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Slatt, R. M., P. R. Philp, Y. Abousleiman, P. Singh, R. Perez, R. Portas, K. J. Marfurt, S. Madrid-Arroyo, N. O'Brien, E. V. Eslinger, and E. T. Baruch, 2012, Pore-to-regional-scale integrated characterization workflow for unconventional gas shales, in J. A. Breyer, ed., Shale reservoirs—Giant resources for the 21st century: AAPG Memoir 97, p. 127–150.

DOI:10.1306/13321461M97441

Copyright copy2012 by The American Association of Petroleum Geologists.

Pore-to-regional-scale Integrated Characterization Workflow for Unconventional Gas Shales

Roger M. Slatt,1 Paul R. Philp,2 Younane Abousleiman,3 Prerna Singh,4 Roderick Perez,5 Romina Portas,6 Kurt J. Marfurt,7 Steven Madrid-Arroyo,8 Neal O'Brien,9 Eric Eslinger,10 Elizabeth T. Baruch11

1ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.
2ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.
3ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.
4ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.; Present address: Chevron-Texaco, Inc., Houston, Texas, U.S.A.
5ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.
6ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.; Present address: ConocoPhillips, Inc., Houston, Texas, U.S.A.
7ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.
8ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, U.S.A.
9Department of Geology, State University of New York, Potsdam, New York, U.S.A.
10Eric Geoscience, Inc., and The College of St. Rose, Albany, New York, U.S.A.
11Australian School of Petroleum, University of Adelaide, South Australia, Astralia

ACKNOWLEDGMENTS

We thank Devon Energy Corp. for financial and data support for much of this research; Ted Champagne of Clarkson University, Potsdam, New York; Carol McRobbie of State University of New York-Potsdam for technical assistance with SEM and FE-SEM analyses; and Dennis Eberl, U.S. Geological Survey, for XRD and chemical analysis of shales. This research was conducted mostly by graduate students in the University of Oklahoma College of Earth and Energy Institute of Reservoir Characterization and PoroMechanics Institute.

ABSTRACT

Based on recent studies of Barnett and Woodford gas shales in Texas and Oklahoma, a systematic characterization workflow has been developed that incorporates lithostratigraphy and sequence stratigraphy, geochemistry, petrophysics, geomechanics, well log, and three-dimensional (3-D) seismic analysis. The workflow encompasses a variety of analytical techniques at a variety of geologic scales. It is designed as an aid in identifying the potentially best reservoir, source, and seal facies for targeted horizontal drilling. Not all of the techniques discussed in this chapter have yet been perfected, and cautionary notes are provided where appropriate.

Rock characterization includes (1) lithofacies identification from core based on fabric and mineralogic analyses (and chemical if possible); (2) scanning electron microscopy to identify nanofabric and microfabric, potential gas migration pathways, and porosity types/distribution; (3) determination of lithofacies stacking patterns; (4) geochemical analysis for source rock potential and for paleoenvironmental indicators; and (5) geomechanical properties for determining the fracture potential of lithofacies.

Well-log characterization includes (1) core-to-log calibration that is particularly critical with these finely laminated rocks; (2) calibration of lithofacies and lithofacies stacking patterns to well-log motifs (referred to as gamma-ray patterns or GRPs in this chapter); (3) identification and regional to local mapping of lithofacies and GRPs from uncored vertical wells; (4) relating lithofacies to petrophysical, geochemical, and geomechanical properties and mapping these properties.

Three-dimensional seismic characterization includes (1) structural and stratigraphic mapping using seismic attributes, (2) calibrating seismic characteristics to lithofacies and GRPs for seismic mapping purposes, and (3) determining and mapping petrophysical properties using seismic inversion modeling.

Integrating these techniques into a 3-D geocellular model allows for documenting and understanding the fine-scale stratigraphy of shales and provides an aid to improved horizontal well placement. Although the workflow presented in this chapter was developed using only two productive gas shales, we consider it to be more generically applicable.

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