DEVICE FOR CASING STRING CEMENTING Russian patent published in 2002 - IPC

FIELD: construction of oil and gas wells, particularly, devices for separation of pumped fluids. SUBSTANCE: device has a cementing plug with rigid core to which flexible collars and end piece are secured. End piece lower part is conical and its cylindrical part has bore for split spring ring. External part of ring is made at an angle of 25-30 deg to upper surface of end piece sealing cone. End piece upper part has seating cone which comes in contact with upper conical internal bore of stop ring. It is also provided with bore in cylindrical part. Packing ring is installed in bore. Ring enters mating lower cylindrical internal bore of stop ring which has upper conical, middle and lower cylindrical internal bores. Diameter of middle cylindrical internal bore is less than diameter of lower cylindrical internal bore. All conical members of each flexible collar are separable. They have projections and mating recesses in lower and upper cylindrical parts, respectively. Lower and upper flexible collars have similar connections with upper surface of seating cone of end piece and flange, respectively. Length of external vertical conical part of flexible collar is determined by empirical formula. Total length of assembled flexible collars coming in contact with casing pipe is determined by empirical formula too. EFFECT: higher quality of casing string cementing due to exclusion of wear of flexible collars, accurate calculation of length of plug itself and fixation of plug end piece in stop ring.