Downhole cable having a protective sheath

Abstract

The invention relates to a downhole cable (1) and to a method for producing a downhole cable (1) which can be used for transmitting data or measured values and / or electrical energy. The downhole cable (1) comprises a cable sheath (2) and a first cable harness (3) received within the cable sheath (2), wherein the first cable harness (3) has a first protective tubing (5) and at least one first fibre (6) received or arranged within the first protective tubing (5). The first cable harness (3) is embedded in a protective sheath (9) over the entire axial length of the downhole cable (1), wherein the protective sheath (9) is formed by components which comprise filaments or a powder and a binding resin.

Description

[0001] BOREHOLE CABLE WITH A PROTECTIVE SHEATH

[0002] The invention relates to a borehole cable for transmitting data or measured values ​​and / or for transmitting electrical energy.

[0003] EP3362834B1 and US10825584B2 disclose an optical fiber cable and a borehole cable, respectively. The cables disclosed in these documents have the disadvantage that their reusability or multiple use is severely limited, particularly due to the high stresses encountered during use in natural gas or oil wells.

[0004] The object of the present invention was to overcome the disadvantages of the prior art and to provide a borehole cable and a method for producing a borehole cable, wherein the borehole cable has improved robustness with respect to stresses in natural gas or oil wells or during insertion into a borehole and removal from a borehole, so that increased reusability is possible.

[0005] This object is achieved by a device and a method according to the claims.

[0006] The borehole cable according to the invention for transmitting data or measured values ​​and / or electrical energy comprises a cable sheath and a first cable strand accommodated within the cable sheath. The first cable strand comprises a first protective tube and a first fiber accommodated or arranged within the first protective tube. At least the first cable strand is embedded in a protective sheath over the entire axial length of the borehole cable, in particular fully embedded, wherein the protective sheath is formed from components which comprise threads or a powder and a resin. The protective sheath is molded onto the first cable strand and is preferably formed integrally and in one piece.

[0007] A single fiber can be understood as a cable for transmitting data or electrical energy. For example, a fiber optic cable or a cable or conductor for conducting electrical energy can be understood as a single fiber. A downhole cable can be used in boreholes, such as natural gas or oil wells, as well as in underground energy storage or geothermal wells.

[0008] Furthermore, the cable sheath is the radially outermost layer of the borehole cable, whereby the cable sheath offers protection against external stresses, such as chemical or mechanical stress.

[0009] A cable harness is also understood to mean one of possibly several cable harnesses, which cable harness is formed along the entire axial length of the borehole cable. A cable harness or the at least one cable harness can comprise at least the first protective tube. The protective tube is a hollow tube, which can be formed, for example, from a metallic alloy, and in whose interior the at least one first fiber can be accommodated.

[0010] At least the first cable harness is embedded in the protective sheath, or the at least one first cable harness can be molded onto the protective sheath. The protective sheath completely surrounds the at least one cable harness, so that the protective sheath is designed as an insulating layer between the first cable harness and the cable sheath.

[0011] The resin of the protective sheath can, for example, be a synthetic resin or binding resin that cures through heat or UV radiation, which penetrates the threads or powder during the production of the protective sheath. This allows the protective sheath to be molded at least onto the first cable strand. Ultimately, the cable sheath completely encloses the protective sheath, and preferably, the cable sheath can be in full contact with the protective sheath.

[0012] This results in, among other advantages, that the elastic properties of the borehole cable are improved by the protective sheath compared to a borehole cable without a protective sheath. Since boreholes generally do not have to be designed in a straight line, and thus a borehole cable inserted into a borehole sometimes experiences significant deflections and thus deformations, the borehole cable according to the invention offers the advantage of reducing plastic deformations during insertion and removal of the borehole cable. This creates the possibility of repeated reusability of the borehole cable, which particularly improves the economic efficiency of operating a borehole when using the borehole cable according to the invention.

[0013] In synergy with this, the protective sheath, in addition to the cable sheath, offers a further layer of protection for the at least one cable strand or, under certain circumstances, for the possibly multiple cable strands of the borehole cable with regard to chemical stress in a borehole. For example, hydrogen diffusion into the at least one cable strand can be reduced, which on the one hand increases the service life of the borehole cable by reducing hydrogen embrittlement over the service life of the borehole cable and, on the other hand, provides security against faulty data transmission if the first fiber is designed as a data transmission line. Security against faulty data transmission is improved, for example, in the case of a fiber optic cable as a data transmission line in that the reduced hydrogen diffusion prevents darkening of the fiber optic cable due to penetrating hydrogen.Hydrogen embrittlement is also understood to be the process in which hydrogen is embedded in crystalline structures through diffusion processes and thus leads to a change in their properties, in particular to embrittlement of the structure.

[0014] Furthermore, the inventive design of the borehole cable with the protective sheath improves the tensile strength of the borehole cable, which in turn improves the reusability, despite high loads during insertion into and removal from a borehole, compared to conventional borehole cables without the inventive protective sheath.

