MULTIBRANCH WELL CONSTRUCTION METHOD Russian patent published in 2006 - IPC E21B7/08 

FIELD: special methods or apparatus for drilling, particularly for deflecting the direction of boreholes.

SUBSTANCE: method involves cutting window in casing pipe of primary well bore, wherein the casing pipe is provided with splines and retrievable seating unit is installed on the splines, the retrievable seating unit includes inner splines arranged in upper seating unit part, outer splines located in lower seating unit part and seating casing pipe provided with clutch having auxiliary wedge member at upper clutch end; filling interval of retrievable seating unit installation with non-hardening viscous-plastic liquid having shearing strength determined from mathematical relation; drilling additional bore to design depth with the use of deflection wedge provided with splines in lower part thereof and with seating plate having angle of inclination equal to that of auxiliary wedge member; removing deflection wedge from well after additional bore drilling; delivering liner with casing pipes to head of newly-drilled additional bore; sealing additional bore head by lowering head packing unit in additional bore head, wherein head packing unit comprises shutoff packer provided with medium separation means and has wedge with channels for plugging composition and additional connection pipe with collars in upper part thereof; injecting plugging composition in liner and flushing the well; drilling upper part of additional connection pipe and removing seating unit after additional bore completion.

EFFECT: increased reliability of deflection wedge fastening for window cutting in casing pipe, prevention of mud accumulation in main well bore during additional bore drilling.

11 dwg, 1 tbl