Capture, Costs Part of Equation
CO2 Answers Are as Elusive as CO2
Today’s high product prices and demand for oil make tertiary recovery projects important and even necessary.
Carbon dioxide injection, better known as CO2 flooding, is a technique of choice for enhanced recovery from older oil fields.
At the same time, concern about global warming has generated intense interest in carbon sequestration – injecting CO2 into deep reservoirs for storage.
So it’s high irony that CO2 tertiary recovery projects and sequestration research are stymied by the same, restrictive problem:
There isn’t enough CO2.
“It’s ridiculously expensive to extract the carbon dioxide in the purity that’s required for CO2 injection,” said Gareth Roberts, president and CEO of Denbury Resources Inc. in Plano, Texas.
“Not all CO2 is created equal. It depends on what it’s mixed with, and the pressure is also important,” he added.
Denbury Resources draws on a natural CO2 supply from Jackson Dome, near Jackson, Miss., to feed most of its tertiary recovery projects.
Roberts said the oil industry needs CO2 of 98 percent purity or more for enhanced recovery, to ensure miscibility for oil production.
Commercial supplies of CO2 used in the food and beverage industry also are available, but they are even more pure and vastly more expensive, according to Jim Drahovzal, senior research geologist for the Kentucky Geological Survey in Lexington, Ky.
Drahovzal will serve as technical program chair for the AAPG Eastern Section annual meeting, “Winning the Energy Trifecta,” Sept. 16-18 in Lexington.
The meeting includes a Sunday workshop on carbon dioxide flooding for EOR followed by two morning sessions on CO2 sequestration.
He recalled talking to a commercial supplier who could deliver a useful amount of beverage-quality CO2.
“The best price I understood was $90 per ton, delivered in one of these 20-ton tankers,” Drahovzal said.
“It’s a considerable thing when you’re thinking about a 3,000-ton pilot,” he noted, “like some people are talking about for these regional pilot projects.”
Today’s News: Wait
Behind most of the current interest in carbon sequestration is an assumption: The United States will require power plants and other industries to capture the CO2 they produce.
But that hasn’t happened yet, so there’s no significant capture of carbon dioxide for research purposes or injection.
“The whole thing is kind of waiting right now in terms of legislation concerning CO2, in terms of mitigating that to the atmosphere,” Drahovzal said.
For that reason, many people working on CO2 injection are looking at a 10-year time frame to develop CO2/tertiary recovery flooding and CO2/carbon sequestration on a large scale.
Roberts said Denbury Resources can recover natural CO2 for $2 to $3 per ton. It contracts for captured, by-product CO2 for about 1.5-to-two times that amount – roughly $3 to $6 per ton.
A tax on carbon emissions could persuade power generators and other CO2 producers to capture carbon dioxide, but it would have to be a stiff tax, he said.
An alternate system of capping emissions and allowing companies under the limits to sell offsets also could lead to CO2 capture, at a lower per-ton produced cost, Roberts noted.
“The carbon tax that would be required would be on the order of $3 an Mcf, which is on the order of $50 a ton, while the cap-and-trade would be something like $20 a ton,” he said.
A Costly Project
Sean Plasynski is sequestration technology manager for the U.S. Department of Energy’s National Energy Technology Laboratory (NETL) office in Pittsburgh.
He’s faced with the problem of getting CO2 supplies for injection research, and he acknowledged the cost of capturing produced carbon dioxide.
“Capture costs can be very expensive,” he said. “To put in a main scrubber (in a power generating plant) can create an increase in electricity cost of 75 percent.”
Beyond that, there’s a transportation cost to move the CO2 to an injection site or tertiary recovery project.
“In most cases you don’t have a power plant sitting right on top of a producing field,” Plasynski noted.
Drahovzal said new research targets CO2 production from clean-coal technologies. One of those is Integrated Gasification Combined Cycle (IGCC), where coal is gasified and power plants produce electricity from both gas turbines and heat-recovery steam turbines.
“A lot of people are interested in seeing if we can separate CO2 from things like IGCC or coal-to-liquid units. In both cases, those units would produce a pure stream of CO2,” he said.
NETL research into sequestration has a $100 million budget split between core research and development and infrastructure projects, according to Plasynski.
