DK2567386T3

DK2567386T3 - Power cable to a topdrivenhed on a drilling rig

Info

Publication number: DK2567386T3
Application number: DK11720250.7T
Authority: DK
Inventors: Matthew Bodziony; Walter Constantine; Damian Billeaudeau; Almir Fonseca Menezes
Original assignee: Draka Holding N V
Priority date: 2010-05-03
Filing date: 2011-05-03
Publication date: 2016-11-07
Also published as: BR112012028242B1; BR112012028242A2; WO2011140034A2; EP2567386B1; WO2011140034A4; EP2567386A2; WO2011140034A3

Description

DESCRIPTION

FIELD OF THE INVENTION

[0001] The present invention relates to an improved top-drive cable, which is particularly useful in petroleum-drilling deployments.

BACKGROUND

[0002] The top-drive assembly in land-based and offshore drilling rigs provides the rotational force needed to drill a borehole. Typically, several cables supply power to the motors within the top-drive assembly.

[0003] In conventional designs, these power cables are positioned within large-diameter rubber hoses with each power cable typically being secured to a rubber hose with a flexible epoxy. Each rubber hose may be clamped to a steel cable, which provides support to the power cables. The rubber hoses protect the power cables from harsh conditions experienced during drilling operations. Indeed, rubber hoses are used to protect the power cables, because conventional cable jackets do not provide sufficient mechanical protection.

[0004] The rubber hoses (and the power cables) typically are suspended from a position about midway on the drilling rig in a service loop. The service loop provides cable slack, thereby allowing the top-drive assembly to vertically reciprocate (/.e., move up and down the drilling rig).

[0005] Because each power cable in conventional designs is secured within a rubber hose (e.g., with an epoxy) that vertically reciprocates corresponding with the movement of the top-drive assembly, it is important for the power cable to be designed for continuous flexing operations. A cable having insufficient flexibility (e.g., not designed for continuous flexing) may suffer from undesirable fatigue and eventually break.

[0006] Furthermore, problems may arise if each power cable is not centered within its rubber hose in the service loop. A power cable that is not centered will have a different loop radius than the rubber hose. Whenever the power cable bends during operation (e.g., caused by the vertical reciprocation of the top-drive assembly), stresses occur in the power cable. Thus, if a power cable is not centered within the rubber hose, it will experience non-uniform stress, which can lead to the premature failure of the cable.

[0007] Another problem of conventional designs is that the power cable may become twisted because of the continuous reciprocation of the top-drive assembly.

[0008] A cable as defined by the preamble of claim 1 is disclosed in CN 201 374 209 Y.

[0009] The conductors within the power cable can also cause undesirable twisting. In addition to the hose, conductors within the power cable partially support the weight of the power cable. These elements, however, elongate at different rates, causing the conductors to become the primary support mechanism of the power cable. This, in turn, can lead to the power cable becoming twisted. Power cables employing a single conductor are particularly susceptible to such twisting. This twisting causes additional stresses in the power cable and eventually premature failure.

[0010] Accordingly, a need exists for an improved top-drive power cable that (i) resists cable rotation and (/7) does not need to be positioned within a rubber hose.

SUMMARY

[0011] Accordingly, in one aspect, the present invention embraces a cable for providing power to a motor of a top-drive as defined by claim 1.

[0012] In another aspect, the present invention embraces a method of supplying power to a top-drive assembly on a drilling rig.

In particular, a top-drive power cable connects the top-drive assembly to a power source.

[0013] The foregoing illustrative summary, as well as other exemplary objectives and/or advantages of the invention, and the manner in which the same are accomplished, are further explained within the following detailed description and its accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]

Figure 1 schematically depicts a cross-sectional view of a top-drive power cable in accordance with one embodiment of the present invention.

Figure 2 schematically depicts a cross-sectional view of a connected pair of top-drive power cables in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION

[0015] In one aspect, the present invention embraces an improved top-drive power cable. In this regard, Figure 1 depicts an exemplary top-drive power cable 10 in accordance with the present invention.

