Experimental study on asphaltene precipitation induced by CO2 flooding

Abstract

The effects of CO2 pressure, temperature and concentration on asphaltene precipitation induced by CO2 were studied using a high-pressure vessel, interfacial tensiometer, Fourier transform infrared (FTIR) and drill core displacement experimental apparatus. The results indicated that the content of asphaltene in crude oil decreased, and the interfacial tension between a model oil and distilled water increased, with an increase of CO2 pressure, decrease of temperature and increase of molar ratio of CO2 to crude oil when CO2 contacted crude oil in the high pressure vessel. The content of asphaltene in sweep-out oil and the permeability of test cores both also decreased with an increase of CO2 flooding pressure. The main reason for changes in content of asphaltene in crude oil, in interfacial tension between model oil and distilled water and in the permeability of the test core is the precipitation of asphaltene which is an interfacially active substance in crude oil. Precipitation of asphaltene also blocks pores in the drill core which decreases the permeability.