The HWDP's uses AISI 4145H alloy structural steel, the technique of production exactly carries on the SY/T5146-1997 standard, HWDP is one kind of medium weight and the drill pipe similar drilling tool, its wall thickness is thicker than the drill pipe, is thinner than the drill collar, on its thick wall body connected special and lengthen drilling joint. Generally adds between the drill pipe and the drill collar, prevents to drilling string's sudden change, reduces drill pipe's weariness; Uses in the directional well, might in compare the low torque in the situation to sneak in high speed, reduces drilling string 's attrition and the breakage. Because its rigidity are less than the drill collar, less contact area with wall of a well , is also not easy to form differential pressure sticking.
