Atlantic Margin 3D Lab

New Geophysical Acquisition Technology

During the acquisition of the AM20 3D seismic survey, TGS tested two new geophysical acquisition technologies. The aim of the tests was twofold:

1. A new high-resolution streamer 3D technology optimized for small Deep Sea Mineral (DSM) targets close to the seafloor
2. The first free-fall seismic node test to examine ultra-long offset shots from the mother survey, AM20 Penta source 3D production.

The nodal data is currently being processed and a wide range of tests and analysis in complex volcanic rocks are planned for the finished data. 

The high resolution part for DSM targets was acquired using 10 separate small sources in 5 gun-strings where all 10 was fired with small dithers within 50 ms. Apparition Geoservices set up the gun solution for the semi-simultaneous shots. The shooting pattern was regular 8x12,5m giving many times the trace content per area than the Penta sources used on AM20 with pop interval 7,5m and 37,5m inline repetition.

The processed data from the Deca source line yielded superior resolution than the AM20 benchmark with contributing frequencies well above 250 Hz. In vertical section we can now interpret features down to 15-20m in size. As such this technology should fit finding small sulphide complexes (SMS - Seafloor Massive Sulfides) along the mid-oceanic ridges. Maybe even image internal structures. 

The second objective for the Deca test was to assess how much less sail line overlap is needed for targets basically on the seafloor. All streamer 3D acquisition until now is overlapping the spread 50%. Apparition Geoservices created an 80 cross line 3D made from the one Deca source sail line. The interpretation of spatial resolution and sharpness based on the 80 cross line 3D suggests results can be achieved with only 30% sail line overlap. This then means a fixed 20% acquisition time saving for the production 3D on DSM/SMS