Effect of biodegradation on tar sand bitumen of South Woodford Area, Carter County, Oklahoma

Abstract

Tar-sand bitumens from the South Woodford Area have been analyzed to study effects of biodegradation on oils and to determine their possible sources. The tar-sand deposits, located approximately 1.5 miles south of Woodford, Carter County, Oklahoma, are distributed along the crest of the South Woodford Anticline. Sixteen bitumens from the Rod Club Sandstone (Mississippian) were chosen from a single well (Fitzgerald #5) which was cored near the axis of the anticline.

This study shows that the tar-sand bitumens have been so severely biodegraded that most of the n - alkanes, low molecular weight cycloalkanes, isoprenoid alkanes, C27-C29 steranes, and light aromatics and sulfur compounds have been removed. In addition, the hopane distributions have been altered to differing degrees with those above C3 o decreasing prior to the C27-29 hopanes. The triaromatic steroid hydrocarbons are also altered with the preferential removal of C20-21 and C2 7 -28 20R species. Diasterane and C3 o -sterane distributions appear to be unaffected by biodegradation. The high resistance of tricyclic terpanes, C 24 -tetracyclic terpane and monoaromatic steroid hydrocarbons to biodegradation indicate that the distribution of these compounds are well -suited to serve as bitumen-oil correlation parameters.

Geochemical correlation between the tar sand bitumen and oils produced in the Pauls-Valley area was attempted to determine which of these oils was the source for the tar-sand bitumen. The age of the reservoir of these oils range from Ordovician to Pennsylvanian. These oils were divided into two major groups based on biomarker distribution (JONES, 1986). One group appears to be sourced by the Woodford Shale whereas the other appears to be sourced by the Viola Limestone. The tar sand bitumen-oil correlation study , based on biomarker distributions and pyrolysis-gas chromatography of asphaltenes, shows that the tar-sand bitumen is genetically-related to the group of oils derived from the Woodford Shale.