Blown out Gulf well secured — but not killed

A natural gas well that blew out in the Gulf of Mexico in July has been plugged, though it may be a long time before it is permanently killed, federal regulators confirmed Monday.

Even before emergency workers began tackling the blown-out Walter Oil & Gas well, it had been naturally clogged by sand that halted the flow of hydrocarbons. When gas first started spewing from the well on July 23, 44 workers evacuated a Hercules rig at the site, hours before it caught on fire.

Houston-based Walter Oil & Gas began drilling a relief well at the site in early August, with plans to intercept the original failed well and pump it full of cement. But in the meantime, the company and its contractors continued other interventions, including setting plugs and pumping cement into the wellbore.

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Those steps — completed on Aug. 13 — apparently paid off. The Bureau of Safety and Environmental Enforcement said debris was fully removed from the site as of Sept. 6, and no gas has been detected in the area. Although the bureau is continuing to monitor work at the site, a unified command consisting of the safety agency, the Coast Guard and Walter concluded its oversight of the response efforts on Aug. 11.

On Aug. 30, the safety bureau approved Walter’s proposal to convert its planned relief well into one that will produce remaining natural gas in the reservoir. Over time, as gas drains from the same reservoir, pressure is expected to decline to a point when the weight of seawater can be used to keep it at bay. The safety bureau said the original, damaged well would be reentered at a later date — after the pressure declines from the planned production — to set deeper, permanent plugs.

The jack-up rig Rowan EXL-3, has been conducting relief well drilling at the South Timbalier 220 site, about 55 miles from the Louisiana coast.

The blowout occurred the morning of July 23, when the Hercules 265 jack-up rig was drilling a sidetrack well, entering an existing wellbore with the goal of tapping another portion of the same reservoir.

The Interior Department’s Bureau of Safety and Environmental Enforcement has launched a panel investigation of the incident, which could take a year or longer to complete. The investigation will probe what caused the sudden influx of natural gas at the site and why emergency equipment may have failed to keep it in check. Investigators also are expected to examine what caused explosive gas to ignite 10 hours after it started coming on board the rig.

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Factors could include the geology of the region, an area of the Gulf known for its sandy production and the propensity for washouts, when sand sloughs away from the sides of a well, creating a larger opening and the potential to lose drilling fluids in the formation.

Coast Guard officials previously told lawmakers a possible ignition source may have been abrasive sand hitting metal on the rig, after flying through the blowout preventer. But a spark would have been inconsequential were it not for a cloud of explosive gas on the rig.

No oil was spilled at the well, and natural gas evaporates over time, though not without environmental effects as its main component is the greenhouse gas methane. Although methane does not remain in the atmosphere as long as other greenhouse gases, it is 21 times more potent than carbon dioxide in warming the atmosphere.