An Experimental Study On The Efficiency Of CO₂ Flooding In Deep And High Volatile Oil Reservoirs

Using conventional water injection technology cannot improve effectively the recovery of deep low permeability reservoir.According to this kind of problem,domestic and foreign experts and scholars put forward by using injection gas to improve oil recovery,in which CO₂flooding is more and more used method at present.This way can effectively improve oil recovery of the low permeability reservoir.CO₂ is a low viscosity and high efficiency oil displacement agent,which can be effective for replenishing the formation energy and improve the injectivity of injection agent and oil displacement efficiency and therefor it is the effective ways to improve the recovery degree of deep low permeability reservoirs.In addition,the international community generally concerned about the problem of greenhouse gas emissions control.By using carbon dioxide as oil displacement agent,which can be not only can improve the oil recovery,but also has an important significance for reducing the greenhouse effect and environmental protection.In this paper,the research content is from scientific research project of ZhongYuan oilfield.Taking Hu 96 block for research objects,this paper thoroughly studied both the minimum miscibility pressure（MMP）and CO₂ flooding long core displacement experiments.Based on the test the changes of the components of the gas produced was studied to determine the efficiency of CO₂ flooding in different stages of development.The main work includes swelling test by CO₂ injection,and the slim test in different development stages,and long core displacement test.The basic parameters of the crude oil were measured by PVT test,and the characteristics of crude oil with different percentage of CO₂ were measured by swelling test.By slim-tube test,different MMP was tested under the pressure with different development stage.The research results show that with the decline in crude oil saturation pressure,the difference between the MMP and saturation pressure into a rising trend.CO₂ flooding efficiency was studied with the pressure depletion by long core physical simulation experiment,and the components of the gas produced was studied.The experimental results show that on the CO₂flooding efficiency can reach 80%under Hu 96 block formation pressure,however,the recovery degree can reach 96.57%by CO₂ flooding after building up the pressure with CO₂.