308 Deepwater methane hydrates the probable cause of BP Gulf explosion

Deepwater methane hydrates the probable cause of BP Gulf explosion

(1) Deepwater methane hydrates the probable cause of BP Gulf explosion
(2) Professor  says Gulf of Mexico oil spill is 10-20 times bigger than BP admits
(3)  Huge underwater plumes of oil in the Gulf of Mexico
(4) Independent investigator Robert Bea says accident was preventable; safety compromised
(5) Drilling deeper increases risks of crushing water pressure and explosive methane gas

(1) Deepwater methane hydrates the probable cause of BP Gulf explosion

From: Max <Max@mailstar.net> Date: 21.05.2010 01:33 AM
Subject: deep water methane

http://www.guardian.co.uk/environment/2010/may/20/deepwater-methane-hydrates-bp-gulf

Did Deepwater methane hydrates cause the BP Gulf explosion?

Strange and dangerous hydrocarbon offers no room for human error

David Sassoon

guardian.co.uk, Thursday 20 May 2010 11.34 BST

The vast deepwater methane hydrate deposits of the Gulf of Mexico are an open secret in big energy circles. They represent the most tantalizing new frontier of unconventional energy — a potential source of hydrocarbon fuel thought to be twice as large as all the petroleum deposits ever known.

For the oil and gas industry, the substances are also known to be the primary hazard when drilling for deepwater oil.

Methane hydrates are volatile compounds — natural gas compressed into molecular cages of ice. They are stable in the extreme cold and crushing weight of deepwater, but are extremely dangerous when they build up inside the drill column of a well. If destabilized by heat or a decrease in pressure, methane hydrates can quickly expand to 164 times their volume.

Survivors of the BP rig explosion told interviewers that right before the April 20 blast, workers had decreased the pressure in the drill column and applied heat to set the cement seal around the wellhead. Then a quickly expanding bubble of methane gas shot up the drill column before exploding on the platform on the ocean's surface.

Even a solid steel pipe has little chance against a 164-fold expansion of volume — something that would render a man six feet six inches tall suddenly the height of the Eiffel Tower.

Scientists are well aware of the awesome power of these strange hydrocarbons. A sudden large scale release of methane hydrates is believed to have caused a mass extinction 55 million years ago. Among planners concerned with mega-disasters, their sudden escape is considered to be a threat comparable to an asteroid strike or nuclear war. The Lawrence Livermore National Laboratory, a Livermore, Ca.-based weapons design center, reports that when released on a large scale, methane hydrates can even cause tsunamis.

So it is not surprising to anyone who knows about the physics of these compounds that the Deepwater Horizon rig was lost like a waterfly crumpled by a force of nature scientists are still just getting to know.

Number One Deepwater Drilling Issue

SolveClimate contacted scientists at the Colorado School of Mines, Center for Hydrate Research, who focus on the fundamental science and engineering of methane hydrates to gain further insight. They did not want to speculate on the role that methane hydrates could have played in the BP disaster, but they were willing to provide a basic understanding of the nature and behavior of these familiar but little understood substances.

"Gas hydrates are the number one flow assurance issue in deepwater drilling," Carolyn Koh, an associate professor and co-director of the Hydrate Center, told us in an exclusive interview.

She explained that the oil and gas industry has a lot of experience with methane hydrates, because they have to be kept from forming in pipes or they will clog the lines, stop the flow of oil, and pose a danger. Drillers use inhibitors such as methanol to keep the hydrates from crystallizing inside drill rigs operating at great depth, where conditions for methane hydrate formation are ideal.

This film clip of an experiment conducted on the ocean floor near the Deepwater Horizon drilling site demonstrates how quickly and easily methane hydrates can form. It was conducted by the Gulf of Mexico Hydrates Research Consortium aboard the Seward Johnson in September 2006. The voices of the scientists conducting the experiment are clearly audible.

The clip shows with remarkable clarity a robotic arm maneuvering a clear tube over a stream of hydrate bubbles emanating from a crater on the sea floor. Within minutes, gas trapped in the tube begins to form a visible solid — a white ice matrix — thanks to the extreme cold and pressure of the ocean depth. When the tube is inverted, the hydrate, less dense than seawater, floats out of the tube, dissociating into its components, gas and water.

Oil and gas drillers encounter far greater volumes of methane hydrate than the gentle stream of bubbles escaping from a small fissure that are shown in the film.