[0015] Furthermore, it can be expedient if the borehole cable comprises a second cable strand accommodated within the cable sheath, wherein the second cable strand comprises a second protective tube and a second fiber accommodated or arranged within the second protective tube, wherein the first cable strand and the second cable strand are embedded in the protective sheath over the entire axial length of the borehole cable. The protective sheath can be molded onto the first cable strand and the second cable strand, or can completely enclose the cable strands. The integration of the second cable strand increases the tensile strength of the borehole cable. Since both cable strands are embedded in the protective sheath, in particular are completely embedded therein or molded thereon, a multi-part composite is created, which results in advantageous properties with regard to elasticity and / or strength, particularly with regard to bending stress on the borehole cable.the elastic limit of the borehole cable. This allows for improved compensation of internal shear forces via the protective sheath when the borehole cable is subjected to bending stress. The elastic limit of the borehole cable as a whole is thus increased, reinforcing the previously described beneficial effects and ensuring economical and safe use of the borehole cable in boreholes.

[0016] Furthermore, it can be provided that the first cable strand and the second cable strand are twisted or stranded together and accommodated or arranged within the cable sheath. In the production of this embodiment of the borehole cable, the two cable strands are stranded before being sheathed with the protective sheath. The protective sheath thus completely transforms or surrounds the two stranded cable strands. Since the cable strands are stranded together, the stranding has the advantageous effect that the first fiber is excessively long relative to the axial extent of the borehole cable. This excessive fiber length is particularly advantageous since the borehole cable according to the invention can be exposed to high temperatures of up to 900°K during use, wherein the first fiber can have a different coefficient of thermal expansion than the first protective tube or the cable sheath.On the one hand, the linear expansion of the borehole cable due to heat effects is already partially compensated for by the provision of the protective sheath. However, it is advantageous if the safety of the borehole cable is further increased, since the fiber excess length of the first fiber relative to the axial extension of the borehole cable allows, within certain limits, a difference between the absolute linear expansion due to heat effects between the first fiber and the borehole cable. This further increases the safety of the borehole cable and also broadens the application spectrum with regard to external loads acting on the borehole cable, which improves the cost-effectiveness of the borehole cable.

[0017] Furthermore, it can be provided that the borehole cable comprises at least one third cable strand accommodated within the cable sheath, wherein the third cable strand comprises a fourth protective tube and a third fiber accommodated or arranged within the fourth protective tube, wherein the first cable strand, the second cable strand, and the third cable strand are embedded in the protective sheath over the entire axial length of the borehole cable. The integration of the third cable strand further increases the tensile strength of the borehole cable. Since all cable strands are embedded in the protective sheath, in particular are fully embedded therein or are molded onto it, a multi-part composite is created.In particular, the integration of all three cable strands into the protective sheath increases the radially outer surface of the cable strands, which are formed by the protective sheath, creating an improved material bond that reinforces the advantageous properties already described above. Thus, when the borehole cable is subjected to bending stress, internal shear forces can be compensated for more effectively via the material bond between the protective sheath and the cable strands, while simultaneously improving the tensile strength of the borehole cable.

[0018] Another advantageous embodiment is one in which the first cable strand, the second cable strand, and the third cable strand are twisted or stranded together and accommodated or arranged within the cable sheath. Twisting three cable strands together results in several advantages. The tensile strength of the borehole cable is increased, while the radially outer circumferential surface of the cable strands, which is shaped by the protective sheath, is nevertheless almost completely embedded in the protective sheath. This preserves the advantageous mechanical properties of the combination of cable strands and protective sheath. Mechanical properties can include, for example, the plastic and elastic properties, as well as flexural properties, or properties relating to the robustness and resistance to mechanical loads of the borehole cable.Furthermore, the stranding of the cable strands creates an excess length of the first fiber relative to the borehole cable, which is inherent in the stranding process. This improves the application versatility of the borehole cable and its robustness against thermal stress.

[0019] According to a further development, it is possible for the second fiber to be an electrical conductor. The provision of an electrical conductor increases the usability of the borehole cable for a wide variety of applications. The electrical conductor or the second fiber can be designed such that the electrical conductor is embedded in an insulating layer, preferably made of a plastic material, wherein the outer diameter of the insulating layer surrounding the electrical conductor corresponds to an inner diameter of the second protective tube. This utilizes the full cross-section of the second protective tube, which, since the electrical conductor is metallic, subsequently improves the tensile strength of the borehole cable.

[0020] Furthermore, it may be advantageous for the third fiber to be an electrical conductor. This further improves the application versatility and tensile strength of the borehole cable, as previously explained.

[0021] Furthermore, the first fiber can be an optical fiber or a vacuum core optical fiber. This enables data transmission into and out of the borehole, increasing the application versatility of the borehole cable. Particularly with regard to the protective sheath designed according to the invention, the use of a fiber optic cable as the first fiber is expedient, since the protective sheath offers a thermal and chemical insulation layer as well as a mechanical protection layer, particularly with regard to transverse pressures on the borehole cable. Since the fiber optic cable can also be used for monitoring the condition of the borehole using special measuring methods, this provides a further advantage in addition to the enabled data transmission with regard to safe operation of a borehole using the borehole cable according to the invention.

