Patent Abstract:
An anomaly detector, used to sense the presence of tool collars, tool joints and other structures within a longitudinal space, that includes a protective housing. Sensory components are disposed within the protective housing and a port is provided for communication between internal and external components of the sensory system. A pressure containing region within the housing prevents the loss of pressure from within the detector, and protects the various components of the system from fluids and other materials constrained within the longitudinal space.

Full Description:
BACKGROUND OF INVENTION 
   The present invention relates generally to (but is not limited to) snubbing units that are used to vertically move a tubing string, formed from a series of tubing joints serially interconnected by larger diameter threaded tubing collars, or threaded upset ends, into and out of a pressurized well bore. 
   The typical snubbing unit used to vertically move a jointed tubing string into and out of a pressurized well bore moves the tubing string through a stationary riser spool on which vertically spaced upper and lower blowout preventers (BOPs) are operatively mounted. As is well known in this art, the BOPs are used to isolate the interior of the riser spool portion above them (normally at ambient pressure) from the much higher well pressure in the riser spool portion below them, while at the same time being openable and closable in “air lock” fashion to permit sequential passage therethrough of a series of tubing joint collars. Each BOP is sized so that in its closed position it forms a sliding pressure seal around the tubing joint being moved therethrough, and in its open position permits passage therethrough of the larger diameter tubing collar. 
   During lowering of a particular tubing collar toward the upper BOP, the upper BOP is open, and the lower BOP is closed. When the collar enters the intermediate riser spool portion between the upper and lower BOP&#39;s, downward tubing string travel is halted and the upper BOP is closed. The interior of the intermediate riser spool portion is then brought to well pressure by opening an equalizing valve to communicate the intermediate riser spool portion with such well pressure. After this pressure equalization is achieved, the lower BOP is opened, and the tubing string is further lowered to move the collar downwardly past the open lower BOP. 
   The lower BOP is then closed, and the interior of the intermediate riser spool portion is vented to the atmosphere by opening a bleed-off valve operatively connected to the intermediate riser spool portion. The upper BOP is then opened to ready the intermediate riser spool portion for downward receipt of the next tubing collar. A reverse sequence of BOP opening and closing, and pressurization and depressurization of the intermediate riser spool portion interior is, of course, used as the tubing string is being moved upwardly through the riser spool by the snubbing unit. 
   In the snubbing operation described above, it is important to temporarily terminate vertical tubing string movement after each tubing collar has entered the intermediate riser spool section through the open BOP, and before the collar strikes the closed BOP, to permit the necessary condition reversal of the BOPs and the pressurization or depressurization of the intermediate riser spool portion interior. Failure to temporarily stop each tubing collar at this position, as is well known, can cause severe disruptions of and lengthy delays in the snubbing operation. 
   For example, during forcible lifting of the tubing string through the riser spool, if a tubing collar is not stopped upon its upward entry into the intermediate riser spool portion it will forcibly strike the underside of the closed upper BOP. The continuing lifting force on the tubing string above the closed upper BOP can easily tear the tubing string apart at the jammed collar, thereby permitting the entire lower portion of the string to fall to the bottom of the well bore and causing a well blowout through the upper BOP. Also, if the tubing is being forcibly lowered through the riser spool, and a tubing collar strikes the closed lower BOP, the portion of the tubing string above the jammed collar can be easily crumpled and wedged within the riser spool. 
   The requisite precise positioning, and temporary stoppage, of each vertically successive tubing collar within the intermediate riser spool portion has been somewhat difficult to determine for two primary reasons. First, after each tubing collar enters the BOP assembly, it can no longer be seen by the snubbing unit operator. Second, there is often at least a slight variation in the collar-to-collar lengths in the tubing string. This arises from tubing joint length variances. Accordingly, it has been previously necessary for the snubbing unit operator to laboriously keep track of each successive collar-to-collar length in the tubing string to facilitate the essentially “blind” placement and stoppage of each collar within the intermediate riser spool portion. A slight calculation error, or an attention lapse by the snubbing unit operator, can thus easily cause breakage or crumpling of the tubing string 
   One method of determining the position of a tubing collar or joint within a BOP stack is demonstrated in U.S. Pat. No. 5,014,781 issued to Smith. Referring now to  FIG. 1 , a device according to Smith detects the approximate position of a collar  124  within a BOP stack  110  through the use of an upper  152  and a lower  154  electromagnetic coil affixed to the exterior of an intermediate riser spool section  114 . 
   SUMMARY OF INVENTION 
   In accordance with an embodiment of the invention, an apparatus is provided in which the presence of an anomaly of a longitudinal tube can be sensed through the use of one or more sensory components. The apparatus includes an external housing, for protection of the sensory components from external conditions. The external housing of this embodiment may also play a role in supporting an internal pressure-containing region. 
