"The well essentially snuffed itself out," said Jim Noe, a vice-president with the rig owner Hercules Offshore Inc., speaking in a telephone interview.
The well had blown wild Tuesday, forcing the evacuation of 44 workers. The rig caught fire Tuesday night and part of it collapsed.
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.
There were no injuries when the blowout occurred about 55 miles off the Louisiana coast at a well operated by Walter Oil & Gas.
When the fire was raging, officials said they were preparing to drill a relief well nearby to divert the gas and end the blowout and fire. Such a step is probably not necessary now that the fire is out and the well has bridged over, said Adam Bourgoyne, an industry consultant and a former dean of Louisiana State University's petroleum engineering department.
He said finding some way to seal or cap the well permanently will be much easier now. Well control experts should now be able to get close to the rig and examine it.
"You never know anything for certain but usually if it bridges it doesn't re-start," Bourgoyne said.
The rig is in 154 feet of water, relatively shallow in terms of offshore drilling.
The Hercules 265 was built in 1982. It was certified by the American Bureau of Shipping until September 2017 and by the Coast Guard through July 4, 2017, according to federal records. It also had a blowout preventer control system approved in November of 2010.
In May, Hercules told its investors that Walter Oil & Gas was paying between $101,000 and $103,000 a day to rent the Hercules 265 for a 60-day period that was supposed to end July 25. After that Arena Energy was supposed to rent the rig for 90 days, paying $102,000 to $104,000 a day.
Why the blowout prevention system did not prevent the blowout is part of the investigation. Neither Noe nor anyone else connected with the investigation would say anything about the probe so far.
"Our efforts will now turn to, first, confirming the conditions at the well site, and then to assisting in Walter's effort to permanently secure and seal the well. We will then focus on a precise analysis of the facts that led to this incident," Noe said.
The rig is called a "jackup rig" because it has four legs extending to the ocean floor to hold it up. Parts of the rig had collapsed as it burned Wednesday, but the structure remained intact.
Experts had said the environmental effect of the blowout was expected to be limited, even before the well was blocked and all 44 workers were safely evacuated.
Because the well involved is a natural gas well, not an oil well, experts said the pollution threats were far less than those posed by some previous accidents.
Federal inspectors said a light sheen was spotted around the rig Wednesday evening. But like one spotted shortly after the blowout began Tuesday, the sheen quickly dissipated.
Gas wells often also have oil or other hydrocarbons as well as natural gas. Officials and scientists agree the latest accident should not be nearly as damaging as the BP oil spill, also in the Gulf of Mexico, that sent crude oil oozing ashore in 2010.
Tuesday's blowout occurred at a drilling rig next to a natural gas platform that wasn't producing gas at the time. The rig was completing a "sidetrack well," which drills into the same well hole under the platform. Such wells are used to access a different part of the gas reserve.
Associated Press writer Stacey Plaisance in New Orleans and Jeff Amy in Jackson contributed to this report.