Measurement of minimum miscibility pressure of carbon dioxide in Thai crude oil

Abstract

The minimum miscibility pressure (MMP) between CO2 and petroleum crude was measured using a Parr reactor and the pressure decay technique. The effects of oil molecular weight and temperature on MMP were carried out using crude oil API of 62.1, n-pentane, and n-heptane. All samples were tested at 30 ℃, and crude oil and n-heptane additionally tested at 40 ℃. n-Decane used as an oil reference was measured at 20 ℃. The oil sample in the Parr reactor was pressurized by injecting CO2 gas at various pressures (400 to 950 psi), to obtain pressure decay curves. The MMP determined from the pressure drop curve, the point just before the total pressure drop started to decrease at 30 ℃ were 890, 680, and 785 psi for crude oil, n-pentane, and n-heptane, respectively. At 40 ℃, the MMP of n-heptane was 880 psi, while the MMP of crude oil was beyond 950 psi. The MMP of n-decane reference at 20 ℃ was 820 psi which was very similar to literature. In addition, the increase in oil molecular weight increased the MMP of the system as did the temperature. The MMP of crude oil API 62.1, n-pentane, and n-heptane at 30 ℃ were calculated using Li et al. correlation and compared the results. The percentage absolute error (%AD) of crude oil API 62.1, n-pentane, n-heptane at 30 ℃ were 1.35%, 5.88%, 4.84%, respectively while that of n-heptane at 40 ℃ was 6.02%. The pressure decay technique can be applicable to determine the MMP of Thai crude oil.