Nanocapsules for Controlled Release of Waterflood Agents for Improved Conformance

Abstract

The use of polymer gels for water shutoff is a valuable approach to control water production and improve conformance. One polymer gel system, partially hydrolyzed polyacrylamide in combination with Cr(III), shows utility for water shutoff within the near wellbore region. Deeper placement of this polymer gel system within the reservoir is challenging, owing to rapid reaction rates of the gel precursors that prohibits propagation and in-depth placement. The use of a nano-delivery vehicle (i.e., nanocapsule) to contain and shield Cr(III) from the reservoir for a defined time could enable deeper placement and effectiveness of the polymer gel treatment. By protecting the Cr(III) from the polyacrylamide, the gelation is postponed until programmed release of the Cr(III) deeper within the reservoir. Herein, we present feasibility studies that demonstrate the capacity to encapsulate Cr(III) into sub-micron nanocapsules using an inverse miniemulsion technique. Nanocapsules exhibit distinct core-shell morphology, measuring between approximately 200 nm to 500 nm in diameter, depending on the formulation. Laboratory studies successfully demonstrate the encapsulation of Cr(III) within the particles and suggest the potential for delayed release of the Cr(III) cargo. The nanocapsules tolerate simulated reservoir conditions, including high temperatures (50°C) and concentrated salinity. A stable core-shell nanocapsule designed to encapsulate Cr(III) crosslinker via a technically feasible and scalable encapsulation method addresses the requirement for improved waterflood applications and the ability to reach deeper into high permeability zones deep in the reservoir. The technological advancements presented in this paper support a novel approach and hold great potential for controlled delivery of chemistries targeted for the oilfield.