Low permeability cement systems for steam injection application

A cement slurry composition comprises a plugging agent with a glass-transition temperature lower than about 150° C. The plugging agent is preferably an including polyethlene wax, polypropylene wax, carnauba wax or scale wax. After the cement slurry sets, it may be heated to a temperature sufficient to melt the wax. The molten wax may then flow into pores in the set cement. Upon cooling, the wax solidifies. As a result, the porosity and permeability of the set cement are reduced.