| With the increasing consumption of conventional petroleum resources,the focus of exploitation is gradually shifting to heavy oil resources with abundant reserves.The main characteristics of heavy oil are high density,high viscosity and poor fluidity.In addition,the underground topography of the oilfield is complex and there are many rock fractures,which increase the difficulty of heavy oil exploitation.Thermal recovery is the main method of heavy oil at present.In recent years,cold recovery technology of heavy oil emerges quietly.However,both cold recovery and hot recovery technology of heavy oil involve emulsion viscosity reduction mechanism of heavy oil.However,the emulsification process of heavy oil is very complex,which is affected by many factors such as the amount of emulsifier,emulsification temperature,liquid-phase salinity and p H value.In this experiment,Jin 8-7and Chen 373 heavy oil were used as experimental objects to study the emulsification law and emulsion stability law of the two kinds of heavy oil under different influencing factors,and the emulsification kinetic equation of heavy oil was established.The main conclusions are as follows:(1)The basic physical property analysis of the two heavy oils shows that the viscosity of Chen 373 crude oil is significantly higher than that of Jin 8-7 crude oil;The content of heteroatom in asphaltene of Chen 373 crude oil is about 2.8 times that of Jin 8-7 crude oil.Both Chen373 crude oil and Jin8-7 crude oil have polar groups such as-OH,-NH,S=O,and the components containing polar groups are the main interfacial active components of crude oil,which affect the emulsification and emulsion stability of heavy oil.(2)The analysis results of emulsifying amount and particle size of heavy oil during the process of forming water-in-oil emulsion under different conditions showed that the higher the emulsifying temperature,the higher the equilibrium oil content of emulsion;Low concentration of Na Cl and emulsifier content can improve the emulsification capacity of heavy oil.Heavy oil is difficult to emulsify in acidic environment,and the emulsification capacity of heavy oil increases with the increase of p H value of water phase.During the emulsifying process,the particle size of the emulsion decreases first and then increases with the extension of emulsifying time,and finally tends to be flat.The emulsification mechanism of heavy oil was deduced comprehensively.The emulsification process of two kinds of heavy oil included rapid emulsification stage and emulsion ripening stage.The rapid emulsification stage is mainly the dispersion process of crude oil droplets,and the droplet coalescence rate increases gradually in the emulsion ripening stage,and finally the droplet dispersion rate is equal to the coalescence rate.(3)The second-order kinetics equation was used to fit the emulsification data under different conditions.Except for the emulsification process under acidic conditions,the error between the calculated and experimental values of the equilibrium emulsification amount of crude oil was less than 5%,indicating that the emulsification process was in line with the second-order kinetics characteristics.(4)the stability of the emulsion research results show that the modulus of oil-water interface expansion along with the increase of emulsifier concentration appeared three peaks,increases with the concentration of Na Cl increased before they are lower,the greater the frequency and interface expansion,the higher the modulus of oil-water interface expansion,shows that the strength of interface molecular inter-atomic forces,the bigger the formation of the interfacial film strength.Increasing the temperature will decrease the stability of the emulsion.The stability of the emulsion was firstly increased and then decreased with the increase of Na Cl concentration,and the stability of the emulsion was the best when the concentration was 2wt%.Increasing the concentration of emulsifier can significantly improve the stability of emulsion. |
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