BP has launched $40 billion (£24 billion) worth of lawsuits against its partners on the disastrous Deepwater Horizon rig, including claims that cementing contractor Halliburton failed to properly use modelling software to analyse safe drilling conditions.

In a trio of suits against cementing contractor Halliburton, rig owner Transocean, and blowout preventer manufacturer Cameron, BP said safety systems failed and key technology was “unreasonably dangerous”. The problems had led to $40 billion of costs for BP following the Gulf of Mexico oil spill, it said.

Halliburton’s cement modelling software, known as OptiCem, was used to design the cementing and analyse how many stabilising devices, known as centralisers, were needed for the well.

“Halliburton breached its duty of reasonable care with respect to, among other things, its provision of professional services,” said BP. This included Halliburton being “negligent”, BP said in its lawsuits, by “failing to properly run the OptiCem model, including failing to make the proper assumptions and inputs”.

Halliburton had even used the wrong data, BP alleged. “Halliburton made numerous basic mistakes in the OptiCem model, including inputting demonstrably wrong information when it had the correct information to input into the model,” it said.

Halliburton said it will "vigorously defend" itself against the claims.

US government investigations had established that BP failed to fully adhere to the results of the OptiCem software, which demanded 21 centralisers be used. BP initially adhered to the software tests and ordered 15 extra centralisers, in addition to the six in place. But when technicians on the rig received the extra centralisers they mistakenly decided the new centralisers were the incorrect type. At this point BP proceeded with the drilling anyway, with the six centralisers, in order to save time.

As the drilling proceeded on six centralisers, Brian Morel, drilling engineer at BP, wrote an email to colleague Brett Cocales, saying: “Who cares, it’s done, end of story, we’ll probably be fine”.

BP’s claim, that Halliburton had incorrectly used the software, somewhat challenges other verdicts.

Meanwhile, in its lawsuit against Transocean, BP alleged the company’s engineers had “failed to monitor” drilling fluids in the well.

“To fulfil his duties in monitoring the well to detect kicks and to shut in the well when necessary, the Deepwater Horizon driller typically ran three data screens in the driller cabin. The screens would have displayed, among other things, the drill pipe pressure and the volume of drilling fluids,” it said.

“Transocean’s drillers could (and should) be able to identify a kick in a well by monitoring the flow of drilling fluids into and out of the well, and the pressure on the drill pipe.” But procedures that took place to transfer mud and drilling fluids had “removed” a key data set, it alleged.

BP also alleged that Transocean had delayed in initiating the key safety technology called the Emergency Disconnect System, which ultimately “malfunctioned”.

Transocean branded the lawsuit as “specious and unconscionable”. It said: “The Deepwater Horizon was a world-class drilling rig manned by a top-flight crew that was put in jeopardy by BP, the operator of the Macondo well, through a series of cost-saving decisions that increased risk – in some cases, severely.”

It blamed BP for a “fatally flawed well design and poor management”. It added: “This is the latest desperate bid by BP to turn its back on the agreement they made with Transocean to assume full responsibility for the costs and liability of any pollution, contamination and environmental damage caused by hydrocarbons that leaked from the Macondo well.”

The rig had a device known as a blowout preventer, aimed at preventing dangerous oil flow. The BOP failed to function, and US government investigations uncovered that this was partly owing to a piece of pipe trapped in it. However, they also found that the BOP lacked proper backup systems.

“Cameron’s design and production of an unreasonably dangerous BOP and its negligent conduct in maintenance and repair of it, was a cause, in whole or in part, of the blowout of the Macondo well and the ensuing oil spill in the Gulf of Mexico,” BP said in a lawsuit against the firm.

One of the key control systems failed to activate because of a power problem, BP stated. Following investigations, it said, the response team found that at least one of the ‘deadman’ safety system batteries “had insufficient charge” to activate itself.

Cameron has said the BOP was "designed and tested to industry standards and customer specifications". The company said it is working with the oil industry "to ensure safe operations".

BP concluded: “The simple fact is that on April 20, 2010, every single safety system and device and well control procedure on the Deepwater Horizon failed, resulting in the casualty.

“Accordingly, the BP Parties seek at least $40 billion in damages and contribution from Transocean for the costs, expenses, injuries and damages that BP has incurred, continues to incur, and will incur as a result of the Deepwater Horizon incident and oil spill caused by Transocean’s multiple failures.”

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