The result of visual displacement experiment of the sandstone pore micro model indicates that polyacrylamide chemical plugging agent should have priority to be selected as a chief agent for plugging wide channels in reservoirs. The viscosity variations of the plugging agent after entering the channel can be classified as follows: big slug with low viscosity; big slug with high viscosity and small slug with high viscosity. The process that formed plugging mechanism and plugging result can be described as: absorbed water film produced by pore channel surface-dynastic entrapment of gel network floc-unit-physical plugging- viscoelastic plugging effect. In addition

under the same water plugging condition

PHMP and clay composite plugging agents are more suitable for plugging wide channel and fractured reservoirs

whereas PHMP and TP-920 swelled-grain composite plugging agents are fit for plugging wide channels and fractures

the chemical plugging agent above shows that plugging result in double pore medium has more significance than that in single pore medium.