Verlag des Forschungszentrums Jülich
JUEL-3831
Selected oil samples representing 24 oilfields in the Upper Rhine Graben have been characterized organic geochemically and correlated to their source rocks. According to these results, the following oil families (and source rocks) were differentiated:
Refering to the location of pure versus mixed oils as compound-specific calibration points, the migration history was modelled along a 45 km long NW-SE cross section with special attention to a strict application of the multiple source rock concept. In this concept, the petroleum from all four different source rocks was traced separately throughout its entire migration history. Thus, it became possible to check at any time stage how much of the petroleum in a specific grid cell of the numerical model was sourced from which source formation, and to adjust this information to the organic geochemical data.
Bruss, Dietfried
Zur Herkunft der Erdöle im mittleren Oberrheingraben und ihre Bedeutung für die Rekonstruktution der Migrationsgeschichte und der Speichergesteinsdiagenese
VIII, 222 S., 2000
In order to understand the petroleum migration history of several combined petroleum systems within the same basin (Upper Rhine Graben, SW-Germany), a numerical simulation was constrained by compositional analysis of the oils from individual fields as well as by an evaluation of the diagenetic pathway of carrier and reservoir rocks.
- Type A oils, derived from an evaporite source rock of a locally restricted anoxic, hypersaline environment with organic matter bearing a high amount of autochthonous bacterial and relatively low amounts of terrestrial input (Tertiary, Untere Hydrobien Schichten).
- Type B oils which are interpreted as being derived from a source rock of a deltaic environment with organic matter from higher land plants as well as from marine algae and bacteria (Tertiary, Pechelbronner Schichten).
- Type C oils reflecting a marine anoxic, siliciclastic source rock facies with a significant amount of organic matter from marine algae (Jurassic, Posidonia shale).
- Type D oils which were sourced by a suboxic clastic source rock unit with contributions of marine organic matter and a comparatively low input from higher land plants. The more distal, marine-dominated facies gives rise to oils distiguished by a C25 highly branched isoprenoid alkane and lower contents of oleanane (Tertiary, Septarienton).
However, in addition to this four pure oil families, mixtures of type BC and CD could be identified.
The model was further constrained by an evaluation of the petroleum emplacement within the diagenetic pathway of selected carrier and reservoir rocks.
The results of the thus constrained model of the Middle Upper Rhine Graben demonstrates
1) ... that the very recent generation of type D oils from the Tertiary Separienton became possible only by a substantial contribution of convective heat flow, predominantly in areas around faults zones.
2) ... that up-dipping carrier rocks represent the dominating migration pathways for petroleum expelled from the Jurrassic source unit (type C) which results in predominantly lateral migration.
3) ... that migration pathways for petroleum expelled from Tertiary sources (type A, B and D) was predominantly vertical due to the fault zones available at this later time.
Generally, it must be concluded that a numerical simulation of the compaction, the thermal, and the hydrocarbon generation history may hardly be sufficient for migration modelling. For a close match of the petroleum migration history, additional calibration data are needed. If several petroleum systems are combined within a basin, a good chance is provided by an organic geochemical calibration of pure versus mixed oils.
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