Changes

| Use samples that have suffered as little postgenetic transformation as possible || Postgenetic transformations—especially [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation], cracking, and [http://www.gazprominfo.com/terms/topping-gas/ gas stripping] of oils—can make positive correlations very difficult. Also, all oil–source rock correlations are complicated by the fact that significant compositional changes occur as the oil is expelled from the source rock and migrates.

| Use samples that have suffered as little postgenetic transformation as possible || Postgenetic transformations—especially [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation], cracking, and [http://www.gazprominfo.com/terms/topping-gas/ gas stripping] of oils—can make positive correlations very difficult. Also, all oil–source rock correlations are complicated by the fact that significant compositional changes occur as the oil is expelled from the source rock and migrates.

|-

|-

| Use source rock samples that are mature, not post mature || Since many source rock samples are immature, a comparison with mature oils can be difficult—not only because physical appearances and molecular distributions are different, but also because extracts from immature rocks are sometimes genetically unrelated and compositionally dissimilar to mature extracts and oils.<ref name=ch08r26>Kohnen, M., E., L., Schouten, S., Sinninghe Damste, J., S., de Leeuw, J., W., Merrit, D., Hayes, J., M., 1992, The combined application of organic sulphur and isotope geochemistry to assess multiple sources of palaeobiochemicals with identical carbon skeletons: Organic Geochemistry, vol. 19, p. 403–419, DOI: 10.1016/0146-6380(92)90008-L.</ref>

| Use source rock samples that are mature, not post mature || Since many source rock samples are immature, a comparison with mature oils can be difficult—not only because physical appearances and molecular distributions are different, but also because extracts from immature rocks are sometimes genetically unrelated and compositionally dissimilar to mature extracts and oils.<ref name=ch08r26>Kohnen, M. E. L., S. Schouten, J. S. Sinninghe Damste, J. W. de Leeuw, D. Merrit, and J. M. Hayes, 1992, The combined application of organic sulphur and isotope geochemistry to assess multiple sources of palaeobiochemicals with identical carbon skeletons: Organic Geochemistry, vol. 19, p. 403–419, DOI: 10.1016/0146-6380(92)90008-L.</ref>

|}

|}