[Mb-civic] Less CO2, AND More Oil--Yowsa!

[Jim Burns]

This sounds fantastic, and makes one wonder if this is being explored in
the U.S., as well....
 
SCIENCE
Edward Willett
 
"In with the CO2, out with the oil"

 
A well is a hole in the ground. Sometimes it has water in it. Sometimes
it has oil in it. But increasingly, in southeastern Saskatchewan, it has
carbon dioxide (CO2) in it.
 
Apache Canada Ltd. recently began injecting CO2 into its oilfield in the
Midale area. EnCana has been injecting CO2 into the Weyburn oilfield
since 2000.
 
They're not doing it just for the fun of it, of course. Pumping CO2 into
those oil fields also pumps new life into them, by allowing more oil to
be pumped out of them.
 
The Weyburn oilfield covers more than 180 square kilometers, and the 1.4
billion barrels of oil it's estimated to have contained when discovered
in 1954 makes it one of the largest medium-sour crude oil reservoirs in
Canada.
 
Getting all the oil out of any oilfield is a challenge. Some can be
readily pumped out just by drilling a hole in the ground—but an oil
well's peak production usually lasts only one to three months, then
slows. You can drill new wells for a while, but eventually, production
from the entire field tapers off.
 
The next step is usually waterflood injection: water is pumped into the
reservoir to increase its pressure and push oil to existing wells.
Weyburn went on waterflood in 1964.
 
In the Weyburn field, oil is retained in two very different layers of
rock: the Marly zone, made of a chalky dolomite, and, underneath it, the
Vuggy zone, made of highly fractured (and thus highly permeable)
limestone. Water did a fine job of flushing oil from the Vuggy zone, but
didn't make much headway in the much tighter Marly zone.
 
CO2 miscible flood technology injects not water, but almost pure, highly
pressurized carbon dioxide. It's "miscible" because the CO2 actually
mixes with the oil. In effect, it become carbonated—and just like any
other carbonated liquid, it expands.  (Think of a what happens when
you open a shaken can of pop.) This forces it through the tight openings
in the rock and to the waiting extraction wells. The process is also
helped by the fact that the oil/CO2 mixture is less viscous than the oil
by itself, and by the fact that the mixture acts as a solvent,
dissolving some of the rock and thus making it more porous.
 
The results are impressive. With waterflood technology, the field is
thought to have given up about 30 percent of its overall contents. CO2
miscible flood technology should boost that to 46 percent—or, to put
it another way, an additional 130 million barrels of oil should come out
of the Weyburn field over the next 30 years, with production reaching
30,000 barrels of oil per day by 2008, compared to just 10,000 barrels
of oil per day without CO2 injection.
 
Apache's forecasts for its Midale unit are similar. The Midale oil pool
was discovered in 1953; Apache's Midale Unit was formed in 1962 as a
waterflood project. To the end of 2004, 131 million barrels of an
original 515 million barrels in the unit had been recovered; CO2
injection is expected to result in another 45 to 46 million barrels of
recoverable oil.
 
The CO2 comes from the Great Plains Synfuels Plant, located near Beulah,
North Dakota. Built during the 1970s energy crisis, it is the only
active plant in the U.S. that produces synthetic natural gas from coal.
The CO2, derived from one of the plant's products previously sold as a
low-value fuel, is delivered through a 325-kilometre pipeline.
 
Five thousand tonnes of CO2, which would otherwise have gone into the
atmosphere and contributed to global warming, is injected into the
Weyburn field every day. Over the 30-year lifetime of the project 20
million tonnes will be sequestered; another 8.75 million tonnes will be
sequestered in the Midale reservoir. Since, on average, each Canadian's
activities results in the release of 4.5 tonnes of CO2 a year into the
atmosphere, and Saskatchewan's population is around one million, you
could say the two projects will together lock away the equivalent of
more than six year's worth of the entire province's carbon dioxide
emissions.
 
And according to a study conducted by Regina's Petroleum Technology
Research Centre—the first large-scale study in the world on the
geological storage of CO2 in a partially depleted oil field—only 0.2
percent of that CO2 will find its way into the atmosphere in the next
5,000 years.
 
More energy, less pollution: not bad for a bunch of holes in the ground.
     
Edward Willett is a freelance writer in Regina, Saskatchewan, Canada.
E-mail comments or questions to ewillett at sasktel.net. Ed's website is
www.edwardwillett.com, and his blog is at edwardwillett.blogspot.com.
Ed's latest novel is the exciting science-fiction adventure Lost in
Translation (Five Star, ISBN 1594143056 ); his latest non-fiction
book is Genetics Demystified (McGraw-Hill, ISBN 0071459308).