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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 5. (May)

First Page: 845

Last Page: 845

Title: Three Oil Types in Paleozoic Rocks of Northern Denver Basin--Implications for Exploration: ABSTRACT

Author(s): Jerry L. Clayton, J. David King

Article Type: Meeting abstract

Abstract:

Analysis of 22 oil samples produced from Pennsylvanian and Permian rocks across the northern Denver basin revealed three genetically distinct oil types. One type is produced from the Permian Lyons Sandstone from fields located near the structural axis and along the west flank of the basin. This oil type is characterized by pristane-phytane ratios of less than 1.0 (average 0.8), ^dgr13C values of -28.5 to -29.1 ppt for saturated hydrocarbons, low relative amounts of n-alkanes, and absence of hopanoid biomarker compounds. The second oil type is produced from rocks of Virgilian and Wolfcampian ages in northeastern Colorado and southwestern Nebraska. This oil has a pristane-phytane ratio of about 1.5, n-alkanes dominant in the saturated hydrocarbon fraction, abunda t hopanoid biomarker compounds, and C15+ saturated hydrocarbon fractions depleted in carbon-13 compared to the Lyons oil type (^dgr13C values -28.8 to -30.4 ppt). Oil produced east of the Denver basin from rocks of the Lansing Group ("F" zone) and Ordovician rocks at Boveau Canyon and Sleepy Hollow fields, respectively, is geochemically similar to this second oil type. The third oil type is produced from rocks of Desmoinesian age. This oil has a pristane-phytane ratio near 1.0, contains intermediate amounts of n-alkanes relative to isoprenoids compared to the other oil types, and contains the isotopically heaviest saturated hydrocarbons of the three oil types (^dgr13C values -27.7 to -27.8 ppt). These three oil types have probably been generated from thre different source rocks. The geographic distribution of the Virgilian-Wolfcampian and the Desmoinesian oil types suggest at least two broad areas for possible future exploration: for the Desmoinesian type, along a trend subparallel to the eastern limit of Desmoinesian rocks in the subsurface from the Nebraska panhandle to east-central Colorado; and for the Virgilian-Wolfcampian type, along a generally east-west trend in northern Colorado, southwestern Nebraska, and northwestern Kansas.

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