WELL HEAD FACILITY FOR RELEASE OF FLOW STRING OUT OF BOREHOLE Russian patent published in 2010 - IPC E21B31/113 

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil and gas producing industry, particularly to wellhead facilities for release of flow string stuck in borehole at failure. The wellhead facility for release of flow string out of borehole consists of a damper and of a vertical pulse generator. The damper is made in form of a vertical sealed cylinder with a piston, an under piston cavity of which is filled with gas, while the generator is made as tubular case consisting of successively connected power cylinders. The power cylinders are furnished with pistons serially joined with hollow rods so, that under piston cavities of the power cylinders communicate between them and via a distributor they communicate with a piston valveless pump. The distributor consists of a cylinder case with two chambers divided with a partition equipped with direct-acting and back spring loaded valves: also force of contraction of the back valve with the spring is higher, than contraction force of spring of the direct-acting valve.

EFFECT: simple design and raised efficiency of release of stuck flow string out of borehole.

1 dwg