Abstract:
A telemetry system for a downhole tool positionable in a wellbore penetrating a subterranean formation is provided. The telemetry system includes a telemetry tool engageable within the downhole tool. The telemetry tool including a telemetry unit, the unit being interchangeable between a mud pulse telemetry unit and an electromagnetic telemetry unit.

Description:
CROSS-REFERENCES  
       [0001]     The present application claims priority of U.S. Provisional Patent Application Ser. No. 60/594,273 filed on Mar. 24, 2005. The Provisional Application is incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to the exploration/production of a subterranean formation penetrated by a wellbore. More particularly, the present invention relates to techniques for communicating between equipment at the surface, and a downhole tool positioned in the wellbore.  
         [0003]     The exploration and production of hydrocarbons involves placement of a downhole tool into the wellbore to perform various downhole operations. There are many types of downhole tools used in hydrocarbon reservoir exploration/production. Typically, a drilling tool is suspended from an oil rig and advanced into the earth to form the wellbore. The drilling tool may be a measurement-while-drilling (MWD) or a logging-while-drilling (LWD) tool adapted to perform downhole operations, such as taking measurements, during the drilling process. Such measurements are generally taken by instruments mounted within drill collars above the drill bit and may obtain information, such as the position of the drill bit, the nature of the drilling process, oil/gas composition/quality, pressure, temperature and other geophysical and geological conditions.  
         [0004]     Downhole drilling and/or measurement tools may be provided with communication systems adapted to send signals, such as commands, power and information, between a downhole unit housed in the downhole tool, and a surface unit. Communication systems in drilling tools may include, for example, mud pulse systems that manipulate the flow of drilling mud through a downhole drilling tool to create pressure pulses. One such mud pulse system is disclosed in U.S. Pat. No. 5,517,464 and assigned to the present assignee, the entire contents of which are hereby incorporated by reference.  
         [0005]     Wireless communication techniques, such as electromagnetic (or EMAG) telemetry systems, have also been employed in downhole drilling tools. Such systems include a downhole unit that creates an electromagnetic field capable of sending a signal to a remote surface unit. Examples of electromagnetic telemetry systems are disclosed in U.S. Pat. Nos. 5,642,051 and 5,396,232, both of which are assigned to the present assignee.  
         [0006]     Advancements, such as the use of repeaters and gaps, have been implemented in existing drilling tools to improve the operability of electromagnetic systems in drilling applications. By creating a gap, or non-conductive insert, between adjoining sections of drillpipe, the electromagnetic field is magnified and provides an improved signal. Examples of a gap used in an electromagnetic telemetry system are described in U.S. Pat. No. 5,396,232, assigned to the present assignee, and U.S. Pat. No. 2,400,170 assigned to Silverman.  
         [0007]     In some cases, such as deep well applications, mud pulse telemetry may be the best telemetry source. In other cases, such as high data rate, high rate of penetration conditions and poor quality mud conditions, electromagnetic telemetry may provide the best telemetry source. For example, electromagnetic telemetry is simple to set up and operate, but can be dependent on formation characteristics and have limited depth capability. In other cases, mud pulse telemetry tools may be capable of extreme depths, but may be sensitive to the mud conditions and require more expertise to operate.  
         [0008]     In some cases, telemetry systems have also been made retrievable. For example, U.S. Pat. No. 6,577,244 describes a retrievable while drilling tool. Existing telemetry tools are typically housed in an expensive drill collar, designed specifically to couple with the telemetry tool. These expensive drill collars typically have an orientation feature at the bottom to orient the sensors relative to the drill collar and a telemetry sub, which facilitates the transmission of the information to the surface.  
         [0009]     It is, therefore, desirable to provide a telemetry system that is adaptable to a variety of wellbore conditions. It is further desirable that such a system be convertible between different types of telemetry systems, and/or provide an efficient orientation system. Additional features may also be provided to enhance reliability, operational efficiency, power capability, size scalability, orientation and/or retrievability.  
       SUMMARY OF THE INVENTION  
       [0010]     The invention provides a telemetry system for a downhole tool positionable in a wellbore penetrating a subterranean formation. The system includes a telemetry tool engageable within the downhole tool. The telemetry tool comprising a telemetry unit, the unit being interchangeable between a mud pulse telemetry unit and an electromagnetic telemetry unit.  