The core R&D work includes:
- Methods of capturing CO2.
- Direct and geologic storage.
- Breakthrough concepts that improve economics.
- Work with other produced gases, like methane.
- Injection monitoring, measurement and verification.
The infrastructure work includes seven regional sequestration programs involving all but nine of the U.S. states.
“There’s really no silver bullet here. All these things need to work together,” Plasynski said.
Aside from the problem of getting CO2 for injection research, he has to identify potential reservoirs for long-term carbon dioxide storage.
“First, you have to capture it before you can store it,” he said. “But even if you could capture it for nothing, you better have a place to store it.”
Drahovzal said reservoir characterization is a significant problem in planning CO2 injection for carbon sequestration.
“We’ve been looking at sequestration potential for six years,” Drahovzal said. “The problem is, many times we don’t have good reservoir data.
“The other thing that worries us is fracturing. In many cases we don’t know if they connect to the surface, or if they might connect to aquifers,” he added.
Not every existing oil reservoir can be considered a candidate for CO2 injection for storage, Plasynski said.
“You don’t want to be in an active fault location. You want a deep reservoir with good, impenetrable caprock above it,” he noted.
“You want it to be deep enough, because when you put CO2 in it in a supercritical state, you want it to stay that way,” he said.
But a secondary recovery waterflood doesn’t eliminate a reservoir from consideration.
“A field that has a lot of injection wells is fine, as long as those have been filled,” Plasynski said.
It Makes Cents
When carbon sequestration can be linked to tertiary oil recovery, the economics improve dramatically, although recovery project economics are sensitive to CO2 pricing.
“It’s the other side of the story, and the side that makes more sense,” Roberts said.
He sees existing fields as prime candidates for CO2 storage – if there is a future emphasis on carbon sequestration.
“They’ve trapped oil and gas for millions of years, and they’ll probably trap CO2 for that long, also,” he said.
Denbury Resources operates primarily in Mississippi, Alabama, Louisiana and Texas.
“The cheap oil is all gone – it’s a peak oil issue,” Roberts said. “It’s important to get all the oil out of the ground you can, especially in friendly places like the southern United States.
“They are very interested in increasing production from these older fields,” he noted. “And they are happy to register these sites as sequestration sites.”
Roberts said his company negotiates for new sources of CO2 supply in addition to Jackson Dome, and operates a transmission system for its tertiary recovery projects.
“We move about 500 million cubic feet of CO2 a day and plan to increase that to one billion,” he said. “We’re flooding a dozen fields.
“Just with the sources we’re negotiating with now and with the new-builds, we could probably produce man-made resources of up to 2 Bcf/day,” he added.
Needed: Geologists to the Debate
While Roberts is enthused about CO2 injection for enhanced oil recovery, he’s less optimistic about carbon sequestration to combat emissions.
“The whole idea of capturing CO2 – if you look at what’s going on around the world, the amount that’s likely to be sequestered is just a drop in the bucket,” he observed.
Sequestration also will contend with both technical and legal issues: “The legal definition of where the gas goes is a problem, unless you own the land for many miles in every direction, ” he said.
Despite the many challenges, CO2 injection for enhanced recovery and sequestration probably will attract even more attention in the coming months and years.
“In a sense we’re not very far down the track, but now everyone is becoming concerned,” Drahovzal said. “And they’re so concerned that they want answers tomorrow.
“All of a sudden, there’s a lot of money being thrown at this thing,” he added.
And it’s clear the future of CO2 injection will require a large number of well-trained, specialized geologists who understand reservoirs.
“The geologists need to get involved in the debate,” Roberts said.
“Most people involved in CO2 injection are not geologists and don’t understand what happens when you inject it into the ground,” he observed.
That’s becoming a problem as CO2 legislation emerges without input from the larger scientific community.
“Ordinary people don’t understand the physical world, yet they’re making rules and passing laws based on that lack of knowledge,” Roberts said.
Drahovzal recalled listening to a speaker who claimed research into CO2 injection and sequestration is today’s equivalent of the nuclear research Manhattan Project.
“That may be overblown,” he said, “but it’s going to take a lot of really high-tech people in both engineering and geology to make this thing go.”