Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide–Moisture Conditions: A Molecular Dynamic Study

Abstract

In recent decades, shale gas, which has been regarded as a source of clean energy, is gradually replacing conventional energy. Shale gas adsorption in carbon dioxide (CO2)–moisture systems has been discussed in many previous studies; however, the intrinsic mechanism has not been clarified yet. In this work, the molecular dynamic (MD) method is adopted to study the adsorption behaviors of shale gas adsorption in the realistic kerogen nanoslit. The spatial density distributions of shale gas and different components have strong inhomogeneity. To reveal the heterogeneous adsorption mechanism, the potential of mean force (PMF) distributions of shale gas components are calculated on different target positions for the first time. The water (H2O) component prefers to adsorb on the oxygen-enriched position, as a result of the strong molecular polarity and hydrogen bond interactions. The CO2 component tends to adsorb on the carbon-rich site, which is the result of combining the van der Waals interaction and molecular polarity with kerogen walls. The potential energy contours are computed to verify the affinities between different components and the kerogen surface, and the potential energy difference can be observed between the bulk phase and adsorbed phase, which corresponds to the density and PMF analyses. The sensitivity analysis is also carried out to verify the above mechanism explanation. Higher temperature facilitates the desorption of shale gas, and higher pressure leads to more adsorption quantity. In the larger pore space, because of more content of H2O and CO2 molecules, the adsorption amount of methane (CH4) decreases. More content of CO2 is conducive to the desorption of shale gas, verified by cases in various component proportions.

Molecular Dynamics Simulations of Ion Transport through Protein Nanochannels in Peritoneal Dialysis

“…With a mesh size of 0.5 Å, the simulation domain was chunked, and the density value was derived by counting the atomic numbers present in each chunk within the simulation domain. Due to van der Waals interactions between carbon and total fluid atoms, density peaks appeared at the interface between the fluid and graphene layers, and consequently, multilayers formed, as proved in previous studies [ 38 , 39 ]. It can be observed that the sodium ions are concentrated on the left side of the electrode due to the electric field force.…”

“…This structure also has a confined effect on the fluid molecules, especially at the beginning and ending positions of the nanochannel, which is similar to the phenomenon of ion rejection. between carbon and total fluid atoms, density peaks appeared at the interface between the fluid and graphene layers, and consequently, multilayers formed, as proved in previous studies [38,39]. It can be observed that the sodium ions are concentrated on the left side of the electrode due to the electric field force.…”

Pore‐Scale Modeling of Coupled CO2 Flow and Dissolution in 3D Porous Media for Geological Carbon Storage

“…Geological sequestration of carbon dioxide (CO 2 ) has been considered a promising solution to mitigate the adverse effects of climate change by stemming the increase in atmospheric CO 2 (Bachu, 2000; Falkowski et al., 2000; J. Liu et al., 2022). There are several options for sites used for geological CO 2 storage, such as deep saline aquifers, depleted oil and gas reservoirs, unmineable coal seams, etc.…”

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Geological sequestration of carbon dioxide (CO 2 ) has been considered a promising solution to mitigate the adverse effects of climate change by stemming the increase in atmospheric CO 2 (Bachu, 2000;Falkowski et al, 2000;J. Liu et al, 2022).

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Virtual Special Issue of Recent Advances in Shale Gas Exploration and Exploitation

“…They found that CH 4 surface adsorption is strongly dependent upon surface wettability and that adsorption capacity in organic-rich shales can be much higher than that in inorganic-rich shales. Liu et al 18 investigated CH 4 adsorption in the presence of CO 2 and moisture in realistic kerogen slits using MD simulations. They observed that H 2 O prefers to adsorb on the oxygen-enriched position and CO 2 tends to adsorb on the carbon-rich site.…”