COMPLETION OF DIRECT-CEMENTING CASING STRING WITH RETURN VALVE Russian patent published in 2015 - IPC E21B33/14 

FIELD: oil and gas industry.

SUBSTANCE: assembly of direct-cementing casing string with return valve is suggested, and this assembly comprises a common case for plug catching baffle with feed-through channel made to seal and fix a cementing plug, and return valve including bushing and saddle for the gate formed in the upper part of the bushing connected to the plug catching baffle. At that the return valve is made with the gate made as a ball and extendible saddle with elastic sealing. Moreover the upper part of the return valve bushing is fixed inside the feed-through channel of the plug catching baffle. Besides, the baffle is made with groves while cementing plug is equipped with a latch with scalloped surface to be inserted into the above grooves at setting the cementing plug into the plug catching baffle.

EFFECT: improved reliability of the casing string closure upon completed circulation of grouting mortar both with cementing plug and return valve and fixation of gates from rotation for the purpose of in-line drilling of the assembly upon cementing.

5 cl, 10 dwg