Abstract:
A downhole fiber optic protection system is disclosed which includes at least one protector sub mounted in a downhole string, the protector sub having at least one recess formed in an outside diameter of the protector sub and optionally including component protectors mounted to the outside diameter of the protector sub whereby the one or more recesses in the outside of the protector sub provide protection to fiber optic components and protected areas are created underneath component protectors further more delicate of the fiber optic connectors. The device is designed to prevent the harsh downhole environment from adversely affecting optical fibers themselves or optical components in the optical fiber system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Ser. No. 60/155,632, filed Sep. 23, 1999, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the field of hydrocarbon exploration, drilling and production. More particularly, the invention relates to subsurface systems employing fiber optic conductors, connectors and instrumentation and protection required and desirable for the same. 
     2. Prior Art 
     In recent years, the use of fiber optic technology has grown in many industries. The benefits of using fiber optics where electric conductors were used previously has greatly improved communications in both the quality of information transmitted and received, and the speed of communication. Unfortunately however, many of the benefits of fiber optic technology have not heretofore been available to the hydrocarbon exploration, drilling and production industry due to the extremely unfavorable conditions downhole. These, of course, are high pressure, high temperature, vibration, caustic fluids, etc. All of these conditions collectively and individually are significantly deleterious to delicate optic fibers and would cause very early failures requiring workovers in production wells if employed as they have been in other industries. Because of this, the incorporation of optic fibers downhole, in all but the most limited of circumstances, has been contraindicated. Due to the technological benefits of fiber optic usage, the industry is in need of a way to deploy and employ fiber optics reliably in the downhole environment. 
     SUMMARY OF THE INVENTION 
     The above-identified drawbacks of the prior art are overcome, or alleviated, by the fiber optic protection system of the invention. 
     Fiber optic conductors, connectors, instrumentation, sensors and associated control circuitry (hydraulic/electrical/optical), etc. are now employable in the downhole environment in connection with the invention disclosed herein. The protection system insulates fiber optic technology from the unfavorable conditions existing downhole so that such technology may be reliably employed, thus allowing the subsurface portion of the hydrocarbon industry to reap the benefit of fiber optic technology. Optical fibers allow greater accuracy and speed of determining information downhole. Decisions are faster made and adjustments in different zones may be executed quicker to enhance production of desired fluids while retarding production of undesirable fluids. 
     The scope of the invention also includes the routing of surface supplied power (hydraulic/electrical/optical) through a protected environment to the downhole fiber optic components to selectively supply said power to any number of a multitude of downhole tools, as desired. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1 is a schematic representation of the protection system of the invention connected with the other tools. 
     FIGS. 2-4 is an elongated longitudinal cross-section view of the manifold sub of the invention; 
     FIGS. 5-7 is an elongated plan view of the top of the manifold sub of the invention; 
     FIGS. 8-10 is an elongated plan view of the bottom of the manifold sub of the invention; 
     FIG. 11 is a cross-section view of the invention taken along section line  11 — 11  in FIG. 2; 
     FIG. 12 is a cross-section view of the invention taken along section line  12 — 12  in FIG. 2; 
     FIG. 13 is a cross-section view of the invention taken along section line  13 — 13  in FIG. 2; 
     FIG. 14 is a cross-section view of the invention taken along section line  14 — 14  in FIG. 2; 
     FIG. 15 is a cross-section view of the invention taken along section line  15 — 15  in FIG. 3; 
     FIG. 16 is a cross-section view of the invention taken along section line  16 — 16  in FIG. 3; 
     FIG. 17 is a cross-section view of the invention taken along section line  17 — 17  in FIG. 3; 
     FIG. 18 is a cross-section view of the invention taken along section line  18 — 18  in FIG. 3; 
     FIG. 19 is a cross-section view of the invention taken along section line  19 — 19  in FIG. 3; 
     FIG. 20 is a cross-section view of the invention taken along section line  20 — 20  in FIG. 4; 
     FIG. 21 is a schematic view of a partial cross-section of the splice box of the invention; 
     FIG. 22 is an enlarged view of the circumscribed area of the splice box in FIG. 21; and 
     FIG. 23 is a plan view of a splice box of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Fiber optic systems for downhole monitoring and control are most favorably placed within a protected environment in a housing. The housings include beveled edges to avoid impact or shock loading on corners during running into the well and they include protective covers over all exposed openings for the same purpose. Moreover, the fiber optic components being employed are preferably mounted in a vibration/shock load dampening material (for example, teflon, metal, or similar), which is chemically inert with respect to the well content, to guard them for any vibration or shock loading that does occur. 
