Geology and petroleum prospectivity of the Sea of Hebrides Basin and Minch Basin, offshore NW Scotland

Fyfe, Laura‐Jane C.; Schofield, Nicholas; Holford, Simon; Hartley, Adrian J.; Heafford, Adrian; Muirhead, David; Howell, John

doi:10.1144/petgeo2021-003

Cited by 4 publications

(1 citation statement)

References 106 publications

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“…However, within the Irish sector, Carboniferous source rocks have been proven on the eastern flank of the basin (Shannon and Naylor, 2010). The northern extent of these Carboniferous rocks is not clear; onshore, the northernmost extent of Carboniferous rocks along the West Coast of Scotland is seen at Inninmore bay, Morvern, adjacent to the Isle of Mull, comprising of a Westphalian age coal-bearing sequence (Fyfe et al 1993). However, no other known outcrops are present north of this.…”

Section: Source Rocksmentioning

confidence: 99%

Audit of Petroleum Exploration Wells in the UK Rockall Basin: 1980-2006

Schofield¹,

Broadley²,

Jolley³

2019

Preprint

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The UK Rockall Basin is one of the most underexplored areas of the UK Continental Shelf (UKCS) with only 12 exploration wells drilled since 1980, in a basin area that is equal in size to the entire North Sea hydrocarbon province (NNS, CNS & SNS). With only one discovery, made in 2000 (Benbecula South 154/1-1 Gas discovery), the general view of the basin from an exploration viewpoint has not been traditionally positive. The overriding aim of this document is to allow an accessible introduction to the exploration history and hydrocarbon prospectivity of the Rockall region, while at the same time highlighting some of the recent advances in understanding of the basin. Importantly, this report highlights that although the ratio of 1 discovery to 11 dry wells can be interpreted as indicating a basin with little to no viable petroleum system, this statistic is misleading. As of 2019, based on the assessment in this report, we would argue that the discovery to dry hole ratio is closer to 1:6 (rather than 1:11), due to five wells being drilled on invalid geological targets, as a result of lacking subsurface knowledge and/or poor quality seismic data. In addition to this, there is a lack of deep well penetrations with the UK Rockall, with only one well reaching sedimentary strata older then the Cretaceous, meaning that the detailed stratigraphy of the area is still largely unknown.The exploration narrative of the UK Rockall should be placed in context in regard to the rest of the UKCS, where from the years 1965-2007, a total of 22681 exploration wells were drilled (compared against the 12 drilled in the UK Rockall from 1980-2006). Therefore, it must be argued that, as of 2019, not enough subsurface geological information currently exists within the UK Rockall to assess the viability of the petroleum system.

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Section: Source Rocksmentioning

confidence: 99%

Audit of Petroleum Exploration Wells in the UK Rockall Basin: 1980-2006

Schofield¹,

Broadley²,

Jolley³

2019

Preprint

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Concretionary cementation of a Scottish Middle Jurassic sandstone by hot, Paleocene fluids: a clumped isotope study

Paxton

Andrews

Dennis

et al. 2023

JGS

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This study focusses on new clumped isotope data from concretionary calcite cements in the Middle Jurassic Valtos Sandstone Formation (Great Estuarine Group) of the Inner Hebrides. Clumped isotopes show that concretion cementation began at 45±6 °C increasing to temperatures in excess of 70 °C before cooling slightly to 57 ± 7 °C at the concretion margin. In the early stages of cementation, calculated δ 18 O FLUID values were ∼ –12‰ VSMOW, identical to an estimate of Paleocene Hebridean meteoric water based on hydrothermal reactions close to Paleocene Igneous Centres. These δ 18 O FLUID values imply that concretion cementation started in the Paleocene probably during the earliest stages of phreato-magmatic effusive igneous activity. As the concretion grew, temperature changes were accompanied by progressively evolving δ 18 O FLUID compositions up to +2.1 ± 1.1‰ VMOW. These evolving δ 18 O FLUID compositions were caused by isotope exchange reactions between 18 O-rich lithologies and hot basinal fluids migrating upward along faults. This fluid flow was driven by progressive crustal loading from the thickening Paleocene lava pile which also caused sandstone compaction. Published radiometric dates that constrain the emplacement time of the Skye Lava Group, and its subsequent rapid erosion, suggest that concretion formation and final compaction was completed in no more than 2.6 myr, far more rapidly than modelled previously. Initial concretion growth that pre-dates development of volcanic topography shows that the strongly negative compositions of Hebridean Paleocene meteoric water are mainly of latitudinal rather than orographic origin. Supplementary material: Clumped isotope data correction and uncertainties, sample details and additional figures is available at https://doi.org/10.6084/m9.figshare.c.6459860

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Challenges and opportunities for hydrocarbon exploration within the Mesozoic sub-basalt plays of the Norwegian Atlantic Margin

Kilhams

Chedburn

Layfield

et al. 2022

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The sub-basalt domain of the Norwegian continental shelf (NCS) is one of the last remaining hydrocarbon exploration frontiers in Europe. While there is an established geological and tectonic framework, little has been published that addresses the remaining hydrocarbon exploration risks/uncertainties. Unlike the Faroe Shetland Basin and Rockall Trough, at the time of writing, there are currently no industry-drilled sub-basalt well penetrations on the Norwegian continental shelf. Numerous potential Mesozoic sub-basalt hydrocarbon plays exist on the NCS but, due to the lack of industry-drilled sub-basalt penetrations, there is a perceived large exploration risk. By using cross-border analogues, basin modelling workflows and integration of available seismic data the main uncertainties across the NCS are outlined including charge timing, structural definition, and details of reservoir presence. Generically the Late Cretaceous and Middle Jurassic intervals are potential plays which may be present on the Norwegian Margin. However, there is considerable uncertainty on their depth and preservation. Although significant challenges and uncertainties remain, the authors believe that the integration of well results, consideration of basin modelling driven heat flow estimates and new 3D seismic data may open sub-basalt opportunities for a new exploration frontier on the NCS. Thematic collection: This article is part of the New learning from exploration and development in the UKCS Atlantic Margin collection available at: https://www.lyellcollection.org/topic/collections/new-learning-from-exploration-and-development-in-the-ukcs-atlantic-margin

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Geology and petroleum prospectivity of the Sea of Hebrides Basin and Minch Basin, offshore NW Scotland

Cited by 4 publications

References 106 publications

Audit of Petroleum Exploration Wells in the UK Rockall Basin: 1980-2006

Audit of Petroleum Exploration Wells in the UK Rockall Basin: 1980-2006

Concretionary cementation of a Scottish Middle Jurassic sandstone by hot, Paleocene fluids: a clumped isotope study

Challenges and opportunities for hydrocarbon exploration within the Mesozoic sub-basalt plays of the Norwegian Atlantic Margin

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