Parametric Study of the Cyclic CO₂ Injection Process in Light Oil Systems

Abstract

Performance of cyclic CO 2 injection as an enhanced oil recovery (EOR) technique in a light crude oil system was experimentally investigated. Series of cyclic CO 2 injection tests were designed and carried out at various operating conditions. Effects of parameters including operating pressure (P op ), injection time (t inj ), soaking period (t soaking ) and connate water saturation (S wc ) were investigated on the oil recovery factor (RF) of cyclic injection tests. First, the CO 2 solubility in the crude oil sample and the oil swelling factor as a result of CO 2 dissolution into the oil phase for the crude oil−CO 2 system at temperatures T = 21 and 30 °C were determined. Second, the equilibrium interfacial tension of the crude oil−CO 2 system at T = 30 °C was measured. Afterward, the minimum miscibility pressure (MMP) between crude oil and CO 2 was calculated by means of the vanishing interfacial tension (VIT) technique and found to be MMP = 9.18 MPa. Finally, a total of 12 cyclic CO 2 injection tests were performed at operating pressures P op = 5.38, 6.55, and 8.27 MPa (i.e., immiscible to near-miscible conditions), and constant temperature T = 30 °C and in the presence and absence of connate water saturation. CO 2 injection time and soaking period were varied at each operating pressure in order to determine how these parameters might affect the performance of cyclic CO 2 injection. According to the obtained experimental results, it was found that the oil recovery factor of the cyclic CO 2 injection technique increases considerably with increased operating pressure (e.g., from RF = 32.6% at P op = 5.38 MPa to RF = 54.4% at P op = 8.27 MPa). The results also demonstrated that the oil recovery factor increases by a longer soaking period particularly if the cyclic CO 2 injection performed at lower operating pressures. Moreover, it was observed that the oil recovery factor is independent of CO 2 injection time. In addition, at each operating pressure, the oil recovery factor obtained in the presence of connate water saturation was found to be more than that when there was no connate water saturation in the system.

Determination of Minimum Miscibility Pressure of Crude Oil–CO2 System by Oil Swelling/Extraction Test

“…Various studies have suggested that low IFTs between the injected fluid and oil reservoir can improve sweep efficiencies and reduce residual oil saturation. [17][18][19] In CO 2 -based EOR techniques, at a spe- cific thermodynamic conditions (i.e., pressure, temperature, and composition), the IFT of the crude oil-CO 2 system decreases to a sufficiently low values which leads to a more favorable displacing process. In this study, the axisymmetric drop shape analysis (ADSA) technique for the pendant drop case was applied to determine the IFT between the crude oil and CO 2 .…”

Laboratory measurements of solubility and swelling factor for CO2/Brine and CO2/heavy oil binary systems under low‐medium pressure and temperature

“…[1] The performance of CO 2 -based EOR processes is mainly affected by the solubility of the CO 2 in the oil phase because it results in viscosity reduction and swelling. [1,2] CO 2 miscibility with oil can be achieved at a relatively high pressure and low temperature and only when the oil possesses a relatively high API gravity (higher than 36 8API). When injected at immiscible condition, the CO 2 enhances oil recovery through viscosity reduction, oil swelling, and solution gas drive mechanisms.…”

Experimental investigation on influencing factors of CO2huff and puff under fractured low‐permeability conditions

“…As a consequence, more oil can be produced and oil recovery can be enhanced by reducing oil viscosity, expanding oil volume, and extracting the light components of crude oil. [18][19][20][21][22][23] Mohammed-Singh et al 24 summarized the cases of CO 2 huff and puff in oil fields over the past two decades. Among above methods, CO 2 huff and puff has attracted more attention as an efficient and important technique.…”

“…[13][14][15][16][17] Both soaking time and CO 2 injection volume are important operation parameters to improve the performance of CO 2 huff and puff. [18][19][20][21][22][23] Mohammed-Singh et al 24 summarized the cases of CO 2 huff and puff in oil fields over the past two decades. They found that the best soaking time was 2-4 weeks and massive CO 2 injection enhanced the oil recovery of CO 2 huff and puff.…”