55-10 Calibrated log facies of the Eagle Ford Shale of the East Texas Basin – Implications for interpretations of the processes related to organic enrichment preceding and following Oceanic Anoxic Event 2

Session: Sequence Stratigraphic, Geochemical, and Geochronologic Correlation of the Cenomanian-Turonian Ocean Anoxic Event 2 (OAE2) in the Cretaceous Western Interior Seaway (KWIS) and the Gulf Coast

Presenting Author:

Jason Flaum

Authors:

Flaum, Jason A.¹, Birdwell, Justin E², French, Katherine³, Paxton, Stanley T.⁴, Kinney, Scott⁵, Whidden, Katherine⁶, Gardner, Rand⁷

(1) U.S. Geological Survey, Denver, CO, USA, (2) U.S. Geological Survey, Denver, CO, USA, (3) USGS, Denver, CO, USA, (4) U.S. Geological Survey, Mead, CO, USA, (5) U.S. Geological Survey, DENVER, CO, USA, (6) USGS, Denver, CO, USA, (7) US Geological Survey, Denver, CO, USA,

Abstract:

The Eagle Ford Shale of the East Texas Basin contains Cenomanian–Turonian aged deposits that vary significantly in composition, thickness, and sedimentology across the basin as well as from age-equivalent strata that comprise the continuous (unconventional) oil and gas reservoirs of southwest Texas. The lack of active exploration and development and the presence of significant gaps in the stratigraphic record across the Cenomanian–Turonian Oceanic Anoxic Event (OAE-2), which is often associated with organic enrichment and source rock potential, has led to the Eagle Ford Shale of the East Texas Basin being understudied relative to age-equivalent strata across southwest Texas. To address the lack of available information of this important stratigraphic interval, the U.S. Geological Survey Energy Resources Program drilled four shallow cores targeting the Eagle Ford Shale along the Cretaceous outcrop belt of the East Texas Basin. Core locations span from Georgetown, Texas in the southwest part of the study area to Bonham, Texas in the northeast part of the study area. These cores contain a range of lithologies that are interpreted to represent distal pelagic offshore environments to fluvial-deltaic influenced systems that vary spatially and stratigraphically across the basin. Each core completely penetrates through the Eagle Ford Shale with nearly 100% recovery. Each core also is accompanied by a full well log suite.

High resolution (≤ 2 ft.) geochemical sampling and detailed sedimentologic descriptions from core and thin section observations were completed for each core.  These data and observations provide a basis for interpretations of the spatial and temporal variability for the composition and interpreted depositional environments within the Eagle Ford Shale.  Further, these data and observations were integrated with well log properties, including gamma ray, resistivity, sonic, and density log responses, to develop calibrated, log-based facies models through the Eagle Ford within each core. The core-based models serve as calibration points for stratigraphic correlations to nearby wells. Once correlations were established, cross-sections and maps of the interpreted facies were made across the East Texas Basin to evaluate basin-scale variability of lithologies, providing key insights into the depositional processes and potential accumulation of organic-rich deposits in the intervals related to OAE-2.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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