MXPA96001353A - Combination of perforation recording cable for electric conductor / optimal fibers - Google Patents

Abstract

The present invention relates to a perforation recording cable, comprising: first conductor elements including a steel cable surrounded by copper wires, the copper wires are covered by electrically insulating material, at least a second coding element including At least one optical fiber circumscribed in a metal tube, copper wires surrounding the tube, the copper wires are covered by the electrically insulating material, wherein the first conducting elements and the second conducting element as a minimum, are arranged in a central beam , the second conductive element as minimum is placed in the central beam in order to coil spirally around a central axis of beam, the second conductive element as minimum has an electrical impedance substantially equal to that of the first coding elements, and reinforcing wires coiled helically around the h

Description

COMBINATION OF DRILL RECORDING CABLE FOR ELECTRICAL CONDUCTOR / OPTICAL FIBERS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of armed cables used in the electrical recording of oil and gas well drilling. More specifically, the present invention relates to a design for a combination of optical and electrical fiber cables used to lower instruments for drilling logs into holes drilled in the ground. ? Description of the Related Art Perforation record is known in the art to provide measurements of properties of land formations penetrated by drilling. The record of perforations includes inserting measuring instruments in the perforation, the instruments are connected to one end of an armed electric cable. Armed electric cables known in the art typically comprise at least one isolated electrical conductor that is used both to supply electrical power to the instruments and to transmit signals generated by the instruments to other equipment located on the surface of the earth to decode and interpret the signs The cables known in the art further comprise these coiled wire armatures helically around the electrical conductor to provide tensile strength and abrasion resistance to the cable. The signals generated by the instruments for transmission to the surface of the earth are typically electrical signals. The signals can be in the form of analog voltages or digital points. A disadvantage of using electrical signals in the perforation register is that the mechanical requirements imposed on the perforation recording cable, for example relatively high bending flexibility and low weight per unit length, require that the cable and electrical conductor be formed to Starting from wire that usually have small diameter. A typical perforation recording cable, for example, comprises an electrical conductor consisting of seven copper wires with a diameter of .325 mm (0.0128") covered by a plastic insulator with an outer diameter of 2.44 mm (0.096"). The electrical conductor is typically characterized by an approximate resistance of 9 ohms per 3004.8 meters (1000 feet) of conductor and has a capacitance of several picofarads per .3048 meters (foot) of conductor. Other cables known in the art can include a plurality of conductors arranged in a central bundle or bundle, each conductor having approximately the same construction and electrical characteristics as the conductor employed in the single conductor cable.

Because the electrical properties of conductors in typical drilling logging cables, drilling logging cables known in the art typically can not effectively transmit electrical signals at frequencies above 100 kilohertz (KHz). More recent types of drilling logging instruments can generate data at speeds that make the use of electrical signal transmission difficult and expensive. It is known in the art to provide optical fibers in drilling log cables to allow use of optical telemetry, which are capable of much higher frequencies and data transmission speeds than the transmission of electrical signals. For example, U.S. Pat. No. 4,696,542 issued to Thompson, discloses a drilling log cable having optical fibers arranged substantially in the center inside copper-coated steel conductors, helically wound, the conductors themselves covered by two layers of steel-reinforced cored wire. against helically. A disadvantage for the perforation recording cable described in Thompson '542 patent is that the optical fibers are circumscribed in a plastic tube. Drill log cables may be exposed to hydrostatic pressures and drilling temperatures that are sufficiently high to avoid the use of the plastic pipe as described in the Thompson '542 patent.

