Torque on bottom & Torque off bottom of a drillstring

[offshore7024]

Please Help - I am stuck on this one. How do I calculate off-bottom and on-bottom torque on a drillstring? What is the equation for this?

The input I have are RPM, Pipe OD, Pipe Weight and Torque on Bit. Do I need any more inputs?

Please explain as much as you can. Many thanks in advance.

 

[DrillerNic]

Torque modelling is usually done with a computer simulation rather than a single equasion (the actual equasion is just weight * friction factor = force, really).

Other inputs you will need for most simulations are the well profile, the casing IDs, the hole ID, the casing friction factor and the open hole friction factor (these often change according to the drilling fluid you are using) and the drill string's stiffness (although some models account for differing stiffnesses by changing the friction factors).