Synthesis And Performance Evaluation Of Nano-silica Composite Viscosity Reducer

Decrease of light crude oil reserves has led to the need for heavy oil development.The high viscosity of heavy oil is the key factor that restricts its recovery.Therefore,it is very significance to reduce the viscosity of heavy oil.Nanocomposite material is a new chemical viscosity reducing technology applied in heavy oil development,which retains the function of conventional oil-soluble polymer viscosity reducing agent and synergizes with the specific function of nano particles.Therefore,this paper takes Shengli Chenping heavy oil as the main research object to design and synthesize an oil-soluble nanocomposite viscosity reducer and explore its viscosity reduction effect.First of all,the best visco-reducing nanomaterials were screened out from nano silica,alumina and zinc oxide,which was nano silica.Then,octadecyl acrylate,4-vinylpyridine and acrylamide were used as organic monomers to graft copolymerization with modified nano-Si O₂ dispersion,azodiisobutyronitrile was used as initiator and toluene was used as reaction solvent.An oil-soluble nano-composite copolymer was prepared by solution radical polymerization.Infrared spectroscopy,thermogravimetric analysis（TGA）and scanning electron microscopy（SEM）were used to characterize it.The effects of monomer feeding ratio,modified Si O₂ dosage,polymerization temperature,reaction time,initiator mass fraction,viscosity reducer dosage,temperature and shear rate on viscosity reduction rate were investigated by single factor test.The experimental results show that at 50℃,10 s-1 test conditions,when the monomer feeding ratio of octadecyl acrylate,4-vinylpyridine and acrylamide is 4:2:1,the additive amount of modified Si O₂ is 20%of the mass of the total reaction monomer,the polymerization temperature is 70℃,the reaction time is 6h,and the initiator concentration is 1.2%,the prepared nano-silica composite viscosity reducer has the best viscosity reduction effect on Shengli Chenping heavy oil.When the dosage of viscosity reducer is 700 mg/kg,the apparent viscosity reduction rate is 69.1%and the net viscosity reduction rate is 34.0%.The viscosity reduction ability of the viscosity reducer is better than that of nano Si O₂,commercially available viscosity reducer EVA and ternary oil soluble viscosity reducer.The viscosity reduction effect of the viscosity reducer on Shengli GD2 heavy oil is better than that of Shengli Chenping heavy oil,and the net viscosity reduction rate can reach 38.4%.It shows good effect of reducing viscosity.Finally,by comparing SEM images of asphaltene,X-ray diffraction analysis of asphaltene,asphaltene particle size change,morphology analysis、microstructure properties and viscoelasticity change of heavy oil system without and with adding nano-silica composite viscosity reducer were compared,the viscosity reduction mechanism of nano-silica composite material was discussed.A possible viscosity reduction mechanism model of nano-silica composite viscosity reducer was proposed.