Effect of Nanoparticles with Different Chemical Nature on the Stability and Rheology of Acrylamide Sodium Acrylate Copolymer/Chromium (III) Acetate Gel for Conformance Control Operations

During enhanced oil recovery (EOR), reservoir heterogeneities and fluids distributions promote preferential flow channels formation. Therefore, different types of gels have been proposed to improve swept efficiency on chemical flooding by plugging high permeability zones. The purpose of this article is to evaluate the effect that nanotechnology has on the inhibition of syneresis and the rheological properties of the Acrylamide Sodium Acrylate Copolymer/Chromium (III) Acetate gel system for conformance applications in mature reservoirs. Thus, a methodology is proposed in four stages: First, (I) nanoparticles synthesis, and characterization, followed by (II) bottle tests to monitor gelation kinetics and syneresis degree at 70 degrees C, then (III) description of the rheological evaluation on static and dynamic conditions to calculate gelation time and viscoelastic modulus (G' and G), and finally (IV) the displacement test with the best gel system in the presence of nanoparticles. Results showed that the best nanoparticle was the chromium oxide (Cr2O3), which represented the lesser syneresis degree and increased gelation time. Syneresis of gel samples in the presence of Cr2O3 at day 30 was under 1% for gels prepared with 4000, 6000, and 8000 mgL(-1) of polymer, and polymer to crosslinker ratio (p/c) of 40:1. Regarding SiO2, MgO, and Al2O3 nanoparticles, results show an improvement of gel strength. However, their thermal stability in terms of syneresis was lower. Displacement test in a triple parallel Slim Tube was able to recover an additional 37% of oil of the total oil present in the sandpacks, confirming the effectivity of the system when 100 mgL(-1) of Cr2O3 nanoparticles are included.