| Surfactant flooding is a significant means of tertiary oil recovery in the petroleum industry,which a large number of the scholar has been studying it for several years.As the development of Ansai Oilfield enters a period of medial to high water cuts,the problems exposed by conventional surfactants in mine applications gradually cannot be solved.To overcome the problems of salt tolerance or residence to temperature differences of conventional oil field surfactants,and better adapt to the complex conditions of low permeability reservoirs,Sodium N,N-dialkyl ethylenediamine diphenoxylate,a carboxylic Gemini surfactant,was synthesized.N,N-dialkyl ethylenediamine sodium dibenzoate was combined by using phthalic anhydride,ethylenediamine,and Bromo-n-octane as raw materials,and synthesized through two steps of amidation reaction and N-alkylation reaction.Meanwhile,through a single factor experiment and orthogonal experiment,the synthesis conditions of each step were optimized,and finally,the best synthesis scheme was determined.The amidation reaction of the generated intermediate is fed with ethylenediamine and phthalic anhydride at 1:2.5,the reaction temperature is 65°C,while the reaction time is 18h;the feed ratio of the N-alkylation reaction to the target product is1:2.5,The reaction temperature is 60?,the reaction time is 8h,the final product yield can reach 45.7%.After the synthesis of the product under the optimal reaction conditions in the laboratory synthesis experiment,the interface capability was investigated and the synthesis product was determined as the main agent of the compound surfactant.After studying the compounding mechanism,the optimal compounding flooding system suitable for Ansai Oilfield is determined as follows:the main agent concentration is 0.2%,using newly synthesized carboxylic acid gemini surfactant and non-ionic surfactant OP-10 to the mass ratio of 1:2 is used to form the oil displacement system,which can reduce the oil-water interfacial tension to8.76×10-3mN/m.Besides,the system has good performance at the reservoir temperature and salinity of Ansai Oilfield.Indoor oil displacement experiments show that the system can improve the crude oil recovery rate by 7.92%.According to the conclusion of the laboratory experiment,the field pilot test in Wangyao Block of Ansai Oilfield was carried out.The measures resulted in an average daily oil increase of 1.4t and a comprehensive water cut of 8.6%.It shows that the system has an impressive effect on improving the recovery factor,which provides a theoretical and practical basis for the future innovation and promotion of this technology. |
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