Diffusion characteristics of shale mixed gases on the wall of microscale fractures

Shale reservoirs are rich in organic and inorganic matter, causing a large amount of gas to exist on the surface of microscale cracks in an adsorbed state. Revealing the surface diffusion characteristics of adsorbed gas is of great significance for the microscale numerical simulation of shale gas reservoir. In this paper, the unconventional gas reservoir is taken as the research object, and the characteristics of gas surface diffusion on surface wall of microscale fractures is systematically studied. There are two innovations in this paper: (a) the characteristics of gas surface diffusion inside the planar microscale fractures are analyzed; (b) The influence of mixed gas effect on gas surface diffusion is considered. Research results show that: (a) when the fracture opening is 2 nm or 5 nm, the influence of the opening of microscale fractures on the thickness of adsorption layer can be ignored. (b) The interaction between components refers to the frictional force generated by the relative motion of molecules. (c). The magnitude of frictional force is related to the Maxwell Stefan diffusion term and is proportional to the velocity difference. Due to the interaction between components, fast-moving molecules will accelerate the movement of slow-moving molecules.

Automated summary

This paper systematically studies the characteristics of gas surface diffusion on the surface wall of microscale fractures in unconventional gas reservoirs. Two innovations are analyzed: the characteristics of gas surface diffusion inside planar microscale fractures and the influence of mixed gas effect on gas surface diffusion. The research results show that the fracture opening has a negligible influence on the thickness of the adsorption layer when it is 2 nm or 5 nm.