[0022] In particular, it may be advantageous if the first fiber or fiber optic cable has an initial fiber overlength relative to the unstacked or untwisted first protective tube in a range of 0.1% to 5%, in particular 0.5% to 1.5%. As already explained above, this increases the possible and safe application range of the borehole cable with regard to high ambient temperatures, since the initial fiber overlength compensates for the difference between the different thermal expansions between the fiber optic cable and the borehole cable, preventing the fiber optic cable from breaking.

[0023] Furthermore, it can be provided that the twisted cable strands have a lay length, which lay length is selected from a range comprising 20 mm to 120 mm, in particular 50 mm to 70 mm. This is advantageous because the tensile strength of the borehole cable is improved by the appropriate stranding of the cable strands together. Synergistically, the stranding creates a fiber excess length that adds up to the initial fiber excess length up to a resulting fiber excess length in stranded cable strands. A further synergistic effect with regard to the protective sheath arises in that the protective sheath prevents, within certain limits, a change in the lay length, for example in areas of strong deflections of the borehole cable in a borehole or during the insertion and removal of the borehole cable.This is advantageous in terms of secure data transmission or secure condition monitoring of the borehole using the fiber optic cable.

[0024] The lay length refers to the pitch of the helically laid cable strands. The lay length is thus a linear measure of the axial extent of the borehole cable, the length over which a cable strand exhibits a complete 360° turn of the helix. For the borehole cable in question, the lay direction is irrelevant in this context. However, it should be noted that the lay length of the individual stranded cable strands can be essentially identical.

[0025] According to a special embodiment, it is possible for the threads or powder to be made of a mineral, ceramic, or carbon-containing first material. Thus, the insulation properties and elasticity of the protective sheath can be adjusted depending on the application.

[0026] According to an advantageous development, the first material can be a mixture of silicates and / or feldspar and / or olivine. This advantageously influences the temperature resistance of the protective sheath, which subsequently improves the thermal resilience of the borehole cable. Accordingly, the application spectrum of the borehole cable is expanded and the reusability of the borehole cable is improved depending on the application. In combination with the use of a binding resin specifically tailored to the first material, the resistance to thermal stress can be further improved.

[0027] In particular, it can be advantageous if the first material contains basalt. This makes the borehole cable more resistant to high transverse pressures and hydrostatic pressure loads. Furthermore, the elastic limit of the borehole cable is increased, which reduces plastic deformation of the borehole cable compared to a conventional borehole cable without a protective sheath and with a basalt-containing first material. This, in turn, improves the reusability of the borehole cable.

[0028] Furthermore, it can be provided that the first fiber, in the stranded state of the first cable strand, has a resulting fiber excess length, wherein the resulting fiber excess length relative to the length of the borehole cable is selected from a range comprising 0.1% to 3%, in particular 0.5% to 1.5%. With regard to thermal stress, this enables the use of the borehole cable up to temperatures of up to 900°K, since the advantageous effects of the protective sheath or the basalt-containing protective sheath in combination with the resulting fiber excess length of the first fiber or the glass fiber compensate for the difference in length expansion due to thermal effects.

[0029] Another advantageous embodiment provides for at least two contact surfaces or touch surfaces to be formed over an axial length of one meter of the borehole cable between the first fiber and an inner surface of the first protective tube under normal conditions and with an unstacked first cable strand that is straight in the axial direction. Normal conditions are understood to mean an ambient temperature of 273 °K and an ambient pressure of 1013.25 mbar. Since the first fiber is subjected to tensile stress due to its own weight, particularly when the borehole cable is aligned vertically, this stress on the first fiber can be reduced via the contact surfaces. Provision can be made for the first fiber to be arranged in the first protective tube, for example, in a spiral shape running in the longitudinal direction of the borehole cable. This ensures that the touch surfaces are formed.Accordingly, this arrangement results in a fiber excess length of the length of the first fiber relative to the length of the borehole cable.

[0030] Furthermore, it can be provided that the first fiber has a resulting fiber excess length compared to the first protective tube, so that a resulting frictional force is formed at the contact surfaces between the first fiber and the first protective tube over the axial length of the borehole cable when the borehole cable is positioned vertically and under normal conditions, wherein the resulting frictional force is in the range between 30% and 200%, in particular at least 70% of the dead weight of the first fiber. This supports the first fiber so that it is not at risk of tearing due to its own weight when the borehole cable is positioned vertically. This is advantageous in that the usable length of the borehole cable is increased, which in turn increases its application diversity.In particular, when the cable strands are stranded together, additional support surfaces for the first fiber are created by the first cable strand being arranged spirally in the longitudinal direction of the borehole cable.

[0031] According to a further development, it is possible for a fluid or gel to be accommodated or arranged within the first protective tube. In particular, it can be advantageous if the fluid is a thixotropic gel. This can further increase the protection of the first fiber or a glass fiber. In particular, the protection of a glass fiber against darkening caused by hydrogen can be improved, especially in underwater applications or at high temperatures and correspondingly increased hydrogen diffusion in boreholes for natural gas or oil production. This increases the service life or lifetime of the borehole cable, which in turn improves its cost-effectiveness. In addition to the barrier effect, the friction coefficient at the contact surfaces between the inner surface of the first protective tube and the first fiber can also be influenced.

