Molecular Diffusion Coefficients of the Multicomponent Gas−Crude Oil Systems under High Temperature and Pressure

The molecular diffusion of an oil−gas system is a key factor to determine the mass transfer rate. The actual mass transfer between oil and gas is an unsteady-state process. In this paper, the diffusion coefficients of the N2-rich gas−crude oil, CO2-rich gas−crude oil, and CH4-rich gas−crude oil systems were determined at 60 °C and 20 MPa by the mutual diffusion model developed. Results of the coefficient measurements show obvious transit characteristics of the gas−oil diffusion processes. Both the required equilibrium time and the diffusion rate depend on not only the diffusion gas but also the diffusion system. The diffusion gas concentration affects the diffusion coefficients slightly.