     In order to provide one of skill in the art an understanding of the concept embodied by the invention, FIG. 1 illustrates several downhole tools and optic components in one possible configuration. The drawing is schematic but is apt to illustrate the concept of the invention. The manifold sub  7  houses many of the fiber optic components such as optic dry-mate connectors, optic splices, fiber optic service loops, optic hydraulic valves, optic-electric valves, fiber optic pressure sensors, fiber optic temperature sensors, optic wet-mate connectors, etc. and is an important subassembly of the protection system disclosed in more detail hereunder. Other protective sub-assemblies are also illustrated in FIG. 1 referring to the splice box  6  (which may or may not be integral to the manifold sub), service loops  8  and connector subs  3 . Each provides protection against mechanical loading, temperature effects and pressure effects. The components also include outer features to reduce the occurrence of impacts with other structures while being run into the hole. These too are discussed hereunder. 
     In a particular embodiment of the manifold sub  7 , referring to FIGS. 2-4, control lines conveying optic fibers and hydraulic fluid, optic fiber components and associated control components are illustrated in various cross sectional and plan views. One of skill in the art will recognize that all of the conduits in the manifold sub  7 , be they optic fiber or hydraulic control lines, are protected within the manifold sub body  11  between a centrally located recessed channel  12  in the manifold sub body  11  and the outer surface of the manifold sub body  11 , or one of a series of component protectors  13 - 20 . It is to be understood that a protected space is provided under each of the component protectors. 
     In one embodiment, the component protectors  13 - 20  are designed so that they are flush with, or below the outer surface of the manifold sub body  11 . This reduces the risk of the component protectors  13 - 20  catching on another structure downhole and causing an impact or shock load to be transmitted to the components housed within the manifold sub. The component protectors  13 - 20  have beveled edges to ensure against impact loading on corners while running. The component protectors  13 - 20  are secured over the various fiber optic components housed within the manifold sub  7  to form an interference fit, such that substantial load must be applied, via a distributed load system comprising of a multitude of cap screws  21  being threadedly connected to the manifold sub body  11  through a series of clearance holes  70  (visible in some views only) in the component protector  13 - 20 , to deflect the component protector material adequately to fully secure the component held therein against vibrational/load effects. The cap screws  21  are locked in place with locking washers, or thread locking adhesive, or similar, to ensure against load dissipation. Additionally, the component protectors  13 - 20  are manufactured very accurately to form a very close fit between the component protectors  13 - 20  and the recessed channels  12  and  29  in the manifold sub body  11  into which they are installed. This ensures against axial movement and lateral movement of the fiber optic components housed between the recesses in the manifold sub body  11  and the component protectors  13 - 20  due to tension/vibration effects within the connections to the fiber optic components. All component protectors  13 - 20  are easily replaceable without detriment to the other components of the manifold sub  7 . Other features of specific component protectors  13 - 20  will be discussed in depth later in this document. 
     The manifold sub  7  is tubular and may be either concentric or eccentric with respect to the casing bore  4  within which the manifold sub  7  is located and places all of the control lines and fiber optic components (discussed hereunder) within the annular body thereof. The manifold sub  7  may be supplied with metal-to-metal sealing threaded connections  22  at either end to allow connection to the tubing  1 , or other components of the system, as represented in FIG.  1 . The manifold sub body  11  may in one embodiment be bored to accept certain components or may in another embodiment be milled radially to accept components which then are covered with component protectors  13 - 20  as noted previously, or both concepts are employable together. Well fluids are permitted to flow through the internal bore of the manifold sub  7  and within the annulus between the casing bore and outer surface of the manifold sub body  11 . 
