A critical review on use of polymer microgels for conformance control purposes

Polymer microgels are submicron-to-micron size, water-dispersible particles that are formed through use of a crosslinking agent. Their permeability reduction capabilities, when triggered, enable the strategic plugging of high-permeability channels so as to divert flooding fluid to the relatively unswept adjacent low-permeability zones. This improves macroscopic sweep efficiency, increasing hydrocarbon production and decreasing associated water production. Polymer microgel flooding thus serves to provide in-depth conformance control, distinguishing it from conventional polymer floods that offer primarily mobility control benefits. This paper provides a literature review on the use of polymer microgel technology for conformance control purposes. Polymer microgel flooding is first introduced, and the motivation for their use over conventional polymer flooding is outlined. This is followed by a discussion on the characterization of polymer microgels as well as some theories on how they act as conformance control agents. In addition, an extensive survey of four different types of polymer microgels (Colloidal Dispersion Gels, Preformed Particle Gels, Temperature-Sensitive Microgels, and pH-Sensitive Polymer Microgels) is provided. Attention is mainly given to the microgel characteristics, laboratory observations, and field applications. The rheology and plugging mechanism of the different polymer microgels are also discussed in some detail. Polymer microgel flooding is gaining popularity as a means of conformance control. Despite uncertainty around the precise mechanism by which microgels divert flow, numerous lab and field applications have demonstrated this technology׳s ability to improve sweep efficiency and enhance oil recovery. •A critical assessment of 4 different polymer microgel types is presented.•Microgel flooding is distinct from polymer flooding and polymer gel applications.•Microgel floods provide in-depth conformance control, targeting bypassed oil.•Lab and field applications demonstrate improved sweep efficiency/oil production.•The mechanism by which microgels divert flow from thief zones is still uncertain.