Abstract:
A system for sensing a pipe joint within a well structure bore comprises a body connectable in line with the well structure. The body has a central bore therethrough and includes a plurality of blind bores extending radially inwards from the outer surface. The system further includes at least one sleeve being locatable within one of the plurality of blind bores wherein each of the sleeves has a magnet located at an end thereof at least one sensor being locatable within one of the at least one sleeves. The at least one sensor is operable to output a signal representing the width of a metallic object located within the central bore. The system may further include a display operable to receive the output signal from the at least one sensor and to display an output to a user indicating the width of the metallic object within the central bore.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates to well boring in general and in particular to a method and apparatus for sensing a pipe joint within a well structure. 
         [0003]    2. Description of Related Art 
         [0004]    In hydrocarbon production, a well may be formed by an outer casing located within a wellbore and may optionally be surrounded by cement. The well may then include a tool or production string therein for working or producing from the well. Due to the potentially high pressures within the well from hydrocarbons extracted from the hydrocarbon producing formation, numerous types of shut-off valves, spools and other fittings to isolate and control access to the well, such as, by way of non-limiting example a Christmas tree, as it is commonly known or a snubbing rig. 
         [0005]    The well structure may include shut-off valves for closing off or otherwise completely or partially sealing the top of the well as desired by a user. In particular, one common design for such valves are pipe rams which utilize a pair of opposed rams which are movable along a plane perpendicular to the well bore. The rams may be moved along the plate by pistons or the like and are operable to be moved out of the central passage of the well or to be pressed together to seal the well. Rams may be of a blind or shear type to completely seal the well or of a pipe ram type in which the two rams each include a half-circle hole sized to pass a pipe therethrough when the two rams are pressed together. Such pipe rams are commonly utilized in snubbing rigs to seal around the drill or production string and isolate the well below the pipe ram from the environment while permitting the drill or production string to remain within the well or to be extracted or inserted into the well. 
         [0006]    One difficulty that exists with common hydrocarbon wells is the difficulty of determining the location of the joints on the tool or production string. Such strings are commonly formed of a plurality of endwise connected pipes which are connected to each other by threaded connectors. Conventionally such threaded connectors are located at each end and provide enlarged portions of the pipe which are strengthened so as to provide a larger stronger section of the pipe to be grasped by tools and the like. Such tool joints present a larger cross-section than the remainder of the pipe. Disadvantageously, such enlarged diameters of tool joints may interfere with the proper operation of pipe rams should the pipe ram be attempted to be closed at the location of such a tool joint or when extracting or inserting the pipe when at least one of the rams is set to hold back the pressure. Such an event is commonly referred to as stripping which may create a risk of the tool joint being pulled or pushed into the closed piper ram thereby damaging the pipe and/or pipe ram. 
       SUMMARY OF THE INVENTION 
       [0007]    According to a first embodiment of the present invention there is disclosed a system for sensing a pipe joint within a well structure bore. The system comprises a body connectable in line with the well structure. The body has a central bore therethrough along a central axis corresponding to a central bore of the well structure and an outer surface. The body includes a plurality of blind bores extending radially inwards from the outer surface. The system further includes at least one sleeve being locatable within one of the plurality of blind bores wherein each of the sleeves has a magnet located at an end thereof at least one sensor being locatable within one of the at least one sleeves. The at least one sensor is operable to output a signal representing the width of a metallic object located within the central bore. 
         [0008]    The at least one sleeve may be formed of a ferromagnetic material. The body may comprise a spool. The spool may include a plurality of connection bores extending through the spool parallel to the central axis. The blind bores may be located between the connection bores. The spool may be formed of a substantially non-magnetic alloy. The spool may be formed of a nickel-chromium based alloy. 
         [0009]    Each of the at least one sensors may comprise a hall effects sensor. At least one pair of blind bores may be connected to each other by a bridging bar. A first pair the blind bores may be located on opposite sides of the body. A second pair of blind bores may be located to one side of the first pair. The bridging bar may comprise a tubular member extending between the sleeves of the at least one pair of blind bores. The bridging bar may comprise a solid member extending between the sleeves of the at least one pair of blind bores. The bridging bar may be formed of a ferromagnetic material. 
         [0010]    The system may further comprise a display operable to receive the output signal from the at least one sensor and to display an output to a user indicating the width of the metallic object within the central bore. 
         [0011]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    In drawings which illustrate embodiments of the invention wherein similar characters of reference denote corresponding parts in each view, 
           [0013]      FIG. 1  is a cross-sectional view of a the top end of a wellbore having an outer casing and a production string located therein with an apparatus for sensing the location of a pipe joint. 
