As the briefing heads towards the end, questioning comes back to the “negative pressure test”, used to determine whether the cement job had been successful and the well had been sealed properly so no oil and gas could escape.
On the afternoon and evening of April 20, the rig crew had two attempts at conducting a negative pressure test, intended to check what would happen if the heavy drilling fluid were flushed out of the riser and replaced with lighter sea water, as part of the standard procedure for disconnecting the rig and moving away.
Many of the questions are attempts to get behind the report, for example, whether BP was taking extra risks to cut costs, how high the responsibility goes up the organization and whether there is a systemic problem at BP that needs addressing.
Now we come to what the BP team believes were the causes of the accident, and the first company in the line of fire is Halliburton, which was the contractor responsible for the cement job to seal the well.
There is a heavy emphasis placed on the cement “foam”: cement injected with nitrogen to make it lighter, to avoid damaging the rock formation of the reservoir and making it harder to subsequently produce oil.
Sure enough, the presentation moves on to a lengthy assessment of some of the factors that BP believes are not responsible for the accident, which have been cited in Congress as possible causes.
One is the decision to use just six “centralisers” to stabilize the steel casing inside the hole, instead of 21, which modelling had suggested would cut the risk of oil and gas leaks. Only six were used because the BP team working on the well believed – incorrectly – that they had an unsuitable type of centralisers on board the rig. The investigation team concluded that the decision to use only six centralisers “likely did not contribute to the cement’s failure to isolate the main hydrocarbon zones”.
Bly goes on to give the 30-second version of the report’s conclusions, which is that there were eight distinct failures that led to the accident, and it was only because all eight of those factors went wrong that the explosion and subsequent leak occurred.
“At the end of the day, all eight of these things had to occur to get from the initiation of this to the end of the accident,” he says.
One member of the accident investigation team worked on the inquiries into the Challenger and Columbia space shuttle disasters, which is highly relevant experience for understanding the failures of complex engineering procedures in the difficult and dangerous conditions in a mile of water and a further 2 ½ miles of rock below the sea bed.
BP’s presentation of the results of its internal inquiry into the Deepwater Horizon disaster is being delivered in Washington, in recognition of the fact that the most important audience it is addressing is in the US government and Congress.
The general message of the report is that mistakes were made by BP, but also by Transocean and Halliburton, the two key contractors on the project. Without failures by all of those companies, the accident would not have happened.
BP has published its internal investigation report into the Deepwater Horizon rig disaster in the Gulf of Mexico on 20 April 2010.
Largely, that it was the well cement’s fault, and thus Halliburton’s a little bit, for not testing the cement properly before placement. Although BP’s workers are in the frame too. As the report puts it:
It did not appear that Halliburton conducted all relevant lab tests on the final cement slurry prior to proceeding with cement placement. The investigation team saw no evidence that the BP Macondo well team confirmed that all relevant lab test results had been obtained and considered by the Halliburton in-house cementing engineer before cement placement proceeded.
BP’s investigation team includes a series of recommendations based on their key findings. The report notes that ”others in the industry may benefit from consideration of these recommendations as well”.
The recommendations themselves are too technical to go into in detail, but broadly cover “drilling and well operations practice” and as well as “contractor and service provider oversight and assurance”.
Here are a few that seemed noteworthy:
- Conduct an immediate review of the quality of the services provided by all cementing service providers
- Propose to the American Petroleum Institute the development of a recommended practice for design and testing of foam cement slurries in high-pressure, high-temperature applications
It just wouldn’t be a proper oil-related disaster if Greenpeace were not involved at every stage of the game.
Responding to BP’s report on the oil spill, Jim Footner, head of its energy campaign, said:
“This report is a sorry catalogue of the gaffes and failures behind the Deepwater Horizon disaster. And it’s highly likely that a truly independent report would be even more damning for BP.
“Worryingly, they’re just weeks away from drilling at similar depths in UK waters. The Government must step in right now and stop this by introducing a moratorium on deep water drilling.
It seems that not a lot went right on the Macondo welll on April 20. If you need a step-by-step description of events that led to the accident, here is BP’s more detailed account, helpfully attributing blame at each step (the emphasis is ours).
- The cement and shoe track barriers – and in particular the cement slurry that was used – at the bottom of the Macondo well failed to contain hydrocarbons within the reservoir, as they were designed to do, and allowed gas and liquids to flow up the production casing;
- The results of the negative pressure test were incorrectly accepted by BP and Transocean, although well integrity had not been established;
- Over a 40-minute period, the Transocean rig crew failed to recognise and act on the influx of hydrocarbons into the well until the hydrocarbons were in the riser and rapidly flowing to the surface;