There has been a significant transformation in both reservoir management and infill well planning resulting directly from the application of 4D seismic across the Schiehallion field in the deep water United Kingdom. Atlantic Margin
Schiehallion has been now surveyed with two pre-production surveys (1993 &1996) and two post-production 3D surveys (1999 & 2000). The time lapse data has demonstrated large seismic amplitude and reservoir timing changes which can be related field production. The observed effects are attributable to the changes in pressure due to production and water injection. It has also shown where gas has been evolved around producers and has assisted the interpretation of hydraulic connectivity between producers and injectors.
In conjunction with reservoir simulation, the 4D has enabled 1) an improved understanding of the reservoir architecture. 2) production and injection strategy to be set by well, 3) the location and design of infill wells to be optimised and 4) a closer integration between the role of the geoscientist, reservoir and production engineer to be facilitated.
In a broader context, the Schiehallion 4D experience has helped BP to move the concept of 4D monitoring from R&D into the mainstream of reservoir surveillance and management. Consequently BP is in the process of acquiring up to seven 4D surveys across a range of fields in the UKCS during 2000 and 2001. Furthermore, an experiment is planned to test more frequent acquisition of 4D, on an oilfield adjacent to Schiehallion, using an array of permanent seabed sensors.
This paper describes the Schiehallion 4D seismic experience of using and summarises the steps being taken to apply it more widely.