Sub-volcanic play in the Central North Sea?

Sub-volcanic play in the Central North Sea?

According to researchers from the University of Aberdeen there is potential for an oil and gas play under the Rattray Volcanics in the UK Central North Sea.

Researchers from the University of Aberdeen have revisited the seismic data and wells in the area of the Rattray Volcanics in the central North Sea and concluded there is the possibility of a sub-volcanic play.

The original objective of the study on Rattray volcanics was to investigate the edge of the lava field and to try and identify the major intra-basaltic and supra-basaltic drainage systems, and any potential ‘Rosebank type’ intra-basaltic play fairway. The Rosebank Field was discovered in 2004 within the Palaeocene–Eocene lavas of the Faroe-Shetland Basin. The reservoir intervals are unusual in that they are a series of intra-basaltic fluvial clastic sequences, separated by basalt lava flows, hyaloclastite and volcaniclastic sediments (Read also “Equinor majority owner”.

The outcome of the research project however suggests a very different type of sub-volcanic play to be present under the Rattray volcanics (Quirie et al., 2018). The Middle Jurassic Rattray Volcanic Province is located at the triple junction of the North Sea continental rift system. Previously it was thought to be sourced from three large central volcanoes: the Glenn, Fisher Bank and Ivanhoe volcanic centres. Quirie et al. state now that no such volcanic centres are present, and the Rattray Volcanics were in fact fissure eruptions from linear vents. The orientation of the fissures is broadly parallel to the Highland Boundary Fault implying that Mid-Jurassic magmatism used pre-existing crustal structural anisotropies established during the Caledonian Orogeny.

The lack of large intrusive complexes beneath the Rattray Volcanics indicates that the pre-Middle Jurassic sedimentary sequences (e.g. the Devonian–Carboniferous Old Red Sandstone Group, the Permian Rotliegend and Zechstein groups and the Triassic Skagerrak Formation) are present under the volcanics. Therefore, the subvolcanic reservoir and source rock units within the triple junction of the Central North Sea might be worth looking into.

A cross-section of the Rattray Volcanic Province old and revised model with lava fissures (Credit: University of Aberdeen)

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