DEVICE FOR STAGE CEMENTING OF WELL Russian patent published in 2001 - IPC

FIELD: casing of oil and gas wells; particularly, devices for cementing of casing strings of these wells. SUBSTANCE: device includes body with cementing holes, lower and upper control bushings. There are also extensible resets for intermediate cementing plug. Extensible rests are engageable with lower busing and installed under cementing holes. Device body is double-walled with circular space between external and internal walls and wit washing holes under cementing holes. there is special unit for communication of body space wit circular space after forcing of cement mortar of the first stage of cementing. Lower and upper bushings are made with radial holes and located in circular space for successive motion of lower bushing by upper bushing to the first intermediate fixed position, second intermediate fixed position and extreme lower position. In this case, provision is made for successive opening-closing of washing holes by lower bushing and opening-closing of cementing holes by upper busing. Extensible rests are installed from cementing holes at distance ensuring alignment of upper end face of intermediate plug with lower edge of cementing holes. Upper cementing plug has possibility of seating onto intermediate cementing plug with closing of cementing holes. EFFECT: higher operate reliability of device, reliability of freeing of device internal space upon completion of cementing without drilling operations. 5 cl