Adjustable Kick Off Sub
AKO (Adjustable Kick Off) sub or Bent Sub is a small segment of the drill string which is tilted at an angle rather than being straight. It is run above the bit and below the power section in the drill string and is used for drilling directional well or for kicking off from a vertical well. Running the AKO sub in the string makes it possible to steer the well as needed through sliding. The tilt of the sub depends on tool size, hole size, and DLS (Dog Leg Severity) requirement.