In recent years shale resource plays have become increasingly important. However, understanding the controls on reservoir quality in shale formations is still in its infancy, despite thousands of well penetrations. Using examples from several shale resource plays, including the Haynesville, the Eagle Ford and the Muskwa formations, this paper demonstrates how inorganic whole rock geochemical data that are primarily obtained to provide stratigraphic correlations can be used to model mineralogy, model TOC, determine paleoredox facies, recognize zones of biogenic silica and aid with sequence stratigraphic interpretations.

The primary application of whole rock geochemical data to date has been providing stratigraphic correlation based around changes through time in elemental composition, i.e. chemostratigraphy. Stratigraphic correlation is of paramount importance for temporally and geographically constraining other reservoir characteristics. In addition to classic chemostratigraphy, the whole rock geochemical data provide information about terrigenous inputs, which can be used to help elucidate transgressive – regressive cycles and thereby help with understanding sequence stratigraphic correlations.

Reservoir quality in shale is dependent largely on mineralogy. Major element concentrations determined for chemostratigraphy can be used to model most mineral phases, including quartz, clay (semi quantitative abundance of kaolinite, illite and chlorite), calcite, dolomite, feldspars, pyrite and apatite. By adding select trace elements, typically U and Ni, the TOC contents can also be modeled. Furthermore, it will be demonstrated how by combing SiO2 concentrations with elements derived from terrigenous sources, it is possible to recognize zones where biogenic silica is present.

Paleoredox plays an important role in determining TOC values. Consideration of redox-sensitive elements, such as V, Ni, Th, U and Mo provides a means to determine the degree of anoxia during deposition. Using examples from the Haynesville Shale, it will be shown how anoxia is determined and how it varies laterally within the basin.

The methodologies shown in this paper are readily exportable to any shale resource play. The results can be generated from core, side-wall core and cuttings samples, providing a rapid, cost effective means to assess shale in a well-bore penetration.

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