Since the Prudhoe Bay field on the North Slope of Alaska was developed in the mid-1970s, technological innovations have dramatically changed the scope of operations. According to the U.S. Department of Energy, if Prudhoe Bay was developed with today’s technology, its footprint would be 64% smaller, the drilling impact area would be 74% smaller, roads would cover 58% less surface area, and operating facilities would take 50% less space.
A number of technological innovations have made smaller, less intrusive development possible in Arctic environments. Several of these are explained below.
Ice Roads and Ice Drilling Pads
When oil and gas exploration began in the Arctic in the 1920s, roads were bulldozed directly onto the tundra – which thawed the underlying permafrost, rendering the route impassable after one season. Road construction techniques rapidly evolved as more was learned about the environment. Crews now construct temporary ice roads. Temporary ice roads allow the construction of oil field pipelines during the winter months, thus largely eliminating the need for permanent gravel roads adjacent to pipelines. Ice-road building techniques are also used to create ice runways and ice pads to support exploratory drilling. Ice roads and pads melt in the spring and leave no significant damage to the tundra.
Ice roads are suitable for all conventional wheeled vehicles, from pickups to dump trucks. Ice road construction involves first compacting snow already on the tundra; the tundra is not scraped or removed. Tanker trucks apply either seawater from the ocean or freshwater from nearby lakes, chosen for minimum impact to fish, to create a firm crust. Chipped or crushed ice is then laid down to build thickness and create a smooth surface. The crushed ice is watered and allowed to freeze. When the ice road has reached a thickness of 12 to 18 inches, a road grader scars the surface; at very low temperatures this rough surface creates excellent traction for tires. All spills or releases on ice roads and pads are removed during operations and before the ice melts. Snow roads are also occasionally constructed using snow rather than ice to thicken the roadbed.
Ice pads have been used for years to support the drilling of exploration wells across Alaska's North Slope. Construction of ice pads uses the same techniques as ice roads. When an exploration well is completed, the drill rig and other facilities are removed; after the pad melts in the summer, it is difficult to see where the site was located. Recently, new, prefabricated insulating panels are being used to extend the exploratory drilling season by as much as 50 percent. This means drilling can be completed in fewer seasons, reducing seasonal equipment mobilizations and minimizing environmental disruptions.
Directional/Horizontal Drilling
It used to be that wellbores were basically vertical (or only slightly deviated) holes. This made it necessary to drill virtually on top of the location of a potential oil deposit. While the ability to drill an angled, directional hole has existed for a long time, the difficulty was in controlling the angle to assure that the target was reached. Using older processes, periodically, the drill pipe and bit had to be removed from the hole and a tool inserted to take readings from which the angle could be adjusted when the bit and pipe were returned to the hole to resume drilling. But the advent of minaturized computers and advanced sensors that can be attached to the drill bit now allows companies to drill directional holes with great accuracy since they can get real-time information on the subsurface location throughout the drilling process. Today, with directional drilling, a well can reach a target the size of a walk-in closet located over 5 miles away from the drilling rig and more than a mile deep.
The ability to use directional drilling allows many wells to be drilled from a single well pad, and for wells to be spaced much closer together. This greatly reduces the amount of surface area, or footprint, required to drill the same number of wells.
Horizontal drilling is similar to directional drilling, but the well is designed to cut horizontally through the middle of the oil or gas deposit. This has the potential to substantially increase the recovery of oil or gas from that formation. While not applicable everywhere, horizontal drilling has been used successfully on the North Slope. Early horizontal wells penetrated only 500 to 800 feet of reservoir laterally, but technology advances recently allowed a North Slope operator to penetrate 8,000 feet of reservoir horizontally.
Coiled Tubing Drilling
Another drilling innovation is the use of coiled tubing to replace traditional drill pipe. Coiled tubing eliminates the time and cost associated with the continuous joining, reinstallation, and removal of drilling pipes. A coiled tubing drilling rig is significantly smaller than a traditional rig, requiring only about half as much working space. These rigs are quieter than conventional drilling operations and, because they drill smaller diameter holes, produce less waste. Operators on the North Slope are employing coiled tubing technology where feasible to further reduce their footprint and impact.
This technology continues to advance and its use will continue to grow. New materials like advanced titanium alloys and advanced metal-free composites are continuing to improve the reliability, performance, corrosion-resistance, weight, and cost-effectiveness of coiled tubing operations.
3-D Seismic Technology
Substantial enhancements in computing power during the past two decades have allowed the industry to gain a much clearer "picture" of what lies beneath the surface. The ability to process huge amounts of data to produce three-dimensional seismic images has significantly improved the drilling success rate of the industry. By reducing the number of wells that need to be drilled to achieve the same level of production, surface disturbance is diminished and waste volumes are decreased.
Since it is not feasible to build ice roads for conducting initial seismic surveys, the industry has developed large all-terrain vehicles with huge, low-pressure, balloon-like tires that can carry substantial loads across the tundra leaving virtually no tracks. To further protect the tundra, such operations are conducted only in the winter when the ground is frozen solid and wildlife is absent.
Grind-and-Inject Technology
The construction of permanent facilities (roads, living quarters, etc.) in an Arctic environment usually requires the use of gravel. The primary waste product from drilling is the rock cuttings that are brought to the surface. In 1988, one of the North Slope companies proved that processed drill cuttings could be ground and used in road construction since the material was essentially identical to native gravel and surface soils. The portions of cuttings that cannot be used as gravel are ground even more finely and injected back into a subsurface formation. This allows drilling operations in Arctic environments to operate without drill pits and to achieve "zero discharge" of drilling wastes. This technology results in decreased waste volumes, less mining of surface gravel, and less surface disturbance.
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