Downhole signal-conducting and power-conducting flexible cable

Abstract

Disclosed herein is a downhole signal-conducting and power-conducting flexible cable that can stretch and contract as required while remaining conductively conducted to a source and a receiver. Also disclosed is a method of conducting a signal and power downhole through said flexible cable. The flexible cable can be used with or included with downhole tools.

Claims

1. A method for conveying a signal and power through a flexible cable, said cable comprising: a. an electrical and signal conducting cable i) formed like a serpent; ii) cast into a rubber strip; iii) installed between a mandrel and a washpipe; and iv) shaped into a half shell to fit between said mandrel and washpipe; wherein i) the upper part of the rubber strip is fixed to the mandrel or washpipe; and ii) the lower part of the rubber strip is fixed to a lower mandrel or other part of the string located below the moving parts of the drive spline and held in position by a flexible rubber material and held in suspension so it can either expand or contract.

2. The method of claim 1, said cable comprises two cables located on one half circle each.

3. The method of claim 2, wherein the flexible rubber is replaced by a lattice.

4. The method of claim 1, wherein the flexible rubber is replaced by a lattice.

5. The method of claim 1, wherein the electrical and signal cable is replaced by a two lead or more cables providing multiple independent signals and/or power transfer.

6. The method of claim 1, wherein said cable comprises two or more conductors mounted in the same rubber compound.

7. A flexible cable for conveying one or more signals and power therethrough, said flexible cable comprising: a. an electrical and signal conducting cable i) formed like a serpent; ii) cast into a rubber strip; iii) installed between a mandrel and a washpipe; and iv) shaped into a half shell to fit between said mandrel and washpipe; wherein i) the upper part of the rubber strip is fixed to the mandrel or washpipe; and ii) the lower part of the rubber strip is fixed to a lower mandrel or other part of the string located below the moving parts of the drive spline and held in position by a flexible rubber material and held in suspension so it can either expand or contract.

8. The flexible cable of claim 1, said cable comprises two cables located on one half circle each.

9. The flexible cable of claim 2, wherein the flexible rubber is replaced by a lattice.

10. The flexible cable of claim 1, wherein the flexible rubber is replaced by a lattice.

11. The flexible cable of claim 1, wherein the electrical and signal cable is replaced by a two lead or more cables providing multiple independent signals and/or power transfer.

12. The flexible cable of claim 1, wherein said cable comprises two or more conductors mounted in the same rubber compound.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings accompanying the present invention serve to illustrate the nature of the invention. These drawings are included for purposes of illustration only and should not be understood as strictly limiting the invention claimed herein.

[0015] The drawings include the following parts: (1) Mandrel; (2) Washpipe; (3) Rubber strip; (4) Serpentined cable; (5) Fixing hole on rubber strip lower end; (6) Elongated cable upper end; (7) Fixing hole on rubber strip on upper end; (8) Elongated cable, lower end; (9) Threaded lower end of washpipe; (10) Fixing hole on 1; (11) Fixing hole on lower end of washpipe; (12) Threaded lower end of mandrel; and (13) Threaded upper end of mandrel.

[0016] FIG. 1 depicts some of the components of the flexible cable of the invention.

[0017] FIG. 2 depicts embodiments of the rubber strip and serpentine cable employed with the flexible cable.

[0018] FIG. 3 depicts an embodiment of the flexible assembled and in compressed form.

[0019] FIG. 4 depicts the flexible cable of FIG. 3 in relaxed or uncompressed form.

[0020] FIG. 5 depicts an alternate embodiment of the flexible cable of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Electric line, conductor, cable, wire and coil are terms used in this application and in other patents to describe a conduit that can transmit a signal or power or both through a tool or from one tool to another or through a drillstring. For this application, the word conductor has been used to encompass said terms. Furthermore, all tools described as prior art and the present invention has at least three components in common, a mandrel, a washpipe mechanically connected with the mandrel having the washpipe installed inside it and a conductor cable. The annular space between the mandrel and the washpipe is where a conductor would normally be installed in order to protect it from flow. The mandrel and the washpipe are connected to the lower housing with a spline system that allows these two elements to change its total length when activated. This is valid for jars, energizers, shock subs, bumper subs and other tools fitted with a spline that allows axial movement.

[0022] The present invention discloses a method to mount a flexible conductor or cable between a mandrel and a washpipe. The mandrel is connected to a lower housing by a spline in such a way that the mandrel and lower housing can move or stroke in a telescopic manner without rotating independently of each other. This type of ability is used in drilling jars, shock tools, bumper subs and energizers, all downhole drilling tools. All the mentioned tools require a limited stroke to function. Further, all the tools described also require flow of mud or other fluids to go through them. A drilling jar, when in use, can stroke both up and down and the mandrel and lower housing can be accelerated either apart or towards each other to create an impact. When using a wired drillpipe system, it is necessary to convey a flexible conductor through the tool with variable length. Present technologies include U.S. Pat. No. 6,991,035B2 that teaches a flexible coil mounted between a mandrel and a wash pipe. The coil can change length when required. However, the drawback is that when a coil changes length, it also must change diameter to compensate for the change in length. This fact requires extra annular space between the mandrel and the washpipe, where it is mounted. This extra space must be compensated for by either increasing the diameter of the mandrel or decreasing the diameter of the washpipe. Any change in diameter will reduce the available space for fluid to pass through the tool and will increase the pressure losses. If the diameter of the mandrel is increased, the space between the mandrel and the borehole wall will be decreased and increase resistance to flow between the mandrel and borehole wall. This will result in an increased pressure required to circulate fluids. If the washpipe diameter is decreased to compensate for coil diameter change, the inside diameter of the reduced washpipe will cause a pressure loss inside the drillstring, increasing the required pump pressure to circulate fluids. Decreasing the washpipe diameter can also cause problems when an operator wants to access the lower part of the drillstring with a wireline to access tools, or even dropping darts and ball to activate other tools.

