DOWNHOLE JAR APPARATUS FOR USE IN OIL AND GAS WELLS

摘要

A downhole jar apparatus for use in oil and gas wells provides an improved construction that features a movable piston that imparts upward blows to the tool body during use. The apparatus includes an elongated tool body having upper and lower end portions and a longitudinal flow bore for enabling fluid to pass from the upper end of the tool body to the lower end portion thereof. A pair of pistons are slideably mounted within the tool body including an upper piston having a seat and a lower piston having a seat. A ball valving member is used to seal the upper piston, that ball valving member being pumped down through a work string such as a coiled tubing unit in order to reach the seat of the upper piston. A second valving member in the form of an elongated dart is disposed in between the two pistons. A trip mechanism separates the second valving member from the lower piston when a predetermined hydrostatic pressure value is overcome. Once the second valving member and lower piston are separated, the second piston is fired upwardly striking an anvil portion of the tool body to create the upward jar or blow.