Abstract

In July 2005 during Tropical Storm Cindy the pressure balance safety joint on the 8" crude oil riser at the West Delta 109A platform was separated. Subsequently, measures were taken to de-oil the first 5000ft. of the separated end of the pipeline. Before further action could be taken, Hurricane Katrina passed through the area resulting in further movement of, and substantial damage to, the pipeline. Divers did locate the line at a point some 4500ft from the platform and subsequently discovered that some 7000ft. of it was buried under mudslides further downstream of the platform.

The pipe line damage could not be repaired due to it's being buried under mudslides, therefore a unique approach was taken. Cuts were made at each end of the damaged pipeline, flanges and shut off valves were installed and a 4" pipe riser was then made up to one end, picked up and tied back to the service barge some 500 ft away thus creating an engineered radius suitable for coiled tubing (CT) operations. The CT unit was then made up at an angle of 15ΒΊ to the vertical and an inflatable plug run into the riser, thence into the 8" line until it could go no further. The plug was then inflated and tested, the disconnect was activated and the crude oil in the line flushed out with sea water to the barge tanks until the returns were clean. The CT was pulled leaving the plug in place and the same procedure was repeated at the other end of the damaged section. In this way some 4190ft of the buried line was safely de-oiled leaving the balance isolated between the two inflatable plugs.

In this paper the authors will review the pipeline damage and discuss the various options considered to make the line safe and prevent leakage and environmental damage in the future. They will go on to describe in detail the preparation for, and the successful performance of, this CT deployment, the first of it's kind in the Gulf of Mexico. They will conclude that this pioneering operation can serve as a model for several such pipeline situations which the MMS has mandated should be fixed by 2010.

Introduction

The West Delta 109A platform is located in 250ft of water at the mouth of the Mississippi River. Crude oil production is routed by way of an 8" pipe line which traverses 39,000 ft. to a 12" tie-in at WD 125. In July 2005 during tropical storm Cindy the pressure balance safety joint on the 8" crude riser became separated. After the storm had passed the damage was surveyed and in accordance with approved MMS procedures several steps were taken to assess the amount of damage, if any at all. The riser was de-oiled and isolated with a lock out at the platform and a blind flange installed at the base of the riser. Divers were dispatched to locate the separated end of the pipeline which was eventually found some 300ft. away to the south west of the platform. In order to reconnect the riser a total of 300 bbls of sea water were pumped into the line behind a soluble ball and a soft foam pipe line pig. This displaced oil from the line for a distance of 5000ft. However, before complete displacement of the line could be completed Hurricane Katrina entered the Gulf of Mexico and operations were suspended.

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