Patent ID: 8011427

Claim:
A double-acting jar comprising: an outer housing; an inner mandrel at least partially disposed telescopically within the outer housing to define a fluid chamber between the inner mandrel and the outer housing, the fluid chamber containing fluid and being sealed; a valve disposed within the fluid chamber on one of the inner mandrel and the outer housing; the valve having a downhole portion that is movable between a downhole seated position in which the valve seats against the one of the inner mandrel and the outer housing and an unseated position, the downhole portion having a downhole restriction surface; the valve having an uphole portion that is movable between an uphole seated position in which the valve seats against the one of the inner mandrel and the outer housing and an unseated position, the uphole portion having an uphole restriction surface; the other of the outer housing and the inner mandrel having a cooperating restriction surface that cooperates with the downhole restriction surface and the uphole restriction surface to set the double-acting jar for a jar, the cooperating restriction surface being dimensioned so that, from relative movement of the inner mandrel and the outer housing, the cooperating restriction surface is movable between above and below the valve with a neutral position in which a portion of the cooperating restriction surface is between the downhole restriction surface and the uphole restriction surface; the downhole restriction surface incorporating a first bypass that is configured to allow bypass of fluid in the chamber when the downhole restriction surface and the cooperating restriction surface move past each other during re-setting of the jar to the neutral position; the uphole restriction surface incorporating a second bypass that is configured to allow bypass of fluid in the chamber when the uphole restriction surface and the cooperating restriction surface move past each other during re-setting of the jar to the neutral position; first jarring surfaces on the inner mandrel and outer housing respectively for jarring contact with each other during a jar in a downhole direction; and second jarring surfaces on the inner mandrel and outer housing respectively for jarring contact with each other during a jar in an uphole direction.