Newswise — Time is the enemy when combating an accidental oil or gas release, especially when the leak takes place in water a half-mile deep or more. "Knowing where the spill will surface so you can have clean-up crews in place can mitigate some of the environmental impact," says Clarkson University Professor and Researcher Poojitha Yapa.
As exploration goes ever deeper into the world's oceans to satisfy our global thirst for energy, the production of oil and gas from extremely deep wells is increasing dramatically. Yet, until recently oil companies and governments had no way of knowing what happens to gas or oil if accidentally released at extreme depths of 2,500 feet or more. Predicting how the oil would spread and where slicks would surface was pretty much guesswork. Variables like the chemical composition of oil and gas, ocean currents, deepwater pressure, and temperature influence the thermodynamic and hydrodynamic laws that govern the oil and gas spills as they ascend from the ocean bottom to the water surface. At those depths it can take several hours, or even days for a spill to reach the surface.
It was this critical need to understand the behavior of oil and gas released at extreme depths that drove Clarkson University researchers, under the direction of Yapa, to develop a deepwater oil spill computer model. The project took four years and was sponsored by the United States Minerals Management Services (MMS) and a deep-spill task force consortium made up of more than 20 oil companies. The computer model, named CDOG by Yapa and his team, can closely simulate the behavior of oil or gas from a well blowout in very deep water.
"In any modeling project, model verification is critical," remarks Yapa. In 2000, a consortium of oil companies and MMS put his model to the test by sponsoring a series of large-scale field experiments off the coast of Norway. They completed a series of four significant oil and gas releases in the Norwegian waters from a depth of more than 2,500 feet. "The project was costly " roughly $2.5 million," states Yapa, "but the data from these experiments was unique and extremely valuable." Using CDOG, the Clarkson team simulated the deepwater experiments then compared the results with actual field data from the Norwegian releases. The comparisons were so good that both the model development and the results of these comparisons have been published in leading hydraulic engineering journals.
"Though the industry safety record has been very good to date," Yapa says, "as deepwater oil and gas exploration increases, our models become extremely valuable for contingency planning, ecological risk assessment, and decision making during emergencies."
However, spills are not the only way oil and gas are released into the ocean. There are also natural releases through vents on the ocean floor. Although the release from a vent or deepwater well blowout may start out as a gas, it has the potential to be converted to a slush-like material known as "gas hydrates." These materials are buoyant and travel upwards with the oil and gas plume. As the plume continues rising to the surface, pressure and temperature changes cause this slush to revert back to a gas, which can separate from the plume. The gases can dissolve into water. "This is a complex scientific process and neither the gas nor the plume mass may come to the surface directly above the vent that spewed it," emphasizes Yapa. "Our computer modeling will predict where it is likely to surface."
In addition to ocean vents, there are literally hundreds of sunken ships around the world. "The potential for oil leaking from these vessels is high," notes Yapa. Several countries have sought his expertise to simulate what will occur following accidental spills at levels ranging from surface releases, to those at extreme ocean depths. He is currently involved in a 10-year study for Japan to develop computer models for deepwater releases and the ecological impact assessment of a potential oil spill in Tokyo Bay. Yapa and his Clarkson University team are also beginning a new three-year project for the Japanese to model the physical-chemical process of an oil spill. He has created oil spill models for Singapore and Brazil, and has contracted to do models for both Kuwait and Spain. In addition, the St. Lawrence Seaway Development Company is using a model co-developed by Yapa to help it respond in the event of an oil or chemical spill.
Currently, Yapa is working with the National Oceanographic Atmospheric Administration's Hazardous Materials Branch (NOAA HAZMAT) to integrate his oil spill model with theirs.
Photo Caption: An oil and gas blowout (Photo courtesy of NOAA HAZMAT)
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