The Synthesis Of Nano-clay And The Application Of Drilling Fluid System

During the exploration of deep and ultra-deep wells in oil and gas fields,high temperature and pressure and other harsh conditions bring great challenges to the application of drilling fluid systems.In the past 20 years,polymers of nanoparticles and functionalized monomers have been used as treatment agents for drilling fluids to enhance the performance of drilling fluids under high temperature and pressure conditions and to meet engineering needs.In this paper,intercalators and nano-modifiers were preferentially selected to form a composite modifier.The optimal synthesis conditions were determined using single factor condition analysis and response surface analysis:the amount of initiator was 0.57wt%,the p H value of the system was 7,and the reaction temperature was 70.9°C.The final response value of rock-carrying capacity（YP/PV）was 0.178,the filtration loss（FL）was 9.59 m L,and the coefficient of lubrication（Co F）was 0.25.To investigate the physical and chemical characteristics of DMC-MAA-SiO₂ nano-modifier and its modified clay drilling fluid,it was characterized and analyzed.The molecular structure composition,chemical composition,thermal stability,microscopic morphology and particle size of the nano-modifier were characterized,and the results showed that the chemical composition and molecular structure characteristics of the nano-modifier compounded the expected requirements,with superior temperature resistance and spherical particle structure.The analysis of clay layer spacing and microscopic morphology of the nano-modified clay drilling fluid showed that the modified clay crystalline layer spacing was expanded,and the nano-clay composite structure was formed at the same time.In order to study the mechanism of the interaction between the composite modifier and the clay layer,the particle size distribution of the drilling fluid and the microscopic morphology of the mud cake were analyzed respectively.The optimal addition of nano-modifier DMC-MAA-SiO₂was determined to be 0.5%～0.75%.The rheological properties of the drilling fluid before and after aging were not significantly different,and the filtration loss after aging was all around 10 m L,which decreased by about50%～65%compared with that before the modifier was added,and the decrease of lubrication coefficient reached 25%～30%.The composite clay wrapping structure improves the dispersion of the clay and will form a dense filter cake in the process of filtration loss,while the formation of the nanostructure reduces the sliding contact between the drilling fluid clay particles and the well wall and enhances the lubrication capacity.The composite modified clay can be tried to replace the commonly used clay in current drilling fluids and used under high temperature conditions.Thus it can improve the rheological and filtration loss performance of drilling fluids.