Twenty-three years after BP discovered the Chiswick Field in 1984, first gas production was achieved by Venture Production. During its long period of appraisal and development, this asset has passed between five different operators and a large number of co-venturers. Prior to development, the field represented one of the largest undeveloped gas volumes present in the UK Southern North Sea. Key uncertainties include reservoir compartmentalization, low net/gross ratios and poor reservoir permeability, uncertainties in structural mapping and gas-water contact depths, as well as a widely varying Carboniferous subcrop and significant lateral changes in fluviatile sandstone architecture. Drilling and completion during the first phase of development were a significant challenge, with ambitious long and deep fracture-stimulated horizontal wells. The installation comprised a five-slot minimum facilities well-head platform with production tied back via the Venture-operated Markham J6A Platform with gas landed in Den Helder, Holland. As part of Phase II development a further three wells are being planned to accelerate recovery and access the remaining undeveloped reserves in both the primary Carboniferous and secondary Rotliegend reservoirs in the Chiswick Field.The Chiswick Field is located in block 49/4a, UK Southern North Sea (SNS), approximately 160 km NE of Great Yarmouth (Fig. 1). The reservoir is primarily of Upper Carboniferous Westphalian A and B age with Permian Rotliegend as a secondary reservoir target. The field is a slightly elongate faulted anticline lying on the same dominant Hercynian NW-SE trend as the Markham Field to the SE and the Ketch Field to the NW and covers an area of some 37 km 2 . The field is subdivided into five main fault compartments named Alpha, Beta, Gamma, Delta and Epsilon (Fig. 2). Depth to the top reservoir is around 3300 m TVDss at the crest of the structure and the volume of gas-in-place is estimated to be in the region of 600 BCF. BP discovered the field in 1984 with the well 49/4-1, which encountered gas within the Carboniferous Westphalian A and B channel sandstones.Chiswick remained one of the largest undeveloped gas accumulations in the SNS for more than 20 years predominantly as a consequence of the significant number of uncertainties associated with the field. Reservoir distribution is recognized as the primary uncertainty, particularly in undrilled fault blocks. The Carboniferous is erosionally truncated below the Hercynian unconformity; therefore, predicting whether Westphalian A or B reservoir is present at the subcrop away from well control is difficult and this is exacerbated by the channelized nature of the reservoir sands. The porosity and permeability of these sands is low and they are part of an overall low net to gross sequence. This introduces uncertainty with respect to the connectivity of individual channel sands and also in terms of production and the connection of sufficient quantities of sand to the wellbore to achieve economic flow rates. Further uncertainties...

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In the course of investigation of the causes of fluctuations in yield of the squeteague (Cynoscion regalis, Bloch & Schneider) in the Middle Atlantic States, a need for tagging experiments became apparent. The usual methods were not well adapted to the needs of the investigation, for the squeteague is so soft-fleshed and so weak-boned that tags of the usual designs are quickly lost. Moreover, the most pressing problems were concerned with the movements of squeteague of the "0" and 'T' age groups, comprising fish between 6 and 11 inches in length. These small fish were found to lose tags even more quickly than adults.Of a number of methods tested on fish confined in live cars, only one proved well adapted to the severe requirements of the problem. This method, first tested in August 1930, consists of insertion of printed and numbered strips of colored celluloid into the coelom, where they are found when the recaptured fish are cleaned. It was found in the live-car experiments that the wound healed quickly, usually within ten days, and that no inflamation or irritation of the viscera resulted. No mortality attributable to the operation occurred, for in all of the five experiments with three species, no deaths occurred within three months of the date of tagging, and fewer tagged fish than unmarked controls died subsequently. Two of the experiments were continued longer than a year, during which time no tags were lost and no internal irritation developed. In these experiments scup as small as 4", brook trout as small as 5", and squeteague as small as 8" were marked successfully.Encouraged by the results of the aquarium experiments, the method was tested further by release of marked squeteague, scup and cod at sea. Returns from these experiments have ranged between 1.5 and 10 percent and may be expected eventually to be somewhat greater, as recaptures are still being reported. In the squeteague experiments, fish as small as 6" have been tagged successfully as evidenced by their subsequent recapture.By means of this method it has been possible to demonstrate that "0" class squeteague at Montauk, New York, averaging 8" in length, migrate to southern waters during the winter. The following summer they appeared in the coastal waters of Virginia and New Jersey. Some difficulty has been experienced in securing adequate information concerning the locality and date of recapture of scup and squeteague, for these species are more frequently cleaned by deal-*Published by permission of the U.S.Commissioner of Fisheries.