Читать книгу Power Trip: From Oil Wells to Solar Cells – Our Ride to the Renewable Future - Amanda Little - Страница 10

You have to burn fossil fuels to harvest them—that’s a reality in any drilling scenario—but the ratio of energy invested to energy gained gets slimmer as the drilling conditions get more extreme. (By “energy invested” I’m referring to all fossil fuels used to discover, drill, pump, and refine the oil and transport it to market.) During the glory days of U.S. oil production in the 1930s, an investment of 1 barrel of oil would yield a return of about 100 barrels. By 1970, when oil deposits had become scarcer and more difficult to extract and refine, the ratio had shrunk by more than half: 40 barrels of oil gained for every 1 barrel invested. By 2005, as the industry faced ever-greater limits, the ratio had diminished still further: about 14 to 1. Returns will continue to diminish, some experts argue, until we reach a 1:1 ratio; and that would spell the end of the petroleum era.

As I watched the Cajun in action, I began to understand why extreme drilling conditions can be so treacherous and demanding. It’s an expensive fuel-intensive process by itself to grind a drill into the farthest reaches of the earth; it’s an even bigger challenge to overcome the inevitable barriers and delays that occur along the way, draining more fuel and resources as the project wears on. That morning, workers on the Cajun Express had begun scraping clean the 5-mile drill hole so that perforating guns could be dropped down to the base of the well. There the guns would be triggered, releasing a spray of buckshot to loosen the sediment and stimulate the flow of oil into the well. If these highly sensitive instruments encounter unexpected obstacles on the way down, they can fire prematurely and this can permanently cripple the well. The well therefore has to be thoroughly cleared first by a tool known as a junk basket—an 8-inch-wide hunk of iron that’s forced up and down the entire 5-mile length of the hole, removing loose earth, rocks, and other possible barriers.

Halfway through our visit, Siegele took me to the rig’s control room—a small glassed-in chamber that contains a thronelike chair and a desk with a red joystick that operates the drill. I could hear the clank BOOM clank BOOM of the drill’s robotic arm sounding rhythmically as it gripped, positioned, and screwed together 90-foot sections of pipe to plunge the junk basket ever deeper into the hole. Minutes later, Siegele got some bad news. “The junk basket is stuck way down there on some debris,” reported Ron Byrd, a weather-beaten Chevron employee who has captained Gulf rigs for more than thirty years. Siegele winced almost imperceptibly. “Just a little bump in the road,” he muttered when I pressed him for details. Technically, it was a million-dollar bump. The crew would have to spend the next forty-eight hours fishing the jammed cleaning tool out of the hole, halting all other activity on a rig that costs over $500,000 a day to lease, fuel, and operate. But this is chump change to Siegele, with his annual budget of more than $1 billion. “If snags like this didn’t happen so frequently, you’d probably let them get to you,” Siegele told me, sucking in a breath of salt air. “But you can’t do these kinds of wells without stuff breaking—it comes with the territory.”

It’s one of many hazards that come with the territory. Take, for instance, loop currents. These mighty flows of water propelled by the Gulf Stream can threaten to bend or snap the drill shaft as it plunges toward the seafloor, and have to be vigilantly monitored for any directional shifts. The rig’s electrical system is also highly vulnerable—if a fuse blew, the thrusters would seize up, and the drill shaft would have to be severed. Still another challenge is guiding the drill on its optimal course down through 30,000 feet of sediment—a challenge akin to “flying above New York City in a jumbo jet, aiming a baseball at the pitcher’s mound in Yankee Stadium, and hitting it dead center,” said Siegele. The margin of error as the drill enters the seafloor is only about a meter in any direction. Any farther, and chances go up that you’ll hit a fault line or air pocket that will throw the whole well off.

Charting the course of the drill is an implausibly difficult task of its own. “We’re pretty much shooting in the dark,” said Siegele. Chevron runs its offshore drilling operations out of a gleaming Houston skyscraper that’s the shape of twin cylinders, resembling the nose of a double-barreled shotgun aimed skyward. The company devotes billions of dollars annually to mapping out the subsea landscape of its deepwater fields on high-tech equipment at this location, but there’s a limit to what these maps can show.

Geologists work in cavernous visualization rooms with floor-to-ceiling monitors and computers that have the processing power of “a PlayStation the size of an eighteen-wheeler,” as one engineer described it to me. The computers crunch seismic data that are then translated into maps of ancient sediment. To collect the data, geologists deploy ships that cruise above deep-sea prospects and pop off air guns—underwater cannons that emit gigantic burps of air into the ocean, bouncing sound waves off the underwater rock formations. Aquatic microphones tethered to the vessel record the response.

Gathering seismic data for subsea oilfields in the Gulf of Mexico is far trickier than in other offshore drilling regions. The sediment beneath the Gulf has a salt layer that’s as massive and ragged as the Swiss Alps; this layer acts like a fun house mirror for sound waves, deflecting and distorting them in ways that other sediments don’t. So Siegele’s team had to trigger multiple air guns at once while microphones took hundreds of thousands of recordings simultaneously. The vast constellation of data points enabled Chevron’s seismologists to unscramble the salt layer’s distortions. Still, the maps were largely inscrutable. “Reading these maps is like looking through a wall of thick glass brick,” as one geologist told me, “and trying to count the eyelashes of a person on the other side.”

The maps also can’t predict how hard it will be to extract the crude. You might think of oil as situated in big pools under layers of rock. But it’s actually embedded in the rock, like water in a sponge. “When you drive the drill down you’re going into porous rock that can be either kind of squishy or kind of rigid,” Siegele explained. Squishy is better, but as rocks age in deeper terrain, they typically become tighter—meaning less productive. You also confront more debris that can clog the well shaft: in other words, instead of sucking up the oil in one big swig like a soft milkshake, it’s as though chunks of ice and strawberry get stuck in the straw. That’s why, when I visited the Cajun, teams of geologists were standing by to analyze the rocks and mud that got pulled up by the junk basket, hoping to gather a better understanding of the conditions deep below.

Temperature and pressure also pose risks to drilling activities, so engineers must vigilantly scan the computer readouts that monitor these conditions as machinery travels down through the sediment, crossing geological layers that range from hard bedrock to sand to empty voids. The rapid pressure changes between these layers routinely disturb equipment. At the well bottom, there is enough pressure to implode a human head—or more pertinently, to crack iron casings. And the closer you get to the earth’s core, the hotter the rocks become. At 20,000 feet below seabed, the oil is hot enough to boil an egg. At 30,000 feet, the oil can reach over 400 degrees Fahrenheit, hot enough to cook off into natural gas or carbon dioxide. Meanwhile, the water at the bottom of the deep sea is at near freezing temperatures, creating a dangerous contrast as the oil is pulled up.

Any one of these factors—loop currents, faulty drill placement, electrical glitches, rock porosity, pressure and temperature changes—could delay operations for days, weeks, even months. At more than half a million dollars a day, the operating costs add up on deep-sea rigs like the Cajun. Hurricanes, too, pose an ominous threat. In 2005, the year of Katrina, Chevron had to carry out seven emergency evacuations. BP’s legendary Gulf of Mexico platform Thunder Horse suffered a $250 million blow when a hurricane tore a tiny hole in its hull that eventually sank half the rig, requiring a stem-to-stern reconstruction.