Patent Publication Number: US-9412502-B2

Title: Method of making a down-hole cable having a fluoropolymer filler layer

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. application Ser. No. 13/071,941 filed Mar. 25, 2011, now abandoned, which claims the benefit of U.S. Provisional Application Ser. No. 61/318,482 filed Mar. 29, 2010, entitled, “Down-hole Cable Having a Fluoropolymer Filler Layer”, the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure is generally related to cables and more particularly is related to a down-hole cable having a fluoropolymer filler layer. 
     BACKGROUND OF THE DISCLOSURE 
     Down-hole cables are found in use in many industries including those that conduct deep drilling, such as within the oil drilling industry. These cables may be used to transmit information and data from a drilling region having the drilling equipment to a control center located remote to the drilling region. Many oil-drilling regions are located deep within the Earth&#39;s crust, such as those seen with onshore and offshore drilling. The drilling region may be 5,000 feet or more from a control center located on the Earth&#39;s surface or a control center located on water at sea level. A cable of 5,000 feet or more may have a high weight that, when located vertically down a drilling hole distorts the structure of the cable itself. This may result in a failure of the cable or a deformity of the cable that renders it more inefficient than a non-deformed cable. 
     Current cables include a filler constructed from solid polypropylene that surrounds a conductor and enclosed with an armored sheath, such as a superalloy like Incoloy or a stainless steel. The purpose of the polypropylene filler is to provide a compressive force between the conductor core and the armored sheath, thereby producing a force to retain the conductor core within the cable. The force produced by the solid polypropylene filler may counteract a pullout force, which is the force necessary to remove the conductor core from the cable. The polypropylene fillers that are used are rated at 150° C. and therefore are frequently unable to retain their integrity when the cable is being produced using a heated method. This is due to the inherent crystallinity of the extruded polypropylene filler and the after effect additional heat cycles from the encapsulation extrusion of the armored sheath. These additional heat cycles cause a phase shift in the polypropylene, which in effect, reduce the diameter of the material, which lessens the pullout force necessary to compromise the cable. The encapsulation extrusion process has temperatures that are greater than the annealing temperature of the polypropylene facilitating the phase shift. This results in a cable that may easily be damaged from its own weight creating a pullout force on the conductor core resulting in the conductor core moving within the cable. 
     Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies. 
     SUMMARY OF THE DISCLOSURE 
     Embodiments of the present disclosure provide an apparatus and method for a down-hole cable. Briefly described, in architecture, one embodiment of the system, among others, can be implemented as follows. The down-hole cable includes an insulated conductor portion and a filler layer abutting and encapsulating the insulated conductor portion, wherein the filler layer is substantially formed with a foamable fluoropolymer. At least one additive is mixed with the foamable fluoropolymer filler layer. An armor shell is applied to the exterior of the foamable fluoropolymer filler layer with the at least one additive. A bond is formed between the foamable fluoropolymer filler layer with the at least one additive and an internal surface of the armor shell. 
     The present disclosure can also be viewed as providing methods for making a down-hole cable. In this regard, one embodiment of such a method, among others, can be broadly summarized by the following steps: extruding a pre-foamed foamable filler layer about an insulated conductor, wherein the pre-foamed foamable filler layer further comprises a fluoropolymer and an additive; applying an armor shell about the insulated conductor and the pre-foamed foamable filler layer with additive; pressure-testing the armor shell by pressurizing at least one cavity formed between the pre-foamed foamable filler layer with additive and the armor shell; and after pressure-testing, foaming the foamable filler layer with additive into a foamed state, wherein at least a portion of the foamed filler layer with additive bonds to an interior surface of the armor shell, wherein the foamed filler layer with additive withstands a pullout force at temperatures of temperatures above 200° C. 
     Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a cross-sectional illustration of a down-hole cable, in accordance with a first exemplary embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional illustration of a down-hole cable, in accordance with a second exemplary embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional illustration of a cable in an in-use position, in accordance with the first exemplary embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional illustration of a cable, in accordance with a second exemplary embodiment of the present disclosure. 
