On the development of high-frequency torsional impact drilling techniques for hard formation drilling

Abstract

Stick-slip vibration is a big problem that the drilling of deep wells has to face, especially for drilling of tough formations. This type of vibration leads to failure problems, reduces the rate of penetration, and lowers the borehole quality. Suppression techniques for stick-slip vibration, for example, active control method based on real-time measurement, play important roles in improving the drilling efficiency. The high-frequency torsional impact drilling, however, provides a cheaper and more stable way to mitigate stick-slip in many conditions. This work is aimed to study the high-frequency torsional impact generator, which is used to achieve the function, for this new technique. First, state-of-the-art of high-frequency torsional impact generator is studied by schematically illustrating the existing four structures and their operating principles, followed by comments for these structures. Second, theoretical background of the high-frequency torsional impact drilling is presented, showing how the high-frequency torsional impact generator works to mitigate stick-slip and improve drilling efficiency. Finally, an optimally designed high-frequency torsional impact generator is schematically described. It is an improved version of the assembly of United Diamond and the improvements are based on results of a series of laboratory experiments.