BP blamed for Gulf of Mexico disaster in new report

BP (BP.) found itself in the firing line on Wednesday afternoon, after an internal investigation by rig owner Transocean (RIG) found BP largely responsible for the catastrophic Gulf of Mexico oil spill.

The offshore drilling contractor blamed a "succession of interrelated well design, construction and temporary abandonment decisions," many made by operator BP, as the cause of the Deepwater Horizon rig explosion on 20 April 2010 and the subsequent oil spill.

Transocean said the decisions, many made by BP in the two weeks leading up the incident, were driven by the British oil giant's knowledge that the "geological window for safe drilling was becoming increasingly slow."

It goes on to note that BP was specifically concerned that downhole pressure - whether exerted by heavy drilling mud used to maintain well control or by pumping cement to seal the well - would exceed the fracture gradient and result in fluid losses to the formation, thus costing money and jeopardising future production of oil.

The Swiss firm said BP also failed to properly communicate risk to its contractors, such as the absence of adequate testing on the cement or the uncertainty surrounding critical tests and procedures used to confirm the integrity of the barriers intended to inhibit the flow of hydrocarbons into the well.

However, the company made clear that the findings of the report did not represent the legal position of Transocean, nor attempt to assign legal responsibility or fault.

Nevertheless, it is in stark contrast to BP's own internal report, which blamed a series of causes on multiple parties, in line with government investigations which have also held a number of companies to account.

The companies involved in the worst offshore oil spill in US history have sued each other in a bid to recoup their losses.