Abstract:
An example device in accordance with an aspect of the present disclosure includes a splice housing body comprising a raceway within which optical fibers can be positioned, at least one port through the splice housing body to which a pressure fitting for optical fiber can be mounted, a base to which the splice housing body may be removably attached, and a port in one of the splice housing body or base for inserting fluid in the splice housing body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to the following two applications filed the same day as this application, which are both incorporated in this application in their entireties by reference: (1) application Ser. No. ______, for “Hybrid Electrical and Optical Fiber Cable Splice Housings,” Park, et al, inventors, attorney docket no. 61429-897059 and (2) application Ser. No. ______, for “Mounted Downhole Fiber Optics Accessory Carrier Body, Park, et al., inventors, attorney docket no. 61429-896456. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This disclosure relates to fiber optic cables utilized in oil and other wells and other extreme environments and to splices and Y-connections of such cables. 
       BACKGROUND 
       [0003]    Distributed fiber optic sensors and fiber optic cables are commonly clamped to the tubing or casing during run-in-hole (RIH). The cables are cut at packers and re-spliced once they are fed through the packers, or cut and spliced at sensor locations. In other situations, end terminations or in-line splices are needed. Conventional practice is to take the cables and sensors to a cabin with positive pressure to remove any explosive gases, or to another safe area to prepare and splice the fibers/cables, and then take the finished assembly to the rig-floor and attach the assembly to a pre-manufactured gauge mandrel. The process of moving cables and system components takes time, and rig-time is very expensive. Any reduction in rig-time therefore results in significant savings. 
         [0004]    Similarly, space is expensive, and larger casing sizes require larger mandrel sizes for a given tubing size. A splice housing must be designed to survive bottom hole pressures, and the mandrel must be designed to survive bottom hole pressures during stimulation and production. 
         [0005]    Many applications use a tubular linear splice housing for the splices, and Y-blocks are attached to the end of the splice housing to break out a fiber for a sensor such as a pressure sensor. The length of the splice and associated machined mandrels may be substantial, which increases cost and complexity. A longer machined mandrel requires a more expensive machine for manufacturing, and the cost is therefore higher. 
         [0006]    In existing linear splice configurations, the length of fiber in the splice tray is equivalent to the length of the pressure housing. The fiber is fixed at each end of the splice tray, in some instances with an adhesive like epoxy or room temperature vulcanizing (“RTV”) adhesive. As a result, when the splice housing is lowered in the well bore, it increases in temperature and expands, as does the fiber. However, the coefficient of expansion of the metal is typically an order of magnitude greater than the fiber. As a result, the fiber is stressed in tension, which can affect the optical signals, and the fiber can break. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Illustrative embodiments are described in detail below with reference to the following drawing figures: 
           [0008]      FIG. 1  is an isometric view of a splice housing lid. 
           [0009]      FIG. 2  is an exploded perspective view an alternative embodiment of the splice housing lid shown in  FIG. 1  together with an optional simple cover, seals and other attachments. 
           [0010]      FIG. 3  is an isometric view of a curved base, oval or oblong raceway fluid-filled fiber optic splice housing assembly with two pressure sensors and a “transparent” splice housing lid. 
           [0011]      FIG. 4  is a similar view of the housing assembly and sensors of  FIG. 3  with an opaque splice housing lid. 
           [0012]      FIG. 5  is an isometric view of a portion of a solid, machined mandrel with the fiber optic splice housing and pressure sensors of  FIG. 2  shown attached to a flat surface of the mandrel. 
           [0013]      FIG. 6  is an isometric view of the mandrel shown in  FIG. 5  without the splice housing or sensors attached. 
           [0014]      FIG. 7  is an isometric view of a modular mandrel assembly with collars securing a splice housing and sensor cover on a section or length of round casing. 
           [0015]      FIG. 8  is an enlarged view of the splice and sensor housing shown in  FIG. 7  with a transparent splice housing and sensor cover. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The subject matter of embodiments of this patent is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. 
         [0017]    At high temperatures, current linear splice housings can expand in length much more than the fiber due to differences in the thermal expansion of metal and glass. This creates stress in the fiber that can affect the optical properties of the signal, or in some cases, cause the fiber to break. Elimination of stress and breakage and increased splice reliability are key to the successful operation of down hole fiber telemetry. 