         [0011]     The invention provides a telemetry system for a downhole tool positionable in a wellbore penetrating a subterranean formation. The system includes a telemetry tool comprising an electromagnetic telemetry tool and a mud pulse telemetry tool, wherein the electromagnetic telemetry tool or the mud pulse telemetry tool may be individually disposed or retrieved from the telemetry tool when the tool is disposed in the wellbore.  
         [0012]     The invention provides a method of disposing a telemetry system within a wellbore penetrating a subterranean formation. The method includes engaging a telemetry tool within a downhole tool for disposal in the wellbore, wherein the telemetry tool comprises a telemetry unit being interchangeable between a mud pulse telemetry unit and an electromagnetic telemetry unit; and selectively equipping the telemetry tool with a mud pulse telemetry unit or an electromagnetic telemetry unit when the downhole tool is disposed in the wellbore 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     These and other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying Figures, wherein:  
         [0014]      FIG. 1  is a schematic illustration of a downhole tool suspended in a wellbore from a drilling rig via a drill string, the downhole tool provided with a telemetry tool in accordance with the teaching of the present invention;  
         [0015]      FIG. 2A  is a schematic illustration of one embodiment of an electromagnetic telemetry tool in accordance with the teachings of the present invention;  
         [0016]      FIG. 2B  is a schematic illustration of another embodiment of an electromagnetic telemetry tool in accordance with the teachings of the present invention;  
         [0017]      FIG. 3A  is a schematic illustration of one embodiment of a mud pulse telemetry tool in accordance with the teachings of the present invention;  
         [0018]      FIG. 3B  is a schematic illustration of another embodiment of a mud pulse telemetry tool in accordance with the teachings of the present invention;  
         [0019]      FIG. 4A  is a schematic illustration of a combination telemetry tool showing one embodiment of a hanger system in accordance with the teaching of the present invention; and  
         [0020]      FIG. 4B  is a schematic illustration of a combination telemetry tool showing another embodiment of a hanger system in accordance with the teaching of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Referring now to  FIG. 1 , a rig  11  supports a downhole drilling tool  12  that is suspended from the rig  11  in a wellbore  14 . The downhole tool  12  is adapted to drill the wellbore  14  using a drill bit  16  located at a lower end thereof. The downhole tool  12  is operatively connected to and includes a downhole telemetry tool  18  and a drill string  20 . The drill string  20  includes a plurality of drill collars connected to form the drill string  20 .  
         [0022]     Various components, such as the telemetry tool  18 , sensors  22 , a power unit  24 , as well as other components, are positioned in one or more drill collars and enable the downhole tool  12  to perform various downhole operations. The telemetry tool  18  may be an electromagnetic tool, as further described with respect to  FIGS. 2A and 2B , that communicates with a surface detection unit  26  capable of detecting electromagnetic pulses, or a mud pulse tool, as further described with respect to  FIGS. 3A and 3B , that communicates with a surface detection unit adapted to detect mud pulses, as described in detail below. Thus, in accordance with the teachings of the present invention, the telemetry tools of  FIGS. 2 and 3  contain interchangeable modules. These interchangeable modules allow the telemetry tool  18  of  FIG. 1  to be converted from an electromagnetic telemetry tool to a mud pulse telemetry tool (and vice versa). Furthermore, in accordance with the teaching of the present invention, the telemetry tool  18  of  FIG. 1  can be adapted to include an electromagnetic telemetry tool and a mud pulse telemetry tool. Other telemetry tools, such as an acoustic tool may also be used. Additionally, these telemetry tools may be converted at the surface, or retrieved from downhole for conversion and then reinserted.  
         [0023]     Referring now to  FIG. 1  and  FIG. 2A , a portion of the downhole tool  12  is shown wherein the telemetry tool  18  is an electromagnetic telemetry tool  18 a. The electromagnetic tool  18 a is operatively coupled, preferably via a wireless communication link, to the surface unit  26  (as shown in  FIG. 1 ) for communication therebetween. The electromagnetic tool  18   a  generates an electromagnetic field F receivable by the surface unit  26 . The electromagnetic tool  18   a  transmits the electromagnetic field F that carries the data collected in the downhole tool  12  to the surface unit  26 . The surface unit  26  is also adapted to send an electromagnetic field receivable by the electromagnetic tool  18   a.    