[0032] Furthermore, it may be expedient for the first cable harness to comprise a third protective tube, with an electrical conductor accommodated or arranged within the third protective tube. In this case, the third protective tube may be arranged within the first protective tube, but it may also be arranged, for example, next to the first protective tube and in contact with it. It is advantageous in this case that, for example, a control voltage or additional electrical power can be provided in the borehole via the additional electrical conductor. This allows the borehole cable to be used multifunctionally, broadening its application spectrum.

[0033] Furthermore, it can be provided that the first cable harness comprises a protective tube sheath, wherein the protective tube sheath surrounds the first protective tube in a form-fitting and / or frictional manner or is molded around the first protective tube. This improves the barrier effect for protecting the first fiber arranged in the first protective tube. Furthermore, the tensile strength of the borehole cable is improved. The adhesion of the protective sheath to the first cable harness can also be improved by appropriately selecting the material of the protective tube sheath.

[0034] Furthermore, the first protective tube and the cable sheath may be made of metallic alloys. This improves the protection against mechanical and chemical stress, the barrier effect for protecting the first fiber, and the tensile strength of the downhole cable.

[0035] Specifically, the borehole cable according to the invention is intended for use in oil and gas wells, geothermal wells, or in boreholes for underground energy storage facilities. High thermal, chemical, and mechanical stresses are to be expected in oil and gas wells. For example, severe deformation or bending of the borehole cable can occur during insertion into a borehole. These stresses can also occur during removal from the borehole. Accordingly, the design of the borehole cable according to the invention enables reusability after use in a borehole.

[0036] During the operation of a borehole, the borehole cable must withstand thermal and chemical stresses, and a fiber optic cable arranged in the first protective tube must be protected in such a way that secure data transmission or continuous monitoring of the borehole condition is ensured. The borehole cable according to the invention meets these requirements, and the inventive design of the borehole cable improves its properties to ensure safer and more economical operation in oil and gas wells. The same applies to the use of the borehole cable according to the invention in geothermal wells. The borehole cable according to the invention also offers the same advantageous effects for underground energy storage systems, such as redox flow storage systems.

[0037] The invention further relates to a method for producing a borehole cable comprising the following method steps:

[0038] - Providing a first cable harness comprising a first protective tube;

[0039] - inserting a first fiber into the first protective tube;

[0040] - Providing at least one second cable harness, the at least one second cable harness comprising a second protective tube, wherein a second fiber is accommodated within the second protective tube;

[0041] - Stranding or twisting the cable strands, wherein by means of the twisting a resulting fiber excess length of the first fiber relative to the borehole cable or to the longitudinal extent of the borehole cable is formed from a range comprising 0.1% to 3%, in particular 0.5% to 1.5%;

[0042] - Sheathing or forming the stranded cable strands with a protective sheath, wherein the stranded cable strands are in particular embedded in the protective sheath and wherein the protective sheath is formed from threads or powder made of a mineral, ceramic or carbon-containing first material and from resin or from a curable binding resin by means of a pultrusion process, extrusion process or a similar process;

[0043] - Coating the protective sheath with a cable sheath. The advantage here is that the method according to the invention makes it possible to produce a borehole cable with a protective sheath whose mechanical properties are improved by the protective sheath compared to a borehole cable without a protective sheath. The mechanical properties can be understood to mean, for example, the plastic and elastic properties as well as flexural properties or properties relating to the robustness and resistance to mechanical loads of the borehole cable. Since boreholes generally do not have to be linear and thus a borehole cable inserted into a borehole sometimes experiences significant deflections and thus deformations, the borehole cable produced by the method according to the invention has the advantage that the plastic deformations during insertion into a borehole and during removal from the borehole are reduced.Thus, the possibility of repeated reusability of the borehole cable is created, which in particular improves the economic efficiency of the operation of a borehole when using the borehole cable according to the invention.

[0044] In synergy with this, the protective sheath, in addition to the cable sheath, offers an additional layer of protection for the cable strands of the borehole cable with regard to chemical stresses in a borehole. For example, hydrogen diffusion into the at least one cable strand can be reduced, which on the one hand increases the service life of the borehole cable by reducing hydrogen embrittlement over the service life of the borehole cable and on the other hand provides security against faulty data transmission, provided the first fiber is embodied as a data transmission line or as a fiber optic cable. Security against faulty data transmission is improved, for example, with a fiber optic cable as a data transmission line in that the reduced hydrogen diffusion prevents darkening of the fiber optic cable due to penetrating hydrogen.Hydrogen embrittlement is also understood to be the process in which hydrogen is embedded in crystalline structures through diffusion processes and thus leads to a change in their properties, in particular to embrittlement of the structure.

[0045] Furthermore, the method according to the invention makes it possible to produce a borehole cable with a protective sheath whose tensile strength is improved, which in turn improves reusability compared to conventional borehole cables without a protective sheath, despite high loads during insertion into and removal from a borehole. Also advantageous is a design according to which it can be provided that when inserting the first fiber into the first protective tube, an initial fiber excess length of the first fiber relative to the length of the first protective tube is introduced from a range comprising 0.1 %o to 5 %o, in particular 0.5 %c to 1.5 %c. As a result, the resulting fiber excess length is further increased due to the stranding of the cable strands together, since the stranding per se already sets a fiber excess length compared to the unstacked state of the first cable strand, depending on the applied lay length.This allows the borehole cable to be used at temperatures up to 900 °K, as the advantageous effects of the protective sheath, combined with the resulting excess fiber length of the first fiber, compensate for the difference in linear expansion caused by thermal effects between the borehole cable and the first fiber. Synergistically, the lay length can be increased according to the initial excess fiber length to ultimately achieve the desired resulting excess fiber length of the first fiber relative to the length of the borehole cable.

