Research progress on polymer microspheres for in-depth profile control in hydrocarbon reservoirs: Structural design and degradation measures

With prolonged development of oil fields, injected water induces channeling along high-permeability zones, leading to a decrease in crude oil recovery rate. Polymer microspheres are extensively employed for in-depth profile control in hydrocarbon reservoirs owing to their outstanding viscoelasticity and plugging capabilities. However, reservoirs may suffer poor fluid injectivity from irreversible polymer plugging, and polymer microspheres are structurally unstable in deep reservoirs. This article systematically summarizes four structural design methods aimed at enhancing the reservoir adaptability of microspheres, including: adding functional monomers, altering the concentration and type of crosslinking agents, adding inorganic fillers, and constructing core–shell microspheres. The improvement effects of each method are discussed. Besides, physical and chemical approaches to degrading large particle size microspheres and their pros and cons were also reviewed in detail. Finally, we discussed the prospects and challenges associated with structural design and degradation methods for polymer microspheres.