| China is the world’s largest importer of crude oil,and is currently in a period of rapid industrialization and urbanization.During the"14th Five-Year Plan"period,the country put energy security at an important position in the development strategy again.With the increase of mining life,the light crude oil resources will gradually reduce.However,China is rich in heavy oil resources.Compared to conventional crude oil,heavy oil has the characteristics of high viscosity,high density and poor fluidity,which make it difficult to be extracted and transported.Emulsification and viscosity reduction can effectively reduce the viscosity of heavy oil and improve its fluidity,thereby improving transmission efficiency and reducing energy consumption.At present,the emulsification viscosity reduction technology is widely used in the exploitation and pipeline transportation of heavy oil.In this paper,based on the acid amine condensation reaction,polyethylene polyamine(PEPA)-based emulsifiers and polyethyleneimine(PEI)-based emulsifiers were prepared through grafting different types and proportions of lipophilic groups on PEPA and PEI backbones,respectively.The synthesized emulsifiers were characterized by FT-IR,~1H NMR and elemental analysis.Subsequently,taking the viscosity reduction rate of heavy oil of Shengli Oilfield as the primary evaluation indexes,we studied the effects of the type of grafted organic carboxylic acid,the graft ratio and the type of the skeleton molecule on the emulsification performance.The reasons for the performance differences among different emulsifiers were analyzed by means of optical microscopy,surface tension,etc.,and the mechanism of viscosity reduction was supposed.The main research content of this article can be divided into the following two parts:(1)Synthesis of PEPA grafted long-chain carboxylic acid emulsifier and its emulsification performance for extra-heavy oilPEPA-based series emulsifiers were prepared by allowing PEPA to react with n-octanoic acid,n-decanoic acid,dodecanoic acid and myristic acid,respectively and emulsifier was characterized by FT-IR and elemental analysis.Viscosity reduction effects of PEPA-based series emulsifiers on Shengli extra-heavy oil(154080 m Pa·s)were evaluated and the results showed that the prepared emulsifier PEPA-dodecanoic acid-2-1 had a good emulsifying viscosity reducing effect on Shengli extra-heavy oil.In the laboratory,the viscosity of the emulsion formed can be reduced to 35 m Pa·s,and the viscosity reduction rate is over 99% when the dosage is 1 wt%and the oil-water ratio is 60:40.The emulsifier not only has high viscosity reduction efficiency,but also stability induce a heavy crude oil emulsion.According to the optical microscopic observation,the emulsifier can induce to form a stable O/W emulsion between heavy oil and water.The results of critical micelle concentration and surface tension tests showed that the emulsifier PEPA-dodecanoic acid-2-1 had the best solubility and surface activity.(2)Synthesis of PEI grafted long-chain carboxylic acid emulsifier and its emulsification performance for extra-heavy oilIn order to further improve the stability of emulsifier molecules,PEI is selected as the backbone,and n-octanoic acid,n-decanoic acid,dodecanoic acid and tetradecanoic acid are grafted on the PEI backbone.PEI-based series emulsifiers are used in the emulsification experiment of Shengli extra heavy oil.The emulsification experiment results showed that the emulsifier PEI-n-octanoic acid-1-30 had good emulsification performance.Under the conditions of oil-water ratio of 60:40,temperature of 50°C,and dosage of 0.5 wt%,Shengli extra heavy oil can be completely emulsified to form a stable O/W emulsion with a viscosity reduction rate of over 99%.Compared to the emulsifier molecule synthesized with PEPA as the backbone,the dosage of PEI-based emulsifiers is reduced by half,and the salt resistance is greatly improved.In addition,under the same conditions,the emulsification performance of PEI-n-octanoic acid-1-30 is better than those of four common commercial emulsifiers Tween 40,sodium heavy alkylbenzene sulfonate,petroleum sulfonate and fatty alcohol polyoxyethylene ether-9. |
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