   In accordance with an embodiment of the invention, a method is provided for determining the presence of an anomaly of a longitudinal tube within a longitudinal hollow. Detection of direction of motion may also be determined through the use of directional sensory components or through the use of a plurality of sensory components, mounted within a protective housing. 
   Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a prior art sensor device. 
       FIG. 2  is a side view of an embodiment of the invention. 
       FIG. 3   a  is a frontal view of an embodiment of the invention, showing position of interface. 
       FIG. 3   b  is a frontal view of an embodiment of the invention, with interface removed and internal members visible. 
       FIG. 4  is a top down view of an embodiment of the invention. 
       FIG. 5  is a cutaway side view, showing internal members. 
       FIG. 6  is an embodiment of the invention, showing internal recess. 
       FIG. 7  is an embodiment of the invention, showing internal recess. 
   

   DETAILED DESCRIPTION 
   Referring to the drawings wherein like reference characters are used for like parts throughout the several views,  FIG. 2  shows, in accordance with an embodiment of the present invention, a housing  2  of a pressure containing anomaly detector (“PCAD”). In this embodiment, the housing  2  include a port  4  for communication with sensors or other components (not shown) located within the housing  2 . The housing  2  has one or more fasteners  8  disposed along the top and bottom for attaching the PCAD to adjacent components (not shown), including those commonly used in a BOP stack. These fasteners  8  may be of any form commonly used in the industry, including, but not to, tap end studs, and the housing  2  may be adapted to use various fasteners  8 . Such adaptation may include threaded holes, lips, indentations, threads and any other adaptations necessary to interact with a desired type of fastener  8 . Adjacent components may include, but are not limited to, tubes, pipes and spacers, such as may be used in oilfield applications. Furthermore, in another embodiment, the housing  2  of the PCAD may be integrated into such components so as to form a single unit. 
   The port  4  of an embodiment of the PCAD housing  2  is visible in  FIG. 3   a . One or more sensors or other components (not shown) may be disposed within the port  4 . Placement of components within the port  4  allows easy access for maintenance, upgrades, removal or installation of components. In keeping with such uses, the port  4  may vary in size, shape and structure based on the types of components used, the level of accessibility desired, the need to maintain the integrity of the housing  2  under various internal pressures, and other considerations. 
   Within the port  4 , may be mounted an interface  20 . This interface  20  permits communication between external components (not shown) of the sensing system, and internal components, such as coils and internal sensors (not shown), as will be discussed in detail. Furthermore, the interface  20  itself may include one or more sensory components. This interface  20  may be inset, so that it does not protrude beyond the housing  2 . Mounting of the interface  20  in such an inset fashion protects it from damage and external elements. Furthermore, if a larger interface  20  is needed, it may protrude beyond the external housing. One or more wires (shown at  6  in  FIG. 2 ) may connect to or through the interface  20 . 
     FIG. 3   b  shows a PCAD with the interface  20  removed. One or more seals  26 , if present, are visible through the unobstructed port  4 . One or more holes  24  may be disposed in the one or more seals  26 , for connection of the interface  20 . The seals  26  may comprise magnetic or non-magnetic materials, and may be stacked, as will be described in detail with regard to FIG.  5 . 
     FIG. 4  is a top-down perspective of an embodiment of a PCAD. In the embodiment of  FIG. 4 , the housing  2  is circular in shape; however, other shapes may also be desired and implemented in various embodiments of the invention. An inner passage  12  is located within the housing  2 . Anomalies of a tube (not shown) or other structures passing through this inner passage  12  may be detected by one or more sensory components (not shown) disposed within the PCAD. An isolation sleeve  10  may be disposed between the housing  2  and inner passage  12 . The isolation sleeve  10  shown has a circular cross-section, however, the shape of the sleeve may vary depending on various considerations, such as the shape of the housing  2 . The isolation sleeve  10  may be plastic, or any other suitable material. It may be desirable that the material of the isolation sleeve  10  be non-conductive in order to minimize interference with the detection ability of the PCAD. 
   Also, disposed between the housing  2  and inner passage  12  and within the inner sleeve  12  if present, will be a pressure containing region (“PCR”)  40 . This PCR  40  may include one or more seals, a longitudinal sleeve, or other elements used in the art for containment of pressure within a defined space. In one or more embodiments, an isolation sleeve  10  is disposed between the PCR  40  and housing  2 . If the PCR  40  comprises a plurality of seals, these seals may be stacked within the housing as demonstrated in FIG.  5 . 
