Preparation Of Pickering Emulsion Based On Nanometer Fe₃O₄ Particles And Evaluation Of Its Viscosity Reducing Effect On Heavy Oil

The reserves of heavy oil in the world are very rich,but heavy oil has high viscosity,poor fluidity,making it difficult to exploit.Heavy oil emulsification and viscosity reduction technology is a widely used mining technology in recent years.Emulsifying heavy oil into O/W type emulsion can effectively solve the problems of high viscosity and poor flowability of heavy oil.Therefore,emulsification and viscosity reduction technology of heavy oil with excellent emulsification and viscosity reduction ability is particularly important for heavy oil exploitation.This article is based on the hot solvent method to prepare nano Fe3O4 particles,which are compounded with surfactant OP-10,or coated with inorganic materials and modified on the surface of nano-Fe₃O₄particles.Two Pickering emulsification and viscosity reduction systems with excellent emulsification performance and magnetic response ability are obtained.Two Pickering emulsification and viscosity reduction systems were used to evaluate the performance of heavy oil hydrothermal emulsification and viscosity reduction,and the emulsification and viscosity reduction mechanisms of the two systems were explored and analyzed.Magnetic nano-Fe₃O₄particles were prepared using a hot solvent method.The effects of sodium citrate dosage,hexahydrate ferric chloride dosage,sodium acetate dosage,and reaction time on the structure and morphology of the product were analyzed.The optimal preparation conditions were determined as follows:sodium citrate dosage of 0.01mol·L^-1,hexahydrate ferric chloride dosage of 0.01mol·L^-1,sodium acetate dosage of 0.03mol·L^-1,reaction temperature of 200℃,and reaction time of 8 hours.The average particle size of nanometer Fe₃O₄particles is 240.86nm,which can withstand the high temperature of 300℃,the water contact angle is 30.0°,and is magnetic.The saturation magnetization is76.97emu·g^-1,which can form Pickering emulsion,but the stability is poor.The Pickering emulsion viscosity reduction system of Fe₃O₄nanoparticles combined with OP-10 was designed.When the addition of Fe₃O₄particles is 0.1wt%,the addition of OP-10 is 0.1wt%and the oil-water ratio is 5:5,the viscosity reduction effect can reach99.70%.Thermogravimetric analysis of OP-10 shows that OP-10 starts thermal decomposition after 150℃,so the system can only withstand 150℃at the highest and can be used for viscosity reduction of heavy oil at low temperature（<150℃）.The OP-10 emulsion viscosity reducing system composed of nano Fe₃O₄particles has magnetic response characteristics.This system can achieve emulsification demulsification up to 5 times by applying or removing an external magnetic field.Through the three steps of Si O₂coating,amino functionalization,and benzaldehyde modification,nano-Fe₃O₄particles can be transformed into Fe₃O₄@Si O₂-A grain.The average particle size of the synthesized products is 331.25nm,the water contact Angle is 71.9°,and the saturated magnetization is 67.32emu·g^-1.The Fe₃O₄@Si O₂-A particle emulsion viscosity reduction system was designed.When the amount of Fe₃O₄@Si O₂-A particle is 0.1wt%and the oil-water ratio is 5:5,the viscosity of heavy oil can be reduced by 99.65%.After aging at300℃for 4h,the system can still reduce the viscosity of heavy oil by 98.82%.Fe₃O₄@Si O₂-A particle emulsion viscosity reduction system has magnetic response characteristics,it can be applied or removed by an external magnetic field to achieve emulsification and demulsification up to 5 times.The emulsifying viscosity reducing mechanism of Fe₃O₄nanoparticles combined with OP-10 emulsion viscosity reducing system and Fe₃O₄@Si O₂-A emulsion viscosity reducing system is essentially the same.Both systems transform the emulsification of heavy oil into O/W Pickering emulsion,making the oil phase become the internal phase and the water become the external phase,thus dismantling the stacking of gum and asphaltene and preventing the coalescence of oil droplets.The friction between heavy oil turns into the friction between water film and water film,thus reducing the flow resistance and greatly reducing the viscosity of heavy oil.