Abstract:
A wireless coiled tubing joint locator for locating joints or collars in a production tubing string. The joint locator is adapted for running into a well on coiled tubing, and other downhole tools may be connectable to the joint locator. An electromagnetic coil assembly senses the increased mass of a pipe joint, and provides a signal to an electric circuit which generates a momentary electric output signal received by a pilot solenoid valve. The solenoid valve momentarily opens a pilot passageway which activates a piston to close a circulation port in the joint locator. This closing of the circulation point results in an increase in a surface pressure reading observable by the operator. A rupture disk is provided so that pressure cannot be applied to any downhole tool below the joint locator prematurely, and a seat sleeve is provided to prevent premature communication of fluid to the rupture disk but can be opened at any time by dropping a ball into the joint locator. The electronic circuit can be configured to provide a selected one of a plurality of time delays. A fixed test period is also provided in the circuit which delays activation of the time delay so that the joint locator may be tested before it is run into the well. The electric circuit and power supply are provided in a removable case for easy replacement and reconfiguration.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to subterranean pipe string joint locators, and more particularly, to a joint locator for positioning on a well tool connected to coiled tubing in a well and which has a pressure differential actuated piston controlled by a pilot solenoid valve. 
     2. Description of the Prior Art 
     In the drilling and completion of oil and gas wells, a wellbore is drilled into the subterranean producing formation or zone of interest. A string of pipe, e.g., casing, is typically then cemented in the wellbore, and a string of additional pipe, known as production tubing, for conducting produced fluids out of the wellbore is disposed within the cemented string of pipe. The subterranean strings of pipe are each comprised of a plurality of pipe sections which are threadedly joined together. The pipe joints, also often referred to as collars, are of an increased mass as compared to other portions of the pipe sections. 
     It is often necessary to precisely locate one or more of the pipe joints of the casing, a liner or the production tubing in the well. This need arises, for example, when it is necessary to precisely locate a well tool, such as a packer, within one of the pipe strings in the wellbore. The well tool is typically lowered into the pipe string on a length of coiled tubing, and the depth of a particular pipe joint adjacent to or near the location to which the tool is positioned can be readily found on a previously recorded casing joint or collar log for the well. That is, after open hole logs have been run in a drilled wellbore and one or more pipe strings have been cemented therein, an additional log is typically run within the pipe strings. The logging tools used include a pipe joint locator whereby the depths of each of the pipe joints through which the logging tools are passed is recorded. The logging tools generally also include a gamma ray logging device which records the depths and the levels of naturally occurring gamma rays that are emitted from various well formations. The additional log is correlated with the previous open hole logs which result in a very accurate record of the depths of the pipe joints across the subterranean zones of interest referred to as the casing joint or collar log. 
     Given this readily available pipe joint depth information, it would seem to be a straightforward task to simply lower the well tool connected to a length of coiled tubing into the pipe string while measuring the length of coiled tubing in the pipe string by means of a conventional surface coiled tubing measuring device until the measuring device reading equals the depth of the desired well tool location as indicated on the joint and tally log. However, no matter how accurate the coiled tubing surface measuring device is, true depth measurement is flawed due to effects such as coiled tubing stretch, elongation from thermal effects, sinusoidal and helical buckling, and a variety of often unpredictable deformations in the length of coiled tubing suspended in the wellbore. 
     Attempts have been made to more accurately control the depth of well tools connected to coiled tubing. For example, a production tubing end locator has been utilized attached at the end of the coiled tubing. The production tubing end locator tool usually consists of collets or heavy bow strings that spring outwardly when the tool is lowered beyond the end of the production tubing string. When the coiled tubing is raised and the tool is pulled back into the production tubing string, a drag force is generated by the collets or bow springs that is registered by a weight indicator at the surface. 
     The use of such production tubing string end locator tools involve a number of problems. The most common problem is that not all wells include production tubing strings and only have casing or are produced open hole. Thus, in those wells there is no production tubing string on which the tool can catch while moving upwardly. Another problem associated with the lower end of the production tubing string as a locator point is that the tubing end may not be accurately located with respect to the producing zone. Tubing section lengths are tallied as they are run in the well and mathematical or length measurement errors are common. Even when the tubing sections are measured and tallied accurately, the joint and tally log can be inaccurate with respect to where the end of the tubing string is relative to the zone of interest. Yet another problem in the use of production tubing in locator tools is that a different sized tool must be used for different sizes of tubing. Further, in deviated or deep wells, the small weight increase as a result of the drag produced by the end locator tool is not enough to be noticeable at the surface. 
     While a variety of other types of pipe string joint indicators have been developed including slick line indicators that produce a drag inside the tubing string, wireline indicators that send an electronic signal to the surface by way of electric cable and others, they either cannot be utilized as a component in a coiled tubing well tool system or have disadvantages when so used. One improved coiled tubing joint locator tool and methods of using the tool are disclosed in U.S. Pat. No. 5,626,192, assigned to the assignee of the present invention. This tubing joint locator does not require the use of electric cable and overcomes other shortcomings of earlier prior art. This joint locator has a longitudinal fluid flow passageway therethrough so that fluid can be flowed through the coiled tubing and the joint indicator and has at least one lateral port extending through a side thereof which provides communication between the fluid flow passageway and the well annulus outside the tool. An electronic means detects the increased mass of a pipe joint as the locator is moved through the pipe joint and generates a momentary electric output signal in response thereto. A valve means is actuated in response to the electric output signal to momentarily open or close the lateral port which creates a surface detectable pressure drop or rise in the fluid flowing through the coiled tubing and the joint locator indicative of the location of the pipe joint. The valve is connected to the solenoid and is mechanically directly opened or closed thereby. 
