Migration behavior of CO2-crude oil miscible zone

The CO2-crude oil miscible zone is the key factor to improve the recovery of miscible flooding, and the migration behavior of CO2-crude oil miscible zone has an significant influence on the development effect of CO2 miscible flooding. At present, the research on the characteristics of CO2-crude oil miscibility mainly focus on the miscible mechanism and the migration behavior of the miscible front edge, but there still remain many gaps in the systematic studies on the migration behavior of miscible zones. This paper defines four characteristic parameters of the miscible zone and presents the migration behavior of the miscible zone through theoretical analysis and numerical simulation. The results demonstrate that before the miscible zone's front edge breaks through, the front and rear edges' sweep coefficient and the dimensionless miscible zone's area increase linearly.Then, the dimensionless miscible zone's width decreases gradually after reaching the local maximum, while the front and rear edges' fingering coefficient increase more and more rapidly. After the miscible zone's rear edge breaks through, the miscible zone sweep coefficient's increase rate dropped significantly. The dimensionless miscible zone's area, the dimensionless miscible zone's width and the fingering coefficient gradually decrease and then stabilize. Based on the accurate characterization of miscible zone, it can provide a basis for the miscible zone regulation to improve the development effect of CO2 flooding.