# How can I create a simple velocity model for 2D data?

A velocity model can be constructed using Volume Maths (see *Volume Maths*). While the equation may be a little daunting, the result is very flexible. For 2D data, we will use stack data to define the output lines.

## Create a Volume Maths process

- In the
**Process**tab, click on the Add icon and select**New Process**. - Create a
**Volume Maths**process and type a**Name**for the process. - Click
**OK**.

- In the Details Panel, click the Add icon to add your 2D volume and horizon.
- Input the following formula:

`max((twt_ms - WB)/(9000-WB) * 4500 + 1500, 1500)`

(See below for a brief explanation of the equation.)

- Set the output extents as follows:
- TWT (ms), 0 - 9000 [24]

- The process should now yield a resulting volume in the
**Volume**tab.

## Set the class of the result volume to Velocity (Interval)

- Right-click on the
**Volume Maths**process and select**Open Child Volume**, or find the resulting volume directly from the**Volume**tab (the process volume should be in*Italics*). - Double click on the volume, or right click and select
**Configure Volume**. - In the
**Configure Volume**window, set the class of the resulting volume to**Velocity (Interval)**.

## A brief explanation of the equation

`max((twt_ms - WB)/(9000-WB) * 4500 + 1500, 1500)`

- max(result, 1500)
- The minimum velocity is 1500; only output the result if it is larger than 1500.

- (twt_ms - WB) / (9000-WB)
- The current time sample (twt_ms), as a fraction (0.0 to 1.0) between the water bottom and 9000ms.
- To scale between two horizons, add another horizon (symbol 'h2') and replace '9000' with 'h2'.

- (fraction * 4500) + 1500
- Calculate a velocity between 1500 and 6000, scaled by the fraction.
- The fraction is scaled by 4500.
- 4500 = 6000 - 1500
- (Scaling) = (the model maximum velocity) - (the model minimum velocity)

## Genuine offer of assistance

If you have any questions regarding the workflow, or if you need a variation of this process for a 3D model, don't hesitate to contact our support team at [email protected].