The geological processes that create fluid storage capacity and connectivity in global fractured basement reservoirs are poorly understood compared to conventional hydrocarbon plays. Hosting potentially multibillion barrels of oil, the upfaulted Precambrian basement of the Rona Ridge, offshore west of Shetland, UK, gives key insights into how such reservoirs form. Oil presence is everywhere associated with sub-millimeter- to meter-thickness mineralized fracture systems cutting both basement and local preseal cover sequences. Mineral textures and fluid inclusion geothermometry suggest a low-temperature (90–220 °C), near-surface hydrothermal system, as does the preservation of clastic sediments in the same fractures. These fills act as permanent props holding fractures open, forming long-term fissures in the basement that permit oil ingress and storage. Calcite-fill U-Pb dating constrains the onset of mineralization and contemporaneous oil charge to the Late Cretaceous. The additional preservation of oil-stained injected sediment slurries and silica gels along basement faults suggests that rift-related seismogenic faulting initiated lateral oil migration from Jurassic source rocks into the adjacent upfaulted ridge. Subsidence below sea level in the latest Cretaceous sealed the ridge with shales, and buoyancy-driven migration of oil into the preexisting propped fracture systems continued long after the cessation of rifting. These new observations provide an explanation for the viability of sub-unconformity fractured basement reservoirs worldwide, and have wider implications for subsurface fluid migration processes generally.

The hydrocarbon prospectivity of the Faeroe–Shetland White Zone, located in the area between the Shetland and Faeroe Islands, was assessed in a regional study that integrated seismic and well interpretations with detailed source-rock geochemistry and predictive basin modelling.The Faeroe Basin formed during a Barremian rifting event followed by subsidence during the Late Cretaceous. The Paleocene began with a period of thermal uplift of basement highs and rapid sedimentation which infilled the submarine topography formed during the Cretaceous, and produced marked overpressuring in the basin. Gradual subsidence continued through the Tertiary except for a significant mid Tertiary inversion event that formed several interesting structures in the basin.New thermal models of basins and a new pressure mechanism for inducing hydrofractures that allow vertical hydrocarbon migration from Jurassic source rocks through Cretaceous mudrocks to Tertiary reservoirs, which we call the ‘whoopee cushion effect’, provide the key controls on the hydrocarbon charge mechanism, timing and petroleum composition.The other crucial elements, source, reservoir, and traps which are present at several stratigraphic levels in the White Zone, are summarized in this paper.The interplay of overpressure, hydrocarbon generation and migration during a complex basin evolution makes the White Zone a highly prospective frontier petroleum province.

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The Clair Field is a giant oilfield containing in the region of 6–7 Bbbl of stock tank oil initially in place, located approximately 75 km west of the Shetland Islands. As such, it represents the single biggest hydrocarbon accumulation on the UK Continental Shelf. Clair was discovered in 1977, but first production did not occur from Phase 1 until 2005, after a lengthy appraisal period. The major appraisal milestone occurred in 1991 after well 206/8-8 proved up fractured clastic red beds of the Devonian Lower Clair Group. This was followed up with an extended well test on 206/8-10Z, which demonstrated the longer-term performance of the reservoir. Further appraisal on Clair Ridge led to the sanction of the Clair Ridge, which came on stream in November 2018. Following the Greater Clair appraisal programme in 2013–15, development options are currently being worked for Clair South, which will develop the Lower Clair Group reservoirs together with overlying shallow-marine reservoirs of the Cretaceous and Jurassic.

Bulletin 106. 1920, 879 pages, 279 text figures and 162 plates. Students of bothl fossil and recent bryozoa will greet with interest and pleasure this monumental work long anticipated and recently issued, for while treating primarily of fossil bryozoa this monograph contains much of interest to students of living forms. This work appears in two volumes, one containing the text anA text figures, the other consisting of photographic plates alone. A cursory inspection reveals the fact that these volumes possess the excellence of copious illustration, a most satisfactory virtue in. the eye of those who will use them. The text figures are abundant, the number as stated above (279) by no means giving a true idea of the actual number, since each figure consists of from two to ten or more illustrations, representing .portions or organs of the species under discussion, and often besides figures of nearly related species for comparison. From this point of view the number given should be multiplied many times, and by actual count the first fifteen text figures contain more than one hundred separate drawings or preparations. These are all either original with the authors or are taken from the illustrations of other bryozoologists. Each photographic plate likewise contains from twelve to twenty-five separate photographs. These are distinguished by a remarkable clearness and definiteness of outline, even of minute details, revealing an unusually skilful management of light !and shade and producing an excellent and expert piece of work which will not fail to call forth the gratitude as well as the admiration of their fellow workers. Over 700 species belonging chiefly to the two orders, Cyclostomata and Cheilostomata, are treated in this monograph.. In the seventy or more pages of introduction the authors present many topics of interest involving new points of view which will doubtless stimulate further research. Of these topics but three will be touched upon. 1. It is gratifying to find clear definition and illustration of 69