Studies On Alkylbetaine Surfactants Derived From S-Triazine In Alkali-free Enhanced Oil Recovery

This thesis has designed and synthesized ten kinds of carboxyl betaine surfactants derived from s-triazine. The relationship between surface activity and surfactant structure has been studied and the interface activities between the surfactants and alkane as well as crude oils from Daqing Plant2and Plant4have been explored. Comparison with corresponding sulfonate triazine surfactants has made to provide guidance for molecular design of flooding surfactants.Firstly, in this paper, symmetric and asymmetric-chain carboxyl betaine s-triazine surfactants BCn-m have been synthesized through molecular design with s-triazine, sodium chloroacetate, fatty amines and N,N-dimethyl-1,3-propanediamine as raw materials. As a result, the structures of the products are confirmed by mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance1HNMR and13CNMR.Surface activity and interface activity of the synthesized surfactants have been explored. Surface activity of surfactants with total carbon numbers of hydrophobic chains in the range of16to22are better, its γcmc is5～20mN m-1lower than that of other surfactants. Interface activity between the s-triazine surfactants and alkanes/crude oil is the research focus. Study shows that the lowest alkane/water interfacial tensions of BC8-8, and BC10-BC12-8BC14-8, BC10-10and BC12-10are close to10-3mN m-1. As the surfactant concentration increases, alkane/water interfacial tension and equilibrium time of dynamic interfacial tension are smaller. Alkane/water interfacial tension and equilibrium time of dynamic interfacial tension grows larger after the addition of NaCl. In a wide concentration range, the oil-water interfacial tensions between BC8-8, BC10-8, BC12-8and Daqing Plant2crude oil and Daqing plant4crude oil are down to10-2～10-3mN m-1. As the surfactant concentration increases, the equilibrium time of dynamic interfacial tension becomes shorter time, and the equilibrium interfacial tension increases first decreased and then increased, existing an optimal surfactant concentration. BC8-8, BC10-8and BC12-8exhibit temperature tolerance ability. After adding electrolyte, interfacial tension between BC10-8and crude oil increased while that of BC12-8reduced to some extents. BC12-8mixed with surfactants of shorter hydrophobic carbon chain show higher interfacial activity. Mixed system of BC12-8, BC10-8with Na2CO3show higher interfacial activity Lastly, comparision between BC8-8, BC10-8, BC12-8and corresponding sulfonate triazine surfactants were made. It shows that the carboxylate and sulfonate triazine surfactants exhibit poor salt tolerance while interacting with alkane. While interacting with Daqing Plant2crude oil, compared with sulfonate surfactants, carboxylate surfactants show greater temperature resistance, better electrolyte resistance, higher stability of the homologue complex systems and polyacrylamide.