HYDRAULICALLY DRIVEN FISHING JARS

摘要

A fishing jar (11) is placed in a work string for delivering blows to a stuck object in a well. This fishing jar (11) utilizes energy stored in the work string for delivering the blow, rather than having a main spring of its own. The fishing jar (11) uses hydraulic pressure to move a piston member (35). The piston member (35) engages a firing member (75) when it reaches one end of its stroke. The directional valve (45) then directs fluid to the other side of the piston (35) to cause the piston (35) to move in the opposite direction. When it starts to move in the opposite direction, the firing member (75) will provide a restrictive load against that movement. Once the pressure builds to a high enough level, it will move the housing (13) relative to the piston (35), which is restricted from movement by the firing member (75). When the housing (13) moves, it elastically deforms the work string, storing energy in the work string. The firing member (75) will release the housing (13) once the housing (13) reaches the end of its stoke. The housing (13) has a hammer surface (97) that strikes an anvil (95) once released.