     In some cases, the output of the solenoid may be insufficient to overcome the friction of the sleeve particularly with smaller tools with size restrictions. The present invention solves this problem by using a pilot operated solenoid valve which communicates fluid pressure to a piston such that the pressure differential inside the tool and outside the tool moves the piston to close a normally open circulating port. The pilot operated solenoid valve decreases the stroke necessary for the solenoid valve and further reduces the power requirements proportionally. 
     Another potential problem with the apparatus shown in U.S. Pat. No. 5,626,192 is the pressure spike caused by closing the circulation port might interfere with or cause premature operation of pressure sensitive tools which are located in the tubing string below the coiled tubing joint locator. The present invention solves this problem by providing a rupture disk which opens only at a predetermined pressure, and pressure can only be communicated to the rupture disk after circulating a ball through the tubing string and applying sufficient pressure to actuate a sliding sleeve. 
     The present invention also includes the improvement to the apparatus shown in U.S. Pat. No. 5,626,192 of incorporating a selection of time delays in the electric means which prevents the solenoid valve from being actuated before it is desired. This reduces the power drain on the batteries as the tool is run into the well until the desired depth of the tool has been reached. The circuitry provides a fixed test period prior to activation of the time delay which allows the tool to be functionally checked before it is run into the well. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved coiled tubing joint locator which allows fluid flow therethrough and does not require an electrical connection with the surface. It has a modular configuration which allows easy replacement and rearrangement of the major components. 
     The joint locator comprises a housing having an upper end adapted for connection to a length of coiled tubing whereby the locator may be moved within the pipe string in response to movement of the coiled tubing, the housing defining a central opening therethrough and a normally open transverse circulation port in communication with a central opening. The circulation port is formed in a nozzle which is one of a plurality of interchangeable nozzles. The joint locator further comprises a valve disposed in the housing for momentarily closing the circulation port in response to a pressure differential between the coiled tubing and a well annulus outside the circulation port, and an electronic means disposed in the housing for detecting an increased mass of a pipe joint and generating a momentary electric output signal in response thereto, thereby placing the valve in communication with the pressure in the coiled tubing in response to the signal. The valve is preferably a solenoid valve, and the electronic means preferably comprises a pilot solenoid in the valve which opens in response to the signal and places the valve in communication with the pressure in the coiled tubing. The housing defines a pilot passageway therein in communication with an upper portion of the valve and an annulus or vent port in communication with a lower portion of the valve. The solenoid is adapted to open the pilot passageway in response to the signal. 
     The electronic means preferably also comprises an electromagnetic coil assembly, including a coil and magnet, for electromagnetically sensing the increased mass of the pipe joint. The electronic means further comprises an electric power source and electric circuit means for generating a signal when the coil electromagnetically senses the increased mass. The electronic circuit means has a time delay circuit with a preselectable time delay therein which prevents premature draining of the electric power source. The time delay circuit includes a test time period which allows testing of the joint locator at the surface prior to initiation of the time delay. The power source and electric circuit means are preferably disposed in an electric case which is removable from the housing. This case is preferably threadingly connected to an upper end of the housing. 
     The joint locator also comprises pressure isolation means for preventing premature communication between the pressure in the coiled tubing and a bottom portion of the housing below the communication port. This pressure isolation means may comprise a rupture disk. The pressure isolation means also comprises in the preferred embodiment a valve having a seat thereon and a flow passageway therethrough and a ball engagable with the seat after the ball is circulated down through the coiled tubing string into the joint locator. The valve has a closed position wherein flow through the passageway is prevented and an open position wherein flow through the passageway is allowed. When the ball is engaged with the seat, fluid communication through the circulation port is prevented, and when a predetermined pressure is applied to the valve and ball, the valve is moved from the closed position to the open position thereof. The valve comprises a seat body fixedly disposed in the housing and forming a lower portion of the flow passageway, and a seat sleeve slidably disposed in the seat body and forming an upper portion of the flow passageway. The upper portion of the passageway is in communication with the lower portion of the passageway when the valve is in the open position thereof. The valve further comprises shear means for initially shearably holding the seat sleeve in the closed position thereof. 
     Stated another way, the joint locator is an apparatus for locating joints in a well pipe string comprising a housing having an upper end connectable to a length of coil tubing and defining a central opening therethrough and a transfer circulation port in communication with the central housing, and an electronic assembly disposed in the housing. The electronic assembly comprises a sensing means for detecting an increased mass of a pipe joint, and an electric module comprising a power source and an electric circuit connected thereto and to the sensing means. The electronic circuit generates a momentary electric output signal in response to the detection of the increased mass by the sensing means, and the electric module is removable as an integral unit from the housing. The apparatus further comprises valve means disposed in the housing for momentarily closing the circulating port in response to the electric output signal. 
    
    
     Numerous objects and advantages of the invention will become apparent to those skilled in the art when the following detailed description of the preferred embodiment is read in conjunction with the drawings which illustrate such embodiment. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a cased well having a string of production tubing disposed therein and having a length of coiled tubing with the wireless coiled tubing collar or joint locator of the present invention connected thereto and inserted into the well by a coiled tubing injector and truck mounted reel. 
