Changes

==Use many analytical tools==

==Use many analytical tools==

The importance of a diversified set of analytical tools cannot be overemphasized. We have noted that many published correlation efforts often rely unduly on biomarker analyses, often to the exclusion of elemental data and even [[Wikipedia:Isotope geochemistry|stable carbon isotope ratios]]. This reliance on biomarkers undoubtedly arises because of the widespread and rapid availability of molecular data through GC/MS analysis and is promoted by the existence of a large database of molecular analyses of crude oils. Nevertheless, excessive reliance on a single analytical technique can lead to erroneous correlation conclusions, especially since many of the biomarkers used in correlations are present only in concentrations of a few parts per million.

The importance of a diversified set of analytical tools cannot be overemphasized. We have noted that many published correlation efforts often rely unduly on [[Organic compounds: environmental indicators|biomarker analyses]], often to the exclusion of elemental data and even [[Wikipedia:Isotope geochemistry|stable carbon isotope ratios]]. This reliance on biomarkers undoubtedly arises because of the widespread and rapid availability of molecular data through [[Gas chromatography/mass spectrometry (GC/MS): procedures|gas chromatography/mass spectrometry (GC/MS)]] analysis and is promoted by the existence of a large database of molecular analyses of crude oils. Nevertheless, excessive reliance on a single analytical technique can lead to erroneous correlation conclusions, especially since many of the biomarkers used in correlations are present only in concentrations of a few parts per million.

Because oils are susceptible to many transformations during expulsion and [[migration]] and in the reservoir—including cracking, phase separation, and biodegradation—correlation techniques and parameters must be selected to minimize complications due to postgenetic transformations. In general, oil–[[source rock]] correlations are more difficult than oil–oil correlations, largely because we seldom have samples from the effective (mature) [[source rocks]] themselves. Problems arise from variations in facies between the basin center and the sampling point as well as from potentially large maturity differences. Condensates can be difficult to correlate because they have lost much of their valuable information during cracking, phase separation, or both.

Because oils are susceptible to many transformations during expulsion and [[migration]] and in the [[reservoir]]—including http://www.chemguide.co.uk/organicprops/alkanes/cracking.html [cracking], phase separation, and [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation]—correlation techniques and parameters must be selected to minimize complications due to postgenetic transformations. In general, oil–[[source rock]] correlations are more difficult than oil–oil correlations, largely because we seldom have samples from the effective (mature) source rocks themselves. Problems arise from variations in [[Lithofacies|facies]] between the basin center and the sampling point as well as from potentially large [[Thermal maturation|maturity]] differences. [http://www.glossary.oilfield.slb.com/en/Terms/c/condensate.aspx Condensates] can be difficult to correlate because they have lost much of their valuable information during cracking, phase separation, or both.

==Integrate geochemistry with geology==

==Integrate geochemistry with geology==