Synthesis and In‐Situ Aggregation Plugging Capacity of Nanoparticles as Potential Deep Profile Control Agents

To address the poor injectivity of conventional chemicals, and the drawbacks of existing elastic polymer particles in deep conformance control of low permeability reservoirs, nanoparticles with self‐aggregation properties were fabricated in this study. The injectability, aggregation properties, and in‐situ aggregation plugging capacity of nanoparticles in the reservoir were systematically investigated. Results show that the increase of the ion concentration and cationic charge number is beneficial to the aggregation of nanoparticles. Moreover, the aggregation time was longer when sulfonic acid groups were grafted on the surface of nanoparticles. Core flooding experiments show that when the core permeability is between 50×10−3 μm and 450×10−3 μm, the nanoparticles with an average particle size of 252.9 nm can successfully propagate to the deep formation and plug water channeling areas through the particle clusters formed by in‐situ aggregation. The negative change of Gibbs free energy and enthalpy indicates the reduced energy of the mixture system in the process of aggregation of nanoparticles, which reveals the essence of aggregation of nanoparticles. Nanoparticles with self‐aggregation properties were fabricated. The prepared nanoparticles have outstanding injectability and remarkable plugging capacity. Nanoparticles can form particle clusters with larger particle sizes through in‐situ aggregation in the pore throats to block water channels. This study provides a new method for the equilibrium between nanoparticle injectivity and in‐depth profile control in low permeability reservoirs.