100 4D Surveys: Adventures and Misadventures

Abstract Dynamic reservoir monitoring using seismic data is now a common practice, but when BP North Sea first embarked on this in 1992 using streamer data over Magnus streamer, it was very much stepping into the unknown, with a hope of meeting our pioneering objective of monitoring a significant pressure signal; and if successful, understand what levels of change we could monitor. This was followed up in 1995 with the first permanent array over Foinaven (FARM - Foinaven Active Reservoir Monitoring) which acquired a monitor survey in 1998. A streamer survey soon followed in 1999 which matched the existing 3D of 1993 and resulted in the first large at scale 4D project to investigate. After those initial experiments, no one could have envisaged the level to which the industry has now applied the technology. Since that time BP has acquired over 100 4D monitor surveys over a variety of fields in the North Sea. The 4D experience covers a wide variety of geological settings, from a hard concrete like sea bottom at Clair, to a relatively soft sea bottom at Valhall, from flat sea floor to dipping (Schiehallion) or even rugose (Skarv). We have gained a great deal of experience of both towed streamer and OBS 4D, in some areas it has worked particularly well, and in others, less so, from strong to weak signals, amplitudes and time shifts. In this paper we give an overview of our experiences and where we see the direction of future applications.