bluuebunny/crossref_metadata_2025 huggingface dataset:
The Murchison Field, Block 211/19a, UK North Sea
Authors: Warrender John
Published: April 2008

The Murchison oil field forms part of the Brent oil province in the East Shetland Basin, northern North Sea. The field, which straddles the UK-Norway international boundary, was discovered in 1975 and began production with Conoco (UK) Ltd as Operator, in 1980. Like many oil accumulations in the East Shetland Basin the trap consists of a northwesterly dipping rotated fault block of Jurassic-Triassic age sourced and sealed by unconformable Upper Jurassic shales. The productive reservoir consists of Middle Jurassic Brent Group sandstones which represent the south to north progradation of a wave/tide influenced delta system. The Brent Group on Murchison has an average thickness of 425 ft with average porosities of 22% and permeabilities in the 500-1000 md range in producing zones. The maximum hydrocarbon column thickness is approximately 600 ft. The oil is undersaturated and no gas cap is present. Recoverable reserves are 340 MMBBL from a total oil in place figure of 790 MMBBL. Oil production which is via a single steel jacket platform peaked at 127 000 BOPD in 1983 and currently averages 45 000 BOPD. Economic field life is expected to be at least 20 years.

The Murchison Field is located in the East Shetland Basin, northern North Sea at approximate latitude 61° 23' N, longitude 1° 43.5' E, 120 miles northeast of the Shetland Islands (Fig. 1). The field straddles the UK-Norway international boundary with the greater portion in the UK Block 21 l/19a and the lesser portion in Norway Block 33/9. Water depth is -512 ft BMSL. In the context of the North Sea the field is of medium size with an areal closure of approximately 7 square miles and contains 790 million barrels of oil in place. The productive reservoir consists of coastal deltaic sandstones of the Middle Jurassic Brent Group which lie between the marine shales of the Lower Jurassic Dunlin Group and the marine, organic-rich shales of the Upper Jurassic Humber Group. The trap is structural comprising a single, northwesterly dipping rotated fault block which has been sourced and sealed by the overlying Upper Jurassic shales. The field is named after the Scottish geologist Sir Roderick Impey Murchison (1792-1871), who is best known for his contribution to Palaeozoic stratigraphy.
The Cyrus Field, Block 16/28, UK North Sea
Authors: Mound D. G. , Robertson I. D. , Wallis R. J.
Published: April 2008

The Cyrus Oilfield is located in Block 16/28 of the UK sector of the North Sea approximately 250 km (155 miles) NE of Aberdeen and 55 km (34 miles) NE of the Forties Field. The trap consists of a broad, very low relief four-way dip closure developed over a deeper tilted fault block. The reservoir consists of submarine-fan sandstones of late Palaeocene age, belonging to the Andrew Formation. Provenance was to the NW resulting from the early Tertiary sea-level fall which exposed the East Shetland Platform. The reservoir has been sub-divided into two zones, an upper zone of interbedded sandstones and mudstones with net to gross ratios of 0.4 to 0.6 and sandstone porositites of 12% to 18%, and a lower zone of massive fine-grained sandstones plus subordinate thin shales and limestones, with net to gross ratios in excess of 0.9 and porosities averaging 20%. The reservoir is filled with undersaturated oil of 35° API and is normally pressured. The estimate of initial oil-in-place is 75 MMBBL. Development of the field is centred on the use of BP's SWOPS (Single Well Offshore Production System) vessel using two horizontal field development wells which feed into a single seabed template for offtake. Ultimate recovery from the field is estimated to be approximately 12 MMBBL.
The Petronella Field, Block 14/20b, UK North Sea
Authors: Waddams P. , Clark N. M.
Published: April 2008

Petronella Field is a small oil and gas accumulation located 110 miles northeast of Aberdeen in UK Block 14/20b. The field lies on the highest part of the east-west-trending Petronella Ridge approximately 6 miles southwest of the Witch Ground Graben axis. The reservoir is Upper Jurassic in age and lies some 7500 ft below sea level. It comprises shallow marine sandstone of the Piper Formation ('Principal Reservoir Sequence') overlain by deeper marine turbidites ('Hot Lens Equivalent') of the Kimmeridge Clay Formation. The structure is a tilted fault block which is bounded to the north by a major fault system, downthrown to the north. Sandstone units dip to the south and thin or are truncated to the north as a result of erosion of the crest of the structure. Seal is effected by Upper Jurassic siltstone and Lower Cretaceous calcareous claystone. The accumulation has been sourced from maturation of the Kimmeridge Clay Formation below approximately 10000 ft in adjacent basins. The Field was discovered in February 1975 and is delineated by six wells. Current production of 13 000 BOPD comes from one well and uses an innovative remote subsea system controlled from, and with pipelines to, the Tartan Platform 6.4 miles to the east. Ultimate recoverable reserves from the main portion of the Field are 17 MMBBL of crude oil.
The Amethyst Field, Blocks 47/8a, 47/9a, 47/13a, 47/14a, 47,15a, UK North Sea
Authors: Garland C. R.
Published: April 2008

The Amethyst gas field was discovered in 1970 by well 47/13-1. Subsequently it was appraised and delineated by 17 wells. It consists of at least five accumulations with modest vertical relief, the reservoir being thin aeolian and fluviatile sandstones of the Lower Leman Sandstone Formation. Reservoir quality varies from poor to good, high production rates being attained from the aeolian sandstones. Seismic interpretation has involved, in addition to conventional methods, the mapping of several seismic parameters, and a geological model for the velocity distribution in overlying strata.

