New GeoStreamer X data for exploration, ILX and appraisal in the Norwegian Sea

Geological Setting and Challenges in The Norwegian Sea

The Norwegian Sea is known for good-quality hydrocarbon reservoirs and complex geology. Tilted fault blocks created by Late Jurassic rifting host prolific pre-rift petroleum plays, which consist of high-quality Jurassic sandstone reservoirs in structural traps. However, improved seismic data has led to an increased focus on marine post-rift deep-water clastic systems and stratigraphic traps in the Cretaceous section. Increased interest on the Cretaceous section combined with exploration potential in undrilled Jurassic structures and potential within the Paleocene and Triassic makes the Norwegian Sea attractive for continued exploration.

Warka, 6507/2-6, Slagugle, and Iris/Hades are all recent discoveries that prove the considerable remaining potential in the Norwegian Sea. High-quality seismic data is key to overcome subsurface imaging challenges and provide an accurate representation of the subsurface. The overburden in the Norwegian Sea may seem simple at first. However, periods of subsidence, uplifting and erosion have resulted in an overburden characterized by high impedance contrasts, rough surfaces, complex velocities, and complex anisotropy. In addition, shallow glacial morphology generates strong noise and multiples, affecting not only shallow targets but deeper targets as well.

GeoStreamer X: Innovative Acquisition and Rich Azimuthal Coverage

The GeoStreamer X 2022 acquisition program in the Norwegian Sea encompasses an area of approximately 6 700 sq. km, with an azimuth orientation perpendicular to the existing GeoStreamer dataset acquired between 2011 and 2016. Together the state-of-the-art depth imaging and the reprocessing of the existing data creates a uniform and large-scale multi-azimuth dataset in the region.

The innovative GeoStreamer X configuration utilizes a wide-tow triple source setup that allows for denser sampling in the crossline direction, longer cables for improved Full Waveform Inversion (FWI), and streamers towed as closely as possible to the source arrays. In this case, the source array separation was 250 m between outer arrays, and the data was recorded with 14 streamers spaced at 75 m intervals (12x7 km and 2x10 km long).

This acquisition setup significantly improves the near-offset distribution and provides rich azimuthal coverage. This enables a step change in data quality in the Norwegian Sea, helping to solve remaining imaging challenges in, for example, complex overburden structures, but also in areas with weaker reflectivity such as the Cretaceous. It also reveals the deeper potential in the region.

A modern pre-processing sequence ensures seamless merging of all azimuths into a single dataset before Q Kirchhoff Pre-Stack Depth Migration (Q-KPSDM). The velocity model will be obtained through comprehensive Velocity Model Building (VMB), including the use of both refractions and reflections for FWI in a multi-azimuth setting. This is crucial for resolving both shallow and deep velocity anomalies, such as channels, shallow gas, or velocity variations at Cretaceous and Jurassic reservoir levels.