This winter, a major oil exploration effort is happening in a familiar place: Prudhoe Bay

An oil rig at Prudhoe Bay in 2017. This winter, BP is undertaking a massive 3-D seismic exploration program at Prudhoe Bay. (Photo by Elizabeth Harball, Alaska’s Energy Desk)

Several big new oil discoveries have been announced in Alaska over the past few years, and a lot of attention is focused on the next wave of North Slope oil exploration, especially when it comes to what might happen in the Arctic National Wildlife Refuge.

But this winter, a massive exploration effort is aimed at finding new oil in a field that was discovered five decades ago: Prudhoe Bay.

Prudhoe Bay is the biggest oil field in North America and it has been in production for over 40 years now — a decade longer than expected. But today, if you could peek inside the machinery at Pump Station 1 that collects everything pumped up from Prudhoe Bay, less than one percent of what’s in there is oil. There’s a little bit of water. The other 97 percent? Natural gas.

“So while we’re still a very big oil field, we’re a huge gas field and a big water field,” said Scott Digert of BP Alaska. Digert is the area reservoir development manager for the east side of Prudhoe Bay.

At least for now, Alaska doesn’t have a second pipeline to get all that gas to market, so most of it is pumped back into Prudhoe Bay to help recover more oil. Digert said there’s still plenty left in Prudhoe Bay, but now, they have to work a lot harder to get it, using increasingly advanced technology.

This winter, BP is getting ready to use some of that technology. The oil company is launching a massive effort to get the clearest picture yet of what the Prudhoe Bay oil field looks like. The idea is that, after all these years, there’s more oil at Prudhoe to drill, but it’s in harder-to-find pockets.

“We have thousands of wells that have gone through this area,” Digert said. “But now we’re down to smaller and smaller oil pools that we’re trying to target.”

Digert explained that this winter, BP is going to go over 470 square miles with a fine-toothed comb.

“This is an unusually large survey for us,” Digert said.

To do it, BP is using what’s called 3-D seismic technology. BP geophysicist Gino Alexander said simply put, 3-D seismic is the process of using sound waves to figure out what it looks like beneath the ground.

“What we do is we create a seismic source, a sound wave, and it reflects on the subsurface, and we record it,” Alexander said.

That seismic source is a huge vehicle that rolls over the snow-covered tundra and vibrates the ground. A recording device, similar to a microphone, measures the signal that comes back.

“We then take that recorded signal, and we use physics and mathematics to turn that into an image,” said Alexander, “in very much the same way that you would take a picture from your digital camera, when it records ones and zeroes into an image, we do that in a very similar way.”

The picture will give BP the best, most detailed, data yet on what’s going on in the layers of rock far beneath the tundra and where to find the remaining oil.

Efforts like this have paid off for the company. After years of decline, BP has managed to flatten production at Prudhoe Bay; its new mantra is “40 more.”

Digert said that while other companies like ConocoPhillips and Hilcorp are working to bring new oil fields online, BP thinks it’s important to keep Prudhoe Bay going.

“There’s a lot of space in the trans-Alaska pipeline right now, so there’s lots of room to get more oil off the Slope,” Digert said. “But we do have to have that critical volume of oil going down the pipeline.”

Digert said this winter’s 3-D seismic program will guide the next decade of drilling, helping BP squeeze every last drop out of Alaska’s biggest oilfield.

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Elizabeth Harball is a reporter with Alaska's Energy Desk, covering Alaska’s oil and gas industry and environmental policy. She is a contributor to the Energy Desk’s Midnight Oil podcast series. Before moving to Alaska in 2016, Harball worked at E&E News in Washington, D.C., where she covered federal and state climate change policy. Originally from Kalispell, Montana, Harball is a graduate of Columbia University Graduate School of Journalism.

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