Kansas Geological Survey, Open-file Report 2009-5
Preliminary High-Resolution Stratigraphic Analysis of the Caney and Woodford Shales in a Continuous Shallow Corehole (KGS-OGS Current #1) from the Lawrence Uplift in Pontotoc County, Oklahoma
W. Lynn Watney, Darwin R. Boardman, Neil H. Suneson, Jim Puckette, Thomas L. Thompson, John H. Doveton, Evan K. Franseen, John R. Victorine, Kenneth Stalder, and Robert Walton
KGS Open File Report 2009-5
Statement of Problem
- Need for a basic scientific framework to augment resource appraisal of gas shales in order to place deposits in a global temporal and process framework.
- Provide means to leverage successes to other shales in other basins.
- No global high-resolution stratigraphic or biostratigraphic model exists for the Upper Devonian to Lower Pennsylvanian succession.
- Complex mm- to dm- scale beds and bed sets of basinal, shale-dominated lithofacies have been variably related to global and regional processes, but their correlation is ill-defined.
- Strategic, continuous reference sections that are resolved stratigraphically, biostratigraphically, and geochemically in three dimensions are needed in Midcontinent basins to establish the systematics of temporal variations in lithofacies from basin to shelf. This is critical to establishing a sequence stratigraphic framework.
- Regional reference section must be tied to global stratotypes through chronostratigraphic methods to develop a robust, process-based understanding of strata and to allow results to be widely applicable to equivalent strata in other basins.
- The paleogeography for the Upper Devonian-Lower Pennsylvanian that defines the shelf-to-basin transitions surrounding the Arkoma Basin is highly generalized. Vastly improved resolution as needed to better assess resources and reconstruct the foreland basin framework and basement structures that have actively influenced sedimentation and paleo-oceanographic conditions.
- Shelf-to-basin detrital and biogenic silica distribution is poorly understood; refined spatial and temporal distribution is needed for these deposits that include the "Chat" or tripolite (microporous spiculitic-skeletal packstone-grainstone) deposits that accumulated along the shelf margin, and the gradation from non-siliceous to siliceous Woodford and the Arkansas Novaculite.
- In general, rock properties need to be placed in this spatial-temporal framework in order to optimize exploitation of associated remaining unconventional and conventional oil and gas resources.
- The role of global, regional, and local controls on the distribution of organic-rich, phosphatic, and siliceous stratal successions needs to be determined before more refined global predictive models on resource distribution can be realized.
- From a global perspective, boundary stratotypes are being sought for key intervals that are being reexamined including Devonian-Carboniferous, Visean-Serpukhovian (Sand Branch, lower Fayetteville and upper Barnett shales), Bashkirian-Moscovian (base of Atoka in Wapanucka).
- In general, the biostratigraphy in the type areas of the U.S. is based on shallow-water small forams and conodonts (e.g. Chesterian) and these species are different from those found in Russia and cannot be easily correlated.
- Systematic conodont biostratigraphy of the major gas-producing shales including Fayetteville, Caney, and Barnett, is needed in conjunction with isotope chronology, chemostratigraphy, and sequence stratigraphy to establish global reference sections.
- Late Devonian- to Chesterian-age basinal shale-rich strata are increasingly important domestic unconventional oil and gas reservoirs,
- Extending resource development in the greater Anadarko-Arkoma-Ft. Worth foreland basins from core-producing areas requires an understanding of spatial variations of critical shale properties.
- A classic interaction of major global and regional processes appears to be responsible for these new hydrocarbon resources including recurring basin anoxia, long- and short-term changes in eustasy, climate change, differential sedimentation and basin subsidence, spatial-temporal changes in fault system dynamics, and strong diagenetic variations.
- Stratigraphic analysis, namely establishing temporally distinct depositional sequences, is critical to mapping the distribution of favorable reservoir rocks. The preliminary analysis thereof for the KGS-OGS Current #1 corehole was presented.
- Depositional sequence analysis once conducted on a regional level as proposed in an extended coring program from shelf-to-basin should provide the means to establish a high-resolution paleogeography.
- Sequence stratigraphic interpretations and paleogeographic reconstructions substantiated with biostratigraphic, paleoecologic, geochemical, and chronostratigraphic information from strategic coring sites integrated with conventional analytical data about the resource (e.g.., Rock Eval, gas desorption, rock properties) should help establish additional oil and gas resources.
- The extent of these unconventional oil and gas resources onto the surrounding shelf margins during episodes involving expanding anoxia and upwelling and increased organic productivity has yet to be delineated and is an outcome sought in this ongoing investigation.
- Integration with global processes active in creating these oil and gas resources should aid in extending these results to other basins worldwide.
- This approach to studying shale resources parallels those of modern characterization of conventional reservoirs and, in fact, will aid in resolving long-standing correlations both regional and global.
The complete text of this report is available as an Adobe Acrobat PDF file.
Kansas Geological Survey, Energy Research
Updated May 21, 2009
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