Enhanced Swelling Effect and Viscosity Reduction of Solvent(s)/CO2/Heavy-Oil Systems

Abstract

Summary In this paper, techniques have been developed to examine the enhanced swelling effect and viscosity reduction of CO2-saturated heavy oil with the addition of either solvent C3H8 or solvent n-C4H10. Experimentally, pressure/volume/temperature (PVT) tests are conducted to measure the saturation pressure, swelling factor, and viscosity of the C3H8/heavy-oil system, the C3H8/CO2/heavy-oil system, and the n-C4H10/CO2/heavy-oil system, respectively, in the overall temperature range of 280.45 to 391.55 K. It has been found that an increased swelling effect of heavy oil is obtained by adding the gas solvent C3H8 or n-C4H10 into the CO2 stream. An enhanced viscosity reduction of the CO2/heavy-oil system is also achieved in the presence of either C3H8 or n-C4H10. The enhanced swelling effect and viscosity reduction caused by adding either C3H8 or n-C4H10 into the CO2 stream are particularly favorable for achieving a higher heavy-oil recovery compared with pure-CO2 processes. Theoretically, three binary-interaction-parameter (BIP) correlations in the Peng-Robinson (PR) equation of state (EOS) (PR-EOS) method have been proposed for respectively characterizing CO2/heavy-oil binaries, C3H8/heavy-oil binaries, and n-C4H10/heavy-oil binaries by treating each oil sample as a single pseudocomponent with its molecular weight (MW) and specific gravity (SG). The BIP correlations (together with the PR-EOS) can be used to predict the saturation pressures and swelling factors of the C3H8/CO2/heavy-oil system and the n-C4H10/CO2/heavy-oil system with a generally good accuracy.

Interfacial tension of CO2 and crude oils under high pressure and temperature

“…The oil viscosity reduction, oil swelling effect and miscibility between CO 2 and crude oil are considered main contributions for CO 2 -EOR [8,9]. Oil mobility can be improved because of CO 2 dissolving in crude oil which causes oil viscosity to be reduced and the oil volume expanded [10].…”

Direct perturbation of the Peng–Robinson attraction and covolume parameters for reservoir fluid characterization

“…Data and predictions for the gas-oil-ratios (GOR) for heavy oil 3 (Pedersen et al, 2004) at the reservoir temperature of 305.45 K. The AAD of the GOR predictions is 2.9% with the direct PnA method. Table 5), Feeds #4 and #5 in Li et al (2013a). The AAD of the saturation pressure predictions is 13.7% for Feed #4 and 6.0% for Feed #5.…”

“…For heavy oil 4, the regression in the direct PnA method used the P SAT of 56.64 bar at 347.67 K for the live oil reported (Feed #5 in Li et al, 2013a). Density data for this live oil were unavailable, and, therefore, generated on the basis of the EOS model given by Li et al (2013a).…”

“…Density data for this live oil were unavailable, and, therefore, generated on the basis of the EOS model given by Li et al (2013a). Fig.…”

Experimental and Theoretical Determination of Equilibrium Interfacial Tension for the Solvent(s)–CO2–Heavy Oil Systems

“…It should be noted that the density of the heavy oil and the density of the bulk gas phase are required inputs for implementing the ADSA program. In this study, the density of Lloydminster heavy oil at any temperature and pressure can be calculated using the heavy oil density correlation presented elsewhere, 22 while the density of the bulk solvent phase is calculated with the PR EOS. Thereafter, the ADSA program for the pendent drop case is executed to determine both the dynamic and equilibrium IFTs by solving the Laplace equation of capillarity.…”