Lower Cretaceous deep-water sandstone plays in the UK Central Graben

Abstract

Up to the present, exploration of the UK Lower Cretaceous deep-water sandstone play has been confined largely to the Moray Firth basins. The Lower Cretaceous of the Central Graben area has been modelled previously as predominantly shale-prone, and hence unattractive to exploration. There is a growing realization that this may not be the case. Since seismic imaging of Lower Cretaceous sandstones is known to be poor whether hydrocarbon-bearing or water-wet, a robust depositional model must be constructed from well and regional geological data in order to predict sandstone distribution and geometry, and hence to aid identification of potential hydrocarbon traps. Of the hundreds of wells drilled in the Central Graben area that targeted deeper Jurassic-Triassic reservoirs, virtually all have been located on the flanks of the graben, or on intra-graben highs. However, 71 of these wells have proved sandstones or traces of sandstone within the Lower Cretaceous, giving grounds for optimism that more substantial deep-water sandstone developments may be present within the graben depocentres. Twenty-six leads have been identified within these depocentres; most of these are located within stratigraphic traps in interpreted detached basin floor fans.

Lower Cretaceous reservoir development in the North Sea Central Graben, and potential analogue settings in the Southern Permian Basin and South Viking Graben

“…In contrast to the UKCG, where numerous wells encounter Lower Cretaceous sandstones (Milton-Worssell et al 2006), only three wells in the NCG area (from a total of 160 Lower Cretaceous penetrations) are reported to contain similar deposits (NPD 2017, Figs. 4b, 6).…”

“…Although the Forties-Montrose High and Marnock Terrace formed barriers that separated the UKCG depocenters from the Moray Firth during the Early Cretaceous ( Fig. 1a), it is possible to extend the Lower Cretaceous Moray Firth reservoir intervals into the UKCG (Milton-Worssell et al 2006) where various wells encounter Lower Cretaceous sands. This well data, in combination with seismically-derived maps, allowed Milton-Worssell et al (2006) to postulate the distribution of (mainly deep marine sandstone) bodies, sourced by the Western Platform, Forties-Montrose High and Jaeren High, for both a Latest Ryazanian-Barremian play and the Aptian-Albian play in the UKCG.…”

“…Boirie & Jeannou 1984;Statoil 1991) and published material (e.g Isaksen & Tonstad 1989 , see table 1). Additional occurrences of Lower Cretaceous sandstones in UKCG wells are adopted from Milton-Worssell et al 2006).…”

“…The sandstones in these wells are lithostratigraphically defined as Ran Sandstone units (NPD 2017) and, in contrast with the deep marine character of most equivalent Lower Cretaceous sandstones in the UK, are interpreted as shallow submarine fans (Isaksen & Tonstad 1989;Milton-Worssell et al 2006).…”

Mesozoic resource potential in the Southern Permian Basin area: the geological key to exploiting remaining hydrocarbons whilst unlocking geothermal potential

“…Steuber et al 2005), led to an evolution from a clastic-dominated succession (marine shorefaces/pelagic mudstones/deepwater sandstones: e.g. Milton-Worssell et al 2006;Jeremiah et al 2010;Vis et al 2018;Zwaan 2018) to chalk-rich seas (including important reservoir units across the region: e.g. van Lochem 2018).…”