Environmental Engineering Reference
In-Depth Information
This post-depositional aspect of ichnofabric obviously is of considerable
interest to exploration geologists and hydrogeologists because it demonstrates
the direct influence that biogenic processes have on the migration and pool-
ing of fluids in porous media. Since most Phanerozoic sedimentary rocks
exhibit an ichnofabric of one sort or another, it follows that ichnofabric data
must be a component in the characterization and evaluation of oil, gas, and
water reservoirs. This is especially true when examining drill cores for
hydrocarbon exploration. Ichnofabrics are commonly described in core
( Bockelie, 1991; Gerard and Bromley, 2008; Knaust, 2009, 2010; Martin
and Pollard, 1996; McIlroy, 2007; Taylor and Goldring, 1993 ), whereas
specific ichnotaxa are not always recognized with ease and identified with
certainty in core.
Given the expense of recovering drill cores from the subsurface, and in the
light of the invaluable information they can provide to the exploration or res-
ervoir geologist, ichnological analysis is a crucial part in the description and
interpretation of well cores (see Knaust, 2012 ). A few selected examples of
common ichnofabrics in typical marine reservoirs from offshore Norway illus-
trate common ichnofabrics and their appearance in slabbed cores and demon-
strate their value for reservoir characterization ( Figs. 4-7 ).
5. CONCLUSIONS
The ichnofabric concept and application of the techniques of ichnofabric anal-
ysis that derive from the concept have proven to be robust and resilient. Sedi-
mentologically, ichnofabric can be used as a way to assess the degree or
intensity of bioturbation. It is also a direct reflection of sediment consistency
and sedimentary dynamics within the depositional environment, and as such
it may be a crucial tool in interpreting event sedimentation. Geochemically,
the dynamics of interstitial oxygen concentrations will be reflected in different
ichnofabrics. Paleoecologically, ichnofabric provides a direct reflection of the
endobenthic community, including the vertical tiering structure of the ichno-
coenosis. Taphonomically, ichnofabric ostensibly contributes to the diagenetic
fabric that results from lithification of a burrowed sediment. Stratigraphically,
recurrent ichnofabrics can be used effectively for correlation in certain situa-
tions within sedimentary basins. Practically, the analysis of ichnofabrics can
be used as a powerful describer of reservoirs.
ACKNOWLEDGMENTS
The authors' ideas about ichnofabrics have benefited considerably from the shared thoughts
and insights of many astute colleagues over the past three decades. Much of the early work on
ichnofabrics by A. A. E. was supported by research grants from the National Science Foun-
dation. D. K. is grateful to Statoil for permission to publish the data presented in Figs. 4-7 . The
review of Jean Gerard greatly improved this chapter.
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