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 [[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.

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 oil]]s. 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 [[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.

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 [[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.