| Chemical flooding especially surfactant flooding is one of the most widely used technologies which can enhance oil recovery( EOR). However, there are three main problems in the domestic surfactant flooding field: single agent becomes ineffective with the addition of alkali, mixed systems exist serious chromatographic separation and the oil displacement effectiveness is restricted in the oil reservoir with the characteristics of high temperature and high salinity. To solve those problems, some research work on non-alkali flooding mixed systems of surfactants was done in this dissertation. Gemini sulfonate surfactant and anionic/non-ionic surfactant acted as the main agent respectively in the mixed systems. The effect of different mixed-proportion, total concentration, salinity and hardness was also disscussed. The main contents and results were as follows:Reaserch and comparison were carried out on the surface(interface) chemical properties of the mixed systems of two-alkyl diphenylmethane disufosalt(DSDM) and five kinds of surfactants, which were widely used in EOR. And the results showed that di C12B/C14-DSDM and BS-16/C16-DSDM were the optimizing oil displacement agents. di C12 B was short for didodecylmethylcarboxyl betaine, BS-16 was the abbreviation of fatty alkyl dimethyl betaine. Surface chemical properties and interation parameters between surfactants molecules of the two mixed systems along with their different combinations had been investigated. The results indicated that the two mixed systems had good synergistic effect. The oil/water dynamic interfacial tension of the two mixed systems were measured without adding any alkaline agent at different mixed-proportion, total concentration, kinds of oil, temperature, the salinity and hardness. The results showed that the mixed systems could reduce interfacial tension of Shengli crude oil/water to ultralow(an order of 10-3 m N·m-1) under the conditions of the mole fraction of DSDM was more than 50 %, the total surfactant concentration was 0.05~0.2 wt.%, the hardness was 50~200 mg·L-1, the salinity was 4000~10000 mg·L-1 and the tempreture was 70 oC. The results demonstrated that di C12B/C14-DSDM and BS-16/C16-DSDM systems were suitable for oil reservoir of high temperature and high salinity, and the chromatographic separation phenomenon had less effect on the systems.A series of fatty alcohol polyoxyethylene ether(AEO), were used as raw materials, which were transformed to corresponding fatty alcohol polyoxyethylene ether caoboxylates(AEC) by reaction with sodium chloroacetate(Cl CH2COONa) in the presence of Na OH. The optimum synthesis condition which was explored by orthogonal experiment was as follows: n(AEC) : n(Na OH) : n(Cl CH2COONa) = 1.0:1.5:1.1, reacted for 8 h at 75 oC, and the conversion of AEO was 83.56 %. Physicochemical properties and surface chemical properties of a series of AEC were studed, hydrophilicity and the ability to reduce the surface(interface) tension of them were also analysed. BS-68/C16/18AEC3 and BS-18/C16/18AEC3 mixed systems had been filtered as the best displacement agents based on the interfacial tension of the mixtures of AEC and fatty alkyl dimethyl betaine(BS-16, BS-68 and BS-18). Oil displacement agent formula was further studied systematically. The results revealed that Shengli crude oil/water interface tension could be reduced to 10-3 m N·m-1 in the two systems with the addition of a small amount of AEC in a wide total surfactant concentration range. BS-68/C16/18AEC3 mixed system could be used in petroleum reservoir with salinity concentration that was less than 30000 mg·L-1, and BS-18/C16/18AEC3 system could be used in petroleum reservoir with salinity concentration that was less than 50000 mg·L-1. |
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