Mumbai High North Platform Fire

27th July 2005

pillai_sreejith@hotmail.com

Mumbai, India

Source courtesy: Internet

The ONGC MHN Platform• The Mumbai (or Bombay) High field is India's largest offshore oil

and gas field. • The Mumbai High Basin is 75 km long and 25 km wide, located in

the Arabian Sea about 160 km west of the Mumbai coast. • The oil and gas field is divided into the north and south blocks and

has been operating by the Oil and Natural Gas Corporation (ONGC) since 1974.

• The Mumbai High North (MHN) platform, a 30 years old 7-storey steel structure, was an oil and natural gas processing complex which had a capacity of 80,000 barrels per day of crude production.

• It was connected to an unmanned NA drilling platform, the BHF platform with residential quarters and the WIN platform also with residential quarters. All these were interconnected by bridges.

• The MHN facility separated oil and gas carried by risers from the nearby wells, below the NA and BHF platforms, and sent them onshore by separate undersea pipelines.

Fire affected ONGC Platform

Fire affected platform

Source courtesy: Internet

Sequence of Events• The MPS vessel Samudra Suraksha was working elsewhere in field

supporting diving operations when a cook onboard the MPS cut off the tips of two fingers.

• Monsoon conditions onshore had grounded helicopters, so the injured person was to be transferred from the MPS to the MHN by crane lift for medical treatment.

• While approaching the MHN on the windward side, the MPS experienced problems with its computer-assisted azimuth thrusters so the MPS was brought in stern-first under manual control and the injured person was transferred off the MPS.

• Strong swells pushed the MPS towards the MHN platform, causing the helideck at the rear of vessel to strike and sever one or more gas export risers carrying oil from the undersea wells to the MHN facility.

• The riser broke and crude oil started leaking. The oil caught fire and gas, under high pressure, began to escape. It was reported that a ball of flame fell on the MHN and there was explosion on the platform.

• The flow of oil and gas from the affected wells was shut down through the sub-surface safety valves.

• Emergency shut-down valves (ESDVs) were in place at each end of the risers, but some risers were up to 12 km long and riser failure caused large amounts of gas to be uncontrollably released.

Sequence of Events• The fire was so intense that the MHN was abandoned in

accordance with the disaster management plan of offshore operators.

• Within two hours, the whole platform collapsed into the sea with a few foundation piers left – Fire lasted for only 2 hours

• A total of 384 personnel were on the MHN complex, the two MPS vessels and an offshore oil rig Noble Charlie Yester at that time.

• 11 people died and 11 others were reported missing. 362 employees were rescued by a combined force of offshore supply vessels, helicopters, and vessels of Indian Navy and Coast guards.

• The MPS also caught fire and was towed away by another multi-purpose support vessel but sank on 1 August 2005, about 12 nautical miles from the Mumbai coastline.

• The heat radiation caused severe damage to the NA platform and the Noble Charlie Yester jack-up.

MPS on fire

Source courtesy: Internet

Source courtesy: Internet

Source courtesy: Internet

Source courtesy: Internet

The platform structure after fire

Source courtesy: Internet

Remains of the burnt-out platform!!

The MHN was completely destroyed in the fire, along with a helicopter positioned in it. The multi-purpose support vessel causing the fire sank few days later!!

Source courtesy: Internet

What went wrong?

• Extreme weather conditions. Under normal practice, a multi purpose support vessel can only engage an oil rig under normal weather conditions.

• DP failure. MPS vessel was a dynamically positioned vessel with computer-controlled thrusters which could remain in one position on the sea.

• Multiple riser failures (12 km long pipelines) downstream of ESDVs

• Inadequate PFP on risers• Approach of MPS from windward side

Investigation findings

• Only two of eight lifeboats and one of ten liferafts at the complex were launched;

• Inadequacy of collision avoidance practices and procedures;

• Location and vulnerability of the risers in the jacket relative to platform loading zones;

• Some riser protection guards were in place just above sea level, but these were only suitable for smaller offshore supply vessels and were not considered suitable for larger multi-purpose support vessels;

UK HSE Recommendations on Riser Protection

• Installation of fenders;

• Installing risers within caissons, well conductors and J Tubes;

• Not allowing risers to be located inside platform loading zones;

• Risers routed away from hazards such as fire, explosion and impact;

• Vessel loading/offloading/mooring not undertaken at riser locations;

• External risers not located on prevailing weather side of platform;

• Other operational procedural safety controls and permit;

• Other marine operation and safety controls in the vicinity of offshore installations; and

• Provision of subsea isolation valves (SSIVs) to limit the consequences of any riser damage.

Questions

• Can this happen in your offshore complex?– Are the supply / stand-by boat allowed access close

to installations, especially risers?– Are the boat / helicopter operations restricted during

bad weather conditions?– Does your protocols allow boats to approach from

windward side during windy conditions?– Are the boats with DP class and how do you ensure

that the DP is functioning?– Are risers protected from boat impacts?

Possible FPSO / Platform Vs Boat/ship interactions

Visiting Vessel

Passing Vessel

Fixed Platform

FPSOPotentialCollision

Learning• Even a small error can escalate and go totally out of control!

• Always be aware of the hazards and safety issues involved in every activity performed.

• FPSO / Platform collisions may be rare but they can happen. If it does happen, usually with catastrophic consequences.

• No safety system can mitigate in case of catastrophic accidents such as a riser failure and resulting jet fire!!

• We should ensure that these events do not occur at all (reduce the event probability to ALARP!)

pillai_sreejith@hotmail.com