Gas in place is currently estimated at 1100 BCF, with recoverable reserves of 844 BCF. The phased development plan envisages 20 development wells drilled from four platforms, and first gas from the 'A' platforms was delivered in October 1990. A unitization agreement is in force between the nine partners, with a technical redetermination of equity scheduled to commence in 1991.
The Barque Field, Blocks 48/13a, 48/14, UK North Sea
Authors: Farmer R. T. , Hillier A. P.
Published: April 2008

The Barque Field is associated with some of the earliest gas discoveries in the southern North Sea. In the Sole Pit area the reservoir, the Rotliegend Group Leman Sandstone Formation of Lower Permian age, occurs between Carboniferous Coal Measures, which source the gas, and Zechstein evaporites which form an excellent seal. Primarily aeolian, the sandstone has very low permeability resulting from deep burial of the Sole Pit Trough. The deepest burial and hence the maximum diagenetic damage to the reservoir was achieved in the early Late Cretaceous prior to the two-fold main phases of inversion in Late Cretaceous and Mid-Tertiary.

Compaction and diagenesis reduced reservoir permeability to such an extent that parts of the field would be non-productive were it not for the presence of effective natural fracture zones and well stimulation by hydraulic fracturing techniques. Though appraisal and evaluation have been relatively extensive, remaining uncertainties dictate a conservative development in conjunction with the adjacent Clipper Field. A selected initial area was developed for first gas in October 1990. Good reservoir performance may lead to later development of the whole field.
The Esmond, Forbes and Gordon Fields, Blocks 43/8a, 43/13a, 43/15a, 43/20a, UK North Sea
Authors: Ketter F. J.
Published: April 2008

The three separate fields, Esmond, Forbes and Gordon form the Esmond Gas Complex in Quadrant 43 in the UK Southern North Sea. The Bunter Sandstone Formation is the reservoir in each of the separate, seismically defined, simple, anticlinal structures. The Bunter Sandstone correlates well across the three structures and is composed of a 400-500 ft thick interval containing individual channel sandstones deposited in an arid environment on an alluvial fan. Porosity and permeability are controlled by original texture and by subsequent diagenesis. Reservoir communication within the Bunter reservoir is good though locally tortuous.

First gas production started in July 1985. Four offshore installations have allowed gas to be produced at full contract (plateau) rates of 200 MMSCFD without major interruption. Ultimate sales gas reserves are approximately 530 BCF.
Ravenspurn South Field, Blocks 42/29, 42/30, 43/26, UK North Sea
Authors: Heinrich R. D.
Published: April 2008

The Ravenspurn South Gas Field is located in the Sole Pit Basin of the Southern North Sea in UKCS Block 42/30, extending into Blocks 42/29 and 43/26. The gas is trapped in sandstones of the Permian Lower Leman Sandstone Formation, which was deposited by aeolian and fluvial processes in a desert environment. Reservoir quality is poor, and variations are mostly facies-controlled. The best reservoir quality occurs in aeolian sands wth porosities of up to 23% and permeabilities up to 90 md. The trap is a NW-SE-striking faulted anticline: top seal is provided by the Silverpit Shales directly overlying the reservoir, and by Zechstein halites. Field development began early in 1988 and first gas was delivered in October 1989. Production is in tandem with the Cleeton Field, about 5 miles southwest of Ravenspurn South, as the Villages project. Initial reserves are 700 BCF and field life is expected to be 20 years.
Unravelling dates through the ages: geochronology of the Scottish metamorphic complexes
Authors: Rogers G. , Pankhurst R.J.
Published: April 2008

The paper by Giletti
et al.
(1961) is seen as a major landmark in the evolution of dating techniques in polymetamorphic terrains. We consider certain critical issues from each of the main complexes of the Scottish Highlands studied by Giletti et al. to illustrate how subsequent developments in geochronological methodology have influenced our understanding of metamorphic belts. Lewisian examples focus on the formation of Archaean crust, and the age of the main high-grade metamorphism and the Scourie dyke swarm. The antiquity of Moinian sedimentation, its relationship to the Torridonian sandstones, and the timing of Precambrian metamorphism have been controversial issues. The timing and nature of Caledonian orogenesis, most clearly expressed in the Dalradian complex, have been the focal points for the refinement of radiometric investigation. These complexes have been subject to successive developments in methodology, with ever-tighter constraints from Rb-Sr and K-Ar mineral dating, through Rb-Sr and Pb-Pb whole-rock studies, U-Pb dating of bulk zircon fractions, and Sm-Nd whole-rock and mineral investigation, up to the latest technologies of single-grain zircon and ion microprobe analysis. The rocks have released their secrets reluctantly, and many of the questions posed in 1961 have still not been definitively answered. However, the hope of unambiguous solution leads towards greater efforts, ever more reliable data, and a clearer evolutionary picture.
The Lofoten Drift, Norwegian Sea
Authors: Laberg Jan Sverre , Vorren Tore O. , Knutsen Stig-Morten
Published: April 2008

