Objective The contradiction of the oil-water relationship is prominent in offshore high porosity and permeability reservoirs. To address this issue, the adaptability evaluation of delayed gelation elastic silicic acid gel water plugging agent (6 wt% sodium silicate, 0.85 wt% activator ternary weak acid monoammonium GL-1 and 0.1 wt% mixed meter hydroxide) and the study of injection parameters were carried out.

Methods The gelation properties and long-term stability of the water plugging agent were investigated using a visual method. The injectability, plugging ability, water erosion resistance, and selectivity of the water plugging agent were evaluated using sand-filled tube experiments, and the injection volume, acting position and injection rate of the water plugging agent were optimized.

Results The adaptability evaluation showed that the gelation time of the water plugging agent from strength A to strength E was 72 h, and the final gel strength could reach strength I, which could meet the requirements of on-site implementation. The highest injection pressure was only 0.72 MPa, and the water plugging agent had good injectability. The water plugging agent had good selectivity, plugging and water erosion resistance properties. It could preferentially enter the high permeability channeling path. The plugging rate of the high permeability channeling path after gelation was more than 96%, and the breakup pressure gradient was higher than 4.46 MPa/m. The plugging rate was reduced by 2.31% after 50 PV continuously high-intensity water injection. After aging at 65 ℃ for 180 days, the dehydration rate was only 2.61%, indicating that the water plugging agent had good long-term properties after gelation. The experimental study of injection parameters showed that the optimal injection parameters of the water plugging agent were 0.8 PV of injection volume, 3 mL/min of injection rate, and the best acting position in the middle of the sand-filled tube. The plugging rate was 98.03% under the optimal injection conditions.

Conclusion The delayed gelation elastic silicic acid gel water plugging agent was available for water plugging the high porosity and permeability reservoirs.