     FIGS. 2A-2F show a longitudinal cross section of the coiled tubing joint locator. 
     FIG. 3 is a cross section taken along lines  3 - 3  in FIG.  2 C. 
     FIGS. 4A and 4B show a wiring schematic showing the control circuitry used in the joint locator. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     After a well has been drilled, completed and placed in production, it is often necessary to service the well whereby procedures are performed therein such as perforating, setting plugs, setting cement retainers, spotting permanent packers and the like. Such procedures are often carried out by utilizing coiled tubing. Coiled tubing is a relatively small flexible tubing, usually one to two inches in diameter, which can be stored on a reel when not being used. When used for performing well procedures, the tubing is passed through an injector mechanism, and a well tool is connected to the end thereof. The injector mechanism pulls the tubing from the reel, straightens the tubing and injects it through a seal assembly at the wellhead, often referred to as a stuffing box. Typically, the injector mechanism injects thousands of feet of the coiled tubing with the well tool connected at the bottom end thereof into the casing string or the production tubing string of the well. A fluid, most often a liquid such as salt water, brine or a hydrocarbon liquid, is circulated through the coiled tubing for operating the well tool or other purpose. The coiled tubing injector at the surface is used to raise and lower the coiled tubing and the well tool during the service procedure and to remove the coiled tubing and well tool as the tubing is rewound on the reel at the end of the procedure. 
     Referring now to FIG. 1, a well  10  is schematically illustrated along with a coiled tubing injector  12  and a truck mounted coiled tubing reel assembly  14 . Well  10  includes a wellbore  16  having a string of casing  18  cemented therein in the usual manner. A string of production tubing  20  is also shown installed in well  10  within casing string  18 . Production string  20  is made up of a plurality of tubing sections  22  connected by a plurality of joints or collars  24  in a manner known in the art. 
     A length of coiled tubing  26  is shown positioned in production tubing string  20 . The wireless coiled tubing collar or joint locator of the present invention is generally designated by the numeral  28  and is attached to the lower end of coiled tubing  26 . One or more well tools  30  may be attached below joint locator  28 . 
     Coiled tubing  26  is inserted into well  10  by injector  12  through a stuffing box  32  attached to the upper end of tubing string  20 . Stuffing box  32  functions to provide a seal between coiled tubing  26  and production tubing string  20  whereby pressurized fluids within well  10  are prevented from escaping to the atmosphere. A circulating fluid removal conduit  34  having a shutoff valve  36  therein is sealingly connected to the top of casing string  18 . Fluid circulated into well  10  through coiled tubing  26  is removed from the well through conduit  34  and valve  36  and routed to a pit, tank or other fluid accumulator. 
     Coiled tubing injector  12  is of a kind known in the art and functions to straighten coiled tubing  26  and inject it into well  10  through stuffing box  32  as previously mentioned. Coiled tubing injector  12  comprises a straightening mechanism  38  having a plurality of internal guide rollers  40  therein and a coiled tubing drive mechanism  42  which is used for inserting coiled tubing  26  into well  10 , raising the coiled tubing or lowering it within the well, and removing the coiled tubing from the well as it is rewound on reel assembly  14 . A depth measuring device  44  is connected to drive mechanism  42  and functions to continuously measure the length of coiled tubing  26  within well  10  and provide that information to an electronic data acquisition system  46  which is part of reel assembly  14  through an electric transducer (not shown) and an electric cable  48 . 
     Truck mounted reel assembly  14  includes a reel  50  on which coiled tubing  26  is wound. A guide wheel  52  is provided for guiding coiled tubing  26  on and off reel  50 . A conduit assembly  54  is connected to the end of coiled tubing  26  on reel  50  by a swivel system (not shown). A shut-off valve  56  is disposed in conduit assembly  54 , and the conduit assembly is connected to a fluid pump (not shown) which pumps fluid to be circulated from the pit, tank or other fluid communicator through the conduit assembly and into coiled tubing  26 . A fluid pressure sensing device and transducer  58  is connected to conduit assembly  54  by connection  60 , and the pressure sensing device is connected to data acquisition system  46  by an electric cable  62 . As will be understood by those skilled in the art, data acquisition system  46  functions to continuously record the depth of coiled tubing  26  and joint locator  28  attached thereto in the well  10  and also to record the surface pressure of fluid being pumped through the coiled tubing and joint locator as will be further described herein. 
     Referring now to FIGS. 2A-2F, the details of joint locator  28  will be discussed. An outer housing  64  contains the other components of joint locator  28 . At the upper end of outer housing  64  is a top sub  66  having a cylindrical first outer surface  68  which extends into a bore  70  of a makeup ring  72 . A sealing means, such as a plurality of O-rings  74  provide sealing engagement between top sub  66  and makeup ring  72 . Top sub  66  defines a plurality of radially extending cylindrical recesses  76 . A plurality of set screws  78  are threadingly engaged with makeup ring  72  and extend into corresponding recesses  76  to lock top sub  66  and makeup ring  72  together. 
     Outer housing  64  also comprises an upper housing  80  attached to makeup ring  72  by threaded connection  82 . A sealing means, such as a pair of O-rings  84 , provide sealing engagement between upper housing  80  and makeup ring  72 . 
