Enhanced oil recovery methods outlined

U.S. Department of Energy funds numerous EOR research projects

Patricia Jones

PNA Contributing Writer

For years, U.S. Department of Energy researchers have collaborated with industry to study various techniques to improve production levels from oil and gas deposits.

Charles Thomas, Ph.D., a U.S. Department of Energy representative who has participated in a number of different enhanced oil recovery studies, presented an overview of such government-funded research during an energy workshop held at the University of Alaska Fairbanks on April 11 and 12.

Researchers have come to some general conclusions about enhanced oil recovery techniques, he said, some of them fairly obvious to the oil and gas industry.

“The reality is that recoverable effectiveness of methods are lower in the field than in the lab,” Thomas said, generating a substantial amount of laughter from the more than 100 industry, government and university personnel attending first day of the workshop.

“We have also learned that we have to understand the geology of our target reservoir,” he added.

Knowledge about underground structures and formations hosting crude is necessary to develop appropriate recovery methods, he said. “It doesn’t matter how good the project is if you can’t contact the oil to sweep it up.”

Finally, Thomas praised the use of certain chemicals injected underground to increase oil recoveries. “The small slugs of high contact chemicals do work well, and if you can control them, you can have an economic recovery.”

Yet the most common methods of enhanced oil recovery involve thermal steaming and the injection of gas liquids, he said.

EOR methods outlined

One process he described was steam flooding, injecting steam into the underground formation. As the steam cools, it condenses to water. “In the same process, it heats the oil and causes it to flow.”

In situ combustion achieves the same result, Thomas said, except that air is injected into the reservoir to create a combustion front.

He briefly talked about gas flooding, which involves injecting natural gas liquids or even CO2 into underground reservoirs to increase oil flow. This technique works on the North Slope, Thomas said, because of the large quantities available. “This is just a case of looking at the specific needs and having the opportunity to take advantage of it.”

“What we usually find in carbon dioxide flooding or any other gas project is that you use the gas — CO2, nitrogen or injectant, followed by water, followed by another slug, followed by water,” he added.

Researchers have also tested the injection of certain chemicals, which will contact crude oil and help to mobilize it.

“In this process, to protect your polymers you have to pre-flush the reservoirs, then inject the chemicals,” Thomas said. “These are the kinds of innovative technologies that we’ve been working on for many years.”

Finally, researchers have also investigated the use of microorganisms in a process similar to the chemical injectant method. “It’s complicated like the chemical processes, but with this, you also have micro-organisms to manage.”

EOR benefits North Slope producers

“Prudhoe Bay got into gas and water injection — it started very early (in the field’s life), which was the right thing to do,” he said. “As technology came along, it was either applied or developed at Prudhoe Bay, where it was all put together in a very intelligent way.”

At the start of Prudhoe Bay’s development, producers estimated the field contained about 9 billion barrels of recoverable crude, Thomas said. “By 1986, this had already increased to 10.2 billion, with the introduction of these technologies of recovery,” he said. “In 2000 it was up to around 13 billion barrels and now it’s over 14 billion.”

Miscible injectant projects at Kuparuk have also helped to increase production at that field, which contains some heavy oil deposits.

Continued research is focused on heavy oil, Thomas said.

“Outside of finding new fields, we’re looking at enhanced oil recovery in heavy oils, which is a major target of about 25 to 30 billion barrels of oil,” he said. “Maybe 3 to 6 billion barrels is a reasonable target — we certainly hope so.”

Continuing the flow of crude oil through the trans-Alaska pipeline is crucial to the North Slope oil industry, Thomas said.

“As oil throughput declines, tariffs continue to go up,” Thomas said. “It’s important to maintain throughput … important not just for new projects, but it’s important to everything existing on the North Slope.”