Abstract: Numerical models and recent outcrop case studies of alluvial-to-coastal-plain strata suggest that autogenic avulsion can control the stacking density and architecture of channelized fluvial sandbodies. The application of these models to subsurface well data was tested by the analysis of upper coastal plain deposits of the late Bajocian Ness Formation in the Brent Field reservoir, UK North Sea. These coastal plain deposits accumulated during the progradation and retrogradation of the wave-dominated ‘Brent Delta’. Sedimentological facies analysis and palaeosol characterization in cores were used to interpret the styles of palaeochannel avulsion. These results were then compared with the dimensions and distributions of channelized fluvial sandbodies that had been quantified by spatial statistical tools (lacunarity, Besag’s L function) applied to interpretative correlation panels between closely spaced wells. The results indicate that the distributions of channelized sandbodies may plausibly have been generated by avulsions and that they influence sandbody connectivity and pressure depletion patterns. Intervals of upper coastal plain strata with relatively wide sandbodies that display some clustering in their stratigraphic architecture are associated with a high proportion of avulsions by incision and annexation in core samples. Such intervals display relatively good vertical pressure communication and relatively slow, uniform pressure depletion.

Abstract A core repository is a physical record of a country's or commercial organization's subsurface wealth. Some of the largest core repositories hold thousands of kilometres of core material and it is a challenge to turn this physical archive into an accessible digital resource for all. Non-destructive multi-sensor core logger, hyperspectral and X-ray imaging techniques offer a unique chance to rescue valuable data trapped within core samples, improving the way that a core repository delivers data to academic or industrial end users. Here we present a case study of an archived petroleum core acquired in 1985 at the Osprey Field, UK Continental Shelf. Data from the UK National Data Repository are augmented by a multi-sensor core logger, hyperspectral and X-ray dataset that is uploaded into a cloud-based digital repository. The data were analysed using a multi-variant analysis to reclassify the original lithological interpretations, uncovering a greater proportion of clay and cemented horizons than was previously interpreted. A workflow is established to optimize the use of legacy cores and exploit the abundance of data trapped within the core repository using continuous multi-sensor core scanning and imaging data, which are stored within the virtual environment for visualization and access to all.

Abstract This chapter describes Middle Jurassic second-order sequences J20 and J30, and their component third-order sequences, J22–J26 and J32–J36. The J22 sequence contains the major Intra-Aalenian Unconformity (‘Mid-Cimmerian’) across a wide area of the North Sea Basin and an equivalent event onshore UK. The base J24 (Lower Bajocian) is marked by the Rannoch Shale (Brent Group) and by the flooding of the Ollach Sandstone, Hebrides Basin. The base J26 (Upper Bajocian) ties to the Mid Ness Shale (Brent Group) and the base of the Upper Trigonia Grit Member, central England. The base J32 (Upper Bajocian) ties to the base of the Tarbert Formation, the base of the Great Oolite Group in central England and the base of the Great Estuarine Group, Hebrides Basin. The base J33 (Middle Bathonian) falls within the Tarbert Formation and the base of the Taynton Limestone, central England. The base J34 (uppermost Middle Bathonian) commonly falls at the top of the Brent Group. The base J36 (uppermost Bathonian) represents a major increase in marine influence, at the base of the Beatrice Formation, in the Inner Moray Firth and at the base of the Staffin Bay Formation, Hebrides Basin.

