DOE-Sponsored Expedition Confirms Resource-Quality Gas Hydrate in the Gulf of Mexico
Leg II Initial Scientific Reports Now Available
On May 6, 2009, the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL)in collaboration with the U.S. Geological Survey (USGS), the U.S. Minerals Management Service, an industry research consortium led by Chevron, and others completed a landmark gas hydrate drilling expedition. The objective of the 21-day expedition was to confirm that gas hydrate can and does occur at high saturations within reservoir-quality sands in the Gulf of Mexico. This objective was fully met, with highly saturated hydrate-bearing sands discovered in at least in two of three sites drilled.
Gas hydrate is a unique substance comprised of natural gas (almost exclusively methane) in combination with water. Gas hydrate is thought to exist in great abundance in nature and has the potential to be a significant new energy source to meet future energy needs. However, prior to this expedition, there was little documentation that gas hydrate occurred in resource-quality accumulations in the marine environment.
The Gulf of Mexico Gas Hydrate Joint Industry Project (JIP) Leg II expedition follows a 2005 JIP Leg I drilling program that focused on possible drilling hazards related to gas hydrate in fine-grained sediments. Leg II was designed to expand the understanding of gas hydrate in the Gulf of Mexico by specifically targeting systems thought to include high-quality (thick, porous, and permeable) sands.
The field program was led by NETL's Dr. Ray Boswell and the USGS's Dr. Timothy Collett and was managed by Chevron's Rana Roy and Dr. Emrys Jones. The program was completed on-time, with no safety incidents, and below the planned $11.2 million dollar budget.
The results from this expedition support the potential of gas hydrate as an energy resource, reports Dr. Boswell. This potential forms the foundation of the Office of Fossil Energy's Methane Hydrate R&D Program, which is focused on expanding future energy options by developing the information and technology required for eventual production of natural gas from hydrate. During the expedition, gas hydrate was found at saturations ranging from 50 percent to more than 90 percent in high-quality sands. The deposits were also found in close accordance with the project's pre-drill predictions, providing increased confidence in our gas hydrate exploration and appraisal technologies.
Our drilling at Walker Ridge block 313 and Green Canyon block 955 has discovered the most promising marine gas hydrate accumulations in the world, comments Dr. Collett. In addition, we have found gas hydrate in a range of settings, including sand reservoirs, thick sequences of fracture-filling gas hydrates in shales, and potential partially saturated gas hydrates in younger systems. These sites provide a wealth of opportunities for further study and data collection that will enable significant advances in understanding the nature and development of gas hydrate systems.
From an industry prospective, the cooperation of government, industry, and academia was critical to the successful completion of this project, adds Dr. Jones. There is no doubt that we have advanced our understanding of marine hydrates. While there is still much work to do, our knowledge of gas hydrates is significantly increasing through efforts like this one.
JIP Leg II also featured a number of technical advances, including the use of an advanced suite of logging-while-drilling tools that provided unprecedented three-dimensional images of hydrate-bearing sediments. In addition, the wells drilled at Walker Ridge, approximately 3,500 feet below the seafloor, were more than 1,000 feet deeper than any previous gas hydrate research well.
The operational success of JIP Leg II is due in large part to colleagues at the U.S. Mineral Management Service, AOA Geophysics, and Schlumberger who provided the initial appraisals of these targets. JIP Leg II operations were also supported by the Borehole Research Group at Lamont-Doherty Earth Observatory of Columbia University.