Experimental Studies On Multiple-injection System To Enhance Recovery Of Oil Field After Polymer Flooding

Polymer flooding has been large-scale carried out in eastern oil filed,enhanced oil recovery up to 10 %.But there are still underground about 50 percent of crude oil can not be exploited,It's necessary to take the measures to enhance oil recovery after polymer flooding. The main reason for limitation of polymer flooding is polymer channeling along the major channels (or high permeability bands) and invalidity of the water cycle,the utilization rate of polymer is very low,so crude oil is not effective displaced in low-to-moderate permeable formation. Based on this problem the issue evolved a set of enhanced oil recovery experimental studies after polymer flooding. Through inner laboratory study ,multiple-injection system of enhancing oil recovery after polymer flooding was optimized,ie gel microsphere,crosslinker,high efficiency oil displacing agent and behavior of three oil displacement agents was valuated,concrete experiments as follows:Positive ion gel microspheres was selected to block off the major channels through gel microspheres screening experiment; the laws of gel microspheres grain diameter was found when existing polymer and flowing in porous medium through swelling and shearing experiments. and the matched relations of gel microsphere grain diameter and formation permeability was found through the adaptation experiment of the gel microspheres grain diameter and formation permeability.Crosslinker was selected as profiling control agent to block off high-middle formation through gelling experiment and shearing and steady experiments ,and through filling crosslinker experiment after polymer flooding in distinct formations, the profiling and blocking laws of crosslinker was studied.High efficiency oil displacing agent was selected through interfacial tension force experiment,and the steady characters of oil displacing agent was verified under diversity environments. Through decreasing trigger pressure gradient decreasing injection pressure and increasing crude output experiments,the effect of decreasing trigger pressure gradient was studied, and while enhancing displacement efficiency,oil displacing agent could enhance oil recovery through decreasing trigger pressure gradient and was increasing capillary tubes. Through binary system profiling and ternary system profiling experiments,the capability of enhancing oil recovery of ternary injection system was verified based on increasing follow-up injecting pressure of binary system, the formation of low-middle permeability layer was sufficiently used, so the formation of low-middle-high permeability layer will be fully utilized while increasing follow-up water flooding injection pressure, and recovery was increased to a great degree after polymer flooding.