     Referring to FIG. 2C, the lower end of upper housing  80  is attached to a middle sub  86  at threaded connection  88 . A sealing means, such as a pair of O-rings  90 , provide sealing engagement between upper housing  80  and middle sub  86 . 
     As seen in FIG. 2D, the lower end of middle sub  86  is attached to a coil housing  92  at threaded connection  94 . A sealing means, such as a pair of O-rings  96 , provide sealing engagement between middle sub  86  and coil housing  92 . It will be seen that coil housing  92  forms another portion of outer housing  64 . 
     Outer housing  64  also includes a valve housing top sub  98  of a valve housing  100  which is connected to the lower end of coil housing  92  at threaded connection  102 , as seen in FIG.  2 E. Referring also to FIG. 2D, a sealing means, such as a pair of O-rings  104 , provide sealing engagement between coil housing  92  and valve housing top sub  98 . 
     Outer housing  64  also includes a middle housing  106  attached to the lower end of valve housing top sub  98  at threaded connection  108 . 
     Referring now to FIG. 2F, the lower end of middle housing  106  is attached to a bottom housing  110 , also forming a portion of outer housing  64 , at threaded connection  112 . 
     Bottom housing  110  is connected to a circulating sub  114  at threaded connection  116 . 
     At the bottom of outer housing  64 , a bottom sub  118  is attached to circulating sub  114  at threaded connection  120 . A sealing means, such as a pair of O-rings  122 , provides sealing engagement between circulating sub  114  and bottom sub  118 . 
     Referring again to FIG. 2A, top sub  66  defines a threaded opening  124  therein adapted for connection to coiled tubing  26 . Top sub  66  also defines a longitudinal bore  126  therethrough. An annular groove  128  is defined in first outer surface  68  of top sub  66 . 
     A second outer surface  130  on the lower end of top sub  66  extends into a bore  132  in a printed circuit board (PCB) chassis  134 . PCB chassis  134  defines a window  136  therein. An electric circuit means, such as a printed circuit board (PCB)  138 , is disposed in window  136  and is attached to surface  140  which extends longitudinally in PCs chassis  134  adjacent to window  136 . A screw  141  is used to attach PCB chassis  134  to top sub  66 . Screw  141  is off-center with respect to top sub  66 . 
     A split ring assembly  142  is disposed in groove  128  in top sub  66 . Split ring assembly  142  comprises a pair of split ring halves  144  and  146  with a retaining means, such as an O-ring  148 , to hold the halves in groove  128 . Split ring assembly  142  holds makeup ring  72  in engagement with top sub  66  and prevents longitudinal movement therebetween, while allowing relative rotation therebetween, during assembly of joint locator  28 . That is, makeup ring  72  may be rotated with respect to top sub  66  to form threaded connection  82  between the makeup ring and upper housing  80  without requiring rotation of top sub  66  or PCB chassis  134 . After threaded connection  82  has been made up, set screws  78  are installed as previously described to lock top sub  66  and makeup ring  72  together so that the makeup ring cannot be rotated to disengage threaded connection  82 . 
     The upper end of a top flow tube  150  is disposed in bore  126  in top sub  66 . A sealing means, such as a pair of O-rings  152 , provide sealing engagement between top sub  66  and top flow tube  150 . Top flow tube  150  extends downwardly through upper housing  80 , middle sub  86  and coil housing  92  of outer housing  64 , as seen in FIGS. 2A-2D. 
     A top support collar  154  extends into a bore  156  at the lower end of PCB chassis  134 . A plurality of screws  158  are used to attach top support collar  154  to PCB chassis  134 . 
     An annular upper end cap  160  is spaced from top support collar  154  by a plurality of non-threaded standoffs  162 . A plurality of screws  163  extend through standoffs  162  and are used to attach top support collar  154  to upper end cap  160 . Upper end cap  160  has a plurality of openings  164  defined therein. Preferably, but not by way of limitation, there are four such openings  164  which are angularly spaced around upper end cap  160 . 
     An upper spring housing  166  is disposed below and adjacent to upper end cap  160 . Upper spring housing  166  defines a plurality of openings  167  therein which are aligned with openings  164  in upper end cap  160 . 
     Disposed below upper spring housing  166  is a battery pack housing  170  defining a plurality of battery chambers  172  therein. Battery chambers  172  are aligned with corresponding openings  167  in upper spring housing  166  and openings  164  in upper end cap  160 . An electric power source, such as a plurality of batteries  174 , is disposed in each battery chamber  172 . In the preferred embodiment, but not by way of limitation, there are four battery chambers  172  with eight batteries  174  each of which are AA size batteries. 
     A plurality of screws  171  connect upper spring housing  166  to battery pack housing  170 . 
     An upper plunger  176  is disposed in each opening  167  in upper spring housing  166 . Each upper plunger  174  is biased downwardly against an uppermost battery  174  by an upper spring  178  which is also engaged with an upper contact screw  180  disposed in each opening  164  of upper end cap  160 . Another screw  182  connects upper contact screw  180  to a wire  183  which is connected to PCB  138 . 
     Referring now to FIG. 2C, a plurality of screws  184  attach a lower spring housing  186  to the lower end of battery pack housing  170 . Lower spring housing  186  defines a plurality of openings  188  therein which are aligned with corresponding battery chambers  172  in battery pack housing  170 . A lower plunger  190  is slidably disposed in each opening  188  in lower spring housing  186 . Each lower plunger  190  is biased upwardly against the lowermost battery  172  by a lower spring  192 . 
