What are Drilling Jars?

Most modern drilling jars are hydraulic. They are also usually double acting, meaning they can deliver an extra-heavy impact should the bottom hole assembly become stuck. They are intended to work as an integral part of the drill string, and can withstand high pressures and temperatures over a long period of time, making them suitable for long-term use.

With almost the same length and diameter specifications as standard drill collars, and with a similar connection strength and slip setting area, they may be used as a component of a stand of drill collars without difficulty.

Usually, jars will be used alongside accelerators, which are run above the jar and work automatically. They serve to amplify the impact force of the jar, and can even double it in some cases. They commonly use the compression of silicon to give added stored energy and optimize jar impact and free-travel distance in both directions. They also have the added benefit of dampening the dynamic load in the drillpipe, since they transmit shock waves poorly, thus helping reduce damage to both string and surface equipment.

Drilling Jars Diagram (Slideshare, 2017)

Drilling Jars Diagram (Slideshare, 2017)

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Drilling Jar and Accelerator (Fishing Tools) Video

A drilling jar is used to increase pulling capacity to free the stuck pipe and an accelerator is used to intensify force generated by the drilling jar at the upper depth of the well.

This video demonstrates how a drilling jar and an accelerator are activated to free the stuck pipe.

Summary from this video

• The more you pull on the drilling jar before it is tripped, the more power you will get from the drilling jar.
• Drill collars placed above the drilling jar enhance the performance of the hydraulic jar.
• The jar accelerator is used to intensify effect of jar at any depth. Use of the accelerator is very effective in a shallow fishing operation.
• The accelerator helps keep the energy generated by jar impact from being lost up hole.
If you cannot see the video for some reasons, please check out this link http://youtu.be/w-9gd2eeibc.

I wish you would enjoy learning about the drilling jar and the accelerator.