Project showcase

Montara Blowout

Project goal

Add Energy provided multiphase flow modelling and well control supervision throughout the entire project.

Why We Were Contracted

On August 21st 2009, the Montara H1 ST-1 well blew out underneath the cantilevered derrick of the jack-up rig West Atlas. The Montara field consists of a 4 well slot un-manned wellhead platform, located 675 kilometers west of Darwin, Australia, in the south part of Timor Sea. The water depth is ~80 m.

The production well was completed with a horizontal section into the reservoir with a 9 ⅝" casing set at total depth. The well was suspended for 5 months. In August 2009, the crew removed a pressure containing corrosion cap set inside the casing in preparation for installation of the BOP. The blowout started with a flow of condensate from a thin oil reservoir zone, followed by gas from an overlaying high permeable gas cap. All personnel were safely evacuated.

In response to the incident, Add Energy specialists were engaged to provide support and recommendations for the upcoming relief well drilling and kill operation.

Why We Were Contracted

What We Did

Blowout analysis

Add Energy specialists performed immediate simulations and evaluations in order to provide recommendations for the upcoming kill operation. The blowout simulations were based on the results from the latest reservoir modelling and surface observations.

Kill analysis

The dynamic kill simulations were based on the relief well being drilled from the jack-up rig West Triton located about 2 km away from West Atlas, by intersecting the blowing well in its horizontal section about 100 meters above the 9 ⅝" casing shoe.

Add Energy prepared a detailed kill plan prior to relief well intersection in order to assist the operator during the planning process. The kill plan included recommendations with respect to relief well intersection, milling and pumping schedule during dynamic kill and static kill operations.

In addition to the planning contribution, Add Energy specialists directed the final kill operation offshore.

The Result

Several carefully planned ranging bypasses and sidetracks were made prior to finally intersecting by milling a hole in the casing to allow circulation of kill fluid. During pumping operations, the West Atlas rig caught fire – an explosion which was felt on West Triton.

The initial kill mud rate and density that the relief well rig could deliver was not sufficient to stop the flow. Following the first attempt, an unconventional staged kill operation was planned for. The well was successfully killed November 3rd 2009, ending 74 days with pollution.

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