Romancing the Ice: The Energy Potential of Gas Hydrates

Abstract:The new Integrated Deep Drilling Program will spend big money; use big drillships to answer a lot of questions about the future energy potential of 'the ice that burns.'

Analysis:Earlier this month the JOIDES Resolution, a 469-foot-long drilling/coring vessel, completed a two-month scientific expedition in the Pacific Ocean off Oregon. The voyage – made to investigate the origin and distribution of methane (gas) hydrates on and beneath the ocean floor – was part of the Ocean Drilling Program (ODP), a decades-old international oceanographic research effort funded mainly by the U.S. Government.

The Oregon cruise, the 208th leg of the ODS since it was organized in the 1970s, was one of the last the vessel, a mobile drilling rig refitted for science, will make. The program – in its current iteration, at least – will end in about a year. It will be succeeded on Oct. 1, 2003 by a much larger, more generously funded program, the Integrated ODP (IODP), and two new drilling/coring ships will replace the JOIDES Resolution. But more about that later.

It's somewhat fitting that this most recent ODP leg involved efforts to solve the gas hydrates mystery, since one of the new outfit's three principal scientific themes during the next 10 years will be the deep biosphere and the sub-seafloor ocean, with initiatives aimed at fluids and gases occupying and flowing on the sea floor. Almost from the beginning, major focus will be placed on gas hydrates.

Hydrates? They're cage-like lattices of ice, inside of which molecules of methane and other hydrocarbon gases are trapped. If brought to the surface quickly enough, they can be set afire, since methane gas leaks, or disassociates, from the ice under ambient temperature and atmospheric pressure. Called "the ice that burns," they are found in two general geologic settings:

  • Beneath the ocean floor at water depths greater than about 1,640 feet (500m), where low temperatures and high pressures dominate. Offshore deposits are found on the seafloor, and can be several hundred feet thick below that.
  • On land in permafrost regions where they form due to sustained cold temperatures in shallow sediments.

  • Scientists have known about naturally occurring gas hydrates for more than a century, but drew little or no interest until about 20 years ago, when they began to form artificially inside pressurized gas pipelines under cold conditions, such as in snow country or in deep water. Unmitigated, artificial hydrates present flow assurance problems in pipelines, both onshore and offshore. They also can block flow in risers, subsea manifolds and wellheads, and other deepwater production equipment. There, the costs of plugged wells and pipe can be staggering. The petroleum industry, then, became very interested in both prevention and inhibition of such hydrates.

    Scientists and researches have a different view of hydrates. For one thing, they represent a potential source of unlimited energy. For another, they pose a potentially disastrous threat to the world's climate.

    Due partly to results from ODP cruises during the 1980s and 1990s, as well as to research conducted by other organizations, vast fields of gas hydrates have been detected around most of the world's continental margins. Straight-line projections estimate the natural gas potential of the world's hydrates at something like 400,000,000 trillion cubic feet (tcf). It's an almost laughable figure, until you consider lab tests reveal that 1 cubic centimeter (cc) of gas hydrate contains about 158 cc of methane, mainly because high seafloor pressures pack the gas molecules more densely inside the ice crystals.

    In 1997, the U.S. Geological Survey (USGS), basing projections on field studies made by the ODS and other groups, estimated that the in-place gas resource within U.S. hydrate accumulations alone totals about 200,000 tcf. That dwarfs the estimated 1,400 tcf of conventional U.S. gas – both already recovered and in reserve. To put it somewhat in perspective, the USGS says a 30-mile by 90-mile hydrates accumulation in the Atlantic Ocean on the Blake Plateau off Georgia and the Carolinas could contain enough methane to fill all U.S. natural gas needs for more than 70 years. Potentially, say the scientists, there could be more energy in hydrates alone than in all other known fossil fuels.

    So much for the energy potential. Then, consider the potential climatic threat they present. It, too, is mind-boggling.

