Abstract
A factor influencing the effectiveness of CO2 injection is miscibility. Besides the miscible injection, CO2 may also contribute to oil recovery improvement by immiscible injection through modifying several properties such as oil swelling, viscosity reduction, and the lowering of interfacial tension (IFT). Moreover, CO2 immiscible injection performance is also expected to be improved by adding some solvent. However, there are a lack of studies identifying the roles of solvent in assisting CO2 injection through observing those properties simultaneously. This paper explains the effects of CO2–carbonyl and CO2–hydroxyl compounds mixture injection on those properties, and also the minimum miscibility pressure (MMP) experimentally by using VIPS (refers to viscosity, interfacial tension, pressure–volume, and swelling) apparatus, which has a capability of measuring those properties simultaneously within a closed system. Higher swelling factor, lower viscosity, IFT and MMP are observed from a CO2–propanone/acetone mixture injection. The role of propanone and ethanol is more significant in Sample A1, which has higher molecular weight (MW) of C7+ and lower composition of C1–C4, than that in the other Sample A9. The solvents accelerate the ways in which CO2 dissolves and extracts oil, especially the extraction of the heavier component left in the swelling cell.
Highlights
The development of an oil field can be carried out in up to three stages: primary, secondary, and tertiary recovery
The results clearly demonstrate the similarity of how propanone and ethanol work in both samples; they increase the swelling factor more than that of CO2 injection without any solvent addition
Based on our experiment using the novel apparatus of VIPS that was able to acquire the swelling factor, viscosity and interfacial tension (IFT) simultaneously, the following conclusions may be drawn: 1
Summary
The development of an oil field can be carried out in up to three stages: primary, secondary, and tertiary recovery. The identification of a miscibility condition between the injected gas and the oil is important for oil recovery in EOR. Miscibility is defined as a physical condition between two or more liquids that allows mixing in all proportions in the absence of an interface contact. Higher oil recovery from reservoirs can be achieved by CO2 displacement if the injection pressure is greater than a certain minimum pressure. This minimum pressure is defined as the CO2 minimum miscibility pressure, hereafter abbreviated as MMP [3]. The MMP will determine whether the CO2 gas injection is a miscible or an immiscible process
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