Amadeu Sum, an assistant professor at the Colorado School of Mines and also a co-director of the Hydrate Center, explained that methane hydrates can be encountered by drillers in the deep ocean where methane hydrates are trapped in sediments beneath the ocean floor.

Vast Deposits in Ocean Sediments

Professor Sum explained gas and oil flow up the pipe together in normal drilling operations. These hydrocarbons occur naturally together in conventional drilling operations. The deepwater of the Gulf of Mexico, and other places where methane hydrates exist, present drillers with special safety challenges.

For one thing, methane hydrates are believed to exist in vast deposits underneath the ocean floor, trapped by nature in ocean sediments. Deepwater drillers could find themselves drilling through these natural hydrate deposits.

Professor Sum said geologists know much less about these hydrate-bearing sediments than conventional ocean sediments, and that there is "little knowledge of the risks" of drilling into them.

The Deepwater Horizon rig was drilling in Block 252 of an area known as the Mississippi Canyon of the Gulf, thought to contain methane hydrate-bearing sediments, according to government maps. The platform was operating less than 20 miles from a methane hydrate research site located in the same canyon at Block 118.

From the sea floor a mile down, the Deepwater Horizon rig had penetrated another 18,000 feet — almost another five miles down — into the earth's crust with pipe.

According to the National Academy of Sciences, which published a bullish report on the energy potential of methane hydrates, "Industry practice is to avoid methane-bearing areas during drilling for conventional oil and gas resources for safety reasons."

Professor Sum explained that because "with oil there is usually gas present," it is possible for methane hydrates to form in the pipe even when not drilling through hydrate-bearing sediments. The pressure and cold of the deepwater create conditions that encourage gas flowing into the pipe to form hydrates, and if the rate of crystallization is rapid enough, the hydrates can clog the pipe.

The cofferdam that BP lowered over the broken pipe gushing oil to contain the spill was almost immediately clogged by methane hydrates, which formed spontaneously. Gas escaping with the oil from the well, when trapped in the steel structure with cold water under great pressure, rapidly accumulated into an ice-like matrix.

Documented Explosive Hazard

In a book about methane hydrates, which Professor Koh co-authored, brief mention is made of a case in which methane hydrates caused a gas pipe to rupture on land, leading to loss of life.

Two workers were attempting to clear a line in which a hydrate plug had formed. The authors say that "the impact of a moving hydrate mass" caused the pipe to fail. The explosion caused a large piece of pipe to strike the foreman, killing him. The book then quotes from the Canadian Association of Petroleum Producers Hydrate Guidelines to describe proper procedures for safely removing a hydrate plug in a pipe on land.

SolveClimate was not able to find more detailed public documentation of this incident in Alberta, but mention is made in an article in a publication of the Oak Ridge National Laboratory, a federal research center associated with the Department of Energy, of a different unspecified incident on a drilling rig.

"Forces from methane hydrate dissociation have been blamed for a damaging shift in a drilling rig's foundation, causing a loss of $100 million," the article reports.

Although public discussion of damage from methane hydrate accidents appears to be minimal, the danger is well-recognized within the industry. Last November, one Halliburton executive gave a presentation before a meeting of the American Association of Drilling Engineers in Houston, titled "Deepwater Cementing Consideration to Prevent Hydrate Destabilization."

It recognizes that the cementing process releases heat which can destabilize methane hydrates, and presents something called Cement System 2 as a solution to the problem. One of the graphs shows that the system doesn't achieve gel strength for four hours.

Yet according to an eyewitness report broadcast on Sunday on 60 Minutes, BP managers made the decision to decrease pressure in the well column by removing drilling mud before the cement had solidified in three plugs Halliburton had poured.

When a surge of gas started shooting up the well, a crucial seal on the blowout preventer at the well head on the ocean floor failed. It had been damaged weeks before and neglected as inconsequential by Transocean managers, according to the CBS news broadcast, even after chunks of rubber emerged from the drilling column on the surface.

According to the Associated Press, the victims of the Deepwater Horizon explosion said the blast occurred right after workers "introduced heat to set the cement seal around the wellhead." It is not known if Halliburton was employing Cement System 2, and testifying before the Senate last week, a Halliburton executive made no mention of methane hydrate hazards associated with cementing in deepwater.

