Well control personnel respond to a wide range of issues, many of which are directly related to well integrity.
In many cases, an intervention on the well would have been substantially less complex if a proactive approach had been taken before the event occurred.
Tubular failures
Tubular failures are among the most complex and challenging issues to address when a well is flowing in an uncontrolled state. This uncontrolled state typically occurs because the wellbore barrier (casing or tubing) has failed, and the reservoir pressure cannot be contained by an exposed formation post-failure. If this has occurred, this is referred to as an underground blowout (UGBO) or oftentimes termed as cross-flow. Hydrostatic pressure is the key to an effective kill as most are readily aware of. Depending on the location of the failure, establishing a kill can become increasingly more difficult in these UGBO cases.
In general terms, tubing and casing failures that are shallow have the potential to lead to broaching. Broaching is the term used when flow from the well exits to the surface outside of the wellbore casings. Depending on the severity of the flow, all access can be lost to the wellhead making a relief well (RW) the only viable option for intervention. If access is still feasible, shallow failures may offer the chance to establish a fluid column but typically require some manner of live well intervention to access the well below the exit point (via coiled tubing [CT] or snubbing).
Tubing and casing failures that are deeper generally limit the fluid column that can be established and thus limit the hydrostatic pressure available to generate a kill within the wellbore system. Many times, these situations have only been solved by mechanical barriers in combination with a fluid column. The configuration of the well and the flowpath will ultimately dictate the proper solution.
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