The Lubricity of Amphiphilic Carbon Dots in Silicate Drilling Fluids
Silicate drilling fluids have strong inhibitive capacity and good environment protection property,but their poor lubricity limits their application.In screening good lubricating agents for silicate drilling fluids,extreme pressure(EP)lubrication tester is used to measure the coefficient of friction of silicate drilling fluid samples containing amphiphilic carbon dots and polyoxyethylene surfactant.The best lubricating agent selected is then tested with total organic carbon analyzer,dynamic light scattering tester and contact angle tester to analyze its mechanisms of lubrication.The test results show that the amphiphilic cardon dots have excellent lubricity and high temperature stability.A 5％sodium silicate(Na2SiO3)water solution treated has EP coefficient of friction of around 0.500.The solution is then treated with 0.3％amphiphilic carbon dots(C12-CDs),and the EP coefficient of friction is reduced to 0.065.After hot rolling the C12-CDs treated Na2SiO3 solution at 110℃ for 16 h,the EP coefficient of friction of the solution is further reduced to 0.063,that is,the EP coefficient of friction of the Na2SiO3 solution is reduced by 87.52％.On the other hand,the polyoxyethylene surfactant shows no effect on the lubricity of the Na2SiO3 solution.Further study shows that C12-CDs has excellent adsorption performance on the surface of the quartz sands,the surface tension of a C12-CDs solution(c=100 mg/L)increases from 44.81 mN/m before the adsorption process to 64.03 mN/m after the adsorption process,the adsorption capacity is 89.23 mg/L.Particle size analysis shows that the C12-CDs can effectively reduce the particle sizes of the Na2SiO3 solution;the average particle size of the Na2SiO3 solution is reduced from 514 nm to 63.2 nm.The multi-hydroxy structure and the long hydrophobic chain on the surface of the carbon nuclei can improve the adsorption of the amphiphilic carbon dots on the surfaces of the drill string,the borehole walls and the silicate aggregates.The amphiphilic carbon dots as a good lubricating agent have good compatibility with silicate drilling fluids.Field application shows that C12-CDs can reduce the coefficient of friction of silicate drilling fluids by 86.34％,and are thus a good lubricating agent for silicate drilling fluids.
Amphiphilic carbon dotsSilicate drilling fluidCoefficient of frictionMechanism of lubrication
万方数据
维普
