Studies On Synthesis?characterization And Application Of LH-Petroleum Sulfonates

Petroleum sulfonate is one of most efficient surfactants in tertiary oil recovery due to its high interfacial activity, excellent compatibility with oil and low lost. However, the petroleum sulfonates, which were synthesized from raw oils of different sources, will be very different in many respects such as the compositions, average molecular weights, molecular weight distributions and interfacial tensions. Therefore, in order to improve the oil production in the block of LH-oilfield, LH-petroleum sulfonate was synthesized in our laboratory by using minus three lines distillate produced from LH-oilfield as raw material, and fuming sulfuric acid as sulfonating agent. The compositions, chemical structures, molecular weight distributions, and oil displacement performances of LH-petroleum sulfonate were also characterized. Moreover, the differences in chemical compositions and interfacial tensions between LH-petroleum sulfonate and two commercially available petroleum sulfonates were compared. At the same time, alkyl benzene sulfonates with different chain length were synthesized, which were used for further explore the infulence of composition and structure of petroleum sulfonate on the oil water interfacial of LH-oilfield. The detail results are as below:(1) The optimal synthesis condition of LH stock oil was established: the acid/oil ratio was 0.4:1, reaction temperature 50 ?, reaction time 40 min, the amount of solvent(1,2-dichloroethane) was 10 mL/g raw oil. The crude product active content was more than 60%; the product which was synthesized in optimum conditions appeared the characteristic stretching vibration absorption peak in the vicinity of 1053 cm-1 and 1179 cm-1. The further studies found that LH-petroleum sulfonate molecules contained 2-3 aromatic rings, the alkyl side chains was 30-32 carbon atoms, and the average number of methyl groups was 6-8. At the same time, the two-phase titration method for the mean relative molecular amount of LH-petroleum sulfonate was 751.3 g/mol, and the electrospray ionization mass spectrometry was 675.2 g/mol. The molecular weight was mainly distributed in the range of 400-650 and 900-1100, which had a wide and moderate molecular weight distribution.(2) LH-petroleum sulfonate was poor in reducing oil-water interfacial tension lonely, no matter thin oil or heavy oil. But the oil-water interfacial tension of thin oil and heavy oil from Liao He oilfield can reach 10-2 mN/m and lower orders of magnitude when some auxiliary surface active agent was added in this system, such as inorganic salt or alkali. When LH-Petroleum Sulfonate was mixed with nonionic surfactant 6501, this thin oil system could obtain ultra-low interfacial tension(10-3 mN/m) in the ratio of 10:90, 20:80 and 30:70, and exhibited good emulsifying properties. The interfacial tension of LH-Petroleum Sulfonate/heavy oil system could reach 10-4 mN/m magnitude in the ratio of 50:50. The results of indoor simulation flooding experiment also showed that oil displacement efficiency could be increased to 7.9% in the mixing ratio of 20:80(LH-petroleum sulfonate: 6501) and the injection rate was 0.55 PV.(3) With no auxiliary surface active agents, heavy alkylbenzene sulfonates could make the interfacial tension reach to 10-2 mN/m magnitude for dilute oil I, dilute oil III and heavy oil from LH-oilfield, and the interfacial activities were the best. But LH-petroleum sulfonates and Daqing petroleum sulfonates could only reduce oil-water interfacial tension to 10-1 mN/m magnitude. When sulfonate surfactants were mixed with auxiliary surface active agent, such as sodium carbonate or sodium chloride, the interfacial tension about heavy oil could be significantly reduced to 10-3 mN/m magnitude for LH-petroleum sulfonate, and the interfacial tension of the other two sulfonate surfactants could also reach to 10-2 mN/m magnitude. All these results illustrated that: heavy alkylbenzene sulfonates were the most suitable surface active agent for LH-oilfield between these three kinds of surface active agents, followed by LH-petroleum sulfonates or Daqing petroleum sulfonates. The reason might be that the average relative molecular weight and the molecular weight distribution range of heavy alkylbenzene sulfonates were moderate, while that of LH-petroleum sulfonates were large and wide, and Daqing petroleum sulfonates were small and narrow.(4) In the conditions of alkalinity concentration(1%) and the assistance of effective concentration of surfactant(0.05%), the orders of different chain length of the alkyl benzene sulfonate surfactants reduced the oil-water interfacial tension of thin oil III were: cetyl dimethyl benzene sulfonic acid sodium(<10-2 mN/m) performanced the best in reducing oil-water interfacial activity, followed by the hexadecane toluene sulfonic acid sodium(5.4*10-2 mN/m). The interfacial activities of long carbon chain octadecyl methyl benzene sulfonic acid sodium and shorter carbon chain of tetradecyl methyl benzene sulfonic acid sodium were poor in reducing oil-water interfacial activities. The studies of structure activity relationship showed that: cetyl dimethyl benzene sulfonic acid sodium or hexadecane toluene sulfonic acid sodium might be the effective main body sulfonate surfactant for thin oil ?.