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Millimeter to nanometer-scale tight oil–CO2 solubility parameter and minimum miscibility pressure calculations

Zhang, Kaiqiang, Jia, Na, Li, Songyan and Liu, Lirong (2018) Millimeter to nanometer-scale tight oil–CO2 solubility parameter and minimum miscibility pressure calculations Fuel, 220. pp. 645-653.

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In this paper, solubility parameters and minimum miscibility pressures (MMPs) of five tight oil–CO2 systems are calculated in millimeter to nanometer scales. First, the Peng–Robinson equation of state (PR-EOS) is modified to calculate the vapour–liquid equilibrium in nanopores by considering the effects of capillary pressure and shifts of critical temperature and pressure. Second, a thermodynamic formula of the solubility parameter is derived and presented from the modified PR-EOS, which is applied to calculate the solubility parameters in nanopores. Third, the MMPs are estimated from the newly-developed solubility parameter-based method, at which the difference between the solubility parameters of oil and gas phases approximately equals to . The modified PR-EOS is found to be accurate for predicting the oil–CO2 phase behaviour. It is found that are almost equivalent at low pressures but with the pressure increase, at a larger pore radius becomes greater. The estimated MMPs are found to agree well with the measured MMPs from the coreflood and slim-tube tests in bulk phase and with the determined MMPs from the diminishing interface method in nanopores, whose average absolute relative deviations (AARD) are within 4.38% except for two abnormal cases. A smaller nanopore is found to contribute to the oil–gas solubility (i.e., a lower ) and the MMP is also decreased with the pore radius. Moreover, the temperature increase and addition of CH4 into the oil and gas phases lead to a larger , which make the oil and gas phases become more difficult to be soluble so that the corresponding MMPs increase. On the contrary, the oil–gas solubility is beneficial from the addition of C2H6 into gas phase so that the MMP is reduced. Overall, the effects of temperature, initial oil and injection gas compositions on the MMP are found to be weakened in nanopores.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Civil and Environmental Engineering
Authors :
Zhang, Kaiqiang
Jia, Na
Li, Songyan
Date : 22 February 2018
Funders : Petroleum Systems Engineering at the University of Regina, Petroleum Technology Research Centre (PTRC), Mitacs Canada
DOI : 10.1016/j.fuel.2018.02.032
Copyright Disclaimer : © 2018 Elsevier Ltd. All rights reserved.
Uncontrolled Keywords : Solubility parameter; Minimum miscibility pressure; Nanopores; Equation of state; Tight oil–CO2 systems;
Additional Information : Embargo OK Metadata OK No Further Action
Depositing User : James Marshall
Date Deposited : 23 Jul 2020 10:22
Last Modified : 23 Jul 2020 10:22

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