COUPLING FOR STEPWISE CEMENTATION OF CASING STRINGS Russian patent published in 1995 - IPC

FIELD: oil and gas industry. SUBSTANCE: coupling is a device having a composite body with holes for circulation and an inner shoulder. Inside the body there is a movable bushing with a seat and circulation holes. The bushing is locked in its extreme position by a retaining unit. The bushing and the body combine to form an annular space. There is a differential bushing in this annular space. The annular bushing covers the circulation holes of the body and the movable bushing. The device is provided with an intermediate bushing. The intermediate bushing has sealings on its internal surface, connecting thread, and radial holes with annular grooves. An intermediate space is formed in the internal surface of the movable bushing. The movable bushing has radial holes under its circulation holes. These radial holes make the intermediate space open to the annular space under the lower end-face of the differential bushing. The shear retaining unit is located in the axial channel of the intermediate bushing. This unit covers radial holes of the intermediate bushing. EFFECT: higher reliability. 4 dwg