Temperature compensated wire-conducting tube and method of manufacture

Abstract

A method and apparatus for manufacturing a continuous metal tube having a plurality of electrical conductors disposed therein, by using a spring member to depress the electrical conductors while a flat metal strip is formed into a tubular member and welded to enclose the electrical conductors. The spring member functions to protect the electrical conductors from heat damage. The welding occurs completely downstream of the spring member in order to avoid excessive heat buildup in the spring member.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to an elongated tubular member having electrical conductors disposed therein. The tubular member is capable of transmitting both a fluid medium and electrical power to a remote location. The term elongated is used to refer to tubular members of at least 1000 ft. or more in length with the members being fluid-tight sothat the fluid can be transmitted to the remote location.The tubular members of the present invention are particularly useful in the steam quality measuring systems disclosed in U.S. Pat. Nos. 4,581,926 and 4,736,627. These patents disclose methods and apparatus for measuring the quality of steam being injected into a subterranean formation to enhance the recovery of heavy crude deposits from the formation. Steam is the most widely used thermal recovery method where it is desirable to heat heavy crude deposits to more efficiently produce them. The patents require both the transmission of electrical power to the mea...

AI Technical Summary

Benefits of technology

The present invention solves the above problems by providing a simple means by which a tubular member may be manufactured having the required electrical conductors disposed therein. In addition, the invention disposes the electrical conductors in a position wherein the conductors will remain in position as they elongate due to thermal expansion.

The invention utilizes a continuous flat strip of metal that is formed into a continuous tubular member with the edges of the strip being juxtaposed. The edges of the strip are then welded together to provide a fluid-tight tubular member. In addition, as the flat strip is formed into a tubular member, the electrical conductors are fed into the tube simultaneously with the forming of the tubular member. The invention provides a means by which the electrical conductors may be protected from the damaging heat of the welding operation. It is preferable to use alloy steel for forming the tubular member and a shielded arc welding technique such as tungsten inert gas welding to join the edges together.

Compensation for the difference in the thermal expansion rates of the tubular member and the electrical conductors is provided by properly sizing the tubular member and forming the electrical conductors in the shape of a helix. The inside diameter of the tube is selected sufficiently large to accommodate the helical shape of the electrical conductors. The helical shape of the conductors ensures that they will contact the inner wall of the tubular member. The friction from this contact is sufficient to hold the conductors in position in the tubular member. As the conductors elongate in response to a temperature increase, they will be forced into increased contact with the inner wall of the tubular member. This will increase the friction force that holds the conductors in position. Thus, the conductors will remain in position and not fall to the lower end of the tubular member as it is inserted into the well.

Problems solved by technology

This would be a complicated arrangement, particularly since it is necessary to feed the members through a wellhead lubricating system since the wells must actually be in production to obtain measurements.

While this is possible, it is normally not possible to feed the electrical conductors through the length of the tubular member required in well logging operations.

This is time consuming and would increase the probability of an ineffective electrical connection.

In addition to the problem of providing the tubular member with the electrical conductors disposed therein, there is also the problem in thermal injection wells of providing for temperature compensation between the different materials used for the electrical conductors and the tubular member.

In addition, many wells have a corrosive atmosphere that requires the use of corrosion resistant materials.

If no means are provided for compensating for the expansion of the copper conductors, the greater length of the conductors will cause them to tend to fall to the bottom of the tubular member as it is lowered into the borehole In extreme cases the conductors could eventually plug the bottom of the tubular member.

In addition, it is possible that when the tubular member is withdrawn from the borehole, spooled on the storage drum and allowed to cool to atmospheric conditions, the copper, in cooling, will break some of the conductors due to contraction and the inability of the bunched-up conductors to freely move within the tubular member.

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