Abstract The Hewett Field has been in production for some 50 years. Unusually for a Southern North Sea field in the UK Sector, there has been production from several different reservoirs and almost entirely from intervals younger than the principal Leman Sandstone Formation (LSF) reservoir in the basin. Some of these reservoirs are particular to the Hewett area. This reflects the location of the field at the basin margin bound by the Dowsing Fault Zone, which has influenced structural evolution, deposition and the migration of hydrocarbons. The principal reservoirs are the Permo-Triassic Hewett Sandstone (Lower Bunter), Triassic Bunter Sandstone Formation (BSF) (Upper Bunter) and Permian Zechsteinkalk Formation. There has also been minor production from the Permian Plattendolomit Formation and the LSF. Sour gas is present in the BSF only. Several phases of field development are recognized, ultimately comprising three wellhead platforms with production from 35 wells. Gas is exported onshore to Bacton, where the sour gas was also processed. Peak production was in 1976 and c. 3.5 tcf of gas has been recovered. Hewett has also provided the hub for six satellite fields which have produced a further 0.9 tcf of gas. It is expected that the asset will cease production in 2020.

Abstract The Hewett Fields complex, discovered in 1966, is located in the southwestern part of the Southern North Sea Basin. Gas is currently being produced from four horizons: Upper and Lower Bunter sandstones in the Triassic, Rotliegendes sandstones, and Zechstein dolomites in the Permian. Seven fields, containing a total of ten reservoirs, lie within the Hewett Unit and all have a NW-SE orientation. Gas flows, via two 30-inch (0.76 m) pipelines, to the ConocoPhillips-operated Bacton terminal, where onshore compression facilities are located. There are also compressors located on two platforms. Over 4 TCF (113 billion cubic metres) of gas has so far been produced in over 30 years of production.

Abstract Six satellite fields have been developed through the Hewett Field facilities: Big Dotty, Little Dotty, Deborah, Della, Dawn and Delilah. Little Dotty has produced from both the Leman Sandstone Formation (LSF) and Bunter Sandstone Formation (BSF) whilst the other satellites are exclusively LSF developments. The LSF reservoir quality exhibits a marked contrast across the Dowsing Fault Zone, which separates the inboard satellites to the SW from the outboard satellites to the NE. The inboard satellites, Big Dotty, Little Dotty and Dawn, display the best reservoir quality, reflecting their lesser depth of maximum burial. These fields share a strong aquifer, exhibited a rapid water-cut development and are now shut-in. The greater depth of maximum burial experienced by the outboard satellites, Deborah, Della and Delilah, is reflected in poorer reservoir quality along with weaker aquifers that are also more compartmentalized. These remain in production and will achieve higher recovery factors. Big Dotty was developed from a wellhead platform whereas the other fields were developed as subsea tie-backs. Collectively, these satellite fields have produced some 0.9 tcf of gas, playing an important strategic role in offsetting the production decline in the Hewett Field and extending the life of the asset.

Abstract Assemble at the Las Vegas Convention Center, south of the Hilton Hotel. Take any main street south to Tropicana Avenue. Turn west on Tropicana, past the Las Vegas Strip, and continue to Interstate Highway 15. Turn south on Interstate 15 toward Mountain Pass, California. Mileage starts at 0.0. 0.0 Tropicana exit on Interstate 15. Head south toward Mountain Pass. McCarran International Airport on the left. Spring Mountains on your right at 3:00. The impressive range is made up of thrust plates of the foreland fold and thrust belt (Armstrong and Oriel, 1965; Armstrong, 1968; Burchfiel and Davis, 1972). In the low morning sun the bold cliffs of the Aztec Sandstone are clearly visible. The Keystone thrust plate, consisting of dark Cambrian limestone and dolomite, overlies the Aztec Sandstone (Longwell and others, 1965; Burchfiel and others, 1974). Lower and presumably older thrust faults, which aren't very obvious from here, include the Red Springs thrust (Davis, 1973) and the Bird Spring thrust (Hewett, 1956). Behind and to your left, at approximately 7:00, is Frenchman Mountain, a titled and listrically rotated fault block containing most of the Paleozoic shelf sequence of carbonate rocks (Longwell and others, 1965). 2.9 Mountains at 9:00 are the northern end of the McCullough Range extending south from Henderson, Nevada (fig. 1). Northern part of the range consists predominantly of Tertiary volcanic rocks. View to the right in the Spring Mountains shows Keystone and older thrust plates. Strata in the thrust plates at 3:00 are relatively horizontal, but to