Non-homogeneous Influence the Effect of CO2-N2 Compound Flooding in Ultra-low Permeability Reservoir

Abstract

Affected by reservoir rhythmicity, permeability contrast and length-thickness ratio, using carbon dioxide-nitrogen compound flooding in ultra-low permeability non-homogeneous reservoir will influence the oil recovery. Based on the experimental core model, a series of targeted models are established by changing the correlation parameter by numerical simulations. The results shows that, the higher heterogeneity, the lower oil recovery in reservoir, the less carbon dioxide injection should be needed to achieve the maximum recovery; because of the gravitational differentiation and fluid exchange between the oil layers, using carbon dioxide-nitrogen compound flooding in non-interbedded positive rhythm reservoir will have a better recovery than positive rhythm of interbedded reservoir, negative rhythm of interbedded reservoir and negative rhythm reservoir without interbed; when the permeability contrast is a constant, the larger length-thickness ratio, the later the gas breakthrough and the higher oil recovery.