MRCSP Phase I Geologic Characterization Report - Midwest ...

44 CHARACTERIZATION OF GEOLOGIC SEQUESTRATION OPPORTUNITIES IN THE MRCSP REGION
Table 19.—Potsdam Sandstone estimated effective
CO 2-storage capacity by state (in gigatonnes)
State Area (mi 2 ) Total
Ohio 18 0.002
Pennsylvania 9,280 1.704
Total 9,298 1.706
Table 21.—Rome trough sandstones estimated effective
CO 2-storage capacity by state (in gigatonnes)
State Area (mi 2 ) Total
Eastern Kentucky 13,157 1.001
Ohio 201 0.006
West Virginia 5,094 0.221
Total 18,452 1.228
Table 20.—Unnamed Conasauga sandstones estimated effective
CO 2-storage capacity by state (in gigatonnes)
State Area (mi 2 ) Total
Eastern Kentucky 25 0.001
Michigan 409 0.164
Ohio 21,185 3.469
Pennsylvania 2,410 0.459
West Virginia 943 0.0161
Total 24,973 4.255
Table 22.—Mt. Simon Formation estimated effective
CO 2-storage capacity by state (in gigatonnes)
State Area (mi 2 ) Total
Eastern Kentucky 6,661 4.336
Indiana 18,957 80.612
Michigan 40,530 112.839
Ohio 19,768 19.390
Total 85,916 217.177
by the St. Peter Sandstone and the “Clinton”/Medina/Tuscarora
Sandstones. The deep saline formations with the smallest potential
are the Potsdam Sandstone and basal sandstone in the Rome trough
in eastern Kentucky. The low potentials stem from assigning these
two aquifers very low porosities, since porosity generally decreases
with depth, and both units are deeply buried. In addition, because
of the lack of exploratory wells in many areas, such as in the deepest
portion of the Appalachian basin in Pennsylvania, some areas
contained no data and could not be mapped (see the structure and
isopach maps of Appendix A). This also accounts for much of the
small potential of the basal sandstones. The unnamed sandstones in
the Conasuaga were also assigned a low porosity, since initial studies
indicated the primary lithology of the Conasauga in eastern Ohio
and western Pennsylvanian is a sandy or silty dolomite.
It is perhaps useful to compare the estimated capacities in this
study with some other assessments. An assessment of the Mt. Simon
Sandstone (including areas outside MRCSP) by Gupta and others
(2001) showed a capacity range of 160 to 800 gigatonnes based on
a porosity range of 5 to 25 percent, net-to-gross-ratio of 50 to 95
percent, and storage efficiency of 6 percent. In the same study, the
capacity range for 8.5 percent porosity was 195 to 371 gigatonnes.
This compares well with the estimated 10 percent capacity number
of 217 gigatonnes for Mt. Simon in the MRCSP region in this
study. Similarly, the Rose Run sandstone capacity range of 9 to 43
gigatonnes of Gupta and others (2001) is comparable to the 49 gigatonnes
estimated in the current study.
Estimated CO 2 sequestration capacity in the Devonian Ohio
Shale (Cleveland to Lower Huron Members) and equivalents in
the Appalachian basin and the Antrim Shale in the Michigan basin
ranges between 23.2 and 88.3 gigatonnes, varying between CO 2 adsorption
rates of 22 and 84 standard cubic feet of gas per ton (U.S.)
of shale. Capacity estimates for the black shales in eastern Kentucky
represent only that part of the shale in the MRCSP region. The 90 th
percentile figures calculated for Ohio, Pennsylvania, and West Virginia
seems overly optimistic. The gray shales and intertonguing
siltstones characteristic of the Devonian shale in these states may
not have a sufficient organic matter content to adsorb such large volumes
of CO 2. More realistically, the sequestration capacity is likely
in the calculated range between the 10 th and 50 th percentiles. All of
these estimates are, of course, contingent on the injectivity of CO 2
into the shale, which is untested.
For the oil-and-gas fields, the fields are separated into those that
are less than 2,499 feet in depth and those that are greater than 2,500
feet in depth (762 m). The 2500-foot depth cutoff roughly corresponds
to the predicted transition from the gaseous phase to the super-critical
phase of CO 2, which is approximately 260 times denser
than the gaseous phase and, therefore, more desirable.
Solubility Storage
While solubility storage is described in this document, it is not applied
in this study, since most of the initial sequestration will occur
as volumetric storage. Instead, one representative calculation was
conducted for the project. The solubility capacity was calculated for
Mt. Simon Sandstone of Indiana, Michigan, and Ohio. The potential
CO 2-storage capacity using the solubility calculation is in excess of
83 gigatonnes, while the potential storage capacity using the volumetric
calculations is over 217 gigatonnes, an increase by a factor
of 2.6. However, an interesting phenomenon occurs in the solubility
calculation. In the center of the Michigan basin, there is no solubility
capacity. This is because the modeled salinity is too high to allow
CO 2 to dissolve into the formation fluids. The high salinity, generally
increasing salinities with depth, and the low solution rates indicate
that solubility storage will not be a near-term factor in sequestering
CO 2 in the MRCSP area. As a comparison, Dooley and others (2004)
used the solubility approach to estimate that the total storage capacity
in the Mt. Simon Sandstone, including all of the Illinois basin and
the Appalachian basin is approximately 225 gigatonnes.