         FIG. 5  is a flowchart illustrating a method of making the abovementioned down-hole cable in accordance with the first exemplary embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a cross-sectional illustration of a down-hole cable  10 , in accordance with a first exemplary embodiment of the present disclosure. The down-hole cable  10 , hereinafter, “cable  10 ” may also be referred to as a tube-encapsulated conductor, a permanent down-hole cable, or simply as a cable. The cable  10  includes an insulated conductor portion  20 . A filler layer  30  abuts and encapsulates the insulated conductor portion  20 , wherein the filler layer  30  is substantially formed with a foamable fluoropolymer. At least one additive mixed  32  with the foamable fluoropolymer filler layer  30 . An armor shell  40  applied to the exterior of the foamable fluoropolymer filler layer  30  with the at least one additive  32 , wherein a bond is formed between the foamable fluoropolymer filler layer  30  with the at least one additive  32  and an internal surface  42  of the armor shell  40 . The cable  10  may be any wire, transmission line or similar structure that may be used in deep drilling operations, such as with onshore or offshore oil drilling. The insulated conductor portion  20  may include any material, which is capable of facilitating movement of electric charges, light or any other communication medium. The insulated conductor portion  20  may include at least one conductor material  22 , such as copper, aluminum, alloys, fiber electric hybrid materials, fiber optical material or any other material known within the industry. The insulation surrounding at least one conductor material  22  may include any type of insulation. The insulated conductor portion  20  may be capable of facilitating movement of energy capable of powering a device or facilitating a communication or control signal between devices. The insulated conductor portion  20  may be located at substantially the center of the cable  10 , but may also be located off-center or in another position as well. As is discussed with respect to  FIG. 2 , more than one insulated conductor portion  20  may be included. 
     Surrounding the insulated conductor portion  20  and fully encapsulating it is a foamed fluoropolymer filler layer  30 . The filler layer  30  is formed substantially from a foamed fluoropolymer. This may include any foamed fluorocarbon based polymer with multiple strong carbon-fluorine bonds, such as materials like FEP (fluorinated ethylene-propylene), PFA (perfluoroalkoxy polymer resin), MFA (modified fluoroalkoxy), ETFE (polyethylenetetrafluoroethylene), ECTFE (polyethylenechlorotrifluoroethylene), PVDF (polyvinylidene fluoride), TPX (polymethylpentene), PEEK (polyether ether keytone), copolymers, synthetic polymers or any other fluoropolymer. Common trade names for some of these materials may include Tefzel®, Halar®, Nylon and Kynar®. The foamed fluoropolymer filler layer  30  has a foamed structure that is unlike the solid structure of polypropylene materials. 
     At least one additive  32  may be added to the filler layer  30 . The additive  32  may include a powdered polytetrafluoroethylene (PTFE), commonly known under the brand name TEFLON®. The additive  32  may be in the form of a powder, such as a PTSD powder known under the brand name ZONYL® MP1300. The additive  32  is mixed with the fluoropolymer filler layer  30 , preferably integrally, so the combination of the filler layer  30  and additive  32  are fully combined. The additive  32  may assist with preventing the filler layer  30  from sticking to the insulated conductor portion  20 , which may prevent proper foaming of the filler layer  30 . For example, the additive  32  may impart a low surface energy into the filler layer  30  to enhance nonstick characteristics of the filler layer  30 . 
     The foamed fluoropolymer filler layer  30  and additive  32  may be manufactured on an extrusion line with a nitrogen port in the barrel of the extruder. The nitrogen may be injected into the barrel at the extrusion process to create the foamed cell structure. This cell structure may be present in the entire filler layer  30  and be capable of providing a compressive force on the insulated conductor portion  20 . The foamed fluoropolymer layer  30  with additive  32  may also be formed through any other foaming process, wherein a foam having a substantially high viscous is directed proximate to the insulated conductor portion  20  and processed to have a substantially low viscosity. Foamed fluoropolymer may also have a high annealing temperature, whereby it can retain its integrity throughout an annealing process. This may include annealing processes that exceed 150° C., 175° C., 200° C., 250° C., 300° C., 350° C. or any other known annealing temperature. Preferably, the foamed fluoropolymer filler layer  30  will be able to exceed temperatures up to 250° C. The foamed cellular structure of the fluoropolymer may provide a stable matrix of material, which increases the compression on the insulated conductor portion  20  thereby increasing the effective pullout force on the cable. 
     The armor shell  40  is a sheath or exterior coating or layer that is applied to an exterior surface of the foamed fluoropolymer filler layer  30  and protects the inner components of the cable  10 . The armor shell  40  may be substantially hardened, metal or metal alloy, as is known in the art, and may be substantially concentric to the insulated conductor portion  20  and constructed from a strong material, such as a stainless steel or Incoloy®. The armor shell  40  may protect the cable  10  from foreign objects penetrating the cable  10 , such as debris from a drilling process. The armor shell  40  may also support the cable  10  to an anchoring position or between two anchoring positions. For example, the cable  10  may be anchored on one end with the armor shell  40  whereby the other end of the cable  10  is located in a vertical direction within the Earth, such as when it is placed down a drilling hole. The armor shell  40  may also include any woven, solid, particulate-based and layered protecting materials. 
