Geochemical comparison of core extracts and oil samples in reservoir

Molecular memory effects recording the accumulation history of petroleum reservoirs: A case study of the Heidrun Field, offshore Norway

“…Only the maturity ratios based on aromatic hydrocarbons reveal significant differences between both sample groups. For obvious reasons Baylis (1998) was not able to obtain results in agreement with the present study. His technique, involving solvent extraction of impregnated reservoir rocks in a single step, unavoidably yielded chemical maturity data on mixtures of oil impregnations from large as well as from fine pores.…”

“…This is mainly due to the use of inadequate methods for the laboratory-based extraction of such rocks. The bulk compositions of solvent extracts of oil-bearing reservoir rocks obtained by the conventional techniques (involving single-step extraction of crushed and ground samples) are mostly much different from those of DST-or production oil samples recovered from equivalent stratigraphic levels (Baylis, 1998). However, the sequential flow-through extraction technique developed by Schwark et al (1997) allows discrimination of the individual oil charges present in a single sample.…”

“…Alteration of the composition of oils impregnating reservoir sandstones due to core retrieval and sample storage is likely (Baylis, 1998). Core retrieval is associated with a drastic pressure drop which in turn leads to degassing and evaporative loss as well as perhaps precipitation of asphaltenes (Pan et al, 2005).…”

“…Furthermore, as in the case history discussed here, they concluded that these variations in maturity can be explained as ''repeated filling events from progressively maturing source rock basins''. Based on a comparison of geochemical data on extracts of impregnated reservoir rocks versus those of related DST-oils Baylis (1998) concluded ''y that it is not possible to characterise an oil definitely by examination of the core extracts''. Although this is true for the bulk composition and properties of reservoir oils, the results of the present study cast doubt on this conclusion, at least with respect to chemical maturity signatures.…”

Complex petroleum migration and accumulation in central region of southern Junggar basin, Northwest China

“…Therefore, comparison between reservoir free and adsorbed hydrocarbons should be performed (e.g., Cao et al, 2006;George et al, 1997;Karlsen et al, 1993). This method is effective because charged oils will interact with reservoir rocks continuously; as a result, the free and adsorbed hydrocarbons would have difference if multistage petroleum charge events took place (Cao et al, 2006;Pan and Yang, 2000;Baylis, 1998;Karlsen et al, 1993). Generally, the adsorbed hydrocarbons represent those that arrive in reservoirs earlier than the free hydrocarbons (Pan and Yang, 2000;Baylis, 1998;Karlsen et al, 1993).…”