offshore mishaps and accidents

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OFFSHORE MISHAPS AND ACCIDENTS

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Offshore accidents occur, because the environment on a drilling platform is potentially dangerous.

– Oil or gas pressures are very high.

– Hydrogen sulfide gas may be present.– Human error is always a possibility.– Accidental collisions can cause a fire.– A helicopter landing/take off can go wrong.– Platform cranes can collapse and fall overboard.

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A short synopsis of offshore accidents:

• Ekofisk – wellhead blow out, 22 April, 1977. No fatalities• Usumacinta Jackup fire – jackup collided with wellhead

on Kab-101. Christmas trees exploded. 22 casualties.• Al Mariyah – Main deck collapse, 2000. 4 casualties.• Piper Alpha – three gas explosions ending with

catastrophic structural collapse, 1988. 167 casualties.• Mumbai High North – Vessel collision severs export gas

riser causing explosion and platform collapse, 27 July, 2005. 22 casualties.

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• Ekofisk

The Ekofisk B blowout occurred during a workover on the B-14 production well, when about 10,000 feet of production tubing was being pulled. The production christmas tree valve stack had been removed prior to the job and the BOP had not yet been installed. The well then kicked and an incorrectly installed downhole safety valve failed. This resulted in the well blowing out with an uncontrolled release of oil and gas. The personnel were evacuated without injury via lifeboats and were picked up by a supply vessel.

Human error

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• UsumacintaIn late-October 2007, the Usumacinta jack-up was positioned over the Kab-101 platform. Strong winds forced the jack-up off location, causing it to collide with the Kab-101 platform and rupture the platform's production tree. Twenty-two workers lost their lives as a result of the emergency evacuation in storm-force conditions. The leaking hydrocarbons ignited twice, causing major fire damage to both the Usumacinta and the Kab-101.

Accidental Collision

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• Al MariyahIn 2000, the jack-up Al Mariyah was on location over wellhead tower 94 in the Umm Shaif field. During cantilever skidding operations, the main deck of the jack-up collapsed, causing the cantilever deck to tilt over. The rig floor fell on to the platform below, damaging the helideck and topside module, whilst the derrick fell into the sea and sank. In July 2006 the rig was repaired in Bahrain.

Structural Failure

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OFFSHORE MISHAPS AND ACCIDENTS• Piper AlphaOn 06 July 1988, work began on one of two condensate-injection pumps, designated A and B, which were used to compress gas on the platform prior to transport of the gas to Flotta. A pressure safety valve was removed from compressor A for recalibration and re-certification and two blind flanges were fitted onto the open pipework. The dayshift crew then finished for the day. During the evening of 06 July, pump B tripped and the nightshift crew decided that pump A should be brought back into service. Once the pump was operational, gas condensate leaked from the two blind flanges and, at around 2200 hours, the gas ignited and exploded, causing fires and damage to other areas with the further release of gas and oil. Some twenty minutes later, the Tartan gas riser failed and a second major explosion occurred followed by widespread fire. Fifty minutes later, at around 2250 hours, the MCP-01 gas riser failed resulting in a third major explosion.

Human error

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OFFSHORE MISHAPS AND ACCIDENTS• Mumbai High North (MHN)At time of accident on 27 July 2005, the Noble Charlie Yester jack-up was undertaking drilling operations in the field and was positioned over the NA platform. The MSV Samudra Suraksha was working elsewhere in field supporting diving operations when a cook onboard the MSV cut off the tips of two fingers. Monsoon conditions onshore had grounded helicopters, so the injured person was to be transferred from the MSV to the MHN by crane lift for medical treatment.At around 1605 hours, strong swells pushed the MSV towards the MHN platform, causing the helideck at the rear of vessel to strike and sever one or more gas export risers on the MHN jacket. The resultant gas leak ignited within a short time. The close proximity of other risers and lack of fire protection caused further riser failure. The subsequent fire engulfed the platforms MHN and MHF, causing the complete destruction of the MHN.

Vessel Collision

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All these tragic accidents create the need to implement:

• Emergency escape routes,• Mandatory personnel protective measures• Training programs on Safety, Health and

Environment (SHE).• Modern and working emergency escape

lifeboats and life rafts.• Strict adherence to offshore safety rules and

regulations.• Clear communication.

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• Properly done detailed engineering design can mitigate some of the potential factors that can lead to catastrophe during the operational life of the structure.

END OF PRESENTATION

offshore mishaps and accidents

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