HYDRAULIC DRILLING JAR

A hydraulic drilling jar for use in association with downhole drilling and adaptable for connection between components of a drill string or the like. The hydraulic drilling jar generally comprises an outer generally hollow hydraulic housing, an inner mandrel assembly, an anvil portion, a hammer portion, and a hydraulic valve. The hydraulic housing has an enclosed first end and an open second end with the first end releasably securable to a first component of the drill string. The mandrel has a first end releasably securable to a second component of the drill string and a second end slidabl y receivable within the open second end of the hydraulic housing to forming an internal fluid chamber between the mandrel and the housing. The mandrel is also slidable within the outer housing from a contracted position to an extended position. The hydraulic housing and the mandrel operatively connect the first and second components of the drill string. One of the anvil and the hammer portions is situated on the hydraulic housin g and the other is situated on the mandrel assembly. Thea hydraulic valve is received around the second end of the mandrel and within fluid chamber. Upon extension of the drilling jar through the application of a tensile load between the housing and the mandre l, the valve seats against the housing and the mandrel tp bifurcate the fluid chamber int o first and second portions while pressurizing the first portion of the fluid chamber to place the hydraulic drilling jar in a cocked configuration. Further extension of the hydraulic drilling jar causes the valve to become unseated allowing for rapid de- pressurization of the first portion of the fluid chamber and a resulting rapid further extensi on of the hydraulic drilling jar with high impact loading of the anvil and the hammer portions.