The Triassic Halfway and Doig formations of the Wembley Field, Alberta, comprise at least five parasequences deposited within a regressive barrier island shoreline system. The uppermost parasequence is referred to as the Halfway Formation and displays two distinct facies successions. Shoreface successions are 10-20 m thick and coarsen upward into strata of an arid marginal marine origin. Tidal inlet channel-fill sequences incise shoreface deposits and display three distinct facies successions. These are interpreted as deposited in the seaward margin, throat and backbarrier margin of the tidal inlet. The presence of welded ebb-tidal delta sandstones, abandoned-channel mudstones and an abundance of tidal flat sediments suggests that the Halfway barrier island shoreline in the Wembley Field was subjected to a tide-dominated, mixed-energy hydrographic regime. Oil and gas are produced from upper shoreface, tidal inlet channel and welded ebb-tidal delta sandstones. Tidal inlet channel-fill sediments cover approximately 90% of the field area. Ebb-tidal delta sandstones occur at the seaward margin (mouth) of individual tidal inlet channels. Upper shoreface sandstones are preserved as areally restricted erosional remnants between inlet channel fills. Although tidal inlet and ebb-tidal delta sandstones are widespread in the field, it is unlikely that they form a homogeneous reservoir unit. Updip pinch-out of these facies in abandoned channel silty shales (mud plugs) creates small-scale stratigraphic traps within each inlet channel fill. Erosional juxtaposition of successive inlet channel fills further compartmentalizes the reservoir. Understanding the distribution of the reservoir compartments helps explain production patterns in the field and to assess the most suitable methods for further development.