Investigation into the migration of polymer microspheres (PMs) in porous media: Implications for profile control and oil displacement

To reduce the unwanted water and further enhance oil recovery, a profile control agent, named polymer microspheres (PMs), was synthesized by inverse emulsion polymerization and its physical properties including morphology, particle size distribution, dispersibility strength and hydration swelling property were thoroughly examined. The main goal of this paper was to investigate the migration behaviors of the PMs in porous media using visual micromodel, nuclear magnetic resonance (NMR) and core displacement tests. The visual images indicated the PMs could plug the high permeability area and divert the subsequently injected fluid to lower permeability area. Moreover, the PMs could re-migrate in the high permeability area and displace residual oil due to elastic deformation. The NMR results revealed that the PMs with low expansion rate and high elasticity generated higher swept volume and displacement efficiency, thus leading to higher oil recovery, compared to those having high expansion rate and low elasticity. It can be observed from oil-water relative permeability curves that compared with water flooding (WF), the oil-water isotonic point was shifted into higher water saturation and disproportionate permeability reduction (DPR) occurred during PMs flooding (PMF). Finally, the profile control and displacement mechanisms of PMs were proposed based on the experimental observations.