Research On Nano-modified Cement Slurry Based On Close Packing Theory

In recent years,the theory of close packing has developed rapidly.With the rise of micro-nano materials,such as nano-silica and graphite oxide nano-sheets have many excellent physical and chemical properties,the close-packing theory,which is used to optimize cement slurry has wider application prospects.However,current cementing slurry technology still cannot meet the needs of some complex well cementing seal integrity.Based on the close packing theory,this paper explores the nano-materials suitable for cementing cement modification,and develops a nano-cement slurry system with excellent mechanical properties of cement slurry/cement stone,and analyzes its microstructure and micro-mechanical properties.First,the effects of closing packing on the performance of cement slurry were studied by experiments.The results show that the mechanical properties of cement stone are significantly improved by the close packing design,and the close packing design has a good effect on inhibiting the shrinkage of cement stone,controlling the cement water loss agent to improve the stability and rheology of cement slurry.Secondly,A single-doped carbon nanotube and graphite oxide cement slurry system was designed,as well as a hybrid nanomaterial cement slurry system mixed with graphite oxide and nano-silica.The results show that nano-materials can promote cement hydration to different degrees and decrease the volume of pores in cement stone and can improve the strengthening and toughening properties of cement stone.The effect of hybrid nano-materials on strengthening the mechanical properties of cement stone is better than that of single-doped graphite oxide and nano-silica cement stone.Finally,the microstructure and micro-mechanical properties of the nano-close cement slurry were analyzed by microscopic methods such as SEM,XRD,MIP and nanoindentation.The microstructure analysis shows that the microstructure of the cement stone doped with nano-materials is more compact,and the characteristics of the nano-materials can promote the hydration of cement,thereby generating more hydrated calcium silicate gel and improving the macro properties of cement stone.The analysis of micromechanical properties shows that the nano-materials can act as a nucleation template in the cement slurry,which promotes the hydration reaction of cement.Therefore,the low-density hydrated calcium silicate(LD CSH)gradually moving to HD CSH and UHD CSH conversion,which have higher mechanical properties.On the other hand,nano-materials can fill the pores of cement stone,which reduces the porosity and further improves the mechanical properties of cement stone.