A Promising Substance

Professors Koh and Sum are concerned that a focus on the dangers of methane hydrates in deepwater drilling will obscure their promise as an energy solution of the future. They are conducting research in the laboratory to create methane hydrates synthetically in order to take advantage of their peculiar properties. With their potential to store gas (both natural gas and hydrogen) efficiently within a crystalline structure, hydrogen hydrates could one day offer a potential solution for making fuel cells operate economically. Still at the fundamental stage, their work on storage is not yet complete enough to apply to commercial systems.

At the same time, there is an international competition underway to develop technology to harvest the vast deposits of methane hydrates in the world's oceans. Japan has joined the US and Canada in pursuit of this energy bonanza, motivated by the $23 billion it spends annually to import liquefied natural gas.

According to a Bloomberg News article called "Japan Mines Flammable Ice, Flirts with Environmental Disaster," the Japanese trade ministry is targeting 2016 to start commercial production, even as a Tokyo University scientist warned against causing a massive undersea landslide that could suddenly trigger a massive methane hydrate release.

The U.S. has a research program underway in collaboration with the oil industry, authorized by the Methane Hydrate Research and Development Act of 1999. The National Methane Hydrates R&D Program is housed at the National Energy Technology Laboratory (NETL) of the Department of Energy.

The National Academy of Sciences provided a briefing for Congress last January on the energy potential of methane hydrates based on its report which asserts that "no technical challenges have been identified as insurmountable" in the pursuit of commercial production of methane hydrates.

In the wake of the BP oil disaster, SolveClimate attempted to contact Dr. Charles Paull of the Monterey Bay Aquarium Research Institute, the lead author of the report. He was unavailable for comment, attending an international workshop on methane hydrates research in New Zealand from May 10-12, and according to his assistant, out of email contact.

(2) Professor  says Gulf of Mexico oil spill is 10-20 times bigger than BP admits
http://www.jconline.com/article/20100522/NEWS0501/5220334/Professor-swept-up-in-oil-disaster

Professor swept up in oil disaster

BY ERIC WEDDLE • EWEDDLE@JCONLINE.COM • MAY 22, 2010

A Purdue University researcher who a week ago helped break the news that the Gulf of Mexico oil spill is at least 10 times bigger than BP was letting on is helping the government prepare an official spill estimate.

Steven Wereley, a mechanical engineering professor, is working with the National Oceanic and Atmospheric Administration to estimate how much oil is spewing from an uncapped well 5,000 feet below the Gulf of Mexico surface.

"I was a bystander in this," Wereley said Friday during a quiet moment at his office in the Birck Nanotechnology Center. "I watched the headlines, but I'm not a petroleum guy."

But Wereley, 43, become an inadvertent player in what many expect will become the worst oil spill in U.S. history, if it hasn't surpassed that mark already.

It started with the April 20 explosion of a Gulf oil rig leased by BP. Eleven workers died in the explosion after a blowout preventer failed to activate, allowing oil and gas under intense pressure to spew from the ocean floor.

Wereley's research is mostly in microfluidics -- fluid dynamics at the micro and nano levels. It's a far cry from the enormous volumes coming from the undersea wellhead, which BP officials said was releasing roughly 210,000 gallons of oil a day.

But then, a technical book he co-wrote three years ago -- "Particle Image Velocimetry: A practical Guide" -- caught the eye of National Public Radio.

On May 13, almost three weeks after the blowout, NPR called Wereley to ask if he could examine a grainy, 30-second underwater video and tell them how much oil was flowing from the well using velocimetrics.

Wereley spent two hours breaking down the video into individual frames and making the calculations, basically by measuring images of the flow pixel by pixel.

His estimate, 3.9 million gallons of oil per day, or 20 times BP's amount, shot around the globe, attracting the attention of major news media the following day.

This past Wednesday, Wereley testified before Congress about his findings. Still, a month later there is no consensus about how much oil is being released into the Gulf. More data, including better quality video, is needed, Wereley said.

(3)  Huge underwater plumes of oil in the Gulf of Mexico
http://www.channel4.com/news/articles/business_money/warnings+of+giant+gulf+oil+leak+aposunderwater+plumesapos/3653497

Warnings of giant Gulf oil leak 'underwater plumes'

By Julian Rush

Updated on 19 May 2010

Scientists have found huge underwater plumes of what they think is oil in the Gulf of Mexico, which may be evidence far more oil is leaking from BP's broken well than current estimates suggest.