           [0014]      FIG. 2  is a perspective view of the apparatus for sensing the location of a pipe joint according to a first embodiment of the present invention. 
           [0015]      FIG. 3  is an exploded view of an apparatus for sensing the location of a pipe joint according to a first embodiment of the present invention. 
           [0016]      FIG. 4  is a cross-sectional view of the apparatus of  FIG. 3  as taken along the line  4 - 4 . 
           [0017]      FIG. 5  is a cross-sectional view of the apparatus of  FIG. 3  as taken along the line  5 - 5 . 
           [0018]      FIG. 6  is an illustration of a display output showing voltage produced by a sensor of the apparatus of  FIG. 3  as a tool joint is passed therepast. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring to  FIG. 1 , a well assembly located within a well bore  8  of a soil formation  6  is illustrated generally at  10 . The well assembly includes a well casing  12  having top flange  14  which is securable to a pipe ram  16  or any other desired well head device. It will be appreciated that the present apparatus may be located at any location within the well, such as, by way of non-limiting example, the casing, snubbing unit, blow out preventer or any other well apparatus. It will also be appreciated that the Although only a single pipe ram is illustrated in  FIG. 1  for the sake of clarity, it will be appreciated that many installations will include more than one well head component. As illustrated in  FIG. 1 , the well assembly includes an apparatus for sensing a pipe joint according to a first embodiment of the invention, shown generally at  20  and one or more top pipe, well component or other equipment  18  located thereabove. A production or tool string  15  is located within the casing and includes a plurality of tool joints  17  therealong. 
         [0020]    The apparatus  20  senses the presence of the tool joint  17  and outputs a signal to a display  80  so as to indicate to a user that the tool joint  17  located within apparatus  20  so as to permit the user to advance the production or tool string  15  within the casing  12  by a predetermined distance so as to avoid having one of the pipe rams  16  or other well head devices engage upon the tool joint. 
         [0021]    With reference to  FIG. 2 , the apparatus  20  comprises a body  22  having a plurality of sensor bores  40  therein each adapted to receive a sleeve and a sensor therein. The body  22  comprises an annular or ring-shaped spool having inner and outer surfaces,  24  and  26 , respectively and extending between top and bottom surfaces,  28  and  30 , respectively. As illustrated in  FIG. 1 , the inner and outer surfaces  24  and  26  are substantially cylindrical about a central axis  32  of the spool  22 . The inner surface  24  defines a central passage  34  extending therethrough which may be sized and shaped to correspond to the interior of the casing  12 . As illustrated in  FIGS. 2 and 4 , the top and bottom surfaces are substantially planar along a plane normal to the axis  32  and may optionally include a seal groove  35  extending annularly therearound for receiving a seal as are commonly known in the art. 
         [0022]    The spool  22  includes a plurality of bolt holes  36  extending therethrough between the top and bottom surfaces  28  and  30  along axis parallel to the central axis  32 . The bolt holes  36  are utilized to pass fasteners, such as bolts  38  as illustrated in  FIG. 1  therethrough to secure the spool inline to the other components of the well assembly  10  according to known methods in the art. 
         [0023]    The spool  22  also includes sensor bores  40  extending thereinto from the outer surface  26 . As illustrated herein, the sensor bores  40  are blind bores extending to a bottom depth within the spool by a distance less than the distance from the outer surface  26  to the inner surface  24 . In such a manner, the sensor bore  40  will maintain a barrier wall, generally indicated at  42  in  FIG. 4  between the sensor bore  40  and the central passage  34  so as to maintain the seal provided by the spool  22 . The barrier wall  42  may have a thickness selected to provide adequate burst strength of the spool according to known methods. Optionally the sensor bore  40  may extend completely through the spool to the inner surface  24 . With reference to  FIG. 5 , the bolt bores  36  may be located at regular intervals around the spool wherein the sensor bores extend through the spool at locations between the bolt bores. As illustrated in  FIG. 5 , the sensor bores  40  may be arranged about the central passage  34  along a common plane normal to the axis  32  of the central passage although other orientations may be useful as well. 
         [0024]    The spool  22  may have any depth between the top and bottom surfaces  28  and  30  as is necessary to accommodate the sensor bores  40 . By way of non-limiting example the spool may have a depth of between 3.5 and 24 inches (89 and 610 mm) with a depth of approximately 4 inches (102 mm) having been found to be particularly useful. Additionally, the spool will be selected to have an inner diameter of the inner surface  24  to correspond to the inner passage of the casing  12  for which it is to be used and an outer surface  26  diameter so as to provide a sufficient depth for the sensor bores  40 . In practice it has been found that an outer diameter of between 4 and 12 inches (102 and 305 mm) larger than the inner diameter has been useful. The spool  22  may be formed of a non-magnetic material, such as, by way of non-limiting example a a nickel-chromium based alloy, such as Inconel® manufactured by Special Metals Corporation. It will also be appreciated that other materials may be useful as well, such as, by way of non-limiting example duplex and super duplex stainless steels provided they do not interfere with the sensor operation as described below. 
