High-Strength Drill Collar for Drill String Wellbore Stability

Drill Collars are integral heavy-wall joints that are manufactured from a solid bar of modified alloy steel. The solid bars are quenched and tempered to obtain the required mechanical properties, then trepanned, drifted and threaded. All drill collars are heat-treated with hardness within 285 to 341 BHN, which are guaranteed one inch below the surface of the pipe.  It consists of 3 types below:

1. Slick Drill Collar, mainly used to provide bit weight to drill bit so that drill pipe is in tension. Especially drill collar can keep drill bit centralized and hole track by large rigidity.

2. Spiral Drill Collar, used to reduce contact area with hole so as to avoid efficiently bit sticking from diffirential
pressure.

3. Spiral Drill Collar With Elevator Groove And Slip Groove. Elevator groove and slip groove made on box thread face of slick drill collar or spiral drill collar can be used as lifting
sub and safety slip when trip out.

4. Non-magnetic Drill Collar, both inner and out surface with unique technical process, which  strengthen the structure and ensures the tools with optimal resistance to stress,corrosion,cracking and the mechanical performance is greatly enganced.