Drillstring Force Monitoring
Knowledge of the forces being applied to the BHA provides information on the energy transfer from the surface to the bit and the dynamic response of the BHA as a result of those forces. Drillstring force measurements of tension, compression and torsion are made using strain gauges and from these measurements the bending moment of the MWD collar is derived. An azimuthal capability also allows the bend direction to be determined. The measurements allow the determination of the actual weight and torque being applied to the bit which is critical in high angle and extended reach wells to ensure optimum bit and hole enlargement performance and prevent drillstring buckling. Knowledge of the weight and torque transmission also provides information on hole cleaning effectiveness. Dynamic BHA forces are measured to prevent stress overload and premature failure of downhole equipment and when these measurements are combined with vibration measurements they provide the necessary information to fully characterize downhole drilling dynamics.