By Paul Hackley, Brian Cardott
Organic petrography via incident light microscopy has broad application to shale petroleum systems, including
delineation of thermal maturity windows and determination of organo-facies. Incident light microscopy allows
practitioners the ability to identify various types of organic components and demonstrates that solid bitumen
is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity, whereas
oil-prone Type I/II kerogens have converted to hydrocarbons and are not present. High magnification SEMobservation
of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs
has enabled major advances in our understanding of hydrocarbon migration and storage in shale, but suffers
from inability to confirm the type of organic matter present. Herein we review organic petrography applications
in the North American shale plays through discussion of incident light photographic examples. In the first part of
the manuscript we provide basic practical information on the measurement of organic reflectance and outline
fluorescence microscopy and other petrographic approaches to the determination of thermal maturity. In the
second half of the paper we discuss applications of organic petrography and SEM in all of the major shale petroleum
systems in North America including tight oil plays such as the Bakken, Eagle Ford and Niobrara, and shale
gas and condensate plays including the Barnett, Duvernay, Haynesville-Bossier, Marcellus, Utica, and Woodford,
among others. Our review suggests systematic research employing correlative high resolution imaging techniques
and in situ geochemical probing is needed to better document hydrocarbon storage, migration and wettability
properties of solid bitumen at the pressure and temperature conditions of shale reservoirs.
Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).