The Lofoten Contourite Drift is located below

c

. 1000 m water depth on the continental slope off northern Norway. It has a maximum thickness of about 360 m and correlation to published seismic stratigraphy implies a Neogene age. The drift probably originated from the deposition of suspended sediments derived from winnowing of the shelf and upper slope. The geometry of the uppermost part of the drift is characterised by maximum thickness at the mound crest, which implies that it is probably presently active. Within gravity core JM97-950/1 (1160 m water depth), the upper 86 cm represents sediments resulting from Holocene winnowing of the shelf and upper slope. The underlying sediments, to 5.5 m core depth, were deposited in a late Weichselian glacimarine environment as revealed by its content of ice-rafted debris and the dating results. Late Weichselian drift growth is consistent with a circulation system transporting surface water northeastward along the continental margin of Norway also during the Weichselian. The downslope sediment input to the study area was probably relatively low during glacial periods due to the evolution of the nearby mainland area, the Lofoten Islands. These islands may have acted as a sediment barrier causing large fluvial and/or glacial drainage systems from central Fennoscandia to be routed south and north of the study area. As a result, alongslope sediment transport has provided the main sediment input to this part of the continental slope.
Muddy contourites in the Baltic Sea: an example of a shallow-water contourite system
Authors: Sivkov Vadim , Gorbatskiy Vladimir , Kuleshov Alexey , Zhurov Yury
Published: April 2008

Bottom currents in the Baltic Sea have had a pronounced effect on the nature and distribution of sediments throughout the Holocene. Due to the intermittent nature of water exchange between the North and the Baltic Seas, the flow of bottom currents is impermanent. Well-developed nepheloid layers are commonly associated with these bottom currents, and provide evidence that active re-suspension and sediment transport is taking place. Periodically intensified inflow from the North Sea through the Baltic Sea gateway has led to erosion of narrow elongate channels, and associated deposition of small elongate patch drifts and contourite levees. The latter two are best developed on the left flanks of the channels. As a result of strong lateral sediment transport, the overall thickness of muddy contourite layers increases towards the steeper slopes of the sea which are situated on the right-hand side of the inflows. Muddy contourites of the Baltic Sea are predominantly terrigenous in composition, made up of soft, black sulphidic muds that are enriched in organic carbon and manganese. Both enrichments are caused by high biological productivity and periodic stagnation of near-bottom waters. Atypically for most oceanic contourites, these shallow-water organic-rich contourites are finely laminated and generally unbioturbated.
Faro-Albufeira drift complex, northern Gulf of Cadiz
Authors: Stow Dorrik A. V. , Faugères Jean-Claude , Gonthier Eliane , Cremer Michel , Llave Estefania , Hernández-Molina F. J. , Somoza Luis , Díaz-Del-Río V.
Published: April 2008

The northern margin of the Gulf of Cadiz is swept by Mediterranean Outflow Water between about 500 and 1000 m water depth. This warm, saline, thermohaline, bottom current attains velocities in excess of 1 m s
-1
through the narrow and relatively shallow Gibraltar gateway, and then descends and slows as it moves towards the north and west around the Iberian margin. It was established in its present form in the latest Miocene, following tectonic re-opening of the Gibraltar gateway, and has since helped to sculpt the slope region in conjunction with downslope processes and diapiric intrusion. The principal area of contourite deposition, up to 600 m in thickness, is the Faro-Albufeira drift complex in a mid-slope setting some 30 km south of Faro. This comprises an elongate low-mounded drift (Faro-Albufeira) and adjacent broad sheeted drifts (Faro and Bartolomeu Dias Planaltos), flanked and partly dissected by deep, erosional, bottom-current channels and buried channels. The seismic character is one
of progradational-aggradational depositional units with laterally extensive sub-parallel reflectors, widespread discontinuities and a large-scale cyclicity in seismic facies. The upper 10 m of cored section comprises muddy, silty and sandy contourites of mixed terrigenous and biogenic composition, that show small-scale cyclicity in grain size and associated sedimentary features. Rates of accumulation varied from < 1 to 14.5 cm ka
-1
(cores), and 3.5 to 29.5 cm ka
-1
(seismics). The large and small-scale cyclicity noted can be related to fluctuation in bottom current velocity related to climate and sea-level changes, although the precise correlation between these events remains uncertain.
The Vema contourite fan in the South Brazilian basin
Authors: Faugères Jean-Claude , Zaragosi S. , Mézerais M. L. , Massé L.
Published: April 2008

The Vema
contourite fan
is a Neogene mud-rich accumulation (200-400 m thick), fed by Antarctic Bottom Water bottom currents and located downstream of the Rio Grande Rise. It forms one single, mounded, fan-shaped body deposited between two major channels through which the main part of the deep AABW circulation is funneled. A suite of cores and seismic lines have been collected over the whole area. The sediments deposited below the shear zone between the two current branches consist almost exclusively of muddy contourites, either homogeneous in structure or micro-brecciated. Manganiferous deposits occur in the vicinity of the channels and on the channel floors. As a result of the morphological and hydrological background, the contourite drift has prograded mostly downstream. It is composed of several depositional units bounded by widespread discontinuities showing erosional patterns. This geometry results from an alternation of episodes of strong and unstable erosive currents, and periods of relatively weak and stable depositional currents
Mixed biosiliceous-terrigenous sedimentation under the Antarctic Circumpolar Current, Scotia Sea
Authors: Pudsey Carol J. , Howe John A.
Published: April 2008

