BP Trial Update I

An independent expert consultant to the oil industry testified last Wednesday that the cement pumped into the Macondo well was not given enough time to harden before a negative pressure test was run, allowing oil and gas to eject out of the well bore and explode. The explosion and ensuring fire destroyed the Deepwater Horizon drilling platform and killed eleven workers. The expert also identified at least nine major errors committed during the cementing that when combined caused the blowout. Witness for the government, Glen Benge, testified British Petroleum was most at fault since it designed the cementing job, oversaw the work, and exercised final decision making authority. He also blamed Halliburton who provided the cementing material.

According to the witness, BP engineers accepted additional risks thinking remedial work could be done later, but the blowout radically invalidated their assumptions. They used an inappropriate heavy cement mix left over from previous operations and reduced the number of centralizers from Halliburton's recommended 21 to just six placed in the bore hole. That decision weakened the cement seal on one side leaving a channel filled with drilling mud that hydrocarbons under immense pressure could blow out to the surface.[trial graphic, above: gray cement, brown drilling mud] Benge also said too little mud was used, only sixty barrels, compared to other BP wells in the Gulf which used one hundred to two hundred barrels. The heavy cement was foamed with nitrogen injection, but when combined with the synthetic oil-based mud that contained a surfactant the foamed cement could be destabilized.

The negative pressure test registered two readings of pressures greater than expected if the Macondo well were completely sealed. Other experts are scheduled to testify for the government this week including an expert on blowout preventers.