Patent ID: 8230912

Claim:
A jarring tool attachable to a well conduit for delivering an impact downhole, the tool comprising: an outer tubular assembly; an inner tubular assembly telescopically received in the outer tubular assembly for relative movement from a neutral position to an up jar position and from the neutral position to a down jar position; 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 a stationary object downhole; wherein the inner and outer tubular assemblies are configured to form a sealed annular hydraulic chamber therebetween; up and down anvil and hammer surfaces formed on the inner and outer tubular assemblies; a restricted section formed in the hydraulic chamber dividing the hydraulic chamber into upper and a lower chambers; a first piston supported in the hydraulic chamber for relative movement from a neutral position in the upper chamber above the restricted section to a jarring position below the restricted section, wherein the first piston comprises a flow channel continuous with the hydraulic chamber that permits fluid flow through the piston; a first valve configured to close the flow channel in the first piston as the first piston moves relatively in a down direction through the restricted section and to open the flow channel in the first piston as the first piston moves relatively in an up direction through the restricted section, whereby a jarring impact is created as the first piston moves past the restricted section in the down direction; a second piston supported in the hydraulic chamber for relative movement from a neutral position in the lower chamber below the restricted section to a jarring position above the restricted section, wherein the second piston comprises a flow channel continuous with the hydraulic chamber that permits fluid flow through the piston; and a second valve configured to close the flow channel in the second piston as the second piston moves relatively in an up direction through the restricted section and to open the flow channel in the second piston as the second piston moves relatively in a down direction through the restricted section, whereby a jarring impact is created as the second piston moves past the restricted section in the up direction.