Development And Evaluation Of Lubricating Microspheres By Inverse Emulsion Polymerization

Flooding microsphere is a nano-micron absorbent material. Its small size, large number and deformable characteristics endow it unique advantages in deep flooding technique for low permeability and heterogeneous reservoir, more and more applications had been carried out in the field. The present polymer microsphere flooding existed large dosage emulsifier, low oil displacement efficiency and poor performance of anti-high temperature and salinity shortage.This paper research focused on microspheres stability and low interfacial tension emulsion system, acquired knowledge and results were as follows:1. selecting acrylamide (AM),2-acrylamido-2-methylpropane sulfonic acid (AMPS) and N-vinyl pyrrolidone (NVP) as monomers; conductivity, oil/water interfacial tension, viscosity and emulsion stability index as indicator, studied emulsifier type,ratio on the influence of emulsion stability. We finally choosed emulsifier type and quality ratio were Span80/Tween60/OA=62/18/20. Inverse emulsion compositions were as follows:51.6%water phase, white oil of41.2%and7.2%emulsifier, stirring rate850r/min.2. Using univariate method investigated initiator type/dosage, reaction temperature, emulsifier dosage and amount of cross-linking agent on the influence of monomer conversion and particle size. Combined orthogonal experiment results, the best polymerization conditions was determined:stirring rate350r/min, initiator V-50concentration of0.027%accounted for monomer, MBA concentration of0.05%, temperature50℃, the conversion was higher than80percents.3. We both used polarized light microscopy, laser particle size analyzer and scanning electron microscopy evaluating the morphology of the microspheres. The average diameters of the microspheres powder were3μm with good spherical shape, particle sizes distribution of4.08μm to27.93μm in the water. Microspheres had good expansion ability, stability and strength. When salinity was higher than10000mg/L, expansion multiple was no longer maintained at about2times. In90℃,20×104mg/L salinity formation water, microspheres can maintain spherical structure for120days. According the amount of oleic acid in Span80/Tween60/OA system, an equimolar amount of NaOH was add which made the performance of lower interfacial tension better than Span80/Tween60system, and the DK1oil/water interfacial tension was reduced to10-2magnitude. Microspheres system with betaine, petroleum sulfonate or polymer complex had certain synergy.4. Physical simulation experiments showed that the microspheres can enter into cores with permeability more than262mD, when the core pore throat diameter/microspheres size ration was1.02, microspheres had best blocking/migration performance. It can migrate in the core exhibiting "wave pressure" variation feature. Microspheres can improve DK1oil recovery for18.54%after water flooding, and it also had good performance of profile control between the cores with permeability ratio of9.3.