Patent ID: 8365818

Claim:
A jarring tool attachable to a well conduit for delivering an impact to a stationary object downhole, the tool comprising: an outer tubular assembly; an inner tubular assembly telescopically received in the outer tubular assembly for relative movement from a contracted position to an extended position; wherein the inner and outer tubular assemblies define a flow path through the tool, and wherein when fluid pressure inside the tool exceeds fluid pressure in the wellbore, the fluid pressure tends to extend the tool; wherein one of the inner and outer tubular assemblies is attachable to the well conduit and the other of the inner and outer tubular assemblies is attached to the stationary object; a jar assembly in the tool wherein the jar assembly comprises an anvil surface and a hammer surface; and a hydraulic reset assembly in the tool comprising at least one hydraulic chamber and piston, the hydraulic chamber is in fluid communication with the flow path so that, when fluid pressure inside the tool exceeds fluid pressure in the wellbore, fluid pressure in the chamber tends to contract the tool.