Because all packed assemblies will bend to some extent, however small the amount of deflection, it is not possible to make a perfectly vertical hole. The rate of hole angle change may be kept to a minimum for normal deviation but occasionally conditions will arise where the total hole deviation must be restricted to closer tolerances.
When this condition occurs the pendulum technique is employed, however if it is anticipated that a packed hole assembly will be required after reduction of the hole angle, the packed pendulum technique is recommended.
In the packed pendulum technique, a pendulum length of collars are slung below the regular packed hole assembly in combination. When hole deviation has been dropped to an acceptable limit, the pendulum collars are removed and the packed hole assembly is again run above the bit. It is then only necessary to ream the length of the hole equal to the length of the pendulum collars prior to resuming normal drilling.
If a vibration dampening device is used in the packed pendulum assembly, it should remain in its original pick-up position during the pendulum operations. (Refer to figure 8.f).
ENI S.p.A. Agip Division
Was this article helpful?