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Park, Anthony J.1, John B. Comer2, Micah L. Foust2, John A. Rupp2, Dong-Hoon Sheen1, Jejung Lee1, Kagan Tuncay1, Peter J. Ortoleva1 
(1) Laboratory for Computational Geodynamics, Indiana University, Bloomington, IN 
(2) Indiana Geological Survey, Bloomington, IN

ABSTRACT: Overpressuring and Fracturing of New Albany Shale in the Illinois Basin: Insights from Automated Information Theory and Basin Simulation

Gas has been produced commercially from New Albany Shale (Devonian-Mississippian) in the Illinois Basin since 1863. Current exploration is concentrated in southern Indiana and western Kentucky where fractured shale comprises the gas reservoirs. 
In this DOE-funded project, sediment compaction, seal development, overpressuring, fracturing, and gas generation were studied to assess their interdependency and relative importance in the formation of gas reservoirs. An information-theory program (TROPY) was created to calibrate poorly constrained geological data, and a comprehensive basin-scale simulator (CIRFB) was used to simulate the dynamic evolution of sediments in the region using the TROPY-calibrated parameters and petrophysical data. TROPY searches for the optimal state of various geologic, chemical, and physical parameters based on limited available well-log and seismic data. CIRFB accounts for visco-elasto-plastic rheology, fracturing, gas/oil generation, multiphase fluid flow, and heat and mass transfer to evolve reservoir properties. Automated error-minimization using both programs allows more realistic basin simulations as available data are made use of in the model. 
Results from the simulations for Harrison County, Indiana, show that lower units in the New Albany Shale and upper portions of the underlying carbonate rocks are preferred zones for fracturing due to the timing of seal development and overpressuring in the shale. Simulations also predict that rapid deep burial and rebound control the timing and rate of seal development and the relatively low level of organic maturation in the shale. The labile organic matter that remained was available for bacterial methanogenesis upon fresh water recharge that culminated during regional Pleistocene glaciation.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.