Other optical fiber cables known in the art include circumscribing the optical fibers in a steel tube. For example, "Electro-Optical Mechanical Umbilicals", Vector Cable, Sugar Land, TX (date of unknown publication) describes several so-called "trailer and umbilical" cables that include steel tubes that circumscribe the Optical Fibers One disadvantage of the combination optical / electrical fiber cables described in the Vector Cable reference is that the cable designs described therein have very large diameter electric conductors that are intended to be used only for transmission of electrical power; Optical fibers perform substantially all signal communication functions of the cable For reasons known to those skilled in the art, the use of large diameter power conductors as described in the Vector Cable reference results in a cable having an external diameter so large that it avoids the use of certain equipment for control of pressure of flu The cables described in the Vector Cable reference also have electrical signal transmission characteristics substantially different from the perforation recor cables known in the art due to the large size of the power conductors. It is also convenient to provide a combination of optical / electrical fiber cables, which has electrical conductors capable of maintaining the electrical signal transmission of the electric perforation recor cables known in the art, in such a way that the existing drilling instruments they use Electrical telemetry does not require to be re-designed. A combination of electrical / optical fiber drilling recor cable having the optical fibers circumscribed in a steel tube is described, for example, in US Pat. No. 4,522,864 issued to Thompson et al. The cable described in the patent 64 provides a circumscribed optical fiber in a steel tube disposed in the center of a perforation recor cable. A disadvantage for the cable described in the patent 64 is that conductor members positioned externally to the central tube containing the optical fiber are constructed of copper-clad steel cable in order to provide inelastic tensile strength and resistance for the cable. Copper-clad steel wire typically has different electrical impedance than copper wire of similar electrical conductance. The conductor members in the cable of the Patent 64 may be difficult to employ for the electrical signal transmission schemes known in the art. In another embodiment of drilling log cable in the '464 patent, one or more of the copper coated steel conductors may be replaced by optical fibers. A disadvantage of directly replacing optical fibers with conductive elements as described in the '64 patent is that some of the electrical power and the signal transmission capacity of the perforation recor cable will be lost since replaced conductors are replaced by a non-conductive element. , that is to say the optical fiber. A further disadvantage to the cable described in the Thompson et al. '464 patent is that the steel tube used to circumscribe the optical fiber is connected to inelastic tension and eventual failure as a result of repeated applications and relaxations of axial tension in the cable. The tube, placed at the center of the cable as described in patent% 464, is subject to greater axial elongation under tension than any of the reinforced cables since the reinforced cables are wound helically around the cable axis and therefore allow elongation of the cable when unwin the helical distribution of the armed wires under axial tension. Another type of drilling log cables, electric / fiber optic is described in "Manufacture and testing of cable for logging in the bottom of drilling, based on armed optical fibers" (Manufacturing and testing of armored fiber optic downhole logging cable) by Randall et al., Wire and collaborators is that the optical fibers are subject to fluid pressure in the perforation since they are not sealed under pressure. Another disadvantage to the cable in the article by Randall et al. Is that some of the electrical conductors are replaced by optical fibers. The electrical transmission characteristics of a cable constructed in accordance with the design of Randall et al. May not have the convenient electrical transmission properties for use with certain instruments for drilling registration. Another combination of electrical / fiber optic drilling log cables is described in International Patent Application No. WO 94/28450 published under the Patent Cooperation Treaty. The cable described in the application No. WO 94/28450 includes a fiber optic circumscribed in a metal tube. The metal tube can be surrounded by braided copper wires that are used to conduct electrical signals and electrical energy. One embodiment of the cable described in application No. WO 94/28450 includes the application of the copper braids directly to the metal tube. One mishap of the cable described in the application No. WO 94/28450 is that the tube is placed at the center of the cable. Placing the tube in the center of the cable as previously explained, can subject the tube and optical fiber to excessive axial tension under certain conditions. In addition, the cable described in the application No. WO 94/28450 does not disclose associated configuration of the metal tube and copper braid to provide the electrical impedance characteristics similar to the insulated copper cables of the known electric perforation recording cables in The technique. In fact, the preferred embodiment of the cable in application No. WO 94/28450 provides a layer of insulating material between the metal tube and the copper braids. As understood by those of skill in the art, drilling logging cables typically include electrical conductors and external armature wires that are respectively positioned to maintain a substantially round cross-sectional shape of the cable even after repeated applications and stress relaxations. axially substantial to the cable, while also subjecting the cable to significant buckling stresses. As understood by those skilled in the art, the applications and relaxations of axial tension and bending stresses occur as a result of lowering the instruments in the perforation and later removing them from the perforation when winding and uncurling the cable through various linings that They direct the cable to the drilling from winch equipment that is provided for winding and un-winding the cable. Drill log cables known in the art that only have electrical conductors provide maintenance of the round cross section of the cable because all conductors have similar tensile and flexural properties. Direct substitution of fiber optic conductors to provide a perforation recording cable having optical fibers will result in the cable having symmetrical bending and tensile properties, and possibly producing resistance to deformation of the circular cross-section of the cable. Accordingly, an object of the present invention is to provide a perforation recording cable having at least one optical fiber, the cable having a mechanical configuration and mechanical properties similar to those of the electric perforation recording cables known in the art. the specialty. A further object of the present invention is to provide a perforation recording cable having at least one optical fiber in an assembly having electrical power and signal transmission and electrical power capabilities similar to the known perforation recording cables in The technique. COMPENDIUM OF THE INVENTION The present invention is a perforation recording cable that includes first elements, each of the first elements consists of a steel cable surrounded by copper wires and covered in an electrically insulating material, and at least a second element that includes at least one optical fiber circumscribed in a metallic tube, copper wires encircle the tube and covered by electrically insulating material. The first elements and the second element as a minimum are arranged in a central beam. The second element is placed in the bundle in order to spirally wound around a central axis of the bundle. The bundle is surrounded by armature wires helically wound externally to the bundle. In a specific embodiment of the invention, the steel cable can be covered with metallic copper. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a cross-section of the drilling log cable according to the present invention. Figure 2 shows a detailed cross section of an electrical / fiber optic conductor element of the cable according to the present invention. Figure 3 shows a detailed cross section of an electrical conductor element of the cable of the present invention. DESCRIPTION OF THE PREFERRED MODALITY A cross section of a perforation recording cable 10 according to the present invention is illustrated in Figure 1. The cable 10 includes 7 insulated conductor elements with plastic as will be further explained. The seven elements are typically placed in a central beam 15 having a substantially regular hexagonal pattern, wherein six of the elements encircle the seventh element, an arrangement of elements familiar to those skilled in the art and intended to provide a significant amount. of deformation resistance of the substantially circular cross section in cable 10. Five of the seven elements, referred to as first elements illustrated generally at 16, may be insulated electrical conductive elements that include a copper-coated steel cable that may have approximately a diameter of .686 mm (0.027 mm) surrounded by nine copper wires each of which can be approximately .325 mm (0.0128 mm) in diameter. The first elements 16 may include an outer insulating lining which may be constituted by heat and moisture resistant plastic such as polypropylene copolymer or ethylene-tetrafluoroethylene ("ETFE") sold under the trademark "TEFZEL" which is a trademark of E.I. du Pont de Nemours &; Co. The other two of the seven elements, referred to as second elements and generally illustrated at 18, each may include, among other things, an optical fiber disposed within a stainless steel tube as will be further explained. The second elements 18 are intended to provide optical fibers to the cable 10 and have electrical and mechanical properties substantially the same as the first five elements 16. The cable 10 of the present invention includes two symmetrically placed of the second elements 18, however it is contemplated that the cable 10 of the present invention will perform as intended with the second elements 18 placed in any or all of the six locations externally located in the regular hexagonal pattern formed by the seven elements. The hollow spaces within the hexagonal structure of the seven elements 16, 18 can be filled with a filling material, illustrated at 17, which can be a plastic such as neoprene or ETFE. The filling 17 maintains the relative position of the seven elements 16, 18 within the cable 10. The elements 16, 18, and the filling 17 are covered with spirally wound galvanized steel reinforcement wires, which are formed in an inner reinforcement lining illustrated at 14. The inner frame 14 itself is externally covered with helically wound galvanized steel reinforcement wires that are formed in an outer frame liner, as illustrated at 12. The construction of the inner frame 14 and the outer frame 12 , may be of a type known to those skilled in the art, and the armor construction is designed to provide significant tensile strength and durability to the cable 10. As is known in the art, in a particular cable 10 which is intended to be used in a chemically hostile environment such as a borehole that has significant amounts of hydrogen sulfide, the wires of reinforcement 12, 14 can alternatively be constituted by a choice of cobalt-copper as here identified by the code MP-35N. One of the second elements 18 is illustrated in more detail in Figure 2. The second element 18 may constitute an optical fiber 22 circumscribed in a metal tube 24, which in the present embodiment is preferably made of stainless steel in order to provide resistance to corrosion. The tube 24 can have an external diameter .838 mm (0.033") and an internal diameter of .584 mm (0.023"). The tube 24 provides protection against abrasion and bending to the optical fiber 22 and excludes fluid in the perforation (not shown) in which the cable (10 in Figure 1) extends when in use. The tube 24 can be coated with copper to reduce its electrical resistance. The tube 24 can be surrounded by twelve copper wire wires generally illustrated at 26. Each of the wires of the cable 26 has a diameter of .254 mm (0.01"). The combination of the tube 24 and wires 26 provides a conductor that it has an electrical resistance of less than 10 ohms per 304.8 meters (1000 feet) in length, tube 24 and copper wires 26 are also covered with plastic insulation 20 which may be composed of a heat-resistant plastic such as ETFE or The outer diameter of the insulation 20 in the second element 18 is substantially the same as the external diameter of the insulation in the first element 16, such that the hexagonal pattern of the seven elements as illustrated in cross section of Figure 1 can be substantially symmetrical regardless of the relative position of the second element 18 within the hexagonal pattern of the beam 15. It will be understood that the second element 18 may be placed in any or all of the six external positions of the hexagonal structure as illustrated in Figure 1. The second element 18 is preferably placed at a location external to the hexagonal structure of the beam 15 because the elements 1618, in the outer locations, are wound helically around the element of a central portion. As understood by those skilled in the art, for reasons such as lateral reduction in pitch diameter with axial tension, the unwinding of helical wiring and the greater total length of the external elements wound helically with respect to the length of the central element 18, the externally positioned elements 16, 18 are subjected to reduced axial tension with respect to the axial elongation of the cable (illustrated in Figure 1 as 10) reducing the possibility of failure induced by axial tension of the tube 24 and the fiber 22. In the present embodiment of the invention, second elements 18 are placed in two external sites opposite each other in the hexagonal pattern, as can be seen by reference again to Figure 1.

