Characteristics of viscous fingering and influencing factors under the conditions of non-piston displacement

A mathematical model of oil displacement under the condition of low pressure gradient has been established and solved. Reservoir saturations are compared for the circumstances of fingering and non-fingering. The effects of displacing fluid viscosity and crude oil viscosity on viscous fingering are specially analyzed. The relationship between CO2 flooding mechanism and fingering is discussed. The result shows that the higher the viscosity of displacing fluid is,the smaller the fingering is; and the higher the oil viscosity is,the larger the fingering is. CO2 can effectively mitigate fingering under high pressure.