         [0024]     The electromagnetic tool  18   a  is positioned within a collar system  100 . The electromagnetic tool  18   a  includes a fishing head  200 , a battery module  202 , a control unit module  204  and a transmitter module  206 . These modules may be contained in one or more drill collars, which form the collar system  100 . Furthermore, the scope of the present invention is not limited by the relative positioning of the modules; the order of the modules can be altered as desired.  
         [0025]     The fishing head  200  is positioned at an uphole end of the electromagnetic tool  18   a . The fishing head  200  is configured to allow easy retrieval and insertion of the electromagnetic tool  18   a . This is particularly useful when the drill collar system becomes stuck and the electromagnetic tool  18   a  needs to be retrieved before the drill collar system is abandoned. For retrieval, a conventional retrieval device is lowered down the center of the drill collar system or string and attached to the fishing head  200  as known in the art. The telemetry tool  18   a  can then be pulled to the surface for future use.  
         [0026]     The battery module  202  includes one or more batteries, such as sequential depletion batteries, that can be used to provide power to the telemetry tool such as the electromagnetic tool  18   a . The battery system is one mode of powering the tool electronics. In implementations, the most economical system can be employed. Numerous ways to create cost effective power systems include, but are not limited to, batteries with sequential depletion schemes and batteries with internal usage tracking circuits. Other modes are possible, including a turbine/alternator system driven by the drilling fluid flow as known in the art, such as a turbo-modulator.  
         [0027]     The control unit module  204  houses the electronics used to operate the electromagnetic tool  18   a . The electronics in the control unit module  204  are used to send and receive coded messages or data. The control unit module  204  may be configured with electronic circuitry and sensors specifically designed for high reliability. The sensors may be, for example, direction and inclination, gamma ray, resistivity, drilling dynamics or other measurement or logging while drilling sensors. Higher than typical design margins may be incorporated into the design in order to achieve significantly higher reliability. This can be accomplished by, but is not limited to, using Multi-Chip Module (MCM) electronic packaging technology.  
         [0028]     The transmitter module  206  is used to generate the electromagnetic signals that are sent, as well as to detect electromagnetic signals. The transmitter module  206  includes an orienting device  208  that engages a landing device  209  of the collar system  100 , a lower transmitter contact  210  that is positioned within a hole in a lower transmitter receptacle  212  and a non-metallic gap collar  214 . The lower transmitter contact  210  is removably positionable in the lower transmitter receptacle  212 . Preferably, the lower transmitter contact  210  has a tapered nose portion  216  to facilitate insertion into the transmitter receptacle  212 . The gap collar  214  is non-conducting and enhances signal capabilities for the electromagnetic tool  18   a.    
         [0029]     The orienting device  208  has a keyway  218  adapted to abut against the landing device  209  and, hence, position the electromagnetic tool  18   a  within the collar system  100 . The keyway  218  assists in aligning the electromagnetic tool  18   a  within the downhole tool  12 . The combined orienting device  208  and landing device  209  form an integrated landing and orientation device that houses the tool-specific collar hardware in a shorter, less expensive collar system. The remainder of the telemetry tool  18   a  may then be housed in a low cost collar (e.g., a rental monel collar). The integrated device may then be positioned in a short insulated gap collar, such as the gap collar  214 , for electromagnetic telemetry or in a short flow sub for mud pulse telemetry.  
         [0030]     Referring now to  FIG. 2B , an electromagnetic telemetry tool  18 b is positioned within a collar system  102  and forms an alternative embodiment of the telemetry tool  18  of the downhole tool  12  of  FIG. 1 . The collar system  102  includes a flow sleeve  220  proximally positioned relative to a fishing head  222  of the electromagnetic tool  18   b . In the present embodiment, the downhole tool  12  is a convertible downhole tool that can be adapted to include an electromagnetic telemetry tool, a mud pulse tool, or a combination telemetry tool, as discussed in detail below.  
