A tool (composed primarily of slips, a ported mandrel, and rubber sealing elements) set in the casing which allows cement or other fluids to be pumped through the tool, but seals against any fluid movement when the tubing is released from the tool. The cement retainer is generally used in squeeze cementing work. The cement retainer cannot be unset once it has been set in the casing but it can be drilled out.
Source: API BULLETIN E3, Environmental Guidance Document: Well Abandonment and Inactive Well Practices for U.S. Exploration and Production Operations, First Edition, January 1993 (Reaffirmed June 2000). Global Standards