         [0018]    A fiber optic splice housing in accordance with this disclosure may be used down hole for optical fiber splicing to connect fiber optic sensors and devices to optical fiber in FIMT (fiber in metal tube) or other optical fiber. Typical sensors that may be connected with these devices and methods include pressure sensors, flow sensors and the like. The splice housing assemblies of this disclosure can house, among others, end splices, through splices, single gauges, gauges and through splices and two gauges and through splices. 
         [0019]    The splice chamber of this disclosure may be filled with fluid to prevent gel from the FIMTs travelling into the housing, which can also cause fiber breakage because the gel sometimes pulls fiber into the splice housing. 
         [0020]    Incorporation of a Y-splitter in the same splice housing eliminates multiple connections and the need for a secondary housing. This simplifies and shortens the required structures, which reduces the length of the mandrel to which it is mounted. 
         [0021]    Other embodiments provide a modular mandrel and associated hardware to simplify and shorten the design, to minimize cost, to minimize rig time, to make a slimmer overall package than existing pressure gauge mandrels and splice hardware. 
         [0022]    The splicing techniques and apparatus described here can make use of a zone-rated fiber optic splice kit and techniques. Because this apparatus can hold a sufficient length of fiber in loops, there is sufficient length to get the splice joint in the raceway of this apparatus (described below). In order to use a zone rated splicer with a linear splice housing, the linear splice housing would have to be much longer than it is currently, necessitating a longer mandrel to house it. 
         [0023]    The splice housings of this disclosure utilize versatile splice housing bodies or “lids” usable with a variety of bases, mandrels and other structures to form a splice housing assembly within which splices and other structures are positioned and to which sensors and other devices may be attached. The housing assemblies of this disclosure may be used for end termination, pass through splices, gauge mounting and combinations of these. Splice housing assemblies could also be structured for the housing body to be formed in a mandrel or other base for use with a simpler cover. Such a structure may, however, be more difficult or expensive to manufacture and may forgo the versatility of incorporating the housing body cavity within the lid as described and illustrated here. 
         [0024]    The figures depict two exemplary splice housing lids. A first embodiment is shown as lid  8  in  FIG. 1 . A second embodiment is depicted as lid  10  in  FIGS. 2, 3, 4, 5, 7 and 8 . Numerous other lid configurations in accordance with this disclosure are possible. 
         [0025]    As shown in  FIG. 1 , splice housing lid  8  has a flat mounting surface  9 , a curved outer surface  11 , and lid  8  defines an oval or oblong “raceway”  12  within which fiber optic cable, splices, connections to sensors and other similar structures may be housed and protected when lid  8  is attached, typically with machine screws, to a base to form a splice housing assembly. Raceway  12  may have alternative shapes, including, without limitation, round and oval or oblong with different proportions than the exemplary proportions of those shown in the drawings. 
         [0026]    Lid  10  (shown in  FIGS. 2, 3, 4, 5, 7 and 8 ) likewise utilizes an oblong raceway  12  but also includes two disks  13  around which cable can be wound. An optional, simple plate-like cover (an example of which is shown as cover  29  in  FIG. 2 ) may be attached to the lid  8  or  10  to retain fiber cables within the lid until the lid and simple cover can be attached to a base. 
         [0027]    When attached to a base such as base  26  shown in  FIGS. 3 and 4 , lids  8  and  10  provide an oval or oblong, pressure tight, fluid-fillable enclosure for fiber optic cable  14  that is part of FIMT  15 . The FIMT  15  that runs to the surface contains multiple fibers that can be Multi-mode or Single-mode or a combination of both. As depicted in  FIGS. 2, 3 and 4 , the FIMT  15  is connected to the lid  10  using pressure or compression fittings  20  in one end  21  of the lid  10 . The compression fittings  20  lead fiber  14  through ports  16  in lid  10  (as well as lid  8 ), and the fibers  14  are laid in the raceway  12  inside the lid  10 . The inside-the-lid openings  22  of ports  16  through which cables  14  enter the raceway  12  are most clearly visible in  FIG. 1 . At the opposite end  23  of lid  10 , gauges  18  are connected to the lid  10  through ports  16  using compression fittings  20 . Fibers  14  from the gauges  18  likewise pass into the lid  10  and are laid in the raceway  12 . 
