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This study explores the feasibility of carbon dioxide (CO2) sequestration in the gas shales of Kentucky. The organic-rich Mississippian-Devonian shales have the potential to store significant amounts of CO2. The research includes assessments of CO2 sorption capacity, methane displacement potential, and reservoir simulation. The study also emphasizes the importance of monitoring CO2 levels in surface soils and produced gas.
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CO2 Sequestration in Gas Shales of Kentucky U.S. DOE/NETL DE-FC26-02NT41442 Brandon C. Nuttall, James A. Drahovzal, Cortland F. Eble, R. Marc Bustin AAPG Calgary June 19-22, 2005
Why Black Shales? • Distribution and potential storage volume • Known producer • Gas adsorbed on kerogen and clay • Analogous to CBM?
Basic Research: Feasibility • CO2 sorption capacity • CH4 displacement potential
Devonian Shale in Kentucky Estimated gas in place: 63 to 112 tcf Present in subsurface >=1000’ deep and >=100’ thick Producing area
Big Sandy Reservoir Info • Completion interval >500’ • Average porosity 4.3% • Max. porosity 11% • Temperature 84oF • Average pressure 400 psi • Permeability <0.1 md Atlas of Major Appalachian Gas Plays, 1996
Solid Liquid Gas Typical Reservoir Conditionsfor CO2 Injection Critical Point Melting Line Pressure (psia) Saturation Line Temp (ºF)
Surface 1,000’ Pennsylvanian 2,000’ 3,000’ Mississippian 4,000’ Devonian Geologic Column Coal measures, mixed sand, shale, and coal. “Salt” sands 3,800’ +/- of mixed sand, shale, and carbonate provide adequate reservoir seal. Pennington: Sand and shale Big Lime: Carbonate Borden: Sand and shale Ohio: Carbonaceous black shale Composite thickness data from Knott and Leslie County wells and Dillman and Ettensohn (1980)
3-component system • Quartz • Clay • Organic matter } Density GR Clastic ShaleOverview Borden Mississippian Sunbury Berea Cleveland • 3-component system • Quartz • Clay • Organic matter Three Lick Bed Upper Huron Middle Huron Ohio Shale Devonian Lower Huron Olentangy
Cross section LAS file Adsorption Both Study Area
Average Organic Content Total Organic Carbon
Mean Random Reflectance Frequency Upper oil window and wet gas/condensates R0 random x 1.066 ~ R0 max
Standard cubic feet per ton CO2 CH4 Devonian Shale Adsorption Isotherms
Average CH4: 8.1 scf/ton Average CO2: 42.9 scf/ton Adsorption at 400 PSIA Frequency Adsorbed gas (standard cubic feet per ton of shale) CO2 = 5.3 x CH4
CO2 scf/ton = 7.9 x TOC + 20.7 r2 = 0.80 CO2 Adsorption at 400 PSIA
Sidewall cores for adsorption and CH4 displacement Borden Sunbury Berea 1 Cleveland 2 Three Lick 1 Upper Huron 1 Middle Huron 4 Lower Huron 1 Olentangy
Gas Saturation Adsorbed Gas (scf) Kerogen Bound Water Cum. Gas (bcf) Total Phi Total Gas (scf) QFM TOC ECS Shale Analysis Clays
Crossplot Lower density & Higher GR = More organic RhoBmax gray shale = 2.82 g/cc (g/cc)
Calculate TOC from RhoB Schmoker, 1993, USGS Bull 1909
Shading based on density (RhoB) <2.4 >2.8 More carbonaceous More clastic Cross Section W E 72 miles 1,600 feet
Tons/sq km >3 MM <1 MM 27.6 Billion Tons CO2 Estimated 40 scf/ton thickness weighted average
Future • Map TOC from density logs • New estimate of CO2 capacity • Demonstration project • CO2 monitoring • Surface soils • Produced gas • Reservoir simulation
Conclusion Preliminary analyses indicate the organic-rich Mississippian–Devonian shales of Kentucky have the potential to sequester large volumes of CO2. www.uky.edu/kgs