Synthesis of Fe3o4@Pei/Pam Smart Polymer Gel as a Magnetically-Controllable Directional Plugging Agent for Conformance Control in High-Temperature Oil Reservoirs

Polymer gel technology has been proven to be one of the most effective methods for conformance control and enhanced oil recovery (EOR). However, traditional polymer gels have significant limitations when it comes to directional plugging. To address this challenge, a novel smart polymer gel (SPG) composed of a water-based ferrofluid (Fe3O4@PEI) and polyacrylamide (PAM) is designed and prepared to achieve conformance control by directional plugging in target reservoirs. The resultant Fe3O4@PEI exhibits remarkable suspension stability and magnetic properties in water, as well as a uniform dispersion and smaller particle size (3.83 nm) in water, with a density of 2.98 g/cm­3. Furthermore, our method utilizing Fe3O4@PEI as a chemical cross-linker enables effective and controlled cross-linking with the PAM molecules, resulting in a stable and magnetically-controllable SPG with a 3D network structure. SPG-6.0 resulting from this process demonstrates a solid-like state at 120 ℃, with an average storage modulus of 25.490 Pa and an average loss modulus of 7.610 Pa. The gelation strength reaches 126,780 mPa·s after 1 month at 120 ℃. The core displacement experiments with the magnetic generator demonstrated that SPG-6.0 has a bearing capacity of up to 8.56 MPa, a plugging rate of 97.83%, and can enhance the fractional flow of water from 6.3% to 97.2% in low permeability cores. SPG's desirable rheological properties, high thermal stability, precise controllability, high plugging capacity, and effective conformance control make them promising directional plugging agents for achieving conformance control in high-temperature oil reservoirs.