         [0028]    As is depicted in  FIG. 1  showing lid  8 , raceway  12  need not contain additional structures. However, positioning of fiber cables  14  in the raceway  12  can be facilitated by one or more structures within the raceway such as pins or other structures around which the fiber cables  14  are loosely wound to facilitate placing and retaining the fibers within the splice housing as desired. Similar “loose winding” or loose loops of fiber may be positioned in the fiber housings of this disclosure without use of pins or other structures within lids  8 ,  10  or other embodiments of this disclosure. This loose winding also allows for relative expansion between fiber and the raceway  12  to compensate for thermal expansion, in addition to providing room for significant lengths of additional fiber, reducing stress on the fiber and accommodating subsequent changes if needed. 
         [0029]    As examples, winding structures may be one, two (or more) cable wind cylinders or disks  13  within lid  10 . These disks  13  may be integrally formed with the lid  10  or separately formed and secured to the lid by screws, bolts, pins, adhesives or other appropriate fasteners. As but one example of alternatives to full disks  13 , one half-disk having a D-shape may be positioned at each end of the oval raceway  12  with each half-disk curved surface facing one of the curved ends of the raceway  12 . 
         [0030]    In addition to the cable management functions described below, disks  13  may provide support for the housing by contact between the disks  13  and the base structure to which the lid  10  is attached when assembled with a base such as base  26 . 
         [0031]    Optional disks  13 , if used, may have either a straight or a sloping peripheral edge or wall  25 . With a sloping peripheral wall  25 , disks  13  are not cylindrical sections but are truncated conical sections with the smaller diameter face against the floor of the raceway  12  in lid  10 . Wall  25  of each disk  13  may alternatively have a more complex shape. For instance, wall  25  may be concave, curving from top to bottom as well as around the disk  13 . It is desirable for cable  14  to be loosely positioned within a raceway  12 . However, disks  13  with an inward-sloping peripheral wall  25  so that the bottom of the disk  13  in the bottom of the raceway  12  is smaller in diameter than the portion at the top of disk  13  may facilitate retention of the cables  14  in the raceway  12  when the lid  10  is not in place on a base, because a loop of cable  14  even relatively loosely wound around such a sloping-wall disk  13  must expand in order to slip off of the disk  13 . T-slots or other cable management structures may also be usable in lid  8  or  10  if desired. 
         [0032]    Other numbers and locations of ports  16  and compression fittings  20  than those depicted in the drawings may be used to provide appropriate access consistent with the needs of a particular installation. Because fibers  14  are laid loosely in or pushed into the ends of the raceway  12  and are not wrapped tightly around or attached to structure, different lengths of fibers  14  can be accommodated, there is “extra” fiber  14  with which to splice or to which other fiber can be attached, and there is significantly reduced likelihood the fiber  14  will break. 
         [0033]    Different combinations of gauges, pass through FIMTs, end terminations for DTS (distributed temperature sensing) or DAS (distributed acoustic sensing) fiber, or in-line splices can all be accommodated. By having multiple inlets and outlets in the splice housing assemblies of lid  8  or  10 , the need for a secondary Y splitter housing is eliminated. When a port  16  is not used, it may be plugged. In an exemplary situation, a splice assembly of this disclosure may accommodate a DTS termination, a DAS termination, an inline splice to a pass-through FIMT to connect to sensors lower down the production string, and to an internal pressure gauge and an external pressure gauge. Thus, one FIMT  15  to the surface may carry six or more fibers. 
         [0034]    Strain gauges may also be placed within the raceway  12  of the lid  8  or  10 . 
         [0035]    The fibers  14  within lid  8  or  10  and other lids and housings described herein can be joined by normal splicing techniques using fusion splicers and recoating tools, or splice protectors, or the fibers can be joined using miniature fiber connectors or other means. The raceway  12  provides space for connectors if connectors are used, which linear splice housings may not provide. The raceway  12  also accommodates “crossover” of fiber  14  so that a fiber  14  can reverse direction, although “crossover” of fiber  14  to accomplish a fiber turnaround may also be done in a lid  8  not having disks  13 . The fiber lies loosely in the channel or raceway  12  so that the metal lid  8  or  10  can expand and contract as temperature fluctuates without forcing the fibers  14  in the lid  10  into stress or shear. 
         [0036]    Prior to assembly of the lid  8  or  10  and base  26 , the fibers  14  are held in place within the lid  8  or  10  by the sides and ends of the raceway  12  and by optional disks such as disks  13  in lid  10  and by an optional cover  29  shown in  FIG. 2  that may rest on disks  13 . 
