Measurement of minimum miscibility pressure of CO2 in Thai crude oil: effect of gas impurity

Abstract

A pressure decay technique was used to measure minimum miscibility pressure (MMP) of CO2-Thai crude system. Effects of temperature, oil molecular weight, and gas impurity in CO2 on MMP were determined by for condensate APIo 63.9, oil sample (condensate mixed with n-hexane by ratio 50:50), and n-decane. The sample was put into a Parr reactor that was pressurized by injecting CO2 gas at various pressures from 500 to 900 psi to obtain the pressure decay curves. MMP was determined by the total pressure drop curve, where the MMP was the maximum point of the pressure drop curve. For the effect of molecular weight, the MMP of condensate (Mw=113.64), oil sample (Mw=107.32), and n-decane (Mw=142.28) at 20 °C were 775, 725, and 825 psi, respectively. For the effect of temperature, the MMP of oil sample between 20°C and 30 °C were 725, and 800 psi, respectively. The effect of gas impurity (N2) on MMP was determined for the oil sample. The MMP of CO2 injection with 1% and 3% N2 at 20 °C were 750, and 850 psi, respectively.