CO2 solubility in brine in silica nanopores in relation to geological CO2 sequestration in tight formations: Effect of salinity and pH

Molecular Dynamics Study on CO2 Storage in Water-Filled Kerogen Nanopores in Shale Reservoirs: Effects of Kerogen Maturity and Pore Size

“…After the discussion of the effect of kerogen maturity and pore size on water and CO 2 distributions and CO 2 storage mechanisms, we evaluate the CO 2 storage capacity S cap in various kerogen nanopores, which is defined as where m CO 2 is the molar number of CO 2 molecules in the analysis region within nanopores (see Figure a) and V pore is the effective pore volume obtained from helium uptake method. , More details can be found in the “Effective Pore Volume” part in the Supporting Information.…”

“…Three pore sizes (1, 2, and 4 nm) are designed to represent the kerogen nanopores, which are within the dominant pore size distribution in kerogen. , CO 2 and water molecules can freely move in the system via molecular diffusion. Once the system reaches equilibrium (chemical potentials of water and CO 2 in the nanopore and bulk water reservoirs are equal ,, ), the distributions of CO 2 and water in the nanopore and bulk water reservoirs can be obtained in the corresponding regions. To minimize the pore end effect, we only use the center region of the kerogen nanopore (6 nm in the center in the x -direction, marked as “analysis region” in Figure a) for analysis.…”

“…The Lennard-Jones (LJ) interaction between CO 2 and water molecules are adopted from Vlcek et al, who optimized the unlike-pair parameters. In our previous works, , we conducted a thorough validation of water and CO 2 force fields. It has been proven that the optimized SPC/E + EPM2 have excellent performances in terms of CO 2 bulk density, CO 2 –water interfacial tension, CO 2 solubility in bulk water, and CO 2 diffusion coefficient in bulk water.…”

“…Three dimensional (3-D) periodic boundary conditions are applied. System pressure is dictated by the density in the bulk CO 2 slabs as shown in Figure a from NIST Chemistry Web book as the CO 2 model used can accurately reproduce its density in the studied pressure range. , The pressure for each system can be found in Table , which is in the range of 187.2 ± 2.2 bar. The system temperature is controlled by a velocity rescaling thermostatat 353 K. Except for the interaction between water and CO 2 , the LJ interaction between other unlike pairs further than three bonds or in different molecules is calculated by geometric average .…”

“…The detailed review of the above works can be found in our recent work and a recent review paper . According to our recent works, , CO 2 solubility in water/brine in the kaolinite and silica nanopores strongly depends on the confinement surface chemistry. Therefore, CO 2 solubility in water in kerogen nanopores might be dependent on its maturity.…”