After an apparent Tuesday night well blowout, which ignited a fire that burned for 36 hours, Transocean's Deepwater Horizon semi-submersible mobile rig sank Thursday at the Gulf of Mexico drilling site where it was stationed, about 40 miles south of Venice, Louisiana.

Search crews continued combing Gulf waters Friday for 11 crew members missing since the blast.

"Although the oil appears to have stopped flowing from the well head, Coast Guard, BP, Transocean, and [US Minerals Management Service] remain focused on mitigating the impact of the product currently in the water and preparing for a worst-case scenario in the event the seal does not hold," the Coast Guard said in a statement.

On Friday, as energy industry representatives and government officials worked to deal with the aftermath of the accident, some environmental groups saw the tragedy as another reason to abandon plans by Department of the Interior and MMS to open for oil and natural gas exploration large swaths of the OCS previously closed to drilling.

"We're strongly opposed to the proposal. It's bad for the environment. It's bad politics. The last thing we need to be doing now is doubling down on oil," Nick Berning, a spokesman for Friends of the Earth, said Friday.

In March, President Obama announced plans to open large areas of the Atlantic Ocean and eastern Gulf of Mexico to oil and gas exploration for the first time in decades.

The plan also could move drilling closer than ever to the western coast of Florida, while placing the Pacific coastline and parts of Alaska's frontier off limits.

"The argument from industry is that drilling is now somehow clean and the environmental impacts no longer exist," Berning said. "Offshore drilling is both dangerous for the workers and harmful to the marine environment and to coastal communities."

"This is the kind or accident that we never want to see again," said Sierra Club spokeswoman Kristina Johnson. "Our hearts go out to the families of the missing workers."

She said that the Sierra Club would urge Obama to reconsider his plan to open new regions of the OCS to drilling in light of the accident.

"Wherever there's offshore drilling there's going to be a risk of this type of disaster," she said.

However, Erik Molito, director of upstream and industry operations for the American Petroleum Institute, said the accident should not be a significant factor in efforts to open new regions of the OCS to energy development.

"Hopefully it does not have any adverse impact on an opportunity to develop US oil and gas resources," he said.

Continued exploration and development of the US offshore area is "essential for the economic vitality of the country," Molito said.

Despite the accident, the US offshore exploration and production industry has had an exemplary record of operating safely in the Gulf of Mexico for decades, he said.

Keith Hall, a New Orleans attorney who specializes in energy-related litigation, said he thinks that although the Obama administration will "push for a vigorous investigation of what did happen," its plans regarding expanding offshore drilling likely will "move forward at the same pace."

Aside from the apparent tragic loss of life, the long-term effects of the rig blowout likely will be relatively minor, Hall said.

"There probably will be rather minimal environmental damage. Oil will not reach the shore," he said. "Eventually, there will be drilling in the eastern Gulf.

--Jim Magill, jim_magill@platts.com