The descovery may also explain why so little has come ashore, even though the thin surface slick is over 100 miles long and 40 miles wide.

The researchers from the University of Southern Mississippi on board the RV Pelican abandoned their original mission, which was to map methane hydrates in the seabed, to sample the ocean at various depths.

"There is a shocking amount of oil in the deep water", one of the scientists, Samantha Joye, told the New York Times.

The team found evidence for oil in three or four deep layers, including one 10 miles long, 3 miles wide and 300 feet thick in places. They found them in the deeper water - the shallowest at around 2,300 feet, the deepest, near the sea floor at about 4,200 feet.

They also found the underwater oil plumes depleted the oxygen in the water, which they fear may endanger marine life.

But the head of the National Oceanic and Atmospheric Administration (NOAA) says it is too soon to say they definitely found oil.

Jane Lubchenco said "no definite conclusions have been reached by this research team about the composition of the undersea layers they discovered. The hypothesis that the layers consist of oil remains to be verified."

If it is oil, it may mean far more oil is gushing from the well than the 5,000 barrels a day currently taken as the best estimate, made from analysing satellite images of the surface slick.

Some scientists who have examined the short video, released by BP, of oil leaking from the broken pipe have estimated it might be between 25,000 to 80,000 barrels a day.

BP has refused requests to release any more video, making it difficult for the scientists to confirm their calculations.

And scientists have asked BP if they can send Remote Operated Vehicles to the site of the leak to measure the flow, but BP has refused, saying they would get in the way and might jeopardise the efforts to stem the flow.

(4) Independent investigator Robert Bea says accident was preventable; safety compromised

Horizon rig: What went wrong?

Independent investigator says accident was preventable; safety compromised

By Lisa Myers and Rich Gardella

updated 7:40 p.m. ET May 21, 2010

http://www.msnbc.msn.com/id/37279113/ns/nightly_news/

An independent researcher investigating the Deepwater Horizon oil rig accident has released preliminary findings, based on accounts from rig employees and others, that the accident was the result of a series of mistakes and flawed decisions, which had compromised safety.

The researcher, Dr. Robert Bea, came to the nation's capital this week with that message about what went wrong on the Deepwater Horizon rig.

Bea's been an engineer for 57 years, with experience investigating past disasters. An engineering professor at the University of California at Berkeley, he's a co-founder of its Center for Catastrophic Risk Management, and is the Center's principal researcher. After Hurricane Katrina, he helped lead an independent investigation into why the levees in New Orleans collapsed.

On Thursday, Bea had a closed-door meeting in Washington with other members of the Deepwater Horizon Study Group, a group he's taken the lead in assembling to investigate the oil spill accident. The group consists of professionals from industry and government, many participating under conditions of confidentiality.

"There is no doubt," Bea told NBC News Senior Investigative Correspondent Lisa Myers in an interview this week, "that safety was compromised."

With few witnesses and officials with direct knowledge of what happened speaking publicly, and the results of official investigations months if not years away, Bea says that conclusion comes directly from information he and his group have already received from oil industry employees, including people who were on the Deepwater Horzizon platform when the accident occurred.

Bea says the information includes interviews with 50 people with direct knowledge -- many under conditions of confidentiality -- and recordings of audio transmissions from the rig. Bea says the materials total 400 hours, stored in the group's database on a UC Berkeley server.

Bea has spoken publicly before, but yesterday, one month after the accident, released a report of his preliminary analyses based on the information gathered.

"This disaster was preventable," Bea writes, "had existing progressive guidelines and practices been followed."

The report lists what Bea believes are seven "Steps Leading to Containment Failure," also known as "blowout," including:

*improper well design
*improper cement design
*early warning signs not properly detected, analyzed or corrected
*removing the pressure barrier -- displacing drilling mud with sea water 8,000 feet below the drill deck
*flawed design and maintenance of the final line of defense – the blowout preventer

One of the early warning signs was belches or 'kicks' of methane gas, which came up from the depths of the well in the weeks before the accident. The gas was in slushy ice forms called methane hydrates -- but was potentially explosive. One incident was serious enough to shut the well down.

"They had a catastrophic loss of drill fluid into the formation," Bea says. "Gas got to the surface. They had to bring the rig to cold operation."

From what he's learned, Bea says, workers thought the successful response to that incident had fixed the gas problem in general.