     Referring to FIGS. 2-4, the fiber optic working control line  23  (denoted thus as it contains the optic fibers which are connected to various fiber optic components housed within the manifold sub  7 ) is visible in the top half of the drawings. The fiber optic working control line  23  is housed in a recess  12  in the manifold sub body  11  which can be viewed in FIG. 11, which is a cross section view of the manifold sub  7  of the invention taken along section line  11 — 11  in FIG.  2 . Also within this recess  12  are contained spacer rods  24  constructed of impact/vibration dampening material capable of withstanding downhole temperature and pressure and of being chemically inert with respect to the well content (for example, teflon, metal, or similar). On either side of the spacer rods  24  are hydraulic fluid input control lines  25  which may be connected to other devices within manifold sub  7 , such as optic-hydraulic valves  26  as displayed in the particular embodiment, or pass therethrough, to another manifold sub  7  in the next well zone. Fiber optic working control line  23  is connected to other optic components within manifold sub  7  and is distributed within and without manifold sub  7 . In the particular embodiment represented, fiber optic working control line  23  is connected to a number of optic-hydraulic valves  26  and a fiber optic pressure sensor  27 , but various other fiber optic components could be employed within the manifold sub  7 . Fiber optic connector control line  28  is also visible in the bottom half of FIGS. 2-4, and FIGS. 8-11 Fiber optic connector control line  28  is also housed in a radially milled recess  29  in the manifold sub body  11 . It should be appreciated that all the control lines illustrated in FIGS. 2-10 are protected by an upper gauge ring  30  and lower guage ring  31 , which preferably are annular portions of the manifold sub and are the maximum outer diameter of the manifold sub  7 . Upper and lower guage rings  30  and  31  are specifically configured, manufactured and treated utilizing close tolerance fits and geometry that yields low stress levels during impact/shock and axial and rotational loading while running the manifold sub  7  into or out of the well. Upper and lower guage ring  30  and  31  have beveled edges to ensure a smooth transition to the maximum tool diameter and prevent shock loading on sharp corners. Upper and lower guage ring  30  and  31  ensure that the manifold sub body  11  and component protectors  13 - 20  are not subjected to the mechanical forces encountered while traversing a well. A preferred method of connection of upper and lower guage ring  30  and  31  to manifold sub body  11  may be via a threaded connection  32  between guage ring  30  inner diameter and manifold sub body  11  outer diameter. An alternative method of connection may also be to split the guage ring  31  and install it in a turned recess  33  in the manifold sub body  11 , retaining it in situation via a number of cap screws  34  threadedly connected to the manifold sub body  11 . Rotational resistance may be provided by set screws  35  threadedly connected to the guage ring  30  and locked against manifold sub body  11 , as shown in FIG. 12, or by a key  36  installed between guage ring  31  and manifold sub body  11 , as shown in FIG.  19 . 
     In FIG.  3  and FIG. 14, a component protector  13  covers, protects and further insulates the fiber optic 3-way angled junction  37 , which distributes various optic fibers safely and without imparting excessive bending stresses within the fiber to the various optic components housed within the manifold sub  7 . Also shown in FIGS. 2-10 and FIGS. 14 and 15, component protector  19  protects the fiber optic 3-way angled junction  38  and a multitude of optical connectors  39  connected to it. It should be appreciated that all pressure resisting connections between components of the protection system are of a non-elastomeric nature or metal-to-metal sealing and the protection system has been designed such that all potential leak paths have been optimized. Methods of eliminating potential leak paths include welding of component sub-assemblies together. Component protector  19  includes profiles such that the optical connectors  39  are prevented from rotational movement during threaded connection make-up to the mating end of the optical connector  40 . This feature assists in assembly procedures while running the protection system into the well and attaching the necessary ancillary optic fiber control equipment. 
     Referring now to FIGS. 2-7 and FIG. 15, pressure sensor  27  is illustrated between the radially milled recess  12  in the manifold sub body  11  and the component protector  14 . Fiber optic working control line  23  terminates at the pressure sensor  27 . Hydraulic fluid input control lines  25  continue through the milled recess  12  in manifold sub body  11  and are restrained from vibration and protected from mechanical loading by component protector  15 , shown in FIGS. 2-7 and FIG.  16 . Dependant on required length of hydraulic fluid input control lines  25  within manifold sub  7 , and number of components to which they are attached, a multitude of such component protectors  15  may be used. Prior to exiting the manifold sub body  11 , below the lower guage ring  31 , hydraulic fluid input lines  25  are, in this embodiment, weldedly connected to angled junction pieces  41 , shown in FIGS. 5-7 and FIG.  17 . Angled junction pieces  41  are installed in the milled recess  12  in the manifold sub body  11  and covered by another component protector  17 , providing the same function as previously described component protectors  13 - 20 . Angled junction pieces  41  are used to reduce the otherwise unacceptable bend radius of the control line in order that it can be safely installed within the confines of the milled recess  12  within the manifold sub body  11 . The angled junction piece  41  routes hydraulic fluid, in this embodiment, to the input side of an optic-hydraulic valve  26 , located between a recess  42  in the manifold sub body  11  and a component protector  16 . The recess  42  housing the optic-hydraulic valve  26  is connected to the main recess  12  in the manifold sub body  11  via a radially milled connecting slot  43 . Hydraulic fluid output lines  44  are connected to the output side of the optic-hydraulic valves  26  and exit the manifold sub body  11  via a continuation of the milled recess  42  in which the optic-hydraulic valve  26  is housed. Component protector  18  is installed over the recess  42  to prevent vibration of the hydraulic fluid output control line  44  and to protect it from mechanical loading, as shown in FIGS. 5-7 and FIG.  18 . Dependant on the configuration of the manifold sub  7 , a multitude of component protectors  18  may be required. 
