Study Of Polymer Microspheres For Profile Control In Bohai Oilfields

Polymer microsphere is a conformance control agent with excellent performance,and it has small dimensions and deformation migration capacity.Injected in the deep reservoir,microphere can improve the water flow channel and increase the sweep coefficient of injected water.In recent years,polymer microspheres have been applied in Bohai Oilfields to control the water cut and enhance oil recovery.In order to provide reference for the field application of polymer microsphere as a conformance agent,the basic morphology,swelling capacity,injectability and EOR of polymer microspheres were studied in this dissertation.Firstly,the morphology and size of the microspheres were observed by optical microscopy,particle size analyzer,SEM and TEM.The size distribution and swelling ability of the microspheres were determined by laser particle size analyzer.Secondly,by measuring the injection pressure of the microspheres with different injection parameters,the resistance coefficient and the plugging rate were calculated,and the injection performance and plugging capacity of the microspheres were investigated.Finally,by investigating the changes of microspheres injectivity,water cut and recovery under different oil saturation,the variation regularity were summarized and the appropriate microsphere injection timing was determined.The results show that the mean diameter of initial core-shell microspheres is about15 micron,and the expansion ratio of core-shell microspheres that dispersed injected water at the stratum temperature is 3.05 times.And the mean diameter of initial nanospheres is about 79 nm,and the expansion ratio of nanospheres that dispersed injected water at the stratum temperature is 4.97 times.The permeability suitable for core-shell microspheres is higher than that suitable for nano-microspheres.The plugging rate of nanospheres is higher than that of core-shell microspheres.Decreasingthe injection rate and swelling time is beneficial to reduce the injection resistance coefficient of the microspheres and increase the plugging rate.In the relative permeability curve,the lower the relative permeability of water,the higher the injection pressure of microspheres.There are suitable injection timing for nano-microspheres and core-shell microspheres respectively.The total oil recovery of nano-microspheres is the highest when oil saturation is 30%,and that of core-shell microspheres is the highest when oil saturation is 50%.