MIGRATION OF NORDEGG OIL IN THE WESTERN CANADA BASIN - HOW MUCH AND HOW FAR

Geological and organic geochemical data show that the organic-rich Low er Jurassic ''Nordegg Member'' could not have been a major source for the 269.4x10(9) m3 oil in place in the Lower Cretaceous tar sands/heav y oil deposits in eastern Alberta. Stratigraphic reconstructions indic ate that upward expulsion of ''Nordegg'' oil was prevented by the over lying Poker Chip Shale, except for a small region near the eastern sub crop edge of the ''Nordegg'', where the Poker Chip has been removed by erosion. It is only in this restricted area that the ''Nordegg'' is o verlain by permeable sands belonging to the Lower Cretaceous Mannville Group (Bluesky/Gething interval). Some ''Nordegg'' oil has been expel led downward into subcropping Triassic and Permian reservoirs. The mid dle, silty marlstone unit of the ''Nordegg'' has been suggested as the conduit for the migration of mature ''Nordegg'' oil to the eastern su bcrop edge beneath the Mannville. This theory is not supported by oil- source rock biomarker analysis of extracts from this middle unit and a djacent source rock and, thus, up-dip migration of oil through the mid dle unit of the ''Nordegg'', from mature sources in the west to low ma turity regions near the eastern subcrop edge, is not indicated. The am ount of oil expelled by mature ''Nordegg'' source rock subcropping per meable Mannville strata is estimated to range from 5.9 to 17.6x10(9) m 3 oil. This volume of oil is sufficient to have filled the Bluesky/Get hing interval in the Peace River tar sands (Eastern Alberta), but is i nsufficient to account for the additional huge volumes of oil in the u nderlying Paleozoic carbonates and other tar sands heavy oil deposits (i.e., Buffalo Head Hills, Wabasca-Grand Rapids, Athabasca, Cold Lake) .