Following installation of the capping stack and in line with the procedure approved by the National Incident Commander and Unified Area Command, the well integrity test will begin on the MC252 well on July 13.

For the duration of the test, which will be a minimum of six hours and could extend up to 48 hours, the three ram capping stack will be closed and all sub-sea containment systems – the Q4000 and Helix Producer – will be temporarily suspended, effectively shutting in the well.

It is expected, although cannot be assured, that no oil will be released to the ocean for the duration of the test. This will not however be an indication that flow from the wellbore has been permanently stopped, BP said.

According to the company, information gathered during the test will be reviewed with the relevant government agencies including the federal science team to determine the way forward. Options include reinstatement of containment as well as extending the test duration beyond 48 hours.

The sealing cap system never before has been deployed at these depths or under these conditions, and its efficiency and ability to contain the oil and gas cannot be assured, said BP.

The Helix Producer containment system started operations on July 12. The Q4000 containment system continues to capture oil and gas from the MC252 well and flare the hydrocarbons at the surface. Relief well operations continue throughout this period and remain the sole means to permanently seal and isolate the well.