Sediment supply to the Scotia Sea is controlled by the east-flowing Antarctic Circumpolar Current (ACC) with some Weddell Gyre influence in the south. Near-bottom flow is unsteady with frequent changes in flow direction and episodic benthic storms. Near the North Scotia Ridge, mounds of sediment up to 1 km thick have accumulated on lower Miocene ocean floor. The basins farther south contain up to 2 km of sediment which is flat-lying or draped rather than mounded. Sediment cores exhibit a biogenic-terrigenous cyclicity related to glacial-interglacial cycles. Grain-size data suggest that ACC flow was stronger during glacials than interglacials.
Current controlled deposition on the Wilkes Land continental rise, Antarctica
Authors: Escutia C. , Nelson C. H. , Acton G. D. , Eittreim S. L. , Cooper A. K. , Warnke D. A. , Jaramillo J. M.
Published: April 2008

Turbidite, contourite and hemipelagic deposition are the main components of Wilkes Land continental rise sedimentation above the regional unconformity WL2. On the continental shelf, unconformity WL2 marks the start of shelf progradation, which is interpreted to correspond with the onset of glacial conditions in this segment of the east Antarctic margin. Unusually large (i.e. up to 900 m relief and 18 km between levee crests) channel-levee deposits, and high relief (up to 490 m) mounded contourite-style deposits develop above unconformity WLlb. Unconformity WLlb overlies unconformity WL2 and is interpreted to have formed under a fully continental glacial regime where ice streams reached the palaeo-continental shelf edge. Based on an analysis of multichannel seismic profiles and sediment cores, we differentiate three phases in the development of the sedimentary unit between WLlb and the present seafloor. From older to younger these are: Phase 1, dominated by turbidite deposition; Phase 2, dominated by turbidite and contourite deposition with significant mound building; and Phase 3, dominated by turbidite and contourite deposition without active mound building. We hypothesize that building of the mounds during Phase 2 corresponded with times of expansion of the Antarctic ice-sheet when vast amounts of sediment were eroded from the continent and continental shelf. The large amount of unsorted glacial sediment supplied to the outer shelf apparently travelled down the slope canyons and rise channels as turbidity current flows to feed the usually large continental rise channel-levee complexes. The suspended fines of the turbidity flows were then entrained in a palaeo-nepheloid layer and carried by the westward flowing palaeo-contour currents until their deposition in the mounds. During Phase 3, sediment supply to the continental rise, although important in volume and capable of turbidite and contour-current deposition, was insufficient to support further building of the mounds. We believe the decrease in sediment supply to the continental rise from Phase 2 to Phase 3 could be the result of a change on sediment depocentres, with most of the sediment supplied to the margin during Phase 3 being trapped on the continental shelf. We believe that ultimately these changes are related to the stage of glacial evolution of the continent.
Neogene contourites, Miura-Boso forearc basin, SE Japan
Authors: Stow Dorrik A. V. , Ogawa Yujiro , Lee In Tae , Mitsuzawa Kyohiko
Published: April 2008

The mid to late Miocene Misaki Formation sediments of the Miura and Boso peninsulas, south central Japan, were deposited in the Pacific-facing forearc region of the proto Izu-Bonin arc at bathyal depths. The hemipelagic background facies, composed mainly of calcareous biogenic and pumiceous voicaniclastic material, are interbedded with thin to thick scoriaceous beds of turbiditic and pyroclastic fall origin. Careful study in the field and in the laboratory of these fine-grained background sediments has revealed the marked influence of bottom currents at certain horizons in producing intervals with distinct muddy contourite characteristics. These include: a general absence of primary structures due to intense bioturbation, some diffuse layering, irregular concentrations of coarser-grained material, sharp and erosive top and bottom lamina contacts, rare micro-cross-lamination disrupted by bioturbation that was continuous with deposition, and a mixed pelagic biogenic (commonly fragmented), volcaniclastic and terrigenous composition. Small-scale cyclicity of variations in grain-size and structural features can be related in part to episodic volcaniclastic input and in part to fluctuation in bottom current strength. Evidence for bottom current reworking of the tops of thin-bedded sandy turbidites is equivocal, and further work is required to resolve this debate. The recognition of Miocene-age contourites from the NW Pacific provides further evidence for the existence of active deep-ocean circulation in the Pacific at this time. However, it is not possible to determine which current system, Antarctic Bottom Water or deep Kuroshio Current, was responsible for these outcrop examples of fossil contourites.
Kuroshio Current-influenced sandy contourites from the Plio-Pleistocene Kazusa forearc basin, Boso Peninsula, Japan
Authors: Ito Makoto
Published: April 2008

