Evolution and Reservoir Development of an Ancient Carbonate-Siliciclastic Ramp Margin: Middle Triassic of Western Canada

Mark A. Radomski, Thomas F. Moslow, and Charles M. Henderson
Department of Geoscience, University of Calgary, Calgary, AB, Canada

The Middle Triassic Halfway Formation in west-central Alberta is interpreted as a series of prograding shoreface facies associations in a ramp setting within a progradational series of parasequence sets. These parasequence sets have been reworked syn-depositionally by laterally discontinuous tidal inlet channels cutting perpendicular to the shoreline trend. Within the study area the Halfway interval consists of a condensed section of mixed carbonate-siliciclastic margin/ramp facies and has been the focus of a detailed sedimentological study to refine depositional models, predict reservoir architecture, and determine the evolution of this margin/ramp succession.

Nine lithofacies from the Halfway interval have been described within this study and environmental interpretations range from offshore marine to arid continental. Five facies association have been created by grouping commonly occurring lithofacies. These facies association groupings include: distal shoreface and proximal shoreface siliciclastics, tidal inlet/channel bioclastic fill, continental evaporates, and biostrome carbonates. Major exploration targets from this region include tidal inlet/channel fill as well as proximal shoreface sandstone.

The evolution of this Middle Triassic mixed carbonate-siliciclastic ramp succession is of interest as evidence gathered in this study suggests a complex reservoir history including multiple events of deposition, tectonism, erosion, diagenesis, and hydrocarbon emplacement. An understanding of these events and their relative timing and magnitude is critical in order to create an accurate exploration model of this shoreline-ramp reservoir trend.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas