Pipe centralizer and method of attachment
A crimpable centralizer has been invented for installation on pipe, such as would be useful in well bore drilling and casing operations. The present invention provides a centralizer having a cylindrical body which when coaxially placed over a pipe and substantially radially inwardly displaced at a plurality of points (i.e. crimped) about the circumference of a section of the cylindrical body, attaches to the pipe to create a connection having structurally significant axial and torque load transfer capacity. When crimped according to the methods of the present invention, the load transfer capacity of the connection between the centralizer and the pipe can be arranged to substantially prevent significant relative movement of the centralizer on the pipe under loads that may be encountered when using one or more of the pipes as components of a tubular string used for drilling or completing well bores.
1. A method for attaching a centralizer to a metal pipe by crimping, the metal pipe having an outer surface, such method comprising the steps of: providing a metal pipe; providing a centralizer having a body with an inner bore therethrough sufficiently large to allow insertion therethrough of the metal pipe, a plurality of outward facing bearing surfaces on the body and at least one tubular section on the body having an internal diameter capable of fining about the outer surface of the metal pipe; inserting the metal pipe through the inner bare of the centralizer, applying an inward, substantially radially-directed force to a plurality of points about an outer circumference of the tubular section causing it to plastically deform inwardly and come into contact with the outer surface of the pipe at points corresponding to the plurality of points; and applying such additional inward, substantially radially directed force as required to force both the centralizer and the outer surface of the metal pipe to displace inwardly an amount at least great enough so that when released, an interference fit is created between the centralizer and the metal pipe.
2. The method of claim 1 wherein at least one of the outer surface of the pipe arid an inner surface of the tubular section is roughened to facilitate frictional engagement therebetween.
3. A wellbore casing assembly comprising: at least a section of wellbore casing; and a wellbore casing centralizer crimped onto the at least a section of well bore casing, the wellbore casing centralizer including a body having a first end and a second end opposite the first end, an outer facing surface and an inner bore extending therethrough from the first end to the second end sufficiently large to allow insertion therethrough of the external diameter the section of wellbore casing, at least one crimpable tubular section on the body through which the wellbore casing centralizer is crimped about the external diameter of the section of wellbore casing and a centralizing section on the body including a plurality of bearing surfaces extending outwardly from the outer facing surface.
4. The wellbore casing assembly of claim 3 wherein the crimpable tubular section has an external diameter to thickness ratio of less than 100.
5. The wellbore casing assembly of claim 3 wherein the crimpable tubular section has an external diameter to thickness ratio of less than 50.
6. The wellbore casing assembly of claim 3 wherein the crimpable tubular section is circumferentially continuous such that hoop stress can be generated therein.