Speaking at a meeting about North Slope gas hydrates research, U.S. Geological Survey (USGS) geologist Tim Collett

said, “When we look at it, Alaska has always been our best gas hydrates experimental place, and it's the place where we've been able to collect the most data with the most well penetrations in the best hydrate occurrences.”

In November, the Alaska Department of Natural Resources (DNR), which recently signed a memorandum with the Department of Energy (DOE) to work together to facilitate gas hydrate and other energy research in Alaska, withheld a number of open leases in the Greater Prudhoe Bay region from upcoming lease sales to provide an opportunity to determine the suitability of those lands for gas hydrates research. The December 2013 meeting in Denver, hosted by the USGS, was held to enable geophysicists at the DNR to report on their review of the potential of that acreage, according to DNR geophysicist and speaker Diane Shellenbaum.

Ray Boswell, of the DOE's National Energy Technology Laboratory, said, “From our prior testing in Alaska we have confirmed that these gas hydrates field programs can be conducted safely and effectively, even in areas of ongoing industry activity. We have confirmed that it's necessary to look at gas hydrates as a petroleum-systems approach and applying what we already know from unconventional oil and gas.

“Gas hydrates in Alaska occur at high saturation in sand-rich sediments and are the most amenable to current conceptions for gas hydrate production. If we can't figure out how hydrates work in Alaska and demonstrate their producibility there, then it's going to be difficult to do it anywhere,” he said.

During the past 10 years, the Arctic has hosted a series of comprehensive field-evaluation programs. Japanese and Canadian researchers began tests at the Malik site in northwest Canada, where it was conclusively demonstrated that gas hydrates are technically recoverable with the depressurization method.

The formal USGS assessment, according to Collett, indicates that there are 85 trillion cubic feet (Tcf) of technically recoverable resources in hydrate form on Alaska's North Slope.

Collett described regional controls on gas hydrate occurrences on the North Slope, based on the concepts of a working petroleum system including source migration, structure, and gas hydrate occurrence in the geologic system. He also described the nature of two confirmed gas hydrate North Slope occurrences, known as the “Eileen” and “Tarn.” Seismic data was analyzed and downhole logging data was collected from the Mount Elbert prospect (BP) and the Ignik Sikumi project (ConocoPhillips and Jogmec).

According to Collett, these are unconventional deposits formed when pre-existing “free gas” accumulations were later converted to gas hydrates. The pressure and temperature conditions for the hydrates in the permafrost were only created about 1.6 million to 1.8 million years ago, but all of these systems have been active for a much longer period of time. “This is important because it's different than a marine environment where the hydrate system evolves over a very long period of time,” he said.

—Larry Prado

Comments