Geoscience Reference
In-Depth Information
sources of CO
2
; and (2) saline reservoirs have potentially the largest reservoir
capacity of the three types of geologic formations.
Advantages and Disadvantages
Although deep saline reservoirs potentially have huge capacity to store
CO
2
, estimates of lower and upper capacities vary greatly, reflecting a higher
degree of uncertainty in how to measure storage capacity.
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Actual storage
capacity may have to be determined on a case-by-case basis. Estimates of
storage capacity for the United States from the DOE Regional Sequestration
Partnership Program are discussed below.
From estimates of the potential storage capacity in saline reservoirs, it is
likely that the vast majority of CO
2
injected underground would be stored in
these formations, assuming that CCS were deployed on a commercial scale
across the United States. In addition to their potential capacity, deep saline
reservoirs underlie large portions of the country, and could be more easily
accessible to large, stationary sources of CO
2
than oil and gas reservoirs or
coal seams.
Figure 1
shows broad outlines of sedimentary basins containing
the deep saline reservoirs, and the locations of a variety of stationary sources
of CO
2
.
The DOE Regional Sequestration Partnership Program has conducted
simulations, field studies, small-scale injection projects, and is now beginning
a phase of large-scale injection demonstration projects to investigate the
suitability of deep saline reservoirs.
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Because of the potentially vast amounts
of CO
2
that could be sequestered, these experiments could shed light on the
potential for leakage of CO
2
from the reservoir, and test the ability to detect the
movement of CO
2
underground as well as to detect leaks through overlying
cap rocks.
In addition to the possibility of CO
2
leakage, injection of millions of tons
of CO
2
will displace large volumes of brine in the deep saline reservoirs. One
disadvantage is therefore the possibility that displaced brine could leak into
underground sources of drinking water. Ultimately, CO
2
will likely dissolve
into the brine, but that could take decades.
Also, injecting large volumes of fluid into the subsurface has the potential
to trigger earthquakes, especially if the CO
2
is injected into an undetected
fault. Presumably, evaluating the potential storage site prior to beginning
injection will limit the potential for triggering earthquakes (also referred to as
―induced seismicity‖), but there is no guarantee that fluid could not migrate to
faulted or fractured rocks over the course of many years and induce an
earthquake.
