Petrographic analysis provides a detailed description of the texture (grain size, sorting,
and grain contacts), sedimentary structures (laminations, bioturbation), framework grain composition,
authigenic minerals, and types and distribution of macroporosity seen in a thin section. Detailed
petrographic techniques can be used in porosity modeling programs and analysis with ultraviolet light
can be useful in delineating features that are too small to be easily recognized with standard petrographic
Petrographic analysis can be used to evaluate the pore system in a reservoir rock. The occurrence and
distribution of pore types can be identified, and pore structure analysis can determine the ratio of primary
intergranular pores to secondary leached pores and provide critical data for evaluation the efficiency of the
Petrographic Analysis for Burial History Modeling
A highly detailed petrographic analysis can be used as petrographic input for specific burial history modeling
programs and reservoir characterization models. This type of modal analysis includes a point count (minimum of
300 points) of over 150 categories of framework grains, cements, and matrix, estimation of amounts of grain coats
(typically 50 grains), and grain measurements (generally a minimum of 100 grains).
Epifluorscence petrography uses ultraviolet light to emphasize features in a thin section that are difficult to observe
with standard petrographic techniques. This technique is especially useful in identifying and describing microfractures
and microporosity in shale thin sections.
Staining techniques can be used in preparing the thin sections to better enable identification of various carbonate minerals.
Dual carbonate stains will differentiate ferroan carbonates (mauve), ferroan dolomite (blue) and calcite (red) above). In
cross-polarized light, these carbonate minerals have similar optical characteristics and can be otherwise difficult to
distinguish. Cross-polarized light is used to easily identify twinned feldspar and quartz overgrowths (below).
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