North Slope Methane Hydrate Coring Starts Soon
Abstract: It's still a scientific endeavor, but if Anadarko's joint venture to test Arctic methane production works, the time lag until there is access to that huge gas supply source could lessen considerably.
Analysis: They're just about ready to spud that methane hydrates well in Alaska.
A coring rig mounted atop a novel work platform reportedly is onsite at its first North Slope location, and engineers and scientists involved are gathering to oversee the drilling, as well as the core analysis, to be conducted inside a unique mobile, high-tech core lab facility--the first in the world for Arctic operations--to be stationed at the well site.
Anadarko Petroleum Corp., Maurer Technology Inc., Noble Engineering, and the federal government kicked off the three-year project in September 2001 as a "strictly scientific" endeavor. However, this first U.S. attempt at delineating how "the ice that burns" might be produced economically from beneath Arctic permafrost may have taken on new significance. The curve of the nation's available conventional domestic natural gas supply continues to flatten, even with Canadian imports tacked on, while projected demand remains on a steep upswing. Major gas pipelines from the North Slope of both the U.S. and Canada are being considered, as are new facilities to ship liquefied natural gas (LNG) to the Lower 48 States from Alaska and Canada, as well as from overseas. Coalbed methane development continues to grow, as well. Combined, these sources would affect the gas supply picture dramatically. But maybe not dramatically enough to keep pace with demand.
So, hydrates--long considered only a "maybe" in terms of future gas supply--also could be included in the mix of these new gas sources, and perhaps sooner than scientists and explorers imagined even a couple of years ago.
Methane hydrates are cage-like lattices of ice, inside of which are trapped molecules of methane and other hydrocarbon gases. Generally, hydrates form in two types of geologic settings: on the deep ocean floor and in shallow strata of areas overlain by permafrost (a deep section of frozen grass, soil, and rocks).
Much pure research is being done on offshore hydrates (see "Romancing the Ice," Oil & Gas Advisory, September 15, 2002), but little is known about how they might be brought to shore for controlled extraction of the gas. When a methane hydrate's ice lattice begins to melt, the gas molecules entrapped in it disassociate. Even slight rises in water temperatures are said to trigger such dissociation from huge mantles of seafloor hydrates, emitting methane into the atmosphere, where it rises above earth to become a much more serious "greenhouse" gas than even carbon dioxide.
The onshore hydrates, however, are more stable, temperature-wise, and the fact that they can be reached in dry environs and at relatively shallow depths makes them the most obvious choice for determining whether gas can be captured from them cost-effectively.
To establish why Arctic hydrates are an important research target, note that the Department of Energy (DOE) estimates total recoverable reserves of methane in Alaska's hydrate zones at some 11,000 to 24,000 trillion cubic feet (tcf). By comparison, current worldwide conventional natural gas resources are estimated at something like 7,000 tcf. But hydrates can mean trouble. Much as conventional natural gas was considered an annoying byproduct in the early days of crude oil exploration and production, oil companies today deem hydrates--particularly as encountered in shallow Arctic sediments--troublesome, at best. Once disturbed by the heat generated by bits and drilling fluids in North Slope oil wells, for example, hydrates often cause perilous safety problems, including "kicks" and other uncontrolled gas releases. Controlling the effects of such artificially applied heat will be a major challenge to future methane hydrate producers, and probably will be the impetus to cre! ate all-new technologies.
But back to the upcoming coring activity, expected to get underway any day now. The estimated $ll million project, whose cost is being shared 50-50 by the companies and the DOE, is using previous and ongoing research and development in onshore hydrate deposition to identify, quantify, and predict production potential for hydrates in the North Slope area. To do so, the partners designed a program to drill, core, and even produce the entrained gas safely and possibly even economically.
While nobody involved expects a definitive answer from this--the precursor of perhaps several more core holes in the area--the project's findings could spawn a much wider investigation of hydrate beds along Alaska's northern coastline. Alaska's leading North Slope producer, BP, is engaged in a four-year, $13.27 million effort to map methane hydrate concentrations at its Prudhoe Bay, Kuparuk River, and Milne Point oilfields. The mapping project does not include a coring element. However, those fields hold sufficient numbers of wells that BP could perhaps use some of them to produce methane from hydrates.
Canada, too, has extensive hydrate accumulations in its permafrost belt, and one joint government/private company effort several years ago extracted "pure science" hydrate cores in the Mackenzie River Delta area of the Northwest Territories.
But the Anadarko coring will have the "luxury" of the onsite analysis lab, where the core can be scrutinized as soon as it is removed from the hole. The cores from the Canadian operation had to be shipped to various labs in insulated containers, which affected their "freshness." Regardless of ambient temperatures, when hydrate cores are pulled from the hole, they degrade rapidly.
According to Tom Williams of Maurer Engineering, who manages the project, the first coring site is on an Anadarko lease located a few miles southwest of BP's Kuparuk River oilfield. The lease area overlies a wide concentration of subsurface hydrates identified by seismic records, electric logs, and other geological data from nearby oil well drilling activity.
The 3,500-foot (1,067-meter) core test, dubbed "Hot Ice No. 1," will employ the latest Arctic technology, including a winterized coring rig installed atop a novel modular aluminum platform equipped with steel legs that raise the work level to 12 feet above ground. Called the Arctic Exploration Platform, the facility was designed by Anadarko engineers to have minimal effect on either frozen or partially thawed tundra, since no gravel drilling pad will be used. This could widen the project's operations weather window to as long as eight months compared to the three to four months allowed for conventional North Slope drilling operations. In any case, the project will be halted from time to time to allow for important local wildlife cycles, including caribou calving and migratory wildfowl nesting, among others.
According to Maurer's Williams, subsurface data indicate the core hole will encounter a hydrate zone at about 1,400 feet, which is located just beneath the deepest permafrost level. A second zone lies at about 2,500 feet. Combined, the hydrate zones should range in thickness from about 500 feet to as much as 1,000 feet.
Drilling will involve using chilled drilling fluid, which will keep the cores from warming before they are transferred immediately to the nearby mobile analysis lab, which Anadarko also will use for its conventional oil and gas coring operations on the North Slope.
The actual recovery of the 3.45-inch (9-centimeter) diameter core from the hydrate zones of the Hot Ice No. 1 will take only about 30 days. However, the rig will remain somewhat longer to complete the well, since the project includes production testing using a heated coil suspended in the production tubing. That way, small quantities of methane can be released from the hydrates. Williams says the expansion factor with Arctic hydrates is considerable. In that area, 1 cubic foot of Arctic hydrate will produce 164 cubic feet of gas.
The results of both the core analysis and the production testing will affect the group's decision to drill additional core holes in the area, DOE officials said.
Meanwhile, the eyes of the petroleum industry will be focused on the project, since it may help determine just how long it might take for the methane contained in Arctic hydrates actually to be developed. And if results are positive, the time lag may be cut considerably.