The Synthesis And Evaluation Of Pre-gelled Particle Profile Control Agent

Most oil field in China have access to high water cut, and the oil recovery dropped significantly. One of the methods to increase recovery is to increase the sweep efficiency. Profile modification can make the injected water flow into low permeability reservoirs, then improve the sweep efficiency and increase recovery.Since oilfields in China have entered the late water flooding stage, conventional treatment has limited effect. The particle profile control and in-depth fluid diversion technique can improve the whole block, and the diameter of the profile control agents can be modified by the diameter of the formation, and having the characteristics of good flexibility, well economical efficiency. Therefore the study of particle profile control and in-depth fluid diversion technique is more and more important.A new tri-axial swellable water-plugging agent was developed which was synthesized by acrylic acid (AA), acrylamide (AM), bentonite and N,N-methylene-bis-acrylamide which swelled in water, and can be used to enhance the sweep efficiency of injecting water and improve the injection profile of the stratum to steady yield. Bentonite was used for a functional monomer to crosslinking copolymerize with the expensive monomer AA, which reduced the cost, strengthened the property and improved the combined properties of water-plugging agent.The tri-axial swellable water-plugging agent was synthesized by aqueous solution polymerization,which with acrylic acid, acrylamide and bentonite as start material, N,N-methylene-bis-acrylamide as crosslinking agent and potassium persulfate/sodium acid sulfite as initiator. The influence factors of absorbency properties synthesized by aqueous solution polymerization, such as the concentration of initiator and crosslinker, initial monomer concentration, reaction temperature, pH of system, ratio of monomers, and the amount of bentonite were investigated by the series of single factor tests. By orthogonal experiments, the optimum technological parameters were fixed. The concentration of initiator was 0.3%,crosslinker concentration was 0.05%;initial monomer concentration was 20%, ratio of monomers(AA/AM)was 3:1, the amount of bentonite was 10%, pH of system was 7.0, reaction temperature was 50℃.The results showed that the Pre-erosslinking particle swelled 700-900 times in water, It was stable under 80℃for 60d. In addition, the agent behave dwell in pliability, deformability as well as in injection. By the core flooding experiment, anti-washing capability, blocking rate and breakthrough pressure of core were investigated. The water shutoff agent have better performance of anti-washing capability, selection and high blocking rate. Washed by 50 PV water, blocking rate over 85%. Water-plugging efficiency was 95.12%, oil-plugging efficiency was 20.45% and the breakthrough pressure of core was 112.2MPa/m, which can modify the water profile well.