The Deepwater Horizon oil spill is considered the largest accidental marine oil spill in the history of the petroleum industry. But the rig explosion on April 20, 2010 can’t be blamed on a single decision, but rather a series of safety “fails,” or “risk creep.”
We know today that BP made decisions that favored speed over safety. The Transocean crew was also involved in rash decision-making. Even federal regulators who supervised drilling in the Gulf of Mexico signed off on proposals at each stage too, perhaps because they were overly impressed by the team’s strong safety record. Unfortunately, the entire industry had succumbed to what can be called “risk creep.” Over the decades, drillers gradually moved into deeper waters and sunk wells that involved greater internal pressures and hazards. The technologies and regulations originally developed for shallow waters were updated in response, but not to a degree proportionate with the growing risks. So, even as drillers were getting more proficient, disaster was becoming more likely.
At a point in the film, the project is said to be nearly a month and a half behind schedule, and to make up time, engineers were sent off the rig without performing a Cement Bond Log. The highest-ranking onsite employee of Transocean, the company that owned the Deepwater Horizon, demands what’s called a “negative test”, whereby the well is essentially allowed to flow against the cement. A no pressure reading at the surface means that the cement is holding.
Here is where the scene becomes a valuable educational aid. The test should read 0 psi, indicating control of the cement over the well. Instead, it jumps to over 1,000 psi. That should have been the end of the discussion, and everyone should have stopped operations until they could figure out why this test was not indicating 0. Instead, BP personnel insist that because no fluid appears at the rig level, there can’t be any pressure pushing anything up from below. Rather, there’s a “bladder effect” of trapped pressure around the drill-pipe, which is causing a false positive.
In no way was this the only factor leading to the blowout. However, it does distill so many of the behaviors that contributed:
– Failure to follow a fundamental tenet of the oil & gas industry – “Stop the Job” – was silenced in the name of making up time
– At best, BP’s input was a hypothesis to be tested, not a conclusion on which to act. There was no rigorous follow-up to determine what would have to be true (or false) for this hypothesis to hold.
– Most significantly, ignoring the potential downsides explaining away the data because nothing terrible had happened with previous wells (see risk creep above).
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RedVector’s Fundamentals of Petroleum Engineering course
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