CO₂ Sequestration Opportunities in Kentucky

Contact: Carrie Pulliam

• The MIDCARB project, original project, completed
• National Carbon Database and GIS, on going
• Regional Sequestration Partnerships (now in Phase II)
• Midwest Geologic Sequestration Consortium, current, Illinois Basin
• Midwest Regional Carbon Sequestration Partnership, current, central and northern Appalachian Basin
• Southeast Regional Carbon Sequestration Partnership, current, Black Warrior Basin and Gulf Coastal Plain states
• Measurement, Mitigation, and Verification: CO₂ and CH₄ flux in soils and the near subsurface, new

The world runs on fossil fuels and is likely to do so for a significant part of the 21^st century. In the United States, coal is the primary fuel for electric power generation and petroleum is the transportation fuel of choice. Natural gas is an increasingly important fuel for the manufacturing industry, electrical utilities, and transportation. (See the Energy Information Administration of the U.S. Department of Energy for resource and usage information.) One of the by-products of burning fossil fuels is the release of CO₂ (carbon dioxide), a greenhouse gas, into the atmosphere. The increase in atmospheric CO₂ is linked by most scientists to global warming. Three strategies are available for managing the amount of CO₂ released to the atmosphere:

• Increased use and development of low-carbon or carbon-free energy sources
• Increased energy efficiency and energy conservation efforts for combustion technologies that rely on fossil fuels
• Removal and long-term storage of CO₂ from exhaust gas streams. This long-term storage of CO₂ is referred to as "carbon sequestration."

It will be several decades before carbon-free fuels become widely available. Conservation measures will help, but increased demand for energy, especially in developing countries, will diminish their beneficial effects. While alternate fuel and conservation strategies are being developed and implemented, long-term storage options will be needed for successful carbon management.

The main goal of these projects is to build a knowledge base for use in evaluating the distribution, physical characteristics, and capacity of potential CO₂ storage sites.

In 2002, Kentucky's coal-fired power plants emitted 87 million metric tons of CO₂ (seventh overall in the United States, EIA). Kentucky is a net exporter of power. FutureGen is an initiative to build an integrated zero-emissions power plant that takes advantage of carbon sequestration and produces hydrogen for fuel cells. Preliminary regional site assessments have been made, see FutureGen in Kentucky, a Powerpoint presentation.

In Kentucky, CO₂ sequestration potential exists in three recognized types of geologic sinks:

• Oil and gas fields
• Coal beds
• Saline aquifers

Additional potential unconventional sequestration sites warranting assessment are:

• Devonian black shales of the Appalachian and Illinois Basins
• Deep reservoirs
  • East Continent Rift Basin
  • Rough Creek Graben
  • Rome Trough

Existing oil and gas fields represent one of Kentucky's primary opportunities for sequestration. There are an estimated 1.7 billion barrels of original mobile oil-in-place (OOIP) in 46 of the largest reservoirs in Kentucky (see TORIS). Of this amount, at least 170 million to 250 million barrels of oil remains for primary and secondary recovery. A successful, immiscible CO₂ flood in eastern Kentucky increased oil production in the field by 23 percent. An estimated 50 percent of the CO₂ used in that flood remained sequestered in the formation. As an economic benefit, CO₂ flooding could be expected to boost statewide annual oil production by 10 to 15 percent to about 3.45 million barrels. Enhanced recovery projects designed to maximize CO₂ sequestration could use approximately 20 percent of the CO₂ emitted in the state.

The organic-rich fractured Devonian black shales and Pennsylvanian coal beds of Kentucky are additional possible sites for carbon sequestration. The state produced 94.2 billion cubic feet (bcf) of natural gas in 2004; most is from the Devonian shales in the Appalachian Basin of eastern Kentucky. A project to evaluate the sequestration potential of the Devonin Shale in Kentucky has been completed and the final report is being prepared. In the state's coal basins, there are an estimated 283 bcf of coalbed methane gas-in-place. For the shale and coals, using a recovery factor for natural gas of 17 percent, 5 tcf remain savailable for primary production and approximately 50 tcf available for enhanced recovery. CO₂ sequestration in these reservoirs could result in an additional 30 bcf in annual production for natural gas in Kentucky and sequestration of 60 bcf CO₂ annually. At this rate, in 10 years, as much as 31.8 million metric tons of CO₂ could be sequestered.

The sequestration of CO₂ in saline aquifers is also possible in many parts of Kentucky. Several deep saline aquifers are present in the Appalachian and Illinois Basins. The Cambrian Mt. Simon Sandstone has been used for deep-well disposal in Ohio, as has the Cambrian-Ordovician Knox Group in Kentucky. Other formations, such as parts of the Middle Proterozoic Middle Run Formation, could be considered for sequestration in the vicinity of the Cincinnati Arch and the Illinois Basin of central and western Kentucky. Capacities for CO₂ sequestration in these formations are unknown.