The application of sequence stratigraphy to the understanding of Late Jurassic turbidite plays in the Central North Sea, UKCS

Carruthers, Alan; McKie, Tom; Price, J. D.; Dyer, R.; Williams, G.; Watson, Paul

doi:10.1144/gsl.sp.1996.114.01.02

Cited by 22 publications

(13 citation statements)

References 12 publications

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“…11). These stacking patterns, which are also reported from other Upper Jurassic North Sea sequences (Carruthers et al 1996;Veldkamp et al 1996), are indicative of deposition within an extensional transgressive regime.…”

Section: Stacking Patterns and Discontinuitiessupporting

confidence: 81%

Fulmar: a mature field revisited

Spaak¹,

Almond²,

Salahudin³

et al. 1999

PGC

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The original STOIIP of the Fulmar Field is currently estimated as 853 x 10 6 STB and it is considered that approximately 540 x 10 6 STB of oil has so far been produced, representing 63.4% of the original reserves. This high recovery factor coupled with an increasingly high water-cut (currently averaging 90%) suggests that the end of field life is drawing close. Prior to making an abandonment decision however it was considered prudent to review and update both the geological and dynamic reservoir models in order to ensure that the full field potential has been realized before making provisions for abandonment. In this context, the depositional model and stratigraphic architecture of the Upper Jurassic Fulmar Sands have been reviewed. Two geological models have been considered: (1) the preexisting model; and (2) an alternative model, which reflects continuing uncertainties in the field's stratigraphic architecture.The main part of the Fulmar reservoir consists of a stacked sequence of shoreface sediments that were deposited within an extensional, back-stepping shallow marine setting. This sequence is punctuated by several minor flooding events, which are characterized by distal, poorer quality shoreface sediments. The latter deposits locally form small, but distinct, pressure and flow discontinuities in the reservoir. These heterogeneities were captured in detail, in a 3D geological model and input into the full field reservoir simulation using the Shell proprietary GEOCAP/MoReS software. The history match of the dynamic reservoir model predicted that by-passed oil could be locally trapped below these flooding events. This concept was confirmed in mid 1997 by two wells drilled on the crest of the field. The simulation model also indicates that a significant volume of potentially unswept oil may be present on the NE flank of Fulmar within the poorer reservoir quality, lower shoreface 'Clyde sands'. This concept will be tested by drilling a horizontal well into these sands in the mid part of 1998. As the architecture of the alternative geological model showed some differences to the pre-existing field geological model, particularly in the down flank areas, this model was also input into the GEOCAP simulation in order to compare and test the reliability of the simulation predictions. Only minimal differences were observed between the two simulation models, which reflects the dominantly high net: gross (N: G) in the main producing western part of the field and the similarity of the correlations in the crestal and eastern parts of the field.Both similation models show a significant improvement in the history match, which highlights the potential benefits to be gained by constructing detailed 3D reservoir models that better describe the architecture of the flow units and barriers in the reservoir than more 'traditional' layer-based (CPS-3) models. These studies are helping to maximize recovery from this highquality, strongly depleted reservoir.This paper primarily presents a review of the stratigraphic architecture model...

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Section: Stacking Patterns and Discontinuitiessupporting

confidence: 81%

Fulmar: a mature field revisited

Spaak¹,

Almond²,

Salahudin³

et al. 1999

PGC

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“…All sands are of very limited lateral extent and occur in the vicinity of the Buchan Horst with its outcrop of Early Carboniferous and Devonian sandstones, which is the most likely source. Several authors date this unit in Well 20/5b-2 as Callovian to Early Oxfordian (Carruthers et al 1996;Davies et al 1996;Harker & Rieuf 1996;Stephen & Davies 1998). However, although dinocysts of this age have been reported in one out of three contractor biostratigraphy reports prepared for this well (Davies et al 1996, fig.…”

Section: Uj4 (Polonicum) Sequencementioning

confidence: 99%

“…Regional treatments of the Humber Group are given by Turner et al (1984), Andrews & Brown (1987), Boldy & Brealey (1990), Boote & Gustav (1987), Hallsworth et al (1996, 1993, O'Driscoll et al (1990) and Richards et al (1993). A sequence stratigraphic approach has been taken in more recent studies including Harker & Rieuf (1996), Carruthers et al (1996), Davies et al 1996, Stephen & Davies 1998, Davies et al (1999. Previously published palaeogeographical maps put the OMF into a more regional context (Rattey & Hayward 1993;Harker & Rieuf 1996).…”

Section: Data Usedmentioning

confidence: 99%

Sequence stratigraphy and sedimentary history of the Humber Group (Late Jurassic-Ryazanian) in the Outer Moray Firth (UKCS, North Sea)