[0046] According to a further development, it is possible to use an optical fiber or a vacuum core optical fiber as the first fiber. This enables data transmission into and out of the borehole, increasing the application versatility of the borehole cable. The use of a fiber optic cable as the first fiber is particularly advantageous with regard to the protective sheath, as the protective sheath provides a thermal and chemical insulation layer as well as a mechanical protection layer, particularly with regard to transverse pressures on the borehole cable. Since the fiber optic cable can also be used with special measuring methods to monitor the condition of the borehole itself, particularly along its longitudinal extent, this provides a further advantage in terms of safe borehole operation in addition to the data transmission it enables.

[0047] Furthermore, it can be expedient to set a lay length within a range of 20 mm to 120 mm, in particular 50 mm to 70 mm, when stranding the cable strands. This is advantageous because the appropriate stranding of the cable strands improves the tensile strength of the borehole cable. Synergistically, the stranding creates a fiber excess length that adds to the initial fiber excess length, resulting in a resulting fiber excess length in stranded cable strands. A further synergistic effect with regard to the protective sheath is that the protective sheath prevents or, to a certain extent, reduces changes in the lay length, for example, in areas of strong deflections of the borehole cable in a borehole or during insertion and removal of the borehole cable. This is advantageous with regard to secure data transmission or secure condition monitoring of the borehole using the fiber optic cable.

[0048] Furthermore, a mixture of silicates and / or feldspar and / or olivine can be used as the first material. This has a beneficial effect on the temperature resistance of the protective sheath, which subsequently improves the thermal resilience of the borehole cable. Accordingly, the application spectrum of the borehole cable is expanded and its reusability is improved depending on the application. In combination with the use of a binding resin specifically tailored to the first material, the resistance to thermal stress can be further improved.

[0049] Furthermore, it can be provided that a basalt-containing material is used as the first material. This makes the borehole cable more resistant to high transverse pressures and hydrostatic pressure loads. Furthermore, the elastic limit of the borehole cable is increased, which reduces plastic deformation of the borehole cable compared to a conventional borehole cable without a protective sheath and with a basalt-containing first material. This again improves the reusability of the borehole cable.

[0050] According to a special variant, it is possible that the sheathing of the stranded cable strands with the protective sheath comprises the following process steps:

[0051] - wrapping or spinning the stranded cable strands with threads made of the first material or wetting or coating the stranded cable strands with powder made of the first material;

[0052] - Soaking or impregnating the cable strands wrapped or coated with the first material with resin or a curable binding resin in a resin bath or with an impregnation tool;

[0053] - Curing the resin by heating or UV curing.

[0054] These process steps enable the protective sheath to be manufactured as technically simple and cost-effectively as possible. Furthermore, this ensures that the cable harnesses are fully embedded in the protective sheath or even molded onto it. Since all cable harnesses are embedded in the protective sheath, in particular, fully embedded in it or molded onto it, a multi-part composite is created. In particular, the integration of all cable harnesses into the protective sheath increases the radially outer surface of the cable harnesses that are surrounded by the protective sheath, creating an improved material bond that reinforces the advantageous properties already described.In this way, when the borehole cable is subjected to bending stress, internal shear forces can be compensated in an improved manner via the material bond between the protective sheath and the cable strands, while at the same time the tensile strength of the borehole cable is improved.

[0055] According to an advantageous development, it can be provided that a third cable strand with a fourth protective tube and a third fiber accommodated therein is provided before the stranding of the cable strands, wherein the first cable strand, the second cable strand, and the third cable strand are stranded together during the stranding of the cable strands. In particular, it can be advantageous if an electrical conductor is used as the second fiber and as the third fiber. This allows the tensile strength of the borehole cable to be further increased, while at the same time, another fiber is provided, for example, as an electrical conductor for transmitting electrical power.

[0056] For a better understanding of the invention, it is explained in more detail using the following figures.

[0057] They show in a highly simplified, schematic representation:

[0058] Fig. 1 shows a possible design of a borehole cable;

[0059] Fig. 2 shows a cross-section of the borehole cable;

[0060] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference numerals or identical component designations, whereby the disclosures contained in the entire description can be transferred mutatis mutandis to identical parts with identical reference numerals or identical component designations. The position information chosen in the description, such as top, bottom, side, etc., also relates to the directly described and illustrated figure, and these position information is to be transferred mutatis mutandis to the new position in the event of a position change. Fig. 1 shows one possible embodiment of a borehole cable 1. The borehole cable 1 comprises a cable sheath 2 for protecting the borehole cable 1 from external chemical or mechanical stresses. A first cable strand 3 and at least one second cable strand 4 can be accommodated within the cable sheath 2.The first cable harness 3 can comprise a first protective tube 5, wherein at least one first fiber 6 can be accommodated within the first protective tube 5. The at least one first fiber 6 can be a glass fiber or a vacuum core optical fiber or a similar fiber based on optical fiber technology for data transmission. Furthermore, it can be provided that the at least one first fiber 6 is embedded in a gel or a thixotropic fluid or gel within the first protective tube 5, or is at least wetted by the gel.

