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Hydrate well production test gets regulatory OK Alaska regulators grant ConocoPhillips request to inject carbon dioxide in effort to produce methane via ‘gas-to-gas exchange’ Wesley Loy For Petroleum News
Alaska drilling regulators have issued an order authorizing a procedure to test production from an experimental natural gas hydrate well in the Prudhoe Bay field.
The procedure involves injecting a mixed stream of carbon dioxide and nitrogen gases into the Ignik Sikumi No. 1 well. The well, already drilled, is a partnership between ConocoPhillips, the U.S. Department of Energy’s National Energy Technology Laboratory (NETL), and a Japanese company.
The idea of the injection is to “evaluate in-situ gas-to-gas exchange as a potential method for producing methane from gas hydrates,” says the Jan. 18 enhanced recovery injection order from the Alaska Oil and Gas Conservation Commission.
Huge potential of hydrates The well’s name, Ignik Sikumi, is Iñupiaq for “fire in the ice.”
Hydrates are a solid, crystalline form of gas, usually methane, mixed in sandstone and water. A combination of cold and pressure keeps the gas as a solid.
The test will involve injecting tons of carbon dioxide down the well in an effort to free methane from hydrate-saturated sandstone.
The process involves exchanging CO2 molecules for methane molecules within the hydrate. The aim is to produce methane gas, leaving the CO2 trapped underground.
This has worked in a lab, but hasn’t been tried in the field.
Ignik Sikumi is an important project considering the huge potential that hydrates represent. The U.S. Geological Survey has estimated 85 trillion cubic feet of undiscovered, technically recoverable gas resources exist within hydrates in northern Alaska. That compares to the 35 tcf of known conventional gas in Prudhoe Bay and other North Slope fields.
Injection details ConocoPhillips spudded the Ignik Sikumi exploratory well on April 5, 2011, and reached a total depth of 2,597 feet on April 16, an AOGCC well completion report shows.
It was drilled on an ice pad adjacent to the BP-operated Prudhoe Bay unit L-pad and temporarily suspended.
The well will be re-entered for the production test. The plan is to inject up to 20 tons of mixed CO2 and N2 into the hydrate-saturated Upper C Sand of the Sagavanirktok formation.
“The injected ... mixture in a gas state will exchange with the methane and remain sequestered in the pre-existing hydrate lattice,” the AOGCC order says.
Injection will occur within the Upper C Sand as deep as 2,273 feet measured depth.
The order says injection will occur over 10 to 14 days, with drawdown and production to follow.
“Produced fluids will be flowed through above-ground well testing equipment where the produced gas will be heated, separated and measured,” the order says.
In issuing the order, commissioners sought assurances the injection won’t interact with six nearby wells or affect fresh water zones, and also that fluids won’t migrate outside of the Upper C Sand.
Japan connection An Oct. 24, 2011, NETL press release said the Japan Oil, Gas and Metals National Corp. also is involved in the Ignik Sikumi project.
Test plans call for “roughly 100 days of continuous operations from January to March 2012,” the release said.
“The collaborative testing will take place under the auspices of a Statement of Intent for Cooperation in Methane Hydrates signed in 2008 and extended in 2011 by DOE and Japan’s Ministry of Economy, Trade, and Industry,” NETL said. “The production tests are the next step in both U.S. and Japanese national efforts to evaluate the response of gas hydrate reservoirs to alternative gas hydrate production concepts. The tests will provide critical information to inform potential future extended-duration tests.”
Following the attempted swap of CO2 and methane molecules, the research team will conduct a monthlong evaluation of an alternative methane production method called depressurization.
“This process involves pumping fluids out of the borehole to reduce pressure in the well, which results in dissociation of methane hydrate into methane gas and liquid water,” NETL said. “The method was successfully demonstrated during a 1-week test conducted by Japan and Canada in northwestern Canada in 2008.”
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