Quantification of Phase Behavior for Solvent/Heavy-Oil/Water Systems at High Pressures and Elevated Temperatures with Dynamic Volume Analysis

Summary Accurate quantification of phase behavior of solvent/heavy-oil/bitumen/water systems at high pressures and elevated temperatures is of high significance for the design of vapor extraction, cyclic solvent injection, expanding-solvent steam-assisted gravity drainage (ES-SAGD), and hot-solvent injection processes. The relevant experimental data and theoretical analyses are still insufficient for achieving a reliable model. This is especially true when the system temperatures approach or exceed the critical temperatures of the solvents used (i.e., when the solvent density is large enough). This study provides new experimental measurements of the phase behavior of propane (C3H8)/carbon dioxide (CO2)/heavy-oil/water systems at pressures up to 20 MPa and temperatures up to 432.3 K. More specifically, four feeds of C3H8/CO2/heavy-oil/water systems are used to conduct constant composition expansion (CCE) tests, during which the heights of the entire fluid system (i.e., total volume) and each phase are recorded at each pressure and temperature, respectively. Theoretically, a dynamic volume analysis (DVA) of the measured data is proposed for the first time to quantify each phase, provided that the assumption for vapor phase is valid and that the vapor and oleic phase densities can be accurately calculated. By tuning the binary interaction parameter (BIP) for solvent/heavy-oil pairs (denoted as BIPS−HO) to match the total volume, the height of the vapor/oleic (V/L) interface can be matched as well. By using the tuned BIPS−HO, the total volume and height of the V/L interface of C3H8/CO2/heavy-oil/water systems can be accurately predicted, no matter whether the solvent solubility in water is low (i.e., C3H8) or high (i.e., CO2). This DVA can be used to determine/evaluate the solvent solubility, saturation pressure/phase boundary, and phase volume/density accurately in a large temperature and pressure range. The newly proposed DVA method is also used to reproduce the experimental measurements collected from the literature, including phase-volume fractions, solvent solubility, and saturation pressure. In addition, the DVA method can serve as a tool to check whether the experimental measurements are reliable or not.

Download Full-text

Determination of Individual Diffusion Coefficients of C3H8–n-C4H10-CO2-Heavy Oil Systems at High Pressures and Elevated Temperatures by Dynamic Volume Analysis (DVA)

10.2118/179618-ms ◽

2016 ◽

Cited By ~ 1

Author(s):

Sixu Zheng ◽

Daoyong Yang

Keyword(s):

Heavy Oil ◽

Diffusion Coefficients ◽

High Pressures ◽

Elevated Temperatures ◽

Volume Analysis

Download Full-text

Determination of Individual Diffusion Coefficients of C3H8/n-C4H10/CO2/Heavy-Oil Systems at High Pressures and Elevated Temperatures by Dynamic Volume Analysis

SPE Journal ◽

10.2118/179618-pa ◽

2016 ◽

Vol 22 (03) ◽

pp. 799-816 ◽

Cited By ~ 17

Author(s):

Sixu Zheng ◽

Daoyong Yang

Keyword(s):

Mass Transfer ◽

Heat And Mass Transfer ◽

Volume Change ◽

Heavy Oil ◽

Diffusion Coefficients ◽

High Pressures ◽

Elevated Temperatures ◽

Transfer Model ◽

Volume Analysis ◽

Alkane Solvents

Summary By coupling heat and mass transfer for C3H8/n-C4H10/CO2/heavy-oil systems as well as by treating heavy oil as multiple pseudocomponents, a new technique together with its computational scheme has been developed to determine individual diffusion coefficients of alkane solvents and CO2 in heavy oil at high pressures and elevated temperatures by dynamic volume analysis (DVA). Experimentally, well-designed diffusion tests have been conducted for an n-C4H10/heavy-oil system, a CO2/heavy-oil system, an n-C4H10/CO2/heavy-oil system, and a C3H8/n-C4H10/CO2/heavy-oil system by using a visualized pressure/volume/temperature (PVT) setup. The volume change of liquid phase is monitored and recorded during the measurements, whereas the gas-chromatography (GC) method is used to determine the compositions of gas mixtures at the beginning and the end of the diffusion tests. Theoretically, the volume-translated Peng-Robinson (PR) equation of state (EOS) characterizing heavy oil as multiple pseudocomponents has been incorporated to develop a 2D heat-and-mass-transfer model for the aforementioned systems. The alternating-direction-implicit algorithm is applied to solve the 2D difference equations into which a moving gas/liquid interface has been successfully incorporated. The discrepancy between the measured and calculated dynamic-volume change and the discrepancy between the measured and calculated gas compositions at the end of diffusion tests have been minimized to determine the individual diffusion coefficients. Alkane solvents diffuse faster than CO2 in heavy oil, whereas addition of alkane solvent(s) into the CO2 stream not only enhances mass transfer, but also achieves an improved swelling effect of heavy oil. Among the four diffusion tests, the largest dynamic swelling factor at the end of the diffusion test is measured to be 1.118 for the C3H8/n-C4H10/CO2/heavy-oil system.

Download Full-text