A Novel Silicic Acid Gel Channeling Plugging Agent for Heavy Oil Thermal Recovery

In the thermal recovery process of heavy oil reservoirs, steam channeling both underground and on the surface frequently occurs, which significantly undermines the periodic oil production and the oil-gas ratio. In this work, a silicic acid gel plugging agent was constructed by using industrial sodium silicate solution and organic small molecules as raw materials. The gelation time of the plugging agent was controllable at 90–150 ℃. Optimal gel strength was achieved when the sodium silicate concentration is set between 40% and 50%, and the activator concentration ranges from 6% to 10%. Mechanistically, the sodium silicate solution initially cross-links into monosilicic acid under the influence of the activator, followed by a polycondensation reaction to form linear polysilicic acid chains. These chains then entangle and fold to establish a stable three-dimensional network structure, endowing the gel with remarkable temperature-resistance properties, enabling it to maintain structural stability even at 300 ℃. The results of physical simulation displacement experiments show that when the injection volume of the channeling plugging agent slug is 0.5 pore volume (PV) and the aging time at 150 ℃ is 12 h, the plugging ratio can reach no less than 89%. In conclusion, this channeling plugging agent system exhibits good temperature-resistant plugging performance, providing theoretical guidance and technical support for the effective control of high - temperature steam channeling during heavy oil thermal recovery.