A well kick, during a wiper trip, recently occurred on a floating drilling vessel due to loss of mud column pressure by swabbing. When the expanding gas forced mud out of the riser onto the rig floor, an employee broke his leg by accidentally stepping out of the "V" door while attempting to leave the rig floor. The volume of mud that was being swabbed from the hole was apparently lost out of a leak in the riser rather than flowing out the flowline. Initial detection of such a surface flow would have served as an early warning of the influx of gas, into the well bore, by swabbing.
A riser leak can prevent early detection of swabbing. To avoid this in the future, the operator plans to scan the riser by TV prior to trips. Observing the riser-fluid level under static conditions is also an effective means of detecting fluid loss. If the fluid level is dropping, the rams should be closed, the riser refilled, and the fluid level again observed, to determine if the mud is being lost through a riser leak or into the formation. |
