Three-dimensional seismic characterisation of large-scale sandstone intrusions in the lower Palaeogene of the North Sea

completely injected vs. in situ remobilised sandbodies

Ewa Szarawarska, Mads Huuse, Andrew Hurst, Wytze De Boer, Liwei Lu, Steven Molyneux, Peter Rawlinson

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

A large number of km-scale, saucer-shaped sandstone bodies of enigmatic origin have recently been documented in the North Sea and the Faroe Shetland Basin. This study utilises three-dimensional seismic data, calibrated by well data, to examine two such bodies that exhibit very similar saucer-shaped geometries in cross-section. The Volund and Danica structures, located 250 km apart are interpreted as end members of a spectrum of large-scale remobilised and injected sandstones present in the North Sea Palaeogene. Both are characterised by a central 1–2 km-wide low area surrounded by a discordant, 2–300 m tall inclined dyke complex, that tips out into a bedding concordant body interpreted as a shallow-level sill and/or partly extruded sandstone. The origin of the central concordant sandstone body as either injected (laccolith) or depositional is of key importance to a complete understanding of the origin and prospectivity of these structures. The key criteria for recognising an injected vs. depositional origin for the central concordant sandbody are: (1) a flat, nonerosional base; (2) ‘jack-up’ of the overburden equal to the underlying sand thickness; (3) equally thick layers of encasing mudstones; and (4) paleogeographic context. This study suggests that the Danica structure was deposited as a channel sandstone and remobilised in situ; this led to the formation of wing-like intrusions along the channel margins. In contrast, the Volund structure overburden displays a forced-fold geometry, arguably a diagnostic feature of an intrusive origin. The ability to recognise and differentiate completely injected vs. in situ remobilised sandbodies is important both from a basin analysis, hydrocarbon exploration and rock mechanics points of view. An improved understanding of these aspects will lead to a reduction of risks associated with the exploration and development of such a sandbody and an enhanced understanding of sediment remobilisation and fluid flow on a basin scale.
Original languageEnglish
Pages (from-to)517-532
Number of pages16
JournalBasin Research
Volume22
Issue number4
Early online date1 Apr 2010
DOIs
Publication statusPublished - Aug 2010

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Paleogene
sandstone
overburden
laccolith
basin analysis
geometry
hydrocarbon exploration
rock mechanics
remobilization
basin
sill
mudstone
fluid flow
dike
seismic data
cross section
in situ
sea
fold
sand

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Three-dimensional seismic characterisation of large-scale sandstone intrusions in the lower Palaeogene of the North Sea : completely injected vs. in situ remobilised sandbodies. / Szarawarska, Ewa; Huuse, Mads; Hurst, Andrew; De Boer, Wytze; Lu, Liwei; Molyneux, Steven; Rawlinson, Peter.

In: Basin Research, Vol. 22, No. 4, 08.2010, p. 517-532.

Research output: Contribution to journalArticle

Szarawarska, Ewa ; Huuse, Mads ; Hurst, Andrew ; De Boer, Wytze ; Lu, Liwei ; Molyneux, Steven ; Rawlinson, Peter. / Three-dimensional seismic characterisation of large-scale sandstone intrusions in the lower Palaeogene of the North Sea : completely injected vs. in situ remobilised sandbodies. In: Basin Research. 2010 ; Vol. 22, No. 4. pp. 517-532.
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abstract = "A large number of km-scale, saucer-shaped sandstone bodies of enigmatic origin have recently been documented in the North Sea and the Faroe Shetland Basin. This study utilises three-dimensional seismic data, calibrated by well data, to examine two such bodies that exhibit very similar saucer-shaped geometries in cross-section. The Volund and Danica structures, located 250 km apart are interpreted as end members of a spectrum of large-scale remobilised and injected sandstones present in the North Sea Palaeogene. Both are characterised by a central 1–2 km-wide low area surrounded by a discordant, 2–300 m tall inclined dyke complex, that tips out into a bedding concordant body interpreted as a shallow-level sill and/or partly extruded sandstone. The origin of the central concordant sandstone body as either injected (laccolith) or depositional is of key importance to a complete understanding of the origin and prospectivity of these structures. The key criteria for recognising an injected vs. depositional origin for the central concordant sandbody are: (1) a flat, nonerosional base; (2) ‘jack-up’ of the overburden equal to the underlying sand thickness; (3) equally thick layers of encasing mudstones; and (4) paleogeographic context. This study suggests that the Danica structure was deposited as a channel sandstone and remobilised in situ; this led to the formation of wing-like intrusions along the channel margins. In contrast, the Volund structure overburden displays a forced-fold geometry, arguably a diagnostic feature of an intrusive origin. The ability to recognise and differentiate completely injected vs. in situ remobilised sandbodies is important both from a basin analysis, hydrocarbon exploration and rock mechanics points of view. An improved understanding of these aspects will lead to a reduction of risks associated with the exploration and development of such a sandbody and an enhanced understanding of sediment remobilisation and fluid flow on a basin scale.",
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AU - Rawlinson, Peter

