Phase Behaviour and Physical Properties of Dimethyl Ether (DME)/CO2/N2/Water/Heavy Oil Systems Under Reservoir Conditions

Abstract

Abstract The application of a mixture of dimethyl ether (DME) and flue gas is a promising method to recover heavy oil as DME is first-contact miscible with hydrocarbons and partially miscible with water, CO2 can accelerate mass transfer, and N2 can boost the energy in a depleted heavy oil reservoir; however, phase behaviour and physical properties of DME/CO2/N2/water/heavy oil systems are still not well quantified. In this study, theoretical and experimental techniques are developed to determine phase behaviour and physical properties of the aforementioned systems at pressures ranging from 2 MPa to 20 MPa and temperatures spanning from 352.15 K to 433.15 K. In addition to collecting experimental data from the public domain, eight constant composition expansion (CCE) tests are carried out. A thermodynamic model that incorporated the Peng-Robinson equation of state (PR EOS), a modified alpha function, the Péneloux volume-translation strategy, and the Huron-Vidal (HV) mixing rule is used to reproduce the measured phase equilibria data. The tuned binary interaction parameters (BIPs) are utilized in conjunction with the thermodynamic model to accurately predict saturation pressure (Psat) and swelling factor (SFs) with a root-mean-squared relative error (RMSRE) of 3.32% and 0.57%, respectively. Furthermore, the recently proposed model demonstrates its high accuracy in forecasting the oleic/vapor (LV) two-phase boundaries for N2/heavy oil systems and DME/CO2/heavy oil systems with an RMSRE of 1.93% and 2.77%, respectively. Similarly, the accuracies of the predicted aqueous/oleic/vapor (ALV) three-phase boundaries for N2/water/heavy oil systems and DME/CO2/water/heavy oil systems are 2.85% and 3.47%, respectively. Besides, water is found to increase the phase boundaries for DME/CO2/heavy oil systems but decrease those of N2/heavy oil systems and DME/CO2/N2/heavy oil systems. Additionally, as the concentration of N2 and CO2 in the feed mixture is increased, its Psat is increased. In this work, new PVT experiments are conducted to evaluate the impact of adding DME/CO2/N2 into the heavy oil bulk phase in the absence and presence of water. The developed model accurately characterizes the phase boundaries and physical characteristics of the reservoir fluids containing polar components, which are essential for design, evaluation, and optimization of hybrid steam-solvent injection processes in heavy oil reservoirs.