     Lower spring  192  also engages a lower contact screw  194  positioned in an opening  195  defined in a lower end cap  196 . Lower end cap  196  is adjacent to lower spring housing  186 , and each opening  195  is aligned with a corresponding opening  188  in lower spring housing  186  and battery chamber  172  in battery pack housing  170 . 
     Another screw  197  is used to attach a wire  199  to lower contact screw  194 . Wire  199  is also connected to PCE  138 . 
     A bottom support collar  198  is spaced from lower end cap  196  by a plurality of non-threaded standoffs  200 . A plurality of screws  201  are used to attach bottom support collar  198  to lower end cap  196 . 
     The lower end of bottom support collar  198  extends into the upper end of middle sub  86 . Referring now to FIG. 3, fingers  202  and  203  extend upwardly from middle sub  86  into corresponding slots  204  and  205  in bottom support collar  198 . Fingers  202  and  203  and slots  204  and  205  are different widths to uniquely orient bottom support collar  198  and middle sub  86  with respect to one another, as will be further described herein. 
     PCB chassis  134 , top support collar  154 , upper end cap  160 , upper spring housing  166 , battery pack housing  170 , lower spring housing  186 , lower end cap  196  and bottom support collar  198  form an electric case  206  which houses printed circuit board  138  and batteries  174 . It will be seen that electric case  206 , and the components therein, are easily removed from outer housing  64  by disconnecting top sub  66  and makeup ring  72  and sliding the assembly out over top flow tube  150 . This provides easy battery replacement and facilitates replacement or reconfiguration of printed circuit board  138 . 
     A probe contact insert  208  is disposed in the upper end of middle sub  86  below bottom support collar  198 . A plurality of binderhead screws  209  lock probe contact insert  208  with respect to middle sub  86 . 
     Four probes  210  are disposed through bottom support collar  198  and extend downwardly therefrom. Four probe contact screws  211 , corresponding to probes  210 , are threaded into probe contact insert  208 . Each probe  210  is connected to a wire  213  which is also connected to PCB  138 . Two sets of probes  210 , contact probes  211  and wires  213  provide a connection between PCB  138  and an electromagnetic coil assembly  220 , and another two sets provide a connection between PCB  138  and a solenoid valve  286 , as further described herein. 
     A back cap  212  is disposed adjacent to probe contact insert  208 , and the lower end of probe contact screws  211  extend slightly into back cap  212 . Each probe contact screw  211  is in electrical contact with a wire  214 . Two wires  214  extend down to electromagnetic coil assembly  220 , and two wires  214  extend down toward solenoid valve  286 . 
     Referring also to FIG. 2D, a spring  216  is positioned between back cap  212  and a shoulder  218  in middle sub  86  to provide a biasing means for biasing back cap  212  and probe contact insert  208  upwardly. It will be seen by those skilled in the art that this keeps each probe contact screw  211  in electrical contact with the corresponding probe  210 . Because of the difference in the widths of fingers  202  and  203  on middle sub  86  which engage corresponding slots  204  and  205  in bottom support collar  198 , it will be seen that each probe  210  is aligned and kept in contact with a specifically corresponding probe contact screw  211 . In this way, the proper electrical connection is made between PCB  138  and electromagnetic coil assembly  220  and also with solenoid valve  286 . 
     Electromagnetic coil assembly  220  is positioned in coil housing  92  below middle sub  86 . Electromagnetic coil assembly  220  is of a kind generally known in the art having a coil  217 , magnets  219  and rubber shock absorbers  221  and  223 . 
     As seen in FIGS. 2A-2D, top flow tube  150  extends downwardly through outer housing  64 . Top flow tube  150  has a central opening  225  which forms a portion of a flow passageway  222  in joint locator  28  which extends through PCB chassis  134 , top support collar  154 , upper end cap  160 , upper spring housing  166 , battery pack housing  180 , lower spring housing  186 , lower end cap  196 , bottom support collar  198 , probe contact insert  208 , back cap  212 , middle sub  86  and electromagnetic coil assembly  220 . 
     The lower end of top flow tube  150  is attached to a top neck portion  224  of valve housing top sub  98  by threaded connection  226 . A sealing means, such as a pair of O-rings  228 , provides sealing engagement between top flow tube  150  and top neck portion  224 . 
     Top neck portion  224  defines a bore  230  therein which may be referred to as an upper portion  230  of a sub passageway  232  in valve housing top sub  98 . Sub passageway  232  is part of flow passageway  222  and will be seen to be in communication with central opening  221  in top flow tube  150 . In addition to upper portion  230  in top neck portion  224 , sub passageway  232  has an angularly disposed central portion  234 , seen in FIG. 2D, and a longitudinally extending lower portion  236 , seen in FIG.  2 E. Thus, lower portion  236  of sub passageway  232  is off center with respect to upper portion  230  and the central axis of joint locator  28 . 
