Preparation Of Poly(acrylamide-divinylbenzene) Microspheres And Their Use In Drilling Fluids

With the effect of different pressure in the drilling process could cause fluid loss, which called the drilling fluid filtration, the large filtration amount would cause a shale swelling and hole collapse, made the wall of well unstable. As a kind of important drilling fluid additives, fluid loss agent played an important role in maintaining the performance of drilling fluid stable, drilling safely and efficiently. With the rapid development of polymer spherical particles, its unique spherical structure and characteristics of small size made it receive more and more attention in the application of the drilling fluid additives.The method of dispersion polymerization had been used in this paper, poly (acrylamide-divinyl benzene) microspheres was prepared in alcohols solvent by using acrylamide as monomer, divinyl benzene as crosslinking agent; reaction temperature, reaction time, stirring speed, amount of initiator and monomer ratio, dispersing agent and amount of dispersant were filtered through production rate, particle size and micro structure, the final reaction conditions was determined as follows:reaction temperature was 70℃, the reaction time was 7h, amount of initiator was 4% of the total quality of monomer, monomer ratio of DVB:AM was 1:2, amoun of dispersant FS wasl.5%; microspheres obtained under this condition had a higheproduction rate, uniform particle size and homogeneous dispersion; could wetting in both water and oil, had a certain hydrophilic lipophilic property, could be used as an additive in the oil-base drilling fluid and water base drilling fluid.The poly (acrylamide-divinyl benzene) microspheres as additives was used in the oil-base drilling fluid with water base drilling fluid. The results showed that:Poly (acrylamide-divinyl benzene) microspheres showed a good fluid loss resistance and temperature tolerance in oil-base drilling fluid. Could improve the value of demulsification voltage, made the stability of drilling fluid enhanced, improved shear and dynamic plastic ratio of drilling fluid, at the same time reduced the amount of filtration; with the contrast with fluid loss agent oxidation asphalt commonly used and nano calcium carbonate, microspheres also showed good resistance to high temperature and fluid loss, the high temperature and high pressure filtration volume of drilling fluid with adding amount of 0.5% microspheres, density drilling increasing to 1.6 g/cm3 was 10 mL after aging at 200℃, adding the amount of 2% oxidized asphalt and nano calcium carbonatewas respectively 15 mL,24 mL,smaller amount of drilling fluid filtration was obtained when the added amount is far less than the oxidation asphalt and nano calcium carbonate; plugging rate was more than 50% after high temperature, thermogravimetric analysis also reflected the microspheres had a higher temperature resistance than oxidation asphalt and nano calcium carbonate; at the same time, microspheres haa strong sealing performance in drilling fluid, sealing performance was far better than oxidation asphalt and nano calcium carbonate after high temperature, the microstructure of the mud cake also verified this conclusion.Microspheres as addition agent showed good temperature resistance, filtration reducing property and unctuosity. The adding of microspheres had little effect on rheological property of drilling fluid, the amount of 1% microspheres is less than other fluid loss agent in the drilling fluid, reduced the drilling fluid filtration, improved the lubricity; decreasing rate of friction reached more than 55%, spherical structure of microspheres made it can reduce the friction coefficient of drilling fluid effectively, and remained lubricating spherical structure after high temperature; these properties of microspheres in drilling fluid also manifested after aggravating; with the lubrication time growing, solid lubrication film formed by microspheres on metal surface made the lubrication of drilling fluid not reduce.