Image processing of interpreted 3D seismic data to enhance subtle structural features/lineations

With the ever increasing number of 3D surveys being acquired, it is essential that 3D interpretation be both effective and efficient to ensure that maximum information is derived from the data. In this context, Woodside has put considerable effort into the development and application of novel techniques in seismic interpretation over recent years to assist in the optimal interpretation of its existing and planned 3D seismic data sets. These studies have included comprehensive analysis of seismic horizon attributes, coupled with the application of image processing techniques, to enhance subtle features not readily discernible by other means.

Image processing, commonly applied in mineral exploration to enhance Landsat images and potential field data, has been applied to interpreted seismic horizons from 3D data sets with outstanding results. Two aspects of image processing which have been utilised with good effect are data illumination and combined displays.

The illumination technique involves artificially illuminating the horizon by a ‘sun’ and varying the ‘sun’ angle (azimuth and elevation). This tends to enhance features normal to the ‘sun’ direction. Combined displays have allowed the integration of different attributes onto one map using both a black/white scale and an overlay colour scale.

Application of these techniques in the Goodwyn South/Tidepole area has provided new insights into the nature of subtle features of the seismic data. For example small faults, barely discernible using conventional mapping techniques, are clearly revealed and can be traced with confidence along their strike. Moreover, the dip direction of these faults is readily apparent. In particular, the illumination and dip displays enhance the fault trends, while the azimuth displays combined with other attributes highlight the inter-relationship of faults and direction of fault throw. Integration of all these attributes/displays during interpretation has allowed a clearer understanding of this structurally complex region.

Potential also exists to highlight even more subtle features such as cuestas associated with the subcrop of resistant beds. This response was utilised recently to assist in targetting development wells in the North Rankin Field.

Further development and application of these image processing techniques, coupled with horizon attribute mapping (dip and azimuth) will result in more confident and better interpretations, and hence will assist the orderly and optimum development of Goodwyn and other fields during the 1990s.