Preparation And Performance Research Of Fe₃O₄ Nanoparticles-based Viscosity Reducers For Heavy Oil

With the growing demand of energy consumption,conventional oil has been declining year by year.The heavy oil with abundant reserves has become the current research focus.The development of high-efficient viscosity reducers for heavy oil is of great significance for improving its recovery.Fe3O4 nanoparticles-based viscosity reducers were selected as research object for this work.The four components and physical properties including viscosity of Chenping and GD2 heavy oil from Shengli Oilfield were measured.Then the relationship between viscosity and shear rate,temperature,diluent and time was studied,which provided a reasonable basis for the evaluation of viscosity reduction.Fe3O4 nanoparticles were surface modified with ymethacryloxypropyltrimethoxysilane(KH570),triethoxyvinylsilane(A151)and oleic acid(OA)to obtain lipophilic Fe3O4-KH570,Fe3O4-A151,Fe3O4-OA,and their average net degree of viscosity reduction(DVR)for Chenping heavy oil were 27.91%,29.44%and 51.27%,respectively.The modified Fe3O4 has good recycling potential in magnetic field.The DVR of modified Fe3O4 for GD2 heavy oil was lower than Chenping heavy oil.The dispersion stability of nanoparticles in the carrier fluid has the greatest impact on DVR,followed by the ability to disrupt asphaltene aggregates.Surface lipophilicity increasement is essential for viscosity reduction.However,nanoparticle size and the ability to adsorb asphaltenes are not directly related to DVR.Ternary oil-soluble polymer OSN was synthesized with octadecyl acrylate,styrene and N-methylol acrylamide.When the monomer mole ratio is 6:4:1,the reaction temperature is 70℃,and the reaction time is 6 hours,OSN has optimal synthesis conditions.Then Fe3O4-KH570 and those three monomers were used to synthesize quaternary nanocomposite viscosity reducers OSNT.Generally,DVR of OSNT was higher than that of OSN.At a shear rate of 10 s-1 and 50℃,DVR increased from 29.25%to 38.93%.Nanoparticles enhance the rigidity and temperature sensitivity of polymer,and its lubricating effect can cooperate with the polymer to reduce viscosity.DVR of OSN and OSNT to GD2 oil was lower than that of Chenping oil.Gromacs was used for dynamic simulation calculation and the results showed that the addition of OSN significantly reduced the average cluster size of asphaltenes,which made the system looser and reduced the viscosity of heavy oil.Scanning electron microscopy results showed that the OSNT destroyed the structure of asphaltene aggregates and then the particles became more uniform and interlamellar spacing increased.After adding OSN,the storage modulus and loss modulus were reduced by 92.84%and 72.17%,respectively,and after adding OSNT,the storage modulus and loss modulus were reduced by 95.16%and 78.84%,respectively.This proved microscopically that the viscosity reducer can destroy the internal network structure and reduce elastic component of the heavy oil.The heat loss ability was also reduced.OSNT had a larger change than OSN,which was consistent with the viscosity reduction of heavy oil after adding viscosity reducers.The successful development of two kinds of Fe3O4 nanoparticles-based viscosity reducers with excellent DVR in this work expands the selection of heavy oil viscosity reducers and provides new ideas for improving heavy oil recovery.