         [0025]    With reference to  FIG. 3 , an exploded view of the apparatus is illustrated having sleeves  50  locatable within each of the sensor bores and sensors  70  locatable within the sleeves  50 . The sleeves  50  comprise tubular members extending between first and second ends,  52  and  54 , respectively, and having inner and outer surfaces,  56  and  58 , respectively. As illustrated in  FIG. 4 , the outer surface  58  of the sleeves are selected to correspond closely to the sensor bores  40  in the spool  22 . The sleeves  50  are formed of a substantially ferromagnetic material, such as steel so as to conduct magnetic flux as will be more fully described below. The sleeves  50  are selected to have a sufficient outer diameter be received within the sensor bores  40  and an inner surface diameter sufficient to accommodate a sensor  70  therein. By way of non-limiting example it has been found that a diameter of the inner surface of between 0.5 and 1 inches (13 and 25 mm) has been useful. The sleeve  50  may also have a length sufficient to receive the sensor  70  therein, such as by way of non-limiting example, between 0.5 and 3 inches (13 and 76 mm). The outer diameter of the sleeve  50  may also optionally be selected to permit the sleeve to be secured within the sensor bore by means of an interference fit or with the use of adhesives, fasteners, plugs or the like. The sleeve  50  may also be selected to have an outer diameter of sufficient size to have an interference fit with the sensor bore  40 . 
         [0026]    The sleeves  50  also include a magnet  60  located at the first end  52  thereof. The magnets  60  are selected to have strong magnetic fields. In particular, it has been found that rare earth magnets, such as, by way of non-limiting example, neodymium, or samarium-cobalt. Optionally, the magnets  60  may also be nickel plated. The magnets  60  are located at the first ends  52  of the sleeves  50  and retained in place by the magnetic strength of the magnets. Optionally, the sleeve  50  may include an air gap  51  between the magnet  60  and the barrier wall  42  of up to ½ inch (13 mm) although other distances may be useful as well. 
         [0027]    The sensors  70  are inserted into the open second ends  54  of the sleeves and are retained within the sleeves by any suitable means, such as, by way of non-limiting example, adhesives, threading, fasteners or the like. The sensors  70  are selected to provide an output signal in response to the magnetic field in their proximity. By way of non-limiting example, the sensors  70  may comprise magnetic sensors, such as hall effect sensors although it will be appreciated that other sensor types may be utilized as well. As illustrated in  FIG. 4 , the sensor may be located substantially at a midpoint of the sleeves  50  although it will be appreciated that other locations within the sleeve may be useful as well. The sensor includes an output wires  62  extending therefrom. The output wire  62  is wired or otherwise connected to the display and is therefore operable to provide an output signal representing the width of a metallic object located within the central passage  34  such as the drill string. 
         [0028]    With reference to  FIG. 6 , the output  70  may display the voltage signal outputted by the one or more sensors against time. During a first time period, the voltage signal will be at a first level, generally indicated at  84 , while a main portion of the pipe is drawn through the spool  22 . As the tool joint  17  is drawn through the spool  22 , the voltage output of the sensors  70  will be increased, generally indicated at  86 , due to the increased diameter of the metallic object within the central passage  34 . After the tool joint  17  passes the spool, the voltage will return to a lower level  88 . In such a manner, the display  80  will indicate to an operator when the tool joint  17  is located within the sleeve. Thereafter, the operator will be able to advance the production or tool string  15  by a known distance so as to ensure that the pipe rams  16  or other equipment avoids the tool joint  17 . 
         [0029]    With reference to  FIG. 2 , the apparatus may be provided with a bridging bars  90  extending between a pair of opposed sleeves  50 . The bridging bars  90  may be formed of a substantially ferromagnetic material and is adapted to be secured within the sensor bores  40 . The bridging bars  90  may be solid or hollow and are operably connected to the sleeves  50  within the sensor bores  40 . The bridging bars  90  serves to link the magnets and sensors on opposed sides of the spool  22  thereby increasing the field observed. As illustrated in  FIG. 2 , the apparatus may include a central bridging bar  90   a  extending between sensor bores  40  on opposed sides of the spool  22  and a pair of side bridging bars  90   b  extending between a pair of sensor bores  40  located to one side of the central bridging bar  90   a.  It will be appreciated that other arrangements may be useful as well, such as excluding the side or central bridging bars. 
         [0030]    While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.