This paper presents the first detailed organic geochemistry and petrography of the Lower Cretaceous tight reservoir units from the Valdemar Field, Danish Central Graben. The Tuxen and Sola formation chalks and the interbedded argillaceous Munk Marl Bed and Fischschiefer Member, respectively, contain thermally immature marine Type II kerogen, mainly algal liptinites, degraded bituminite and late-oil solid bitumen. The more clay-rich Fischschiefer Member and Munk Marl Bed constitute a relatively efficient seal for vertical migration and have significantly higher kerogen content as compared to the more calcareous Sola and Tuxen reservoirs. Evidence for significant oil migration can be observed across all the lithounits, highest in the Tuxen Fm which also constitute the main reservoir. Microscopic observations show a widespread distribution of granular degraded bituminite, formed by microbial degradation and diagenetic alteration of liptinites, and late-oil solid bitumen precipitated from the migrated oils. Biomarkers from rock extracts indicate open-marine depositional conditions of the source rocks that charged the hydrocarbons, having a geochemical composition similar to oils charged from the Upper Jurassic–lowermost Cretaceous Farsund Formation. The solid bitumen within such heterogeneous reservoir units might influence both reservoir quality and petrophysical properties.

本文介绍了丹麦中格拉本Valdemar油田下白垩统致密储层单元的第一个详细的有机地球化学和岩石学。图克森和索拉地层的白垩以及互层的泥质质的蒙克马尔床和费希切弗成员分别包含热不成熟的海洋II型干酪根，主要是藻类脂蛋白，降解的沥青和晚油的固体沥青。与石灰质的Sola和Tuxen储层相比，粘土含量更高的Fischschiefer Member和Munk Marl Bed构成了垂直运移的相对有效的密封层，且干酪根含量明显更高。可以在所有岩石单元上观察到大量石油运移的证据，在也构成主要储层的图克森组中最高。显微观察显示，由于微生物的降解和脂质岩的成岩作用而形成的粒状降解沥青的广泛分布，以及从迁移的油中沉淀出的后期油状固体沥青。岩石提取物中的生物标志物表明烃类的烃源岩在海洋中的沉积条件，烃类的地球化学成分与侏罗纪-最下白垩统Farsund组的烃类相似。这种非均质储层单元中的固体沥青可能会影响储层质量和岩石物性。岩石提取物中的生物标志物表明烃类的烃源岩在海洋中的沉积条件，烃类的地球化学组成与侏罗纪-最下白垩统Farsund组的烃类相似。这种非均质储层单元中的固体沥青可能会影响储层质量和岩石物性。岩石提取物中的生物标志物表明烃类的烃源岩在海洋中的沉积条件，烃类的地球化学组成与侏罗纪-最下白垩统Farsund组的烃类相似。这种非均质储层单元中的固体沥青可能会影响储层质量和岩石物性。