Summary

A time-based approach to source rocks and associated fine-grained units employing a framework of large-scale stratigraphic sequences provides a high-level scoping tool to pinpoint the temporal position of potential organic-rich, core mudrock facies throughout Phanerozoic time. Utilizing a composite global eustacy curve taken from published sources, a total of 45 second-order flooding intervals are noted, 16 of which correspond to times of larger, more extensive, extrabasinal transgressions. Each of the 45 flooding events is associated with development of an organic-rich, core mudrock facies that has potential to serve as a local to interregional source kitchen for unconventional mudrock plays. Individual second-order core mudrock units may vary widely in terms of generative potential owing to differences in global to local geologic conditions at time of depositional and to differing post-depositional histories. Individual 2nd-order intervals must therefore be carefully assessed using a variety of geologic, geochemical, and petrophysical methods in order to define present-day resource potential.

Introduction

The domestic oil and gas industry has undergone a true paradigm change over the past five years. The industry-wide shift to exploring for and producing unconventional plays (e.g., shale-gas, liquid-rich mudrocks) constitutes the latest phase of a ?shale revolution? that has roots back to Mitchell Energy's work on the Barnett Shale of the Fort Worth Basin in the early 1980's (Lapierre, 2013). The search for new unconventional plays includes the integration of geochemical, petrophysical data sets together with traditional basin history analysis methods, with the goal of identifying organic-rich, fine-grained successions that can be effectively stimulated and economically produced from either vertical or horizontal wellbores.

The foundation of all economic fine-grained, mudrock-dominated systems or unconventional plays is the presence of one or more organic-rich source intervals. As industry moves forward and develops a handful of established unconventional plays (Bakken, Marcellus, Eagle Ford, etc.), the search for new reserves will undoubtedly lead to the identification and testing of less areally-extensive, more subtle (in terms of thickness and/or organic content) source rock intervals. Any high-level screening method to locate possible source rock intervals within a given basin is therefore a useful to the overall exploration process.

URTeC 1563462

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