MRCSP Phase I Geologic Characterization Report - Midwest ...

12 CHARACTERIZATION OF GEOLOGIC SEQUESTRATION OPPORTUNITIES IN THE MRCSP REGION
Consequently, some states were able to compile basic mapping data
quickly, which allowed them extra time to researching additional
data types and sources. Others had to spend much of the project
gathering basic data from paper records and entering it into a computer
compatible format.
One of the benefits of this project was that conducting a regional
compilation allowed for the sharing and mapping of data seamlessly
across political boundaries. An added benefit was this process permitted,
perhaps a first for the region, the analyses of trends (many
being previously undetected) that occur through areas of variable
data for the benefit of the entire region. These results will be critical
for future carbon management in the region and will also be useful
to a wide range of nonsequestration applications.
The thickness and depth of nine potential sequestration target
units and five cap-rock intervals were mapped by the MRCSP
working group. In total, the MRCSP geologic assessment resulted
in 30 original depth and thickness maps, nine regional thematic
maps, and 14 derivative capacity maps in a state-of-the-art GIS
database. Moreover, the regional digital oil-and-gas-fields map
and database was a very significant accomplishment for the seven
state region. It is the first compilation at this scale in the region
and represents the first digital compilation of petroleum fields data
for Maryland, Michigan, Pennsylvania, and West Virginia. The
completion of this basic field-level data, along with the detailed
field polygons, within this regional GIS compilation will prove
very useful not only for CO 2 sequestration research and planning,
but also to the oil and gas industry, academia, and others in the
public and private sectors.
This project represents the first time these geologic units or intervals
have been mapped across this entire region. Also a first for this
project was the collection of the geothermal gradient and salinity
information in a centralized digital database. A number of the maps
produced represent the first time any type of map for that specific
interval have been constructed—such as the basal Cambrian sands.
Although several of the member states were part of MIDCARB
(DOE’s initial CO 2 sequestration partnership), the MRCSP project
represents the first time that the geologic CO 2 sequestration potential
has been evaluated for Maryland, Michigan, Pennsylvania, and
West Virginia. The cooperation of the member organizations in this
geologic investigation provides an excellent opportunity for understanding
and implementing future carbon management options
based on the best-available geologic knowledge of the region.
GEOLOGIC MAPPING PROCEDURES, DATA SOURCES AND METHODOLOGY
The central products of the MRCSP Phase I geologic tasks were
a series of regional-scale, digital spatial models and maps, with the
overall goal to create a GIS to support regional planning for carbon
sequestration. The GIS provides spatial data that can be used
to evaluate the potential for geologic sequestration of CO 2 at any
particular site within the MRCSP study area by digitally analyzing
which underlying geologic units might be suitable for further analyses
as a CO 2 reservoir and/or seal, their depths and overall thickness,
and to provide an estimate of sequestration capacities. Selected sites
that appear suitable must still be subjected to further, more detailed
studies and site-specific testing and analyses. Digital maps were
compiled for the depth and thickness of target and confining geologic
layers, the extent of major oil and gas fields, the locations of
industrial injection wells, as well as for other geochemical and petrophysical
data needed to calculate CO 2 sequestration capacity.
Most of the mapping effort focused on generating structure and
isopach maps for nine regional geologic sequestration targets and
five confining layers. The mapping also represents one of the first
attempts to create regional-scale geologic maps using quantitative
methods with rigorous error assessments. Geologic structure and
isopach maps were created by interpolating formation tops from oiland-gas-well
records that were compiled by the individual partnership
states. The MRCSP geologic database contains a total of 85,650
individual wells (Figure 7) and approximately 162,000 formation
tops. Control points (wells) available for mapping individual layers
ranged from less than 500 points for very deep layers (Lower
Cambrian rocks), to in excess of 23,000 points for shallower layers
such as the Lockport-Onondaga interval. Point data were converted
to isoline maps using a couple of different, commercially-available
software packages that utilize a range of interpolation methods/
algorithms. Unfortunately, these computer interpolations occasionally
resulted in the generation of surface trends that contradicted
known geologic surfaces. In these cases, isolines were manually edited.
Grids (rasters) were created for every layer to facilitate spatial
analyses, modeling, and cartographic display. The accuracy of the
maps was evaluated rigorously. Root Mean Square Errors (RMSE)
ranged from 20 to 500 feet for the structure grids and from 20 to 600
feet for isopach grids. Such error ranges reinforce the previous statements
that the maps of this project are of sufficient quality for regional
planning, but cannot be used in place of detailed site studies.
METHODOLOGY FOR STRUCTURE
AND ISOPACH MAPPING
Maps in this project were created to identify major regional sequestration
targets and confining layers. Our definition of mapping
units reflects these goals rather than traditional stratigraphic-use
customs. Hence, in many cases the mapped layers do not follow formal
lithologic units or sequence-stratigraphy definitions as currently
used by many workers. For some map layers, several lithologic units
that are considered diachronous were merged together. For example,
the Cambrian basal sandstones layer includes the Mt. Simon Sandstone,
the basal sandstones of the Rome Trough, the Potsdam Sandstone,
and unnamed sandstones of the Conasauga Group (Figure 8).
These units range from the Furongian (Upper) to the Lower Cambrian
in their occurrence, yet have little genetic relationship to one
another. However, the grouping of these units together is useful in
and of itself since all sandstones directly overlying the Precambrian
unconformity can now be found on one map, thus reducing the complexity
of using multiple maps for a like stratigraphic unit.
The mapping workflow for this project included six steps: (1) data
gathering, (2) data filtering to remove erroneous wells, (3) interpolation
and contouring of gridded data, (4) manual editing of digital
contour maps, (5) peer review and adjustments, and (6) creation of
grids from final contour maps. The various MRCSP geologic teams
divided the mapping responsibilities amongst themselves based on
individual areas of expertise. Each organization was responsible for
the aforementioned steps 1 thru 5 for each selected interval and each
team was allowed the freedom to use the mapping software of their
choosing. After review, the final contour map files were sent to the
Ohio Division of Geological Survey, where final gridding was applied
for use in the CO 2 capacity calculations.
Original Data
The primary dataset consisted of well data provided by each