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DOE optimistic about methane hydrate New report highlights progress towards possible future development of a resource that could produce vast quantities of natural gas Alan Bailey Petroleum News
In the nearly 10 years since Congress first authorized the U.S. Department of Energy to implement and coordinate research into the possible production of natural gas from methane hydrate, vast quantities of which exist offshore the United States and around the base of the permafrost under Alaska’s North Slope, the DOE gas hydrate program has made significant progress in its mission, according a draft status report mandated by Congress and published by the National Research Council Jan. 29.
“DOE’s program and programs in the national and international research community provide increasing confidence from a technical standpoint that some commercial production of methane from methane hydrate could be achieved in the United States before 2025,” said Charles Paull, chair of the committee that wrote the report, and senior scientist, Monterey Bay Aquarium Research Institute. “With global energy demand projected to increase, unconventional resources such as methane hydrate become important to consider as part of the future U.S. energy portfolio and could help provide more energy security for the United States.”
Concentrated natural gas Methane hydrate consists of a white crystal-like substance that concentrates natural gas by trapping methane molecules inside a lattice of water molecules (methane is the primary component of natural gas). The hydrates remain stable within a certain range of temperature and pressure, but when decomposed yield about 164 times their volume in methane.
The huge volumes of methane locked up in methane hydrate deposits under the North Slope could become a major source of natural gas for export through a future North Slope gas pipeline, and the close proximity of an existing oilfield infrastructure to these deposits has made the deposits a prime focus of methane hydrate research. The U.S. Geological Survey has estimated that there are between 25.2 trillion and 157.8 trillion cubic feet of technically recoverable natural gas in these deposits.
There are also major methane hydrate deposits under the Gulf of Mexico, perhaps less easy to access than on the North Slope but also close to existing infrastructure.
Three North Slope projects There are currently three DOE-supported methane hydrate projects in progress on the North Slope: a BP-managed project that drilled the Mount Elbert methane hydrate test well in the Milne Point area in 2007; a ConocoPhillips-managed project to investigate the possibility of using waste carbon dioxide to tease methane from hydrates; and an investigation of the methane hydrate resource potential of gas fields near the town of Barrow.
The drilling of the Mount Elbert well in the BP-managed project followed a multiyear investigation of seismic and well-logging techniques for locating, characterizing and quantifying gas hydrate deposits under the central North Slope, and a parallel program of field and laboratory studies to evaluate the practicalities of producing natural gas from the hydrates. A total of 16 research groups have been involved in this project, the NRC report says.
The researchers successfully recovered methane hydrate samples from two sandstone intervals in the Mount Elbert well, thus enabling the refinement of the well-log and seismic attributes of the hydrates and ultimately enabling USGS to reassess the methane hydrate resource potential of the entire North Slope. And downhole testing of the hydrate-bearing rock formations provided new insights into the response of the hydrates to pressure changes, an important factor in the potential production of natural gas from the hydrates.
The research team wants to follow up on the results from the Mount Elbert well by conducting a methane hydrate production test somewhere in the central North Slope and has been investigating possible test sites. The team may reconfigure its membership to help resolve any land ownership and land access issues, the NRC report says. And BP anticipates deciding by the end of March on whether to move to the production test phase of the project, the report says.
Using carbon dioxide The ConocoPhillips project, initiated in 2008 and having the attraction of offering a means of sequestering carbon dioxide in addition to producing natural gas, is based on a concept demonstrated in small-scale laboratory experiments, involving the replacement of methane molecules in the methane hydrate lattice structure by molecules of carbon dioxide. No tests of this type have been conducted on naturally occurring methane hydrate samples, the report says.
To address the significant challenge of replicating the laboratory experiments in a scaled-up field trial, ConocoPhillips has selected a field site and plans to initiate a test project in early 2010, the report says (ConocoPhillips said in October that it anticipates conducting the field test in the winter of 2011).
The Barrow gas fields project also started in 2008, this time under the terms of an agreement between DOE and the North Slope Borough, and involving Anchorage-based Petrotechnical Resources of Alaska. The production characteristics of the gas fields had led people to suspect that the disassociation of methane hydrates in the gas reservoirs had been contributing to gas production from the fields, and work to date in the DOE-sponsored project has focused on the assessment of where in the subsurface the hydrates may be stable and, hence, what volume of hydrates may be present.
The project team now plans to drill a well, to verify whether the methane hydrate is present and to test a production technique in which the hydrates would be disassociated by the removal of adjacent free gas in the reservoir.
Gulf of Mexico A DOE-sponsored and Chevron-led project in the Gulf of Mexico began in 2001 and has focused primarily on characterizing gas hydrate deposits in reservoir-quality sands under the gulf. The project has involved 18 industry partners, several federal agencies, national laboratories and university research groups, the NRC report says.
Initial phases of the project culminated in 2005 with the first successful drilling and coring of methane hydrate in the Gulf of Mexico, with well logs, cores and borehole seismic data being acquired from two sites. Equipment developed for the project enabled the testing of cores from the wells at in-situ pressures.
Results from the 2005 drilling led to the planning of a further drilling program and the drilling of seven wells in the spring of 2009, penetrating gas hydrate deposits and confirming the effectiveness of techniques such as 3-D seismic for detecting the deposits. The delineation in some wells of thick sand bodies with methane hydrates confirmed the existence of hydrate resources that may be used to produce natural gas, if appropriate production techniques are developed, the NRC report says.
But many significant challenges remain, to prove out both the sustained production of significant volumes of natural gas from methane hydrates and to show that this production can be done at an economically viable cost. It will be necessary to demonstrate well completions designed for gas hydrate production and to conduct long-term production tests to evaluate the possibility of commercial methane hydrate development, the NRC report says.
The report also recommends several other lines of research, including further research into the use of carbon dioxide for natural gas production from hydrates; further research into the hazards associated with the presence of methane hydrates when drilling conventional oil and gas wells; and the continued development of geophysical techniques for mapping and measuring gas hydrate deposits.
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