The
casing pipe collapses either if pressure conditions exceed its original rated collapse pressure or the original collapse pressure rating of the casing is no longer valid due to casing wear and/or corrosion. Casing wear due to friction or corrosion decreases the effective collapse pressure rating of the casing, through the decreased wall thickness. Collapse is often discovered when the Bottom Hole Assembly BHA is run into the hole and hangs up inside the casing.
When Collapsed Casing can occur:
The collapse pressure of the casing is exceeded during a pressure test where an annulus leak is occurring.
The collapse pressure of the casing may be less than expected, due to casing wear.
The casing fluid is evacuated, causing the casing to collapse.
The casing is buckled due to aggressive Casing Running Procedures.
How To prevent Collapsed Casing Pipe Stuck?
Avoid casing wear, refer to casing wear guidelines.
Good cementing practices should be used.
Cement to the surface or as high as possible.
Use corrosion inhibitors in fluids.
Indicators For Collapsed Casing
Drill String hangs up when RIH.
The caliper log shows collapsed casing.
Freeing Stuck Pipe From Collapsed Casing
Jar out of the hole if possible.
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