Hill, M.G.; Milner, M. 2012 The Kupe velocity model - 4D Taranaki Project. Lower Hutt, N.Z.: GNS Science. GNS Science report 2012/37 39 p.
Abstract: The Kupe mapping area (KUP) is the first of seven offshore regions within the Taranaki Basin to be seismically mapped as part of the GNS Science 4D-Taranaki (4DT) Project. Seventeen horizons were interpreted throughout the region. Here we present the velocity model used to depth convert the 4DT seismic interpretation within the KUP area. Constant velocities are used for five layers including the water column and basement. All other layers, six in total, used a ‘V0 / k’ method, where V0 represents velocity at the top of a layer, and k represents the velocity gradient within a layer. Layer velocities were clipped at a maximum of either 4000 or 5000 metres per second (m/s) so that thick layers did not have unrealistically high velocities. The velocity model is represented as a voxet (3D cellular cube) with 1 km x 1 km x 100 millisecond (ms) cells that contain an average velocity attribute that is used for time-depth conversion. A comparison between the depths of horizons calculated by the model and depths derived from the local well model (calibrated two-way time (TWT) / Depth curve) in the Kupe region indicates mean differences of between 10 and 20 m with the minimum value of 1.85 m (seabed) and maximum value of 57.5 m (K90 at Tahi-1). The 4DT model predicts a thicker sedimentary sequence than that previously modelled by Thrasher et al (1995) for the Kupe Region. The Top Cretaceous surface is up to 2.5 km deeper on the western side of the Manaia Fault, and up to 1.7 km deeper on the eastern side. The velocity model is provided by GNS Science in Fohrmann et al. (2012a), in both ASCII and SEGY formats, for both time and depth domains. (auth)
