Effect Of Nano-silica On Properties Of Conventional Density Oil Well Cement Slurry

Cementing stone is a kind of high brittle,low toughness,porous and high alkaline material.It is easily damaged by downhole stress and acid fluid corrosion and loses its supporting casing.Therefore,nano silica is added to the cement to improve the anti damage ability of the cement stone.In this paper,the effect of nano silica on the properties of cement slurry and the mechanism of action are studied,providing more theoretical basis for its application in practical production.In this paper,the effects of nano silica on rheology,stability,thickening time and gas channeling resistance of cement slurry were studied.The results show that the stability and anti gas channeling ability of the cement slurry are modified by nano silica,and the thickening time of the cement slurry is reduced,the initial consistency increases and the convective denaturation has a certain influence.But in a reasonable mixing range,it can meet the needs of the construction.The smaller the size of the nano silica particles,the more obvious effect is.The effect of nano silica on the mechanical properties of cement stone is reflected by measuring the compressive strength,tensile strength and strength development parameters of the cement stone.The result is that nano silica can improve the mechanical properties of the cement stone and improve the toughness of the cement stone.The porosity is reduced and the pore structure is improved.The smaller the particle size of nano silica is,the better the mechanical properties and pore structure of cement paste will be.The improvement effect of nano silica on the properties of cement stone is verified by a high temperature and high pressure cement ring integrity tester.The results show that the integrity of the cement can be improved by nano silica.By measuring the strength of the cement before and after carbon dioxide corrosion and the corrosion depth to reflect the change of corrosion conditions,the results show that the nano silica can improve the corrosion resistance of the cement stone.The changes of the phase and Micromorphology of the cement stone after corrosion are studied by XRD and SEM.In order to close the actual working conditions of the downhole cement ring,the coupling of stress and carbon dioxide corrosion is used in cement stone.When loading different stresses,the degree of corrosion of cement stone is different.After adding nano silica,the improvement effect of stress corrosion corrosion of cement stone is obvious.The hydration process is reflected by the change of electrical conductivity in the hydration process.Nano silica can accelerate hydration and shorten the hydration time.Through XRD,TG and SEM,the morphology of the hydrated products and the hydrated products are analyzed by nano silica.The nano silica can be used to hydrate the cement and the hydration of cement.The product has a "volcanic ash reaction",which reduces the alkalinity of the cement stone,and the nano silica particle size is small,so it is used as a nuclear agent in hydration,accelerating the nucleation crystallization of the hydration products of cement,reducing the size of the hydration products and making the cement more compact.