Determining the volume expansion of the CO2 + octane mixture using a fused silica capillary cell with in-situ Raman spectroscopy

Accurate expansion data for CO 2 in petroleum model compounds (e.g., alkanes, cycloalkanes and aromatics) are fundamental information for CO 2 sequestration and enhanced oil recovery in oil reservoir. In this study, the volume expansion of the CO 2  + octane mixture was measured using a fused silica capillary cell with in situ Raman spectroscopy. A section of water was loaded between octane and CO 2 in the fused capillary tube to seal the octane whilst allowing the diffusion of CO 2 into the octane. Raman spectroscopy was applied during our experiments to verify that the CO 2  + octane mixture reached phase equilibrium. Moreover, a good quadratic relationship was observed between the Raman peak intensity ratio and volume expansion factor. It was verified that this method can be used not only just to obtain more accurate experimental data, but also to protract additional volume expansion factor curves or curved surfaces from measured Raman peak intensity ratio using this equation. Over an extended temperature and pressure range, this method was thus shown to be more efficient and accurate than the traditional pressure–volume–temperature methods.