Figure 3 shows a cross section of the first element 16 in more detail. The first element 16 may consist of a steel cable 28 which may be coated or covered with metallic copper to have an external diameter of approximately .686 mm (0.027") thereby reducing the electrical resistance of the wire 28. The wire covered with copper 28 may additionally be encircled by nine copper wires, generally illustrated at 30 and having an external diameter of .325 mm (0.0128"). The combination of wire 28 and copper wires 30 has an electrical resistance of less than 7 ohms per 304.8 meters (1000 feet) in length. The wires 30 may be covered with an electrical insulating material such as polypropylene or ETFE. With reference again to Figure 2, the second elements 18 are designed in such a way that the combination of the tube 24 and the wires 16 have an external diameter that allow the insulating material 20 to provide the second element 18 with substantially the same electrical capacitance per unit length than the first element 16. Therefore, the assembled cable (illustrated in Figure 1 as 10) will have substantially the same signal transmission and electrical power properties as a perforation recording cable made according to the prior art . While the present invention is directed to a perforation recording cable having a total of seven of the first elements 16 and second elements 18 in the central beam (illustrated as 15 in Figure 1) it is contemplated that the cables having other substantially symmetrical arrangements of first elements 16 and second elements 18 in the central beam 15, where elements 16, 18 are helically wound around a central axis of beam 15, will also have the electrical and mechanical characteristics of a cable that only has wires of copper in the beam but that will include at least one optical fiber placed inside the cable to minimize the axial tension applied to the fiber. What is claimed:

