Rowan Gorilla I

Rig:

Rowan Gorilla I Jack-up

Date:

15 December 1988

Location:

North Atlantic

Activity:

Rig move

Introduction

The Rowan Gorilla I jack-up was built by the Marathon LeTourneau yard at Vicksburg, MI and completed in 1983. From 1983, the Rowan Gorilla I spent the first 5 years of its life located off the east coast of Canada. Low levels of drilling activity and high maintenance costs led to the initial decision to move the rig from Halifax, Nova Scotia to Trinidad, West Indies. Lack of a contract led to the subsequent decision to move the rig in winter across the North Atlantic to North Sea area. The rig departed Halifax on 08 Dec 1988, towed by the M/V Smit London.

Rig Capsize and Sinking

On the morning of the 13 December, a storm to the south-west of the rig's position brought winds of 60 knots and waves over 40 feet. Over the following two days, the rig was battered by high seas resulting in some significant damage. Wind and wave action caused the legs of the rig to oscillate and transmit stresses to the supporting structures on the hull. This caused hull fractures to propogate and flood storage tanks in the rig's stern. The lowering of the rig's stern allowed the high seas to break over the deck, causing containers and other deck cargo to break loose and batter top-side hatches, creating more points of flooding. On top of this, the tow line, having suffered two days of abuse, broke and the Smit London could only stand by as the crew of the rig attempted to control the flooding situation.

By 1000 on the morning of the 15th December, the captain of the Smit London noted that the rig was considerably heavier by the stern and, noting similarities with the sinking of the Dan Prince jack-up, warned the rig superintendent that the rig was in imminent danger of sinking. Around noon, a series of waves from 50 to 60 foot high hit the rig, dislodging the remaining loose cargo and causing the stern to hang under the seas. After consideration, the rig superintendent then ordered the crew to abandon the rig via the starboard lifeboat.

At 1605, the Rowan Gorilla I rolled aft and capsized. Due to the state of the seas, the decision was made to leave the crew in the lifeboat (cheers, guys - it's comforting to know you care - Ed) until calmer weather arrived. They spent what could only be described as an uncomfortable night strapped into the capsule being tossed about, suffering seasickness and singing songs in their exposure suits. On 16 Dec 1988, the crew were finally ferried via a Zodiac from the lifeboat to the Smit London, which returned to Halifax.

About 6 weeks after the sinking, an inflated liferaft from the Rowan Gorilla I was recovered in the North Atlantic. The liferaft was assumed to be one of the two washed overboard from the main deck by the heavy seas.

Causes

The immediate cause of the sinking of the Rowan Gorilla I was the uncontrolled flooding of an unknown number of the rig's internal spaces, causing the loss of positive buoyancy. One of the main contributory factors was the formation of fractures in the rig's hull, which flooded the preload tanks and the port thruster room and caused the rig to settle at the stern. These fractures were thought to have been the result of excessive leg oscillation, which imparted severe stresses onto the hull. Also contributing to the sinking was probable damage to hatches, tank vents and other through-deck fittings on the hull's topside, caused by equipment and deck cargo being broken loose by boarding seas. This damage led to numerous downflooding points on the main deck.

Sources:

U.S. Coast Guard Investigations: Marine Casualty Report PDF document

Photos
1. Geological Survey of Canada