[0016] The power cable 10 includes one or more high-conductivity conductors 11. In one embodiment, the power cable 10 includes high-conductivity conductors 11 of different sizes. The larger diameter conductors 11a may be used as power conductors and the smaller diameter conductors 11b may be used as grounding conductors. For example, the larger diameter

conductors 11a may be about 329.36 mm2 (650 kcmil) in size (/.e., having a cross-sectional area of about 329.36 mm2 (650,000 circular mils)), thus having a diameter of about 20.5 millimeters. The smaller diameters conductors 11b may be 2/0 AWG (American Wire Gauge) in size (/.e., having a cross-sectional area of 67.39 mm2 (133,000 circular mils)), thus having a diameter of about 9.3 millimeters. Preferably, the high-conductivity conductors 11 are copper, although other high-conductivity metals (e.g., aluminum, silver, or gold) or metal alloys may be employed as an alternative to copper.

[0017] The foregoing notwithstanding, those of ordinary skill in the art will appreciate that the size of the high-conductivity conductors will depend upon the desired current-carrying capacity of the power cable 10. Indeed, because the current-carrying capacity of the power cable 10 depends upon the cross-sectional area of the high-conductivity conductors, greater current-carrying capacity requirements typically require larger diameter high-conductivity conductors.

[0018] One or more conductors 11a and 11b are individually insulated. For example, each conductor is preferably insulated with a chemically cross-linked polyolefin (e.g., having a thickness of between about one millimeter and three millimeters). Alternatively, and by way of example, the conductors are insulated with silicone, a thermoset polymer, cross-linked polyethylene, halogen-free ethylene propylene rubber, and/or a low smoke, halogen-free cross-linked polyolefin.

[0019] The power cable 10 includes electromagnetic shielding. As depicted in Figure 1 and by way of example, a layer of metal/polymeric tape 13 (e.g., aluminum/polyester tape) surrounds the high-conductivity conductors 11. Preferably, the metal/polymeric tape has two sublayers: (/) a polymeric layer (e.g., a polyester layer) and (//) a metallic layer (e.g., a layer of aluminum or other highly conductive metal). In one embodiment, a braided shield layer 14 is positioned between a first layer of an aluminum/polyester tape 13 and a second layer of an aluminum/polyester tape 15, thereby forming electromagnetic shielding. Preferably, the metallic sublayer of each tape is positioned adjacent to, and more preferably in contact with, the braided shield layer 14. Preferably the braided shield layer 14 is formed from a braid of tinned copper. Alternatively, the shield layer 14 is not braided but may be formed from a serving of tinned copper (e.g., a plurality of tinned copper wires helically wrapped around the cable). That said, other materials such as copper, aluminum, or bronze may be used to form the shield layer 14. For example, in an alternative embodiment the electromagnetic shielding may include a braided copper shield layer positioned between two layers of copper/polyester tape.

[0020] In a particular embodiment, the wires used to form the braided shield layer 14 may be 30 AWG in size (e.g., having a diameter of about 0.26 millimeter). That said, other sized wires are within the scope of the present invention as claimed. The braided shielding layer 14 typically provides coverage (/.e., the extent to which the underlying material is concealed) of between about 60 percent and 95 percent and, in combination with the tape layers 13 and 15, provides effective electromagnetic shielding.

[0021] A layer of rubber/fabric tape 16 preferably surrounds the electromagnetic shielding (e.g., surrounding the second layer of aluminum/polyester tape 15). In an alternative embodiment, an armor layer (e.g., formed from braided bronze) surrounds the electromagnetic shielding.

[0022] The power cable 10 includes one or more polymeric sheaths enclosing the high-conductivity conductors. In one embodiment and as depicted in Figure 1, the power cable 10 includes a first polymeric sheath 17 and a second polymeric sheath 19, enclosing a reinforcing layer 18. Each polymeric sheath of this embodiment has a thickness of between about three millimeters and four millimeters. The polymeric sheaths 17 and 19 are preferably formed of material that is resistant to drilling fluids, such as the "mud" used in drilling operations. In a preferred embodiment, the polymeric sheaths 17 and 19 are formed from a low-smoke, zero-halogen (LSZH), ester-based polymeric material. By way of example, the polymeric sheaths 17 and 19 are formed from a cross-linked polyolefin or from nitrile rubber.

