MRCSP Phase I Geologic Characterization Report - Midwest ...

116 CHARACTERIZATION OF GEOLOGIC SEQUESTRATION OPPORTUNITIES IN THE MRCSP REGION
DEPOSITIONAL ENVIRONMENTS/
PALEOGEOGRAPHY/TECTONISM
The Sylvania Sandstone represents the initial transgressive phase
of an extensive Devonian-age carbonate sequence—the Detroit
River Group—that was deposited over the regionally extensive
Kaskaskia unconformity. The rounded and frosted quartz grains,
common in many parts of the Sylvania, are characteristic of sand deposited
in eolian environments or at least sand reworked from older
eolian rocks. However, the presence of marine fossils and interbeds
of sandstone within adjacent carbonates suggest a predominantly,
if not entirely, shallow marine environment. Hatfield and others
(1968) concluded the Sylvania was most likely a beach deposit that
formed during a eustatic transgression.
SUITABILITY AS A CO 2
INJECTION TARGET OR SEAL UNIT
The sandstone-dominated facies of the Sylvania Sandstone, best
developed in central and southeastern lower Michigan, have been
used for Class 2 waste-disposal wells and is also a major source for
brine in industrial-mineral wells for the chemical industry in Midland
County (Fisher and others, 1988). Porosity and horizontal permeability
measurements from 24 sidewall-core samples from the Sylvania,
collected in a well in southeastern lower Michigan, ranged from 1
to 28 percent porosity with an average of 16.6 percent. Permeability
measurements ranged from 0 to 388 md with an average of nearly 100
md. These measurements are consistent with porosity and permeability
characteristics presented herein. The primary doubts concerning
the suitability of the Sylvania for CO 2 injection centers mostly on the
unknown variability of the lithofacies and their distribution throughout
the Michigan basin. Subsurface analysis of general lithofacies
patterns indicates the sandstone-dominated facies in southeastern and
central areas of the Michigan basin are replaced by mainly cherty
carbonate facies in other regions. The chert-dominated lithofacies is
likely to be porous, and also tripolitic, thereby significantly affecting
the injectivity potential of the unit. Thus, a more detailed analysis of
variations of the internal facies and rock properties of the Sylvania
warrant additional investigation in order to further understand the
CO 2 sequestration potential of the unit. In the central portion of the
Michigan basin, the geologically older and potential sequestration
reservoirs of the Mt. Simon and St. Peter Sandstones are very deep
(thus expensive to drill). This great depth may not be advantageous
for the occurrence of zones of high porosity and permeability for
injection of CO 2 within these older units. In contrast, the Sylvania
in much of this same central basin area is fairly thick and occurs at
a moderate depth that may be more favorable for development of
porosity and permeability ample for CO 2 sequestration.
The Amherstburg Formation, a complex succession of evaporites
and carbonates in the Detroit River Group, everywhere overlies the
Sylvania Sandstone. Gardner (1974) suggests the continuity and
integrity of Amherstburg Formation is variable; thus, its ability to
function as a seal for the Sylvania in the Michigan basin is undetermined.
However, overlying the Amherstburg are evaporates of
the Lucas Formation, the Dundee Limestone, the Traverse Group
(shale and limestone), and the Antrim Shale. This combined package
should provide an adequate seal to insure integrity to Sylvania
Sandstone injection reservoirs.
13. LOWER/MIDDLE DEVONIAN NEEDMORE SHALE
The Needmore Shale is present throughout western Maryland,
south-central Pennsylvania, and eastern West Virginia; the upper
part of the Needmore is laterally equivalent to the Onondaga Limestone
in northern Pennsylvania and New York, and to the Huntersville
Chert in western Pennsylvania and West Virginia (Figure 5).
The Needmore Shale is underlain by the Early Devonian Oriskany
Sandstone and overlain by the Middle Devonian Onondaga Limestone,
Huntersville Chert, or Tioga Bentonite, depending upon the
location within the Appalachian basin.
Conodont biostratigraphy indicates that the Needmore Shale is of
Early and earliest Middle Devonian age. Conodonts from the overlying
Tioga Ash Bed suggest that the top of the Needmore is within
the Polygnathus costatus costatus Zone of Middle Devonian age.
(Harris and others, 1994)
ORIGIN OF NAMES, TYPE SECTION, SIGNIFICANT
EARLIER STUDIES ON THIS INTERVAL
The Needmore Shale is named for exposures in southern Fulton
County, Pennsylvania (Willard and Cleaves, 1939). The name was
extended into Maryland, Virginia, and West Virginia by Woodward
(1943). This unit was later assigned as a member of the Romney
Shale (Lesure, 1957) and the Onondaga Formation, but currently is
formational in status.
NATURE OF LOWER AND UPPER CONTACTS
The contact between the Needmore Shale and the underlying
Oriskany Sandstone is sharp and unconformable, representing either
a transgressive surface or a transgressive surface/unconformity
converged (G.R. Baum, personal communication, 2005). The
Needmore Shale grades laterally into the Huntersville Chert and,
upsection, into dark gray, argillaceous limestones of the Onondaga
Limestone. In the absence of the Huntersville Chert and the Onondaga
Limestone facies, there is a 10- to 15-foot interval of coarse,
brown shale mixed with considerable volcanic ash termed the Tioga
Bentonite at the top of the Needmore Shale.
LITHOLOGY
The Needmore Shale is a dense, fissile, dark olive-gray to black,
calcareous shale with dark gray interbeds of thin-bedded and nodular,
fossiliferous, argillaceous limestone. Dark gray volcanic tuffs
and ash beds occur at the top of the formation (Glaser, 2004).
Over most of western Maryland, the upper half of the unit is thickly
laminated shale containing nodules and thin beds of limestone.
Similar shale without limestone makes up the lower portion of the
Needmore Shale, grading at the base to dark fissile non-calcareous
shale. In outcrop, the coarser shale and mudrock disintegrate rapidly
to pale-olive or tan chips or irregular clasts, whereas the black shale
weathers to thin grayish-white plates and papery flakes much like
the Marcellus Shale (Glaser, 2004).
DISCUSSION OF DEPTH AND THICKNESS RANGES
Based on well log picks and published reports for Maryland,
the thickness of the Needmore Shale ranges from 3 to 190 feet
(Edwards, 1970; Nutter and others, 1980). The unit thickens from
northwest to the southeast (Figure A13-1). Depth to the top of
the Needmore varies from a minimum of about 1,000 feet below