Depth Datum Definitions

WinPICS will post your well tops and depth grids to your maps in elevation or depth below seismic datum.

You can set the map depths in the Map Preferences dialog box or from the Well Spot Database dialog box.

WinPICS uses two datums to help calculate depths.

Seismic datum

Seismic is in the time domain. Tops and well information are in the depth domain. The elevation of the seismic datum ties seismic times to the depth values.

Use the Set Seismic Datum dialog box to set the elevation and velocity for your seismic datum.

Time depth conversion

The only relevant datum in time depth conversion is the seismic datum. To generate a velocity, we need to divide a distance by a time.

The distance is calculated as the distance between the elevation value of the point of interest (a top), and the elevation of the seismic datum.

The seismic datum is defined as time 0 for all seismic sections in the project. The time is calculated as the difference between the time of the horizon and time 0.

The times captured in the calculation are normally two-way times. The average velocity calculation adjusts for this.
The replacement velocity is not used in a time to depth conversion. It is used only to let users estimate where to draw depth events, such as the start and end of logs, on the seismic.

Kelly Bushing Datum

The Kelly Bushing (KB) datum measures well depth. Well depth is initially in measured death (MD). WinPICS converts the MD to true vertical depth (TVD), by referencing the KB datum.

The drilling depth is TVD below KB.

If the well is vertical, then MD below KB is the same as TVD below KB.

To calculate the average velocity, WinPICS adds the TVD value to the difference between the seismic datum elevation and the KB elevation.

Examples

The following images shows examples of how WinPICS uses datums to calculate depths.

Please note the sign of depth value.
Deep example. View image

Deep example (datum below KB). View image

Shallow example. View image

What do you want to do?

Set the elevation and velocity for your seismic datum