Reservoir Quality and Heterogeneity of Tidal Inlet Sandstones, Halfway Formation, Northeastern British Columbia, Canada

Abstract

A subsurface investigation of the mid-to-late Triassic Halfway Formation in northeastern British Columbia has identified a series of wave-dominated tidal inlet sandstones associated with transgressive and prograding barrier island shoreline trends. Depositional models and facies reconstructions were based on sedimentologic analysis approximately 60 cored sequences and 1200 well logs within the Halfway. Tidal inlet sequences are very fine to coarse-grained quartzose sandstone ranging from 4.0 to 10.0 m in thickness. Facies with greatest reservoir quality are contained within the lower half of the sequence. Fine- to medium-grained stacked fining-upward units with scoured lower contacts and planar to trough cross-bedding characterize this facies. Molluscan shell molds and casts can comprise up to 60% of an inlet sequence. Porosity values as high as 25% are associated with these coquinas.