Optimization Research Of Engineering Parameters For CO₂ Flooding On Low Permeability Reservoir During High Water Cut Stage

Xinli oil filed is one of the typical low permeability reservoir,and the target block to be studied chose water flooding in the earlier stage,which caused high composite water cut,severe interlayer problems and low oil recovery finally.Results from long-term research at home and abroad show that CO₂ flooding has a noticeable effect on increasing utilization degree and oil recovery of low permeability reservoir.Taking the target block of Xinli oil filed as research object,this paper analyzes reservoir geologic characteristic and exploiting dynamic feature,and acquires reservoir nature and fluid parameters.Through lab experiments,we study composition and PVT properties of the reservoir fluid,acquire MMP of formation crude by slim tube test and perform CO₂ flooding experiments under different injection methods and different water cut.Based on the analysis and test results,we establish CO₂ flooding compositional model to study the engineering parameters'optimization for CO₂ continuous flooding,intermittent CO₂ flooding and CO₂ WAG flooding,from which we obtain the best development method and its optimum flooding parameters.Finally,we determine the CO₂flooding development plan and conduct potential evaluationResults from above study reveal that the process of CO₂ flooding in the target block belongs to immiscible displacement.And research on the development effect of CO₂flooding after water driving for low permeability reservoir shows that when water cut is at intermediate degree,meaning water cut lies in 30%⁴0%,recovery is the highest for CO₂ flooding.Furthermore,CO₂ WAG flooding is the optimal way for the block,which could combine the microscopic oil displacement efficiency of CO₂ and the macroscopic sweep capacity of water,so it creates the highest recovery and conversion rate.