地质科技通报 (May 2023)
Surface wettability of oxygen-containing functional group-modified graphite and its effect on gas-water distribution
Abstract
Wettability is one of the important physical properties of reservoir rock surfaces, and it is a key factor affecting capillary force, relative permeability, bound water saturation and fluid micro-distribution. Based on the molecular simulation method, this paper made a study of the wetting behavior of a graphite surface (organic surface) modified by the oxygen-containing functional groups and the distribution characteristics of the methane-water system in organic slit pores. The results showed that the interaction energy between the water molecules and the surface decreased and the wetting contact angle of the organic matter surface increased with the increase in the oxygen-containing functional groups; with the increase in the temperature, the interaction energy between the organic matter surface and the water molecules increased, and the wetting contact angle decreased; in the graphite slit pore model with symmetrical C/O ratio, water molecules were symmetrically distributed near the wall of oxygen-containing functionalized graphite, and with the decreasing in the C/O ratio, the relative concentration of water molecules increased and the diffusion coefficient decreased, while methane molecules were clustered in the center of the pore. In the graphite slit pore model with asymmetric C/O ratio, the water molecules were asymmetrically distributed near the wall of the oxygenated functionalized graphite, while the methane molecules were clustered in the center of the pore, where the side with a low C/O ratio had strong hydrophilicity on the wall and a high relative concentration of water molecules, while the side with a high C/O ratio had strong hydrophobicity on the wall and a low relative concentration of water molecules. The research findings were extremely significant to make a study of the influences of shale reservoir characteristics.
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