Cationic Gemini Surfactants In Eor Field Of Applied Basic Research

Compared with conventional surfactants, Gemini surfactants exhibit lower cmc value and higher surface activity, which make them superior to the sole surfactant employed in EOR area at present. Owing to the superiorities Gemini surfactants have mentioned above, which could be introduced into EOR area. In this dissertation, a series of research on Gemini surfactants were carried out, so as to solve the problems conventional surfactants confronted at present, and at the same time, which would provide the technical and theoretical support on the applied research of Gemini surfactants in oil field.The synthesis and characterization results of cationic Gemini surfactants indicated that, first, there exists quaternary ammonium structure in the molecules of sample synthesized in lab by 红外光谱法 method, second, NMR method verified the existence of Gemini structure in the molecules of sample synthesized in lab, last, through the two methods mentioned above, the samples synthesized are sure to be object product, that is, cationic Gemini surfactants.The investigation results of cationic Gemini surfactant solution reducing oil/water interfacial tension indicated that this sort of surfactants have high interfacial activity, and at low concentration and no alkaline added, Gemini surfactants could reduce water and oil interfacial tension even to super-low level, that is 10~-3mN/m order of magnitude, and with the increase of heavy components of oil, Gemini surfactants reduce O/W IFT easier, and the results also indicated that during the course of Geminis reducing O/W IFT , there exists the match between Gemini molecule structure and the components of oil. The results would provide probability on employing Gemini surfactants into compound flooding with no alkaline, which will make it possible to employ Gemini surfactants to reduce oil/water IFT during the course of oil exploitation.The research was carried out on synergetic effect of cationic Gemini surfactants and conventional surfactants mixture reducing oil and water interfacial tension by use of Uniform Design, and the results indicated that there exhibited obvious synergetic effect for non-ion conventional surfactant, OP-10, and Gemini surfactant, GS14-2-14, during the course of mixture reducing oil /water IFT, and Uniform Design method can be used in the area of chemical flooding and compound chemical flooding. And the investigation results in this part can guide for making use of the synergetic effect resulted from Gemini surfactants andconventional surfactants to increase efficiency and decrease cost.The investigation results of cationic Gemini surfactants converting solid surface wettability indicated that cationic Gemini surfactants could convert oil-wet surface into waterwet surface, even into strong water wet surface. And as for water wet surface, most cationic Gemini surfactants could convert water-wet surface into weak water-wet surface. The investigation results in this part would provide the theoretical and practical guide for employing cationic Gemini surfactants to change the wettability of reservoir, so as to enhance oil displacement efficiency.Microscopic displacement course and results of cationic Gemini surfactants' solution indicated that, in capillary model, Gemini surfactants exhibited higher oil displacement efficiency than water, and at the same concentration, GS12-4 exhibited higher oil displacement efficiency than GS14-2. and in sand packed model, GS12-4 exhibited higher oil displacement efficiency than GS14-2, too. The two microscopic models and core flooding results indicated that Gemini surfactants solution have high oil displacement efficiency and wettability of solid surface also influences oil displacement efficiency a lot. At last, according to the microscopic displacement course and results, oil displacement mechanism of cationic Gemini surfactants was put forward, which includes reducing O/W IFT, converting the wettability of solid surface, conglomerating oil drop, forming oil zone and emulsifying crude oil, and etc.In all, cationic Gemini surfactants can be an effective oil displacement chemical in EOR area.