[0061] The second cable harness 4 may comprise a second protective tube 7, in which a second fiber 8 is accommodated. The second fiber 8 may be formed as an electrical conductor with a full-circumferential insulation layer.

[0062] The first cable strand 3 and the second cable strand 4 can be stranded or twisted together. In this case, it can be provided that the cable strands 3, 4 have a lay length in the stranded state ranging from 20 mm to 120 mm, in particular from 50 mm to 70 mm. The two cable strands 3, 4 can each have a substantially circular cross-section, whereby the cable strands 3, 4 can thus touch each other in the stranded state along a spiral contact line that runs along the length of the borehole cable.

[0063] The borehole cable 1 can further comprise a protective sheath 9. The protective sheath 9 can be accommodated within the cable sheath 2, wherein the cable sheath 2 can be designed to completely enclose the protective sheath 9 and to touch the protective sheath 9 at its outer diameter. The cable strands 3, 4 can be completely embedded in the protective sheath 9, so that the protective sheath 9 has an insulating effect with respect to the cable sheath 2 and so that, if possible, no cavities are formed between the cable sheath 2 and the cable strands 3, 4, provided this is technically feasible within the scope of the manufacturing possibilities of the protective sheath 9. The protective sheath 9 can be made of at least two components. A first component can be formed from powder or threads, which powder or threads are formed from a first material. A second component can be formed from a resin or a curable synthetic resin.The production of the protective sheath 9 can comprise the following method steps: Providing the twisted cable strands 3, 4. Encasing the twisted cable strands 3, 4 with threads made of the first material and / or coating with or applying powder made of the first material in order to fill spaces between the twisted cable strands 3, 4 and to produce a specified outer diameter of the protective sheath 9;.

[0064] Subsequently, the resin or the curable synthetic resin can be introduced into the already produced casing made of the first material and cured using a pultrusion process;

[0065] As an alternative to a pultrusion process for sheathing the cable harnesses 3, 4 or for producing the protective sheath 9, an extrusion process can also be used.

[0066] In this way, the twisted cable strands 3, 4 can be completely embedded in the protective sheath 9 over the entire axial length of the borehole cable 1 or the protective sheath 9 can be molded onto the cable strands 3, 4, whereby a material connection can be established between the outer diameters of the cable strands 3, 4 and the protective sheath 9.

[0067] The first material can be a mineral, ceramic, or carbonaceous material, with a mixture of silicates and / or feldspar and / or olivine being particularly conceivable. It can further be provided that the first material, in particular, contains basalt, whereby desired insulation, barrier, and elastic properties of the borehole cable 1 can be achieved. In particular, by molding the protective sheath 9 onto the twisted cable strands 3, 4, the mechanical properties, in particular the elastic-plastic properties of the borehole cable 1, can be advantageous. Mechanical properties can be understood, for example, as the plastic and elastic properties, as well as bending properties, or properties relating to the robustness and resistance to mechanical stress of the borehole cable 1.

[0068] Fig. 2 shows a further and possibly independent embodiment of the borehole cable, wherein again the same reference numerals or component designations as in the previous Fig. 1 are used for the same parts. Fig. 2 shows a cross-section of the borehole cable. The first fiber 6 can already be introduced into an untwisted first protective tube 5. The introduction into the first protective tube 5 can be accomplished in such a way that the fiber 6 is unwound from a take-off disk or a spool and, after initial insertion into the first protective tube 5, is pulled from the take-off disk into the first protective tube 5 by the friction occurring between the first protective tube 5 and the first fiber 6 during continuous production.When inserting the first fiber 6 into the first protective tube 5, an initial fiber overlay relative to the untwisted first protective tube 5 can be introduced from a range comprising 0.1% to 5%, in particular 0.5% to 1.5%. By stranding or twisting the first cable strand 3 with the second cable strand 4, a resulting fiber overlength of the first fiber 6 relative to the borehole cable 1 can be achieved from a range comprising 0.1% to 3%, in particular 0.5% to 1.5%.

[0069] By appropriately providing the resulting excess fiber length of the first fiber 6 relative to the borehole cable 1, the borehole cable 1 can have at least two contact surfaces 11 or contact surfaces between the first fiber 6 and an inner surface 10 of the first protective tube 5 over an axial length of one meter. If the borehole cable 1 is aligned vertically in its axial direction, a frictional force resulting at the contact surfaces 11 between the first fiber 6 and the inner surface 10 of the first protective tube 5 can be in the range between 30% and 200%, in particular at least 70% of the dead weight of the first fiber 6. It is further conceivable for the first fiber 6 to have a coating on its outer diameter, by means of which the resulting frictional force can be varied by changing the friction coefficient in accordance with specific application requirements of the borehole cable 1.The coefficient of friction can also be adjusted by appropriately selecting a gel that may be provided inside the first protective tube 5.

