Brazil: Up to 2,600 barrels of oil leaked

AP News
Posted: Nov 18, 2011 6:22 PM
Brazil: Up to 2,600 barrels of oil leaked

















The oil is believed to be coming from seep lines in the seafloor near the well and not from the well itself. Natural seeps are common around the world _ perhaps the most well known in the U.S. is the La Brea Tar Pits in the heart of Los Angeles _ and are often used by oil companies during undersea exploration to determine where a good prospect for oil drilling may be.


But problems with drilling a well nearby can exacerbate the seeps and cause greater flow of oil, which can be hard to control, said George Hirasaki, a Rice University engineering professor who was involved in the Bay Marchand oil containment effort for Shell off Louisiana in the 1970s.

"Anytime there is movement of fluids, even if it didn't go to the surface of the well, the internal flow could result in the fluid going somewhere else," Hirasaki said. "It could move laterally at the same depth or increase the flow rate of natural seeps that are connecting to the surface."

Investigators will want to look at whether the weight of the mud being used during the drilling and abandonment operations was sufficient to contain the pressure inside the well, and they will also want to see whether drilling too deep caused problems in a geopressure zone beneath the seafloor, experts said.

Ed Overton, a Louisiana State University environmental sciences professor, said that to truly control the leak could be difficult.

"If you have this stuff oozing up through the ground you don't have a mechanism for control," Overton said. "If something started that to leak, that would worry me a lot more than a leak around the well. You'd have to drill a relief well and intercept that ooze."

People familiar with last year's BP oil spill off Louisiana know about relief wells.

BP spent four months drilling a relief well that it used to pump cement under the area that was spewing oil into the Gulf of Mexico, and sealed the leak permanently.

Experts said that while there are many physical differences between the BP spill and the Chevron spill, the main common thread is the slow flow of information and different explanations for what happened and the severity of what happened.

"There's a pretty long track record of all the people involved in spills underestimating at least initially the size of the spills," Overton said. "I would suspect they literally don't know, so they are trying to figure out."

The Chevron leak is smaller than those Brazil has seen in the past.




Associated Press writer Bradley Brooks reported this story in Rio de Janeiro and Harry Weber reported from Atlanta, Georgia.