Failures provide an opportunity to revisit the existing practices and make necessary improvements in the way operations are designed and executed. Hydrate plug formation in certain operating conditions pose a well-recognized operational hazard. Water can form solid crystalline structure around gas molecules when favorable conditions exist. Very few hydrate formation incidents have been reported in open literature hence limiting the understanding of this subject.

One such incident occurred in Northern Alberta where a coiled tubing string became stuck due to hydrate plug formation in the well bore. Although the coiled tubing operations have become increasingly safer yet the challenging production environment results in greater intervention risks than ever. Coiled tubing failures occurring as a result of operating in these conditions enable us to learn valuable lessons which must be shared with the industry to raise general awareness and reduce industry-wide failures. During this operation, coiled tubing was run for retrieving bridge plug in a 3400m (11155ft) gas well. Restrictions were encountered during the operation, however; coiled tubing safely reached the desired depth. The plug was retrieved successfully but the coiled tubing became stuck close to surface. The pipe was freed up after several attempts and pulled inside the riser section. It was discovered that the pipe had been catastrophically buckled after the risers were opened on surface.

The paper evaluates different failure scenarios in an attempt to analyze the factors that may have been responsible for pipe failure in the given operating conditions while describing the engineering analysis, investigation conducted and lessons learned from it. The paper gives an insight into hydrate prevention techniques in order to avoid stuck pipe conditions hence preventing failures during intervention operations.

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