Effect of pressure, temperature, and mass fraction of CO2 on the stability of the asphaltene constituents in crude oil

Abstract

ABSTRACTThis paper focus on the main influence factors (temperature, pressure, and mass fraction of CO2) on the state of asphaltene in the crude oil during CO2 flooding by using high temperature and high pressure microanalysis system of solid precipitation. For the simulated oil sample – CO2 system, the state of asphaltene is not affected by temperature within this range of 50°C to 100°C, the particle size of the asphaltene has an increase with the increase of the pressure from 8MPa to 40 MPa. When the mass fraction of CO2 is less than 35%, the state of the asphaltene has not changed and the asphaltene particles are in a suspension state. When the mass fraction of CO2 increases to 40%, the aggregation of the asphaltenes occurs and then form precipitation. With the further increase of the mass fraction of CO2, the particle of the asphaltene aggregates has a significant increase. For the field development project design of CO2 flooding, the influence of the temperature can be ignored, the appropriate mass fraction of CO2 is below 35% and the gas injection pressure should maintain a relatively low value. The results can provide a theoretical basis to avoid the asphaltene precipitation during CO2 flooding.