I have a question asked regarding what the differences between True Vertical Depth (TVD) and Measured Depth (MD). Today, I will describe both definitions and their importance for calculation in a drilling field.
True Vertical Depth (TVD) is measured vertically from the surface down to a certain target down hole.
Measured Depth (MD) is the total length of the wellbore measured along the actual well path.
See the following illustration for more understanding.
True Vertical Depth (TVD) is used for following calculations:
Measured Depth (MD) is used for following calculations:
Well control as stokes pump in the drill string and in the annulus, pressure schedule for wait and weight method well control.