Abstract
In this paper, there are nine oil samples to explore the characteristics of formation oil at different CO2 injection rate, and the characteristics include bubble point pressure, volume expansion coefficient, viscosity, density, and average molecular weight, composition of gas and liquid phase, and asphalt sediment. According to the experimental results of early nine oil samples of swelling tests, in high temperature and high pressure conditions, characteristics and changing rules of properties of formation oil, including bubble point pressure, volume expansion coefficient, viscosity, density, and average molecular weight, composition of gas and liquid phase, and asphalt sediment, were evaluated and analyzed at different CO2 injection rate systematically. The research not only can provide guides for petroleum engineers when they need to adjust the injection and production programs, but also can provide comparatively comprehensive experimental rules for researches on enhanced oil recovery (EOR) mechanisms of gas miscible and nonmiscible flooding. Moreover, phase parameters of different formation oil system can be extracted for reservoir numerical simulation.
Highlights
Research on the phase characteristics of CO2 and formation oil system is an indispensable access for to understand mechanisms of miscible-phase displacement
Xiangliang mainly analyzed the changes of viscosity and density in N2-oil system when studying the impacts of N2 on the phase characteristics of formation oil within the Niuzhuang reservoir, a fault block reservoir
In the study of phase characteristics of light oil containing dissolved CO2 under reservoir conditions, Li argued that CO2 can extract light hydrocarbon from crude oil while lower the ability of formation oil to dissolve wax, and oil producers need to be reinforced with paraffin control treatments in order to operate normally [6]
Summary
Research on the phase characteristics of CO2 and formation oil system is an indispensable access for to understand mechanisms of miscible-phase displacement. Xiangliang mainly analyzed the changes of viscosity and density in N2-oil system when studying the impacts of N2 on the phase characteristics of formation oil within the Niuzhuang reservoir, a fault block reservoir It found that elastic energy of the system is the main factor to influence the oil recovery of that reservoir [1]. Within CO2&heavy-oil Phase System that in the process of CO2 immiscible displacement, the viscosity of formation crude oil decreased by 30% and the volume expansion of heavy oil and dissolved gas flooding are the main factors to improve recovery. They presented a predictive equation for phase parameters to fit the CO2&heavy-oil system of Lick Creek reservoir [8]. Based on various phase characteristics in CO2-oil system, using different EOR methods and adjusting ways of injection and production can maintain oil recovery in a high level and provide guides for protecting injected gas from circulating in a low even noneffective way
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