     The foamed fluoropolymer filler layer  30  and additive  32  may be the only material between the insulated conductor portion  20  and the armor shell  40 . Accordingly, the foamed fluoropolymer includes a cellular structure that provides a compressive force on an exterior surface of the insulated conductor portion  20  and the interior surface of the armor shell  40 . This compressive force resists the pullout force within the cable  10 , such as that created by gravity acting on a down-hole cable  10 . The cable  10  may have any size diameter or length and therefore the insulated conductor portion  20 , the foamed fluoropolymer filler layer  30  and the armor shell  40  may have any size or configuration. This may include a foamed fluoropolymer filler layer  30  that is substantially thin in comparison to the armor shell  40  or the insulated conductor portion  20 , or a foamed fluoropolymer filler layer  30  that forms the majority of the material within the cable  10 . 
     Further, a bond may be formed between the filler layer  30  having the additive  32  and the internal surface  42  of the armor shell  40 . The bond may include a chemical bond that is generated after complete foaming of the filler layer  30 . The bond may retain the filler layer  30  to the armor shell  40 , thereby preventing separation of the filler layer  30  from the armor shell  40  when a pullout force is applied to the insulated conductor portion  20 . 
     In operation, the cable  10  may be placed vertically, wherein one end of the cable  10  is substantially above the other end of the cable  10 . This may include a cable  10  with any length, such as 100 feet, 300 feet, 500 feet or greater, or any other length. For example, the cable  10  may be suspended within a hole drilled within the Earth&#39;s crust, wherein one end of the cable  10  is located above the Earth&#39;s crust and the other end is located 500 feet or more below the Earth&#39;s crust. The cable  10  may be held in this position for any period of time. The cable  10  may be resistant to the pullout force created by gravity acting on the components of the cable  10 . In other words, the foamed fluoropolymer filler layer  30  may place a compressive force on the insulated conductor portion  20 , which is stronger than any pullout force created by gravity. The cable  10  may also include anchors at any portion of the cable  10  to retain the cable  10  in one or more positions. The cable  10  may be suitable for any vertical use, and may be especially preferable for vertical use spanning a distance of 500 feet or more. As one having ordinary skill in the art would recognize, many variations, configuration and designs may be included with the cable  10 , or any component thereof, all of which are considered within the scope of the disclosure. 
       FIG. 2  is a cross-sectional illustration of a cable  10 , in accordance with the first exemplary embodiment of the present disclosure. As is shown, the cable  10  includes an insulated conductor portion  20  located near a central axis of the cable  10  and the abutting filler layer  30  that is formed from foamed fluoropolymer and the additive  32  encapsulates the insulated conductor portion  20 . The filler layer  30  and additive  32  includes a foamed cell structure, which creates a stable matrix, thereby increasing the effective pullout force throughout the cable  10 . The foamed cell structure may be included in all or a portion of the filler layer  30  and additive  32  throughout a cable  10 , and is illustrated throughout the filler layer  30  in  FIG. 2 . For example, the foamed cell structure may be included in only specific sections or segments of the cable  10 , or only within a certain radial boundary within the cable  10 , such as with a striated foamed design. The foamed cell structure may be produced by a variety of methods, including injecting a quantity of gas, such as nitrogen, into the filler layer  30  and additive  32  as it is extruded in a manufacturing process. Specifically, the extruder used to create the filler layer  30  may include a gas port within the barrel, whereby the gas is injected in the filler layer  30  and additive  32  to create the foamed cell structure. The armor shell  40  is applied to the exterior of the foamed fluoropolymer filler layer  30  and additive  32  with the foamed cell structure and traverses around the circumference of the cable  10 . The bond is then created between the foamed fluoropolymer filler layer  30  with the additive  32  and the interior surface  42  of the armor shell  40 . 
       FIG. 3  is a cross-sectional illustration of a cable  10  in an in-use position, in accordance with the first exemplary embodiment of the present disclosure. The cable  10  is a down-hole cable for use in substantially vertical positions. For example, the in-use position of the cable  10  may include a substantially vertical orientation where the cable is at least partially placed within a drilled or bored hole within the Earth or a body of water, such as an ocean.  FIG. 3  illustrates the cable  10  positioned partially within a hole  50  within the Earth  52 . As can be seen, the armor shell  40  of the cable  10  may be positioned proximate to the Earth  52 , whereby it may prevent articles within the Earth  52  from penetrating the cable  10 . For example, the armor shell  40  may prevent rocks or other objects from damaging the cable  10  while it is placed within the hole  50 . Additionally, the armor shell  40  may be used to secure the cable  10  in a specific position via an attachment to one or more anchoring structures  60 . In  FIG. 3 , the anchoring structures  60  are illustrated at an upper end of the cable  10 , although they may be placed along any part of the cable  10 , including the bottom or a mid-section. 
