them occurs by a passive, space filling mechanism. [48][49][50][51][52] The organic component of shale known as kerogen is commonly thought to contain much of the CH 4 , but recent GCMC studies support the conclusion that although it prefers CO 2 relative to CH 4 , the behavior of these species is strongly dependent on the chemical composition, functionality, moisture content and pore structure of the kerogen. 74,75 Overall, the structure, dynamics and energetics of the adsorption environments of CO 2 , CH 4 , other hydrocarbons, and H 2 O in kerogen have not been well explored, and the CRC-MD methods used here can be readily applied to help address these important questions.…”

“…[45][46][47] Recent Grand Canonical Monte Carlo (GCMC) calculations, for instance, have shown preferential adsorption of CO 2 over CH 4 in the interlayers of dry Na-montmorillonite and other inorganic shale components as functions of temperature (313-373 K) and pressure (0-20 MPa). [47][48][49][50][51][52] In shales and other sedimentary rocks, pores have a wide range of sizes, and the effects of pore size on CO 2 / CH 4 partitioning are poorly understood. This paper presents the results of a computational molecular dynamics (MD) modeling study of the partitioning of CO 2 and CH 4 between bulk fluid and slit-like nano-and meso pores from 4 to 73 Å thick and the structure of the fluid in those pores.…”

A novel method to calculate the gas adsorption of mixed minerals

“…This paper focuses on adsorption of methane on four pure clay minerals (Ill, Mont, Chl, and Kaol) and their mixture. The shale is rich in inorganic clay minerals [6] and plays an important role in the adsorption of methane on shale [7]. Clay minerals contribute differently to the adsorption capacity, and their adsorption depends on the type of clay [8][9][10][11][12].…”

“…The more micropores and nanopores the clay minerals have, the larger the specific surface area, because more surface area is associated with smaller pores, which can provide more surface adsorption sites for methane [8]. As the pore size of the clay increases, the adsorption rate of methane decreases [6]. It was concluded by Ross and Bustin [18] that clay minerals with higher pore volume and larger specific surface area have greater adsorption capacity.…”