Preparation Of Magnetic Nanodemulsifiers And Their Demulsification Performances On Crude Oil Emulsion Containing Solid Particles

At present,most oil fields in China have gone into interim period or late period of development,tertiary oil recovery,quaternary oil recovery and acid fracturing technologies have been widely applied.The application of new technologies indeed improved the oil recovery factor,but followed by complex crude oil emulsions containing a large number of solid particles,which appeared in produced fluid and produced water treatment systems.These oil emulsions hoard in the intermediate transiton layer,hence seriously obstructed the oil production,leading to electric dehydrator field breakdown,dehydrated crude oil contains excessive amounts of water,the quality of treated water deteriorates and other problems.So,for the older oilfield,it is urgent to develop and apply some new efficient demulsification technologies to solve the demulsification problems encountered.In this study,the Daqing crude oil emulsions containing solid particles was analyzed firstly;then based on the interface adsorption characteristic of the solid particles,several magnetic demulsifiers were designed and prepared.For their magnetic property,the demulsification ability of demulsifier was enhanced,and the used magnetic demulsifiers can be recycled and reused,which will reduce the cost of oil production.The solid paticles in the oil emulsion were analyzed by SEM and XRD,the results show that the main components of the solid particles are inorganic compounds,such as calcite,quartz sand,plagioclase and so on;the calcite are the most particles in the produced fluid that has not been acidified,but for the produced fluid from acidizing operations,when mixed them with other production fluid,some new smaller solid particles will be formed,such as microcrystalline kaolinite and Fe S,which tend to adsorpt on the oil-water interface,prevent the droplets from coalescing,and the microparticle produced by the reaction is the main obstacle to separate oil and water efficiently.Magnetic block polyethers,magnetic polyamide-amine demulsifiers and their chemically modified derivatives were synthesized and characterized,and the demulsidication performances of magnetic demulsifiers were investigated.Firstly,superparamagnetic Fe₃O₄nanoparticles were synthesized by chemical precipitation method,and then take it as the core,magnetic block polyethers MBP5921-1 and MBP5921-2 were prepared by coupling grafting method;Secondly,the superparamagnetic Fe₃O₄ nanoclusters were synthesized by solvothermal method,and then take it as the core,the magnetic polyamide-amine demulsifier M-G_n-PAMAM was synthesized following ultrasonic-assisted“bottom-up”method;Thirdly,quaternary ammonium magnetic polyamide-amine demulsifier M-G_n-PAMAM-TMAC and amphoteric magnetic polyamide-amine demulsifier M-G_n-DPMA-S were further obtained by modification of M-G_n-PAMAM.The involved intermediates and the magnetic demulsifiers were all characterized by FT-IR,TEM,XRD,TGA and VSM.The demulsification properties of the magnetic demulsifiers were investigated and the field application test was carried out on a small skid-mounted equipment.According to the results of demulsification properties,the magnetic demulsification machnism was analyzed and discussed.The main results and conclusions are as follows:（1）The synthetic conditions of Fe₃O₄ nanoparticles by chemical precipitation and solvothermal methods were respectively determined.The preparation conditions for Fe₃O₄ magnetic nanoparticles using Fe Cl₃ and Fe Cl₂ as raw materials and NH₃·H₂O as precipitator were optimized.The synthesized superparamagnetic Fe₃O₄ nanoparticle was spherical with average diameter 8.49 nm.Particle size was negative correlation to stirring speed and ammonia concentration,and was positive correlation to reaction temperature.The preparation conditions for Fe₃O₄ nanoclusters by solvothermal method were also optimized,the prepared superparamagnetic Fe₃O₄ nanoclusters were spherical with average diameter 150 nm.Fe₃O₄ nanoclusters have superparamagnetic property,good water dispersion,and higher saturation magnetization than chemical precipitation method.It’s better to choose Fe₃O₄ nanoclusters as a modified substrate for organic macromolecular demulsifier.（2）Two kinds of magnetic demulsifiers,block polyether and polyamide-amine,were synthesized,and their demulsification performances on the O/W simulative emulsion were investigated.Firstly,using the Fe₃O₄ made by chemical precipitation method as magnetic core,KH-560and KH-550 as coupling agents,BP5921 as the grafted demulsifier,MBP5921-1 and MBP5921-2 were obtained respectively,demulsification performances of the magnetic demulsifiers were all better than that of BP9521,the magnetic field could enhance the demulsification effect of magnetic modified demulsifier indeed.Perhaps due to the introduction of one more silicon shell,the demulsification effect and magnetic induction intensity of MBP5921-1 are lower than those of MBP5921-2.Secondly,using the Fe₃O₄ nanoclusters made by solvothermal method as magnetic core,M-G_n-PAMAM was obtained by ultrasound-assisted"bottom-up"synthesis method.Compared with the coupling grafting method,ultrasound-assisted"bottom-up"synthesis method can greatly shorten the reaction time and improve the reaction efficiency,and the grafting rate of demulsifier is increased.M-G_n-PAMAM was used as raw material to prepare quaternary ammonium modified M-G_n-PAMAM-TMAC and amphoteric modified M-G_n-DMPA-S,respectively.Among all the magnetic polyamide-amine demulsifiers,the demulsification performances of the 2.0 generations were the best.（3）The field application test shows that the 2.0 generation amphoterization modified product M-G_2.0-DMPA-S has the best adaptability to the oilfield emulsion containing solid particles.For the oilfield O/W emulsion,the average OIW（oil content in oilfield water）can be decreased from 2752mg/L to 428mg/L after the treatment of M-G_2.0-DMPA-S demulsifier,and the the average WIO（water content in oil）can be decreased from 4.64%to 0.64%.At the same time,M-G_2.0-DMPA-S also shows excellent recyclable and reusable performance,and the dehydration rate of M-G_2.0-DMPA-S remains above 92.5%after 9 cycles,which has a good application prospect.