Earth Science Scientists Create, Study Methane Hydrates in “Ocean Floor” Lab

Discussion in 'Earth Science' started by mscbkc070904, Mar 15, 2005.

  1. mscbkc070904

    mscbkc070904 Premium Member

    Data may help develop strategies for mining natural gas locked up in seafloor sediments

    March 13, 2005

    SAN DIEGO, CA - Scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have recreated the high-pressure, low-temperature conditions of the seafloor in a tabletop apparatus for the study of methane-hydrates, an abundant but currently out-of-reach source of natural gas trapped within sediments below the ocean floor. Michael Eaton, a Stony Brook University graduate student working for Brookhaven chemist Devinder Mahajan, will present a talk outlining the use of the apparatus for the creation and study of methane hydrates during a special two-day symposium co-organized by Mahajan at the 229th National Meeting of the American Chemical Society in San Diego, California. The talk is scheduled for Sunday, March 13, at 3:05 p.m. in room Madeleine C-D of the Hyatt Regency.

    For one thing, methane hydrates -- which are ice-like cages made of water molecules surrounding individual methane molecules -- are only stable at the very low temperatures and high pressures present at the ocean floor. “If you try to bring it up, these things fizzle and decompose, releasing the trapped methane,” Mahajan says.

    So a multi-agency team led by the Department of Energy -- as part of its mission to secure America’s future energy needs -- is trying to learn about the conditions necessary for keeping hydrates locked up so they can be extracted safely and tapped for fuel.

    Mahajan’s group has built a vessel that mimics the seafloor temperature and pressure conditions, where they can study the kinetics of methane hydrate formation and decomposition. Unlike other high-pressure research vessels, the Brookhaven apparatus allows scientists to interchange vessels of different volumes, study even fine sediments, and visualize and record the entire hydrate-forming event through a 12-inch window along the vessel. In addition, mass-balance instrumentation allows the Brookhaven group to collect reproducible data in the bench-top unit. Even better, Mahajan says, they can study the kinetics in actual samples of sediment that once contained hydrates -- as close to the natural conditions as you can get in a lab.

    “You fill the vessel with water and sediment, put in methane gas, and cool it down under high pressure. After a few hours, the hydrates form. You can actually see it. They look like ice, but they are not. They are stable at 4 degrees Celsius,” he explains.

    One further advantage of doing this work at Brookhaven Lab is that the scientists can use the National Synchrotron Light Source -- a source of intense x-rays, ultraviolet, and infrared light -- to measure physical characteristics of the sediments under study. Using x-ray computed microtomography, the scientists gain information about the porosity and other physical characteristics that may affect the availability of nucleation sites where hydrates can form.

    Such data about hydrate formation in natural host sediment samples are scarce. By studying different samples and learning what combinations of pressure and temperature keep the methane locked up, the scientists hope to identify ways to compensate for the changes the hydrates experience as they are brought to the ocean’s surface so they can be extracted with a minimum loss. The comparisons of different sediment samples might also help pinpoint the most abundant sources of locked-up methane.

    “It may be at least a decade before we can even think about mining these deposits, but answering these fundamental questions is certainly the place to start,” says Mahajan, who holds a joint appointment as a Stony Brook University professor. “This is a very important issue tied to our future national energy security.”

    Source: www.bnl.gov
     
  2. mscbkc070904

    mscbkc070904 Premium Member

    I was wandering if methane is used as a alternate energy source? If so, how effective is it compared to petro's used now?

    BUt if they are looking at mining these deposits, what is the overall structure of the sea floor to do such a thing? Plus, if mining those built up deposits, if depleted, could it cause cave ins or plate slips so forth?
     
  3. bodebliss

    bodebliss The Zoc-La of Kromm-B Premium Member

    Methane is natural gas, swamp gas, propane, etc. They call it methane in it's unrefined form.
     
  4. sweetpea

    sweetpea New Member

    The methane hydrates are so easily destabilized, that the very extraction process (drilling, etc.) can create enough heat to melt and release the methane, losing it to the ocean.

    I have been studying in this area in the past 6 months, and it is an interesting challenge, but one that most definitely needs to be addressed, just as heavy-crude production needs to be addressed.

    Definitely will be interesting to watch the developments in this area.
     
  5. Zsandmann

    Zsandmann Premium Member

    Hi sweetpea!

    You sound like a geologist, or else you are just interested in geological processes. I am a geophysicist so if you want we can talk more on topics such as this one. I posted a thread about these gas hydrates and how they may be one cause of planes disappearing in the Bermuda Triangle, search it out. Also, as far as extraction like you were speaking of, I have seen studies where they have mounted a dome over the drill so as the bubbles of methane are released they are funneled up and collected. There is so much potential fuel in the deposits we really should look into them futher.

    Z
     
  6. sweetpea

    sweetpea New Member

    Yes, they've started employing some new technology to mitigate the heating that takes place during drilling through the zones, but what is still lacking is a reliable and repeatable zonal isolation technique across a methan hydrate zone. Since cement, which is the typical Z.I. product is extremely exothermic, it tends to melt the hydrates as it cures. There are some more optimal products, such as foamed cement containing nitrogen, which is less exothermic and also tends to expand instead of shrink like normal cement does. There needs to be a step-wise improvement in this area before these zones can be repeatedly completed successfully. A brand new method for these zones.

    Look forward to visiting with you!
     
  7. Zsandmann

    Zsandmann Premium Member

    Thats very interesting. I did not realize that they would do zone isolation on the hydrates, I was just expecting them to induce a mass heating to free them since they freely flow, and the density and pressure gradients should force them out through the seafloor rather easily.

    What is your personal experience in the field? I.e. are you a student or are you in industry or acedemia?
     
  8. sweetpea

    sweetpea New Member

    I'm in industry.

    What you may be missing in considering this is that the hydraulic pressure of the seawater above the zone would not allow this very efficiently. The methane hydrate zones are relatively close to the seabed in the first place. Remember, they are actually considering pumping GHG's to the bottom of the sea floor for containment, so if you released the methane it would do the same thing - pool - or just slowly bubble to surface (which I believe there have been reports of this happening in locations in the Indian Ocean since the December quake). So you have to have a riser (production casing) to produce them efficiently. And you have to isolate the zone from leaking up the annular space between the casing and the wellbore.