NPD study of seismic data from the northern North Sea

The Norwegian Petroleum Directorate (NPD) has analysed all seismic data acquisitions in the area 60 – 62 degrees north from the period 1998 – 2007. The purpose of this work is to determine the degree of potential overlapping seismic surveys in the same area, and the reasons for this.

The acquisition of seismic data on the Norwegian shelf has received more and more attention in recent years, in part due to the increased activity in the petroleum sector. From a fishery perspective, there is a perception of a higher level of conflict between fishing boats and seismic acquisition vessels. It has been claimed that seismic data is acquired repeatedly within the same area. According to the fishermen, this relates particularly to the northern part of the North Sea, in the area 60 – 62 degrees north.

There has been significant acquisition of seismic data in the area between 60 degrees - 62 degrees north. Because this is considered a mature area, there have been few 2D seismic acquisitions during the period 1998-2007, while there have been many 3D surveys (a total of 49 over ten years). These are mainly connected to the large field areas Tampen, Oseberg and Troll, where there have been several seismic acquisitions in the same areas.

The NPD cannot see that there is a basis for saying that seismic data has been acquired repeatedly and in overlapping areas in the sense that this is supposedly unnecessary or could be done more efficiently. Repeated data acquisition over the same field is often done for the purpose of monitoring the reservoir ("4D seismic”) to achieve the best possible recovery. This is the case, for example, on Troll Vest and over the Gullfaks field, which has the most coinciding seismic areas.

Other reasons for coinciding seismic acquisition areas can include new geological problems and new technology.

The licensees have operated the fields for several years, and they have good knowledge about the existing seismic data. Therefore, they have no interest in acquiring new seismic data unless it is deemed necessary.

One reason that the fishermen may experience conflicts in these areas is that the areas that are proposed for seismic surveys are larger than the actual acquisition areas. The NPD has begun work to get the companies to apply for more realistic areas and to provide better information about planned surveys.

Topics: Seismic