Computer Models of Drillstring Friction
Proper evaluation of drillstring friction requires the use of a computer
program. These programs analyze drillstring friction for rotary drilling as
well as drilling with no drillstring rotation.
These mathematical models make a number of simplifying assumptions
and consider the drillstring as composed of discrete elements. Using these
models, it is possible to solve equations for the normal force of drillstring/
well bore contact at the bottom drillstring element, the friction force
deriving from that normal contact force, and the load condition at the upper
end of the drillstring element. Such methods, repeated for each drillstring
element over the length of the drillstring, yield the following information:
• Surface hookload and rotary torque
• Normal forces of drillstring/well bore contact at each drillstring
element
• Average torsional and tensile load acting upon each drillstring
element
Proper evaluation of drillstring friction requires the use of a computer
program. These programs analyze drillstring friction for rotary drilling as
well as drilling with no drillstring rotation.
These mathematical models make a number of simplifying assumptions
and consider the drillstring as composed of discrete elements. Using these
models, it is possible to solve equations for the normal force of drillstring/
well bore contact at the bottom drillstring element, the friction force
deriving from that normal contact force, and the load condition at the upper
end of the drillstring element. Such methods, repeated for each drillstring
element over the length of the drillstring, yield the following information:
• Surface hookload and rotary torque
• Normal forces of drillstring/well bore contact at each drillstring
element
• Average torsional and tensile load acting upon each drillstring
element
