The records studied from tests made by Esso Production Research Company confirm and give quantitative values to many phenomena which have been observed qualitatively or which have been indicated by existing evidence. Phenomena that were distinctly shown to exist in some cases are irregular bit rotation, torque fluctuations, bit bouncing, bit weight fluctuations, and large losses of rotary horsepower along the drill stem. In many cases, weight fluctuations appear to be excited by either the rotation of the drill stem or the mud-pump pressure fluctuations, or both. In at least one case, these fluctuations resulted in the bit bouncing clear of the hole bottom.

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