Insight will dynamically convert from time to depth and depth to time if you provide appropriate velocity information.
This is really awesome for anyone who needs to quickly move between domains without duplicating data.
Velocity is required in the form of either a 2D or 3D volume for the conversion.
Velocity can be imported as SEG-Y or generated using some of the many processes available within Insight.
To check your velocity data, you can view it in section, slice or 3D view as you would any other trace volume.
Here are some example velocity volumes previously created using stack derived velocity, interpolated well velocity, and various synthetic velocity models.
These examples show a lot of variation and so for accurate results it is important to use the best model which is ultimately determined by the data you have to work with.
Using groups I can overlay the velocity on the seismic for better QC.
I will select the stack derived velocities for the next step.
Configuring Insight for conversion is really easy, select File > Configure Time/Depth conversion Select the velocity volume and confirm the velocity type is correct.
Note that you can store velocity in several formats; Interval, RMS, Average and Depth values sampled in Time referred to by Insight as ZT.
Check the velocity units and close the window.
Dynamic time-depth conversion is now active. That's right! It really is that easy!
To see the effect in any view, look for the domain selector in the top left of the navigation bar, toggle from TWT to TVDSS and just look how super speedy the conversion is!
In map view the domain selector is for seismic data. Horizon has its own independent conversion through the property drop down.
To keep you in control, Insight does not automatically extrapolate the velocity traces.
This means that although a 2D velocity volume can be used for time depth conversion in a section,
it will only work at the 2D line locations for a regional horizon map.
For example, here is a 2D section.
The line has a 2D velocity volume associated with it and so once that velocity is configured it can be freely converted from time to depth.
In the map view the 2D time horizon is now interpolated & extrapolated across an XY grid.
When depth converted using the same 2D velocity, only the horizon coincident with the 2D survey is converted.
To perform full map conversion for all 2D and 3D horizon and trace data
you will need to build a 3D velocity volume or use a volume interpolate / extrapolate process to fill the gaps between the 2D lines.
For this example, it's easy to update the process to use the interpolated horizon, and output the model to a 3D geometry instead of 2D.
A regional 3D model has significantly more trace locations than 2D data and so don't forget to adjust the output spacing appropriately.
We recommend using a minimum spacing of 100m x 100m x 24ms (or 20m in depth) when using velocity data unless there is a strong reason for more density.
Large regional 2D surveys should consider increasing this spacing further such as the 1000m by 1000m used here.
If you need to down sample, use the velocity conversion process to ensure the output volume is equivalent to the input.
The recommended minimum spacing will give the best performance when converting.
Configure the Time depth conversion with the updated model.
The full horizon now converts as required.
Not only do the views make use of an active model, other objects are affected too;
Interpretation data objects are converted - horizon, faults, polygons as you have seen in the map example.
To make the depth horizon permanent, save as a custom property.
Setting the output to the input is another way to make the depth horizon permanent.
Volume & interpretation data can be exported in a different domain.
Simply select the required domain on the export dialogue.
Wells are always displayed using the time depth tables and are independent to the velocity model selected.
At any time you can display the time depth tables as a log or density display for a direct comparison with the model.
Even better, for a more direct analysis, the synthetic module can be used to extract the velocity model at the well location for display and to save it as a Time Depth table.
Look out for our other informational videos on building and manipulating velocity models.