f Interval-velocity studies in the Southern North Sea

Interval velocities have been derived from a dense grid of non-exclusive seismic data in the Southern Gas Basin of the North Sea. The analysis of around 8000 velocity spectra has enabled detailed interval velocity maps to be drawn down to Top Zechstein level. A comparison of the seismically derived velocities with known well-derived velocities indicates that in most circumstances the "Dix" interval velocities are a good approximation to the well velocities - particularly for the Tertiary and Upper Cretaceous Chalk intervals. Consequently, the interval velocity maps so derived are useful for the purposes of depth conversion. In addition , these maps reveal interesting trends and anomalies many of which can be interpreted as having distinct geological causes. This poster paper concentrates on the interpretation of velocity anomalies in the Upper Cretaceous Chalk.