[0023] As noted, a reinforcing layer 18, formed of braided aramid fibers, is positioned between the first polymeric sheath 17 and the second polymeric sheath 19. The reinforcing layer 18 supports (e.g., provides mechanical strength to) the power cable 10 when it is installed (e.g., suspended in a drilling rig). In this regard, the reinforcing layer 18 has a breaking strength of at least about 44,482 N ( about 10,000 Ibf (pound-force)) (e.g., about 88,964 N (about 20,000 Ibf) or more). The power cable is for example attached to a drilling rig by applying a grip (e.g., a basket-weave grip) over the second polymeric sheath 19.

[0024] The braided aramid fibers provide open coverage (e.g., coverage of between about 40 percent and 60 percent,). The second polymeric sheath 19 is extruded over the aramid braid so that a portion of the second polymeric sheath 19 fills the gaps in the aramid braid, thereby integrating the second polymeric sheath 19 and the reinforcing layer 18.

[0025] The aramid braid is preferably formed from a plurality of flat aramid strands. For example, the aramid braid includes 48, 36, 32, or 24 flat aramid strands. By way of example, each flat aramid strand has a thickness of about 1 mm (about 0.04 inch) and a width of about 3.4 mm (about 0.135 inch). Depending upon the size of the power cable 10 and its desired strength, aramid strands of other sizes may be employed. To facilitate the formation of a flat strand, aramid fibers are preferably impregnated with a resin. The resin reduces the friction between the aramid strands and helps to ensure that the aramid strands are uniform in size and shape. Exemplary flat aramid strands (e.g., PFIILLYSTRAN™ 49) are available from Phillystran, Inc. (Montgomeryville, PA).

[0026] The aramid braid preferably employs a braid angle (/.e., the acute angle measured from the axis of the braid to a braiding strand) of between about 15 degrees and 45 degrees. More preferably, the braid angle is between about 20 degrees and 30 degrees, even more preferably between about 24 degrees and 27 degrees.

[0027] The design of the reinforcing layer 18 ensures that it provides sufficient strength to the power cable 10 and helps to prevent the rotation or twisting of the power cable 10 during use. In other words, the reinforcing layer 18 provides torque compensation to the power cable 10.

[0028] The power cable 10 preferably contains fire-resistant and non-hygroscopic fillers 12. Exemplary materials used as fillers include glass fibers and/or polypropylene.

[0029] The power cable 10 preferably has a weight of about 18.45 kg/m (12.4 lbs/ft (pounds per foot)). Moreover, in preferred embodiments the power cable 10 has a voltage rating of at least about 2,000 volts, a minimum bending diameter of about 1.83 m (six feet), a breaking strength of at least about 88,964 N (about 20,000 Ibf), and a maximum working load of at least about 1,361 kg (about 3,000 lbs).

[0030] The power cable 10 preferably complies with the IEEE 1580 standard, the UL 1309 standard, and the IEC 60092-350 standard. Moreover, the power cable 10 is DNV and ABS Type Approved and ETL listed as a marine shipboard cable in accordance with the foregoing standards.

[0031] In another aspect, the present invention embraces two or more power cables connected together. Although the ensuing description relates to a connected pair of power cables, it is within the scope of the present invention as claimed to have more than two power cables connected together (e.g., three or more connected power cables).

[0032] Figure 2 depicts a connected pair 25 of two top-drive power cables 30 and 40. In a preferred embodiment, cables 30 and 40 have identical design and/or sizes. In another preferred embodiment, cables 30 and 40 have different designs and/or sizes.

[0033] The power cables 30 and 40 are, in an embodiment, connected with a plurality of bandings 45 along the length of the power cables 30 and 40. For example, a banding 45 is positioned approximately every 1.5 meters along the length of the power cables 30 and 40. Examples of bandings 45 have a width of between about 10 and 15 millimeters. The bandings are for example constructed from stainless steel, although other materials are within the scope of the present invention as claimed.

