Research On Heavy Crude Oil Viscosity Reduction By Ionic Liquids Microemulsion

At present,the non-upgraded heavy oil viscosity reduction has some deficiencies,such as poor universality and unobvious economic benefits,while the upgraded heavy oil viscosity reduction has some stringent requirements,such as high temperature and high efficiency catalyst.Inspired by the designability of ionic liquids and asphaltene affinity,it is planned to reduce viscosity in situ at reservoir temperature,which can not only reduce energy loss and environmental pollution,but also obtain good economic benefits.In view of the dense structure of heavy oil and the small contact area between ionic liquids and asphaltenes in heavy oil,the ionic liquid and the oil phase（ILs/O）microemulsion were constructed,and the ionic liquids were introduced into the reconstituted fractions of heavy oil to achieve viscosity reduction by using the advantages of microemulsion carrying,small particle size and strong permeability.In this paper,the research work has been completed by optimizing ionic liquid synthesis conditions,ionic liquid microemulsion preparation,ionic liquid microemulsion viscosity reduction test,ionic liquid microemulsion construction and viscosity reduction mechanism.First,the target ionic liquid[bmim]Br·Fe Cl₃ was synthesized by a two-step method,the ratio of reactants,reaction time and temperature were selected and optimized,and the physical and chemical properties of synthetic ionic liquids such as conductivity,viscosity and density were evaluated.Then,the ionic liquid microemulsion was constructed using the HLB value method and the pseudo-ternary phase diagram method,and factors such as the appropriate HLB value,the type of compound surfactant,the type of alcohol,and the ratio of alcohol to surfactant were selected.Furthermore,the viscosity reduction experiments of heavy oil by ionic liquid microemulsion were carried out.The effects of Fe Cl₃ mole fraction,ILs/heptane ratio,water content,reaction temperature,reaction time and hydrogen donor on viscosity reduction rate were studied.After the viscosity reduction,the four components and element content of the heavy oil were measured and analyzed.Finally,the construction and viscosity reduction mechanism of ionic liquid microemulsion were discussed and studied respectively.The results showed that the optimal ratio of 1-Methylimidazole to n-butane bromide was1:1.1 at 70℃,and the condensation reflux reaction time was 18 h.The maximum yield of[bmim]Br was 91.8%.In addition,the ionic liquid microemulsion used n-heptane as the oil phase and[bmim]Br·Fe Cl₃ instead of the water phase.The ratio of ionic liquid to oil phase was4:6,Span-80:JFC=0.78:0.22,the co-surfactant was n-butanol,and the mass ratio of alcohol to compound surfactant km was 1.5.According to the above method,a nano-level ionic liquid microemulsion with good temperature resistance and stability was obtained,and the different types of ionic liquid microemulsions were classified by the conductivity method and molecular simulation.At the same time,through the experimental study of viscosity reduction of heavy oil,it was found that the changes of four components,average molecular weight and element content of four kinds of heavy oil with different viscosity before and after viscosity reduction had certain commonness,in which the content of saturated hydrocarbon and aromatic hydrocarbon increased,resin,asphaltene and sulfur element decreased,which proved that ionic liquid microemulsion had played a role of reducing viscosity successfully.