     A valve housing flow tube  238 , also referred to as a bottom flow tube  238  extends into a bore  240  at the lower end of lower portion  236  of sub passageway  232  in valve housing top sub  98 . A sealing means, such as a pair of O-rings  242 , provides sealing engagement between bottom flow tube  238  and valve housing top sub  98 . The lower end of bottom flow tube  238  extends into a bore  246  in a valve housing bottom sub  244 . A sealing means, such as a pair of O-rings  248 , provides sealing engagement between bottom flow tube  238  and valve housing bottom sub  244 . 
     Referring to FIGS. 2E and 2F, valve housing bottom sub  244  has a sub passageway  250  defined therein which forms part of flow passageway  222 . Sub passageway  250  has a substantially longitudinally extending upper portion  252 ; an angularly disposed central portion  254 , and a substantially longitudinally extending lower portion  256 . Upper portion  252  of sub passageway  250  is offset from the central axis of joint locator  28 , and lower portion  256  is on the central axis. 
     Valve housing bottom sub  244  has a passageway port  258  extending between upper portion  252  of passageway  250  and top surface  260  of the valve housing bottom sub, as seen in FIG.  2 E. Valve housing bottom sub  244  also has a piston port  262  extending between top surface  260  and a downwardly facing shoulder  264  as seen in FIGS. 2E and 2F. 
     A sealing means, such as an O-ring  266 , provides sealing engagement between valve housing bottom sub  244  and bottom housing  110 , as seen in FIG. 2F. A bottom sub split ring assembly  268  having two split ring halves  270  and  272  fits in a groove  274  defined on the outside of valve housing bottom sub  244 . It will be seen by those skilled in the art that split ring assembly  268  thus acts to lock valve housing bottom sub  244  with respect to middle housing  106  when threaded connection  112  is made up. An O-ring  276  holds halves  270  and  272  of split ring  268  in groove  274  during assembly. 
     Referring again to FIGS. 2D and 2E, one of wires  214  is shown extending downwardly through valve housing top sub  98 . Wire  214  is connected to an upper portion  280  of a socket connector  282 . Socket connector  282  also has a lower portion  284  which is connected to pilot solenoid valve  286  by a wire  288 . Another set of wires  214 ,  288  and socket connector  282  (not shown) also connect PCB  138  to solenoid valve  286 . 
     Solenoid valve  286  is disposed in middle housing  106  on top surface  260  of valve housing bottom sub  244 . As will be further described herein, solenoid valve  286 , which is schematically shown in FIG. 2E, is of a kind known in the art having an electric solenoid  286  which actuates a valve portion  289 . Solenoid valve  286  is configured and positioned so that when it is in a closed position, communication between passageway port  258  and piston port  262  in valve housing bottom sub  244  is prevented, and the solenoid valve is vented to the well annulus through a transverse annulus or vent port  290  in middle housing  106 . When solenoid valve  286  is in the open position, passageway port  258  and piston port  262  are placed in communication with one another and the solenoid valve is no longer in communication with vent port  290 . Passageway port  258  and piston port  262  when in communication with one another may be said to form a pilot passageway  258 ,  262 . 
     Below shoulder  264  on valve housing bottom sub  244 , a piston  292  is slidably disposed in bottom housing  110  and circulating sub  114 . Piston  292  has a first outside diameter  294  which fits within a bore  296  in bottom housing  110  and a smaller second outside diameter  298  which fits within first bore  300  in circulating sub  114 . A sealing means, such as O-ring  302 , provides sealing engagement between piston  292  and bottom housing  110 , and another sealing means, such as O-ring  304 , provides sealing engagement between the piston and circulating sub  114 . A biasing means, such as spring  306  is positioned between a downwardly facing shoulder  308  on piston  292  and an upper end  310  of circulating sub  114 . Spring  30  biases piston  292  upwardly toward shoulder  264  on valve housing bottom sub  244 . Spring  306  is thus positioned in a spring chamber  312 , and a transverse port  314  is defined in bottom housing  110  to equalize the pressure between spring chamber  312  and the well annulus outside joint locator  28 . It will be seen by those skilled in the art that well annulus pressure thus is applied to the area of shoulder  308  on piston  292 . 
     It will also be seen that the top of piston  292  is in communication with piston port  262  in valve housing bottom sub  244 . 
     Piston  292  has a central opening  291  defined by a first bore  316  therein and a larger second bore  318 . Central opening  291  is part of flow passageway  222 . A bottom neck portion  320  of valve housing bottom sub  244  extends into first bore  316  of piston  292 . Thus, sub passageway  250  is in communication with central opening  291  of piston  292 . A sealing means, such as an O-ring  321 , provides sealing engagement between piston  292  and bottom neck portion  320 . 
     Circulating sub  114  defines a threaded port  322  extending transversely therein. A nozzle  323  is threaded into port  322  and defines a circulating port  324  therein. Nozzle  323  may be said to be part of outer housing  64  such that circulating port  324  may be said to extend transversely in the outer housing. Nozzle  323  is one of a plurality of interchangeable nozzles with differently sized circulating ports  324 . Thus, circulating port  324  may be said to be variably sized. In the position of piston  292  shown in FIG. 2F, a lower end  326  of the piston is disposed above circulating port  324 . When open, circulating port  324  is an outlet portion of flow passageway  222 . 
