Application Of Alkyl Glycoside Compounded System In Viscosity Reduction Of Heavy Oil Emulsifying

With the continuous consumption of conventional crude oil,the abundant unconventional crude oil shows great market potential and application prospect.Heavy oil is a kind of unconventional crude oil resources.The high content of resin and asphaltene leads to high viscosity and poor liquidity,which is an important reason restricting heavy oil production.At present,the main methods for viscosity reduction of heavy oil at home and abroad are include heating viscosity reduction,dilute viscosity reduction,emulsification viscosity reduction,catalytic modification and ultrasonic viscosity reduction,etc.Emulsification has the advantages of low cost,simple process,obvious effect and broad application prospect.Emulsifying viscosity reduction method is emulsified heavy oil by injecting surfactant aqueous solution to reduce viscosity of heavy oil.The surfactant contains hydrophobic groups and hydrophilic groups at the same time,which can be adsorbed on the oil-water interface,significantly reducing the oil-water interfacial tension,so that the oil phase can be stably dispersed in the water phase,forming O/W emulsion.Conventional emulsification requires external equipment to provide the energy required for emulsification to form O/W emulsion.However,in actual field production,the energy required for emulsification cannot be obtained through external equipment,which often leads to poor emulsification viscosity reduction effect.Self-emulsification is a method of self-emulsifying to form an emulsion when an immiscible liquid phase comes into contact without or at a low level(such as light stirring and shaking)with additional energy from the outside.Surfactants reduce the interfacial tension of oil and water,and reduce the free energy required for emulsification.With less extra energy,the oil and water system can be self-emulsified.Alkyl glycoside is a surfactant with strong interfacial activity,which can reduce the interfacial tension of oil and water to a very low range,and has the potential to achieve self-emulsification of heavy oil.However,the stabilization ability of alkyl glycoside emulsion alone is poor,so it is necessary to use alkyl glycoside and other cooperative stabilizer to improve the stability of heavy oil emulsion.The main research contents are as follows:(1)In Chapter 2,the combination system of alkyl glycosides and other surfactants was used to emulsify heavy oil under weak shear condition,and the APG and D-OA combination system with good emulsifying effect was selected,the surfactant concentration was 1.0 wt%,and the compound ratio was 4:6.The viscosity of heavy oil emulsion was 110.6 mPa·s when the emulsification temperature was 80℃,and the water dissolution rate was 10%after standing at room temperature for 2 h.The surfactant aqueous solution can peel the heavy oil from the surface of quartz sheet with different wettability.The stability analysis data show that the stability of the composite system is better than that of APG alone.The interfacial tension of APG,D-OA and two surfactants at different temperatures showed that the stability of emulsion was not positively correlated with the interfacial tension.The surface tension and critical micellar concentration of the two surfactants were measured by surface tensiometer,and the interaction parameters were calculated.It was proved that the absolute value of the interaction parameters was the largest and the synergistic effect was the strongest,the emulsion interface film had the highest viscoelasticity and the emulsion stability was the best when the complex ratio was 4:6.(2)In the third chapter,three kinds of nanofluids were synthesized by the combination of alkyl glycoside(APG)and MgO,Al2O3 and SiO2 nanoparticles,which were applied to emulsification and viscosity reduction of heavy oil.Fourier transform infrared spectroscopy proved that APG adsorbed on nanoparticles and improved the interfacial activity of nanoparticles.The Zeta potential proves that the nanofluid has certain stability.APG-SiO2 nanofluid was selected from the three kinds of nanofluids as viscosity reducing agent.The viscosity reducing agent concentration was 0.5 wt%APG+0.07 wt%SiO2.The nano-SiO2 particles were 30 nm hydrophilic unmodified particles,and the emulsification temperature was 80℃.Standing at room temperature for 2 h,the water dissolution rate was 10%.The water phase circulation experiment proves that the water phase of heavy oil emulsion can be reused after demulsification.The stability analysis data show that the stability of the thick oil emulsion prepared by nano fluid is better than that of the thick oil emulsion stabilized by APG alone.The interfacial viscoelastic experiments show that the emulsion containing APG,SiO2 and asphaltene has the largest interfacial viscoelastic modulus,enhanced the strength of the interfacial film and improved the stability of the emulsion.The static oil washing rate of APGSiO2 nanofluid was 96.85%by static oil washing experiment.The recovery rate of NaCl brine and APG-SiO2 nanofluid was 17.55%and 35.02%respectively.