USING BIOMARKERS TO DETERMINE UNKNOWN ORIGINS OF OIL IN A MISSISSIPPIAN CARBONATE RESERVOIR, CENTRAL OKLAHOMA, USA

Understanding the origin of oils contributing to a reservoir can reveal valuable information about where to drill for oil and gas. Previous research shows that oils found in the Mississippian-age carbonate reservoir in central Oklahoma are chemically heterogeneous, and that one or more sources is still unknown. Previous studies indicate the oil generated in the Woodford Shale migrated into the carbonate layer above and was trapped in that reservoir. The other sources of oil in the carbonate layer are still unidentified. It is a possibility that the carbonate layer itself is generating oil, and that oil remains in the carbonate layer. My proposal is to determine if some of the oil found in this carbonate reservoir was generated there or if all of the oil migrated into the Mississippian carbonate layer after generation in the underlying Woodford Shale. I hypothesize that the Mississippian carbonate reservoir is self-sourced in addition to being sourced by the underlying Woodford shale.

To determine if a portion of the oil in the Mississippian carbonate layer is generated in that same layer, I analyzed the petroleum biomarkers in the organic material found in core samples from the Mississippian carbonate layer and compared them to the biomarkers in previously measured oil samples. The samples were from two cores located in western Payne County, and I selected three samples from each core based on lithology and porosity. Using Gas Chromatography-Mass Spectrometry (GC-MS), I analyzed the samples for biomarkers high in carbonates but low in shales. By comparing my results with GC-MS data of previously studied oil samples from the carbonate reservoir, I have found that preliminary results indicate that the oil samples contain biomarkers that match those of the carbonate rock samples. Therefore, it is likely that a portion of the oil was formed in the carbonate layer, indicating that the Mississippian carbonate is an oil source.