Claims (12)

1. CLAIMS 1.- Drill log cable, comprising: first conductive elements that include a steel cable surrounded by copper wires, the copper wires are covered by electrically insulating material; at least a second conductive element that includes at least one optical fiber circumscribed in a metal tube, copper wires surrounding the tube, the copper wires are covered by the electrically insulating material, wherein the first conductive elements and the second conductive element at least, they are disposed in a central beam, the second conductive element at least is placed in the central beam in order to coil spirally around a central axis of the beam, the second conducting element has at least an electrical impedance substantially the same as that of the first conductive elements; and armor wires wound helically around the bundle.
2. 2. The cable according to claim 1, wherein the insulating material comprises ETFE.
3. 3. The cable according to claim 1, wherein the insulating material comprises polypropylene.
4. 4. The cable according to claim 1, wherein the metal tube comprises stainless steel.
5. 5. The cable according to claim 1, wherein the steel cable is covered with metallic copper.
6. 6. - The cable according to claim 1, wherein the beam comprises a total number of seven conductive elements consisting of the first conductive elements and at least one of the second conductive elements.
7. 7. The cable according to claim 6, wherein the beam comprises two of the second conducting elements and five of the first conducting elements, the beam is arranged in a substantially regular hexagonal pattern, such that two of the second elements are opposite each other and helically wound around one centrally positioned of the first conductive elements.
8. 8. The beam according to claim 7, further comprising a filling material disposed within hollow spaces within the substantially regular hexagonal pattern.
9. 9. The beam according to claim 8, wherein the filling material comprises polypropylene.
10. 10. The cable according to claim 1, wherein the armor wires comprise galvanized steel.
11. 11. The cable according to claim 1, wherein the reinforcing wires comprise two contiguous coaxial layers of helically wound wires.
12. 12. The cable according to claim 1 or 11, wherein the reinforcing wires comprise a cobalt-nickel alloy.