MRCSP Phase I Geologic Characterization Report - Midwest ...

APPENDIX A: UPPER CAMBRIAN ROSE RUN SANDSTONE
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flat to sabkha conditions. The carbonate bank represented by these
formations dipped seaward toward southeastern Virginia (southeast
of the MRCSP study area) where these units are dominated by peritidal
carbonates (Haynes, 1991).
Eau Claire/Conosauga/Elbrook/Warrior Formations—Marine conditions
continued in the units capping the trough fill. The marine
shales of the Eau Claire Formation in the western part of the MRCSP
study area represent the continuation of the Mt. Simon transgression
(Driese and others, 1981). It bears repeating that this transgressive
sequence is different from the transgressive sequence that includes
the basal sands in the Rome trough and the basal sands east of the
Rome trough. The Eau Claire and lateral units represent deposition
following filling of the Rome trough. Across the MRCSP study area,
there is a west to east transition in this sub-interval from shallow
marine siliciclastics of the Eau Claire Formation; to mixed carbonates
and clastics deposited in intra-shelf settings in the Conasauga;
to peritidal carbonates of the Elbrook and Pleasant Hill Formations
(Read, 1989a, 1989b). The latter carbonates are part of the persistent
carbonate bank that existed on the eastern, passive margin of the
craton during Cambrian and Early Ordovician time.
Upper Munising/Trempealeau/Potosi/Davis/Copper Ridge/Gatesburg/Conococheague
Formations—During this sub-interval, a
regression caused progradation of peritidal carbonates across the
entire MRCSP study area (Read, 1989a and 1989b). This regression
may have been related to the cessation of extensional tectonics on
the passive margin, and marks the Sauk II/Sauk III boundary (Glumac
and Walker, 2000). The Copper Ridge and its equivalents were
deposited in a variety of peritidal environments. To the east, the
Conococheague was deposited as platform carbonates transitional
to deeper basinal facies to the south and east (Demicco, 1985). Shallowing-upward
cycles within the Conococheague record repeated
facies successions from storm to subtidal algal reef to subtidal shoal
to intertidal flat and, ultimately, to sabkha (Demicco, 1983). Sandstones
in the lower part of the Concococheague and lateral equivalents
may be related to detrital influx following the Sauk II/Sauk
III sea-level fall (Marchefka and Glumac, 2002). More widespread
sandstones in Michigan and parts of Indiana (Galesville and Ironton)
were deposited as shallow marine shelf sands, which preceded
the accumulation of peritidal carbonates in the Trempealeau Formation
(Catacosinos and Daniels, 1991).
SUITABILITY AS A CO 2
INJECTION TARGET OR SEAL UNIT
Given the variability in the geology across the region, it is not
surprising that the mineralogy of lithologies within the Basal Sandstone
to top of Copper Ridge Interval in the MRCSP study area is
quite variable. Much of the sandstone in the interval is composed of
reworked, multicycle quartz similar to the underlying mineralogy of
the basal sandstone. There are also significant amounts of detrital
and diagenetic feldspars, as well as a variety of detrital and authigenic
clay minerals present in some units. Additionally, there are
numerous portions of the section that contain significant amounts
of glauconite. The varied mineralogy complicates analyses of the
interval because geophysical log responses are, in many cases, not
representative of the actual porosity of the rocks. Microporosity
in shales, and the complex mixing of carbonate and siliciclastic
lithologies, complicate geophysical log responses in some areas and
in some parts of the interval. These minerals make the assessment
of porosity and, especially, permeability problematic. Core analyses
from this interval on the Ohio platform indicate low permeability in
the interbedded clastics and carbonates -, suggesting good to excellent
reservoir seal/confining characteristics.
Although the overall interval is mapped as a seal, there are units
within the interval (especially in the east) that are possibilities for
sequestration. These units themselves are confined by thick sections
of shales or carbonates that would act as a seal. In northeastern
Ohio, where limited porosity and permeability have been encountered,
injection wells have been completed in the sandstones of the
Conasauga Group. However, total cumulative injection volumes for
these units are low when compared to Mt. Simon injection sites. In
addition, multiple stratigraphic units had to be utilized at these sites
to obtain the necessary injectivity.
Geophysical log responses of a few well-developed dolomitic
sandstone units within the Conasauga Group of eastern Ohio suggest
potentially good to excellent injection reservoirs. Site-specific
evaluation, coring, and core analysis would be necessary before using
these sandstones as an injection target. These are possible targets
for Phase II studies.
Another potential sequestration target would be sandstones in
the Rome Formation. These arkosic, marine sandstones may be as
much as 500 feet thick (averaging approximately 250 feet). Limited
oil and gas well drilling has encountered permeabilities as high as
177 md, with an average of 62 md, and with mean porosities of 12
percent (Harris and others, 2004). Because these are not regionally
extensive units, they were not a focus of Phase I research, but they
could be examined as part of the continuing geologic characterization
in Phase II. Opportunities for structural closure exist within the
fault-bound Rome trough, although reservoir heterogeneity may
be common (Harris and Baranoski, 1996). The overlying shales
of the Conasauga Group would form the seal on these potential
reservoirs.
Thick zones of vugular porosity have also been encountered in
a number of scattered wells within the Copper Ridge Dolomite.
Vuggy dolostones were used at the DuPont WAD Fee well in Louisville,
Kentucky (just west of the MRCSP study area) for the disposal
of industrial waste fluids, after a well in the Mt. Simon Sandstone
encountered “tight” sandstones at that horizon. The interval of
vuggy dolostone is sealed above by dense dolostones of the Copper
Ridge. Coring of the potential reservoir and seal units within the
Copper Ridge would be required to further evaluate their sequestration
potential in this and other parts of the MRCSP study area.
Where this unit is deep enough to keep the CO 2 in miscible form,
analysis appears warranted for use as an injection target, especially
as a backup or secondary target for deeper Mt. Simon wells. These
are also potential targets for Phase II studies.
4. UPPER CAMBRIAN ROSE RUN SANDSTONE
In Ohio and eastern Kentucky, the Cambrian-Ordovician Knox interval
is subdivided, in ascending stratigraphic order, into the Copper
Ridge Dolomite, Rose Run sandstone, and Beekmantown Dolomite.
The Cambrian Rose Run sandstone is the only laterally persistent sandstone
within the Knox Dolomite. This sandstone interval can be correlated
in the subsurface from eastern Ohio, where it subcrops beneath
the Knox unconformity (Figure A4-1), to eastern Kentucky, into western
West Virginia (upper sandstone member of the Knox), Pennsylvania
(Upper Sandy member of the Gatesburg Formation) (Figure 5), and
extends into New York (partial equivalent of the Theresa Formation).