Boring Stabilization (PDF)
Why stabilize? In rotary borings, drill string and bit stabilization is necessary to drill a plumb boring. Stabilization occurs by utilizing specially designed tools within the drill string combined with operator expertise when applying bit weight. An improperly stabilized drill string can result in excessive bit and tooling wear, borehole deviation, and stuck tooling.
Drill collars are designed to keep the entire drill string in tension, thus improving the performance of the drill bit by helping ensure the drill bit has equal distribution of cutting action on each cone. The combined weight of the collars in a drill string should equal the weight necessary to produce all load required at the bit, plus additional weight to ensure the drill string remains in tension. A drill string operating in tension is held in a relatively straight pendulum manner, minimizing the bending and wear that occur when a drill string is operated in compression.