       FIG. 4  is a cross-sectional illustration of a cable  110 , in accordance with a second exemplary embodiment of the present disclosure. The cable  110  is similar to that of the cable  10  of the first exemplary embodiment, and includes at least a first conductor material  122  and a second conductor material  124  within the insulated conductor portion  120 . A filler layer  130  abuts and encapsulates the first and second conductor materials  122 ,  124  of the insulated conductor portion  120 , wherein the filler layer  130  is substantially formed with a foamable fluoropolymer. At least one additive mixed  132  with the foamable fluoropolymer filler layer  130 . An armor shell  140  applied to the exterior of the foamable fluoropolymer filler layer  130  with the at least one additive  132 , wherein a bond is formed between the foamable fluoropolymer filler layer  130  with the at least one additive  132  and an internal surface  142  of the armor shell  140 . 
     The cable  110  may include any of the features or designs disclosed with respect to the first exemplary embodiment. In addition, the cable  110  includes a plurality of conductor materials, i.e., first and second conductor materials  122 ,  124 , which may include two or more solid or other conductor materials. Additionally, the first and second conductor materials  122 ,  124  may be different conductors, depending on the design and use of the cable  110 . The first and second conductor materials  122 ,  124  may facilitate the transmission of electrical energy through the cable  110 , or may facilitate communication of control signals through the cable  110 . The foamed fluoropolymer filler layer  130  may apply a compressive force on any one or all of the first and second conductor materials  122 ,  124  of the insulated conductor portion  120 , thereby increasing the pullout force resistance within the cable  110 . The plurality of insulated conductor portions  120  may also facilitate transmission of varying signals, such as communication signals on one of the plurality of insulated conductor portions  120  and energy transmission on another of the plurality of insulated conductor portions  120 . As one having ordinary skill in the art would recognize, many variations, configuration and designs may be included with the cable  110 , or any component thereof, all of which are considered within the scope of the disclosure. 
       FIG. 5  is a flowchart  200  illustrating a method of making the abovementioned down-hole cable  10  in accordance with the first exemplary embodiment of the disclosure. It should be noted that any process descriptions or blocks in flow charts should be understood as representing modules, segments, portions of code, or steps that include one or more instructions for implementing specific logical functions in the process, and alternate implementations are included within the scope of the present disclosure in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present disclosure. 
     As is shown by block  202 , a pre-foamed foamable filler layer is extruded about an insulated conductor, wherein the pre-foamed foamable filler layer further comprises a fluoropolymer and an additive. An armor shell is applied about the insulated conductor and the pre-foamed foamable filler layer with additive (block  204 ). The armor shell is pressure tested by pressurizing at least one cavity formed between the pre-foamed foamable filler layer with additive and the armor shell (block  206 ). After pressure-testing, the foamable filler layer with additive is expanded into a foamed state, wherein at least a portion of the expanded foamable filler layer with additive bonds to an interior surface of the armor shell, wherein the expanded formable filler layer with additive withstands a pullout force at temperatures of temperatures above 200° C. (block  208 ). 
     A variety of additional steps may also be included in the method. For example, the step of foaming the filler layer  30  and additive  32 , such as a powdered polytetrafluoroethylene (PTFE), about the insulated conductor portion  20  may include creating a foamed cell structure by gas-injection, such as a nitrogen-injection method during an extrusion process. In addition, foaming the filler layer  30  with additive  32  about the insulated conductor portion  20  may include creating a radial compressive force acting on the insulated conductor portion  20  and the armored shell  40 . The radial compressive force withstands a pullout force between the insulated conductor portion  20  and the armored shell  40 . The bond between the expanded foamable filler layer  30  and the interior surface  42  of the armor shell  40  may be a chemical bond. The radial compressive force and/or the bond, together or independently, may allow the down-hole cable  10  to withstand pullout forces between the insulated conductor  20  and the armor shell  40  in a variety of temperatures, including temperatures greater than 150° C. and preferably 250° C. 
     As may be understood, the down-hole cable  10  may be used for a variety of purposes, such as within oil well drilling operations. Accordingly, the any number of signals may be transmitted through any number of conductors within the insulated conductor portion  20 . These signals may be any type of signals, such as power signals and/or communication signals used to operate a device or combination of devices. This may include signals for monitoring a device&#39;s activity or an environmental activity proximate to the device. As the down-hole cable  10  may be positioned substantially vertically, the armor shell  40  may be connected to at least one anchoring structure. The anchoring structure may support the weight of the down-hole cable  10  via the armor shell  40 . 
     It should be emphasized that the above-described embodiments of the present disclosure, particularly, any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present disclosure and protected by the following claim.