Abstract The organic-rich marine shales of the Upper Jurassic - lowermost Cretaceous Farsund Formation are the main hydrocarbon source rocks for the Cretaceous chalk reservoir of the Valdemar Field (Danish North Sea). Geochemical analyses of oil extracts from core samples across the greater Valdemar Field show substantial heterogeneity of the reservoir oils, suggesting contribution from kitchen areas with source rocks of variable organofacies and thermal maturity. In order to better understand the source rock facies that charged the field, a refined organofacies characterization of the Upper Jurassic - lowermost Cretaceous marine shale source rock succession (Farsund Formation) in the Danish Central Graben was established. This organofacies characterization is based on integration of petrographic and geochemical data and demonstrates large variations in both the regional and local distribution of the organofacies at the sequence level in the shales within the Danish Central Graben. In addition, the organofacies characterization shows that the respective sequences in the succession may be represented by several organofacies at the same time. Part of the explanation to the heterogeneity in the oil types accumulated within the Valdemar Field may lie in the presence of different organofacies within the uppermost sequences (Vol-3 to Ryaz-1) in the three kitchen areas. Each organofacies presumable generates different types of oils and the variation in the relative proportions of the different organofacies likely determines the composition of the generated oils. One dimensional (1-D) maturity modelling at three pseudo-well locations, each representing a potential Farsund Formation kitchen, shows that all kitchens are in the main oil window and that mainly oil was expelled from the Volg-3 to Ryaz-1 sequences. Modelling indicates that (i) average values of TOC, HI, thickness and the kinetic model are the main controls on generation and expulsion of hydrocarbons; and (ii) by increasing these parameters, expulsion could also occur from the lower part of the succession.

中文翻译：

---

上侏罗统 - 最下白垩统烃源岩、丹麦中央地堑的有机相组成，以及对 Valdemar 油田石油相关性的洞察

摘要 上侏罗统—最下白垩统法尔松组富含有机质海相页岩是瓦尔德马油田（丹麦北海）白垩纪白垩系的主要烃源岩。对整个 Valdemar 油田岩心样品的石油提取物进行的地球化学分析表明，储层油具有显着的非均质性，这表明来自具有可变有机相和热成熟度的烃源岩的厨房区域的贡献。为了更好地了解该油田的烃源岩相，建立了丹麦中央地堑中上侏罗统 - 最下白垩统海相页岩烃源岩序列（法尔松组）的精细有机相特征。这种有机相表征基于岩石学和地球化学数据的整合，并证明了丹麦中央地堑内页岩层序水平上有机相的区域和局部分布的巨大变化。此外，有机相表征表明，连续的各个序列可能同时由几个有机相表示。对 Valdemar 油田内积累的石油类型的异质性的部分解释可能在于三个厨房区域的最上层序列（Vol-3 至 Ryaz-1）内存在不同的有机相。据推测，每种有机相产生不同类型的油，不同有机相的相对比例的变化可能决定了所产生油的组成。三个假井位置的一维 (1-D) 成熟度建模，每个位置都代表一个潜在的 Farsund 地层厨房，显示所有厨房都在主油窗口中，并且主要是油从 Volg-3 到 Ryaz-1 序列. 建模表明 (i) TOC、HI、厚度和动力学模型的平均值是控制油气生成和排出的主要因素；(ii) 通过增加这些参数，也可以从序列的下部发生驱逐。厚度和动力学模型是控制油气生排烃的主要因素；(ii) 通过增加这些参数，也可以从序列的下部发生驱逐。厚度和动力学模型是控制油气生排烃的主要因素；(ii) 通过增加这些参数，也可以从序列的下部发生驱逐。