         [0037]    After assembly of lid  8  or  10  and base  26  or another appropriate base structure, the cavity in lid  8  or  10  provided by raceway  12  is closed by the base  26  that may utilize guide pins (not shown) to facilitate alignment and that may be secured to the lid  8  or  10  with screws, bolts or other appropriate fasteners or fastener structures. In light of possible internal pressurization of the lid  8  or  10  and base  26  assembly, and the external pressure environments within which the assembly may be used, an effective seal between the lid  8  or  10  and base  26  is necessary. Such a seal can be achieved by providing a groove  17  (best seen in  FIG. 1 ) surrounding the raceway  12  in one of (a) the lid  8  or  10 , or (b) base  26 , within which groove  17  one or two C-seals  28  or other sealing material may be placed. Assembly of the lid  8  or  10  and base  26  will then compress the C-seal or rings or other seal between the two lid and base components while the groove keeps the seal(s) properly positioned. Alternatively, two or more pairs of grooves, such as concentric grooves, may be used in one of the lid  8  or  10  and base  26 , together, for instance with C-rings of appropriate resilient sealing material. 
         [0038]    A pressure test port  19 , which passes through lid  8  or  10  into groove  17  (and is visible in  FIGS. 1 and 4 ) can provide the ability to test the sealing capability of the C-seals after assembly. 
         [0039]    Fill port  36  (visible in  FIGS. 1, 2, 3, 4 and 5 ) enables the raceway  12  cavity in lid  8  or  10  (when a lid is assembled with a base  26  or other appropriate base) to be filled with appropriate fluid that optionally may be pressurized. Such pressurization prevents gel inside the FIMT from travelling into the splice housing assembly of lid  8  or  10  and base  26 , which can cause the fiber  14  to break inside the FIMT. A vent port can also be included if desired, through which gas can vent when the splice housing assembly is filled or pressurized with a fluid. Alternatively, filling and venting can be performed alternatively through the same port. 
         [0040]    As is indicated by the shape of the bottom of base  26  shown in  FIGS. 3 and 4 , the bottom  24  of base  26  may be curved, preferably in the shape of a segment of a cylinder matching the surface of well casing with which the splice housing assembly of lid  10  and base  26  is used. This permits the lid  10 /base  26  splice housing assembly to be strapped or clamped to such well casing (not shown) with the base  26  in contact with the casing and facilitates secure attachment. 
         [0041]      FIG. 5  shows an alternative splice housing assembly  30  utilizing a machined mandrel  32  (shown separately in  FIG. 6 ). A flat surface  34  of mandrel  32  (see  FIG. 6 ) serves as a base to which a lid  8  or  10  may be attached. Like splice housing assemblies of lids  8  or  10  and base  26 , a splice housing assembly of lid  8  or  10  and mandrel  32  houses all the splices, and the mandrel  32  and sensor cover  50  hold sensors or gauges  18  and sensor cables  52 . 
         [0042]    Unlike conventional mandrels that use a linear splice housing and are about nine feet long, or longer if a Y splice and full length gauges were installed, the mandrel  32  may be much shorter and simpler to produce. The assembly of the mandrel  32  and other components to provide housing assembly  30  during RIH (run in hole) is significantly easier than is the case for a conventional linear splice housing, and raceway  12  provides significant flexibility. If the fibers  14  can be spliced on the rig-floor using a zone rated splicer even more time will be saved. 
         [0043]    In another alternative embodiment depicted in  FIGS. 7 and 8 , a modular splice housing assembly  40  may include a lid  10 , sensor base  48  and associated components secured to a carrier  44  that serves as a base and is in turn secured to a cylindrical casing  42  with two collars or end rings  46 . The housing assembly  40  holds all the cable  14  splices, and all of the cables, including sensor cables. 
         [0044]    Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described, are possible. Similarly, some features and subcombinations are useful and may be employed without reference to other features and subcombinations. Embodiments of the disclosure have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present disclosure is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications can be made without departing from the scope of the claims below. 
         [0045]    For instance, the raceway  12  within the lids  8  and  10  may be other appropriate shapes in addition to the oval or oblong shapes depicted in the Figures. Such raceways may be round and egg-shaped, among other alternatives providing the capacity to receive differing lengths of optical fiber and fiber splices and protect such fiber and splices from damage throughout the time the optical fiber needs to be in use. Additionally, such a raceway cavity may be machined directly in a mandrel and then covered with an appropriate lid or cover. Sensors may or may not be used with or mounted to the splice housing structures and different sensors than the types mentioned herein may be used.