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Experiment seeks answers on burying
carbon dioxide deep underground

For more than a century, Texans have made fortunes by extracting oil from under the Lone Star soil.

Now, a group of University of Texas at Austin geologists will put a byproduct of burning oil—carbon dioxide (CO₂)—back into the ground to keep it from building up in the atmosphere.

In September, the project, called the Frio Brine Experiment, will inject carbon dioxide into underground brine-saturated formations.

Workers on the Frio project drilled a well more than 5,700 feet underground in which to inject carbon dioxide.

Then the researchers will monitor it to measure the differences between predicted and observed performance, said Sue Hovorka, a research scientist at the university’s Bureau of Economic Geology and the project’s principal investigator.

“We want to get as much substantive information out of it, make as much progress on the understanding and the demonstration of the technique with a small budget, a small impact and a short period of time,” she said.

The process is called carbon sequestration and the Bush administration has identified it as a priority area of energy and environmental research.

“Our goal is to develop a suite of carbon management options that we know are safe, affordable and effective,” U.S. Energy Secretary Spencer Abraham has said. “We want to have these options ready should the science tell use that large-scale carbon reductions are necessary in the future.”

CO₂ is a naturally occurring gas that is essential to life and not harmful in most cases.

In large concentrations, however, it becomes a greenhouse gas that has been linked to global warming. Scientists have calculated that about 7 billion tons of CO₂ from manmade sources are released into the atmosphere each year. That includes emissions from gas-powered vehicles and the smokestacks of factories.

Subterranean space

Is there enough room underground for large volumes of carbon dioxide?

“That’s the first question,” Hovorka said. “And yes, there’s lots of space.”

The BEG geologists have quantified the properties of dozens of suitable sites around the country. “The upshot was that we decided, like true Texans, the best sites were here” along the Gulf Coast of Texas and Louisiana, she said.

For the experiment, the researchers selected an oil field in Liberty County, about 30 miles northeast of Houston. The research well is owned by Texas American Resources, an oil company owned by University of Texas at Austin petroleum engineering graduates.

Sue Hovorka, a research scientist at the university’s Bureau of Economic Geology and the project’s principal investigator.

The project name comes from the formation selected to host the injection, the upper Frio Formation of Oligocene age. The Frio sandstones in this field are representative of the kind of formation that underlies much of the Gulf Coast, and if the experiment is successful will prepare for the possibility of CO₂ injection over a wider area.

The test area is geologically separated by faults and sealing shales that will keep the carbon dioxide from seeping into other areas.

Carbon dioxide has long been injected into declining oil wells to extract oil clinging to pores in the rock. That carbon dioxide, however, usually is extracted from the well and used in another well.

While an oil field will serve as the laboratory for the project, the CO₂ won’t be injected in an oil-producing zone. It will be put into brine-bearing formations above the oil-producing zone. Drilling of the well for the injection was completed in June to a depth of 5,753 feet. The purpose of injecting into a rock-brine system is to facilitate modeling and monitoring of the injection by reducing the number and complexity of variables.

A first

This is the first experiment to closely monitor the capacity of the subsurface to store injected CO₂.

The concept of storing CO₂ underground has been around for some time. Statoil, the oil exploration and production company of Norway, has been injecting CO₂ extracted from natural gas into brine-bearing formation below the North Sea.

“The experiment is conceptually simple—we are collecting a broad spectrum of measurements under current conditions, will inject the CO₂ and repeat the same measurements to observe changes,” Hovorka said. “We will then match observed changes to modeled changes to improve our ability to predict what happens as CO₂ is injected. But it will set the stage for bigger, more ambitious sequestration projects.

Rob Trautz of the Lawrence Berkeley National Laboratory prepares a tracer solution for injection into the well. For up to two weeks, researcher will monitor the time it takes for the tracer to break through. Time-to-breakthrough is a function of some of the aquifer hydraulic properties that also will control flow behavior of injected CO2.

The budget is $3.4 million for the UT activities, plus about $1.5 to $2 million for experiments brought to the site by other institutions and companies.  It is a small budget for this type of geologic field study.

The Frio Brine Experiment is one of the Department of Energy’s most prestigious experiments that they nominated for international recognition by the ministerial-level Carbon Sequestration Forum.

The expectation is that most of the CO₂ should stay underground for thousands of years, leaking out so slowly that it can’t be detected above normal levels of carbon dioxide in water and soils.

“The more people see of it, the less of a wild-eyed, radical idea it is,” she said. “The more it seems like, ‘Yeah, we could do that,’” she said. “Which is a good role for the university to have. Take these things that are today wild-eyed, radical ideas and lay out all the pros and cons and the details and let all the stakeholders acquaint themselves with it and see how it could be done.”

More expertise

The bureau’s partners in the project are GEO-SEQ, a research consortium which includes the Lawrence Berkeley, Lawrence Livermore and Oak Ridge national laboratories  and the Alberta (Canada) Research Council; the National Energy Technology Lab (NETL) in the Department of Energy; the U.S. Geological Survey; Sandia Technologies LLC; Texas American Resources; Schlumberger; and BP; the Department of Petroleum Engineering at The University of Texas at Austin; Praxair Inc.; and the Australian Cooperative Research Centre for Greenhouse Gas Technologies. Funding comes from the NETL.

“The labs are bringing the latest tools” with which to measure what’s happening underground, Hovorka said.

The monitoring will show how the carbon dioxide interacts with the other substances below the surface, how it moves, where it goes, how it changes and doesn’t change.

“We’ll monitor gas movement with seismic, we’ll monitor water, we’ll monitor everything,” Hovorka said. “That’s the point.”

The field project, however, will focus on the geology subsurface performance of CO₂. Other questions that need to be answered before geologic sequestration can be widely implemented include the economic feasibility and building out infrastructure to get CO₂ from factories to the field. To answer these questions the Bureau has developed a research consortium, the Gulf Coast Carbon Center, which is funded by BP, Chevron Texaco, Kinder-Morgan, Praxair and the Jackson School of Geosciences.

The Frio Experiment will proceed with injection in September.

The researchers will use food-grade CO₂, the kind used to put the fizz in soft drinks and other beverages. In fact, the CO₂ injection had been planned for the spring, but none was available. It was going into drink production as bottlers prepared for the summer.

Tim Green
Photos: Bureau of Economic Geology

Related Sites

Frio Log Archive
Bureau of Economic Geology
Jackson School of Geosciences
Carbon dioxide injected underground in experiment, testing potential way to cut amount in atmosphere - 5 October 2004
Report could help producers pump more oil from famed Permian Basin - 1 July 2004 Department of Energy's Carbon Sequestration Research Program