Stratigraphic Architecture and Sedimentology in Relation to the Mid-Montney Sequence Boundary in Northeast British Columbia

Abstract

The Lower Triassic Montney Formation in Alberta and British Columbia is a world-class unconventional hydrocarbon reservoir housed primarily within low-permeability siltstone and, to a lesser extent, very fine-grained sandstone. Despite restriction to these two grain sizes, Montney facies are surprisingly heterogeneous. This heterogeneity results in the compartmentalization of resources within zones of distinctly different porosity and permeability. To date most published research has focussed on conventional plays in the eastern reaches of the formation in Alberta, such as the Montney Turbidite interval and shoreface clastic and bioclastic unit proximal to the subcrop limit of the play. The processes that control reservoir characteristics in the western unconventional trend are less well known. In this area subtle changes in facies demarcate large variability in reservoir characteristics, particularly porosity and permeability but also geomechanical attributes (i.e. ‘fracability’). The regional and stratigraphic distributions of these characteristics remain poorly understood. The Mid-Montney sequence boundary in British Columbia is a regional, correlatable subaerial exposure surface and marks a significant change in both inferred depositional processes and stratigraphic architecture of the Montney Formation. The reservoir characteristics of facies which straddle this boundary remain poorly understood. The Mid-Montney boundary interval is characterized by comparably high organic content. The factors controlling this organic content, the nature of the organic material and depositional environments across the boundary are the focus of the present study. This project focuses on core from the Altares/Graham and Cypress fields within northeastern British Columbia. Core within the study interval was described in detail highlighting properties such as lithology, physical and biogenic sedimentary structures and body fossils. Petrographic and petrophysical data were used to establish changes in porosity and permeability at a fine scale. A predictive model is essential for understanding the Mid-Montney boundary and ultimately to compare other producing zones within the formation. Models developed in this study will assist in regional exploration and serve to decrease risk in drilling and allow for maximum hydrocarbon recovery.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016