DEVICE FOR CEMENTING OF CASING STRINGS Russian patent published in 2000 - IPC

FIELD: drilling of oil and gas wells. SUBSTANCE: device is intended for lowering and cementing of liners and sections of continuous casing strings under complicated geological conditions where rotation of drill and casing pipes is needed for reaming of wellbore in the course of their lowering. The device has centralizer with longitudinal helical recesses. Centralizer is located on stem under sub. Piston is located in circular hollow under oil. Stem accommodates bushing which is connected with sub by shear pins. Attached to stem lower part by means of shear pins is separating bushing. Diameter of trip ball exceeds the internal diameter of bushing. Sleeve-funnel has internal longitudinal recesses in its lower part. The recesses are communicated with hollow under piston and with annular space. Located in hollow upper part is pipe union plug whose closed end is located under bushing internal hollow. Open end of pipe union plug is communicated with hollow through blind longitudinal hole. Hole depth exceeds thickness of stem wall. Sleeve-funnel and stem are interconnected by splined joint. Sub has through radial holes which are located under pins and overlapped by bushing. Device is made for motion of bushing when drilling mud is injected in volume determined by expression. EFFECT: higher reliability of device operation. 2 cl, 4 dwg