Lithofacies features of bottom current influenced deep-sea sandy deposits (sandy contourites) have been studied by detailed outcrop analyses of the Plio-Pleistocene infill of the Kazusa forearc basin on Boso Peninsula, Japan. Sandy contourites are characterized by traction structures, such as parallel lamination and ripple cross-lamination, together with minor inverse grading and wave ripple-lamination. Ripple cross-lamination is commonly associated with mud drapes and flaser and lenticular bedding. These sedimentary structures do not display any regular vertical sequences. Sandy contourites are commonly associated with turbidites and comprise turbidite-to-contourite continuums. In general, sandy contourites are better sorted than associated turbidites and have sharp or gradational basal contacts with underlying turbidites or hemipelagites, and sharp upper contacts with overlying hemipelagites. The framework composition of sandy contourites, in contrast, is largely equivalent to that of the associated turbidites. Palaeocurrent directions of sandy contourites are variable in time and space and alongslope- and upslope-directed palaeocurrents are dominant. Turbidite-to-contourite continuums show spatial and temporal variation in bed thickness and lithofacies features. These variations suggest varying intensity of deep-sea bottom currents in the Kazusa forearc basin. Analogous flow conditions have been documented from the modern, deep-water mass of the Kuroshio Current. Thus, the observed variations in lithofacies features and palaeocurrents of turbidite-to-contourite continuums can best be interpreted in terms of fluctuating strength of the deep-water palaeo-Kuroshio bottom current during the Pliocene through Pleistocene
UK Oil and Gas Fields - An Overview
Authors: Gluyas J. G. , Hichens H. M.
Published: April 2008

This volume was conceived when one of us (JG) returned to the UK in mid-1996. Having not worked the UK offshore since the late 1980s it was clear that there had been many changes, not least in the number of fields on production. During that first year back in the UK, JG's copy of Abbots (1991)
UK Oil and Gas Fields, 25 Years Commemorative Volume
became exceedingly well used. A casual comment to Wendy Cawthorne of the Geological Society library to this effect solicited the response that JG was not alone in finding Abbots (1991) useful. Memoir 14 was the Geological Society's 'best seller'. However, although Abbots (1991) continues to sell well, it was by 1996 out of date insofar as it contains papers describing only about half of the fields then on production.

A combination of egotistical zeal, wishing for a bestseller and altruism towards the UK industry led us to make an offer to the Geological Society to revise Memoir 14. The offer was accepted and by April 1998, editors had been appointed and letters of invitation to contribute to the memoir were sent to exploration managers in all the UK operating companies. The responses to those letters were for the most part positive. A request was made to authors for manuscripts to be sent to the editors by June 1999. The first to arrive was six months ahead of schedule (thanks A. Yaliz & N. McKim for their paper on the Douglas Field). However, neither the editors
The Beryl Field, Block 9/13, UK North Sea
Authors: Karasek R. M. , Vaughan R. L. , Masuda T. T.
Published: April 2008

The Beryl Field is located within Block 9/13 in the UK North Sea, in the west central part of the Viking Graben. The block was awarded in 1971 to a Mobil operated partnership, and the 9/13-1 discovery well drilled in 1972. The Beryl A platform was installed in 1975 and oil production started up the following year. The Beryl B platform was added in 1983 and production and gas re-injection pressure support commenced in 1984. The first 3D seismic survey was shot over the field in 1986, and the most recent in 1997. As of January 1999, 133 wells have been drilled into the field and development drilling is expected to continue well into the twenty-first century.

Commercial hydrocarbons occur in sandstone reservoirs ranging in age from Triassic to late Jurassic, with the primary reservoir being the Middle Jurassic Beryl Formation (1.4 billion barrels of oil originally in place). Total ultimate recovery for all reservoirs in the field is expected to be about 960 million barrels of oil (MMBBL) and 2.1 trillion cubic feet (TCF) of gas. As of January 1999, the field has produced nearly 710 MMBBL of oil, or almost 75 % of the ultimate oil recovery.

The field has been described previously by Knutson and Munro (1991), and Robertson (1993). Recent drilling data (more than 30 new wells) and new 3D seismic have updated the initial field descriptions. These data allow the mapping of two key unconformities, the Mid Cimmerian (Jt) event and a Base Callovian (Jb3) event. Reservoir facies models and isochore maps have also been developed, which together with the refined structural model, allow a better understanding of the reservoir distributions and will guide future production strategies.
The North Brae and Beinn Fields, Block 16/7a, UK North Sea
Authors: Brehm J. A.
Published: April 2008

North Brae is located in Block 16/07a, and was discovered in 1975 by Pan Ocean Oil Company. The field was purchased by Marathon Oil Company in 1976 and was delineated in the early 1980s. Production by gas recycling was commenced in 1988. Liquid reserves are estimated at 207 MMBBLs with recoverable dry gas of 800 BCF.

The North Brae Field is one of three gas/condensate fields in the Brae fields area of the South Viking Graben in the UK Sector of the North Sea. The reservoir is part of a large turbidite and debris flow, submarine fan system that also encompasses the East Brae and Kingfisher fields to the northeast of North Brae. North Brae is located at the proximal end of this fan system, and channelized massive conglomerates and sandstones characterize its reservoirs. The stratigraphy of the fan system was influenced by highly variable changes in relative sea level that controlled sediment input. Structural activity was also important, such as syn-sedimentary normal faulting related to the subsidence of the South Viking Graben, and structural inversion, in a series of regional compressive episodes commencing in the Late Jurassic and Early Cretaceous.
The West Brae and Sedgwick Fields, Blocks 16/06a, 16/07a, UK North Sea
Authors: Wright Simon D.
Published: April 2008

abstract

The Marathon-operated West Brae Field straddles Blocks 16/06a and 16/07a in the UK Central North Sea approximately 140 miles (225 km) NE of Aberdeen. The field was discovered in 1975 with drilling of exploration well 16/07-2. The West Brae reservoirs consist of Eocene Balder Formation and Upper Sele Formation Sandstones that were deposited in NW-SE trending submarine channels across the area. Development of the field commenced in April 1997 with first oil being achieved in October the same year. The filed has been developed using sub-sea tie-back to the Brae A platform, which lies 5.6 miles (9 km) SE of the sub-sea manifold. Recoverable reserves are estimated to be 60 MMBBLs, of which some 23 MMBBLs had been produced by 31 December 1999
The Staffa Field, Block 3/8b, UK North Sea
Authors: Gluyas J. G. , Underhill J. R.
Published: April 2008