     Referring now to the bottom half of FIGS. 2-4, FIGS. 8-10 and FIG. 16, the optical connectors  39 , installed in the recesses in the manifold sub body  11  are connected to the mating ends of the optical connector  40 . This sub-assembly is not part of the manifold sub  7  per se, but is ancillary control equipment installed during running of the manifold sub  7  into the well, and is shown for illustrative purposes only. In order to connect the mating end of the optical connector  40  to the optical connector  39 , it is necessary to remove the component protector  20 . The component protector  20  is secured by cap screws  21  which have been selected for ease of removal and installation in an offshore environment. The component protector  20  is a one-piece assembly, again to assist in disassembly/assembly procedures. The bottom half of the lower guage ring  31  is also removed from it&#39;s turned recess  33  in the manifold sub body  11  and the mating end of the optical connector  40  is installed within the milled recess  29  in the manifold sub body  11 . Upon making up the threaded connection between the mating end of the optical connector  40  and the optical connector  39 , the bottom half of the lower gauge ring  31  and the component protector  20  are replaced, the cap screws  21  and  34  locked in position, via locking washers, or thread adhesive, or similar. Referring now to FIGS. 2-7, the hydraulic fluid input lines  25  and hydraulic fluid output lines  44  may terminate in special connection ports  45 , welded onto the end of each of the lines. These connection ports  45  accept control lines connected to downhole tools, such as the Hydraulic Sliding Sleeve  9 , as shown in FIG. 1, below the manifold sub  7 , and provide a method of sealing the conduit against well conditions such as temperature, pressure and well content. Typically, such seals will be of a metal-to-metal nature. 
     Within the context of the invention, the manifold sub  7  protects optic fiber component assemblies from the unfavorable conditions existing downhole. However, as the system is designed to protect hardwired optic components and fibers, there is also a need to provide a protected environment in which to house the required splices between individual optical fibers. While splicing of separate optical fibers together is common practice in many industries, and provisions exist for housing said splices, there are no existing enclosures which protect against the unfavorable conditions experienced downhole. Referring to FIG. 1, the optic fiber splice box sub  6  of the invention houses these splices in a secure environment, providing protection from the conditions within the well, be they temperature, pressure, or mechanical loading, or a combination thereof. While the drawing is schematic, it is apt to illustrate the concept of the invention. The optic fiber splice box sub  6  is an important sub-assembly of the protection system disclosed in more detail hereunder. 
     In order to provide one of skill in the art an understanding of the concept embodied by this aspect of the invention, FIGS. 21-23 illustrate a particular embodiment of the optic fiber splice box sub  6 . The splice box sub  6  is tubular and may be either concentric or eccentric with respect to the casing bore  4  within which the splice box sub  6  is located. The splice box sub body  46  may be supplied with metal-to-metal sealing threaded connections  47  at either end to allow connection to the tubing  1 , or to other components of the system, as represented in FIG. 5, or it may be supplied as an integral part of the manifold sub  7 , being located above the upper gauge ring  30  of said manifold sub, as represented in FIG.  1 . The splice box sub body  46  may be bored to accept certain components or may be milled radially to accept components which are then covered with an enclosure cover  48 . Well fluids are permitted to flow through the internal bore of the splice box sub  6  and within the annulus between the casing bore  4  and outer surface of the splice box sub  6 . 
     The splice box sub body  46  and follower nut  49  include beveled edges to provide a smooth transition to the maximum tool diameter and to avoid impact or shock loading on corners during traverse of the well. Splice box body  46  and follower nut  49  are specifically designed, manufactured (precision machining) and treated (hardened surface preparation) utilizing close tolerance fits and geometry that yields low stress levels during impact/shock and axial and rotational loading while running the splice box sub  6  into or out of the well. Splice box sub body  46  and follower nut  49  ensure that enclosure cover  48  is not subjected to the mechanical forces encountered while traversing a well. 
