Research On Oil Displacement Effect Of Modified Nano-SiO₂ Hyperbranched Polymer In Low Permeability Reservoir

At present,low permeability reservoirs still account for a large proportion of low permeability reservoirs in China,even more than 40%.However,due to technical constraints,the recovery rate is only about 20%.Therefore,low permeability reservoirs have great potential in production.Chemical flooding is the three stages of oil recovery that must be experienced in the middle and late stages of waterflooding development.Polymer flooding has become one of the most important oil displacement technologies in the process of"three recovery".However,in low permeability reservoirs,because of its own characteristics and relatively small pore roar and complex structure,the injection of polyacrylamide（HPAM）in medium and low permeability reservoirs will be"difficult to inject,low recovery"and so on.A modified nano-SiO2 hyperbranched polyacrylamide was synthesized according to the characteristics of low permeability reservoirs.The structure of the polymer was rationalized,and nano-SiO2 properties were also developed.The feasibility of injection was proved in the experiment.At the same time,one-dimensional sand-filled pipe flooding simulation experiment and three-dimensional simulation experiment were carried out,which can be summarized as follows:1.A new type of hyperbranched polyacrylamide was synthesized,and its synthesizability was proved by infrared spectroscopy,and its shear resistance and viscosity were determined.The amount of hydroxyl groups on the surface of nano-SiO₂was calculated by NaOH-HCl titration method to be 1.1611 mmol/L.Finally,nano-SiO₂ was modified by Hyperbranched polyacrylamide with a modification rate of54.7%,which can play a role in hyperbranched polypropylene.The effect of olefin amide can also play the role of nano-SiO₂,and the molecular weight is（1.4±0.1）×10⁷ g/mol,and the ion cyclotron radius is 114±20nm,which meets the conditions of injection into low permeability reservoirs.2.In the experiment of one-dimensional sand-filled pipe,the highest recovery rate is 23.98%when the hot water flooding temperature is 70℃,but there is no significant improvement coMPared with 60℃.So the follow-up experiments are carried out on the basis of 60℃.When the concentration of nano-SiO₂ is 0.6wt%,the effect is the best,and the recovery rate is increased by 20.5%.Finally,the modified nano-SiO₂ is used for displacement.Under the condition of hyperbranched polyacrylamide,when the concentration of solution is 0.2%,the displacement effect is the best,and the recovery rate can be increased by 23.5%.3.In the three-dimensional displacement experiment,the same temperature of hot water displacement is the best,at 25.13%and nano-SiO₂ dispersion displacement is also the best when the concentration is 0.6wt%.The recovery rate can be increased by21.05%.In the case of using modified nano-SiO₂ hyperbranched polyacrylamide displacement,the displacement effect is the best when the concentration of solution is0.2%.The recovery rate can be increased by 24.03%.It is basically consistent with the one-dimensional experimental process.