Synthesis Of Nano-SiO 2 Grafted Hyperbranched Polymer And Its Application In Drilling Fluids

Micro-nano cracks exist common in the shale formation.If there is no effective plugging during the drilling process,the drilling fluid will penetrate into the deep formation directly through the micro-cracks,resulting in the instability of the borehole.Conventional micro-sized plugging agents are helpless to plugging small size cracks in shale formation.It's necessary to use nano-sized plugging materials to improve the sealing performance of the drilling fluid,which may solve the technical problem that shale wall is unstable.Nano-silica's small size and high surface energy,integrated hyperbranched polymer's advantages like low viscosity,high dispersion performance,highly branched structure and a large number of highly active end groups,can be the important method to blocking to the micro pores snd cracks on the shale.In this paper,the hyperbranched polyamides were grafted onto the surface of nano-SiO2 by "grafting from" method with methyl acrylate(MA)and ethylenediamine(EDA)as monomers.The product(HB-PA-S)was gained by modifying the end group into sulfonic acid group.The structure of the synthesized product was tested by FTIR,TGA,DLS,SEM methods and it proved to be the target product.The product resistant to temperature 350 ?,have the median diameter of 413.1nm,and got the good dispersion character,even contain many nan-particles.The sealing performance of HB-PA-S was evaluated by HTHP static water loss method,HTHP filter filtration,core permeability method,pressure transfer experiment and mud cake simulation evaluation method.The result showed that better than the nano-SiO2,the product has a good sealing effect and can be used as a blocking agent.The plugging agents which have good plugging effect was selected through the mud cake simulation evaluation method.Combine these plugging agents with the developed main agent(HB-PA-S),the best plugging agent combination was obtained.The combination is 3%NR-1+ 3%HB-PA-S + 2%ultrafine CaC03.The drilling fluid formulation is preferred,and a basic system with good performance is built.By adding the composite sealing agent,the drilling fluid evaluation system is obtained.The formulation is 4%Bentonite + 3%JHJS-200 + 0.3%FA367 + 2%JA-11 + 1.5%FT-342+ 2%RH220 + 0.1%XC + 0.5%SM-1 + 3%HB-PA-S + 3%NR-1 + 2%CaC03.The systems have good rheological and water loss property,not only have superior sealing performance and can inhibit clay hydration,but also can improve lubricity and anti-pollution performance,which can meet all the requirements of the shale water-based drilling fluid completly.