1. n. [Well Workover and Intervention]

A casing patch is a downhole assembly or tool system used in the remedial relining of casing or tubing.

A casing patch can be used to repair damaged casing sections, corrosion, or leaks. The patch can also be used to seal off unwanted perforations or repair damaged completion modules, such as differential valve (DV) tools, fracturing ports, sand screens, or inflow control devices (ICDs).

The casing patch might be a medium- to long-term repair alternative that enables production to be resumed. In addition, the casing patch can allow avoiding a major workover operation. In some cases, such as in depleted wells nearing the end of viable production, a casing patch may be the best economical means of safely returning the well to production.

See: liner,  liner patch