Accelerators
Accelerator, Intensifier, or Booster are different names for the same tool. An accelerator is used in conjunction with a jar in the string to intensify the force generated by the jar. It is positioned above the jar separated by drill collars. Accelerators are also available in double-acting mode to match the jar action.
A compressible fluid and an effective sealing assembly in the accelerator make the intensifying action possible. It stores energy when put under strain and acts like a hydraulic spring by releasing the energy as the strain is removed. It becomes a handy tool in shallow intervals where the drill string is not too long. Using an accelerator in combination with a jar increases the chances of releasing a stuck string.
Accelerator helps in keeping the energy generated by the jarring impact from being lost up the hole. Without an accelerator, the drill string absorbs some of the impact force of the jar, which reduces its effectiveness, and the string is also subject to undesirable jarring shock loads. The jar accelerator combination is used to intensify the effect of the jar at any depth.