Abstract
The Sea of Hebrides Basin and Minch Basin are late Palaeozoic-Mesozoic rift basins located to the northwest of the Scottish mainland. The basins were the target of small-scale petroleum exploration from the late 1960s to the early 1990s, with a total of three wells drilled within the two basins between 1989 and 1991. Although no commercially viable petroleum discoveries were made, numerous petroleum shows were identified within both basins, including a gas show within the Upper Glen 1 well in Lower Jurassic limestones. Organic rich shales have been identified throughout the Jurassic succession within the Sea of Hebrides Basin, with one Middle Jurassic (Bajocian-Bathonian) shale exhibiting a Total Organic Carbon content of up to 15 wt%. The focus of this study is to review the historic petroleum exploration within these basins, and to evaluate whether the conclusions drawn in the early 1990s of a lack of prospectivity remains the case. This was undertaken by analysis of seismic reflection data, gravity and aeromagnetic data and sedimentological data, from both onshore and offshore wells, boreholes and previously published studies. The key findings from our study suggest that there is a low probability of commercially sized petroleum accumulations within either the Sea of Hebrides Basin or the Minch Basin. Ineffective source rocks, likely due to low maturities (due to lack of burial) and the fact that the encountered Jurassic and Permian-Triassic reservoirs are of poor quality (low porosity and permeability) has led to our interpretation of future exploration being high risk, with any potential accumulations being small in size. While petroleum accumulations are unlikely within the basin, applying the knowledge obtained from the study could provide additional datasets and insight into petroleum exploration on other northeast Atlantic margin basins, such as the Rockall Trough and the Faroe-Shetland Basin.
| Original language | English |
|---|---|
| Article number | petgeo2021-003 |
| Number of pages | 37 |
| Journal | Petroleum Geoscience |
| Volume | 27 |
| Issue number | 4 |
| Early online date | 19 May 2021 |
| DOIs | |
| Publication status | Published - Nov 2021 |
Bibliographical note
Funding: This work was funded by the Natural Environment Research Council (RG12649-12).Acknowledgements: The work contained in this paper contains work conducted during a PhD study undertaken as part of the Natural Environment Research Council (NERC) Centre for Doctoral Training (CDT) in Oil and Gas. We are also grateful to IHS Markit for provision of, and permission to publish examples from, their 2D seismic data volumes and gravity and magnetics database, and to Schlumberger for their donation of Petrel seismic interpretation software licences
to Aberdeen University. We also thank Geognostics for the kind permission to use the Frogtech Geoscience, 2016 depth to basement map (SEEBASE) of offshore northwest Scotland. We acknowledge the UKOilandGasData.com website, owned by UK National Data Repository administered by Schlumberger, for access to the seismic data volumes and released UK well database. We are also grateful to the UK National Onshore Data Library who kindly provided
seismic data (UKOGL request 100891 and 100890) to the University of Aberdeen. Dr. Iain Scotchman and Dr. Clayton Grove are thanked for constructive and helpful reviews, which have improved this paper. Laura-Jane would also like to personally thank the late Professor Bernard Owens, who passed away in July 2019, for his informative discussion on Carboniferous outliers along the west coast early on in her PhD. The views held within this paper do not necessarily represent the views of IHS Markit.