         [0031]     In one embodiment, the electromagnetic tool  18   b  includes a battery module  224  and a control module  226 , each of which are operable in a fashion similar to the operations discussed above with respect to electromagnetic tool  18   a . The electromagnetic tool  18   b  includes a transmitter unit  230  for sending and receiving electromagnetic signals. The transmitter unit  230  includes an orienting unit  232  and a transmitter contact  234 . The orienting unit  232  has a keyway  231  that assists in aligning the electromagnetic tool  18   b  within the collar system  102 . The keyway  231  of the orienting unit  232  engages a landing unit  236  in order to align the electromagnetic tool  18   b . The transmitter contact  234  is positioned within a non-metallic gap collar  238  and retractably positioned within a transmitter receptacle  240 . In a preferred embodiment, the transmitter contact  234  has a tapered nose portion. The gap collar  238  is provided to enhance signal capabilities for the electromagnetic tool  18   b.    
         [0032]     Referring now to  FIG. 3A , a mud pulse telemetry tool  18   c  includes a fishing head  300 , a transmitter module  302 , a control unit module  304  and a battery module  306 . These modules may be contained in one or more drill collars, such as the collar system  104 . The fishing head  300  is positioned at an uphole end of the mud pulse tool  18   c . The fishing head  300  is typically used to insert or retrieve the mud pulse tool  18   c  as known in the art.  
         [0033]     The transmitter module  302  includes a mud pulse generator, such as the one described in U.S. Pat. No. 5,517,464. This transmitter may be provided with an orienting device  308  and corresponding landing device  309 . Accordingly, the orientation device  308  is keyed to the landing device  309  of the collar system  104  for orientating the mud pulse tool  18   c.    
         [0034]     The control module  304  houses the electronics used to operate the mud pulse tool  18   c . The electronics in the control module  304  are used to send mud pulse signals to a detection unit located at the surface as well as to detect mud pulse signals that are received from the surface. Conventional mud pulse hardware may be used to implement embodiments of the invention. The battery module  306  contains batteries used to provide power, as discussed with respect to tools  18   a  and  18   b  of  FIGS. 2A and 2B , respectively. Such batteries may be for example, sequential depletion batteries.  
         [0035]     Referring now to  FIG. 3B  a mud pulse telemetry tool  18   d  used within a common collar system  106  of the downhole tool  12  of  FIG. 1  includes a pressure pulse generator unit  320  and a fishing head  322 . The pulse unit  320  is proximally positioned within a flow sleeve  324  of the collar system  106 . In the present embodiment, the downhole tool  12  is a convertible downhole tool that can be adapted to include an electromagnetic telemetry tool instead of or in addition to a mud pulse telemetry tool.  
         [0036]     In one embodiment, the mud pulse tool  18   d  includes a battery module  326  and a control module  328 , each of which have an operation similar to the operation discussed above with respect to the mud pulse tool  18   c  of  FIG. 3A . In an alternative embodiment, the battery module is supplemented or replaced by a turbine unit that converts mud flow into electrical power and thereby provides power to the tool. Such a power generation unit can be used with any of the tool implementations disclosed herein. In some embodiments, the turbine unit may be included as part of the pulse unit  320  while in alternative embodiments, the turbine unit is a separate unit.  
         [0037]     The mud pulse tool  18   d  includes an orienting unit  330  that includes a keyway  331 . The keyway  331  of the orientation unit  330  engages a landing unit  332  of the collar system  106  in order to align the mud pulse tool  18   d  within the collar system  106 .  
         [0038]     Referring now to  FIG. 4A , a combination telemetry tool  400  includes a mud pulse telemetry unit  402  and an electromagnetic telemetry unit  404 , each located at opposite ends of the telemetry tool  400 . The telemetry tool  400  also includes a fishing head  410 , a control module  412 , and a battery module  414 . The telemetry unit  402  of the telemetry tool  400  is positioned within a flow sleeve  420  of the collar system  108 . The telemetry unit  404  includes a transmitter contact portion  406  that is positioned within a non-metallic gap collar  422  and movably located within a transmitter receptacle sleeve  426 . As discussed above, the gap collar  422  is provided to enhance the electromagnetic signal.  
         [0039]     The telemetry tool  400  includes an orientation unit  430  that is used to align the telemetry tool  400 . The orientation unit  430  has a key  432  that is used to align the telemetry tool  400  in a precise orientation as the key  432  is aligned with a corresponding key-slot in a landing sleeve  434  of the collar system  108 .  
