Abstract: It is difficult to realize deep profile control because of the small pore-throats and complex structure of low-permeability reservoir, and there is contradiction between injection and plugging in traditional polymer microspheres. In order to solve this contradiction, a polymer microsphere plugging agent (CSA) containing amide groups on the surface of microspheres was prepared based on emulsion polymerization of styrene and acrylamide. The dispersed solution of CSA microspheres, whose particle size is much smaller than the diameter of pore-throats, was injected into the reservoir. When the microspheres migrated to the deep part of reservoir, these microspheres could automatically self-aggregate into large particle clusters because of the physical and chemical effects, so as to realize the plugging of the water channels. In this paper, the morphology, temperature resistance and self-aggregation properties of CSA microspheres were studied through transmission electron microscopy (TEM) and bottle test. The results showed that CSA microspheres exhibited heterogeneous core-shell structure, good dispersion, and outstanding thermal stability. The microspheres remain regular and uniform spheres at 100℃ after aging for 35 days. With the increase of the concentration of the cations, the self-aggregation time of CSA was gradually shortened, and the influence of bivalent cations was greater than that of monovalent cations. Core flooding experiments showed that CSA microspheres have good injection properties, CSA microspheres clusters can effective plug the water channels and migrate to the deep part of the reservoir for profile control.

Key words: low permeability reservoir, deep profile control, emulsion polymerization, microspheres, plugging characteristic