Abstract: For more direct observation and comparison of the enhanced oil recovery mechanism with different displacement
ways by CO2，the high-pressure visualization micro model is adopted，which is similar to stratigraphic pore structure to perform
four groups of experiment of water flooding，miscible displacement，nearly immiscible displacement and immiscible
displacement by CO2 in this paper. Based on the color image processing technology and binary image two-value method，the
different displacement front，oil-gas interface，oil-gas distribution characteristics，oil area in model and oil color change of
the different displacement way are studied and contrasted. The research shows that most water displaces oil with unpistol-like
flow during water displacement and oil-gas interface is of convex curve；in CO2 immiscible displacement，there are obvious
gas-liquid two-phase flow between them，the shape of the gas-liquid interface is sharp and the streaming and mixed phase flow
of gas-liquid is more serious and the gas breaks through early；In CO2 nearly immiscible displacement，the oil-gas interface is
dim，gas-liquid diphase region is not obvious and no obvious gas-liquid transition zone is formed. While in the process of CO2
miscible displacement，a distinct gas-liquid transition zone is formed and oil-gas interface is obviously sleek and fuzzy. And，
under the same condition，the CO2 miscible displacement lasts longer than others during the whole displacement process. This
study is of great significance for understanding oil displacement with CO2 and its mechanism.

Key words: words：experiment, binarization