On a Rare Expedition, UT Geoscientists Recover a Possible Energy Resource

 

 

From the helideck of the drilling vessel Helix Q4000, the horizon is a straight line that appears to go on forever, separating the ocean from a mosaic of vibrant purples, oranges, and reds. Dolphins slip in and out of the waters. Fish circle the drill pipe.

It seems like a peaceful place to relax and watch the sunrise, but for the crew aboard the Helix Q4000, floating in the Gulf of Mexico 150 miles off the coast of Louisiana, work never stops.

The vessel is about the size of a football field, but it’s packed with shipping containers, cranes, and drill pipes so it’s hard to walk more than 10 feet without running into something. Crewmembers dressed in hard hats, glasses, and fire-resistant coveralls man massive drills and shuffle in and out of shipping containers, adding to the ever-present buzz of a 24/7 work schedule. If workers don’t look up or watch where they’re walking, they might step under a crane or trip over a metal railing, injuring themselves, or worse.

Such dangers were part of everyday life for a group of Jackson School scientists and graduate students and colleagues from other institutions like Ohio State University in May. Their mission was to extract methane hydrate, a substance seen as a potential future energy source, from below the ocean floor. In 2014, the Department of Energy selected UT to retrieve and conduct research on this little-understood substance. The May 2017 expedition was the first of two drilling expeditions in this $80 million, six-year project, one of the largest, most ambitious research projects in UT history. “This is probably the biggest grant that UT has ever had from federal funding,” says professor Peter Flemings, the project leader. “We’re working on a totally different scale.”

Though scientists can create methane hydrate in a lab, little is known about the substance in its natural state. Earth is rich with methane hydrate, but it’s found naturally in high-pressure, low temperature places, like in Arctic permafrost and under the ocean floor. It’s unstable on the surface, so engineering technology that retrieves and maintains methane hydrate at the right pressure and temperature was key to the expedition’s success. This extraction process has rarely been done before due to the difficulty and expense of creating the right extraction machinery. In 2013, Japan extracted the first gas from deposits of methane hydrate in the seafloor, but the expedition ended early due to sand clogging their machinery. Earlier this year, Japan and China reported successful recovery of methane hydrate from the seafloor. The UT expedition was going to acquire the first samples of subsurface methane hydrate from the Gulf, and failure would be costly. Just a day of drilling cost about $350,000.

The 24-day expedition consisted of 12 days of drilling, in which the crew used a coring tool to cut out a cylinder of sediment from the seafloor, about a mile and a quarter below sea level. The cylinder was then tucked inside a steel vessel that maintained intense pressure on the sediment, so the methane hydrate within would remain in its natural condition. The plan was to retrieve these cores from two separate holes. The first half of the trip was brutal. Flemings and his team of engineers, researchers, and graduate students worked 12-hour shifts, drilling, collecting, and analyzing data, but each attempt was fruitless. They had no cores. “We kept thinking this entire project was a failure,” says Tiannong “Skyler” Dong, a graduate student who worked on the rig. “The morale was very low. We put so much time and effort into this project.”

Dispirited, the team took the coring tool out of the water. They pulled it apart and modified it some, hoping to have better luck in the second hole. When they started drilling again, the mood began to shift as they retrieved core after core. At the end of the trip, they were able to return to UT with 21 pressurized cores. “We don’t fully understand exactly why things turned around so quickly,” Flemings says. “We’re still trying to work that out. But the net result was that although we got zero in the first half, we then got enough core because our success rate was so high [in the second half].”

The cores are now housed in a one-of-a-kind laboratory in the Jackson building, where they are being studied by the UT team. Some of the cores are being sent to other universities that have requested samples for research. Built specifically for this project, the lab is kept at temperatures of about 4 degrees celsius. “Keeping each of these at the pressure they’re at is not only important scientifically but for safety,” says Peter Polito, the lab director. The lab has taken precautions to ensure that if something goes wrong, the methane will be funneled out of the building.

The next phase of the process is to study these cores. The team is working to understand everything they can about this substance, such as its permeability and how the substance changes as pressure is lowered. By lowering their pressure, or “degassing” the methane hydrate cores, scientists can measure the amount of methane, the main component of natural gas, released. Methane is a less carbon-intensive fuel than other fuels. “Methane is a whole lot cleaner than coal, and somewhat cleaner than oil,” Flemings says. “So it’s a healthier fuel.”

Its abundance and high energy content make it attractive as an energy source. The Department of Energy speculates that the energy content of methane in methane hydrate may exceed the combined energy content of all other known fossil fuels. The DOE aims to determine if there is a way to extract the methane from the cores that is economically feasible. “The DOE is tasked with many things, and among those things is to say, ‘In the future, 40 or 50 years from now, we have to make sure we have a reliable energy source. How do we do that?’” Flemings says. “They’re saying right now it’s technologically unfeasible to go and harvest this methane, but if we start the science now, maybe it’ll be feasible in the future.”

For now, the research continues. Flemings will lead another expedition consisting of 56 days of drilling set for 2019, followed by more research. Until then, Flemings and his team will continue to unravel the mysteries and potential of methane hydrate. “The reality is we’ve essentially done no science yet,” Flemings says. “If UT is successful, it’s what happens in the next couple of years that’s really important.”

Photos by Anton Caputo 

 
 
 

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