Abstract: According to 9K₁h reservoir with complex oil/water layers，high permeability and fast water cut increasing，hydrophobic associating polymer with strong viscosity increasing and anti-shearing capacity is screened out as main agent and phenol-formaldehyde is used as crosslinking agent.Thus，a weak gel is developed.The strength of AP-BC gel is up to 11×10⁴mPa·s.After porous media shearing，the gelation time is prolonged by 50% and the strength of the gel is reduced by 10%，and the stability of the gel is much better.The dehydration phenomenon is not observed after 5 months.An experiment using two sand packs in parallel connection is conducted and the two sand packs with the same permeability which is saturated with oil and water respectively.The results show that this gel is more likely to block water layer.According to the 9 K₁h reservoir with bottom water and thin formation，multi-slug in-depth plugging technology is utilized，which includes gradually improve the strength and puts the gel with high strength in suitable allocation.High capacity channels can be plugged by using this technology so that displacing efficiency of water flooding can be improved.Field test shows that obvious oil increasing effect is realized by applying profile control in oil wells from second month to sixth months.

Key words: hydrophobic associating polymer, weak gel, stability, plugging capacity, suitable allocation