Patent ID: 6209638
Filing Date: 2001-04-03
Classification: E21B

Abstract:
An improved wellbore casing accessory, comprising:a) an elongated tubular member having a bore therethrough, a central recessed section and enlarged diameter end sections, at least one end of said tubular member adapted to connect to a casing string, a diameter of said central recessed section being substantially equal to a diameter of said casing string;b) a plurality of lugs disposed on an outer surface of said central recessed section of said tubular member in two longitudinally spaced-apart positions, at least one of said plurality of lugs in each of said positions; andc) a bow spring centralizer mounted in said central recessed section of said tubular member, said bow spring centralizer comprising a pair of spaced apart bands encircling said central recessed section of said tubular member, each of said bands having at least one window therein disposed over one of said lugs, and a plurality of circumferentially spaced, outwardly bowed bow spring blades connecting said pair of bands,wherein sizing and spacing of said lugs, said windows, said bands, and said bow spring blades results in said bow spring centralizer being dragged when said wellbore casing accessory is forced through a passageway having a diameter less than a diameter of said bow spring centralizer at rest, and only one band is in longitudinal contact with a lug at any one time, and wherein a diameter of said bow spring centralizer when fully collapsed and a diameter of said bands is no greater than a diameter of said enlarged diameter end sections.