SLEEVE FOR STEPPED CEMENTATION OF CASING STRINGS Russian patent published in 1999 - IPC

FIELD: oil and gas production industry. SUBSTANCE: sleeve is used in construction of wells and in cementation of casing strings. Sleeve has body with circulation holes, movable differential bush, cementation plug, and holding seat. Holding seat is attached to lower end of differential bush by means of left-hand thread. Holding seat is provided with protrusions which are inserted into corresponding slots made in lower part of body. Body is covered by shear bottom with creation of air chamber together with insertion in holding seat with interference after shearing of bottom and connection of air chamber with space below cementation plug. Aforesaid embodiment of cementation sleeve is characterized by simplified design, improved reliability in closing, and easier drilling through cementation plug. EFFECT: higher efficiency. 2 dwg