دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a drill collar with a round cross section that has a long continuous groove or flute machined helically into its outer surface. The spiraled groove provides space between the wall of the hole and the body of the collar, minimizing the area of contact between the hole wall and the collar;thus the possibility of differential pressure sticking is reduced.