Application of predicted bubble-rising velocities for estimating the minimum miscibility pressures of the light crude oil-CO_2 systems with the rising bubble apparatus

摘要

In this paper, an empirical correlation is modified and applied to predict the CO2 bubble-rising velocity (BRV) in the light crude oil. On a basis of the predicted BRVs, the minimum miscibility pressures (MMPs) of three light crude oil-CO2 systems are estimated by using the BRV criterion with the rising-bubble apparatus (RBA). First, a correction term of s.(2P/rho L)(0.5) is added into the BRV correlation in order to reflect the velocity of falling liquid film in velocity field by applying the Bernoulli's theorem. The modified correlation is tuned to match the BRVs of the dead light oil-pure and impure CO2 systems from the literature and two respective numerical coefficients s of -0.00046 and -0.00028 are determined by using the non-linear least-square method. It is found that the BRV is positive proportionally increased with the bubble diameter, interfacial tension, and density difference. Second, the predicted BRVs are used to estimate the MMPs by using the BRV criterion. Two respective MMPs of the dead light oil-pure and impure CO2 systems are found to be 12.4 MPa and 23.7 MPa at T-res = 53.0 degrees C, which agree well with 12.4-12.9 MPa from the coreflood tests and 23.4 MPa from the RBA tests or 23.4-23.5 MPa from the vanishing interfacial tension (VIT) technique. In addition, a live light oil-pure CO2 system is added to validate the modified BRV correlation. By means of the predicted BRVs, the MMP of the live oil-pure CO2 system is estimated to be 15.5 MPa, which matches well with 15.2-15.4 MPa from the slim-tube tests. The modified empirical correlation can improve the efficiency and capability of the BRV criterion.