Studies of Upper Devonian rocks in western Utah and central and eastern Nevada have determined the presence of 101 species of 25 conodont genera. The description of this fauna, which includes a new species of Palmatolepis? , has led to the recognition of distinct conodont assemblages and zones which are considerably more refined than previous classifications in this area. Representatives of nine of the ten major Upper Devonian conodont zones which have been defined in Germany can be recognized in the Great Basin rocks. These zones are, from oldest to youngest, the dubia (= asymmetrica? ), Ancyrognathus triangularis, gigas, Palmátolepis triangularis, crepida, rhomboidea, quadrantinodosa, velifera , and the costatus . In Germany, Ziegler (1962b) has recognized 24 subdivisions of the ten major zones. Elements of ten of the first 15 subdivisions (lower and middle Upper Devonian) and two of the upper nine subdivisions (upper Upper Devonian) have been identified in Utah and Nevada. The uppermost part of the Devonian has yielded the most meager faunas in the Great Basin rocks. The distinctiveness of many of the German zones is based on first and last occurrences of apparently phylogenetically related conodont “species.” Similar occurrences are recognized in the Great Basin rocks, but, in general, conodonts are less numerous in these geosynclinal sequences than in the German sections. This is probably due, in part, to the distribution of conodonts through a greater thick-ness of sediment in the Great Basin. The lowest zone recognized is considered the base of the Upper Devonian and is characterized by the same assemblage used to designate the middle dubia (= asymmetrica? ) zone in Germany. In Nevada, 34 species have been identified in this assemblage, of which only four occur in younger rocks. Most important elements of this assemblage are the name species, Polygnathus dubia asymmetrica Bischoff and Ziegler, P. dubia Hinde (= P. asymmetrica ovalis Ziegler and Klapper?), Ancyrodella rotundiloba (Bryant), and Palmatolepis? ziegleri n. sp. This fauna has been identified in the lower part of the upper Devils Gate Limestone in central Nevada and in an unnamed formation in north-central Nevada from which thousands of specimens have been recovered. The Ancyrognathus triangularis zone has been recognized above the dubia (= asymmetrica ?) zone in the Devils Gate Limestone in central Nevada, in the uppermost beds of the Guilmette Formation in western Utah, and in the lower beds of the Pilot Shale in this same area. The species identified include the name species and Palmatolepis foliacea , which is most important for the zone identification. Both the lower and upper gigas zones can be distinguished in the Pilot Shale of western Utah where 15 species are identified in the lower part and six species in the upper. Species of Palmatolepis , including P. unicornis in the lower zone and P. linguiformis in the upper, aid in recognition of these divisions. The three divisions of the Palmatolepis triangularis zone recognized in Germany can be identified in the Devils Gate Limestone and the Pilot Shale. The lower division is characterized by the first occurrence of the name species before the occurrence of palmatolepid species which are present in the overlying zone. The middle division assemblage consists of 21 species, nine of which are recognized only in this zone. The upper division has been identified by the presence of 22 species, including six species of Palmatolepis . Only the lower division of the crepida zone is recognized in the Great Basin and this is done on the occurrence of 18 species, more than half of which are present in other zones as well. Specimens of P. quadrantinodosalobata of the type identified in Germany (Ziegler, 1962b, p. 28) aid in the determination of this zone. The rhomboidea zone is well developed in the upper beds of the Devils Gate Formation where seven species of Palmatolepis not recognized in higher or lower intervals plus five other species are present. The lower quadrantinodosa zone has been recognized in a single sample of the Pilot Shale of western Utah but this sample includes the diagnostic P. quadrantinodosa inflexa . The velifera zone is distinguished by the presence of Palmatolepis rugosa trachytera and five other species which have been found in several samples of the Pinyon Peak Limestone of central Utah. The highest conodont zone recognized includes Polygnathus vogesi and Spathognathodus aculeatus which are indicative of the middle costatus zone in Germany. These two species occur in the lower beds of the Fitchville Formation in central Utah. The presence of conspecific conodonts in the same sequence as that found else-where confirms the widespread biostratigraphic value of the multiple Upper Devonian zonation which was first well defined in Germany.

Abstract The Pelican Field lies in the East Shetland Basin, in Block 211/26, roughly 150 km NE of the Shetland Islands. It was discovered in 1975 by exploration well 211/26-4. Development was delayed until 1995 when economic development became feasible as a subsea tie back to the Cormorant Alpha Platform. The reservoir is the Middle Jurassic Brent Group, comprising sands deposited in a fluvio-deltaic, shallow-marine, wave-dominated system. The reservoir interval has an average thickness of around 300 ft, ranging from 220 ft on the crest to 400 ft in down-flank areas. The crest of the field lies at around 10 500 ft true vertical depth subsea. Current estimate of oil in place for the field is c. 500 MMbbl. The Pelican Field suffers from significant deterioration of reservoir properties with depth, leading to low recovery factors of 15–20%. To date, 21 production and injection wells have been drilled recovering a total of 76 MMbbl. Oil production started in 1996 and peak oil production was achieved at 50 000 bopd in the same year. Rates declined due to water-cut development in most of the wells and current production rates are around 2000 bopd.