A blowout preventer may have ignited the fire that caused a Gulf of Mexico rig to partially collapse Wednesday, after a natural gas well blew out, federal authorities reported.
A leak in the natural gas well, owned by Walter Oil & Gas, ignited a fire on a jack-up rig operated by Hercules Offshore late Tuesday night, hours after its 44 workers had been evacuated, according to the Bureau of Safety and Environmental Enforcement.
The ignition source may have been heat generated by the friction of formation sand shooting through the blowout preventer, according to an update to Congress from the Coast Guard. The sand may have traveled on the drill floor and up into the metal of the derrick.
While the source of the leak is still unknown, Danenberger explained that there are several possibilities. The flow path could be inside production casing or tubing.
Another flow path could be between the casing strings or the space between the two concentric casing strings. Alternatively, it could be outside the casing, back to the seafloor, either through cement channels or through fractures in the sediments.
“The fact that there is a fire would imply that that is flowing inside the casing or between the casing strings, because it is coming back up to the surface to the rig,” Danenberger said.
The next steps for the operation will hinge on how the well was constructed.
“I would hope that there is enough well bore and well integrity that they can apply a surface cap and then pump in mud and cement or make some connections to pump in heavy mud, but I have no idea what the well flow is,” Danenberger said. “They could either shut in one or more rams of the blow out preventer and pump in mud and cement or if there is some issue with it, perhaps install a surface cap with outlets that would allow them to pump in mud and cement. This is all contingent on the integrity of the well bore.”
Hercules Offshore said that natural gas flowing from the well ignited, which then spread to the rig. The company was awaiting daylight to assess any potential environmental incident, it said in a Wednesday statement.
The well is located in about 155 feet of water and the well head is above the water's surface.
A drilling rig that caught fire after a natural gas blowout in the Gulf of Mexico appears stable now that the fire is out, and there was no sign of any oil sheen on a fly-over Thursday morning, a rig company executive said.
The federal Bureau of Safety and Environmental Enforcement announced Thursday morning that the well had clogged with sand and sediment, a process called "bridging over" that Noe said can commonly happen with shallow water wells.
Now, officials are focusing efforts on permanently plugging the well and finding out why it blew wild — including why the blowout preventer system on the rig failed to stop the accident.