Preparation Of Magnetic Emulsifier And Their Application In Viscosity Reduction Of Heavy Oils

From a global perspective,the abundant marginal reservoirs including heavy oil and super heavy oil,are regarded as the major supplementary resources of petroleum.However,heavy oilexhibits a high viscosity and poor mobility due to the high-level content of resin and asphalt,as well as wax and heavy metals.Therefore,it is the key to reduce the viscosity of heavy oil so as to realize its efficient recovery.The emulsified viscosity-reducing technique of heavy oil,which could improve the flow of heavy oil,brings about convenience for the exploitation,transportation and processing of heavy oil,and is a promising heavy oil viscosity reduction technology in the 21st century.As a result,development of the efficient,economical and environmentally friendly emulsifier is crucial to solve the world energy crisis and realize the common goal of domestic and foreign researchers.In view of the excellent properties of magnetic nanoparticle emulsifierssuch asgood emulsifying ability,environmentally-friendliness,and good demulsification under the external magnetic field,in this thesis,we synthesize a series of magnetic emulsifiers based on the core of magnetic composite nano-particles Fe₃O₄@SiO₂,the surface of which is modified by functional groups and catalysts.The as-prepared magnetic emulsifiers are used to catalyze the aquathermolysis reactions of extra-heavy oil produced at Shengli Oilfield?Dongying,China?;and the viscosity-reduction abilities of the extra-heavy oils,as well as the sample viscosity,composition,elemental content change are evaluated.The main contents and results of this thesis are as follows:1.Synthesis and characterization of magnetic emulsifiersFe₃O₄nanoparticles were prepared by precipitation method followed by the synthesis of Fe₃O₄@SiO₂nano-particles via sol-gel method.Then the surfaces of Fe₃O₄@SiO₂nanoparticles are modified with hexamethyldisilazane?HMDS?and cetyltrimethoxysilane?CG1631?to prepare Fe₃O₄@SiO₂-HMDS and Fe₃O₄@SiO₂-CG1631.Control of the degree of surface modification can help achieve good oil and water emulsification function,and the emulsification mechanism is discussed.Fe₃O₄@SiO₂-HMDS/Feand Fe₃O₄@SiO₂-CG1631/Fe are prepared by in situ chemical reduction using FeCl₃·6H₂O as the precursor and magnetic emulsifier as carrier,and the formation mechanism of the supported magnetic emulsifier is analyzed.The structures of the as-synthesized magnetic emulsifiersare characterized by VSM,TEM,XRD,IR and BET.Results show that the magnetization of the magnetic emulsifier is54.3 emu·g^-1,the crystal form is complete and the water phase contact angle is about 80°.The O/W type forms Pickering emulsion with the magnetic response function.The XRD and BET data indicate that the nanometer iron particles are mainly supported in the form of microcrystalline on the surface of the emulsifier.2.The application of magnetic emulsifiers in viscosity reduction of heavy oil.The applications of magnetic emulsifiers in reducing the viscosity of the two kinds of tested heavy oils?1^#41670 cP and 2^#160000 cP?are investigated.Results show that under the dosage of magnetic emulsifiers of 1 wt%,the aquathermolysis reaction temperature of180 ^oC,and the aquathermolysis time of 24 h,the contact angle of the water phase is nearly80^oand the magnetic emulsifiers exhibit the optimal reaction performance.The viscosity of heavy oil 1^#can be reduced from 41670 cP to 8510 cP with a viscosity reduction rate of79.6%;heavy oil 2^#can be reduced from 160000 cP to 90790 cP with a viscosity reduction rate of 43.3%.Compared with the magnetic emulsifier,the supported magnetic emulsifier exhibit an improvement of viscosity reduction rate of heavy oil 1^#?viscosity 41670 cP?from79.6%to 85.6%,heavy oil 2^#?viscosity 160000 cP?from 43.3%to 50.9%.The viscosity reduction effect of the magnetic emulsifiers are Fe₃O₄@SiO₂-HMDS/Fe>Fe₃O₄@SiO₂-CG1631/Fe>Fe₃O₄@SiO₂-HMDS>Fe₃O₄@SiO₂-CG1631.The viscosity reduction effect of the supported magnetic emulsifiers are generally better than the unsupported emulsifiers.Hexamethyldisilazane?HMDS?is more suitable for the modification of the magnetic particles than cautyltrimethoxysilane?CG1631?.The viscosity reduction trend shows that the viscosity reduction effect of heavy oil 1^#?41670 cP?is better than heavy oil 2^#?160000 cP?3.The effect of magnetic emulsifiers on the compositions and elemental contents of heavy oils.The compositionsof the heavy oil samples and the elemental elements are analyzed.After the viscosity reduction reaction,the heavy oils have some changes:saturated hydrocarbon and aromatic components increase,resin and asphaltene decrease;N_H/N_C ratio increases and heteroatoms decrease.It is shown that the surface of the magnetic emulsifier in the oil-water interface is easily permeated in the associative structure of the viscous resin and asphalt molecules of heavy oils during hydrothermal emulsification and viscosity reduction reaction.The bare Si-OH has a competitive adsorption,which decompose C-S,C-N,C-O,and C=S,C=N,C=O and other heteroatom groups and breaks the van der Waals force,hydrogen bond and?-?electron between the resin and asphalt,so that the composition of the complex three-dimensional solid structures become loose and easy to form an emulsion.At the same time,high-temperature steam can produce H₂,which leads to hydrogenation reaction of unsaturated components of heavy oils,thereby reducing the viscosity and improving of the flow performance of tested heavy oils.