From: Andy Soos, ENN
Published August 16, 2011 11:02 AM

Oil Leaks

Leaks happen whether anyone wants them to or not. All that can be done is to try to anticipate them and prevent them by useful maintenance and repairs before the leak happens. A computer model that tests automobile components for crashworthiness could also be of use to the oil and gas industry, according to researchers at MIT’s Impact and Crashworthiness Laboratory, who are now using their simulations of material deformation in car crashes to predict how pipes may fracture in offshore drilling accidents. President Barack Obama in May 2010 stated that the federal government needs to look at getting the technology that would allow it to work at the bottom of the sea to plug oil leaks like the Gulf of Mexico spill. That is after that fact. Better would be to stop the leak before it happens.

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There have been many releases of oil over the years.  They are caused by many variables.  Those caused by human error or unexpected accident can only be partially prevented by better design.  Those that are the result of predicable design or mechanical failure can be prevented.

As a case study, the MIT team simulated the forces involved in the 2010 Deepwater Horizon explosion in the Gulf of Mexico, finding that their model accurately predicted the location and propagation of cracks in the oil rig’s drill riser — the portion of pipe connecting the surface drilling platform to the seafloor. In a side-by-side comparison, the researchers found that their model’s reconstruction closely resembled an image of the actual fractured pipe taken by a remotely operated vehicle shortly after the accident occurred. The group presented their results at the International Offshore and Polar Engineering Conference in June.

By testing different shapes and sizes of materials under various pressures, Wierzbicki (author) can determine a material’s overall mechanical properties, such as its strength and ductility. Knowing this, he says, it’s possible to create a simulation to predict a material’s behavior in any configuration, under any conditions. Determining the exact limits for materials is especially important for offshore drilling, he says, where pipes are continually subjected to tremendous pressures at great depths.

Wierzbicki and graduate students Kirki Kofiani and Evangelos Koutsolelos used the same principles to predict the strength and breaking points of the Deepwater Horizon’s drill riser.

The researchers drew up a computer model of the drill riser — a large-diameter pipe attached at one end to a large rectangle, representing the surface drilling platform. The team then ran a simulation that partially reconstructed the Deepwater Horizon accident: After methane gas erupted and shot to the surface, setting the entire platform on fire, the oil rig began to list and sink. The researchers simulated the sinking by slowly angling the rectangular platform downward.

As a result, the attached drill riser began to bend. A color-coded simulation showed points along the pipe where it was likely to crack: Green and blue meant the material was intact; yellow and red indicated it was at its breaking point. The group found four red areas where cracks — and oil leaks — were especially likely to occur.

The group had one point of comparison: an image, taken by an underwater robot shortly after the accident, of the ruined pipe. When the researchers compared their model with the real-life image, they found an almost perfect match.

While it’s unlikely that any pipe material could have remained intact during the Deepwater Horizon disaster, Wierzbicki says there are many improvements that can be made to shore up existing oil and gas pipelines.  

"The deeper you go in the ocean, two or three miles down, the stronger material you need to withstand the pressure," Wierzbicki says. "But stronger materials are more brittle and break more easily. So there’s a difficult problem for the offshore industry, and I think they can learn a lot from us."

Offshore oil spill prevention and response is not just design and predictions.

Important aspects of prevention include technological assessment of equipment and procedures, and protocols for training, inspection, and contingency plans for the avoidance, control, and shutdown of offshore operations. Response includes technological assessment of equipment and procedures for cleaning up oil spills, and protocols for the detection, monitoring, containment, and removal of oil spills, and the restoration of affected wildlife and habitat.

In the United States, offshore oil spill prevention contingency plans and emergency response plans are federally mandated requirements for all offshore oil facilities in U.S. Federal waters.  Oil spills in inland waters are the responsibility of the Environmental Protection Agency (EPA), while oil spills in coastal waters and deepwater ports are the responsibility of the U.S. Coast Guard.

For further information:  http://web.mit.edu/newsoffice/2011/pipeline-fractures-0815.html

Photo:  http://www.chinadaily.com.cn/english/doc/2004-12/09/content_398495.htm

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