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Every day, some 80 million barrels of oil must be transported from their origin in oilfields around the world, moved to refineries in many countries, and distributed on to consumer gasoline stations and other end uses. Tankers by the thousands ply the seas, shipping the majority of the world's internationally traded crude oil from producing to consuming nations. Pipelines and trains handle much of the rest, moving oil and gas overland and sometimes underground from oil fields to ports, often across international borders. Trucks typically take on the final steps of distribution, transporting products -- ranging from gasoline to jet fuel to heating oil -- from refinery to customer.
Much of the world's crude oil starts its journey in pipelines, which consist of two broad types: those that carry refined products, and those carrying crude oil. The latter category is subdivided into "gathering" lines, which are small in diameter (approximately 2-8 inches) and extend from oilfields to central points, and "trunk" lines which move oil in bulk over great distances and are larger -- generally 8-24 inches in diameter, with some exceptions, such as the 48-inch Trans-Alaskan Pipeline.
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| Tankers ship the majority of the world's crude oil from the mouths of pipelines to the ports across the globe.
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With roughly 200,000 miles of pipelines, the U.S.'s system is the largest in the world. Domestically, oil and gas pipeline safety -- particularly the risk of explosions and leaks -- is a major issue, though pipeline operators insist that their technology is the safest and cleanest method of transporting oil in large quantities. Instances of pipeline sabotage, an issue of worldwide concern recently, are an old story, dating back to the technology's origins in 1865 -- when the first wooden pipeline was completed over the violent protests of Teamsters who held a monopoly on transporting oil in barrels by carriage.
Another key to maintaining the flow is the global fleet of oil tankers, now numbering around 3,500. Though these vessels are of widely varying size and quality, the one consistent trend throughout the business' 100-year history has been toward larger and larger vessels. Today, more than 400 VLCC ("very large crude carrier") class tankers, carrying over one million gallons of oil each, handle about one-third of the world's tanker volume. As size has increased, the cost of shipping has fallen to roughly 5-10% of the price per barrel. Meanwhile, the potential for dramatic spills and accidents has risen. Oil companies have responded to this risk, and related negative publicity, by shifting their cargo to independent shippers, many of which operate under "flags of convenience" from countries such as the Bahamas, Panama, and Liberia, where inspection and other rules are relatively lax.
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| The 800-mile-long Trans Alaska Pipeline transports oil from Alaska's Prudhoe Bay region, south to Valdez. |
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Another approach is to build safer vessels. Soon after the massive 1989 spill from the Exxon Valdez in Alaska's Prince William Sound, the U.S. Congress passed legislation requiring double hulls for all tankers in U.S. waters by 2015. But a double hull is certainly no spill-proof guarantee, and by 2001 only one-third of tankers in U.S. waters had them. Globally, the average is higher, at roughly one-half. The November 2003 spill of the Prestige off the coast of Spain led Europe to pass stricter double-hull requirements, possibly shifting single-hulled tanker traffic into U.S. waters. Despite the acute, localized effects of major oil spills, they are a relatively small source of total pollution worldwide. Large spills emit only half the oil into the oceans that natural seeps do, and only one-tenth the quantity of people's casual disposal of engine oil in storm drains -- a target of public awareness campaigns around the U.S.
Although the bulk of world's crude oil moves by pipeline and tanker, both trucks and trains still play important roles. Both transportation technologies have evolved alongside the oil business, and they are still connected to oil, both as a fuel and as cargo. In some countries, the legacy of rail transport -- whether established by the private sector, national governments, or colonial powers -- remains an important means of oil transportation. Trucks began to replace wagons as a means of delivering oil in the 1910s, and took over in earnest in the 1920s. Driving a truck with a liquid load can be difficult and dangerous, and today's oil trucks may have interior baffles -- bulkheads with holes -- to help regulate surges caused by the oil's motion over hills and curves.
-- Edwin Adkins
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