     A seat body  328  is disposed in circulating sub  114 . Seat body  328  has first outside diameter  330  sized to fit within first bore  300  of circulating sub  114  and a larger second outside diameter  332  sized to fit within second bore  334  of circulating sub  114 . A sealing means, such as an O-ring  336 , provides sealing engagement between seat body  328  and circulating sub  114 . An upper end  338  of seat body  328  is below circulating port  324 . Thus, an annular volume  340  is defined between lower end  326  of piston  292  and upper end  338  of seat body  328 , and this annular volume is part of flow passageway  222  and is in communication with circulating port  324 . 
     Seat body  328  defines a body passageway  342  on the outside thereof which is in communication with bore  344  in seat body  328  through a transversely extending body port  346 . 
     A seat sleeve  348  is slidably disposed in second bore  318  of piston  292  and bore  344  in seat body  328 . Seat sleeve  348  is initially shearably attached to seat body  328  by a shearing means such as a shear pin  350 . 
     Seat sleeve  348  defines a central opening  352  there-through, forming part of flow passageway  222 , with a chamfered seat  354  at the upper end thereof. A transversely extending port  356 , also part of flow passageway  222 , is defined in seat sleeve  348 . Port  356  provides communication between central opening  352  and annular volume  340  when in the position shown in FIG.  2 F. 
     A sealing means, such as an O-ring  358 , provides sealing engagement between seat sleeve  348  and piston  292  above port  356 , and another sealing means, such as O-ring  360 , is disposed on seat sleeve  348  below port  356 . In the initial position shown in FIG. 2F, O-ring  360  is in communication with annular volume  340 . O-ring  360  is not used for sealing until piston  292  is moved, as will be further described herein. 
     Seat sleeve  348  also defines a plurality of longitudinally extending flow ports  362  therein which are spaced radially outwardly from central opening  352 . The upper ends of flow ports  362  are located in chamfered seat  354 , and the lower ends of the flow ports are in communication with an annular recess  364  defined in the outside of seat sleeve  348 . A sealing means, such as O-ring  366 , provides sealing engagement between seat sleeve  348  and seat body  328  above recess  364 , and another sealing means, such as O-ring  368 , provides sealing engagement between the seat sleeve and seat body below recess  364 . O-ring  368  is disposed above transverse port  346 , and an additional sealing means, such as O-ring  370 , provides sealing engagement between seat sleeve  348  and seat body  328  below port  346  when the seat sleeve is in the position shown in FIG.  2 F. 
     Below seat body  328 , a rupture disk housing  372  is disposed in bottom sub  118 , and a sealing means, such as O-ring  374 , provides sealing engagement between rupture disk housing  372  and bottom sub  118 . A rupture disk  376  is disposed in rupture disk housing  372 . The upper side of rupture disk  376  will be seen to be in communication with body passageway  342  in seat body  328 , and the lower side of rupture disk  376  is in communication with a central opening  378  in bottom sub  118 . 
     Bottom sub  118  has a threaded outer surface  380  adapted for connection to well tool  30  below joint locator  328 . 
     The presently preferred embodiment of joint locator  28  shown in FIGS. 2A-2F has a generally modular construction. Starting with the uppermost, the modules include as major components PCB  138 , battery pack housing  170  and batteries  174 , electromagnetic coil assembly  220 , solenoid valve  286 , seat sleeve  348  and rupture disk  376 , along with the various components associated with each of these main items. It will be understood by those skilled in the art that with minor modifications, these modules and their major components can be rearranged and repositioned as desired. The invention is not intended to be limited to the exact relationship between the modules shown in FIGS. 2A-2F. 
     OPERATION OF THE INVENTION 
     In operation, joint locator  28  is attached to coiled tubing  26  at threaded opening  124  as previously described, and a well tool  30  is connected below joint locator  28 . Coiled tubing  26  is injected into well  10  and may be raised within the well using injector  12  in the known manner with corresponding movement of joint locator  28 . Thus, joint locator  28  may be raised and lowered within production tubing string  20 . As joint locator  28  passes through a pipe joint  24 , electromagnetic coil assembly  220  senses the increased mass of the pipe joint. 
     Referring to FIGS. 4A and 4B, a schematic of an electrical circuit  390  for joint locator  28  is shown and will be understood by those skilled in the art. Most of electrical circuit  390  is on printed circuit board  138 . Power for circuit  390  is provided by batteries  174 , and coil assembly  220  and solenoid valves  286  are also part of the circuit. 
     To minimize the consumption of power, circuit  390  includes a time delay  392 . Any of a variety of time delay periods may be preselected when joint locator  28  is being made up, and the selected time delay period prevents operation of solenoid  286  before the time delay period has lapsed. This prevents unnecessary actuation of solenoid valve  286  as joint locator  28  is moved in tubing string  20  to the desired location. The deeper the joint locator  28  is going to be used in well  10 , the longer the time delay period selected in time delay  392 . Time delay  392  also has a fixed time period before deactivating solenoid valve  286  so that joint locator  28  may be tested after assembly to allow a tool functionality check before the joint locator is lowered into well  10 . Once the fixed test period lapses, time delay  392  activates the preselected time period to prevent actuation of solenoid valve  286  until lapsing of that time delay period. 
     A test time period is also provided in time delay  392  to allow testing of joint locator  28  before the above-described time delay starts. 
