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| Poor production test flow rates
| Poor production test flow rates
| Low viscosity (due to oil source or [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation]) or high wax paraffinic
| Low viscosity (due to oil source or [[biodegradation]]) or high wax paraffinic
| Bulk properties, GC, and HPLC
| Bulk properties, GC, and HPLC
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Molecular compositions can be used to categorize oils (such as waxy or paraffinic and aromatic) and to determine the effects of geological processes (such as [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegraded], water washed, or immature). Bulk properties such as API gravity can sometimes be predicted from molecular composition data.<ref name=pt05r94>Kennicutt, M. C., and J. M. Brooks, 1988, Surface geochemical exploration studies predict API gravity off California: Oil and Gas Journal: Sept. 12, p. 101–106.</ref> Chromatographic methods are typically used to determine these characteristics.
Molecular compositions can be used to categorize oils (such as waxy or paraffinic and aromatic) and to determine the effects of geological processes (such as [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegraded], water washed, or immature). Bulk properties such as API gravity can sometimes be predicted from molecular composition data.<ref name=pt05r94>Kennicutt, M. C., and J. M. Brooks, 1988, Surface geochemical exploration studies predict API gravity off California: Oil and Gas Journal: Sept. 12, p. 101–106.</ref> Chromatographic methods are typically used to determine these characteristics.
Gas chromatography (GC) data can indicate the geological mechanisms responsible for changes in composition of an oil. For example, during biodegradation, bacteria preferentially remove the ''n''-paraffins that are prominent features in most chromatograms ([[:file:oil-and-condensate-analysis_fig2.png|Figure 2]]). Therefore the decrease or absence of n-paraffins is a strong indication that an oil is biodegraded. Other geological processes recognizable from chromatograms are thermal immaturity (odd-even predominance of the ''n''-paraffins), water washing (depletion of light aromatics), leaky reservoir seals (loss of light ends), and source characteristics (biomarkers) ([[:file:oil-and-condensate-analysis_fig3.png|Figure 3]]). Drilling additives and contaminants can also be identified by chromatography ([[:file:oil-and-condensate-analysis_fig4.png|Figure 4]]).
Gas chromatography (GC) data can indicate the geological mechanisms responsible for changes in composition of an oil. For example, during [[biodegradation]], bacteria preferentially remove the ''n''-paraffins that are prominent features in most chromatograms ([[:file:oil-and-condensate-analysis_fig2.png|Figure 2]]). Therefore the decrease or absence of n-paraffins is a strong indication that an oil is biodegraded. Other geological processes recognizable from chromatograms are thermal immaturity (odd-even predominance of the ''n''-paraffins), water washing (depletion of light aromatics), leaky reservoir seals (loss of light ends), and source characteristics (biomarkers) ([[:file:oil-and-condensate-analysis_fig3.png|Figure 3]]). Drilling additives and contaminants can also be identified by chromatography ([[:file:oil-and-condensate-analysis_fig4.png|Figure 4]]).
If proper standardized procedures are followed, chromatograms can provide reproducible “fingerprints” of oils. These oil fingerprints can then be used to compare and correlate oils. This technique of molecular characterization is more discriminating than bulk property data.<ref name=pt05r88>Kaufman, R. L., A. S. Ahmed, and R. J. Elsinger, 1990, Gas chromatography as a development and production tool, in Geochemistry of Gulf Coast Oils and Gases: Proceedings of the 9th Annual Research Conference, Gulf Coast Section, Society of Economic Paleontologists and Mineralogists, p. 263–282.</ref> For ease in interpretation, chromatographic data can also be displayed as polar or star plots of hydrocarbon peak ratios ([[:file:oil-and-condensate-analysis_fig5.png|Figure 5]]).
If proper standardized procedures are followed, chromatograms can provide reproducible “fingerprints” of oils. These oil fingerprints can then be used to compare and correlate oils. This technique of molecular characterization is more discriminating than bulk property data.<ref name=pt05r88>Kaufman, R. L., A. S. Ahmed, and R. J. Elsinger, 1990, Gas chromatography as a development and production tool, in Geochemistry of Gulf Coast Oils and Gases: Proceedings of the 9th Annual Research Conference, Gulf Coast Section, Society of Economic Paleontologists and Mineralogists, p. 263–282.</ref> For ease in interpretation, chromatographic data can also be displayed as polar or star plots of hydrocarbon peak ratios ([[:file:oil-and-condensate-analysis_fig5.png|Figure 5]]).