Construction And Performance Of Supramolecular Oil Flooding Solution For Xinjiang M Oil Reservoir

In recent years,most of the old oilfields in China are faced with the problems such as high water cut and production decline,and the development situation is very serious.Chemical flooding can improve the oil recovery by improving the sweep efficiency and oil washing efficiency.The surfactant supramolecular system constructed by non-covalent bonds has higher viscosity at lower concentration.It can improve the sweep efficiency,reduce the interfacial tension and improve the oil washing efficiency of oil displacement agent in the process of oil displacement,which is a good oil displacement system.Zwitterionic surfactant and anionic surfactant were selected to construct supramolecular system.By comparing the compatibility,rheological properties and the ability to reduce the interfacial tension of different systems,the types of zwitterionic surfactant and anionic surfactant,as well as the mass ratio and concentration of the mixture were optimized.Then,the transmission electron microscopy,dynamic light scatteringand surface tension measurement were conducted to reveal the micro-thickening mechanism of the supramolecular system.Subsequently,the influence mechanism of p H,temperature and inorganic salts on the rheological property and the ability to reduce interfacial tension of the supramolecular flooding system were investigated.Finally,formation condition of Xinjiang M reservoir(43℃,salinity7877.69 mg·L^-1)were simulated to evaluate the oil displacement effect of the supramolecular oil displacement system.The static adsorption quantity and emulsification performance of the system were evaluated,and the microetching model was used to reveal the mechanism of EOR.The results show that erucyl dimethyl amidopropyl betaine（EDAB）and Sodium dodecyl sulfate（SDS）have better synergistic viscosity enhancement effect under the condition of 43℃and salinity 7877.69 mg·L^-1.When the mass ratio of EDAB and SDS is 1.5:1,the viscosity enhancement effect of the system is best（41.9 m Pa·s）,and the interfacial tension of oil-water could be ultra-low(8.66×10^-3 m N·m^-1).In EDAB/SDS system,SDS can reduce the electrostatic interaction between the molecular head groups of EDAB,and make the molecules distance closely.The tail chain of SDS and EDAB is intertwined by hydrophobic interaction to increase the hydrophobic volume of worm-like micelles,so as to achieve the viscosity enhancement effect.The viscosity of the EDAB/SDS system was first enhanced and then inhibited by p H,temperature and Na Cl concentration.The system has good temperature resistance and sodium salt resistance,which shows good viscosity and low interfacial tension.Under the simulated reservoir conditions,it is found that EDAB/SDS system can effectively reduce the remaining oil saturation.The oil recovery is improved 19%for heterogeneous cores,improved 22.56%for injection of 0.5 PV in homogeneous core.Moreover,the static sandstone adsorption quantity of the system is less(1.21 mg·g^-1),and the system has good emulsifying ability.By observation of microscopic oil displacement model,the EDAB/SDS system can effectively improve the recovery of crude oil by improving the sweep efficiency and oil washing efficiency.The supramolecular flooding system has a wide application prospects because of its low consumption and excellent performance.