Encapsulated chemicals for use in controlled time release applications and methods

An improved method of cementing a pipe string in a well bore comprising the steps of:

• (a) preparing a cement composition comprising a hydraulic cement, water and a controlled time release encapsulated cement strength and set accelerating chemical having a first coating of a hydrophobic film forming material or a sparingly soluble material which provides a dry shield on said chemical and provides a delay in the release of said chemical for a time period of less than about 2 hours, and a second coating of a porous cross-linked hydrophilic polymer which prevents the substantial dissolution of the resulting encapsulated chemical for a selected period of time;
• (b) placing said cement composition in the annulus between said pipe string and said well bore;
• and
• (c) allowing said cement composition to set into a hard impermeable mass therein.