Hot Ice finds gas, but no gas hydrates, at test well
Department of Energy says Anadarko’s Arctic drilling platform south of Kuparuk performed well, as did mobile core lab, continuous coring rig
The Hot Ice No. 1 well drilled over the last year south of Kuparuk on Alaska’s North Slope didn’t find the gas hydrates it targeted, but the U.S. Department of Energy said March 1 that although the well “did not encounter methane hydrate as expected,” it “did produce information that should help to overcome the substantial technical obstacles to the eventual commercial production of this abundant energy resource.”
Hot Ice No. 1 was drilled as part of a two-year cost-shared partnership between DOE’s Office of Fossil Energy, Anadarko Petroleum Corp., Mauer Technology Inc. and Noble Engineering and Development.
Not very much is known about the subsurface distribution of methane hydrate, which is a compound of water and methane that forms under pressure at cold temperatures and has been found under Arctic permafrost and in deep-sea sediments, DOE said, but the worldwide volume of methane hydrate “is estimated to be far greater than all the world’s conventional natural gas resources.”
Subsurface distribution not well understood“We’re just beginning to understand the nature of methane hydrate distribution in the subsurface,” said Brad Tower of DOE’s National Energy Technology Laboratory, which oversees the methane hydrate research program. “Each time we are able to successfully gather high-quality scientific data from the subsurface — as we did with the Hot Ice No. 1 well — we add significantly to our understanding of how hydrate forms, how it can be located, and what its resource potential might eventually be.”
Hot Ice No. 1, just south of the Kuparuk River field and some 60 miles west of Deadhorse, was the first dedicated hydrate well in Alaska. Spud March 31, 2003, drilling operations were suspended when the weather warmed and were resumed in January. The well reached its planned total depth of 2,300 feet Feb. 7, about 300 feet below the zone “where temperature and pressure conditions would theoretically permit gas hydrates to exist,” DOE said.
The department said that while there were “significant gas shows” in the well, no gas hydrates were found.
“The absence of hydrate at the site is in itself a significant scientific finding,” said Tom Williams, vice president with Maurer Technology and a member of the team drilling the well. Williams said that based on data from wells in the area, Hot Ice No. 1 “was expected to encounter a significant thickness of reservoir quality sands in the Upper West Sak unit.”
While the sands were there, Williams said, “we found free gas and water rather than hydrate in the hydrate stability zone. Figuring out why will require a thorough post-mortem analysis of the core, log, and seismic data from the well.”
“Clearly,” he said, “the model for distribution of methane hydrate on the North Slope may be more complex than we previously thought.”
Innovative technologies demonstratedDOE said the well was an opportunity to try out “several unique and previously untested Arctic drilling technologies” expected to be used in future Alaska drilling, including Anadarko Petroleum’s Arctic drilling platform, a mobile hydrate core analysis laboratory and a new application of a continuous coring rig.
The Anadarko Arctic platform, 16 lightweight aluminum modules fitted together and mounted on steel legs to create a platform large enough to contain a rig, auxiliary equipment and a mobile laboratory, includes five modules in an adjacent platform with living quarters for 40 people. DOE said the design of the platform allows “light and air to reach the tundra grass at a drill site during the summer months, and the relatively small and shallow holes created by the legs can be filled when drilling is completed.
“The system eliminates the need to build drilling pads of ice or gravel that have more impact on the tundra landscape,” DOE said.
The department said that there appears to have been “no adverse impact on the environment or wildlife” from leaving the platform in place during the summer, “lending support to the idea that such a system could be used to safely extend the drilling season on the North Slope by several months.”
Mobile core lab from University of OklahomaA mobile core lab used at the project was developed at the University of Oklahoma.
DOE said the lab “makes it possible to analyze cores at a reduced temperature and in close proximity to the drill site.”
Because methane hydrate “quickly separates into methane gas and water when warmed,” it is significant that cores were successfully analyzed “at a reduced temperature and in close proximity to the drill site.” The lab took measurements both on core and on one-inch plugs from the full-sized core. DOE said Hot Ice “also provided an Arctic test of a state-of-the-art CAT scan tool developed by Lawrence Berkeley Laboratory specifically for pinpointing methane hydrate concentrations within cores immediately upon retrieval.”
A continuous coring rig used to drill the Hot Ice well was successful in “drilling and coring relatively shallow wells through permafrost intervals.” Hot Ice was the “first attempt at continuously coring permafrost to detect methane hydrate,” DOE said, and 93 percent of the core from depths of 82 feet to 2,300 feet was successfully recovered.
A high-resolution, three-dimensional vertical seismic profile survey was shot at the well, and DOE said that survey “should help to delineate the stratigraphy and structure that control the occurrence of hydrate in the area.”
“Although we did not find the hydrate we expected, we were able to advance a whole suite of technologies that could ultimately make exploration for and production of the Arctic methane hydrate resource economically feasible,” added Tomer. “These new technologies can be taken to future hydrate research sites where they will ultimately aid in building a better characterization of this potentially important frontier resource.” In addition, DOE said, geologic knowledge gained from an ongoing comprehensive analysis of the core, log, and seismic data from the well will improve models for the genesis and distribution of hydrate accumulations on the North Slope.