“Depositional setting and stratigraphic framework of the Lower Triassic Montney Formation, northeastern British Columbia”, presented by Patricia Gonzáles, University of Alberta.

The Lower Triassic Montney Formation is known as a world-class unconventional petroleum reservoir system. It records sediment accumulation in a variety of depositional settings across the basin, including: siliciclastic shoreface, mixed clastic-carbonate ramp, turbidites, deltas and biostromes (Zonneveld and Moslow, 2018). In northeastern British Columbia, hydrocarbon production occurs mainly from fine- to coarse-grained siltstone reservoirs. In this area, the lithostratigrahy and stratigraphic framework of the formation are poorly understood due to complexities associated with subtle grain-size and lateral-facies variation, diminutive biogenic structures, and distribution of local discontinuities. The integration of different data sets (e.g. core descriptions, wireline logs, geochemical data, thin section analysis, SEM analysis, among others) is important to help identify mineralogical changes and stratigraphic surfaces that aid in the interpretation and correlation of predominantly fine-grained successions, such as the Montney Formation in northeastern BC. 

In this study, based on detailed core examination, twelve lithofacies and three recurring facies associations were identified within the Montney Formation, and were interpreted to represent deposition between distal offshore and lower shoreface settings, along a storm-dominated mixed siliciclastic-carbonate ramp. Sedimentological evidence suggests the area was influenced by ephemeral rivers delivering sediment to the basin, which may have constituted an important sediment source in the area. Trace fossil assemblages are characterized by low ichnodiversity and small size trace fossils, as a result of severe environmental conditions associated with the aftermath of the Permian-Triassic extinction event. Moreover, size diversity index values show an increasing upward trend, likely reflecting improved oxygenation conditions during the Spathian. 

Three third-order sequences were recognized throughout the study area. In distal portions of the basin the contacts are conformable and facies changes are subtle, challenging the recognition of the sequence boundaries. However, detailed core-to-log calibrations are proven essential for the proper identification and regional correlation of significant stratigraphic surfaces. Understanding the lateral-facies variability and overall stratigraphic framework of the Montney Formation in northeastern BC, is key in defining and correlating new potential hydrocarbon reservoirs in the area.

Location: Zoom Webinar 
Date/Time Information:  Thursday, June 11, 2020 (from 10h00 to 11h00)
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