* Relief wells considered best option to plug leak
* BP working on backup plan if needed
By Kristen Hays
BP and the U.S. Coast Guard express confidence that the two wells boring beneath the sea floor will eventually staunch oil from the blown-out well that has been gushing for 81 days.
But they have a backup plan -- a seabed pipeline that could route the oil to a nearby floating platform or to an unused well where it could be injected deep underground.
“I think this situation has taught us from the start to have a backup,” retired U.S. Coast Guard Admiral Thad Allen, the top official overseeing the spill response, told reporters this week.
The first backup is the second relief well. The first relief well began drilling May 2 and has bored 12,788 feet (3,898 metres) beneath the seabed -- about 212 feet (65 metres) from its target, the bottom of the blown-out well. Allen said he expects the relief well to hit its mark by early to mid-August.
The second relief well, begun May 16, wasn’t far behind Friday at 10,260 feet (3,127 metres), BP spokesman Mark Proegler said.
Oil industry experts expect the relief wells to work.
If they don’t hit the right target on the first try, “they can poke around there as long as they need to make it work,” said David Rensink, president of the American Association of Petroleum Geologists.
“I just can’t imagine two of them not being able to do it. I’ve seen relief wells work,” said Donald Van Nieuwenhuise, director of petroleum geoscience programs at the University of Houston.
The first relief well will pierce the blown-out well, find the oil, then pump in drilling mud and cement to kill the leak. If that fails, the second relief well will do the same.
If both relief wells fail, Allen said BP has a plan to fabricate a new pipeline, place it on the seabed and hook it up to the leaking wellhead.
The pipeline could transport oil and gas to an existing platform to be processed, or to an unused well to be injected into a reservoir below the ocean floor, Allen said.
If needed, that option would occur “somewhere in the later August time frame,” Allen said.
Allen repeatedly said this week he is sticking to an August finish date for the relief wells, though the first well could plug the leak by the end of July if no problems or interruptions emerge.
Nieuwenhuise said the pipeline backup plan is doable, though time-consuming to set up. He said injecting oil and gas into a seabed reservoir -- much like crude is deposited into the Strategic Petroleum Reserve’s salt caverns -- could be easier than configuring equipment to get it aboard a platform.
Rensink was more skeptical of the platform option. He said the Macondo well isn’t a normal producing well because of the blowout and failed equipment. If hooked up to a platform via pipeline, it may not be safe to shut off the well’s flow if a hurricane comes, he said. Platforms typically stop production during storms.
BP and the government don’t know how badly the April 20 blowout damaged the wellbore when the blowout preventer failed, Allen said. Rensink said stopping the oil flow could cause a dangerous pressure buildup at the wellhead.
Nieuwenhuise said BP also could possibly detonate a bomb -- conventional or nuclear -- in the well to try to stop the flow. But a blast could damage seabed oil and gas pipelines or cause an undersea mudslide that could damage numerous other offshore energy operations.
“The big danger with any kind of implosion method is that it’s a wild card, and you don’t know what other kinds of problems it would bring,” Nieuwenhuise said.
Editing by Eric Beech