| The interfacial tension was taken as the main measure indicator in the development of oildisplacement system based on the surfactant, the interfacial tension of system should come to10-3mN/m degree. Single kind of surfactant couldn’t meet the requirement, while the mixture ofdifferent kinds of surfactants acted the synergistic effect could reach10-3mN/m degree, it alsocan increase the stability of colloform, decrease the absorption of surfactants in the stones.Alkaline-surfactant-polymer (ASP) system based on the chemical surfactant is the primarymethod in enhancing oil recovery, alkylbenzene sulfonate (ORS) as the major chemicalsurfactant is used widely. But, alkylbenzene sulfonate has several disadvantages in the progressof preparation and employing, such as non-renewable, toxicity, hard-degradability. So it hasbecome the hot field in the world that developing the newly, high-effective, low-toxicity,easily-degradable surfactant used in the oil displacement system.Biosurfactant is a newly kind of surfactant, it have several advantages over chemicalsurfactants, such as lower critical micelle concentration (CMC), lower toxicity, higherbiodegradability, and better environmental compatibility and widespread application comparedto chemical surfactants. The biosurfactant which was secreted by the microorganism also canproduct special functional groups which are hardly compounded by chemical approach.Compared with the widely investigated conventional surfactants, the mixture of differentbiosurfactants such as sophorolipid（sSL） and rhamnolipid（sRL） are less frequently reported.Mixture of biosurfactant and alkylbenzene sulfonate (ORS) systems was more frequentlyinvestigated. Mixture of biosurfactants with better interfacial activity, lower critical micelleconcentration (CMC), more stable micelle structure can enhanced oil recovery, decrease the costof oil displacement.The study based on the system of biosurfactant rhamnolipid fermentationliquor and biosurfactant-sophorolipid, take the interfacial tension as the main evaluation index, toinvestigate the change of interfacial tension at different ratio of biosurfactant-rhamnolipid-fermentation liquor and biosurfactant-sophorolipid, the compatibilityamong alkaline, surfactant and polymer and resistance of temperature and salt. What to measurethe efficiency of the oil displacement through the simulation experience of oil displacement wasprovided underlying theory for practical using. The main results were summarized as follows:1、The preparation and the property evaluation of the synergistic system of“RL/SL”(1) The synergistic effect between sophorolipid and rhamnolipid was studied in this paper. Wecan conclude that the interfacial tension of system can achieve0.8231mN/m, when the totalweight of biosurfactant was0.15%, the ratio of sophorolipid and rhamnolipid-fermentationliquor was1:4. Contrast with the system single rhamnolipid and single sophorolipid, theinterfacial tension of the synergistic system of“RL/SL”decreased41.6%and57.6%. Thesynergistic system of“RL/SL”acted synergistic effect.(2) There was compatibility between sodium carbonate, polymer and the synergistic systemof“RL/SL”. Otherwise, compared with organic alkali, the inorganic alkali(sodium carbonate)could decrease the interfacial tension of the synergistic system of“RL/SL”more effective. Whenthe concentration of sodium carbonate was0.8%, the interfacial tension of system comes to10-3mN/m degree, and the emulsification index comes to the maximum. As the concentration ofpolymer increased, the viscosity rose, the interfacial tension of system essentially unchanged, actas the synergistic effect.(3)Taken the interfacial tension as the main evaluation index, the paper studied the influenceof salinity and temperature to the compound system. As the temperature rises, the interfacialtension of the system decreases. At30℃~60℃, the interfacial tension of the system decreasesquickly, when the temperature is above60℃, the interfacial tension of the system is barelydecreased; When the salinity is below15000mg/L, the interfacial tension of the system cancomes to10-3mN/m degree. We can conclude that, at a broad range of temperature and salt, thesystem act well in the resistance of temperature and salt; The synergistic system had goodemulsifying properties for crude oil of Shengli.2、The effect evaluation of enhancing-oil recovery of the synergistic system(1) Through the simulation experience of oil displacement, simulated oil reservoirenvironment of oil field of Shengli. The paper evaluated the efficiency of oil displacement of“RL/SL/sodium carbonate” system,“RL/SL” system and the system of sodium carbonate. The enhanced oil recovery of “RL/SL/sodium carbonate” system,“RL/SL” system and the system ofsodium carbonate was30.30%、15.50%、4.20%. The enhancing-oil recovery of “RL/SL/sodiumcarbonate” system was higher than “RL/SL” system and the system of sodium carbonate. Itturned out, the synergistic system “RL/SL” with sodium carbonate act good synergistic effect inenhancing oil recovery.(2) Through the simulation experience of oil displacement, the paper researched the effect ofoil displacement of the “RL/SL/sodium carbonate” system in the different equilibrium andinstantaneous interfacial tension, to ensure the influence of interfacial tension for enhanced oilrecovery. It turned out, when the concentration of sodium carbonate was0.2%, the instantaneousinterfacial tension of the system can come to10-3mN/m degree; however, when theconcentration of sodium carbonate was0.6%, the equilibrium interfacial tension of the systemcan come to10-3mN/m degree; The experience also proves that the efficiency of oildisplacement of system was related with the interfacial tension of the system(not onlyequilibrium interfacial tension but also instantaneous interfacial tension), As the interfacialtension of the system decreases, the efficiency of oil displacement of system arises; When theequilibrium interfacial tension doesn’t come to10-3mN/m degree, the minimuminstantaneous interfacial tension comes to10-3mN/m degree, the system can also improve oilrecovery well. It indicated that the synergistic system which has a strong application potentialcan not only enhance oil recovery observably also reduce the cost of sodium carbonatedecreasing the injury for earth.(3) Through the simulation experience of oil displacement, the enhancing-oil recovery of“RL/SL/sodium carbonate” system was26.2%higher than “petroleum sulfonate/sodiumcarbonate”system. The synergistic system of biosurfactant was better than that of chemicalsurfactant in enhancing-oil recovery; Compared with other the synergistic system of chemicalsurfactant used commonly, the studied synergistic system can reduced the cost of surfactantabout0.15%,0.6~1%of sodium carbonate. It can reduce costing of oil displacement and theinjury of earth. So the studied synergistic system has a strong application potential. |
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