E&P 3D Seismic as a Tool for Shallow Hazards Detection

By

 M. Buia¹, K. Buonomo¹, P. Cibin¹, P. Marchetti¹, O. Tarchi¹

(1) ENI SpA - Agip Division, s. Donato Milanese, Italy

 In deep and ultra-deep water the use of an E&P 3D is a cost saving alternative to a traditional well site survey. Conventionally processed 3D seismic cubes are often inadequate for detecting the features generating hazards and so a special reprocessing is needed for increasin g their overall frequency content and consequently the vertical detail; also spatial resolution is improved using bin interpolation. Once achieved the necessary quality in the seismic data, the following 3D cubes are produced:

1) Migrated seismic volume: it is used for detailed seismic stratigraphy and shallow layering definition; potentially dangerous levels or objects are here identified as function of amplitude, geometry and structural features. Water bottom bathymetry is also produced.

2) Velocity cube: it is used to for the depth conversion of the previously defined layers and for pore pressure prediction.

3) Pressure cube: it is calculated from the above velocities and gives the pore pressure development along well trajectory

4) Continuity cube: it is necessary for a very detailed geometrical characterisation of the potentially hazardous features. From the continuity cube the geomorphology of the sea bottom is usually extracted.

5) Acoustic inversion cube: it is used for lithology and fluid prediction in the investigated levels The final result of the studies performed on a E&P 3D survey is the production of a tophole prognosis chart that identify both the hazard percentage and the pressure development as a function of depth.