BOREHOLE HYDRAULIC JACK Russian patent published in 2006 - IPC E21B31/113 

FIELD: oil and gas industry, particularly for freeing stuck downhole equipment.

SUBSTANCE: device comprises at least two hydraulic power cylinders, hydraulic anchor, overflow circulation valve having body connected to anchor body by means of shear pins and hollow stem connected to fishing string. Hydraulic separators having floating gaskets are installed between hydraulic power cylinders, as well as between anchor and hydraulic power cylinder. One hydraulic power cylinder comprises spring-loaded piston and consists of two cylinders provided with threads. Pistons of all hydraulic power cylinders have annular sealing means and annular groove for lubricant receiving. Orifices, which communicate hollow stem interior with hydraulic power cylinder and anchor interiors, are created in front of each hydraulic power cylinder and hydraulic anchor inside hollow stem. Orifices located in front of hydraulic power cylinders have diameters less than that of orifices formed in front of hydraulic anchors. Lower stem part is provided with seat for free-falling sealing ball receiving and connecting tread for fishing tool connection. Lower stem part is connected to valve body.

EFFECT: simplified structure along with technical capability retention.

1 dwg