Drillstring vibrations occur frequently during drilling operations. They can result in drillstring failure, fishing and, in the worst case, side tracking. At the same time, the rate of penetration and the bit/downhole tool longevity are reduced. All these effects of drillstring vibrations lead to substantial additional well cost.

An integrated approach towards vibration control, addressing all the contributing factors, can have a positive impact on well costs. This is especially true for hard rock drilling, as frequently occurring in Middle East countries. Various types of vibration can be distinguished, each having their own specific adverse effects. The integrated approach, developed in Shell, consists of the following elements:

  1. The application of a soft torque rotary system (electric and hydraulic rotary drives) for suppressing (torsional) stick slip vibration of BHA and bit.

  2. The use of vibration analysis software in the design of a BHA, to prevent buckling and to identify safe operating windows for rotary speed.

  3. The cost-effective deployment of vibration monitoring tools.

  4. The regular inspection of drillstring components.

Field cases of the deployment of this methodology reveal that twist-offs can be reduced by more than 80% and drilling performance in terms of ROP and bit life can be improved. Cost savings are realised through the reduction of well days and prevention of tool failures. A limitation of the method is that safe operating parameters are not available under all circumstances.

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