Usumacinta

Rig:

Perforadora Central Usumacinta Jack-Up

Date:

23 October 2007

Location:

Kab Field, Bay of Campeche, Gulf of Mexico

Operator:

Petróleos Mexicanos (PEMEX)

Introduction

The Usumacinta is a mat-supported jack-up based on the Bethlehem JU-200-MC design. It was delivered in 1982 by Bethlehem Steel in Singapore and is currently owned by Perforadora Central of Mexico. In October 2007, the Usumacinta was contracted to drill at PEMEX's Kab-101 platform in the Bay of Campeche. The Kab-101 platform is a light production Sea Pony type platform, installed by PEMEX in 1994, which had two wells producing a daily output of around 5700 bbls oil and 700,000 cubic feet of natural gas. The Usumacinta was contracted to complete drilling work on a third well, named Kab-103, when it collided with the Kab-101 platform and ruptured the Kab-101's production tree.

Storm Collision

On Sunday, 21 October 2007, the Usumacinta was brought into position alongside the Kab-101 platform to finish drilling the Kab-103 well. By Tuesday, 23 October, a cold weather front passed through the Gulf of Mexico bringing storm winds of 130km/hr with waves of 6-8m. The adverse weather conditions caused oscillating movements of Usumacinta jack-up from around 1200 hours on the 23 October. These movements caused the cantilever deck of the Usumacinta to strike the top of the production valve tree on the Kab-101 platform, resulting in a leak of oil and gas. At 1420 hours, the subsurface safety valves of wells 101 and 121 were closed by PEMEX personnel, but the valves were unable to seal completely allowing the continued leaking of oil and gas. At around 1535 hours on 23 October, the 81 personnel on the Usumacinta were evacuated by lifeboat, with the ship Morrison Tide providing fire support. Rough seas hampered the rescue operation and appear to have caused the break-up of at least one liferaft.

Well control personnel were despatched to the Kab-101, with operations delayed by further bad weather and H2S release. Well control operations commenced with attempts to inject heavy mud followed by cement. Operations were again delayed on 13 November when a spark initiated by on-going work caused a fire to break out. The fire was extinguished the following day on 14 November at 2350 hours. A second fire broke out on 20 November, causing the collapse of the Usumacinta's derrick and major damage to the cantilever and connecting bridge. The fire was extinguished the same day with no injuries.

Several phases of work then commenced, including debris removal from the Usumacinta, the attachment of a valve for controlled flaring, the installation of a blow-out preventer and finally the shutting in of the well followed by killing with heavy mud and plugging with cement. By 17 December 2007, PEMEX reported complete control of the well.

Aftermath

Pemex reported a total of 86 personnel involved in the evacuation incident, including 5 sailors sent to aid the rescue efforts. By 24 October 2007, 58 personnel had been rescued, although a lifeboat was reported found but not able to be recovered due to the weather conditions. There were 21 reported deaths during the evacuation of the Usumacinta, with one worker missing, presumed dead.

Regarding the spill, PEMEX undertook measures to contain, recover and disperse the spill. The initial spill was reported by PEMEX at circa 422 barrels per day of mostly light crude, of which 40% was estimated to have evaporated. Chemical dispersants were used alongside sea recovery operations, with a total of 8701 barrels recovered from the sea. By early December 2007, PEMEX estimated that around 5000 bbls oil had been lost from the well and not recovered. There was some criticism over the use of dispersants simply causing the oil to sink to the seabed.

Investigation

PEMEX announced that three different investigations would be undertaken, with two completely independent of PEMEX. Areas to be investigated included the initial cause of the collision and why there was such a large loss of life during the evacuation. While the results of the these investigations have not yet been made public, there has been speculation that the rig suffered some structural or jacking failure. A punch-through is thought unlikely due to the type of jack-up involved, with the large surface area of the mat-type footing exerting minimal pressure on the sea bed. All that has been confirmed so far by PEMEX is that the Usumacinta jack-up oscillated in the storm-force winds, causing the cantilever deck to strike the Kab-101's well valves.

Sources:

Rigzone: Usumacinta Rig Detail
PEMEX: Questions and answers
PEMEX: Environmental Report
Rigzone: Various Usumacinta Reports
ABC News: Oil Rig Accident Kills 18

Photos
1 to 4: PEMEX Usumacinta Accident Photographs PDF document