The Staffa Field occurs at the crest of an intermediate tilted fault block that is located between the Ninian and Alwyn fields in the northern North Sea. The partnership BP, Lasmo and Ranger discovered the field with well 3/8b-10 in 1985. By 1990, BP had left the partnership while Lasmo and Ranger had received Annex B approval for development. First production from this small field reservoired in sandstones belonging to the Middle Jurassic, Brent Group was obtained in 1992. At sanction, reserves were estimated to be about 5.5 MMBBL together with 26.8 BCF corresponding to a recovery factor of 18%. Field life was expected to be about 7.5 years (to 2000) and the plateau length six months. Although initial production exceeded the planned plateau rate of 8000 BOPD, production ceased in June 1993 when the pipeline to Ninian became blocked with wax or wax hydrates. Remedial solvent treatment failed to remove the blockage and replacement of the blocked section was undertaken. This too became blocked soon after resumption of production and the field was shut-in in November 1994. It was then abandoned, since further replacement of the line was not justified economically. At abandonment the field had produced 3.9 MMBBL of oil, 0.296 MMBBL of NGL and 6.457 BCF of gas Gust 13% of its original STOIIP).
The T-Block Fields, Block 16/17, UK North Sea
Authors: Gambaro M. , Donagemma V.
Published: April 2008

abstract

The Tiffany, Toni, Thelma and SE Thelma fields, collectively referred to as the T-Block fields lie wholly within UK Block 16/17 at the southern end of the South Viking Graben. The four fields were discovered between 1976 and 1980 and despite the fact that they share a common reservoir, the Upper Jurassic Brac Formation, they are quite distinct in terms of their petroleum content (type), reservoir quality and production performance. This paper summarizes the characteristics of the T-Block petroleum accumulations and highlights the differences between each of the field.
The MacCulloch Field, Block 15/24b, UK North Sea
Authors: Gunn C. , MacLeod J. A. , Salvador P. , Tomkinson J.
Published: April 2008

The MacCulloch Field lies within Block 15/24b in the UK Central North Sea and is located on the northern flank of the Witch Ground Graben. It was discovered by Conoco well 15/24b-3 in 1990.

MacCulloch Field is a four-way dip closure at Top Paleocene over a deeper Mesozoic structure. The reservoir consists of Upper Balmoral Sandstones containing 32-37° API oils derived from Kimmeridge Clay Formation shales and sealed by shales belonging to the Sele Formation. The field contains recoverable reserves of 60-90 MMBOE.

Reservoir quality is generally very good, with an average porosity of 28% and core permeabilities (Kh) between 200 mD and 2D. AVO anomalies and a seismic flat spot are associated with oil filled reservoir and the oil-water contact in certain areas of the field.
The Davy, Bessemer, Beaufort and Brown Fields, Blocks 49/23, 49/30a, 49/30c, 53/5a, UK North Sea
Authors: McCrone C. W.
Published: April 2008

abstract

Davy, Bessemer, Beaufort and Brown are a series of small to moderate (30-200 BCF) dry gas fields, which span the southeastern corner of the UK Southern North Sea Rotliegend Play fairway. Davy was discovered in 1970; however, it was not until 1989 that Bessemer and subsequently Beaufort in 1991 were drilled. These fields were developed and brought on-stream by Amoco licence groups in 1995/96. More recently the Brown Field was discovered in October 1998 with first gas seven weeks later. The commercial viability of these relatively small accumulations is the result of technical advances across several fronts: 3D seismic imaging, horizontal well technology and minimum offshore facilities.

In the Bessemer and Beaufort area, the Rotliegend Leman Sandstone Formation reservoir (250 ft) primarily consists of stacked aeolian dune sandstones of good reservoir quality (porosity 17%, permeability 10-1000mD). However, in the Davy and Brown area there is greater variation in the Rotliegend isopach (300-700 ft) and the nature of facies present e.g., aeolian dune, sabkha and playa lake.

The fields are tied back from the Bessemer and Davy mono-tower platforms via 15 km and 43 km pipelines, respectively, to the compression facilities on the Indefatigable 23AT platform.
The Leman Field, Blocks 49/26, 49/27, 49/28, 53/1, 53/2, UK North Sea
Authors: Hillier A. P.
Published: April 2008

Discovered in 1966 and starting production in 1968, Leman was the second gas field to come into production in the UK sector of the North Sea and is still producing gas today. It is classified as a giant field with an estimated initial gas-in-place of 397 BCM of gas in the aeolian dune sands of the Rotliegend Group. The field extends over five blocks and is being developed by two licence groups with Shell and Amoco (now BP Amoco) being the operators
The Mercury and Neptune Fields, Blocks 47/9b, 47/4b, 47/5a, 42/29, UK North Sea
Authors: Smith B. , Starcher V.
Published: April 2008

