VelPAK’s HiDef module adds log-level detail to existing velocity volumes. You can easily input your background model, change the fill-type to suit the geology, whilst conforming the velocities with the background trend. The output provides an ideal input for Pore Pressure Prediction, Reservoir Characterisation and Seismic Inversion and removes the depth uncertainty.
HiDef generates highly detailed velocity volumes from background velocity modelling, well velocity logs and geological interpretation. Well log velocities are propagated in a volume consistent with geological and interval velocity constraints, tying the volume to well tops. It produces a sophisticated, high definition velocity model that can be used for depth conversion, in addition to attribute analysis, reservoir characterisation studies and input for seismic inversion packages. Detailed instantaneous and average velocity volumes are then generated.
It is not necessary to have generated a full VelPAK model in order to run HiDef. The input background velocity volume is ideally instantaneous velocity volume generated by VelPAK; the instantaneous velocity volume captures velocity gradients correctly, for example, a simple increase of velocity with depth or unusually high velocities due to uplift etc. A simple interval velocity from Kingdom Advanced Dynamic Depth conversion or a seismic processing interval velocity volume may also be used, which may or may not contain velocity gradients within the layer.
For each layer, the well velocity log data is de-trended. For each log sample in the layer for each well, 3D Kriging is used to propagate residual scalars using the background model trend, applying structural constraints defined for each layer in the geological model. If log data is not available for a well in a particular layer (usually the deepest layers), the background velocity is used. The geological behaviour of each layer is defined by assigning each layer one of three spread types: Cut from Top, Cut from Base or Stretched and Squeezed. When the process is run the layers are flattened onto a datum, processed and then returned to the original layer structure.
Watch the short video on the HiDef module below.