[0023] The present invention shows a flexible length of cable held in place by a rubber or other flexible material. The shape of the cable is serpentine and is shaped/adapted to fit between the mandrel and the washpipe. This serpentine shape allows for a change in length but does not require a change in diameter or extra reserved annular space between the mandrel and the washpipe to compensate for changing diameters. The serpentine cable can be cast into a strip of rubber or other flexible material such as EPDM and can be pre-loaded with a certain amount of stretch to compensate for changes in length, both lengthening and shortening. Some of these materials have an elasticity of several hundred percent and can be used again and again. The combination of the cable and the rubber material can also be in the form of a lattice. The preloaded stretch on the lattice is high enough to contract with sufficient speed if a tool like a drilling jar is fired and a fast-contracting effect is required. The lattice itself will have enough length and elasticity to be able to compensate for any change in length without the lattice being exposed to changes that go beyond the materials' elastic limit. Further, the rubber strip or lattice, in combination with the mandrel and the washpipe, is formed like a half shell so it fits into the annular space between the mandrel and the washpipe. The cable or conductor is enclosed in a hardened rubber or metal shield that is flexible enough to be formed into the half shell between the mandrel and the washpipe.

[0024] The upper part of the rubber strip or lattice is fixed to the mandrel or the washpipe by a bolt or other fixture device. The lower part of the rubber strip or lattice is fixed to the lower mandrel on the opposite side of the moving parts, i.e. the splined drive. This way, the flexible part of the rubber strip or lattice is free to move in synchrony with the splined drive. The lower part of the cable or conductor can also be fixed to an even lower part of the drillstring in order to cross one or more moving parts without losing power or signal. The thickness of the cable or conductor can be adjusted to what the end user requires. If a thicker cable or conductor is required, the serpentine part of the cable or conductor can be elongated to suit requirements. Further, if a longer axial movement or flexibility is required, the rubber strip or lattice can be elongated as needed.

[0025] FIG. 1 depicts some of the main aspects of the invention. The mandrel (1) has a washpipe (2) mounted inside it. The mandrel (1) and washpipe (2) can move independently of each other. The washpipe (2) has a threaded upper end (9) that can be mechanically connected to a upper string member. This string member is not shown as it is not part of the present invention. Between the mandrel (1) and washpipe (2), a flexible cable (4) is cast into a rubber strip (3). The rubber strip (3) and serpentine cable (4) can be flexible in length when stretched. The rubber strip (3) has a fixing hole (5) that allows it to connect to a fixing hole (11) in the washpipe (2). Further, the rubber strip has a fixing hole in the upper end (7) that allows it to be connected to the mandrel (1) through another fixing hole (10). This way, any axial movement between the mandrel (1) and washpipe (2) will cause the rubber strip (3) and serpentined cable (4) to stretch or contract in unison. The lower part of the rubber strip (3) does not necessarily have to be connected to fixing holes (7) and (10). In most cases in tools such as a drilling jar, there is another part of a tool that has a variable length. In order to compensate for this variation of length, the fixing holes (7) and (10) are not used, but instead, there is an elongation of the cable (6) that is elongated past the tools variable length section and is fixed to the bottom of the tool with variable length properties. The functionality is the same, but the lower fixing point has been moved further down the string.

[0026] FIG. 2 depicts details of the rubber strip (3) and serpentine cable (4). When the length of the mandrel (1) and washpipe (2) is changed, the rubber strip (3) will elongate or contract as required, without changing the length of the serpentine cable (4). The fixing point (5) in the upper part of the rubber strip (4) fixes the rubber strip (4) to the washpipe. The lower fixing point does not have to be used if a further tool with variable length is in the immediate closeness to the present invention. Then an elongated cable (6) is elongated past the other variable length parts and fixed to the bottom of the tool. Further, an elongated cable (8) in the upper part of the rubber strip (3) can be elongated to an upper connection point that is not part of the tool. A further possibility is that neither fixing holes (5) and (7) are used and the cable elongations 6 and 8 are fixed to other tools with cable connections.

[0027] FIGS. 3 and 4 shows the assembled tool in relaxed and extended position. In this view, one can see how the rubber strip (3) and serpentine cable (4) elongate and contract as the mandrel (1) and washpipe (2) move apart or together. Further, the rubber strip (3) and serpentine cable (4) can have tension preloaded in such a way that it will contract much faster than if it did not have preloaded tension.

[0028] FIG. 5 shows preferred embodiment of the invention, where the mandrel (1) and washpipe (2) connected at the upper end and by not using fixing holes (7) and (10) and by using the elongated cable (6) to fix the lower end to the lower part of the variable length tool, the mandrel has threads (12 and 13) in each end of mandrel (1) that allows it to the connected to bother the upper part of the string, but also the lower part of the string.