[Editors] MIT: Safe storage of greenhouse-gas carbon dioxide

[Elizabeth Thomson]

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Burying the greenhouse gas:
--New MIT tool could aid safe underground storage of CO2
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For Immediate Release
MONDAY, NOV. 17, 2008

Contact: Elizabeth A. Thomson, MIT News Office
E: thomson at mit.edu, T: 617-258-5402

Photo and Graphic Available

***EDITORS, PLEASE NOTE: The following release is one of two you will  
be receiving about MIT research to be presented tomorrow, Nov. 18, at  
the 9th International Conference on Greenhouse Gas Control  
Technologies***



WASHINGTON, DC — To prevent global warming, researchers and  
policymakers are exploring a variety of options to significantly cut  
the amount of carbon dioxide that reaches the atmosphere. One possible  
approach involves capturing greenhouse gases such as carbon dioxide at  
the source — an electric power plant, for example — and then injecting  
them underground.

While theoretically promising, the technique has never been tested in  
a full-scale industrial operation. But now MIT engineers have come up  
with a new software tool to determine how much CO2 can be sequestered  
safely in geological formations.

The work will be reported Nov. 18 at the 9th International Conference  
on Greenhouse Gas Control Technologies (GHGT-9), to be held Nov. 16-20  
in Washington, D.C.

According to the 2007 MIT study, “The Future of Coal,” and other  
sources, capturing CO2 at coal-burning power plants and storing it in  
deep geological basins will mitigate its negative effects on the  
atmosphere.

However, injecting too much CO2 could create or enlarge underground  
faults that may become conduits for CO2 to travel back up to the  
atmosphere, said Ruben Juanes, assistant professor of civil and  
environmental engineering (CEE) and one of the authors of the work.  
“Our model is a simple, effective way to calculate how much CO2 a  
basin can store safely. It is the first to look at large scales and  
take into account the effects of flow dynamics on the stored CO2,” he  
said.

Already Juanes and co-author CEE graduate student Michael L.  
Szulczewski have applied their model to the Fox Hills Sandstone in the  
Powder River basin straddling Montana and Wyoming. They found that the  
formation would hold around 5 gigatons of CO2 — more than half of all  
the CO2 emitted by the United States each year.

A geological basin is a large underground bowl between 100 and 1,000  
kilometers wide and 5,000 kilometers deep that has filled over  
millennia with layers of sand, fine-grained clays, and other sediments  
that are eventually consolidated into porous rock. Some of the layers  
contain brine and are called deep saline aquifers. CO2 would be  
injected into the aquifers through wells.

The MIT model predicts how much a plume of CO2 will migrate from its  
injection well and the path it is likely to take due to underground  
slopes and groundwater flow.

“A lot of people have done studies at small scales,” Szulczewski said.  
“If we’re going to offset emissions, however, we’re going to inject a  
lot of CO2 into the subsurface. This requires thinking at the basin  
scale.”

“Despite the fact that our model applies at the basin scale, it is  
very simple. Using only pen and paper, you take geological parameters  
such as porosity, temperature and pressure to calculate storage  
capacity,” Szulczewski said. “Other methods suffer from major  
shortcomings of accuracy, complexity or scale.”

Juanes studies a phenomenon called capillary trapping, through which  
CO2, liquefied by the pressure of the Earth, is trapped as small blobs  
in the briny water (picture bubbles of oil in vinegar). The CO2  
dispersed throughout the basin’s structural pores eventually dissolves  
and reacts with reservoir rocks to precipitate out into harmless  
carbonate minerals.

CO2 has been sequestered in small pilot projects in Norway, Algeria  
and elsewhere. In 2004, 1,600 tons of CO2 were injected 1,500 meters  
into high-permeability brine-bearing sandstone of the Frio formation  
beneath the Gulf coast of Texas. Current proposals call for injecting  
billions of tons within the continental United States.

The GHGT-9 conference is organized by MIT in collaboration with the  
IEA Greenhouse Gas R&D Programme (IEA GHG), with sponsorship from the  
U.S. Department of Energy.

This research was supported by the McClelland Fund, administered by  
the MIT Energy Initiative, and by the Reed Research Fund.

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