Geologists knew more than a century ago there was oil on Alaska's North Slope. A 1921 report to the US Geological Survey that discussed Alaska petroleum noted areas of the state had oil seeps that looked commercially promising, including 'some indications of oil in the extreme northern part of Alaska, a region at present almost inaccessible.'
At that time, geologists relied on obvious signs of oil, such as seeps, to find potential oil fields. In the '20s, a method of using sound waves to define underground rock layers was developed. Called 2D seismic surveys, they allowed geologists to see thin slices of the layers of rock underground. In the '80s, 3D surveys widened and sharpened that view. Today, 4D surveys are common. Each advance resulted in more data points for a more accurate look at what was happening underground.
"It's like you're looking through your binoculars, but you don't have them focused," says Chris Nettels, president of GeoTek Alaska, who has worked in the oil industry for more than forty years. 'You're looking and you can see these blob shapes in general, but you can't see what they are. And then all of a sudden, you start focusing and oh, that's a bear!"
Over the years, geologists have been honing their focus. In the oil and gas industry, data is king. Nettels says a coworker once told him, "You've got to learn to drink from the firehose, Chris. That data will always be available. Drink from the firehose and take as much data as you can."
Technology has been and remains a huge driver in gathering and processing data. During his career, Nettels has moved from floppy disks to thumb drives, from a room full of supercomputers to powerful laptops.
"You start to see things better through better data acquisition processing," Nettels says. "Then you can do a better job interpreting because you've got better data sets. So it really comes down to visualization.
"No one today will drill wells without having seismic data, you'd just be a nut to do it," he adds. "So that means today no one's going to do a wildcat exploratory well without having had shot seismic data first [to] know where to put that location for your best opportunity at finding oil."
What Are They Looking For?
Imagine the North Slope is a layer cake, with oil-bearing layers sandwiched between layers of impervious rock, he says. Each layer has a different density, which affects the speed of a seismic wave. But the Slope is also riddled with lots of minor faults, like...