Abstract The Crosby Warren Field is located onshore the UK, south of the Humber Estuary. It was discovered by RTZ Oil & Gas with the CW-1 (L46/12-3) well in 1986. The oil reservoir is Carboniferous, Namurian, Beacon Hill Flags sandstone, with gas found in Namurian sandstones of the Rough Rock, and the discovery well originally flowed waxy 40° API oil at rates of 45 bopd, which increased to nearly 700 bopd following fracture stimulation. The Beacon Hill Flags are a 10 m-thick group of laminated sandstones within a substantial gross thickness of sandstones, silts, muds and occasional thin claystones. The expected ultimate recovery for the field will be about 0.9 MMbbl of oil and 0.7 bcf of gas. Almost all of the oil and gas have already been recovered, and end of life for the field is expected to be in 2022.

Abstract The Cavendish Field is located in UK Continental Shelf Block 43/19a on the northern margin of the Outer Silverpit Basin of the Southern North Sea, 87 miles (140 km) NE of the Lincolnshire coast in a water depth of 62 ft (18.9 m). The Cavendish Field is a gas field in the upper Carboniferous Namurian C (Millstone Grit Formation) and Westphalian A (Caister Coal Formation) strata. It was discovered in 1989 by Britoil-operated well 43/19-1. Production started in 2007 and ceased in 2018. Gas initially in place was 184 bcf and at end of field life 98 bcf had been produced. The field was developed by three wells drilled through the normally unmanned platform into fluvio-deltaic sandstone intervals that had sufficiently good reservoir quality to be effective reservoirs. The majority of the formation within closure comprises mudstones, siltstones and low permeability, non-reservoir-quality feldspathic sandstones. The quality of the reservoir is variable and is controlled by grain size, feldspar content and diagenesis. The field is a structural trap, sealed by a combination of intra-Carboniferous mudstones and a thick sequence of Permian mudstones and evaporites.

Abstract The abandoned Juliet gas field is a small, highly compartmentalized, accumulation situated south and east of the Amethyst Gas Field. It was discovered in 2008 by well 47/14b-10 and flowed first gas on 5 January 2014. The field consists of at least two culminations within a very low-relief east–west-orientated fault-bounded anticline. The reservoir comprises aeolian sandstones of the Permian, Rotliegend Group, Leman Sandstone Formation. Reservoir quality varies from good to moderate, with a high production rate achieved from horizontal wells. Seismic time-to-depth conversion is affected by Quaternary seabed channels, chalk burial history and a rapid thickening in the Basalanhydrit Formation located over the east of the field, associated with the edge of the Zechstein Basin. Gas-in-place at pre-development was expected to be 105 bcf, with reserves of 67 bcf. The field was developed using two horizontal wells and a subsea tie-back to the Pickerill Field, 22 km to the east. Since development, the field appears to be more compartmentalized than initially expected.