Preparation And Evaluation Of Hydrogel Microspheres Used In Oilfield

Using oleic acid/Span20/OP10 as compound emulsifier and diesel oil as continuous phase,nonion polyacrylamide hydrogel microspheres are synthesized by inverse microemulsion polymerization.the optimal ratio of the compound emulsifier is determined according to area contour diagram and pseudoternary phase diagram,and the mass ratio of oleic acid to Span20 to OP10 is 41:31:28.at the optimal polymerization point,the mass fractions of oil phase,emulsifier phase and water phase are 34.62%,15.38%and 50.00% separately.the microemulsions before and after the polymerization are characterized repectively by freeze-etching transmission electronmicroscope,scanning electron microscope and dynamic light scattering,it is shown that there is a little difference between the sizes of them and they are all nanometer-level.The optimum reaction conditions determined through mono-factor method are that the reaction temperature is 40℃,the mass fraction of initiator to the aqueous solution is 0.12%,the mass fraction of MBA to monomer is 0.005%.adjusting the quantity of PEEDS can delay particle expansion.The hydrogel microspheres exist positive cooperative effect with most oil displacement agents especially to alkali,which can reach ultra-low interfacial tension and could be used for deep profile control(or oil displacement). core displacement test shows that the injection of hydrogel microspheres could limitely enhance recovery after tertiary oil recovery but the experimental method has yet to be further explored.In order to expand application,five kinds of cationic polyacrylamide hydrogel microspheres with different cationic degree(5%,10%,15%,20%,25%) are synthesized using Span80-tween60 emulsion system.IR spectroscopy verifie the existence of cationic chains for purified products.The optimum reaction conditions with CD as evaluation criteria are found by orthogonal experiment as follows:mass fraction of MBA to aqueous solution 0.0025%,mass fraction of PEEDS to aqueous solution 5.7%,mass fraction of APS to aqueous solution 0.3%,reaction temperature 50℃.Flocculation experiment and vscosity test show that cationic polyacrylamide hydrogel microspheres could be used as flocculant and polymer tackifier.