Methane (CH4) and carbon dioxide (CO2) are the two most common gases in oil and gas reservoirs, and their fluid properties are essential for reservoir evaluation, reservoir dynamics analysis, multiphase flow law study, phase behavior, and dissolution–dissolution characteristics. However, no experimental study has been conducted under high-temperature and high-pressure conditions. In this study, based on the self-developed high-temperature and high-pressure fluid property testing device, the changes of fluid properties for carbon dioxide (CO2) and methane (CH4) under high-temperature and high-pressure conditions were systematically discussed. The density, gas deviation factor (Z-factor), gas volume factor, and compressibility coefficient of CO2 and CH4 under different temperature and pressure conditions were measured experimentally. Results show that the fluid properties of CH4 and CO2 change significantly under high temperature and high pressure, especially in the process of phase transition. In addition, the experimental results of the miscible fluid of CO2 and CH4 show that with the increase of CH4 molar fraction, the properties of the mixed gas gradually move closer to the single-phase direction of CH4. These results not only provide theoretical support for understanding the dissolution behavior of fluids in oil and gas reservoirs but also provide a data basis for optimizing oil and gas field development strategies.
Jiang et al. (Thu,) studied this question.