MRCSP Phase I Geologic Characterization Report - Midwest ...

APPENDIX A: CAMBRIAN BASAL SANDSTONES
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basal sandstones, Conasauga sandstones, and Potsdam Sandstone of
eastern Ohio, West Virginia, and Pennsylvania range from 50 to 150
feet. However, this is a total thickness of the interval; the amount
of porous/permeable sandstone within the interval is uncertain and
is highly variable and discontinuous. A recent deep well in Mason
County, West Virginia encountered less than 10 feet of porous/
permeable sandstone within this interval.
Within the Rome Trough, the basal sandstones appear to thicken
southward independent of major faults, indicating that the sandstones
may be pre-rift deposits unaffected by movement on the
major bounding faults of the Trough. Post-depositional structural
movement, however, influenced depth and local thickness preservation
(Harris and others, 2004). Some of the variability in thickness
may also indicate structural influences from localized faulting, especially
where there are substantial thickness changes in the basal
sandstone across relatively short distances.
DEPOSITIONAL ENVIRONMENTS/
PALEOGEOGRAPHY/TECTONISM
During late Precambrian and early Paleozoic time, the MRCSP
states were part of a large crustal plate, named Laurentia, which
occupied a position straddling the equator (Dott and Batten, 1976).
Laurentia included the present-day Canadian Shield and possibly
the Transcontinental arch. In late Precambrian time, the Laurentian
plate rifted away from an adjacent plate, creating the Iapetus Ocean
between them (Dietz, 1972). At this time, the southern margin of
Laurentia became a passive continental margin. During early and
middle Cambrian time, the Grenville rocks in what is now the Appalachian
basin states remained exposed to erosion. Deposition of
sand on the Precambrian unconformity began late in the Middle
Cambrian as sea level rose and the southern margin of Laurentia began
to subside in response to the sediment loading. During the Lower
or Middle Cambrian, the Rome trough formed along the southern
margin of Laurentia. Harris (1978) described the Rome trough as
the failed arm of a triple junction (an aulogen), extending from the
Mississippi embayment through Kentucky to Pennsylvania. The
aulacogen is thought to have originated on incipient Precambrian
crustal-block faults derived from stresses during the opening of the
Iapetus Ocean. Thus, the basal sandstones interval of the MRCSP
study area is a transgressive sequence of sandstone, shales and
carbonates deposited on the regional Precambrian uncomformity
surface. Both lower and upper boundaries are highly diachronous,
making regional correlations difficult and tenuous at best. The basal
sandstones in the Rome trough are not correlative to the Mt. Simon
and unnamed Conasauga sandstones. The Mt. Simon and unnamed
Conasauga sandstones are considered younger than the unnamed
basal sandstones of the Rome Trough.
Depositional environments for the basal sandstones range widely,
from marginal marine, to marine, littoral, fluvial, and estuarine
(Jannssens, 1973; Driese, 1981; Haddox and Dott, 1990). The
marine influence is evident where sandstone intertongues with dolostone
in the Appalachian basin area. In the Rome trough, red and
green shales and siltstones with nodular evaporates interlayer with
the sandstones, suggesting very shallow, subtidal to intertidal deposition,
with restricted marine circulation (Harris and others, 2004).
The regional shoreline generally migrated northward from the
proto-Illinois/Michigan basin, Rome trough and eastern proto-Appalachian
basin to the Canadian shield during transgression (Milici
and de Witt, 1988).
SUITABILITY AS A CO 2
INJECTION TARGET OR SEAL UNIT
The lithology of the intervals mapped varies, from the typical Mt.
Simon Sandstone in western Ohio, Indiana, and Michigan to the
basal shaley and arkosic sandstones of the Rome trough and sandy
dolostones of the unnamed Conasauga sandstones. The Mt. Simon
has overall higher porosity and permeability based on core analyses
and a 35-year history of relative higher injectivity rates and volumes
than the unnamed Conasauga sandstones. Data for the basal sandstones
of the Rome trough is scant.
The Mt. Simon of the Indiana-Ohio platform has good to excellent
reservoir quality - gross thickness (200 to 350 feet), porosity
(average 14 percent), and permeability (range 10 to 200+ millidarcies
[md]) (Janssens, 1973; Clifford, 1975). Salinity ranges from
111,000 to 316,000 milligrams per liter (mg/L) with an average
specific gravity of about 1.075 grams per cubic centimeter (g/cc).
Original reservoir pressure at 3,100 feet ranges from 1,000 to 1,100
pounds per square inch (psi).
Table A2-1 lists information from Ohio Class-1 injection wells,
from which a number of observations can be made. Those sites that
list the Mt. Simon as the injection interval (all in western Ohio) have
higher porosities and permeabilities, thicker injection zones, higher
injection rates, and larger cumulative volumes injected. In general,
the Mt. Simon Class-1 sites have also been in operation longer
and, with the exception of the Aristech site, are still in operation.
The Class-1 facilities in northeastern Ohio that utilized the thinner
sandstones and carbonates of the Conasauga Group (Reserve Environmental
Services and Tomen Agro) could not attain very high injection
rates. In fact, the Reserve Environmental Services site could
not inject enough material to sustain its operation. This information
should prove useful when examining prospective sites/reservoirs for
potential CO 2 injection.
In Kentucky, there has been only one attempt to inject waste into
the Mt. Simon, near Louisville, west of the MRCSP study area.
Upon drilling, the sandstones were found to be tight, and a porous
zone within the shallower Copper Ridge Dolomite was ultimately
chosen as the injection horizon.
The overall reservoir character of the basal sandstones (Rome
trough) is not known, but suspected to be relatively poor because
the sandstones are shaley. However, proprietary seismic data in
the region indicates areas where thick, well-developed, sandstones
might be present. Future drilling would be required to confirm the
presence and injection properties of the sandstones. Further characterization
of injection properties of all the basal sandstones and
other prospective reservoir units will be a goal of Phase II efforts
within the MRCSP study area.
The overlying shales, siltstones, and carbonates of the Eau Claire
through Copper Ridge interval provide an excellent vertical seal
system for the Mt. Simon Sandstone in the western part of the
MRCSP study area. Measured vertical permeabilities of the shale
and siltstone intervals typically range from unmeasurable (< .001
md) to 0.01 md. Some sandy intervals within the seal sequence
may have significantly more permeability and porosity, providing
good zones to absorb and trap any CO 2 that might make it through
the lower permeability layers. As depth to the Mt. Simon increases
in the Michigan basin, additional seal units are stacked above this
interval. Should injection intervals be found within the unnamed
Conasauga sandstones, Potsdam Sandstone, or Rome trough sandstones,
a very thick succession of overlying carbonates of the Knox