Bea also says "drilling and well completion operations did not meet industry standards." He says the well was considerably behind schedule and some of what proved to be bad decisions were designed to save time and money at the expense of safety. Below is an excerpt from Dr. Bea's interview with Lisa Myers:

Dr. Robert Bea: There are time pressures that are extremely intense. And there are economic pressures that are extremely intense.

Lisa Myers: So you saw a lot of cutting corners.

Dr. Robert Bea: Sure.

Bea says the worst mistake was the decision to remove heavy drilling fluid, called "mud," from the drill column, as part of the end of the normal process to close down the well. Fine if the cements seals were working, he says. Potentially catastrophic if they weren't.

Lisa Myers: "The critical decision was the one to remove that heavy mud?"

Dr. Robert Bea: "That's based on everything we know. Yes."

The biggest underlying problem of all, Bea says, is that "we horribly underestimated the risk."

Throughout his interview with NBC News, Bea refers to the offshore drilling community as "we." He himself was once a consultant for BP, the lease operator and owner of the oil well at the Deepwater Horizon rig. He has worked with government regulators of the oil drilling industry for decades. Some employees on the Deepwater Horizon the day of the accident are friends and former colleagues.

Bea says all the companies involved in the Deepwater Horizon accident probably bear some responsibility, but that most of the blame rests with BP and the federal government, because they failed to properly oversee the project.

"These are not bad people," Bea says emphatically. "We're just doing dumb things."

Lisa Myers: This report is damning.

Dr. Robert Bea: I hope not. I hate damning... I hope it's constructive... I want learning to come from it. Not just more damn pain. There's enough of that around.

After reviewing Bea's report, BP spokesman Andrew Gowers wrote in a statement to NBC News that the company is surprised Bea has so quickly reached any conclusions, based on incomplete information. BP says with many investigations going on and so much evidence to be examined, "we think it appropriate to await those findings before further comment on the causes of this terrible accident."

Bea says he's been down this road before, after Hurricane Katrina.
He says the revelations about why the levees failed then are similar to the revelations about why the oil rig failed now.

"We had this long slide down this slippery slope of incremental bad decisions [regarding the levees]," Bea says. "This is following the same trail."

"I think we've got the outline of the picture puzzle," Bea says. "The details are still missing. But I think we got the outline right."

(5) Drilling deeper increases risks of crushing water pressure and explosive methane gas

http://www.google.com/hostednews/ap/article/ALeqM5iJEtui-hzwaWwmm69UWEJPINdD3gD9FLBR600

Rush to drill deeper carries added risks

Drilling deeper increases risks of crushing water pressure and explosive methane gas.

By Mike Baker and Jason Dearen, AP

Wed, May 12 2010

http://www.businessreport.com/news/2010/may/12/rush-drill-deeper-carries-added-indt1/
http://www.washingtonpost.com/wp-dyn/content/article/2010/05/12/AR2010051200439.html
http://www.mnn.com/earth-matters/wilderness-resources/stories/rush-to-drill-deeper-carries-added-risks

NEW ORLEANS — The explosion of the Deepwater Horizon oil rig illustrates the energy industry's push to drill in ever deeper waters in search of huge oil deposits, despite the mammoth risks and unique challenges associated with exploration in such a hostile environment.

The lure of the deep is driven by technological advances that make previously inaccessible oil now reachable, and dwindling supplies at shallower depths due to years of exploration. High energy prices and lucrative government incentives have also made it more financially feasible.

"That's where the oil is," said Eric Smith, associate director of Tulane University's Energy Institute. "You can't find any oil any cheaper anywhere else."

But the work is highly technical. In mile-deep seas, where BP PLC's Deepwater Horizon rig was plumbing for oil in an ocean canyon, the work is done in total darkness and near-freezing temperatures. Water pressure is enough to crush a submarine, and the explosive methane gas that likely ignited on the Deepwater Horizon can be much more damaging if not properly controlled.

"The deep water is way too risky," said Kieran Suckling, executive director of the Center for Biological Diversity, a legal advocacy group that opposes such drilling.

Gulf of Mexico oil is a crucial part of the U.S. energy supply. While land-based production has steadily declined, output from the Gulf has doubled over the past two decades, surpassing that of any state including Texas and Alaska.

More companies are developing projects in mile-deep seas, and most of the oil produced in the Gulf now comes from sites more than 1,000 feet below the water's surface.

