The Danish Central Graben, North Sea, is a mature oil‐ and gas‐producing basin in which the principal source rocks are the Upper Jurassic – lowermost Cretaceous marine shales of the Farsund Formation (Kimmeridge Clay Formation equivalent), with possible additional potential in the directly underlying Lola Formation. This study investigates the initial source rock potential of the basin by evaluating the original (back‐calculated) source rock properties (TOCo, S2o, HIo) of the shales in the Farsund and Lola Formations within a temporal and spatial framework. About 4800 samples from 81 wells regionally distributed in the Danish Central Graben were included in the study. Samples for source rock analysis were in general collected with varying sampling density from the entire shale section. The shale section has been divided into seven units (referred to as pre‐FSU1 to FSU6; FSU: Farsund Seismic Unit) which are delineated by mappable, regional‐scale seismic markers. For the pre‐FSU1 and FSU2–FSU6 units, the number of available samples ranged from 608 to 1145, while 433 samples were available for FSU1. Good source rock quality varies through space and time and reflects both the structural development of the basin and the effects of the Late Jurassic transgression, with primary kitchen areas developing in the Tail End Graben, Feda Graben, Gertrud Graben and the Rosa Basin. The source rock quality of the shales increases gradually through time and reaches a maximum in FSU6 which includes the “hot shales” of the Bo Member. The maximum source rock quality appears to correspond to an original Hydrogen Index (HIo) of approximately 675 mg HC/g TOC. The proportion of oil‐prone samples per unit (with HIo >350 mg HC/g TOC) ranges from 7 to 11% in the pre‐FSU1 to FSU2 units (Lower Kimmeridgian – Lower Volgian), increasing to 18 – 22% in FSU3 and FSU4/FSU5 (Lower Volgian – Middle Volgian), and reaching a maximum of 53% in FSU6 (Upper Volgian – Ryazanian). FSU6 is the most prolific oil‐prone source rock interval, but the presence of oil‐prone intervals in older and deeper parts of the shale succession is important for assessing the generation potential of the Upper Jurassic petroleum system. The breakdown of the Upper Jurassic – lowermost Cretaceous shale section into mappable seismic units with assigned original source rock properties will contribute to a considerably improved understanding of the temporal and spatial distributions of source rock quality in the Danish Central Graben.

中文翻译：

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丹麦北部中部侏罗纪-下低层白垩纪海洋页岩上原始烃源岩的时空分布

丹麦北海格拉本中部地区是一个成熟的油气生产盆地，其主要烃源岩为上侏罗统— Farsund组（与Kimmeridge Clay组相当）的白垩纪最低海相页岩。直接位于萝拉组。本研究通过在时间和空间框架内评估Farsund和Lola组中页岩的原始（反算）原始烃源岩特性（TOCo，S2o，HIo），研究了盆地的原始烃源岩潜力。该研究包括来自丹麦中部格拉本地区的81口井的大约4800个样品。通常，在整个页岩段以不同的采样密度采集用于源岩分析的样品。页岩段被划分为七个单元（称为FSU1到FSU6之前的单元； FSU：Farsund地震单元），它们由可绘制的区域规模地震标志物描绘。对于FSU1之前的设备和FSU2至FSU6的设备，可用样本数范围为608至1145，而FSU1则有433个样本。优质的烃源岩质量随时间和空间而变化，既反映了盆地的结构发展，也反映了晚侏罗纪海侵的影响，主要的厨房区域分布在尾端Graben，Feda Graben，Gertrud Graben和Rosa盆地。页岩的烃源岩质量随时间逐渐增加，并在FSU6中达到最高，其中包括Bo成员的“热页岩”。最大烃源岩质量似乎对应于约675 mg HC / g TOC的原始氢指数（HIo）。在FSU1之前的单位到FSU2（低基米尼第安河-较低的伏安河）单位中，易生油样品的比例（HIo> 350 mg HC / g TOC）在7％至11％之间，在FSU3中增加到18％至22％和FSU4 / FSU5（下沃尔格语-中沃尔格语），在FSU6（上沃尔格语-梁赞语）中最高达到53％。FSU6是最容易生油的烃源岩层段，但是在页岩演替的较老和较深部分存在多生油层段对评估上侏罗统石油系统的产生潜力很重要。