[0070] The specified value ranges for the initial excess length, the resulting excess length, and the resulting friction force refer specifically to standard conditions at an ambient temperature of 273 °K and an ambient pressure of 1013.25 mbar. Due to different coefficients of linear expansion of the first fiber 6 and the first protective tube 5 or the borehole cable 1, the resulting fiber excess length and the resulting friction force are naturally subject to variation when deviating from standard conditions.

[0071] Since the protective sheath 9 can contain basalt, corresponding to the first material used for the threads or powder, the protective sheath 9 can also be referred to as a basalt sheath. The basalt sheath can, as previously described, be molded onto the cable strands 3, 4, or the cable strands 3, 4 can be completely enclosed in the basalt sheath. In conjunction with the cable sheath 2, the elastic limit can thus be increased compared to a conventional borehole cable without a basalt sheath. In any case, the basalt sheath or the protective sheath 9 can be formed as a single piece.

[0072] The first protective tube 5 and the cable sheath 2 can be made of metallic alloys. Independently of this, the second protective tube 7 can be made of a metallic alloy or an insulating plastic.

[0073] Furthermore, it is conceivable for the first cable harness 3 to comprise a third protective tube, wherein an electrical conductor is accommodated or arranged within the third protective tube. Provision can be made for the third protective tube to be arranged so as to run essentially axially parallel to the first protective tube 5. However, it is also conceivable for the third protective tube to be arranged within the first protective tube 5.

[0074] Independently of this, it can further be provided that the first protective tube 5 has a protective tube casing 12. The protective tube casing 12 can be made of aluminum, wherein the first protective tube 5 is completely covered by the protective tube casing 12.

[0075] Furthermore, it can also be provided that the borehole cable 1 comprises a third cable strand 13 with a fourth protective tube 14, wherein a third fiber 15 is accommodated in the fourth protective tube 14. The third cable strand 13 can be stranded with the first cable strand 3 and the second cable strand 4, wherein the stranded cable strands 3, 4, 13 can be embedded in the protective sheath 9. Independently of this, it can be provided that the third fiber 15, like the second fiber 8, can be designed as an electrical conductor. The third cable strand 13 can essentially be structurally identical to the first cable strand 3.

[0076] The exemplary embodiments show possible embodiments. It should be noted at this point that the invention is not limited to the specifically illustrated embodiments. Rather, various combinations of the individual embodiments are also possible. This variation possibility, based on the teaching of technical action based on the invention in question, lies within the skill of the person skilled in the art. The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various exemplary embodiments shown and described may represent independent inventive solutions in themselves. The problem underlying the independent inventive solutions can be derived from the description.

[0077] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0078] For the sake of clarity, it should finally be pointed out that, in order to better understand the structure, some elements have been shown out of scale and / or enlarged and / or reduced in size.

[0079] Reference symbol list

[0080] Borehole cable Cable sheath First cable strand Second cable strand First protective tube First fiber Second protective tube Second fiber Protective sheath Inner surface Contact surfaces

[0081] S helical sheath third cable harness fourth duct third fiber

Claims

Patent claims 1. Borehole cable (1) for transmitting data or measured values ​​and / or electrical energy, comprising a cable sheath (2) and a first cable strand (3) accommodated within the cable sheath (2), the first cable strand (3) comprising a first protective tube (5) and at least one first fiber (6) accommodated or arranged within the first protective tube (5), characterized in that the first cable strand (3) is embedded in a protective sheath (9) over the entire axial length of the borehole cable (1), the protective sheath (9) being formed from components, the components comprising threads or a powder and comprising a resin.

2. Borehole cable (1) according to claim 1, characterized in that the borehole cable (1) comprises at least one second cable strand (4) accommodated within the cable sheath (2), wherein the second cable strand (4) comprises a second protective tube (7) and a second fiber (8) accommodated or arranged within the second protective tube (7), wherein the first cable strand (3) and the second cable strand (4) are embedded in the protective sheath (9) over the entire axial length of the borehole cable (1).

3. Borehole cable (1) according to claim 2, characterized in that the first cable strand (3) and the second cable strand (4) are twisted or stranded together and are accommodated or arranged within the cable sheath (2).

4. Borehole cable (1) according to claim 2, characterized in that the borehole cable (1) comprises at least one third cable strand (13) accommodated within the cable sheath (2), wherein the third cable strand (13) comprises a fourth protective tube (14) and a third fiber (15) accommodated or arranged within the fourth protective tube (14), wherein the first cable strand (3), the second cable strand (4) and the third cable strand (13) are embedded in the protective sheath (9) over the entire axial length of the borehole cable (1).

5. Borehole cable (1) according to claim 4, characterized in that the first cable strand (3), the second cable strand (4) and the third cable strand (13) are twisted together or are stranded together and are accommodated or arranged within the cable sheath (2).

6. Borehole cable (1) according to claim 2, characterized in that the second fiber (8) is an electrical conductor.

7. Borehole cable (1) according to claim 4, characterized in that the third fiber (15) is an electrical conductor.

8. Borehole cable (1) according to one of the preceding claims, characterized in that the first fiber (6) is an optical fiber or a vacuum core optical fiber.

