In contrast to at least two earlier reportsfrom U.S. government agencies that put a large share of the blame on Transocean, Transocean Ltd.'s internal investigation blames decisions by BP PLC for the Deepwater Horizon oil-spill disaster.
Transocean owned the Deepwater Horizon, which was drilling BP's Macondo Well in April 2010 when the rig exploded and sank, killing 11 and touching off one of the worst marine oil spills in U.S. history. The well spilled 4.9 million barrels of crude before it was sealed.
According to its probe, Transocean said well design, construction, and temporary-abandonment decisions, many made by BP in the two weeks leading up to the incident, compounded the likelihood of failure.
It alleged BP knew the geological window for safe drilling was becoming increasingly narrow, specifically saying BP was concerned that downhole pressure would exceed the fracture gradient and result in fluid losses to the formation, costing money and jeopardizing future production of oil.
In addition, Transocean said Halliburton Co., maker of the cement that was used to seal the well, and BP didn't adequately test the cement slurry program, despite risks associated with the design.
Representatives from BP and Halliburton weren't immediately available for comment.
Meanwhile, in April, an investigation by the U.S. Coast Guard offered a damning critique of Transocean, saying improper maintenance, insufficient staff training and badly designed safety systems contributed to the deadly explosion. The company had disputed the report, and claimed documentary evidence in the Coast Guard's possession refuted key findings in their report.
Similarly, a U.S. presidential commission's report in January reduced the likelihood that BP would be found guilty of gross negligence. That report criticized
Transocean for failing to communicate to its crew lessons from an earlier near-miss in the North Sea that was "eerily similar" to the Gulf of Mexico blowout