Tracking Seismic Anomalies - The Case for HRS 3D

In the North Sea, a subsea template was planned, and a standard integrated Site Survey was gathered to investigate for shallow hazards. The location was interpreted free of shallow gas and the template was installed. With several HRS 2D lines going over the location, the seismic coverage was good. The location was drilled and a small unexpected shallow gas pocket some 400m deep was discovered underneath the template. Simultaneously, a platform location was planned at the same field 20km away and a standard Site Survey was acquired here also. In light of the template incident it was considered that the best way to improve on the shallow gas assessment was to acquire HRS 3D data. We show the impressive mapping ability using HRS 3D data, along with the difference in anomaly identification between the 3D and 2D. The results of this survey fully justified the approach taken, as well as providing a lot more information about the site than had been expected. This study highlights the potential benefits that HRS 3D data bring in terms of anomaly identification and improved quality of data, along with the added freedom of being able to select any location within the entire 3D grid.