Studies On Series Of 1,3,5-Triazine Surfactants In Alkali-free Flooding

A series of pure surfactants with 1,3,5-triazine structure in alkali-free flooding are designed and synthesized in this dissertation. In order to provide theoretical fundamentals for surfactant molecules design in enhanced oil recovery, the relationship between molecular structure and interface properties of these kinds of sufactants are studied, the molecular structure of these kinds of sufactants that can low the interfacial tension to ultra-low values are investigated, and the mechanism on producing ultra-low interfacial tension by microcosmic point of view are interpreted.Firstly, a series of single long-chain 1,3,5-trazine surfactants (A-MCTn) homologue with various lengths of hydrocarbon chains and double long-chain 1,3,5-trazine surfactants (A-DCTn-m) homologue with various symmetry degree of hydrocabon chains are synthesized by cyanuric chloride and aliphatic amines, and the structures of the intermediates and target compounds are confirmed by EI-MS,1H NMR,13C NMR and IR.Secondly, the interface performances of these synthesized surfactants are investigated. It is found that A-DCTn-m surfactants show high surface activity comparing with A-MCTn. The interfacial tension behaviors in alkane/aqueous solution system and crude oil/aqueous solution system of the serise of double long-chain 1,3,5-trazine surfactants are investigated respectively. The results of the studies of alkane preference indicate that the minimum numbers of alkane carbon (nmin) of A-DCTn-m surfactants are accorded with their structures, the more the total carbon number is, the higher the nmin is. The dynamic interfacial tension of surfactant-only decreases monotonically against alkane but goes through a minimum against crude oil. It is found that A-DCT8-8, A-DCT10-8, A-DCT12-8, A-DCT10-10 and A-DCT12-10 can reduce the interfaical tension between crude oil and aqueous sulotion to ultra-low value, but only A-DCT10-8 and A-DCT12-8 can maintain ultra-low interfacial at wide range concentrations and against various crude oils. The results indicate that not only the surfactant structures but also the lengths of the hydrocarbon chains would affect the decrease of interfacial tension. In addition, other influencing factors on interfacial tension, including temperature, sodium chloride, surfactant homologue mixture system, polymer and sodium carbonate, are also investigated. The resultes show that the series of surfactants have a certain temperature and salt resistance, appropriate homologue mixture system reveals high interface activity, the addition of polymer to the system can make the interfacial tension increase, and the addition of sodium carbonate can reduce the interfacial tension of system to ultra-low value but different surfactant system requiring the different amount of sodiun carbonate. The interfacial tension behavior between crude oil and aqueous solution of the MAS amphoteric surfactants are studied, and the highest interface activity of MAS amphoteric surfactants of carboxylate-type is observed.Lastly, the formation mechanism of ultra-low interfacial tension is investigated, and it is found that mass transfer does not occur and no surfactant molecules diffuse from water phase into oil phase at low surfactant concentration, and the content of A-DCT6-6 molecules at the interface is far below than that of A-DCT12-8 molecules at the interface. However, these two surfactants all form middle phase microemulsion. Therefore, the producing mechanism of ultra-low interfacial tension is propably decided by the amount and status of the adsorption layer of the surfactant molecules at the interface.