DOUBLE-ACTING JAR

摘要

A double-acting jar comprises an inner mandrel and an outer housing. The inn er mandrel is disposed telescopically within the outer housing to define a fluid chamber i n between. There is an uphole restriction and a downhole restriction spaced from one another within the fluid chamber. A uphole valve is disposed within the fluid chamber, the uphole val ve having a first seating surface engageable with an uphole facing sealing shoulder in the flu id chamber. The uphole valve has a first exterior surface that fits with close tolerance within the uphole restriction over at least a portion of the first exterior surface. There is a downhole valve disposed within the fluid chamber, the downhole valve having a second seatin g surface engageable with a downhole facing sealing shoulder in the fluid chamber. The downhole valve has a second exterior surface that fits with close tolerance within th e downhole restriction over at least a portion of the first exterior surface. There are first jarring surfaces on the inner mandrel and outer housing respectively for jarring contact with ea ch other during an upjar, and second jarring surfaces on the inner mandrel and outer housing respectively for jarring contact with each other during downjar. The uphole restriction and downhole restriction are separated such that when the downhole restriction slides upward over the initial portion of the downhole valve to seat the downhole valve, at least a portion of the uphole restriction extends upwardly beyond the downhole end of the uphole valve sufficient to allow a downjar to be carried out. The uphole restriction and downhole restriction are also separated such that when the uphole restriction slides downward over the initial porti on of the uphole valve to seat the uphole valve, at least a portion of the downhole restricti on extends downwardly beyond the uphole end of the downhole valve sufficient to allow a n upjar to be carried out.