Development And Performance Evaluation Of Temperature And Salt Resistant Polymer Microspheres

Polymer microspheres,as a high-performance deep profile control agent,are widely used in the treatment of water control and oil stabilization in the middle and later stages of oilfield water injection development.Due to the influence of divalent ions such as calcium and magnesium and various impurities in the reinjected water,as well as the high temperature of the reservoir,the development of the North China Oilfield is constrained.The existing microsphere particle water plugging agent has poor long-term stability,limited sealing ability,and urgently needs to improve the profile control effect.Therefore,it is crucial to design and synthesize polymer microspheres with good temperature and salt resistance.In this paper,acrylamide(AM),acrylic acid(AA)and 2-acrylamide-2-methylpropane sulfonic acid(AMPS)were used as polymerization monomers to prepare nanoscale polymer microspheres by inverse micro emulsion method.The reaction stability,monomer conversion rate and average particle size distribution of microspheres were comprehensively evaluated,and the optimal synthesis parameters were obtained at the content of compound emulsifier5wt%,Span80/Tween80 mass ratio 3:1,oil-water mass ratio 2:1 Under the conditions of a crosslinking agent dosage of 0.15wt%,MBA: PEGDA mass ratio of 1:1,polymerization temperature of 40 ℃,and stirring speed of 400 r · min-1,nanoscale polymer microspheres with regular morphology,concentrated particle size,and high yield were obtained.Characterize the appearance,morphology,and structural composition of polymer microspheres through optical microscopy,scanning electron microscopy,infrared spectroscopy,and evaluate the temperature resistance,salt resistance,and swelling properties of the microspheres to verify the feasibility of deep profile control and flooding of the microspheres.The experimental results show that the prepared microspheres with an average particle size of around 400 nm have good sphericity,temperature resistance,and salt resistance.Under high mineralization conditions,the expansion rate can reach 4.17 times,and the microspheres do not undergo large-scale hydrolysis under long-term aging,which meets the application requirements.The sealing and migration experiments indicate that polymer microspheres have good sealing properties and deep migration capabilities.The optimization results of injection parameters indicate that the higher the injection concentration and injection amount,the better the microsphere solution.It is necessary to consider the development cost and the improvement effect of sealing rate.When the displacement flow rate is 1.0m L/min,the microsphere dispersion is the best,with a sealing rate of 80.2%,and the best sealing effect is achieved within 7-15 days of swelling time.The oil displacement experiment shows that after injecting polymer microspheres,the average water content decreases by 23.4%,and the permeability difference is at 5.08.The best effect of oil displacement control is achieved,with a recovery rate increase of 21.01% for low permeability reservoirs,which is 7.53 times that of high permeability reservoirs.Polymer microspheres can play a good role in profile control and displacement in heterogeneous models,with permeability differences ranging from 2 to 7.Polymer microspheres have a good sealing effect on high permeability layers,expanding the swept volume,and allowing the remaining oil in low permeability layers to be utilized.