Montara inquest

The monetary and environmental cost of the 72-day Montara field oil leak which culminated in a devastating two-day platform fire in the Timor Sea has yet to be determined, but the Australian Government has been quick to establish a Commission of Inquiry into the incident that will have the powers and authority of a Royal Commission. Rick Wilkinson reports.

The company at the centre of the drama, 100% field owner and operator PTTEP Australasia – a subsidiary of the Thai national petroleum exploration and production company – has pledged funding for an extensive environmental monitoring program of the surrounding seas and northern Australian coastline.

In addition, four parallel reviews and investigations are being carried out by Northern Territory and Federal Government departments, the National Offshore Petroleum and Safety Authority and the Australian Maritime Safety Authority.

Montara on fire with the West Atlas cantilever buckled over and down on to the wellhead platform’s helideck and flames spreading to the jackup rig’s upper superstructure. The picture was taken on 2 November from the firefighting vessel Nor Captain during a run to within 200m of the burning structures to allow an Alert Well Control team to better assess the situation. PHOTO: PTTEP AUSTRALASIA.

The Montara oil and gas field, which lies in 80m of water about 650km west of Darwin, was still in development stage when the saga began on 21 August. A steel wellhead platform had been installed earlier in the year and Seadrill’s jackup rig West Atlas was engaged in simultaneously drilling and completing two horizontal production wells plus a gas re-injection well through the platform jacket when oil and gas were detected leaking from one of them.

West Atlas sister rig West Triton (background), brought in to drill the relief well.

The rig and platform were immediately evacuated and PTTEP engaged troubleshooting company Alert Well Control to lead a well control program. It was decided to bring in another Seadrill jackup West Triton to drill a relief well. There was a delay of several weeks while the second rig was towed in from Singapore and then another month to drill the relief well.

In the meantime oil continued to leak into the sea at an estimated rate of 400b/d, a circumstance which caused an outcry from environmental groups around Australia and internationally. PTTEP, backed by the oil industry, maintained that as Montara oil is very light crude much of the spill dispersed and evaporated quickly in the tropical temperatures of the region.

More delays occurred when four attempts to intersect the rogue well from West Triton failed. The fifth attempt on 30/31 October succeeded and heavy mud was pumped down to kill the leak. Unfortunately during that operation gas and oil from the leaking well ignited at the surface and fire broke out around the cantilever section of the West Atlas engulfing the rig and platform.

Initial attempts to douse the fire with seawater from a nearby service vessel failed and the company decided the best course of action was to continue pumping heavy mud to kill the well and stop the flow of fuel for the fire at its downhole source.

This was accomplished on 2 November, although spot fires continued on the rig for another day. They were allowed to burn themselves out. The resultant damage is graphically illustrated in the accompanying photos (right).

PTTEP has conducted several aerial reconnaissance flights to help assess the damage and will re-board the platform when deemed safe. However the company is tightlipped about the cause of the incident saying it will save any comment for the official inquiries.

Its future plans for the field are also uncertain. PTTEP acquired the Montara field along with nearby Swift, Swallow and Skua oil fields in December 2008 when it bought the assets of private Australian company Coogee Resources.

Coogee had already established plans to develop all four fields (in Skua’s case re-develop as BHP Petroleum produced it until 1997) using subsea completions and flowlines to Montara as the hub where an FPSO would be stationed.

PTTEP picked up those plans and intended to bring the fields onstream beginning in early 2010.

Montara was originally found by BHP Petroleum in 1988. It has a 10m oil column underlying a 25m gas cap. Overall 2P oil reserves for the four fields have been estimated at 38 million barrels recoverable.

The Australian Government’s Commission of Enquiry is to report its findings before April 2010 and include recommendations on measures that might prevent similar incidents occurring and alleviate the safety, environmental and resource impacts arising from such an incident. OE