     Fiber optic working control line  23  and fiber optic connector control line  28  are connected to the splice box sub fiber optic enclosure  50  via ports  51  drilled into the fiber optic enclosure  50 , through the splice box sub body  46 . These connections are sealable by a metal-to-metal sealing Jam Nut and Ferrule arrangement  52 . The fiber optic conveying control line  53 , housing the fibers to which the fibers within the fiber optic working control line  23  and fiber optic connector control line  28  must be spliced is connected to the fiber optic enclosure using the same general method. Moreover, additional ports  51  may be provided for the purpose of pressure testing the fiber optic enclosure  50  upon completion of the splicing procedure, or for the purpose of filling the void within the fiber optic enclosure with a chemically inert material, unaffected by temperature and pressure effects (for example, epoxy resin or similar) for the purpose of providing further resistance to vibrational effects within the fiber optic enclosure  50 . Upon completion of said procedures, said ports  51  will be metal-to-metal sealed using Blanking Plugs, or similar. 
     Referring to FIG. 23, the fibers within the various control lines are introduced into the fiber optic enclosure  50  and the appropriate ends spliced together, to form a ‘hardwired’ continuous optic circuit. In order to achieve this, a considerable length of fiber is required, which must then be housed in a suitable protective enclosure  50 , resistant to the deleterious effects of the inhospitable downhole environment (pressure, well content, etc.). Additionally, the internals of the enclosure  50  must ensure that the optic fiber  55  is not excessively bent during insertion into the enclosure, and that the bend radius of the fiber is kept to a maximum to ensure optic losses are kept to a minimum. This is especially critical at elevated temperatures. In order to achieve this desired aim of the invention, the optic fiber enclosure  50  is fitted with a series of cylindrical guides  54  around which the fibers  55  are wrapped. These fiber guides  54  provide general positioning of the fiber  55  within the confines of the fiber optic enclosure  50  and are tightly toleranced with respect to the walls of the enclosure  50 , to ensure that vibration effects will not cause excessive movement and cause damage to the fiber  55 . The fiber guides  54  are manufactured from a vibration/shock loading dampening material (for example, teflon, metal, or similar). In addition to the fiber guides  54 , a number of fiber wrap subs  56  are provided. The fiber wrap subs  56  are profiled to mate with the inner surface of the fiber optic enclosure  50  to ensure against rotational movement. Additionally, they are secured to a boss  58  in the enclosure  50  inner surface via a tightly toleranced dowel pin  57 . The fiber wrap subs  56  have a shallow groove machined around the outer diameter to assist in wrapping of the fiber  55  around them. Upon completion of the wrapping process, the fiber wrap sub cap  59  is installed and locked to the fiber wrap sub  56  via a key  60 , preventing movement of the cap  59  and thereby preventing any damage to the fibers. Fiber wrap sub  56  and cap  59  are manufactured from a vibration/shock load dampening material (for example, teflon, metal, or similar). 
     In order to seal the optic fiber enclosure  50  from the downhole environment, the enclosure cover  48  is then slid into place to seal on the non-elastomeric or metal-to-metal seals  61 , housed within grooves in the splice box sub body  46 . The follower nut  49  is then threadedly connected to the splice box sub body  49  until it secures the enclosure cover  48  tightly in place. The follower nut is then locked in place via a lock nut, or set screws, or thread locking adhesive, or similar. 
     At this stage, the seals  61  between the splice box sub body  46  and enclosure cover  48  can be fully pressure tested to verify leak tightness. Confirmation of pressure integrity can be obtained via the additional ports  52  in the splice box sub body  46 . The sealed optic fiber enclosure  50  can then be pumped full of void filling, vibration/shock load dampening material and the additional ports  52  sealed. The hydraulic fluid input control lines  25  are then placed over the bottom half of the splice box sub  46  and a protective cover  62  placed over the control lines. This protective cover  62  includes beveled edges to provide a smooth transition to the maximum tool diameter and to avoid impact or shock loading on corners during traverse of the well. The protective cover  62  is specifically designed, manufactured utilizing close tolerance fits and geometry that yields low stress levels during impact/shock and axial and rotational loading while running the splice box sub  6  into or out of the well. The cover is further preferably hardened to improved wear resistance. The cover is further preferably hardened to improve wear resistance. 
     The protective cover  62  ensures that the hydraulic fluid input control lines  25  are not damaged while traversing the well as they pass over the optic fiber enclosure cover  48 . The protective cover may be secured in place via cap screws threadedly connected to the splice box sub body  46 , or may be installed in a turned or milled groove in the splice box sub body  46 , providing resistance to axial movement. A key installed between the protective cover  62  and splice box sub body  46  provides resistance to rotational movement. Alternatively, the protective cover  62  may be designed to fit closely between the mating threads of the threaded connections  47  on each end of the splice box sub body  46 . 
     While preferred embodiments of the invention have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.