The role of organic carbon in the Southern Uplands-Down-Longford Terrane accretionary prism, Scotland and Ireland

IF 1.9 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Petroleum Geoscience Pub Date : 2023-06-29 DOI:10.1144/petgeo2022-059

J. Parnell, J. Armstrong, N. Blamey, A. Boyce, A. Schito, D. Muirhead

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Abstract

Carbonaceous shales in the Southern Uplands-Down-Longford Terrane accretionary prism had extremely high potential for hydrocarbon generation in the Lower Paleozoic. Structural thickening in the prism enhanced the rapid generation of oil. Shale horizons are separated by thick turbidites composed of low-permeability greywackes, so oil under high fluid pressure either pooled along shale bedding surfaces or migrated into fractured greywackes. Pooled oil became solidified to bitumen, which locally formed deposits on a scale of tonnes, mined as coal. The carbon-rich shale also sequestered large amounts of sulfur from seawater, which precipitated as pyrite firstly during early diagenesis, then further during fluid flow through the shale beds. The oil was also sulfur-bearing. Deformation focused on the shale beds during the evolution of the accretionary prism would have been closely related to the fluid flow which precipitated bitumen and sulfides. The palaeo-fluids were also anomalously rich in methane and hydrogen, similar to fluids venting from modern accretionary prisms. Supplementary material: details of localities searched for coal in Lower Palaeozoic, Southern Uplands-Down-Longford Terrane (locations shown in Fig. 6 ) are available at https://doi.org/10.6084/m9.figshare.c.6691597

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有机碳在苏格兰和爱尔兰南部高地-下朗福德地体增生三棱镜中的作用

下古生界南高地-下朗福德地体三棱镜区碳质页岩具有极高的生烃潜力。棱柱的结构增厚促进了油的快速生成。页岩层被由低渗透灰岩组成的厚浊积岩隔开，因此高流体压力下的石油要么沿着页岩层理面聚集，要么运移到裂缝状灰岩中。聚集在一起的石油凝固成沥青，在当地形成了以吨为规模的沉积物，作为煤炭开采。富碳页岩还从海水中吸收了大量的硫，这些硫首先在早期成岩作用中以黄铁矿的形式沉淀下来，然后在流体流过页岩床时进一步沉淀。石油也含硫。在吸积棱柱演化过程中，集中在页岩床上的变形可能与沉积沥青和硫化物的流体流动密切相关。古流体也异常富含甲烷和氢，类似于现代增生棱镜排出的流体。补充资料:下古生代，南高地-下朗福德地体(图6所示位置)寻找煤的详细位置可在https://doi.org/10.6084/m9.figshare.c.6691597上获得

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来源期刊

Petroleum Geoscience 地学-地球科学综合

CiteScore

4.80

自引率

11.80%

发文量

审稿时长

>12 weeks

期刊介绍： Petroleum Geoscience is the international journal of geoenergy and applied earth science, and is co-owned by the Geological Society of London and the European Association of Geoscientists and Engineers (EAGE). Petroleum Geoscience transcends disciplinary boundaries and publishes a balanced mix of articles covering exploration, exploitation, appraisal, development and enhancement of sub-surface hydrocarbon resources and carbon repositories. The integration of disciplines in an applied context, whether for fluid production, carbon storage or related geoenergy applications, is a particular strength of the journal. Articles on enhancing exploration efficiency, lowering technological and environmental risk, and improving hydrocarbon recovery communicate the latest developments in sub-surface geoscience to a wide readership. Petroleum Geoscience provides a multidisciplinary forum for those engaged in the science and technology of the rock-related sub-surface disciplines. The journal reaches some 8000 individual subscribers, and a further 1100 institutional subscriptions provide global access to readers including geologists, geophysicists, petroleum and reservoir engineers, petrophysicists and geochemists in both academia and industry. The journal aims to share knowledge of reservoir geoscience and to reflect the international nature of its development.