Study On The Emulsifying Properties Of ASP Flooding System

In the process of enhanced oil recovery (EOR), chemical technology is a kind ofimportant tertiary oil recovery technology, in which alkali/heavy alkylbenzene sulfonates(HABS)/polymer system can form emulsion with oil, which is beneficial to the crude oilflooding, can greatly improve oil displacement efficiency. But the system has low saltresistance stability, low alkali tolerability, which is not suit for spread in oil fields. In addition,the oil-water interfacial tension is the main indicator to evaluate the surfactant, so studyingthe relation of oil-water IFT and stability of oil emulsion will further explain emulsification incrude oil flooding the mechanism.Nonylphenol polyoxyethylene ether can resist multivalence cation, have some goodperformance such as lower critical micelle concentration, good emulsification and so on, canimprove the stability of the oil recovery system in high salinity conditions. In this article, theinterfacial tension evaluation and emulsion stability evaluation are combined to study theperformance of associative surfactant containing HABS and nonylphenol polyoxyethyleneether(NP), the influence of the improvement of emulsion stability on the interfacial tension,then establish the relation of oil-water IFT and stability of oil emulsion.In this paper, the influences of the concentration of NaOH and HABS, temperature,viscosity, polymer and emulsion droplet size on the ASP system/daqing oil interfacial tension,the performance of associative surfactant containing HABS and NP. The results showed that:within the scope of the investigation, when ω(NaOH)is smaller than1.0%, the IFT between oiland water will reduce along with the prolong of contact time, and the needed minimumcontact time of oil and water (MCT)according to the lowest IFT is bigger than2h;whenω(NaOH)is bigger than1.0%, the MCT can be reduced to lower than1h, but theequilibrium interfacial tension is bigger than this lowest IFT; when NP is put into the system,the MCT value at low alkali concentration will decreased, such as when ω(NaOH)=0.8%, theMCT value can be shortened from2h to75min, but balance interfacial tension value increases.In addition, at the temperature of45℃, when ω(NaOH)=0.6%, total mass concentration of thesurfactant are0.05%and0.1%, in which ω(HABS):ω(NP)=9:1. The stability of crude oil emulsioncontaining NP is obviously better than single HABS system, within24h the separated waterratio can be decreased from17.5%,26.3%to7.5%. Nonionic surfactant can shorten the MCTneeded by the lowest IFT, but not necessarily lower the balance interfacial tension, and at thesame time can improve oil emulsion stability, so, decreasing the balance interfacial tensionbetween oil and water cannot be regarded as the guarantee of the emulsion stability,corresponding relationship between them does not exist.