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Petroleum Origin and Generation
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Condensate hydrocarbons are bigger molecules (C5 plus) than the gaseous (C1–C4) hydrocarbons. Condensate liquid occurs in association with gases (C1–C4) in a reservoir. Under pressure the liquid is in a dissolved state in gas. At the surface, condensate liquid and gases are separated. Condensate hydrocarbons are formed at greater depths and temperatures. Condensate is a product in between oil and gas on a molecular weight basis. Condensate/gases are produced by the cracking of oil within a reservoir, not through the cracking of kerogen. Conversion of vapor into liquid is condensation process. Retrograde condensation occur due to reduction of pressure in reservoir condition.
Mixture Behavior, Stability, and Azeotropy
Published in Juan H. Vera, Grazyna Wilczek-Vera, Classical Thermodynamics of Fluid Systems, 2016
Juan H. Vera, Grazyna Wilczek-Vera
As can be seen in Figures 17.5 and 17.6, the relative amounts of phases L and V are inversely proportional to the segments of the tie line joining the point at the mixture composition z1 with the corresponding equilibrium compositions x1α and y1β. This is the so-called lever rule. If the temperature of the mixture is increased at a constant pressure P, as shown in Figure 17.6, the liquid will start boiling at point b and the boiling point will continually increase until point d is reached. Both the relative amounts of the two phases and their composition will continuously change until all the mixture is in the vapor phase. When the temperature of the system is higher than the critical temperature of one of the compounds, that particular compound is in “supercritical condition.” In this case, as depicted in Figure 17.7, the bubble curve will not reach the pure compound 1 axis. One interesting effect observed in this case is that decompression of a saturated vapor does not always produce a superheated gas. Figure 17.7 depicts the case of a mixture with a composition slightly to the right of critical point c, which is initially at a high pressure and being decompressed until a saturated vapor phase is reached. If the mixture is further decompressed, condensation occurs and a saturated liquid phase will coexist with the saturated vapor phase. Further decompression will cause the relative amount of liquid phase to increase at first, and decrease afterwards until a saturated vapor phase is reached again. Then the fluid passes to the superheated region. This unusual behavior is known as retrograde condensation.
Insights on equation of state modeling PVT experiments for deep volatile oil reservoir
Published in Petroleum Science and Technology, 2023
Jing Zhang, Jing Xia, Jun Qin, Zhongchen Ba, Haining Zhao, Haonan Wu, Chaojie Di, Huijin Chen, Xiaoxi Lin
Figure 10 shows that the PR-EOS modeling results of this study are similar to those obtained from the PVTsim software, which also uses the characterized fluid in Table A2 for calculation. For gas condensate system, the liquid phase saturation gradually increases then decreases as pressure depletion, which is known as the retrograde condensation phenomenon. There is no retrograde condensation phenomenon for volatile oil sample (Figure 10a). Figure 10(b) shows the percentage of the accumulated gas production in total amount of reservoir fluids during the CVD test. The accumulated gas production is monotonically increasing with pressure depletion. Figure 10(c) shows the difference between the gas phase and the two-phase deviation factor in the CVD test. The gas-phase deviation factor basically remains unchanged with pressure variation, while the two phase deviation factor significantly decreases with pressure depletion. Figure 10(d) shows the variation of equilibrium gas and liquid densities in the CVD test.
New calculation method for condensate oil saturation of gas condensate reservoir
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Angang Zhang, Zifei Fan, Lun Zhao, Congge He
During the development of cyclic gas injection in the gas condensate reservoir with bottom water, as the formation pressure decreases, the retrograde condensation phenomenon occurs inside the reservoir. The connate water in the formation will gradually evaporate and be mixed into the condensate gas. The rock compressibility will also change greatly, and the bottom or edge water will also invade the gas reservoir due to the pressure difference (Wu, Li, and Fan et al. 2013; Zhao, Bian, and Fan et al. 2011; Li et al. 2010; Qi, Tang, and Du 2003; Liu, Liu, and Tian 2011).