Loss of Overbalance Due to Pipe Pull Out and Falling Mud Level

When pulling pipe out of a wellbore, the hydrostatic pressure decreases due to the volume of steel being removed from the hole.

The wet pipe is when filled with mud, while the dry pipe system is when only the volume of steel is encountered and the fluid inside the pipe is assumed to be air.

In this page, the user can determine the length of drilling pipe that must be pulled out of hole to lose certain amount of overbalance.