         [0040]     Referring now to  FIG. 4B , a telemetry tool  400   a , similar in function to the telemetry tool  400  of  FIG. 4A , is shown with an alternative orientation unit  440 . The orientation unit  440  is shown to include a load-bearing key  442  positioned within a corresponding notch  444  of a hanger sleeve  446 . As the telemetry tool  400   a  is lowered within a collar system  110 , the key  442  is aligned with the notch  444  of the hanger sleeve  446  and, hence, the telemetry tool  400   a  is accurately aligned and securely positioned within the collar system  110  that is part of the downhole tool  12 .  
         [0041]     With respect to  FIGS. 2A and 3A , the telemetry tools  18   a  and  18   c  are preferably interchangeable. The downhole tool  12  of  FIG. 1  may be provided with an electromagnetic tool, such as the electromagnetic tool  18   a  of  FIG. 2A . The electromagnetic tool  18   a  may then be removed and replaced with the mud pulse tool  18   c  of  FIG. 3A . This is achieved by retrieving the electromagnetic tool  18   a  and replacing certain modules. For example, the transmitter module  206  of the electromagnetic tool  18   a  is replaced with the transmitter module  302  of the mud pulse tool  18   c . In the present example, each of the control units  204  and  304  has sufficient electronics and control systems capable of performing with either the mud pulse telemetry tool or electromagnetic telemetry tool. In this manner, the dowhole tool  12  may be converted between electromagnetic and mud pulse telemetry without retrieving the entire downhole tool  12 . Thus, by way of example, when the depth limits of an electromagnetic telemetry tool are reached, the downhole tool may be converted to a mud pulse telemetry tool by removing the electromagnetic transmitter module  206  of the electromagnetic telemetry tool  18   a  and attaching the mud pulse telemetry transmitter  302  of the mud pulse telemetry tool  18   c . Even though the present example discusses removal and replacement of certain portions of the tool  18 , it is within the scope of present invention to remove one tool and replace it with a new tool, instead of changing certain modules.  
         [0042]     With respect to  FIGS. 2B and 3B , the telemetry tools  18   b  and  18   d  are preferably interchangeable. The downhole tool  12  of  FIG. 1  may be provided with an electromagnetic tool, such as the electromagnetic tool  18   b  of  FIG. 2B . The electromagnetic tool  18   b  may then be removed and replaced with the mud pulse tool  18   d  of  FIG. 3B . This is achieved by retrieving the electromagnetic tool  18   b  and replacing certain modules. For example, the transmitter module  224  of the electromagnetic telemetry tool  18   b  is replaced with the transmitter module  328  of the mud pulse telemetry tool  18   d . In this manner, the dowhole tool  12  may be converted between electromagnetic and mud pulse telemetry without retrieving the entire downhole tool  12 . Thus, by way of example, when the depth limits of an electromagnetic telemetry tool are reached, the tool may be converted to a mud pulse telemetry tool by removing the electromagnetic transmitter module  224  of the electromagnetic telemetry tool  18   b  and attaching the mud pulse telemetry transmitter  328  of the mud pulse telemetry tool  18   d.    
         [0043]     With respect to  FIGS. 4A and 4B , a combination tool is deployed, thereby allowing the downhole tool  12  to communicate information to a remote location using electromagnetic telemetry and/or mud pulse telemetry. The desired telemetry may be determined depending on downhole conditions and the depth of the downhole tool.  
         [0044]     The control systems or control units used herein are preferably provided with automated software capable of automatically performing downhole functions. Various processors or other downhole systems may be provided for use alone or in conjunction with surface systems and the scope of the present invention is not limited thereby. Manual systems may also be provided to activate the tool operations.  
         [0045]     While  FIGS. 1-4  depict various configurations of a convertible or combination telemetry system, the order in which the components are depicted does not limit the scope of the invention. Each of the modules depicted may be re-arranged for a variety of configurations. For example, the transmitter in the electromagnetic telemetry tool may be at the bottom to allow transmission from the tool in quick response to the time the tool exits the casing, for example, or as early as possible in the drilling process.  
         [0046]     While this invention has been described with references to various illustrative embodiments, the description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description.