Print this pageAn Integrated Geological and Petrophysical Study of a Shale Gas Play: Woodford
Shale, Permian Basin, West Texas
Nicholas B. Harris1, Nikki T. Hemmesch1, Cheryl A. Mnich1,
Khodir Aoudia2, and Jennifer Miskimins2
1Department of Geology and Geological Engineering, Colorado School of Mines,
1516 Illinois St., Golden, Colorado 80401
2Department of Petroleum Engineering, Colorado School of Mines,
1613 Illinois St., Golden, Colorado 80401
ABSTRACT
An integrated stratigraphic, sedimentological, geochemical and petrophysical analysis of a long core in the Upper Devonian Woodford Shale from West Texas demonstrates variations in shale lithofacies, mineralogy and rock composition at multiple scales. Cyclic deposition is evident, marked by deposition of a massive carbonate bed, overlain by thick intervals of laminated black mudstone and then a sequence of interbedded lithofacies, including black mudstone, laminated carbonate and siltstone. These cycles are interpreted as third or fourth order stratigraphic sequences.
At the formation scale, the organic geochemical character varies systematically, with maximum values of 5 to 10% total organic carbon (TOC) in the Middle Woodford. High TOC values in the Middle Woodford are mirrored by high Mo/TOC and high TOC/P, suggesting that organic carbon deposition was linked to both redox conditions and organic productivity and that the latter two were linked through a positive feedback relationship.
The proportion of clay decreases and the proportion of biogenic silica increases systematically upward. This is interpreted as a function of a second order fall in sea level, with the delivery of continent-derived dissolved silica increasing upward as the basin became more isolated from the global ocean. The proportion of biogenic silica appears to significantly influence rock properties, with lower values of Poisson’s ratio in the Upper Woodford. This has major implications for well completion and stimulation design.
Harris, N. B., N. T. Hemmesch, C. A. Mnich, K. Aoudia, and J. Miskimins, 2009, An integrated geological and petrophysical study of a shale gas play: Woodford Shale, Permian Basin, West Texas: Gulf Coast Association of Geological Societies Transactions, v. 59, p. 337-346.
TemplateEndEditableAAPG Search and Discover Article #90093 © 2009 GCAGS 59th Annual Meeting, Shreveport, Louisiana