[0034] In an embodiment, the connected pair 25 includes a core cable 50 (e.g., an independent wire rope core (IWRC)) running parallel to and positioned between the power cables 30 and 40. In a preferred embodiment, the core cable 50 is stainless steel and has a breaking strength of at least about 378,099 N (about 85,000 Ibf). In another preferred embodiment the core cable 50 is formed from galvanized steel, aramid fibers, nylon, rayon, polyester (e.g., Dacron® polyethylene terephthalate), and/or other synthetic materials. The core cable 50 is for example attached to the connected pair 25 using a plurality of saddles 46 positioned along the length of the core cable 50. Preferably, each saddle 46 includes two halves 46a and 46b that are placed around the core cable 50. Each saddle, for example, has a length of between about 50 millimeters and 200 millimeters. Preferably, adjacent saddles are separated by a space of between about one meter and three meters. In a preferred embodiment, a saddle extending along a substantial length of the core cable 50 is employed.

[0035] The saddles 46 are attached to the connected pair 25 with the bandings 45. Moreover, the core cable 50 is mechanically coupled (e.g., potted) to each end of connected pair 25. Accordingly, the core cable 50 provides additional mechanical support and torque resistance to the connected pair 25.

[0036] In the specification and/or figures, typical embodiments of the invention have been disclosed. The present invention is not limited to such exemplary embodiments. The use of the term "and/or" includes any and all combinations of one or more of the associated listed items. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description • GN201374209Y [0008]

Claims

A cable for providing power to a motor of a top drive on a drilling rig, comprising: one or more insulated conductors with high conductivity; electromagnetic shielding enclosing the conductors with high conductivity; a first polymeric sheath surrounding the electromagnetic shield; a reinforcing layer of braided aramid fibers surrounding the first polymeric sheath, characterized in that the reinforcing layer: (i) has holes in the aramid braid; (ii) provides a coverage of between 40 and 60 percent, the coverage being the extent to which the first polymeric jacket is concealed, and (iii) has a breaking strength of at least about 44,482 N (10,000 Ibf); and a second polymer sheath wherein the second polymer sheath is extruded over and surrounding the braided aramid fibers, with a portion of the second polymer sheath filling the holes in the aramid braid.

The cable according to claim 1, comprising an armor layer disposed between the electromagnetic shield and the first polymeric sheath.

A cable according to claim 1, comprising a rubber / fabric band layer disposed between the electromagnetic shield and the first polymeric sheath.

A cable according to claim 1, wherein the high conductivity conductors comprise copper, gold, silver and / or aluminum.

The cable of claim 1, wherein the electromagnetic shield comprises: a first band layer; another band layer; and a braided shield layer disposed between the first and second band layers.

The cable of claim 5, wherein the first and second band layers comprise aluminum / polyester bands; and the braided shielding layer comprises tinned copper.

The cable of claim 5, wherein the first and second band layers comprise copper / polyester bands; and the braided shielding layer comprises copper.

A cable according to claim 1, wherein each of the first and second polymeric envelopes comprises a smokeless, halogen-free (LSZH) polymeric material.

A cable according to claim 1, wherein each of the first and second polymeric sheaths comprises a cross-linked polyolefin and / or nitrile rubber.

The cable of claim 1, wherein said reinforcing layer comprises a plurality of flat macaws.

The cable of claim 1, wherein the reinforcing layer comprises flat, resin impregnated aramid wires.

A cable according to any one of claims 1-11, wherein the reinforcing layer uses a braid angle of between about 20 degrees to 30 degrees.

A cable according to any one of claims 1-11, wherein the reinforcing layer uses a braid angle of between about 24 degrees to 27 degrees. A cable according to any one of claims 1-11, wherein the reinforcing layer provides a coverage of about 50 percent.

A cable according to any one of claims 1-11, wherein the reinforcing layer has a breaking strength of at least about 88,964 N (20,000 Ibf).

A connected pair of cables for providing power to a motor of a top drive in a drilling rig, comprising: two cables, each according to any one of claims 1-11, wherein the cables are arranged substantially parallel to each other ; a core cable disposed between and substantially parallel to the power cables; and a plurality of strapping connecting the power cables and the core cable.

A method of supplying a peak drive on a drilling rig with a stream, the method comprising the steps of: providing a cable according to any one of claims 1-11; connecting the cables to the top drive; and connecting the cable to a power source.