Abstract Hydrocarbon exploration in North Yorkshire began in 1937, targeting Triassic and Permian reservoirs below the surface expression of the Cleveland Anticline. D’Arcy drilled the successful well Eskdale-2, marking the first gas discovery in the Zechstein carbonates in the UK. Since then approximately 100 wells have been drilled in the basin with exploration success relatively high. Out of the 25 pure exploration wells in the region, 13 have found hydrocarbon accumulations (flowed gas) and eight of the discoveries have been developed to date. The primary reservoir is the Permian-aged Zechstein carbonate sequence and, more specifically, the Z2, Kirkham Abbey Formation (KAF), which is a tight carbonate reservoir overprinted by a high permeability fracture system. Despite considerable investment and effort over the years, the historical development story of these fields has been very much one of repeated technical and investment failure, with approximately 39 Bcf (billion cubic feet) of the mapped gas initial in-place (GIIP) of c . 326 Bcf produced to date, an estimated recovery factor of 12%. Historical production data show that all the Zechstein reservoirs have experienced early water breakthrough, leading to impaired gas rates and low recoveries. The water influx is due to a highly mobile, but finite aquifer, which under field production conditions preferentially flows through the high permeability fracture system, bypassing the gas stored in the tighter matrix. Third Energy is aiming to resolve the issue of water influx by using artificial lift to encourage the gas to flow. A trial is currently being undertaken at the Pickering gas field and, if this programme is successful, this will provide sufficient confidence for a phased redevelopment programme of surrounding fields. Whilst North Yorkshire has experienced only limited exploration and production (E&P) activity in the last decade, solving the issue of premature water influx in the KAF fields, combined with the search for unconventional resources in the Bowland section of the Mid and Lower Carboniferous strata will herald a new and exciting phase of E&P activities for this province.

Abstract The Armada development comprises three gas-condensate fields in the Central North Sea: Fleming (Paleocene Maureen Formation reservoir), Drake and Hawkins (Upper Jurassic Fulmar Formation reservoirs). Armada came on stream in 1997, with seven PhaseI wells producing at a plateau rate of 450 × 10 6 SCFD. APhase II drilling campaign, comprising three Armada wells, was implemented in 2002 with the aim of extending the duration of the Armada production plateau and, where possible, accessing new reserves. The first well was a relatively straightforward Paleocene Maureen Formation producer, although the target was revised based on a new seismic attribute study, which revealed important heterogeneities in this deep-marine reservoir. The second well targeted the undrilled western compartment of the Hawkins discovery. Unfortunately, the Fulmar Formation was water-wet with no evidence for any hydrocarbon charge, despite the fact that gas had been proved by an earlier exploration well in a downdip compartment. Fortunately, to mitigate the risks, which had been recognized pre-drill, the well had been designed with a secondary Paleocene Maureen Formation target which came in better than prognosed. A significant aspect of the Armada Phase II programme was the extensive integration across a number of disciplines. The combined team was soon able to propose a convincing explanation for the failure of West Hawkins, giving comfort that East Hawkins should be fully charged and was worth drilling. The final Phase II well was therefore targeted on East Hawkins, although it was a difficult well to plan as the key reservoir horizon had only minor stand-off from the gas-water contact. A number of different well trajectories were considered and 3D visualization proved invaluable in ensuring the final well path was optimized. In addition, a major benefit was derived from a recently installed onsite 3D visualization centre that enabled the multidisciplinary Armada team to work together very effectively. For example, the drilling engineers were truly able to appreciate what was driving the geotechnical requirements for the well and vice versa. The well came in very close to prognosis, adding valuable reserves and further extending the Armada plateau. With a rig on the Armada platform the opportunity was taken to drill the South West Seymour prospect, whose chance of success had increased dramatically after a possible direct hydrocarbon indicator was recognized on an inverted seismic volume. The well discovered hydrocarbons in the primary target, the Fulmar Formation and also in the Pentland Formation and was immediately side-tracked to a previously planned updip Fulmar development location.

Abstract The Precambrian rocks on either side of Davis Strait show a similar pattern of events and are interpreted as having formed part of a single shield. Nine major stages in the development of this shield are suggested: (1) formation of an extensive early crust before 3,000 m.y. ago, relicts of which are now preserved as migmatites and high-grade gneisses in the Archean block of eastern Labrador and southwest Greenland; (2) de-position of greenstone belts 2,700-3,000 m.y. ago; (3) plutonic activity in the period 2,500-2,900 m.y. ago, affecting both the greenstone belts and the major parts of the basement on which the greenstones lie; (4) in-trusion of numerous basic dike swarms in the general period 2,000-2,600 m.y. ago; (5) deposition of early Proterozoic (Aphebian) géosynclinal rocks on the consolidated Archean basement; (6) alteration of these rocks by orogenesis which occurred approximately 1,650-1,850 m.y. ago (the Hudsonian orogeny in Canada and the Ketilidian and Nagssugtoqidian orogenies in Greenland); (7) post-orogenic magmatism-particularly marked in areas affected by Hudsonian metamorphism-which extended from South Greenland through Labrador (This magmatism produced chiefly anorthosites, adamellitic granites, monzonites, and norites, which probably were emplaced between 1,400 and 1,700 m.y. ago, although the areas in which they occur commonly remained thermally active to 1,200 m.y. ago or later.); (8) graben faulting, deposition of molasse sediments, and widespread intrusion of basic dikes, in South Greenland and in parts of Baffin Island, accompanying and following emplacement of the post-orogenic rocks (Most of these dikes are tholeiitic; however, alkalic and peralkalic intrusions took place locally 1,100-1,300 m.y. ago.); (9) metamorphism and tectonic alteration of the Archean and Proterozoic rocks in the southern part of the Canadian shield by the Grenville orogeny about 900-1,100 m.y. ago. The only effect of the Grenville orogeny in South Greenland was a weak updating of older rocks in areas close to major faults, so that they yield K-Ar ages of about 900-1,000 m.y.