Cement-based blocking agents are gaining recognition and are widely used in oilfield development because of their satisfactory performance and low cost. A performance evaluation formula must be derived and a particle size compatible with the parameters of one oil reservoir or another must be selected to meet the requirements on radial injection. The relationship between the cement particle-size distribution and the formation permeability was investigated experimentally. The blocking effect of the cement in the reservoir was evaluated. The practicality of its popularization and application was estimated. The results indicate that cement with a median particle size of < 5 mu m is compatible with reservoirs with effective permeabilities from 50 to 200 center dot 10(-3) mu m(2); with particle sizes from 5 to 10 mu m, with effective permeabilities from 200 to 400 center dot 10(-3) mu m(2); and with particle sizes > 20 mu m, with effective permeabilities from 400 to 700 center dot 10(-3) mu m(2). In all cases, 90% blocking was achieved when these compatible values were used. This will contribute to the avoidance of a futile cycle in the high water cut flooding stage of oilfield development and will accelerate the field application of blocking technologies.