Almost from the outset of the Deepwater Horizon disaster on April 20, BP has insisted that this wasn't its accident. Now, after four months of investigating itself, BP appears to have arrived at more or less the same conclusion. From the executive summary of BP's report (pdf):
The team did not identify any single action or inaction that caused this accident. Rather, a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation and team interfaces came together to allow the initiation and escalation of the accident. Multiple companies, work teams and circumstances were involved over time.
The BP report comes with video and appendices and will take a little while to read. Go for it.
If you're in this for what's going to happen next, you can get that in one word: Lawsuits. BP partner Transocean bit back, right away with this statement:
This is a self-serving report that attempts to conceal the critical factor that set the stage for the Macondo incident: BP's fatally flawed well design. In both its design and construction, BP made a series of cost-saving decisions that increased risk - in some cases, severely. Those decisions, made exclusively by BP, included:
Using a long production string rather than a casing tie back, decreasing the number of barriers to gas flow.
Neglecting to run a cement bond log (CBL) to test the integrity of the cement.
Installing fewer than one third of the recommended number of centralizers, dramatically increasing the risk of cement channeling and gas flow.
Failing to conduct a complete "bottoms up" circulation of the well to insure the quality of the cement seal.
Not running a lockdown sleeve to secure the production string to the well head, eliminating yet another barrier to a blowout.
Transocean's investigation is ongoing, and will be concluded when all of the evidence is in, including the critical information the company has requested of BP but has yet to receive.