Drill collar

• Drill collar in bottom of the drill string, is the BHA's main component. Drill collar's main feature is the wall thickness (usually 38~53mm or 4~6 times the pipe wall thickness), have greater weight and stiffness.
  2 drilling of Drill collar in the following main areas of action:
  (1) put weight on the bit;
  (2) ensure the necessary strength under compression;
  (3) to reduce vibration, oscillation, and the beating of the bit, make the drill work smoothly;
  (4) the control hole deviation.
  Drill collars generally divided into 3 types: spiral drill collars, non-magnetic drill collar, drill collars as a whole.
  (1) the overall drill collars for smooth, thick-walled pipes, processing threads at both ends.
  (2) the spiral drill collars in 3 round collar on the outer cylindrical surface machining the right-handed spiral groove, to reduce the contact area and wall, effectively preventing differential pressure sticking
  (3) non-magnetic drill collars are mainly used for oil drilling in the monitoring of the structure identical to the whole Drill collar. Non-magnetic drill collars are N1310 low carbon alloy steel and analysis of the chemical composition of the material is subject to stringent forged together. This material mechanical performance testing to ensure that shock value, and corrosion resistance, toughness and hardness standards, good and good machining properties of low permeability.
  In order to facilitate the work of tripping, you can drill collar thread slips and elevator recess Groove processing of outer surface.
  Implementation of the standards: SY5144-2007.API7-1