Abstract: Water channeling of fractured carbonate rocks seriously restricts oil well production and is particularly prominent in the Troyes oilfield, located in the north of Kazakhstan. A nanometer particulate matter (PM) solution was used to evaluate the plugging ability of matrix and fractured core in a fractured carbonate model. Results showed that PM had good dispersion and swelling ability in simulated formation water. The swelling rate reached more than 300% in 3 d. PM had a perfect deep plugging effect in both matrix core and fractured core. The residual resistance coefficient of matrix and fractured core after plugging reached between 3.29 and 5.88, and the plugging rate was between 69.58% and 83.01%. The higher the residual resistance coefficient, the higher the plugging rate. PM has a good selective plugging effect on oil/water. The oil/water selection coefficient R_w/o was less than 1.0 and close to 0, mainly because of the different mechanisms of oil/water and PM. Scanning electron microscope (SEM) imaging results showed that the plugging mechanism of PM in the throat and fractures was manifested mainly in three aspects: adsorptive retention, mechanical trapping, and agglomeration plugging. The mechanism was further verified by energy disperse spectroscopy (EDS) elemental analysis technology.

Key words: Nano-polymer microspheres; Fractured core; Plugging rate; Oil/Water selectivity; Plugging mechanism

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