--> Is the Tuscaloosa Marine Shale Self-Sourced? Preliminary Oil-Oil and Oil-Source Rock Correlation Studies in the Upper Cretaceous Tuscaloosa Group, Southern Mississippi, USA
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Is the Tuscaloosa Marine Shale Self-Sourced? Preliminary Previous HitOilNext Hit-Previous HitOilNext Hit and Previous HitOilNext Hit-Previous HitSourceNext Hit Previous HitRockNext Hit Previous HitCorrelationNext Hit Studies in the Upper Cretaceous Tuscaloosa Group, Southern Mississippi, USA

Paul Hackley1, Daniel Garza2, Brett Valentine1, Catherine Enomoto1, Celeste Lohr1, Javin Hatcherian1, Frank Dulong1 and Kristin Dennen1

1 U.S. Geological Survey, Reston, Virginia, United States
2 Sanchez Previous HitOilNext Hit & Gas Corporation, Houston, Texas, United States

April 5, 2017 Wednesday 10:10 A.M. AAPG Annual Convention and Exhibition, Houston, Texas

Abstract

The U.S. Geological Survey will assess undiscovered hydrocarbon resources contained in the Upper Cretaceous Tuscaloosa marine shale (TMS) of southern Mississippi and adjacent Louisiana. Operators produce light (38-45° API), sweet Previous HitoilNext Hit from a ‘high-resistivity’ (>5 ohm-m) zone (HRZ) at the base of the TMS. Our characterization of TMS samples indicates low organic carbon (avg. TOC ~0.75%) and dominance of gas-prone Type III kerogen, potentially inconsistent with a self-sourced model (e.g., Lu et al. 2015, AAPG Bulletin 99, 333-357) for TMS-produced oils. Our work also includes characterization of thin (<1 ft), organic-rich (3-9 wt.% TOC), thermally mature (>0.6% Ro) shales in the underlying lower Tuscaloosa (LT), which do contain an Previous HitoilNext Hit-prone mixed Type II/III kerogen. To test if these thin LT shales could generate oils which are trapped at the base of the clay-rich (>50% total clays) TMS HRZ, we are evaluating Previous HitoilNext Hit-Previous HitoilNext Hit and Previous HitoilNext Hit-Previous HitsourceNext Hit Previous HitrockNext Hit correlations throughout the Tuscaloosa Group (TG, including LT; TMS; and upper Tuscaloosa, UT). Preliminary observations from a limited data set show close correspondence in δ13C isotope composition between all analyzed TG oils (n=39). SARA proportions, Pr/Ph, Gam/Hop and C29 normal steranes also are similar for TG oils, and suggest all oils are from a common mixed marine-terrestrial source according to discriminant plots. LT shale bitumen extract (n=3) properties indicate a different paralic-deltaic source of organic matter, containing higher concentrations of C29 normal steranes, higher Pr/Ph ratios, greater proportions of long-chain n-alkanes, and dissimilar diasterane/sterane, C30 sterane index, and tetracyclic and tricyclic terpane ratios. However, correspondence in these properties is observed between TMS bitumen extracts (n=3) and TG oils. Excluding the potential for a nearby un-sampled Previous HitoilNext Hit-prone TMS source, or long-distance lateral migration from a similar source downdip, these observations suggest: 1. the TMS is a self-sourced reservoir; 2. the TMS is the source of oils accumulated in nearby conventional TG reservoirs; and 3. thin organic-rich shales in the LT do not contribute substantially to any Previous HitoilNext Hit accumulations in the TG. Though the TMS displays poor present-day source Previous HitrockNext Hit properties, these data suggest it is the best candidate for a local source Previous HitrockTop and has apparently expelled oils to conventional reservoirs and retained oils for production by horizontal drilling and artificial stimulation.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017