Casing Patch Types And Operations Full Guide
There are several methods for patching damaged casing while maintaining pressure ratings and without restricting internal bore diameters. The casing repair is made by removing the damaged section of the casing and then preparing the casing stub with a Dress-Off Mill.

The external patch is run in the hole on the bottom of the new casing string and externally engages the casing stub. The internal patch is a steel liner corrugated longitudinally to provide clearance for running inside the casing.
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