The Mercury and Neptune Gas Fields, discovered in 1983 and 1985 respectively, are located on the NW margin of the southern North Sea. Both fields have reservoirs in the Permian Lower Leman Sandstone Formation of the Rotliegend Group. The Mercury Field, at Rotliegend level, is an elongate, southerly tilting horst block. It trends NW-SE and is bounded by reverse faults. The Neptune Field, at top reservoir level is a faulted, four-way dip closed structure that is elongated in a NW-SE direction. The combined gas-in-place for the two fields is estimated at 465 BCF with recoverable reserves of 368 BCF. Development drilling on Mercury commenced in early 1999 and on Neptune it is scheduled to start in Q3 1999. The maximum gas export rate will be 250 MMSCFD with first gas anticipated in November 1999.
The V-Fields, Blocks 49/16, 49/21/, 48/20a, 48/25b, UK North Sea
Authors: Courtier James , Riches Hugh
Published: April 2008

The Vulcan, Vanguard, North and South Valiant gas fields are collectively known as the V-Fields and lie on the eastern flank of the Sole Pit Basin in the southern sector of the UK North Sea. They are contained within blocks 49/16, 49/21, 48/20a and 48/25b and are operated by Conoco (UK) Ltd. The first field to be discovered was South Valiant, in 1970, and the initial phase of exploration drilling continued until 1983, with the discovery of the North Valiant, Vanguard and Vulcan fields. Prominent faults and dip closures define the limits of the fields and gas is contained within aeolian sands of Early Permian age. The gross average reservoir thickness is approximately 900 ft with porosities ranging from 3-23% and permeabilities varying from 0.1 mD to 2 Darcies in producing zones. The development of the V-Fields consisted of drilling centrally located production wells in each field, targeting higher quality reservoir zones in areas of maximum structural relief. Initial gas-in-place is estimated at 2.6 TCF with recoverable reserves of about 1.6 TCF. The fields were brought on-stream in October 1988 and currently produce, as of November 1999, up to 260MMSCFD of gas through the LOGGS complex to the Conoco terminal at Theedle-thorpe, Lincolnshire.
The Waveney Field, Block 48/17c, UK Southern North Sea
Authors: Bruce D. R. S. , Rebora P.
Published: April 2008

The Waveney Field lies entirely within UK block 48/17c in the Southern Gas Basin, approximately 46 km north-east of the Norfolk coast line and to the west of the Mobil's Lancelot and Guinevere Fields. The water depth is approximately 75 ft. The field was discovered in 1996 by the 48/17c-12 well and brought on production in 1998 following a 14 month fast track development program and the drilling of two 2500 ft horizontal wells. The gas field is a low relief northwest trending asymmetrical anticline, with a length of 6 kms, and a maximum width of 2 kms. The crest of the structure is at approximately 7748 ft. TVDSS. The original reserves were 84 bcf. The reservoir predominantly comprises aeolian dune sandstones of the Upper Permian Rotliegend with an average reservoir quality range of 7-10% porosity and 0.1-200mD permeability. The hydrocarbons are sourced from down dip Carboniferous Westphalian Coals.
The Sean North, Sean South and Sean East Fields, Block 49/25a, UK North Sea
Authors: Hillier A. P.
Published: April 2008

Sean North, Sean South and Sean East are small prolific gas fields located on the Indefatigable Shelf in the Southern North Sea. They, like most of the other fields in the area, have a Carboniferous source, a Rotliegend aeolian sandstone reservoir and a Zechstein evaporite cap rock. Sean North and South have been developed to fulfil a peak-shaving role, being produced for only a few days per year in times of high gas demand when they can produce at rates of up to 600 MMSCF/D. East Sean is sold to the direct market. Reserves for the fields are 234 BCF (North), 488 BCF (South) and 127 BCF (East).
Sea bed morphology of the Faroe-Shetland Channel derived from 3D seismic datasets
Authors: Long D. , Bulat J. , Stoker M. S.
Published: April 2008

First returns from 3D exploration surveys have been utilized to display seafloor morphology of the Faroe-Shetland Channel between the UK and the Faroes. The image combines 32 datasets creating a regional perspective of Quaternary sedimentary processes. Geomorphic information is of significance for sea bed geohazard evaluation, environmental studies and as an analogy for former sedimentary environments. The image covers more than 25000 km
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extending from the shelf (water depth ∼ 120 m) to the basin floor (water depth up to ∼ 1600 m).

On any margin knowledge of the sea bed morphology is essential for understanding the environmental setting and for safe operations in deepwater. Under favourable circumstances, the sea bed can be picked from 3D exploration seismic surveys in a similar manner to any other horizon to provide detailed images of the seafloor, thereby negating the need for dedicated sea bed surveys. Combining first returns from several surveys creates a regional perspective, essential when considering importance of features e.g. the rarity of a certain seafloor environment or the presence of a potential landslide upslope from an operations area.

