Experimental and theoretical quantification of phase behaviour for solvents/water/heavy oil systems with the PC-SAFT equation of state

Abstract

In this work, a new framework has been proposed to quantify phase behaviour of solvents-water-heavy oil systems based on the perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS) and then compared it with the cubic EOSs (e.g., PR EOS). Experimentally, constant composition expansion (CCE) tests were meticulously conducted to measure saturation pressure ($P_{sat}$), phase volume, and phase compositions for CO₂/heavy oil, N₂/heavy oil, and dimethyl ether (DME)/heavy oil systems with and without water at pressures up to 20 MPa and temperatures up to 433.2 K. Theoretically, a PC-SAFT EOS framework incorporated temperature-independent binary interaction parameters (BIPs) is employed to reproduce the measured $P_{sat}$ and other physical properties of the aforementioned systems. Addition of water into each of the aforementioned systems is found to increase its $P_{sat}$ compared to the systems without water. By characterizing heavy oil as four pseudocomponents, density of the aforementioned systems can be accurately predicted with the root-mean-squared relative error (RMSRE) of 1.84%. Then, the BIPs for each binary pair of the aforementioned systems are obtained by minimizing the deviation between the experimentally measured $P_{sat}$ and the corresponding calculated values. Compared with the modified PR EOS, the proposed framework shows its superior performance with an RMSRE of 2.93% for the predicted $P_{sat}$ of the aforementioned systems.