--> Back to the Rocks: Framework of Depositional Acmes in Source Rocks of the Gulf of Mexico Basin and North Caribbean Margin

AAPG/SEG International Conference & Exhibition

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Back to the Rocks: Framework of Depositional Acmes in Source Rocks of the Gulf of Mexico Basin and North Caribbean Margin

A. S. Pepper

This is Petroleum Systems LLC, Houston, Texas, United States

September 8, 2016 Thursday 2:00 P.M. AAPG/SEG International Conference & Exhibition, Cancun, Mexico

Abstract

Abstract

This is Petroleum Systems is building a stratigraphic framework within which all Gulf of Mexico - North Caribbean source rock data can be placed, so that the Source Potential (Ultimate Expellable Potential or UEP) of each source can eventually be mapped. This framework names each Acme of organic matter deposition for its absolute age in MY, allowing easy recognition of its regional and even wider global correlation. These correlations would otherwise be obscured by rapidly varying litho-stratigraphic nomenclature.

Acmes are recognized so far ranging from Acme 156 (late Oxfordian) to Acme 16 (Early-Middle Miocene). Depending on the depositional and preservation mechanisms, some are developed in all paleo-water depths / depositional tracts, some are limited to areas of (paleo-) deep-water deposition, while others are more prominent on shallower water shelves.

Significant lateral shelf-to-basin variations in Organofacies and quality occur, for example:

  • - Acme 148 (Tithonian) transitions from a clay-rich marine Organofacies B in the US Gulf coast to a clay-poor, carbonate-rich Organofacies Ac in the central deep-water basin and on shelves of the transform and opposing margins in Mexico.
  • - Acme 94 (late Cenomanian-Turonian) also transitions from a clay-rich marine Organofacies B in Mississippi, Louisiana and the East Texas basin to clay-poor, carbonate-rich Organofacies Ac in the central deep-water basin and on shelves of the transform and opposing margins in Mexico.
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    Acme 57 (late Paleocene-early Eocene) ranges in facies from up-dip non-marine Organofacies D/E coal measures to clay-rich shelf and slope marine Organofacies B-D/E to pelagic basinal B.

    Historically, oil families in the US have been linked to their source rocks using geologic arguments and extrapolations of oil chemistry from the onshore shelfal basins, without oil-source correlations. This is difficult, since lateral changes within an Acme will be accompanied by changes in biomarker signature. For example:

    Within Acme 156 (late Oxfordian) the signature of deep-water seeps and shows and Mexican and Cuban oils differs from that of liquids in the US onshore basins (in Smackover and Norphlet Formation reservoirs);

    In the offshore GoM, penetrated Acme 57 (late Paleocene-early Eocene) source rocks, in pelagic deep-water facies, lack the biomarker signature that is classically used to assign offshore oils to a Paleogene source.

    The presentation shows progress in resolving these basin-wide problems.

    AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016