Heterogeneity of the Mineralogy and Organic Content of the Tuscaloosa Marine Shale


Many unconventional clay-rich oil and gas reservoirs are characterized by fine-scale heterogeneity that is challenging to characterize and predict at larger scales. This is particularly problematic in emerging shale plays with limited shared knowledge such as the Tuscaloosa Marine Shale (TMS). The TMS is located within the Central U.S. Gulf Coast region and contains an estimated 7 billion barrels of potentially recoverable oil. In this study we synthesized and interpreted newly available mineralogical and organic geochemical data from 11 wells located in the currently producing area of the TMS. The data are extremely heterogeneous within individual wells, but generally suggest that the basal region of the TMS within the producing region is characterized by higher concentrations of calcite and TOC relative to other areas of the TMS. Data from an ∼18 m section near the base of the TMS (including samples from all 11 wells) averaged 1.65 wt% TOC, 22.8 wt% quartz, 17.2 wt% calcite, 16.2 wt% kaolinite, 14.1 wt% illite, 11.8 wt% smecite, 5.7 wt% chlorite, 3.9 wt% plagioclase, and 4.4 wt% pyrite. Kerogen in this region is a mixture of Type II and Type III and Tmax and vitrinite reflectance data suggest that samples from most wells are within the oil and wet gas generation window. Comparisons to previous investigations of the TMS show that most studies are in reasonable agreement only at the largest scales of observation and break down at smaller scales such that the concentrations of minerals and organic matter reported depend largely on the scale and locations of the investigation and the sampling density. Hence, the best approach for quantifying, describing, and ultimately predicting the heterogeneous physical and chemical properties within TMS may be to rely upon statistically-based comparisons of groups of data such that probability distributions of these groups can be generated that vary with the changing stratigraphy and depositional environments.


Geosciences and Geological and Petroleum Engineering

Research Center/Lab(s)

Center for Research in Energy and Environment (CREE)


This material is based upon work supported by the Department of Energy National Energy Technology Laboratory under Award Number DE-FE0031575

Keywords and Phrases

Heterogeneity; Kerogen; Mineralogy; Scale; TOC; Tuscaloosa marine shale

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Article - Journal

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© 2019 Elsevier Ltd, All rights reserved.

Publication Date

01 Nov 2019