One application of the PEC nanoparticles is the delayed release of crosslinking agent for polymer gels used in water shutoff and conformance control.
Unproductive cycling of injected water of EOR chemicals through high-permeability channels often results in poor volumetric sweep and hence low hydrocarbon recovery efficiency. Polymer gels can be used to block the high-permeability channels, forcing the subsequently injected fluids into the previously unswept oil productive zones. To maximize recovery efficiency, the gel needs to be placed deep into the formation.
The main issue with the current polymer gel systems is the short gelation time. A polymer gel usually consists of a polymer and a crosslinking agent. Once the gel is formed, it can no longer propagate in porous rock. Therefore, the gelation must be delayed to allow in-depth penetration. However, the gelation times of the current systems - ranging from hours to days - are generally too short. Using PEC nanoparticles to control/delay the release of crosslinking agent, the gelation times can be extended from days to weeks or even months.