Drilling jar which is connected with drill tool and worked with
drill string is a downhole unfreezing tool in drilling operation.
The drilling jar is consisting of ZSJ type drilling up jar and ZXJ
type drilling down jar, both they can be used mutually or operated
separately. The up jarring section makes use of hydraulic
mechanism, the jarring force can be adjusted according to up
elevating load but can not exceed the max. load for tool load
rated. The down jarring section makes use of mechanical friction
mechanism, the jarring force is well preadjusted by adjusting
device before put into downhole. No re-adjustment can be allowed
after jar is put into downhole.It is a first selected tool for
directional will, complicated will and deep well.