Featured Research

from universities, journals, and other organizations

Researchers reinforce gas hydrate strategy: New study goes deeper in proving simple technique to pinpoint valuable energy source

Date:
September 20, 2011
Source:
Rice University
Summary:
A new study expands upon previous research to locate and quantify the amount of methane hydrates -- a potentially vast source of energy -- that may be trapped under the seabed by analyzing shallow core samples. The paper should silence the skeptics, the researchers said.

Rice University chemical engineer George Hirasaki, left, and graduate student Sayantan Chatterjee have expanded upon techniques to locate vast reserves of gas hydrates under the seafloor.
Credit: Jeff Fitlow/Rice University

Their critics weren't convinced the first time, but Rice University researchers didn't give up on the "ice that burns."

A paper by a Rice team expands upon previous research to locate and quantify the amount of methane hydrates -- a potentially vast source of energy -- that may be trapped under the seabed by analyzing shallow core samples. The paper published by the Journal of Geophysical Research--Solid Earth should silence the skeptics, the researchers said.

Chemical engineers George Hirasaki and Walter Chapman and oceanographer Gerald Dickens headed the team.

In 2007, Hirasaki and former graduate student Gaurav Bhatnagar theorized that gas hydrates -- methane that freezes at low temperatures and high pressures -- could be detected via transition zones 10 to 30 meters below the seafloor near continental shores; at that level, sulfate (a primary component of seawater) and methane react and consume each other.

As sulfate migrates deeper into the sediment below the seafloor, it decreases in concentration, as evidenced by measurements of pore water (water trapped between sediment particles) from core samples. The depth at which the sulfate in pore water gets completely consumed upon contact with methane rising from below is the sulfate-methane transition (SMT) zone.

In the 2007 paper, Bhatnagar argued the depth of this transition zone serves as a proxy for quantifying the amount of gas hydrates that lie beneath; the shallower the SMT, the more likely methane will be found in the form of hydrates in abundance at greater depth.

Though hydrates may be as deep as 500 meters below the seafloor, locating deposits through shallow coring using such proxies should aid selection of deep, expensive exploratory drilling sites, the researchers said.

The controversy that followed the publication of the original paper focused on sulfate consumption processes in shallow sediment and whether methane or organic carbon was responsible. Skeptics felt the basis of Bhatnagar's model, which assumes methane is a dominant consumer of pore-water sulfate, was not typical at most sites.

"They believed that particulate organic carbon (primarily from ocean-borne dead matter) was responsible for reducing sulfate," said Sayantan Chatterjee, lead author of the new paper. "According to their assumption, the depth of the SMT, upward methane flux and hydrate occurrence cannot be related. That would nullify all that we have done."

So Chatterjee, a fifth-year graduate student in Hirasaki's lab, set out to prove the theory by bringing more chemical hitchhikers into the mix.

"In addition to methane and sulfate profiles, I added bicarbonate, calcium and carbon isotope profiles of bicarbonate and methane to the model," Chatterjee said. "Those four additional components gave us a far more complete story."

By including a host of additional reactions in their calculations on core samples from the coastline of Oregon and the Gulf of Mexico, "we can give a much stronger argument to say that methane flux from below is responsible for the SMT," said Hirasaki, Rice's A.J. Hartsook Professor of Chemical and Biomolecular Engineering. "The big picture gives more evidence of what's happening, and it weighs toward the methane/sulfate reaction and not the particulate organic carbon."

The work is important not only for a natural gas industry eyeing an energy resource estimated to outweigh the world's oil, gas and coal reserves -- as much as 20 trillion tons -- but also for environmental scientists who see methane as the mother of all greenhouse gases, Hirasaki said.

"There's a hypothesis by Dickens that says if the ocean temperature starts changing, the stability of the hydrate changes. And instability of the hydrates can release methane, a more severe greenhouse gas than carbon dioxide.

"That can create more warming, which then feeds back on itself," Hirasaki said. "It can have a cascade effect, which is an implication for global climate change."

Chatterjee had the chance to discuss his results with his peers in July at the seventh International Conference on Gas Hydrates in Edinburgh, Scotland, where he presented a related paper that focused on the accumulation of hydrates in heterogeneous submarine sediment.

Chatterjee said a number of eminent experts commended him after his talk. "I got a chance to show my recent findings on our 2-D model. This will simplify the search and locate isolated pockets where hydrates have accumulated in deep ocean sediments," he said.

Chatterjee's conference paper was awarded a first prize at the prestigious Society of Petroleum Engineers' Young Professionals meeting and second at the Gulf Coast Regional student paper competition.

Co-authors include Chapman, the William W. Akers Professor of Chemical Engineering; Brandon Dugan, an assistant professor of Earth science; Glen Snyder, a research scientist in Earth science; Dickens, a professor of Earth science, and Bhatnagar, all of Rice.


Story Source:

The above story is based on materials provided by Rice University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Sayantan Chatterjee, Gerald R. Dickens, Gaurav Bhatnagar, Walter G. Chapman, Brandon Dugan, Glen T. Snyder, George J. Hirasaki. Pore water sulfate, alkalinity, and carbon isotope profiles in shallow sediment above marine gas hydrate systems: A numerical modeling perspective. Journal of Geophysical Research, 2011; 116 (B9) DOI: 10.1029/2011JB008290

Cite This Page:

Rice University. "Researchers reinforce gas hydrate strategy: New study goes deeper in proving simple technique to pinpoint valuable energy source." ScienceDaily. ScienceDaily, 20 September 2011. <www.sciencedaily.com/releases/2011/09/110915113740.htm>.
Rice University. (2011, September 20). Researchers reinforce gas hydrate strategy: New study goes deeper in proving simple technique to pinpoint valuable energy source. ScienceDaily. Retrieved September 16, 2014 from www.sciencedaily.com/releases/2011/09/110915113740.htm
Rice University. "Researchers reinforce gas hydrate strategy: New study goes deeper in proving simple technique to pinpoint valuable energy source." ScienceDaily. www.sciencedaily.com/releases/2011/09/110915113740.htm (accessed September 16, 2014).

Share This



More Earth & Climate News

Tuesday, September 16, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Researchers Explore Shipwrecks Off Calif. Coast

Researchers Explore Shipwrecks Off Calif. Coast

AP (Sep. 16, 2014) Federal researchers are exploring more than a dozen underwater sites where they believe ships sank in the treacherous waters west of San Francisco in the decades following the Gold Rush. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Isolated N. Korea Asks For International Help With Volcano

Isolated N. Korea Asks For International Help With Volcano

Newsy (Sep. 16, 2014) Mount Paektu volcano in North Korea is showing signs of life and there's not much known about it. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

      Technology News



      Save/Print:
      Share:

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile: iPhone Android Web
      Follow: Facebook Twitter Google+
      Subscribe: RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins