First production from the Viking Fields began in 1972 and at its peak a total of 13 platforms produced at rates up to 950 MMSCF/D from 20 wells. This supplied around 10% of the United Kingdom’s natural gas requirements, 27 years on, that rate had declined to approximately 40 MMSCF/D. However following an extremely successfulinfield drilling programme in the mid 1990s, significant volumes of new gas have been discovered and new technology has facilitated the development of accumulations previously considered non-commercial. This has led to threenew developments within the Viking area: the Vampire Field on the eastern margin; Kx to the south of the Philips’ Alison Field; and four previously non-producing fields, captured within the Phoenix Development.
The major change since Morgan (1991) has primarily been the re-negotiation of the gas sales contract and the removal of the Gas Levy in 1992. This provided favourable marketing conditions for the development of additionalViking gas production and initiated an appraisal programme for remaining reserves. This programme, which will bethe focus of this paper, began with the acquisition of a 3D seismic survey in 1993 and has concluded in the development of the Viking Extensions in 1998, now known as the Phoenix Development.
The Leman Sandstone Formation forms the reservoir and consists of aeolian and fluvial sandstones, which are interbedded in the north of the area with silty shales deposited within a sabkha environment. Hydrocarbons were sourced from the underlying Carboniferous Westphalian coals and carbonaceous shales, and migration into the Rotliegendes Group probably occurred during the Late Cretaceous to Early Tertiary.
The average daily production from the original Viking A and B fields and associated satellites had declined to 196 MMSCF/D by March 1989, peaking to over 300 MMSCF/D with seasonal demand. By October 1999, this had furtherreduced to around 40 MMSCF/D. Production from the Phoenix wells is currently at around 290 MMSCF/D, with furtherdevelopment wells planned. Cumulative production to date is approximately 2880 BCF.