Regional-, field-, and reservoir-scale studies of the petroleum geology, petroleum biogeochemistry, and oil fluid properties of the western Canada oil sands produce the first high-resolution model of oil charge systematics for the oil sands. The sources and alteration history of the Lower Cretaceous and underlying Mesozoic and late Paleozoic oil fields of north-central Alberta (Peace River Arch [PRA] area) were investigated using a very large database of public and in-house data to define the unaltered end-member oils that charged the oil sand reservoirs and to delineate the reservoirs in the study area that are still biologically active today. Bulk chemistry and stable isotopic analysis of oils, in combination with the quantitative analysis of biodegradation-resistant saturated and aromatic hydrocarbon molecular indicators, revealed a complex of oil charge pathways to the oil sands on a field and reservoir scale. The molecular chemistry of the Peace River oil sand bitumen shows oil charge from the Jurassic Gordondale (oil Family Z) in the west along the Montney and Gething formations, mixing with vertical oil charge from the Exshaw Formation east of the Debolt anhydrite facies pinch-out. The Peace River oil sand fields that have received significant Gordondale-sourced oil charge are able to be cold produced, whereas the dominantly Exshaw-sourced oils are too highly degraded for cold production. Most likely, no Gordondale source contributed to the Exshaw source-dominated Athabasca, Cold Lake, and Lloydminster accumulations; however, further investigation of the possibility of some low-maturity Duvernay- and/or Ostracod-sourced oil contribution to the oil sands is still warranted. The precursor oils to the Peace River, Athabasca, Buffalo Head Hills, and Wabasca oil sands were the earliest expelled, lowest maturity petroleum from these source rocks with API gravities in the 20s and with high initial viscosities. The complex vertical and lateral heterogeneities of oil compositions and fluid properties seen in the PRA area reflect variations in oil charge maturity, migration pathways, and varying levels of biodegradation, conditioned by highly variable oil charging. The complexity of the petroleum systems and variation in source organic facies observed in this study are probably typical of the extremely large petroleum accumulations that dominate the world's petroleum occurrences.