Synthesis And Evaluation Of Lubricating Additives For Water-Based Drilling Fluid In Horizontal Section Of Shale Gas

The design and development of high performance lubricant treatment agent is one of the key problems limiting the rapid drilling of water-based drilling fluid in shale reservoir.The traditional lubricant design is mainly based on the liquid lubrication theory of oil,but neglects the boundary bearing and lubrication effect of drilling fluid solid phase in the extreme pressure confined space between drilling tool and borehole wall.In order to improve the lubricity of water-based drilling fluid and strengthen the stability of lubricant molecular structure,based on the previous research on water-based drilling fluid lubricant,this study combined with Stribeck curve to analyze the boundary lubrication behavior of drilling process,and carried out the basic research on the application of hyper-branched polymer lubricant additive for water-based drilling fluid with hyper-branched polymer as lubricant additive.Hyper-branched polymer PMA-EDA was synthesized with ethylenediamine and methyl acrylate as monomers by divergent method.Secondly,the structures of synthetic polymers were characterized by infrared spectroscopy,nuclear magnetic resonance and thermal gravimetric analyzer.Then,according to the synthesized PMA-EDA product,the lubrication improvement effect of it as a lubricating additive was evaluated,and combined with the key treatment agent to study the water-based drilling fluid lubrication system,indoor evaluation of the basic application performance of the lubricating additive PMA-EDA.Finally,the key components were screened and the main components of the macro-lubricating coating were studied.Through the adsorption experiments of hyper-branched polymer and bentonite,the model theory of boundary lubricating film formation enhanced by hyper-branched molecule was proposed.The main conclusions are as follows:(1)G2.5 hyper-branched polymer PMA-EDA was synthesized iteratively from the initial half-generation and whole-generation products by grafting methyl acrylate with ethylenediamine as core;(2)Infrared spectroscopy and nuclear magnetic resonance indicated that the synthesized product had the target product of hyper-branched configuration.Meanwhile,thermogravimetric analysis showed that the thermal decomposition temperature of G2.5 PMA-EDA product was up to 225℃,showing good temperature resistance.(3)In the base pulp evaluation experiment,10%G2.5 PMA-EDA can significantly reduce the lubrication coefficient,and it has a certain rheological improvement effect;The lubricating system was constructed by selecting the key treating agent,and it was shown that the lubricating additive PMA-EDA has excellent temperature and salt resistance in addition to reducing friction and drag.(4)According to the research system,laboratory experiments show that solid lubricant and bentonite are the main components of macroscopic lubrication coating.The results of bentonite experiments,such as scanning electron microscopy,thermogravimetric analysis and infrared spectroscopy,show that PMA-EDA can be adsorbed on the surface of bentonite particles,enhance the connection degree between particles,and improve the contact mode between drilling tools and mud cake.At the same time,the lubricating additive PMA-EDA also provides additional ester group and hydroxyl group adsorption on the surface,promoting the formation of polymer layer on the surface,and promoting the formation of boundary lubrication film with a certain strength.