Drilling applications approved by the federal government last year went to wells at an average depth of 2,114 feet — triple what was seen just a decade ago, according to an Associated Press analysis of data from the federal Minerals Management Service.

This expansion of drilling ever deeper was fueled by the 1995 Deep Water Royalty Relief Act, which exempts companies from paying a percentage of royalties to the government on oil and gas found.

"Prior to that, the Gulf was becoming a dead sea in terms of exploration activities," said David Dismukes, director of policy analysis at Louisiana State University's Center for Energy Studies. "The relief act stimulated a lot of activity ... and concerns about environmental safety in the Gulf."

Politically, U.S.-produced oil from the Gulf of Mexico is an easier sell than continued reliance on foreign sources or tapping pristine Alaskan wilderness.

"In terms of oil that's available to us, it's either imported from places where it's bountiful," Smith said, "or we find deep water deposits off the coast of Africa, Brazil and the Gulf of Mexico."

That is widely expected to continue despite the Deepwater Horizon disaster, which killed 11 workers and has already fouled the Gulf with 4 million gallons of crude.

"This country's pretty well committed to oil and gas, and nobody's really happy when the price goes through the roof," said Philip Johnson, a petroleum engineering professor at the University of Alabama. "My suspicion is that we're going to proceed with production out of the Gulf of Mexico — and that means we're going to keep trying to get farther and farther offshore."

But the conditions down there have challenged oil companies to come up with technological solutions.

Beyond about 1,500 feet, sunlight is unable to penetrate. The temperature at 5,000 feet in the Gulf is about 40 degrees. The water pressure is about 2,300 pounds per square inch, conditions that can damage hydraulic systems or cause leaks.

A remotely operated underwater vehicle designed for 5,000 feet of water is "a whole world of different engineering" than one used at 500 feet, said Louisiana State University oceanographer Robert S. Carney. Yet companies must rely on those vehicles to detect or repair leaks and other problems.

Blowouts like the one that hit the Deepwater Horizon are also more powerful at extreme depths. They can thrust gas, oil, water and debris toward the surface with incredible force.

In the intense pressure and cold of the deep, methane hydrates exist in a slushy, crystalline form. But as methane rockets upward in a blowout, passing into lower-pressure zones, it converts to a gaseous state and gains tremendous force.

The use of heat in cementing, or sealing a well, which was under way prior to the blast, can destabilize methane hydrates at extreme depths. Halliburton Co., which was doing the cementing of the Deepwater Horizon well, acknowledged as much in an industry presentation last year, calling the risks "a challenge to the safety and economics."

Ultra deepwater rigs like Horizon are also required to have more robust blowout preventers that can withstand the intense pressure. The rig's preventer was designed to withstand 15,000 pounds of pressure per square inch, a standard for drilling at these depths. At an oil industry conference in Houston last week, there was an advanced 20,000-pound model on display.

Investigators trying to pinpoint a cause of the explosion are looking at both the blowout preventer and Halliburton's cementing. Interviews with rig workers conducted as part of BP's internal investigation indicate a bubble of methane escaped from the well and rocketed up the drill column, expanding as it approached the surface.

Transocean Ltd., which owned the rig and leased it to BP, is the major player in deepwater drilling, which 40 rigs worldwide working 5,000 feet down or greater. It said in a statement that the company's first commitment is safety.

"The company continues to strive and apply its core safety tools consistently across all its operations around the world," Transocean said.

The ongoing struggle to cap the leak also underscores the challenges when things go wrong far below the surface. BP's initial attempt to cap the underwater gusher with a 100-ton house-sized box designed to funnel the oil to a tanker ship was scrapped due to the formation of an icy slush that clogged it.

Company officials are now focused on positioning a smaller containment vessel, known as a top hat, or plugging a portion of the leak with junk. Those methods are long shots, however, never tried at such depths, and it could be up to three months before a relief well shuts off the leak entirely.

"Think of this same thing happening at less water depth: We could have easily sealed that well," said Satish Nagarajaiah, a Rice University engineering professor who focuses on offshore structures. "Now the challenges are bigger."

As oil companies continue to push the boundaries into new frontiers, they encounter unknowns: different sands, different hydrocarbons, different gas pressures. There's less of a history that can be used to assess problems that drilling may encounter.

"There's a real change when you go from conventional deepwater to much greater depths," said Tyler Priest, a University of Houston professor and expert on the history of offshore petroleum. "There are unknowns."

Baker reported from Raleigh, N.C.