Ice Roads for Thumper Trucks
When a new oil field is opened, each phase of its development—exploration, drilling, and production—may damage the landscape, and in each of these phases, technological improvements promise to reduce or eliminate that damage.
More particularly, exploration, as it is currently conducted, consists of building a map of subsurface data and then drilling. Acquiring that data can be disruptive. The crews needed often number more than 100, and they move across the landscape in container trains pulled by bulldozers. Depth soundings are initiated by “vibroseis” vehicles, multiton articulated trucks lugging around vibrating plates. The plates generate low-frequency signals detectable by “geophones,” microphones placed in a grid over several kilometers in rows as close together as a hundred meters. Sometimes known as “thumper trucks,” these vibroseis vehicles do not produce the portable earthquakes that have agitated the environmental lobby in the past, but they are still sizable rigs that must cover kilometers of ground within a huge network of geophones, each of which must be laid by hand.
The damage caused by moving such equipment about can be minimized, Twyman argues, by exploring the refuge during the winter, when the terrain is frozen, and using Rolligons, vehicles with wide, balloon-style tires that would exert no more pressure on the tundra than a caribou hoof. (One industry photo even shows a Rolligon rolling over a smiling roughneck.) Coincident with the advent of the Rolligon has been the increasing use of ice roads on the North Slope. Ice roads are laid by Rolligons over the frozen tundra in mid-December and can support larger rigs pulling the mobile homes that house the crew. Drilling pads, too, can be built of ice. The oil industry contends that frozen roads and pads make the effects of exploration nearly invisible—all traces simply melt away—and believes that it can extend the drilling season further into spring by insulating the ice platforms.
Proponents also argue that the increasing accuracy of seismic data—which now yields 3-D rather than 2-D maps and can frequently be analyzed in real time by remote supercomputers—means that fewer soundings are necessary. The trade-off, however, is that although 3-D imaging reduces unnecessary drilling on what prove to be dry wells, it also requires the embedding of more microphones to obtain information in the first place. That, in turn, means more ground covered, with possibly harmful results. In any case, since the 1980s, advances in exploration technology have cut the number of wells needed to find oil in a field. This is good both for the oil industry’s bottom line and for the environment.
As the CRS report so baldly puts it, though, “there is no substitute, yet, for drilling,” both for testing the hypotheses of computer modeling and for bringing oil to the surface. No substitute, but the number of wells needed to verify exploration and complete extraction can hypothetically be reduced yet further through a variety of drilling techniques, including directional, “designer,” and multilateral drilling.
In directional drilling, extended-reach drills and bits angle out from a single platform to reach widely separated reservoirs of oil, covering a horizontal distance that can be two to five times the wells’ vertical depth. In the North Sea, such wells have reached eight kilometers in length. Designer wells use bits that can make tight turns to avoid obstacles while drilling. Multilateral wells lead several horizontal branches off a single master well. With 3-D modeling, designer and multilateral wells can reach smaller and smaller pockets of oil. Drill bits have also improved. Made with diamonds, they have become harder, making drilling faster and allowing shorter times on site.
Drill holes, too, have gotten slimmer, which means fewer “cuttings”—the waste material that surfaces during drilling—and fewer personnel needed to handle the equipment and the waste. Some of the associated equipment can be transported by air, which lessens the need for new roads. A related advance is the development of coiled-tubing drilling, first used on the North Slope in 1991. Where traditional rigs might be 60 meters tall and use nine-meter-long sections of interlocking pipe, coiled-tube drilling employs flexible pipe that can be carried on a spool (sometimes brought in by air), which means holes drilled faster with less equipment and a smaller drilling platform.
Much is made of the “footprint” of an extraction operation—the area it takes up—and Twyman reports that, overall, that has been much reduced as well. Drilling, for instance, produces enormous volumes of by-products, including water, natural gas trapped with the oil, and the cuttings fed up to the surface by a boring bit. These materials were formerly dumped into reserve pits six meters deep and around 4,000 square meters in area. Cuttings and water can now be pumped back into the ground. Furthermore, the water can now be separated from the oil while still underground, which alleviates the need for surface separation facilities. The general effect, industry contends, is smaller facilities manned by fewer men.