   In the embodiment of  FIG. 5 , a series of stacked seals  26  disposed within the PCR  40 , form a barrier surrounding the inner passage  12 . The interior surface of the seals  26  forms the inner passage  12 , while the exterior surface of the seals  26  may be surrounded by an isolation sleeve  10 . Between each seal  26  and the next, a gasket  50  is disposed to contain the pressure within the inner passage. Gaskets  50  may comprise any material commonly used in the art. In one or more embodiments, the gaskets  50  comprise a metal. The stack of seals  26  may extend beyond the upper and lower ends of the housing  2 . Such a configuration allows the stack to be compressed when the housing  2  is fastened between various other components including BOPs, spools, adapters, tubes, pipes and spacers, such as may be used in oilfield applications. 
   The seals  26  may be of any magnetic or non-magnetic substance known in the art. In one embodiment, adjacent seals  26  within the stack will alternate between magnetic and non-magnetic composition. Certain of the seals  26  may be adapted to connect to the interface  20 , by means of connecting members  52 . Such adaptation may include holes for attachment by means of bolts, or similar connectors. However, the connecting members  52  may be of any type commonly used in the art. Connecting members  52  may also play a secondary role, such as the conduction of current to and from seals  26  and/or sensors. 
   Each seal  26  in a stack may be formed of discreet subparts, for instance an inner ring (not shown) proximal the inner passage  12  and an outer ring (not shown). Furthermore, seals  26  or the rings forming the seals  26  may comprise or contain coils or other components of a detection system. For instance, if induction balance technology is used in the sensor system, the outer ring of a seal  26  may comprise a transmitter coil while the inner ring comprises a receiver coil. However, the seals  26  and other components of the PCAD may be adapted for any type of sensor technology known in the art, including, but not limited to, pulse induction and beat-frequency oscillation technologies, as well as non-electrical or non-magnetic systems. 
   In one embodiment of a PCAD, entry of a tool collar, or other anomaly into the inner passage of the device will be detected by a sensory component nearest the anomaly and a signal will be transmitted to an indicator. As the anomaly nears the sensor, a stronger signal will be transmitted to the indicator. The use of various sensory components and configurations will allow for increased accuracy and directional detection. Such components may be of any type known in the art. Because a PCAD creates a protected environment for the disposition of sensory components, more sensitive components may be used. 
   In one embodiment of the PCAD, shown in  FIG. 6 , a tubular member  60  may be disposed between the inner passage  12  and the housing  2 . In one or more embodiments, the tubular member  60  is non-magnetic. A recess  62  may be formed in the tubular member  60 . A coil (not shown) or other sensory component may be disposed at least partially within this recess  62 . Alternatively, a coil (not shown) or other sensory component may be integrated into the tubular member  60  itself. Interior and exterior walls of the tubular member may be configured in any fashion based on the need to accommodate sensory components, and other considerations, including manufacturing costs. Furthermore, the tubular member  60  may contain spaces or hollows (not shown) in order to accommodate sensory components, or lower manufacturing costs. The tubular member  60  may extend beyond the top or bottom of the housing  2 , in such fashion that it will be compressed by other components (not shown) attached to the housing  2 . 
   As shown in the embodiment of  FIG. 7 , the recess  62  may also be formed in the housing  2 , either alone, or in combination with a recess  62  in the tubular insert ( 60  in  FIG. 6 ) or a recess  62  formed in a series of stacked sections  70 . Any number of sections  70  may be used to form the stack. Furthermore, metal gaskets  50  may be disposed between the stacked sections  70 , ensuring the pressure containing integrity of the stack. In one or more embodiments, the sections  70  are non-magnetic, however, sections  70  may comprise any material known in the art. In an alternative embodiment, adjacent sections  70  may have differing compositions. Sections  70  may contain internal spaces or hollows (not shown) in order to lower manufacturing costs, or provide for the disposition of sensory or other components of the PCAD. 
   Although the invention has been described with reference to oilfield applications, such an apparatus may be used in any field where it is desirable to detect the presence, position, or movement of an anomaly within a longitudinal space. The protective advantages of the housing  2 , and PCR  40 , although useful in oilfield and similar applications where it is necessary to contain pressure within the housing  2 , may be similarly useful in applications where it is necessary to prevent the entry of external materials into a controlled environment existing within the housing  2 . 
   Advantages of embodiments of the present invention may include one or more of the following. Embodiments of the present invention provide the ability to use more sensitive detection components and protect them from damaging conditions. Embodiments of the present invention provide the ability to operate in a sub-sea or other harsh environments. The sensitivity of anomaly detection can be increased because sensory components may be mounted closer to the path of an anomaly. Ease of repair or replacement is increased for the few elements that are exposed to the environment (e.g., the wires or interface). Embodiments of the invention may also provide a more economical approach to anomaly detection because standard materials may be used in construction of the housing while the more expensive, non-conductive structural compositions can be limited to internal structures. 
   While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Technology Classification (CPC): 4