DEVICE FOR STEPWISE CEMENTATION OF CASING STRING Russian patent published in 2006 - IPC E21B33/14 

FIELD: technology for reinforcing oil or gas wells, in particular related to stepwise cementation thereof.

SUBSTANCE: device includes hollow body with washing and cementing apertures, upper and lower circular recesses on internal side of body. Also provided is differential bushing with axial movement unit. Bushing is held inside the body, forms a working hollow together with it and overlaps its washing apertures. Working bushing with cementing apertures is provided. It is held inside the body by shear elements and overlaps cementing apertures of body. Working bushing has limiter of its axial movement in intermediate position and radial apertures with stops positioned inside for intermediate and uppermost cementing plugs. Stops for intermediate cementing plug are made with their possible "sinking" in lower circular recess of body at intermediate position of working bushing, when its cementing apertures are combined with cementing apertures of body. Stops for upper cementing plug are made with their possible "sinking" in upper circular recess of body at extreme lower position of working bushing, when it overlaps cementing apertures of body.

EFFECT: increased reliability of device, extended area of its possible application.

5 cl, 4 dwg