Basin and petroleum system modeling tools can aid in assessing unconventional resources. The present study gives an overview of the petroleum system of the Western Canada Sedimentary Basin (WCSB) through the modeling of a representative regional geologic cross section. A special emphasis is given on the Triassic Montney and Doig formations, which host the largest known unconventional play in Canada. Our model simulated the large diversity of plays that are found in the WCSB: self-sourced and tight reservoirs as well as conventional reservoirs with conventional and biodegraded oils. Results of this study strengthen the hypothesis of long-distance (>100 km [>62 mi]) migration for a major part of the hydrocarbons generated by the Gordondale and Doig Phosphate source rocks from the western to the eastern part of the basin. They also show that hydrocarbons generated within the Montney formation did not migrate far from their source rock due to very low permeabilities. Although the quantification of expelled versus generated hydrocarbons is still in its infancy, our results suggest that as much as half of the hydrocarbons generated in the Montney-Doig formations might still be retained in their source rock. Extending such a model in three dimensions might help improving the assessment of the volumes and distributions of dry gas, liquid-rich gas, and oil present in the low-permeability Montney and Doig formations.