TECHNICAL FIELD

The present invention relates to a strain relief device for protecting Tubular Electric Cable (TEC) end portions and, more particularly, to a strain relief device that protects end fittings from leakage and loss of circuit continuity. The TEC end fittings may be of fibre- optic or electric type service.

BACKGROUND OF THE INVENTION

In down-hole control and monitoring system applications, Tubular Electric Cable (TEC) are used as control lines and are generally routed along the wellbore tubing to access individual down-hole apparatus. Most TEC control lines used in oilwell applications are for power and communication means and may be of fibre-optic or electric type, or any combinations thereof. In the practice of routing and running TEC control lines along a wellbore conduit, ultimate torsional and tensional loads are imposed on the cable. Moreover, stretching loads are induced during the handling and attachment of the tubular control line to the wellbore conduit as well as during the run- in or installation phase in the well. The latter is mainly due to swabbing effects as the line is squeezed between an inner and an outer wellbore conduit. For those skilled in the art, the aforementioned inner and outer wellbore conduits are often referred to as the wellbore "tubing" or "completion" and the wellbore "liner" or "casing", respectively.

Loads imposed to the TEC are both torsional and tensional and contribute to ultimate loads onto the splices and end connections which in turn cause cable integrity failures of both short and long-term type. For electric and fibre-optic TEC applications, the root cause of failure ultimately initiates a leak of some kind, exposing the integral wires or optic signal lines to unknown fluids from the surroundings. This in turn leads to degradation of insulation resistance of the cable, wire oxidation and loss of optic or electric signal/power continuity. In real world, the breakdown is usually due to leaks and is typically evident inside the TEC end- fittings and splice. The main cause is lack of sufficient strain relief between the tubular jacket and its termination fittings.

US 7,220,067 (Rubinstein et al.) provides an example of existing tubular control line applications. This application provides no strain relief to the end-fittings, terminations, or for the wiring inside, and tubular control lines such as this are subject to a variety of well known problems, limitations, and disadvantages, as described above.

It has therefore been considered desirable to develop a strain relief assembly for TEC control lines which would readily accommodate high tensional and torsional loads. The nature of the handling, operation and installation of apparatus in the wells normally imposes excessive loads onto the control lines. The present invention, in combination with TEC control line end fittings, terminations or splice, reduces failure of the cables used and provides a new protective device which is simple in design, effective in use and adapted for use in oilwell applications.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a strain relief assembly for protecting one or more wires, cables or tubular control lines, comprising a hollow tubular insulating jacket, where the hollow tubular insulating jacket comprises an internal structural support for a wire, cable or tubular control line.

Failures related to leaks and electrical and/or optical continuity in applications using Tubular Electric Cable (TEC) control lines are eliminated through the use of a resilient strain relief assembly attached to the TEC end fittings and splice. The assembly may consist of a channel tubing duct or bore with a slotted section thereof. The slotted trough guides a bent or formed section of the TEC which provides strain relief for the end connection in two orthogonal planes. The strain relief is affixed to the tubing end connection (anchor fittings) and is uniquely constructed in a manner that avoids the transfer of torsional, tension and transverse loads imposed from the TEC tubular jacket to the end connection and its internal termination. The strain relief assembly serves as a resilient, protective securing anchor for the tubular control line.

For a fibre-optic or electric control application utilizing TEC type control lines, stresses imposed either by tensional or torsional loads to the cable and end connection are typically completely absorbed and neutralized within the strain relief assembly. This is mainly due to the bent configuration of the TEC and the structural support it receives inside the slotted section of the strain relief assembly. Moreover, the strain relief assembly of the present invention is designed to resiliently protect fiber-optic and electric control line end connections and their internal wiring from being pulled off or damaged. Damage to the end connections would cause a circuit discontinuity that may lead to loss of power, communications, or combination thereof. The protection is provided as a result of the bent, twisted, or axially curved configuration as described below which locks and secures the inner wires to the cable jacket at the end section of the TEC. In this manner, tensional, transverse and torsional forces inducing stress and strain to the internal wiring as well as the jacket will be removed in the bends and will not reach the end section where the cable or fibre is terminated. This eliminates the phenomenon of the TEC being pulled from the end wire terminations, which is a huge improvement in respect to the commodity of TEC end fitting and splices. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 : is a perspective view of the present invention

Figure 2: cross-sectional view of the present invention

Figure 3: is a perspective view of an alternative embodiment of the present invention

Figure 4: is a cross-sectional view of an alternative embodiment of the present invention

Figure 5: is an illustration showing the service of the present invention.

