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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes


Pub. Id: A031 (1985)

First Page: 621

Last Page: 638

Book Title: SG 20: Alaska North Slope Oil-Rock Correlation Study: Analysis of North Slope Crude

Article/Chapter: Organic Geochemical Properties of Alaskan North Slope Oils and Rocks: SPECIALIZED OR STATISTICAL APPROACHES

Subject Group: Geochemistry, Generation, Migration

Spec. Pub. Type: Studies in Geology

Pub. Year: 1985

Author(s): L. R. Snowdon, T. G. Powell


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 preclu ed 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 nd 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.

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