Drill Collar Boring and Straightness Requirements
Why Straightness Matters in Drill Collars Drill collars are thick-walled tubes used in oil and gas drilling strings. They need a through-bore for drilling fluid circulation. The bores are typically 50-100mm in diameter through 6-10 meters of length. The straightness requirement is about 0.5mm per meter maximum. I have seen what happens when a drill collar exceeds this spec — the eccentric mass causes vibration in the drilling string that accelerates tool joint wear and can lead to down-hole tool failure. ...