The Faroe-Shetland Channel displays a wide range of sea bed features including, sediment waves, contourite deposits, polygonal cracking, landslides, debris flows, turbidity current channels, glacial moraines and iceberg ploughmarks. Resolving the spatial aspects of these features greatly assists the interpretation of shallow profile data for geohazard and environmental studies and provides a backdrop onto which biologists, oceanographers, sedimentologists and engineers can overlay their data sets and thus their interpretations.
3D Analogue Models of Rift Systems: Templates for 3D Seismic Interpretation
Authors: McClay K.R. , Dooley T. , Whitehouse P. , Fullarton L. , Chantraprasert S.
Published: April 2008

3D visualizations of modern, high-resolution seismic data have provided valuable insights into the finite geometries and spatial extent of extensional fault systems, but their evolution in time is poorly understood. Scaled 3D analogue models of rift basin evolution provide kinematic templates for understanding the 4D evolution of extensional fault systems. This paper reviews the development of extensional fault systems in analogue models of orthogonal, oblique and offset rifts. In orthogonal and oblique models, stretching above a zone of ductile deformation at the base of the model initially produced segmented rift border faults whose orientations were strongly controlled by the underlying baseplate configuration. In contrast, the intra-rift faults generally initiated at high angles to the extension direction. With increased extension both the rift border faults and the intra-rift faults propagated along strike, first producing segmented fault systems separated by relay ramps, which, with increased extension, became breached as fault linkage occurred. Kinks in the fault traces indicate linkage points. Within the models, asymmetric intra-rift sub-basins were formed where the extensional fault arrays had a dominant dip polarity. Intra-basin accommodation zones, separating individual sub-basins along the rift axis, were formed by interlocking oppositely dipping fault systems. Offset oblique rift models, formed above a zone of ductile stretching with basement offsets, generated intra-basin accommodation zones whose orientation was controlled by the underlying basement fabric. The results of the analogue models can be directly compared with fault systems in the Northern Ethiopian rift system, with the accommodation zones in the Gulf of Suez, Egypt, with extensional fault arrays in Canyonlands, Utah, and with rift fault systems in the Gulf of Thailand and the southern North Sea.
Kinematic Indicators for Shallow Level Igneous Intrusions from 3D Seismic Data: Evidence of Flow Firection and Feeder Location
Authors: Trude K. J.
Published: April 2008

This paper describes some of the results from a 3D seismic-based analysis of the mechanics of igneous sill emplacement in sedimentary basins. Detailed 3D interpretation of igneous intrusions flanking the Corona Ridge in the Faroe-Shetland Basin has led to the discovery of a sill (the Corona Sill) with a previously unrecognized morphology. Two potential feeder sources have been interpreted for the broadly rectangular intrusion, of which the surveyed portion measures approximately 15 by 4 km. The Corona Sill has a linear NW margin and two lobate protuberances along the SE side. Arcuate ridges that radiate from a central point at the intersection of the lobes cover the imaged surface of the sill. The ridges have wavelengths of 220-350m and amplitudes in the range 25-50m.

The ridged morphology on the surface of the Corona Sill has not previously been described from any seismic or outcrop-based study of igneous sills. The ridges are interpreted to have formed as a direct result of the propagation mechanism, and are thought to have been influenced by the viscosity of the magma, host sediment and the depth of intrusion, which is likely to have been within 400 m of the sediment-water interface. It is suggested that during very shallow intrusion of viscous magma into soft, waterlogged sediments, magma is able to spread, creating a geometry similar to that expected for a high viscosity lava flow.

Ridges were formed by compression of a more rigid outer layer of magma in the sill, retarded by the solidifying sill front. Forward movement of the surface layer is likely to be caused by viscous drag from within the sill body. The ridges on the sill top surface are a kinematic indicator for the flow direction of the magma, enabling identification of the feeder zone, which displays a clear link to an underlying sill. It is demonstrated that 3D seismic data has significant untapped potential for the study of magma transport and intrusive processes in the upper crust
Locating Exploration and Appraisal Wells Using Predictive Rock Physics, Seismic Inversion and Advanced Body Tracking: an Example from North Africa
Authors: Pickering G. , Knight E. , Bletcher J. , Barker R. , Kemper M.
Published: April 2008

A case study is described that illustrates a complete reservoir property prediction workflow, from petrophysical analysis, through rock physics, impedance inversion, and on to interpretation and final drilling locations. This study is from onshore Algeria, where the hydrocarbons are found in several clastic reservoirs of varying ages and properties. The controls on the presence of both reservoir and hydrocarbon location are not straightforward, therefore reducing the risk of drilling locations has significant value. This study concentrated on the Triassic TAG-I formation, which forms the major reservoir in the study area. The prediction method used was an impedance based deterministic approach, using relationships based on rock physics, although the interpretation method includes fuzzy set classifications to take into account the knon-uniqueness' inherent in any seismic attribute. The petrophysical work ensured that the analysis of each well reconstructed *virgin-zone" conditions. Rock physics models were then used to predict shear wave velocities. Acoustic impedance (AI), shear impedance (SI), and elastic impedance (EI) profiles were derived. Shear impedance was the best pure lithology indicator, with acoustic impedance showing a good relationship to porosity and elastic impedance most sensitive to fluid content. As the near angle seismic data were too noisy, gradient/intercept analysis was impossible, so shear reflectivity and consequently SI could not be derived. Although AI showed some lithological discrimination between sands and shales, it was not sufficient to be used as a single discriminator, so interpreted horizons were used to separate reservoir and non-reservoir intervals. The far-angle data were inverted to EI and this was analysed using a fuzzy logic approach. This method produces a classification volume and 3D body tracking was then used to find the best drilling targets. Generally, the analysis correctly predicted the results of the wells, both discoveries and non-discoveries. However, some of the discoveries were not predicted, which appears to be where the classification was not correctly calibrated. Work is now underway to improve the accuracy of the prediction process.