Synthesis And Performance Evaluation Of Supercritical Carbon Dioxide Green Thickener

Petroleum is one of the most important modern industrial raw materials.It can be used not only as fuel for direct combustion,but also as an important chemical raw material.It can be used not only for civil use,but also as an important strategic material for national defense.Most of the domestic medium and high permeability old oilfields have entered the stage of high water cut and high recovery degree.The low permeability oilfields are facing the situation of low calibrated recovery factor and poor development effect of conventional water drive,so they have entered the application period of EOR technology.CO₂flooding is one of the main EOR technologies.However,under reservoir conditions,the viscosity of CO₂is much lower than that of crude oil.During oil displacement,the oil-gas mobility ratio is large,and the phenomenon of"viscous fingering"and gas channeling are easy to occur,which restricts the effect of CO₂in improving crude oil recovery.Considering environmental protection and cost factors,a CO₂thickener containing oxygen hydrocarbons was prepared by bulk free radical polymerization of maleate,which has the characteristics of small molecular weight,fluorine-free and silicon-free.CO₂thickeners with different molecular weights were prepared by adjusting the reaction conditions.The molecular structure and molecular weight of the polymers were characterized by ¹H NMR and gel liquid chromatography.The solubility and thickening performance of CO₂thickener in supercritical CO₂are experimentally studied.The dissolution and thickening effect of thickener are affected by molecular weight,thickener concentration,temperature and pressure.The maximum dissolved mass fraction can reach 10%,and the maximum thickening of supercritical CO₂can be 4.3 times.The indoor long core oil displacement experiment was carried out to study the oil displacement effect of thickened CO₂.Experiments show that the thickener can effectively improve the viscosity of CO₂.The thickened CO₂can improve the oil recovery by 20%on the basis of immiscible flooding in low permeability cores and 6%on the basis of miscible flooding.It can effectively weaken the"viscous fingering"and gas channeling,delay the gas breakthrough time in the process of oil displacement,greatly reduce the gas oil ratio and improve oil recovery.