Study On Interfacial Adsorption Characteristics Of Nanoparticles

Due to the characteristics of small pore throat and strong capillarity in low permeability reservoirs,nanoparticles with small particle size and environmental protection are gradually applied as chemical substitutes in the research of improving crude oil recovery.However,nanoparticles have strong adsorption capacity in porous media,and exploring the adsorption of nanoparticles in porous media is very important in oilfield development.This paper makes a systematic study on the adsorption of nanoparticles at solid-liquid interface and oil-water interface in order to provide theoretical guidance for the application of nano-flooding technology to enhance oil recovery in low permeability reservoirs.By changing the parameters of nanoparticle type,particle size,ambient temperature,metal ion concentration and the like,measuring the adsorption capacity of nanoparticles at the solid-liquid and oil-water interfaces,this paper revealed the adsorption characteristics and influence laws of nanoparticles at the oil-water interface and the adsorption-desorption laws of nanoparticles at the solid-liquid interface.By using a one-dimensional physical core model,studying on the adsorption-desorption behavior of nanoparticles in porous media and evaluating the oil displacement effect of nano-flooding in low permeability cores.The experimental results show that the amphiphilic nano SiO₂ particles with an average particle size of 50nm and a concentration of 0.1wt%have the largest adsorption capacity at the oil-water interface,with better salt resistance and temperature resistance,and the adsorption capacity increases with the increase of temperature and the decrease of particle size.The adsorption law of different types of nano SiO₂ particles on the solid surface of rock conforms to Langmuir isothermal adsorption model.The adsorption amount of amphiphilic nanoparticles is larger,and increases with the decreases of ambient temperature,the decreases of particle size and the increase of the complexity of mineral composition on the solid surface.Adsorption and retention of nanoparticles in porous media are affected by displacement speed,core oil content and permeability.It is easier for nanoparticles to reach the retention saturation state in porous media and harder to desorb,with the higher the displacement speed and the higher the oil saturation.In the range of core permeability of 4×10^-3～23×10^-3μm²,the recovery efficiency of nanofluid flooding is better and increases with the decrease of permeability.