Criteria for recognizing stratigraphic sequences are well established on continental margins but more challenging to apply in basinal settings. We report an investigation of the Upper Devonian Woodford Shale, Permian Basin, west Texas based on a set of four long cores, identifying sea level cycles and stratigraphic sequences in an organic-rich shale.
The Woodford Shale is dominated by organic-rich mudstone, sharply overlain by a bioturbated organic-poor mudstone that is consistent with a second-order eustatic sea level fall. Interbedded with the organic-rich mudstone are carbonate beds, chert beds, and radiolarian laminae, all interpreted as sediment gravity-flow deposits. Bundles of interbedded mudstone and carbonate beds alternate with intervals of organic-rich mudstone and thin radiolaria-rich laminae, defining a 5–10 m (16–33 ft)-thick third-order cyclicity. The former are interpreted to represent highstand systems tracts, whereas the latter are interpreted as representing falling stage, lowstand, and transgressive systems tracts. Carbonate beds predominate in the lower Woodford section, associated with highstand shedding at a second-order scale; chert beds predominate in the upper Woodford section, responding to the second-order lowstand.
Additional variability is introduced by geographic position. Wells nearest the western margin of the basin have the greatest concentration of carbonate beds caused by proximity to a carbonate platform. A well near the southern margin has the greatest concentration of chert beds, resulting from shedding of biogenic silica from a southern source. A well in the basin center has little chert and carbonate; here, third-order sea level cycles were primarily reflected in the stratigraphic distribution of radiolarian-rich laminae.
Added on 31 December, 2013
EIA's Petroleum Supply Monthly report shows oil production in the lower 48 states has increased over the last three years.
Added on 01 July, 2013
Explorer Division Column DPA
During my term as DPA president this year our theme will be “Culture of Greatness.” This may sound arrogant, but I think it is important to recognize and promote the culture of professionalism and discovery that has provided cheap energy for mankind for more than 100 years.
Added on 01 July, 2014
America’s recent ascent to the high-level status of a hydrocarbon producer worthy of a significant presence on the world stage of leading producers stems from something new and a rebirth of something old.
Added on 01 May, 2014
Is that a UFO? Actually it is a UAV (unmanned aerial vehicle), which is an airborne drone that is proving to be useful both onshore and offshore.
Added on 01 November, 2013
A valuable study funded by the Texas Water Development Board sets aside the controversy and takes a closer look at hydraulic fracturing and water resources and consumption.
Added on 01 October, 2013
Wireless 'push-pull' shooting method reduces acquisition costs relative to traces per bin in recent Permian Basin survey.
Added on 01 September, 2013
New dimensions: Geoscientists study how 3-D views of Eagle Ford outcrops are a great tool.
Added on 01 July, 2013
Bottoms up! The successful Barnett play is getting a second look, thanks to a new study that took a bottomsup approach to determines areas with the best potential.
Added on 01 April, 2013
A regional database of more than 3,500 producing Eagle Ford wells is helping to highlight production trends and optimal engineering parameters.
Added on 01 March, 2013