     As joint locator  28  passes through a pipe joint  24 , electromagnetic coil assembly  220  electromagnetically senses the increased mass of the pipe joint and provides a signal to circuitry on printed circuit board  138 . That is, a voltage pulse is induced in coil  217  and sent to PCB  138 . This voltage pulse, if sufficiently large in amplitude, signals the PCB circuitry that it is time to provide battery power to solenoid valve  286 . Once battery power is supplied to solenoid valve  286 , valve portion  289  is actuated by electric solenoid  287  to place passageway port  358  in communication with piston port  262  in valve housing bottom sub  244 . In the preferred embodiment, this power is applied to solenoid valve  286  for a period of approximately  2 . 9  seconds which is a function of the resistor and capacitor values of resistor RlS and capacitors C 14 , C 15  and C 16  shown in FIG.  5 . 
     The “Gain Select” circuitry is simply for signal amplification in the event that the voltage induced in coil  217  is too small for detection or too large to discriminate noise from actual casing collars. 
     The “CCL Enable” is a time delay circuit designed to minimize power drain from batteries  174  when running apparatus  10  to logging depth. A time delay may be preselected from a plurality of time delay values during which the battery power will not be applied to solenoid valve  286 . In the preferred embodiment, but not by way of limitation, time delay periods of ten, twenty, forty, eighty or one hundred sixty minutes may be chosen. After this time delay, the power from batteries  174  back to PCB  138  may be at any time supplied to solenoid valve  286  if a sufficiently large voltage pulse from coil  217  is detected as previously described. 
     The “‘On’-By-Flow” circuitry is for an alternate embodiment in which power from batteries  174  may be supplied to solenoid valve  286  only when a minimum flow volume is being pumped at the surface at the time coil  217  detects a collar. 
     Thus, an electronic means is provided for detecting the increased mass of the pipe joint and placing the ports in communication. It will be seen that the actuation of solenoid valve  286  briefly places fluid pressure in the flow passageway  222  through joint locator  28  in communication with the top of piston  292  in bottom housing  110  and circulating sub  114 . Because the pressure in spring chamber  312  is at annulus pressure, the higher internal pressure in flow passageway  222  in joint locator  28  applied to the top of piston  292  forces the piston downwardly such that it acts as a valve means for closing circulating port  324  in circulating sub  114 . This causes a surface detectable pressure increase in the fluid in joint locator  28 , because the fluid may no longer flow through circulating port  324 . When solenoid valve  286  recloses, spring  306  returns piston  292  to its open position, again allowing fluid flow through flow passageway  222  and out circulating port  324 . 
     The operator will know the depth of joint locator  28  and thus be able to determine the depth of the pipe joint just detected. It will be understood by those skilled in the art that joint locator  28  may also be configured such that circulating port  324  is normally closed and the momentary actuation of piston  292  by solenoid valve  286  may be used to open the circulating port. In this configuration, the pipe joint is detected by a surface detectable drop in the fluid pressure. The configurations shown in FIGS. 2A through 2F is preferable when it is desired to circulate fluid while positioning joint locator  28 . 
     This process for detecting the location of pipe joints may be repeated as many times as desired to locate any number of pipe joints  24 . The only real limitation in this procedure is the life of batteries  184 . 
     Rupture disk  376  is provided to prevent communication of fluid pressure to any well tool  30  below joint locator  28  until sufficient pressure has been applied to rupture the rupture disk as will be further described herein. 
     Referring to FIG. 2F, seat sleeve  348  is shown in the initial, run-in position. It will be seen that fluid may be circulated through flow passageway  222  in joint locator  28  and out circulating ports  324  because port  356  in seat sleeve provides communication between circulating port  324  and central opening  352  in the seat sleeve, as previously described. It will also be seen that port  346 , and thus body passageway  342  are closed so that fluid pressure flow passageway  222  cannot be applied to rupture disk  376 . This prevents premature rupturing of rupture disk  376  and the resultant premature actuation of well tool  30 . 
     Once the desired number of pipe joints  24  have been located using joint locator  28  in the manner previously described, seat sleeve  348  may be actuated by dropping a ball  400  through coiled tubing  26  and joint locator  28 . Ball  400  is sized so that it will pass through flow passageway  222  in joint locator  28  until it engages chamfered seat  354  at the top of seat sleeve  348 . Ball  400  is sized so that it will not pass into central opening  352  in seat sleeve  348 , and thus, the ball prevents further circulation of fluid out of joint locator  28  because circulating port  324  is effectively closed. Fluid pressure then applied to seat sleeve  348  and ball  400  forces the seat sleeve downwardly, shearing shear pin  350 . Seat sleeve  348  is thus moved downwardly until recess  364  therein is aligned with port  346  in seat body  328 . Thus, flow ports  362  in seat sleeve  348  are placed in communication with body passageway  342  in seat body  328 . This places rupture disk  376  in communication with the flow passageway  222  in joint locator  28 , and by applying sufficient pressure to rupture the rupture disk, flow passageway  222  is placed in communication with well tool  30  so that well tool  30  may be used in its prescribed manner. Thus, seat sleeve  348  and rupture disk  376  may be said to provide a pressure isolation means for preventing premature communication between the pressure in coiled tubing  26  and any tool  30  positioned below joint locator  28 . 
     It will be seen, therefore, that the wireless coiled tubing joint locator of the present invention is well adapted to carry out the ends and advantages mentioned, as well as those inherent therein. While a presently preferred embodiment of the apparatus has been described for the purposes of this disclosure, numerous changes in the arrangement and construction of parts may be made by those skilled in the art. All such changes are encompassed within the spirit and scope of the appended claims.