Study on Gas Miscible Displacement in Ultra-low Permeability Reservoirs

For late stage reservoirs with high water cut,the reservoirs with strong water sensitivity and the reservoirs with low permeability,it is one of the important ways for gas flooding to improve oil recovery.Considering good results of previous miscible displacements,three kind of long core tests are designed.The effects and mechanisms of different displacements on enhancing oil recovery are analyzed in this paper.Results show that final oil recovery of continuous gas flooding,gas flooding after water flooding and WAG are 66.7% 、65.8%和 58.7% differently in miscible pressure,and that of continuous gas flooding even reach 58.2% in 20MPa which is immiscible pressure.This paper draws a conclusion that it is feasible for Yushulin reservoir in the city of Daqing to use gas flooding to improve oil recovery in the theory.