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N2 - A large number of km-scale, saucer-shaped sandstone bodies of enigmatic origin have recently been documented in the North Sea and the Faroe Shetland Basin. This study utilises three-dimensional seismic data, calibrated by well data, to examine two such bodies that exhibit very similar saucer-shaped geometries in cross-section. The Volund and Danica structures, located 250 km apart are interpreted as end members of a spectrum of large-scale remobilised and injected sandstones present in the North Sea Palaeogene. Both are characterised by a central 1–2 km-wide low area surrounded by a discordant, 2–300 m tall inclined dyke complex, that tips out into a bedding concordant body interpreted as a shallow-level sill and/or partly extruded sandstone. The origin of the central concordant sandstone body as either injected (laccolith) or depositional is of key importance to a complete understanding of the origin and prospectivity of these structures. The key criteria for recognising an injected vs. depositional origin for the central concordant sandbody are: (1) a flat, nonerosional base; (2) ‘jack-up’ of the overburden equal to the underlying sand thickness; (3) equally thick layers of encasing mudstones; and (4) paleogeographic context. This study suggests that the Danica structure was deposited as a channel sandstone and remobilised in situ; this led to the formation of wing-like intrusions along the channel margins. In contrast, the Volund structure overburden displays a forced-fold geometry, arguably a diagnostic feature of an intrusive origin. The ability to recognise and differentiate completely injected vs. in situ remobilised sandbodies is important both from a basin analysis, hydrocarbon exploration and rock mechanics points of view. An improved understanding of these aspects will lead to a reduction of risks associated with the exploration and development of such a sandbody and an enhanced understanding of sediment remobilisation and fluid flow on a basin scale.

AB - A large number of km-scale, saucer-shaped sandstone bodies of enigmatic origin have recently been documented in the North Sea and the Faroe Shetland Basin. This study utilises three-dimensional seismic data, calibrated by well data, to examine two such bodies that exhibit very similar saucer-shaped geometries in cross-section. The Volund and Danica structures, located 250 km apart are interpreted as end members of a spectrum of large-scale remobilised and injected sandstones present in the North Sea Palaeogene. Both are characterised by a central 1–2 km-wide low area surrounded by a discordant, 2–300 m tall inclined dyke complex, that tips out into a bedding concordant body interpreted as a shallow-level sill and/or partly extruded sandstone. The origin of the central concordant sandstone body as either injected (laccolith) or depositional is of key importance to a complete understanding of the origin and prospectivity of these structures. The key criteria for recognising an injected vs. depositional origin for the central concordant sandbody are: (1) a flat, nonerosional base; (2) ‘jack-up’ of the overburden equal to the underlying sand thickness; (3) equally thick layers of encasing mudstones; and (4) paleogeographic context. This study suggests that the Danica structure was deposited as a channel sandstone and remobilised in situ; this led to the formation of wing-like intrusions along the channel margins. In contrast, the Volund structure overburden displays a forced-fold geometry, arguably a diagnostic feature of an intrusive origin. The ability to recognise and differentiate completely injected vs. in situ remobilised sandbodies is important both from a basin analysis, hydrocarbon exploration and rock mechanics points of view. An improved understanding of these aspects will lead to a reduction of risks associated with the exploration and development of such a sandbody and an enhanced understanding of sediment remobilisation and fluid flow on a basin scale.

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