PTTEP Australasia Ltd has plugged and secured the H1 oil production well at the Montara wellhead platform in the Timor Sea.
The company is now assessing the condition of the platform itself.
The plugging operation by Alert Well Control (AWC) involved setting a 1,400-m cement plug at the bottom of the 2.6-km well. This was followed by setting two mechanical plugs at depths of 1,800 m and 2,000 m before an inflatable packer was run to shallow depths from the wellhead platform.
This enabled the effectiveness of the multiple cement and mechanical barriers sealing the well to be pressure tested.
The programme had been interrupted in mid-December by a cyclone alert, and it was not until early January that AWC and support crew could return and cap the well.
Operations were carried out from the platform’s lower decks, which are still intact after the fire. There are still a number of steps to be undertaken before a full assessment of the platform status can be made and development work resumed to bring the Montara field into production this year.
Meanwhile the Australian government inquiry into the Montara oil spill has elicited a number of responses concerning the cause of the incident.
PTTEP revealed a 340-mm pressure-containing corrosion cap required by the drilling programme had not been installed on the H1 well after suspension of the well last March. This conflicts with a report from the drilling supervisor on the West Atlas jack up rig drilling the well that the corrosion cap had been fitted.
The omission was not discovered until workers returned to complete the well in August.
The later relief well operation confirmed the source of the flow was in the 244-mm casing and the most likely cause of the leak was a channel in the cement in the shoe track casing.
The Department of Environment, Water, Heritage, and the Arts said PTTEP did not submit an oil spill contingency plan—a condition for environmental approval for field development—until several months after drilling five wells at Montara in last January.
Already there have been calls from environmental organisations for increased government monitoring of offshore operations and improved risk-assessment processes. There have also been calls for heavy penalties for companies that breach safety requirements and environmental regulations.
The National Offshore Petroleum Safety Authority (NOPSA) called for an extension of its responsibilities to include regulation of well integrity in federal, state, and Northern Territory legislation. NOPSA also recommended its occupational health and safety inspectors be granted the power to issue prohibition notices on facilities where they consider there is an immediate risk to health and safety of personnel.