The hydraulic jar is a safety tool for the drill stem testing operation, The Hydraulic Jar is used to provide an upward shock to helps free a stuck tool by resisting a pull on the workstring , when equipment becomes stuck in the well bore.

At the end of the stroke, the restriction is removed causing the mandrel to move rapidly upward, resulting in a sudden impact to help free the stuck tools. If the tools are not free, a downward stroke resets the Hydraulic Jar for the next attempt.

Operation of the Hydraulic Jar

The temporary resistance that powers the hydraulic jar is provided by a hydraulic time-delay system. Resistance is released when the metering sleeve inside the jar moves into a bypass section of the outer case. This action allows the special hydraulic oil to bypass rapidly.

The time delay required to release the temporary resistance varies in relation to the weight of the pull. For example, a light pull requires more time for release than a hard pull. When tools below the jar are stuck, a steady pull applied to the jar creates an upward impact blow to the string. The jar can be re-cocked when the string is set down.

Application of the Hydraulic Jar

* Cased Hole Drill stem testing Operation

* Tubing – converyed perforating operation – TCP operation

* Oil well flow operations

Features and Benefits of Hydraulic Jar

• Design of the hydraulic system ensures long life with little maintenance.

• To reduce the rig time

• Jar can be re-cocked rapidly.

• The hydraulic jars are able to adjust the time delay

• Amount of pull to trip the jar can be varied within the limits of the time-delay system.