TEst 2

Approach: Mowry Formation cores in 6 wells form the basis of stratigraphic and facies models. These were used in the generation and calibration of a petrophysical electrofacies model from a dataset of 14 wells, enabling facies interpretation to be extended into the uncored intervals of the Mowry Formation in the study wells

Results & Conclusions: Facies mapping highlighted variations in hypothesized bottom-water oxygenation and quartz sand input. These maps were then combined with 3D seismic attribute, published geochemical and automated mineralogical data, to identify the distribution of depositional facies as a means of improving understanding of reservoir potential.

• Close trends between facies distribution, seismic attributes, average TOC, kerogen types and brittle mineral phases were discovered.
• Regions with lower bottom water oxygenation and lower sand content exhibited lower proportions of brittle phases, higher TOC and a greater proportion of Type II kerogen.
• Regions of higher bottom water oxygenation and higher sand input typically exhibited greater proportions of brittle phases, lower TOC and a greater proportion of Type III kerogen. These more oxygenated, high sand input facies form distinct lobes originating from a paleoshoreline located to the west.

Correlation of facies between wells, guided by seismic attribute maps where available, highlighted a series of large lobe-shaped sedimentary bodies, originating from the western margins of the basin (Figure 4).

• These lobes were largely dominated by oxic to suboxic subtidal sheet facies and tended to have a higher quartz sand and other brittle phase content than the surrounding shales.
• Wells outside of these lobes exhibited more anoxic sediments and less quartz sand. The lobes also displayed-lower TOC values, higher proportion of Type III kerogen and local increased freshwater palynomorph input compared to the surrounding shales.
• Seismic attribute maps highlighted the oxic-suboxic, low TOC regions as being dominated by low density shale (Figure 3) – typically attributed to higher TOC and associated shale porosity.

See Also:

Kenny, R., Davies, C., Purvis, S., Fenton, J., Pandey, V., Iwobi, C., Bose, S., Trevino, R. and Chesser K., 2016. Reservoir Quality and Stratigraphy of the Frontier to Dakota Interval of the Powder River Basin, a Core-Log-Seismic Exercise. URTeC: 2458840.

Davies, C., Purvis, S., Kenny R., Fenton, J., Pandey, V., Geesaman, K., Trevino, R., Iwobi, C., Watford, M. and Bose, S., 2015. Reservoir quality and stratigraphy of the Mowry and Muddy interval of the Powder River Basin, Wyoming, USA. EAGE First Break, v.33, p. 63-68.