Synthesis And Performance Study Of Amphiphilic Microsphere Profile Control Agent

Polymer microsphere profile control is a new profile control technology developed on the basis of cross-linked polymer profile control in recent years.Both indoor research and field tests show that polymer microspheres have broad application prospects in the field of deep profile control of low permeability reservoirs.However,the existing polymer microspheres for profile control have high water swelling rate and large water swelling ratio,and not only have large resistance into the deep part of the reservoir,but also plugging ability and plugging durability of the channeling path in the deep part of the reservoir greatly reduced after water swelling.In addition,the microspheres are produced by the inverse emulsion method,and a large amount of organic solvent and oil-soluble emulsifier are required in the preparation process,so that the production cost of the microspheres is high,and it is difficult to promote the application in a large area.In view of the above problems,the amphiphilic cross-linked polymer microspheres were prepared by emulsion polymerization.On the one hand,the production cost was greatly reduced.On the other hand,owing to the amphipathy of microspheres,the water swelling rate and water swelling ratio of microspheres were effectively controlled.Through the study of the basic conditions for the preparation of amphiphilic microspheres,the best emulsifier for preparing microspheres was AES.The mass ratio of AM to St was controlled in the range of 1.5:18.5 to 3:17 to prepare amphiphilic microspheres.The microsphere was characterized by infrared and transmission electron microscopy.The reaction product was the microspheres obtained by copolymerization of AM,MBA and St monomers,and the microsphere had a regular spherical shape.By studying the effects of various reaction conditions on the preparation of amphiphilic microspheres,it was concluded that only regular spherical microspheres can be prepared by controlling the concentration of MBA no more than 18.5 g/L;the mass ratio of AM to St and the concentration of MBA had great influence on the particle size of microspheres.the concentration of AES,the concentration of initiator and temperature had little effect on the particle size of the microspheres.From the viewpoint of yield,the concentration of APS and reaction temperature had the greatest influence on the yield of microspheres.The concentration of AES,AM/St and the concentration of MBA had little effect on the yield of microspheres,and the optimal concentration of APS was 2.50 g/L,the optimum reaction temperature was 75?,under which the yield of the microspheres can reach more than 90%.The synthesis kinetics of amphiphilic microspheres showed that the reaction rate of the emulsion polymerization of cross-linked polyacrylamide-styrene increased with the dosage of AES,the total dosage of AM and St monomers,the dosage of APS and temperature.The kinetic relationship of cross-linking copolymerization of AM to St can be expressed as Rp?[I]0.43·[M]2.61·[AES]0.98.The apparent activation energy(Ea)of the system was 87.42 kJ/mol.According to the performance evaluation of amphiphilic microspheres,Ca2+had the greatest influcnce on the suspension and dispersibility of microspheres at 25?,followed by Mg2+,while Na+ did not affect the suspension and dispersibility of microspheres.The water swelling ratio of microspheres increased with the increasing of temperature and time.The microspheres tended to be stable after swelling for 4 days at 25? and tended to be stable after swelling for 22 days at 60? and 80?.The initial water swelling rate of the microspheres was faster,and the water swelling rate of the microspheres gradually decreased with time.Under reservoir conditions,the dispersion coalescence time of the microspheres was shortened with the increasing of the concentration of Ca2+and Mg2+and temperature.Ca2+ had the greatest influence on the dispersion coalescence behavior of microspheres at 60? and 80?,followed by Mg2+,while Na+had no effect.The results of core flooding experiments showed that the microspheres can smoothly enter the core with the permeability of 20 mD to 50 mD to block the large pore throat,and the plugging rate can reach more than 80%.The optimal injection concentration of the microspheres was 3000 mg/L,and the optimal injection volume was 1 PV.The amphiphilic microspheres had better injectability,higher blocking strength and better oil recovery than polyacrylamide microspheres under the conditions of optimum injection concentration and volume.