DEVICE FOR EXTRACTION OF PIPES FALLEN TO WELL Russian patent published in 2013 - IPC E21B31/00 

FIELD: oil and gas industry.

SUBSTANCE: device includes a housing of round elongated shape having two blind central holes from below and from above. In lower hole there are four grooves of rectangular shape, which are located at the same height and at equal distance from each other. On inner walls of grooves there located are isolating plates, against which one end of plate springs is borne. The other end of the above spring is borne against inner surface of electrodes installed in grooves on hinges from below. Electrodes are connected to a negative terminal of a DC source. A positive terminal of the source is connected to a casing string, inside which an extracted pipe is located, and namely on its head. Upper hole forms a cavity for electrolyte, in which a submersible pump providing the electrolyte supply to the anodic dissolution zone is arranged. Electrolyte cavity is covered from above with a cover plate with an eye bolt that is connected to a transport system via a rope. Electrodes on projecting edges are provided with isolating platforms for formation of a gap between the electrode and outer surface of the extracted pipe, to which electrolyte is supplied by the pump. Anodic dissolution of extracted pipe metal takes place till formation of holes in the wall, and electrodes are sunken in them.

EFFECT: improving pipe extraction reliability.

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