Beitrag
Geochemical composition of oils from the Gifhorn Trough and Lower Saxony Basin in comparison to Posidonia Shale source rocks from the Hils Syncline, Northern Germany
Stock, Alexander; Littke, Ralf
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften Band 167 Heft 2-3 (2016), p. 315 - 331
veröffentlicht: Sep 1, 2016
ArtNo. ESP171016702010, Preis: 29.00 €
Abstract
Twenty-four oils from reservoirs in the Lower Saxony Basin and the adjacent Gifhorn Trough were analysed for their molecular geochemical composition, sulphur content and density (API values). The results were used to determine oil quality, degree of degradation and to correlate the oils with different source rocks known from the area. Early Toarcian Posidonia Shale was sampled at different levels of maturity for this purpose and literature data on Wealden shales were used for comparison. Oils are characterised by low to moderate sulphur contents and variable densities, including some heavy oils. Heavy oils and oils characterised by a significant hump indicating biodegradation are usually found in shallow reservoirs (depth <1500 m). All oils are characterised by a clear predominance of n-alkanes of medium-chain length over those of long chain length, which is typical of mature oils. Other parameters such as the distribution of aromatic hydrocarbons or the varying but mostly low concentration of steranes and hopanes also indicate that oils represent the peak oil generation stage. Based on ratios of iso -alkanes over n-alkanes and geological evidence, it is likely that the Posidonia Shale is the principal source rock for the oils.
Schlagworte
biodegradation • oil-source rock correlation • gifhorn trough • api gravity • lower saxony basin • thermal maturity