Drill pipe is divided into three categories: kelly, drill pipe and weighted drill pipe. The connection sequence is kelly (1 piece) + drill pipe (n piece, determined by well depth) + weighted drill pipe (n piece, determined by drilling tool assembly design).
Kelly
The kelly is located at the top end of the drill string, and there are two types: square and hexagonal.
effect
①When drilling, the kelly is matched with the compensation center and the rotary table compensation center, and the ground rotation torque is transmitted to the drill pipe, so as to drive the drill string and the drill bit to rotate;
② Bear the full weight of the drill string;
③ Channels for drilling fluid circulation.