| Crude oil plays a highly important role in meeting the world’s energy demand,and such demand will be rapidly increased in next few years.High-temperature and high-salt oil reservoirs are widely distributed in our country,accounting for a large proportion.Therefore,efficient exploitation of high-temperature high-salt oil reservoirs are of great significance.In a typical high-temperature and high-salt G114 reservoir in an oilfield in eastern China,the average temperature is 105 °C,and the salinity is as high as 25963mg/L.The divalent cation content is 121-443 mg/L,and the oil-water mobility ratio is too small.In addition,the long-term water injection during the oil displacement process leads to the development of dominant channels,strong reservoir heterogeneity,small water flooding swept volume,high water content of produced fluid,and low oil displacement efficiency.The application of conventional chemical flooding is limited.In this paper,a poly-tablet binary oil flooding system suitable for G114 reservoir was developed.The experimental study showed that the optimal DP-2 polymer showed good compatibility with GC surfactants,which is suitable for G114 reservoir.Under the conditions of high temperature and high salt,the system can reduce the oil-water interfacial tension to an ultra-low value,and can also effectively increase the viscosity of the displacement fluid.At the same time,the oil displacement system also showed good shear resistance,anti-adsorption performance,long-term stability,emulsifying performance,etc.under harsh reservoir conditions.Therefore,this polymer-surfactant was identified for the enhanced oil recovery system of the G114 reservoir.Experimental studies have shown that the poly-surface binary system has good conductivity and can effectively migrate to the depths of the reservoir to capture the remaining oil in the reservoir.By combination of the economy and oil displacement effect,a 0.3% and 2000mg/L concentrations of surfactant and polymer with an injection rate of 0.6 PV is the best injection method,giving an enhanced oil recovery of 28.88%.In the three-dimensional model flooding experiment that close to the field,the enhanced oil recovery is ca.30%.Finally,the experimental study shows that the profile control in the early stage and combination of polymer concentration can effectively expand the swept volume and make the oil displacement performance better.The results in this study provide a reference for the field application of the poly-table binary system in high temperature and high salinity reservoirs. |
