Abstract:

To effectively enhance the plugging effect of gel systems in high-permeability channels and their long-term stability in formations, a nano-SiO₂-reinforced composite gel system was prepared using partially hydrolyzed polyacrylamide as the main agent, phenolic resin as the crosslinker, and modified nano-SiO₂ as the stabilizer and reinforcing agent. This system exhibited shear resistance, high viscoelasticity, and high strength. The performance of the composite gel system, including its solution properties, plugging efficiency, and injection-production characteristics, was studied by using a rheometer and the experimental equipment for multi-dimensional physical simulation. Compared with conventional gel systems, the nano-SiO₂-reinforced composite gel showed improvements in gel strength by 20%-50%, elastic modulus by 50%-150%, viscous modulus by 40%-80%, and shear resistance by 15%-20%. Physical simulation experiments demonstrated that the nano-SiO₂-reinforced composite gel effectively could plug high-permeability layers and mobilize low-permeability layers, reducing the fractional flow rate in high-permeability layers from 98.3% to 2.5% and increasing the fractional flow rate in low-permeability layers from 1.7% to 97.5%, achieving a profile improvement rate of 96.8%. Under the conditions of a four-fold permeability contrast in a three-layer heterogeneous core, the oil recovery was increased by 6.9%, indicative of the effectively enhanced mobilization of medium-and low-permeability layers. The nano-SiO₂-reinforced composite gel system could provide significant guidance for improving oil recovery in reservoirs with high-permeability channels.

Key words: high-permeability channel, nano-SiO₂, gel, plugging performance, profile improvement