    When exposed to higher temperature and lower pressure, seafloor hydrates literally "melt," allowing the contained gases to escape into the water column and then, presumably, into the atmosphere. Some scientists believe that unstable ocean-bottom hydrates can and do disassociate with changes in ocean floor temperatures, creating massive landslides on the continental slope. Not only might such landslides inflict major damage to pipelines, communications cables and other bottom-supported structures like subsea production systems and fixed platforms, but the disassociated methane also might escape into the atmosphere. They also point out that methane is 10 times more of a "greenhouse" gas than carbon dioxide, which draws most of the current blame for global warming.

    Until very recently, the petroleum industry's interest in the energy potential of hydrates had gotten nowhere – slow. Even today, many oil company futurists still doubt that hydrates hold the estimated energy equivalents described by outfits like the USGS. They also point out that no evidence exists of any offshore pipeline or structure ever having been damaged by landslides activated by hydrate disassociation.

    But it's common knowledge that even so, many major oil companies do have full-time people keeping a close eye on hydrates research. And a few companies actually are conducting their own research into the energy potential angle. Houston-based Anadarko Petroleum and California-based Chevron Texaco, for example, are both conducting tests on Alaska's North Slope, where large, near-surface accumulations of hydrates have been identified during conventional oil and gas development. Anadarko will drill and study three hydrate core holes this winter and study them for several years, with the goal of producing gas from onshore hydrates safely and economically, if such is possible.

    Let's go back to the IODP. That program, when fully operational in 2008, will be significantly larger than its precursors, with an annual operating budget of about $160 million, three times that of the ODP. As organized, the lead agencies of the IODP will be this country's National Science Foundation (NSF), which also led the ODP, and a new Japanese organization with an ungainly name: "the Ministry of Education, Culture, Sports, Science and Technology," or MEXT, for short. The upshot is that the U.S. and Japan will be the lead agencies, with other nations having access to participate in the remaining one-third of the IODP's activities.

    Why Japan? Because that country is vitally interested in non-conventional energy sources, for obvious reasons. The Japanese have done a fair amount of hydrates research themselves, including drilling some test core holes around the Home Islands.

    To emphasize how interested they really are, the Japanese government is supplying a massive drilling vessel, the Chikyu, for the IODP's exclusive use. That vessel, whose hull was launched recently from a Japanese shipyard, will be a whopping 690 feet (210 m) long, 125 feet (38 m) wide, and displace 57,000 tons. Valued at about $590 million, it will be fitted with a drilling system, derrick and blowout preventer stack that will allow it to drill, through a deep-sea riser, core holes of up to 4.34 miles (7 km) below the seafloor in water depths of up to 2.4 miles.

    However, the Chikyu won't be ready to drill for the IODP until late 2007 or early 2008, so the NSF will soon take bids for a new drilling vessel to be used for riserless coring. Though none has been chosen, the ship likely will be an existing vessel, refitted for coring instead of newly built. That vessel probably won't be ready for use until 2005, so the JOIDES Resolution just might get a short new lease on life.

    What this means is that there's a growing interest in gas hydrates that promises to answer some basic questions during the next 8-12 years. Gas hydrate research by IODP will aim to quantify the rate at which methane is generated, determine the link between the gas and the organic carbon source material, as well as the microbial community involved, quantify the rates of gas migration through the sediments, and establish the mechanisms of gas entrapment in seafloor sediments. It also will try to determine whether, in fact, hydrates do play a role in submarine landslides and global climate change.

    Look for increased industry involvement, as well. If hydrates are found to be a true source of alternative fossil energy by IODP and other initiatives, the industry's offshore segment, with its decades of experience in producing conventional hydrocarbons from the deep-sea environment, would be the mostly likely provider of tools and technology needed to produce methane from hydrates safely and cost-effectively. It's a wide-open field.

    Who knows? One day, the world's energy could be supplied not by oil companies, but by "hydrate companies."