PHMP was used in chemical water-shutoff test of chang-6 reservoir micromodel of Ansai Oilfield.The micromodel was made of grinded oil rock cores so as to keep the reservoir pore texture. Test result indicates that using PHMP as plugging agent in chemical water-shutoff could get evident effect. The plugging process is as follow:absorbed water film→ dynamic trapping →physical plugging→viscoelastic plugging. According to the ultralow permeability of the reservoir

its better to chose low density of plugging agent in the study area.The best ones are those with density between 20%～40%.