Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician-Silurian Shales in China and the U.S.

<div>Organic petrography photomicrographs (oil immersion, white incident light) (a, c–f) and SEM images (b) showing typical maceral types (graptolite and pyrobitumen) and distributions of sample TRA-10. (a, b) The microscopy (a) and SEM (b) analysis on the same area of TRA-10. The larger rectangles in (c, d, f) are enlarged areas of the related smaller rectangles. (a, b) Typical graptolite grains occurred as large pieces and oriented in a direction parallel to the bedding plane. (c, d, f) Thinner graptolite pieces dispersed within the shale matrix. (c–f) Small pyrobitumen (less than a few micrometers) grains filled in minerals and oriented in various directions. (e) Some graptolites of a spindle or lenticular shape.</div>

Geofluids

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Figure 7

Figure 7: Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician-Silurian Shales in China and the U.S. 

Figure 7 | Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician-Silurian Shales in China and the U.S. 