| As a mature means of tertiary oil recovery, the polymer flooding has an extensiveapplication in oil fields. Partially Hydrolyzed Polyacrylamide(HPAM) is the most commonlyemployed polymer in polymer flooding, which possess the advantages of high viscosity，andobviously enhance the oil recovery. On the other hand, water phrase viscosity increased inproduced fluid by polymer flooding, which causes oil and water difficult to settle separation.However, at present there is lack of studies on the effect of the crude oil components andadditives to the stability and dehydration of crude oil emulsion. This thesis mainly studied theinterfacial properties of crude oil from Gudao and its acid-base fractions, and additionallyinvestigated the influence of the properties on the stability of crude oil emulsion.The Gudao crude oil was separated into four components (saturated, aromatic, resin,asphaltene) by means of fluid-soild adsorption chromatogram. The crude oil is separated intoacid, base, amphoteric and neutral fractions by ion exchange chromatography (IEC). Theelementary composition, molecular weight, IR spectrum of crude oil and its four fractionswere investigated. It has been systematically studied the influence of HPAM, sediment, anddemulsifies on stability of crude oil emulsion, the dilational viscoelasticity and surfacepressure.The results show that the Gudao crude oil is heavy petroleum, and the structure of resinand asphaltene is complicated. The percentage and the hetero-atom content of the heavycomponents from resin or asphaltene are higher. The isolation of crude oil and propertiesstudy proves that the sizes of the fractions were in the order neutral fraction> acidic fraction> amphoteric fraction> basic fraction. The molecular weights of the four fractions were in theorder amphoteric fraction> acidic fraction> basic fraction> neutral fraction. This shows thatAmphoteric fraction was the heaviest and most complex structure fraction in Gudao crude oil.The H/C ratios of the crude oil and its fractions were in the order neutral fraction> crude oil>basic fraction> acidic fraction> amphoteric fraction. The acid number of the acidic fractionwas the highest; the acid number of the neutral fraction was much lower. The result of FT-IR spectra of functional fractions of Gudao crude oil shows that the dispersions of sulfur,nitrogen and oxygen groups was meanly focus in Amphoteric, Acid and Base fractions.The effect of HPAM that of different molecular weight and concentration on the stabilityand deemulsification of simulate oil emulsion was researched systematically. The resultshowed that the stability of simulate oil emulsion order was asphaltene, resin, oil withoutresin and asphaltene, asphaltene was the main active component; the effect of HPAM oncrude oil and three components simulate oil were different. Besides HPAM can result tothicker interface layer and bad water quality.Through the observation of emulsion micrograph, the smaller droplet particle diameterand the more thickness of droplet, the more stabler of emulsions was. The stability ofasphaltene was the biggest. The presence of sediment increases the stability of crude oilemulsions. But the modified sediment decreases the stability of crude oil emulsions. At thepresence of sediment in water phrase, surface film pressure of crude oil and its fractionsincreased, inflection point moved forward. Sediment had a big influence on dilationalviscoelasticity of crude oil and its fractions. As concerntration of sediment increasing, thedilational modulus, phrase, elasticity and viscosity increased.The Gudao crude oil and its fractions π-A/A0isothermal curve were different. The surfacefilm pressure of crude oil and its polar fractions decreased follows as: asphaltene, crude oil,resin, saturated fraction, aromatic fraction. The final film pressure of asphaltene was muchhigher than other fractions. The final film pressure of crude oil and its acidic-basic fractionsdecreased as: amphoteric fraction, acid fraction, base fraction, crude oil, neutral fraction, andamphoteric fraction film was the strongest.As the pH number increasing, the surface film pressure of aromatic fraction, resin,asphaltene and crude oil increased. With the increasing concentration of HPAM in waterphrase, the film pressure of crude oil, acid, amphoteric and neutral fractions increased, butbase fraction was the reverse. As the molecular weight of HPAM in water phrase increasing,film pressure of neutral fraction was decreased, and when the molecular weight of HPAM was3.70×106g·mol-1, the film pressure of crude oil, acid, base and amphoteric fractions was thehighest, at7.12×106g·mol-1was the lowest. As the concentration of HPAM increased, thefilm pressure of crude oil and its fractions increased. The smaller molecular weight of HPAM,the higher surface film pressure was.The molecular weights and concentrations of HPAM had a large influence on thedilational modules, dilational elasticity, and dilational viscosities of the crude oil and its fractions. As the molecular weight of HPAM increased, the dilational modules, elasticity, andviscosities of the oil/water interfacial films of the crude oil and its four fractions firstincreased and then decreased. When the PHPAM molecular weight was7.6×106g mol1, thevalues of these parameters were highest and the interfacial films were most stable. This showsthat medium-molecular-weight HPAM in the water phase was beneficial to crude oil emulsioninterfacial film stability.Across the entire range of HPAM molecular weights used in the experiments, the crudeoil and amphoteric fraction oil/water interfacial films were the most stable; the interfacialstabilities of the acidic, basic, and neutral fractions were a little lower. As the HPAMconcentration increasing, the oil/water interfacial film dilational modules of the crude oil andits fractions consistently increased; the higher the concentration was, the more stable theoil/water interfacial film was, and the more stable the emulsion was. Across the entire rangeof HPAM concentrations used in the experiments, the dilational modulus of the crude oil wasthe largest and the dilational modulus of the acidic fraction was the lowest.As the dilational frequency increased, the oil/water interfacial film dilational modules,dilational elasticity, and phase angles of the crude oil and its fractions increased, but thedilational viscosities decreased. Across the entire frequency range, the dilational modulus ofthe crude oil was far bigger than those of the other fractions; the acidic fraction had thesmallest dilational modulus, but those of the amphoteric, neutral, and basic fraction oil/waterinterfacial films were equal.Langmuir-Blodgett(L-B) technology was used to study the influence of four differentstructure demulsifiers on crude oil and its acid/base fractions(acid fraction, base fraction,amphoteric fraction and neutral fraction) L-B properties. The dependence of interfacial filmproperties on demulsifier concentration was also expounded. The results showed that branchchain demulsifier AE8025could decrease remarkably the oil-water interfacial film pressure ofcrude oil and its fractions. With the concentration of demulsifier increases, the surface filmpressure was decreased gradually. The decrease range of acid fraction, base fraction andamphoteric fraction was more than neutral fractions by addition of AE8025. The decreaserange of crude oil and its fractions surface film pressure was related to the structure ofdemulsifier. The branch chain demulsifier had stronger ability to reduce surface film pressureof Gudao crude oil and its fractions. It showed that the demulsifier molecules can almostsubstitute the molecules of surface-active fractions at the interface of crude oil and itsfractions emulsion. The substitution ability of branch chain demulsifier was more than straightchain demulsifier. Demulsifier had a great effect on base fraction surface film pressure than other fractions (acid fraction, amphoteric fraction and neutral fraction) at the same demulsifierconcentration. At presence of HPAM, the strength of interfacial film was enhanced by theabsorption of HPAM on oil-water film, so demulsification effency was reduced, butdemulsifier with branch chain has a better effect than demulsifier with straight chain.The demulsifier SD-5for Gudao5#was developed. The water content of the treatedwater decreased from1.22%to0.70%. |
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