By Paul Farrimond
As the 2021 International Meeting on Organic Geochemistry (IMOG 2021, 13-16 September) draws near, I am reminded that I gave a talk at the last meeting (IMOG 2019) in Gothenburg, Sweden on the subject of leaching of immature biomarkers by crude oil as it migrates or within the reservoir.
A good example of leaching, presented in the talk, can be found in the Norwegian Central Graben, where unusually low maturity is seen in the sterane biomarkers of several of the Chalk-reservoired oilfields, particularly Hod & Valhall fields, but also Eldfisk & Ekofisk to a less extent:
Fortunately, leaching of organic matter encountered on the migration path has much less impact on other compounds in the oils, and for example the aromatic maturity parameters for these oils are directly comparable to other (non-leached) oils in the broader area. However, it is essential that the effects of leaching are identified when they occur, as the process can significantly modify the biomarker composition of an oil, resulting in erroneous interpretations, not only in terms of maturity but also source/facies and age of the source rock.
I hope that you find the presentation of interest. Click to download Farrimond 2019 IMOG Presentation