Abstract The Auk Field is located in Block 30/16 at the western margin of the Central Graben. Block 30/16 was awarded in June 1970 to Shell/Esso, and the discovery well 30/16-1 spudded in September 1970. The well found oil in a complex horst block sealed by Upper Cretaceous chalk and Tertiary claystones. The field contained an original oil column of up to 400 ft within Rotliegend sandstones, Zechstein dolomites, Lower Cretaceous breccia and Upper Cretaceous chalk. Production by natural aquifer drive commenced from a steel platform in 1976, initially from the Zechstein carbonates and now predominantly from the Rotliegend sandstone. Artificial lift was installed in 1988 helping to maintain production at economic levels past the year 2000. A complex reservoir architecture with cross flow between the Rotliegend and Zechstein reservoirs, a strong aquifer causing early water breakthrough via faults, and a limited seismic definition led to significant production variations from the initial forecasts. Equally important for the field, horizontal well technology opened up additional reserves and accelerated production from the complex Rotliegend reservoir; the most recent volumetric estimate for the total field predicts an ultimate recovery of 151 MMBBL for the existing wells from a STOIIP of 795 MMBBL . Full field reservoir simulation and 3D seismic data acquisition took place since mid 1980s but only recently resulted in a satisfactory understanding of the reservoir behaviour. The field is situated about 270 km ESE from Aberdeen in 240-270 ft of water. It covers a tilted horst block with an area of 65 km 2 , located at the western margin of the Central Graben. The Auk horst is bounded on the west by a series of faults with throws of up to 1000 ft, the eastern boundary fault has a throw of 5000 ft in the north reducing in throw southwards. The best reservoir lithology in the Zechstein is a vuggy fractured dolomite, and in the Rotliegend dune slipface sandstones provide the majority of the production. Both reservoirs and the overlying Lower Cretaceous breccia shared a common FWL at 7750 ft TVDss. The 38° API oil with a GOR of 190 SCF/STB was sourced from organic-rich Kimmeridge Clay.

Abstract A cored borehole through the Early Devonian Rhynie cherts at Rhynie, Aberdeenshire, NE Scotland, has revealed 53 chert beds in 35.41 m of core. The cherts originated as sinters deposited by hot-spring activity. Chert comprises 4.20 m of the cored succession, with the thickest bed, representing a single silicification event, being 0.31 m thick and the thickest composite chert (comprising six beds) 0.76 m thick. Average chert bed thickness is 80 mm. Forty-five plant-bearing chert beds are interbedded with sandstones, mudstones and shales. The sediments were deposited on an alluvial plain with local lakes, the area being periodically affected by hot-spring activity. Plants initially colonized both subaerial sand and sinter surfaces. Rhynia gwynne-vaughanii and Horneophyton lignieri commonly form the basal parts of the profiles with subsequent colonization by other genera. Rhynia is commonly found in life position above originally sandy substrates, and Horneophyton above sinter surfaces. The composition of the Rhynie vegetation is compared with coeval assemblages and, on the basis of current knowledge, it is concluded that there is no unequivocal evidence that the plants were adapted to life in the stressed environments in the immediate vicinity of hot springs.