CO2 diffusion in n-hexadecane investigated using magnetic resonance imaging and pressure decay measurements

Abstract

A method combining magnetic resonance imaging (MRI) and dual-chamber pressure decay (i.e., the pressure–volume–temperature method) was used to measure the diffusivity of CO₂ in bulk n-hexadecane, a representative oil, at 21 °C. Images of the proton density of n-hexadecane were obtained by MRI using a high magnetic field and high resolution, and the pressure decay was recorded. Overall diffusion coefficients of CO₂ were calculated from both pressure decay and MRI intensity data. The two results showed good agreement. MRI was successfully used to study the diffusivity of CO₂ in n-hexadecane. The change of image density (i.e., proton density) demonstrates that the oil density decreases as CO₂ diffuses into it. The finite volume method was applied to the images obtained by MRI, allowing the diffusion coefficient of CO₂ to be directly obtained. MRI methods can measure the unsteady-state local diffusion coefficient and overall diffusion coefficient of such systems.