Slow worker reaction, equipment failure seen in rig fire
WASHINGTON — Workers reacted too slowly to stop a Gulf of Mexico well blowout that forced the evacuation of 44 people from a drilling rig and ignited a two-day fire in 2013, according to a federal report released Thursday.
The investigation also cited the failure of emergency equipment at the site and faulted two Houston companies — Walter Oil & Gas Corp. and drilling contractor Hercules Offshore — for miscalculating about the ability of fluids pumped into the well to help keep natural gas at bay.
“Given the equipment and human failures noted in the report, this incident could have easily resulted in a more tragic outcome,” said Brian Salerno, director of the Bureau of Safety and Environmental Enforcement, which oversees offshore drilling.
Salerno instructed safety bureau staff to address identified shortcomings, including deciding whether new requirements are needed to bolster the capabilities of blowout preventers used as a method of last resort to seal off a well and trap oil and gas inside.
That device failed to stop the surge of gas from the well that a Hercules 265 jack-up rig was drilling for Walter Oil & Gas 55 miles off the Louisiana coast in July 2013.
The crew escaped in life boats, but gas surged out of the well for 13 hours before it ignited and burned another two days. It was snuffed out naturally, when sediment inside the well accumulated, “bridging over” and halting the flow of gas that fueled the blaze.
The investigation by the safety bureau and U.S. Coast Guard said the initial cause of the incident was a miscalculation by Walter and Hercules personnel about the density of fluid pumped into the well.
That fluid should have been
dense enough to suppress the flow of oil and gas, effectively balancing pressures inside the well. But the probe found that Walter and Hercules personnel did not calculate the density of the fluid to account for the full range of temperatures that could be encountered within the well. When the crew hit higher-than-expected temperatures, that affected the density of the fluid.
That resulted in a lopsided pressure situation — instead of the balance needed — and it caused gas to flow into the well, the investigators said.
The resulting influx of gas, known as a kick, went unrecognized by personnel on the jackup rig at the site. “Crew on the rig floor only became aware that the kick occurred when completion fluid began to shoot out from the open end of the annulus and drill pipe,” the report said.
By that time, the force of fluid erupting out of the well was too strong, the investigators said. It slammed drill pipe into the top drive that rotates it into wells, preventing the crew from installing a safety valve that could have helped stop the incident. The pressure also went well beyond what the rig’s blowout preventer could handle.
Because the flowing fluid carried sand from the formation, it acted to sandblast surfaces within the blowout preventer, “which would have prevented any chance of maintaining a proper seal,” had sealing rams on it successfully closed over the open well.
A spokesman for Hercules said the company was reviewing the report. A spokesmen for Walter could not be reached.
The findings seem to bolster some of the provisions in proposed regulations to require improvements in blowout preventers used offshore and the design of those coastal wells. The oil industry has criticized that proposed well control rule, saying it would impose unjustified economic burdens and discourage oil development.