Abstract: A cement composition is provided including a cement and a low reactivity particle coated with a swellable polymeric material. The low reactivity particle is coated with a swellable polymeric material at a concentration of about 10 weight percent to about 50 weight percent, based on the weight of the cement. The swellable polymeric material swells to a larger volume when exposed to one or more hydrocarbons, depending on the selected polymeric material. The cement composition is used in a method as a self-sealing cement for cementing an oil and gas well, thereby minimizing or mitigating the unwanted migration of water or hydrocarbons.

Abstract: The storable, low-density, hydraulically-active, cementitious slurry of the invention is suitable for cementing within a subterranean formation for oil or gas wells. The low-density slurry comprises a hydraulically-active cementitious material, a set retarder, a plasticizer, glass or ceramic micro-spheres, and a strengthening agent. Further the slurry is substantially free of a suspension agent. The storable, low-density, hydraulically-active, cementitious slurry is made by adding glass or ceramic micro-spheres to a hydraulically-active cementitious material, adding a strengthening agent to the microsphere containing composition, and mixing the resulting composition with water, a set retarder, and a plasticizer to generate a slurry, wherein the set retarder is present in an amount sufficient to allow storage of the slurry.