A two-year research study partnership between the Illinois State
Geological Survey (ISGS), natural gas storage companies and the
Department of Energy's Federal Energy Technology Center will develop
3-dimensional computer models for natural gas storage wells in the
Mt. Simon Gas Storage Fields in the Illinois Basin.
Underground, water-filled sand/sandstone aquifers in the Mt.
Simon area in Northern Illinois are used extensively to store
natural gas for peak seasonal usage in the Midwest. In Illinois
alone, the Mt. Simon formations hold 60% of the total gas storage
inventory, an important supply for peak winter deliveries for
northern Illinois cities, particularly Chicago.
Illinois is ranked fourth in the nation in natural gas storage
with between 1.2 and 1.6, (tcf) trillion cubic feet of gas in
storage. It has 600 billion cubic feet (bcf) of working gas. That is
the gas stored in reservoirs for use in the winter months. The
remainder is cushion gas, which stays in the reservoir year round.
The physical structure of the Mt. Simon reservoirs, however, is
geologically complex, making it difficult to predict their
performance as natural gas suppliers.
By developing 3-dimensional computer models of the reservoirs
using geological and geophysical data collected from 24 storage
reservoirs, the DOE project will help gas storage companies raise
the amount of working gas that can be produced economically from the
gas storage fields.
This will help ensure that customers have uninterrupted and
affordable gas supplies especially during the winter months.
The Energy Department, through its Office of Fossil Energy, will
provide a total of $180,000 ($100,000 this fiscal year) to the
University of Illinois for use by the Illinois State Geological
The 3-D models will be based on full characterizations of 24
storage reservoirs. When the operators of gas storage wells improve
their understanding of the wells' geological and petrophysical
reservoir characteristics, reservoir performance and management are
improved. The proposed work is consistent with the objectives of the
U.S. Department of Energy to develop technologies for more reliable,
safe, cost-effective and efficient gas storage, which will help
ensure an adequate, uninterrupted gas supply for residential,
commercial, and industrial end users.
The geological models can be used as the fundamental framework
for subsequent fluid-flow simulation studies. Although production
histories have been gathered over the years, simulations to increase
deliverablilty or storage capacity strategies require fundamental
knowledge of the reservoir geology and geometry.
This study will define and link the sedimentary facies (referring
to rock units as rock type, mode of origin, composition, fossil
content, or environment of deposition) and their geometry,
mineralogy, and pore characteristics to fluid-flow potential.
Technically, this geologic reservoir characterization study will
provide the following regional and field specific products:
Core descriptions of the physical
wells and interpretations of the rock-type (facies)
Geologic and isopach (which detail
the thickness of the sand) maps and cross sections showing
facies and porosity distribution
Mineral composition and character of
sediments and diagenetic (the process of turning sediment into
rock) cements that comprise the reservoir and its internal,
natural clay compartment seals
Relations of the well porosity to
the well characteristics database (well log)
Geologic structure maps for northern
Illinois and specific fields
3-D models of facies and porosity
Salinity map of Mt. Simon formation
in Northern Illinois.
All data integration, mapping, and modeling will be performed
with Landmark software, utilizing digital wireline log data, lab
measurements of porosity and permeability, core descriptions, and
facies interpretations. Wireline logs are databases of information
gathered by a series of instruments, lowered on a cable, that
characterize well material structure and send this information to a
surface computer via a digitized wireline. ISGS will supply
individual contributing companies with digitized wireline logs for
their wells if they desire. ISGS has been offered previously
recorded digital logs, core data, and much other support by the
The study will assist many companies that are investigating the
possibilities of expanding the capability or capacity of existing
storage facilities to take advantage of FERC Order 636. FERC 636 is
an effort to unbundle the pipeline services into individual parts,
pipeline transport, storage, production etc., which can be
separately contracted by the user. Before the Federal Energy
Regulatory Commission ruling, pipeline companies charged for all of
the handling from wellhead to the user and charged what was
essentially an uncompetitive fee for the service. Users can now
separately contract for the lowest gas, storage and transport