9. Borehole cable (1) according to claim 3 or 5, characterized in that the twisted cable strands have a lay length, which lay length is selected from a range comprising 20 mm to 120 mm, in particular 50 mm to 70 mm.

10. Borehole cable (1) according to one of the preceding claims, characterized in that the threads or the powder are formed from a mineral, ceramic or carbon-containing first material.

11. Borehole cable (1) according to claim 10, characterized in that the first material is a mixture of silicates and / or feldspar and / or olivine.

12. Borehole cable (1) according to claim 10, characterized in that the first material contains basalt.

13. Borehole cable (1) according to one of claims 3 to 12, characterized in that the first fiber (6) in the stranded state of the first cable strand (3) has a resulting fiber excess length, wherein the resulting fiber excess length relative to the length of the borehole cable (1) is selected from a range comprising 0.1% to 3%, in particular 0.5% to 1.5%.

14. Borehole cable (1) according to one of the preceding claims, characterized in that at least two contact surfaces (11) or contact surfaces are formed over an axial length of one meter of the borehole cable (1) between the first fiber (6) and an inner surface of the first protective tube (5) under normal conditions and with the first cable strand (3) straight and unstacked in the axial direction.

15. Borehole cable (1) according to one of the preceding claims, characterized in that the first fiber (6) has a resulting fiber excess length compared to the first protective tube (5), so that a resulting frictional force is formed on the contact surfaces (11) between the first fiber (6) and the first protective tube (5) over the axial length of the borehole cable (1) when the borehole cable (1) is positioned vertically and under normal conditions, wherein the resulting frictional force is in the range between 30% and 200%, in particular at least 70% of the dead weight of the first fiber (6).

16. Borehole cable (1) according to one of the preceding claims, characterized in that a fluid or a gel is accommodated or arranged within the first protective tube (5).

17. Borehole cable (1) according to claim 16, characterized in that the fluid is a thixotropic gel.

18. Borehole cable (1) according to one of the preceding claims, characterized in that the first cable strand (3) comprises a third protective tube, wherein an electrical conductor is accommodated or arranged within the third protective tube.

19. Borehole cable (1) according to one of the preceding claims, characterized in that the first cable harness (3) comprises a protective tube jacket (12), wherein the protective tube jacket (12) forms the first protective tube (5) in a form-fitting and / or friction-fitting manner or is formed around the first protective tube (5).

20. Borehole cable (1) according to one of the preceding claims, characterized in that the first protective tube (5) and the cable sheath (2) are made of metallic alloys.

21. Use of a borehole cable (1) according to one of the preceding claims, characterized in that the borehole cable (1) is intended for use in oil wells, natural gas wells, geothermal wells or in boreholes for underground energy storage.

22. A method for producing a borehole cable (1) comprising the following process steps: - Providing a first cable harness (3) comprising a first protective tube (5); - Inserting a first fiber (6) into the first protective tube (5) - Providing at least one second cable harness (4), the at least one second cable harness (4) comprising a second protective tube (7), wherein a second fiber (8) is accommodated within the second protective tube (7); - stranding or twisting the cable strands, wherein by means of the twisting a resulting fiber excess length of the first fiber (6) relative to the borehole cable (1) is formed from a range comprising 0.1% to 3%, in particular 0.5% to 1.5%; - Sheathing or forming the stranded cable strands with a protective sheath (9), wherein the protective sheath (9) is formed from threads or powder of a mineral, ceramic or carbon-containing first material and from resin by means of pultrusion processes, extrusion processes or a related process; - Cover the protective sheath (9) with a cable sheath (2).

23. Method according to claim 22, characterized in that when introducing the first fiber (6) into the first protective tube (5), an initial fiber excess length of the first fiber (6) relative to the length of the first protective tube (5) from a range comprising 0.1 %o to 5 %o, in particular 0.5 %c to 1.5 %c, is introduced.

24. Method according to one of claims 22 or 23, characterized in that an optical waveguide or a vacuum core optical waveguide is used as the first fiber (6).

25. Method according to one of claims 22 to 24, characterized in that when stranding the cable strands, a lay length is set from a range comprising 20 mm to 120 mm, in particular 50 mm to 70 mm.

26. A method according to any one of claims 22 to 25, characterized in that a mixture of silicates and / or feldspar and / or olivine is used as the first material.

27. A method according to any one of claims 22 to 26, characterized in that a basalt-containing material is used as the first material.

28. Method according to one of claims 22 to 27, characterized in that the sheathing of the stranded cable strands with the protective sheath (9) comprises the following method steps: - wrapping or spinning the stranded cable strands with threads made of the first material or wetting or coating the stranded cable strands with powder made of the first material; - impregnating or soaking the cable strands wrapped or coated with the first material with resin in a resin bath or with an impregnation tool; - Curing the resin by heating or UV curing.

29. Method according to one of claims 22 to 28, characterized in that a third cable strand (13) with a fourth protective tube (14) and a third fiber (15) accommodated therein is provided before the stranding of the cable strands, wherein during the stranding of the cable strands the first cable strand, the second cable strand and the third cable strand (13) are stranded together.

30. Method according to one of claims 22 to 29, characterized in that an electrical conductor is used as the second fiber (8) and as the third fiber (15).

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