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The Jurassic-Cretaceous foreland basin of the Western Canada Sedimentary Basin (FB-WCSB) is considered one of the premier hydrocarbon provinces of North America. The FB-WCSB is characterized by multiple conventional and unconventional stacked reservoirs within in a deep basin system (DBS), and can be organized into:

• A lower Underfilled foreland basin, with the main reservoir units associated with the Jurassic to Lower Cretaceous Nordegg, Poker Chip, Rock Creek, Fernie-Nikinassin, Mannville (and stratigraphic equivalents); and
• An upper Overfilled foreland basin consisting of the Joli Fou, Viking, SWS, Cardium and Belly River (and equivalents).

An analysis of both the top 20 oil/condensate rates and top 20 natural gas rate wells (grouped on a boe/d basis from Alberta in 2015) were organized into pre-foreland basin, underfilled foreland basin and overfilled foreland settings. Fifteen of those wells were from pre-foreland deposits. Of the 25 top wells from the foreland basin:

• 4/20 of the top 20 oil/condensate wells (20%) in the Deep Basin are characterized as occurring in the Overfilled Foreland Basin setting (Dunvegan, Belly River);

• 1/20 of the top 20 oil/condensate wells (5%) are in the Deep Basin Underfilled Foreland Basin (Gething);
• 20/20 of the Top 20 gas wells (100%) are Deep Basin Underfilled foreland Basin (Spirit River Group – Wilrich, Falher and Notikewin).

The Underfilled Foreland Basin is characterized by restricted marine and marginal marine mixed carbonate and clastic deposits (Nordegg-Rock Creek) sourced from the south and east; overlain by clastic dominated fluvial to marginal marine (shoreline, deltaic and estuarine) deposits of the Fernie (Nikinassin), Lower Mannville (Basal Quartz – Ellerslie, Ostrocod, Glauconitic, Spirit River (Wilrich, Falher and Notikewan) and Upper Mannville.Accommodation space increases to the north and northwest. Paleodrainage associated with the Underfilled Foreland Basin is characterized by fluvial and fluvial deltaic systems oriented dominantly from south and southeast towards north and northwest, splitting around paleotopographic highs associated with erosional remnants preserved from the migration of peripheral forebulge events. Shorelines are dominantly oriented east-west and are organized into falling stage, lowstand, transgressive, and highstand parasequences and parasequence sets. The shorelines are segmented along strike into compartments due to multiple point sources of sediment from the multiple S-N oriented fluvial and fluvial deltaic systems occurring along the length of the shorelines.

The transition between Underfilled and Overfilled Foreland Basin deposits is marked by a reorganization of paleodrainage and associated shoreline orientation. The Overfilled Foreland Basin is characterized by clastic dominated fluvial to marginal marine fluvial, deltaic, estuarine, shoreface and shelf deposits sourced from the west. Paleodrainage associated with the overfilled foreland basin is characterized by fluvial and fluvial deltaic systems oriented from west to east. Shorelines are oriented north-south, parallel to the length of the foreland basin.Key reservoir targets are associated with the Dunvegan fluvial, distributary and deltaic), Belly River (channels, shorefaces) and Cardium/Second White Specks).

The organzation of the WCSB-FB reservoirs into Underfilled vs Overfilled FB settings, and a detailed understanding of both the depositional environment and sequence stratigraphic framework are the first hierarchical steps in the better understanding of Deep Basin conventional and unconventional targets. According to Bhattacharya (2016), the source-to-sink (S2S) concept is focused on quantification of the various components of clastic sedimentary systems, from initial source sediment production areas, through the dispersal system, to deposition within a number of potential ultimate sedimentary sinks. During the Jurassic-Early Cretaceous (WCSB - Underfilled Foreland Basin), fluvial systems consisting of continental-scale low slope, axially drained rivers, formed the 40-m-deep channels in the Mannville Group in Canada. During times of maximum transgression (WCSB – Overfilled Foreland Basin) of the Cretaceous Seaway, such as the Turonian and Campanian, the western North American foreland basin was characterized by smaller-scale (typically 10-m deep), steeper gradient sand and gravel bedload rivers, dominated by transverse drainages in the rising Cordillera. This created a number of smaller river-delta S2S systems along the coast, such as the Dunvegan, Ferron, Frontier, Lance and Cardium formations.

Conventional (conglomerate shoreface) reservoirs were major exploration targets from their first discovery in the late 1970s until the advent of horizontal drilling in the Deep Basin in 2005. Primary porosity (3 to 8%) and permeability (1 to 50md Kmax) of the conglomeratic reservoirs are well within the conventional range of reservoir quality. Highest Kmax values are associated with bimodal to unimodal clast-supported, chert-pebble conglomerate facies.

In contrast, unconventional reservoirs are associated with lowstand to falling stage, low accommodation, pebbly chert sublitharenite and quartzose sandstone comprised of shoreface- to- wave dominated delta facies associations.Matrix permeability values are below the resolution of routine core analysis in these characteristically “tight” unconventional reservoirs, which are exploited almost exclusively through horizontal drilling and multi- stage frac completions. The Spirit River Group (Wilrich, Falher and Notikewin), commonly referred to as the “Wilrich” resource play are an excellent example. Reservoir attributes are interpreted to be the product of deposition on low profile, dissipative shoreface/delta fronts developed in a low accommodation setting. The reduced accommodation space results in commonly occurring incisions of shorefaces and delta front facies by fluvial and estuarine channels. Conglomeratic and coarse grained shoreface parasequences are products of deposition on steep profile, highly reflective shorefaces in high accommodation settings. In contrast, finer grained shoreface and delta front parasequences are products of deposition on low profile, dissipative shoreface/delta fronts in low accommodation settings.