DETAILED DESCRIPTION

Referring to Figures 1 , 2, 3 and 4, the strain relief assembly 2 comprises a connection 10, an end fitting aperture 3, a tubing duct 1, and a receiving aperture 5. Referring specifically to Figures 2 and 4, the channel exit section of the end fitting aperture 3 defines the "exit" 1 1, and the entrance of the receiving aperture 5 defines the "entrance" end of the strain relief assembly 2. In turn, at the exit end 11 the end fitting aperture 3 is advantageously sized to receive and protect the end termination of the Tubular Electric Cable (TEC) 4. The tubing duct 1 extends from the exit of the channel receiving aperture 5 to the entrance of the channel end fitting aperture 3 and lies in one or two orthogonal planes. The connection 10 attaches the strain relief assembly 2 to the anchor fittings 8 in a way that prevents rotation of the strain relief assembly 2 and the end fitting 7, relative to anchor fittings 8. The end fitting 7 provides both a mechanical attachment and a seal with the jacket of the TEC 4, thus avoiding leaks to the interior of the anchor fittings 8.

To prevent the rotational and axial load from the end of the TEC 4 control line being transferred to the end fittings 7, the TEC 4 is formed into a bent configuration 41 inside the tubing duct 1. The combination of the bent configuration 41 inside the tubing duct 1 defines the stress and strain relief section of the strain relief assembly 2. The strain relief assembly 2 can be made inexpensively in a suitable material to comply with the anchor fittings 8 and TEC 4, and provides stress and strain relief in order to protect the end terminations of the TEC 4. The stress and strain relief includes relief from axial and torsional loads which are some of the most frequent causes of leaks and circuit discontinuity in most down-hole tubular control line applications.

The bent configuration 41 resiliently protects the internal wiring (or fibre optic cable) 6 and the cable insulating jacket 9 from moving inside the TEC 4. This is achieved through the creation of an internal friction-lock of the wiring 6 and insulating jacket 9, eliminating the stress and strain applied to the cable, which may otherwise pull off, unscrew or damage the connections attached at the end of the cables.

Referring to Figures 3 and 4 of this invention particularly, these figures show an alternative embodiment of the present invention to that provided in Figures 1 and 2. Instead of a straight-through tubing duct 1, as of Figures 1 and 2, this derivative strain relief assembly 2 has a three-dimensional axially curved tubing duct 1. The duct 2 screws over the mid section of the strain relief assembly 2 to prevent tension and rotation of the end fitting 7 after mounting. Due to the nature of the twisted duct I, this embodiment is designed to ease the installation and stress/strain relief of the TEC 4 control line and end fittings 7, as no special tool is required to form or bend the TEC 4 inside the tubing duct 1. The twisted section easily guides the TEC 4 through one. or two 90 degree or more curves lying in two orthogonal planes. The forming and placement of the TEC 4 into said tubing duct 2 is easily done by hand and without the use of special tools.

Further, the use of one or two coincident curves along the axis of the unit significantly reduces the TEC 4 routing space and firmly secures the cable within the strain relief assembly at the same time as it provides the optimum stress/strain protection of the end fittings 7. As with the embodiment described by Figures 1 and 2, the twisted or axial ly curved configuration 41 of this embodiment resiliently protects the internal wiring (or fibre optic cable) 6 and the cable insulating jacket 9 from moving inside the TEC 4. This is achieved through the creation of an internal friction-lock of the wiring 6 and insulating jacket 9, eliminating the stress and strain applied to the cable, which may otherwise pull off unscrew or damage the connections attached at the end of the cables.

The mounting of the receiving aperture 5 resiliently secures the line and requires no additional ties, straps or clamps to hold the TEC 4 within the strain relief assembly 2. Therefore, the second embodiment provides overall protection towards tensional and torsional loads both to the TEC 4 control line end as well as to the strain relief assembly 2.

Figure 5 illustrates an oil-well application and a typical service for the present invention. In the illustration the TEC 4 control line and strain relief assembly 2 is attached to a down-hole instrument 13. Further, the instrument 13 is part of an instrument carrier 18, both of which are mounted to the inner wellbore conduit 12. In turn, the inner wellbore conduit 12 is fed into a wellbore 15 having an outer wellbore conduit 14. The TEC 4 is maintained and controlled from a winch 16. To freely enter the wellbore 15 the TEC 4 is run through an overhanging sheave wheel 17. However, it is important that the TEC 4 control line is securely and resiliently fixed to the wellbore conduit 12 to avoid constrictions and entanglements as it is fed into the wellbore 15. To avoid possible constrictions and entanglements, the TEC 4 is highly stretched by force or braking of the winch 16 and consecutively clamped using control line clamps 19. Typically, the control line clips are attached to each of the tubing collar 20 of the wellbore conduit 12 as the tubing assembly is lowered into the wellbore 15. Thus, it is seen that the TEC 4 and its end portions should be capable of resisting the ultimate stress and strain from the mounting and installation process. For those skilled in the art, it is known that this handling can cause failure and fatalities to the TEC 4 and it is expected that they will encourage the use of this new protective device.

Although the invention has been shown and described with respect to two embodiments, modifications and alterations will occur to others upon reading and understanding this specification. It is intended to include all such modifications and alterations insofar as they come within scope of the appended claims or the equivalent thereof.