Semi-Submersible Drilling Unit Riser Disconnect – Investigation Report

On July 5, 2005, an unplanned riser disconnect was initiated on the Ensco 7500 semi-submersible rig, which had been engaged in exploratory drilling activities, because of unfavorable sea and wind conditions associated with an approaching tropical depression. While the riser volume was being displaced with seawater in preparation for the disconnect operation, the rig was no longer able to maintain station adequately enough to complete the operation. As a result, the riser was disconnected from the Lower Marine Riser Package (LMRP), at which time 710 barrels of synthetic-based mud was released from the riser into the GOM. At the time of the disconnect, there were no open hole hydrocarbons exposed below the casing depth.

2014.03.31 - Semi-Submersible Drilling Unit Riser Disconnect - Investigation Report Figure 1

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Offshore Platform Blowout – Investigation Report

This incident refers to a a brief loss of well control that occurred onboard an offshore platform in the Gulf of Mexico a few years ago. The operator was attempting to pull the tubing free of the seal assembly in a Baker SC-2 packer set at 10,830 feet to repair the Surface Controlled Subsurface Safety Valve (SCSSV) set at 350 feet (RKB) or 232 feet below mud line. In the attempt to retrieve the hanger, the 2 7/8-inch, P-105 tubing parted at approximately 4300 feet while working the pipe up and down. The 2 7/8-inch tubing began getting pushed out of the hole by well pressure and fluid in the annulus began flowing.

2013.12.30 - Offshore Platform Blowout - Investigation Report Figure 1

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Riser Disconnect and Blowout – Incident Investigation

This accident investigation report refers to the accidental riser disconnect and subsequent uncontrolled flow during drilling operations which occurred on Mississippi Canyon Block 538 in February 2000. The Ocean Concord (semi-submersible mobile offshore drilling unit) was in the process of running a liner on drill pipe when the lower marine riser package (LMRP) was inadvertently disconnected from the blowout preventer (BOP) stack. The disconnect resulted in the discharge to the sea of approximately 806 barrels of synthetic mud from the riser and 150 barrels of synthetic mud and 150-200 barrels of crude oil from the wellbore.

2013.07.08 - Riser Disconnect and Blowout - Incident Investigation Figure 1

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Loss of Well Barriers in Connection With Wireline Operation – Investigation Report

The incident occurred on Draugen in connection with a wireline operation in a well. The well was completed and started producing in 1994. Since January 2010, the well has been shut-in. Planning for the wireline operation started in the 4th quarter of 2009. During a planned test, it was discovered that the hydraulically operated main valve in the Xmas tree was not tight, which would entail repair or replacement. The wireline operation was therefore postponed until the main valve had been fixed. At the end of November 2010, the main valve had been repaired, and the implementation of the planned wireline operation could start again.

2013.05.27 - Loss of Well Barriers in Connection With Wireline Operation Figure 1

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Engine Room Fire on Mobile Offshore Unit

A fire occurred in the port engine room of a semi-submersible drilling unit whilst carrying out exploration drilling in Norwegian waters. The fire was indicated by alarms in the control room and confirmed by attending personnel. The engine room was successfully isolated manually after approximately 35 minutes, and the halon system was then activated. This, however, did not completely extinguish the fire, which re-ignited. The fire was eventually extinguished some 7 hours after the initial alarm.

2013.04.05 - Engine Room Fire on Mobile Offshore Unit

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