Abstract Nine oils from 8 wells and one seismic shot hole and 15 solvent extracts from 8 wells in the Prudhoe Bay and North Slope region were analyzed using the following techniques: (1) column chromatographic fractionation; (2) saturate fraction gas chromatography; (3) gasoline range stripping of 25 compounds (oils only); (4) aromatic family analysis (oils and selected extracts); (5) kerogen isolation and CHN analysis (cores only); (6) total organic carbon (cores only). Normal oil-source correlation procedures for this laboratory consist of (1) normal-alkane and acyclic isoprenoid pattern interpretation and matching; (2) cluster and factor analysis of 26 gasoline range compounds; and (3) cluster and factor analysis of 16 classes of compounds in the aromatic fraction. Ancillary data such as kerogen type and quantity, level of thermal alteration, and yield and distribution of saturate, aromatic, NSO, and asphaltene classes are used to make volumetric estimates and to confirm the nature and possible distribution of the source rocks. For the North Slope core samples, low extract yields and moderate to high levels of contamination of the cores precluded useful interpretation of much of the saturate fraction GC data, and the dry storage of the cores precluded obtaining the gasoline range fraction by helium stripping. Biodegradation of two of the oil samples resulted in removal of most of the n -alkanes and acyclic isoprenoids. The Shublik Formation sample from Ikpikpuk No. 1 at a reflectance level of 1.5% and the Kingak Shale sample from North Kalikpik No. 1 at a reflectance of 0.8% (hydrocarbon yields of 46.4 and 68.4 mg/g, respectively) were the only two samples that exceeded the 30 mg/g cutoff for a potential petroleum source rock. The Kingak sample had only about 1% total organic carbon and is thus probably quantitatively insignificant as a source. Three of four other samples that had reflectance levels above 1.5% still have organic carbon contents of 1.8 to 4.5% and could have acted as sources as they passed through the optimum oil generation stage. Other samples were very low (<9 mg/g), and the extract properties have been essentially masked by contamination.

Abstract Organic geochemical data have been obtained on potential source rocks, bitumens, and oils from within and in the vicinity of a Middle Devonian carbonate-barrier complex in western Canada. Organic-carbon values in carbonate rocks vary widely (0.11 to 30.1%) according to facies type. Extract yields from immature samples from the basinal facies can be extremely high and appear to be a consequence of the highly reducing conditions in which the organic matter was deposited. Characteristic features of these high-yield extracts are a low proportion of hydrocarbon, low saturate-to-aromatic ratios, pristane-to-phytane ratios less than 1.0, a high content of acyclic isoprenoids relative to n-alkanes, and an even-to-odd predominance in the n-alkanes. The hydrocarbon yields at low levels of maturity are sufficiently high for these carbonates to be source rocks. The main migration product is heavy oil/bitumen, which shows all the characteristics of the parent-rock extracts. Locally these bitumens have been altered by heat during dolomitization to form an insoluble hydrogen-rich pyrobitumen classified as epi-impsonite. This pyrobitumen probably was formed by polymerization of the NSO/asphaltenes fraction. With increasing depth the normal rock extracts show a decline in NSO (nitrogen, sulfur, and oxygen) compounds and asphaltenes yield owing to polymerization under normal conditions of maturation but with essentially no change in hydrocarbon yield. The oils in pinnacle-reef reservoirs in the Rainbow and Zama fields south of the barrier complex also show features inherited from a source rock deposited under highly reducing conditions. These oils are more mature than heavy oils encountered in the low-maturity area.