Kadolsky¹,

Johansen²,

Duxbury³

1999

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The Humber Group in the Outer Moray Firth is an onlapping sedimentary succession of Late Oxfordian to Ryazanian age, recording a trend of continuously rising relative sea-level. Nineteen subordinate transgressive-regressive cycles ('sequences') have been identified in the numerous wells in the area. The identification of these sedimentary units throughout the study area is indispensable for the interpretation of its sedimentary history, and hence for the ability to predict the possibility of subtle stratigraphic traps. Transgression began during the Late Oxfordian in the North Buchan Graben and culminated in the Early Ryazanian, when only parts of the Halibut Horst and the Fladen Ground Spur remained exposed. Mapping of the onlap reveals the drowning from the south of a significant topographic relief, which was further enhanced by syndepositional rifting. Three structural grains affected sedimentation: (1) E-W (possibly a repeated reactivation of pre-Late Jurassic faults, e.g. North Halibut Graben: pre-Late Oxfordian to Middle Volgian); (2) NE-SW (e.g. Theta Graben: Late Oxfordian to Early Kimmeridgian; Highlander-Piper Ridge: Kimmeridgian to Mid-Volgian); (3) NW-SE (e.g. Witch Ground Graben: Early Volgian to Ryazanian). Sedimentation was initially dominated by coastal plain and shoreface facies of marine-dominated deltas and estuaries (Piper Formation s.l.), sourced mainly from the Fladen Ground Spur. From deposition of the upper Piper Formation onwards, intra-rift horsts, particularly the Halibut Horst, were also important sand sources. Deltaic systems back-stepped toward the basin flanks when accommodation space generation began to exceed sediment supply. Increased rifting in Early Volgian times triggered large-scale mass flow deposition from the Halibut Horst and from the East Piper High. Back-stepping shoreface systems continued their progressive onlap of the basin margins. Lowstand systems tracts in the individual sequences were muted by the overpowering long-term transgression, and significant mass flow deposits were not primarily controlled by the collapse of constructional highstand shelf margins. Instead, long-term tectonic uplift of specific areas sourced basinmargin submarine fan systems, typically confined to half graben on the flanks of the basin (e.g. Claymore sands), and basin-floor submarine channel systems in the core of the Witch Ground Graben (e.g. Galley sands). The potential for subtle stratigraphic traps is greatest in these turbiditic sandbodies where their boundaries are abrupt, as a result of channeling in self-constructed levees, or confinement by fault-induced seafloor topography.

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“…In this part of the WCS, progressive coastal onlap culminates in the widely documented eudoxus mfs sea-level maximum, which occurs throughout the Central North Sea (e.g. Donovan et al 1993;Milton 1993;Partington et al 19936;Underhill & Partington 1993;Carruthers et al 1996;Davies et al 1996;Harker & Rieuf 1996).…”

Section: Stratigraphic Frameworkmentioning

confidence: 99%

Controls on Upper Jurassic sediment distribution in the Durward–Dauntless area, UK Blocks 21/11, 21/16

Stewart

Fraser

Cartwright

et al. 1999

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The Upper Jurassic shallow marine Fulmar sands are widespread in the West Central Graben but have an increasingly irregular distribution when traced westwards across the West Central Shelf (Western Platform). This is strikingly illustrated in the Durward and Dauntless fields (Blocks 21/11 and 21/16), located 20 km west of Kittiwake, where several exploration, appraisal and development wells failed to find the Fulmar sands objective. The main aim of this paper is to offer an explanation for this irregular sand distribution in the Durward/Dauntless area.This study represents an integrated analysis of the thin (50-250 ft) Upper Jurassic succession (equivalent to the Fulmar and Kimmeridge Clay formations) based on around 90 wells and a sub-regional 3D seismic dataset, which covers most of the West Central Shelf. A combination of sedimentological, biostratigraphical and well log criteria has been used to define up to nine genetic depositional sequences bounded by regionally correctable maximum flooding surfaces. This stratigraphic framework provides a linkage between the previously unpublished Durward-Dauntless area and the Kittiwake Field. Typical 'Fulmar sands' facies are restricted to the Kimmeridgian in this area and occur in up to five depositional sequences, which extend from the Base Jurassic unconformity (earliest Kimmeridgian) up to the eudoxus and autissiodorensis maximum flooding surfaces (mfs) (latest Kimmeridgian). These sequences display marked lateral facies changes from sand to mud, while stratal patterns and thickness variations indicate onlap against earlier deposits. This is in striking contrast to the younger mud-dominated depositional sequences (Volgian to Ryazanian), which display complex local subsidence patterns bearing little relationship to Fulmar sand isopach patterns within the Kimmeridgian.The 3D seismic data have enabled mapping of the Base Cretaceous, Top Zechstein Salt and Top Basement (pre-Zechstein), but is unable to directly resolve the thin Upper Jurassic interval. However, these data have enabled a regional structural/stratigraphic model to be developed, particularly in relation to the effects of the nature and rate of accommodation space creation. Conclusions derived from the 3D seismic interpretations have been integrated with those from the well-based sequence stratigraphic studies. The resulting geological model for the Upper Jurassic concludes that Fulmar sand distribution was largely controlled by pre-existing topography, which had evolved during a significant period of (late Triassic-pre Upper Jurassic) subaerial exposure. This topography was critical in controlling highstand sand distribution and its ultimate preservation potential. The importance of pre-Upper Jurassic topography in determining accommodation space became secondary to dissolution of the Zechstein during the suspension-dominated sedimentation of the Volgian and Lower Cretaceous. These local controls vary on a kilometre scale and are superimposed upon the longer wavelength control of regional eastwards dip, wh...

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The application of sequence stratigraphy to the understanding of Late Jurassic turbidite plays in the Central North Sea, UKCS

Cited by 22 publications

References 12 publications

Fulmar: a mature field revisited

Fulmar: a mature field revisited

Sequence stratigraphy and sedimentary history of the Humber Group (Late Jurassic-Ryazanian) in the Outer Moray Firth (UKCS, North Sea)

Controls on Upper Jurassic sediment distribution in the Durward–Dauntless area, UK Blocks 21/11, 21/16

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