Patent Publication Number: US-6991035-B2

Title: Drilling jar for use in a downhole network

Description:
This invention was made with government support under Contract No. DE-FC26-01NT41229 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to oil and gas drilling, and more particularly to apparatus and methods for integrating network and other transmission media into downhole drilling tools. 
     2. Background 
     During downhole drilling operations, drilling jars are used to send shock waves up and down the drill string to dislodge or loosen stuck drill string components, such as a drill bit. Most drilling jars operate by storing potential energy generated from tension or compression in the drill string caused by straining or compressing the drill string uphole at the drill rig. The jar releases this potential energy by suddenly opening, thereby allowing energy stored as strain or compression in the drill string to be released, causing shock waves to travel in a desired direction along the drill string. These shock waves may be sufficient to dislodge a stuck downhole tool or tools. 
     Most downhole tools have several characteristics in common. For example, due to the shape and configuration of a drill string, many downhole tools, with the exception of the drill bit, have a “pin end” and “box end” to enable the tools to be connected in series along the length of the drill string. The pin end is characterized by external threads that may be threaded into corresponding internal threads of the box end. Because torque is applied to the drill string to rotate the drill bit, the box end and pin end are rotationally fixed with respect to one another. In most cases, the box end and pin end are also axially fixed with respect to one another, meaning that the length of the tool is fixed. 
     However, in certain types of downhole tools, such as in downhole jars, the length of the tool is variable. For example, a downhole drilling jar generates shock waves by allowing rapid axial movement between the box end and pin end. The axial movement is suddenly stopped when an internal “hammer” hits an internal “anvil”, causing significant shock waves to propagate from the jar. In most jars, the total axial range of motion is limited to approximately 24 inches. 
     As drilling continues to advance, downhole tools that have axial movement between the pin end and box end may present certain challenges. For example, apparatus and methods are currently being developed to integrate network cable or other transmission media into downhole tools in order to transmit data from downhole tools and sensors to the surface for analysis. This may enable information to be transmitted at much higher speeds than is currently available using current technologies, such as mud pulse telemetry. 
     Most cables use various types of metals, such as copper or aluminum, to transmit electrical signals. These cables are generally fixed in length and are not suitable to be significantly stretched. In axially rigid tools, namely those tools that have a fixed length, integrating cable or other transmission media into the tool body may require little stretching or adjustment of the cable&#39;s length. However, in downhole tools such as drilling jars, where the length of the tool may change significantly, apparatus and methods are needed to integrate transmission cable into the tool body, while accommodating changes in the tool&#39;s length. 
     Another problem is the lack of space within the tool to integrate transmission cable. For example, in drilling jars, most of the internal space of the jar is dedicated to components, such as the hammer, anvil, hydraulic fluid, valves, and other moving parts. Thus, apparatus and methods are needed to integrate transmission cable into the tool, while avoiding interference with components inside the tool. Certain types of jars may accommodate the integration of transmission cable better than others depending on their internal structure and functions. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is a primary object of the present invention to provide apparatus and methods for integrating transmission cable into the body of selected downhole tools, such as drilling jars, having variable or changing lengths. It is a further object of the invention to integrate transmission cable into downhole tools, while avoiding interference with moving or other components within the tools. It is yet another object to accommodate changes in tension that may exist within transmission cable in downhole tools having variable length. 
     Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a wired downhole drilling tool is disclosed in one embodiment of the invention as including a housing and a mandrel insertable into the housing. A coiled cable is enclosed within the housing and has a first end connected to the housing and a second end connected to the mandrel. The coiled cable is configured to stretch and shorten in accordance with axial movement between the housing and the mandrel. A clamp is used to fix the coiled cable with respect to the housing, the mandrel, or both, to accommodate a change of tension in the coiled cable. 
     In selected embodiments, the coiled cable is comprised of a transmission cable enclosed within a conduit. In certain embodiments, the conduit may be constructed of a resilient or elastic material, such as stainless steel. This may enable the conduit to be shaped or molded into a spring-like coil that returns to its original dimensions after being stretched or compressed. In selected embodiments, the spring-like coil may be kept in compression within the housing such that the spring-like coil expands according to the available space within the tool. 
     In selected embodiments, the clamp may be configured to increase its grip on the coiled cable in response to an increase in tension in the coiled cable. This may decrease the chance of the conduit slipping with respect to the clamp. In certain embodiments, the clamp is configured to hold at least 10 pounds of tension in the coiled cable. In selected embodiments, the coiled cable may comprise a first straight portion, a coiled portion, and a second straight portion. The clamp may grip the coiled cable proximate the junction between the first straight portion and the coiled portion, the junction between the second straight portion and the coiled portion, or both. This allows the first straight portion, the second straight portion, or both, to be tensioned greater than the coiled portion. In selected embodiments, the first straight portion, the coiled portion, and the second straight portion are formed from a single continuous cable. 
     In another aspect of the invention, a method for wiring a downhole-drilling tool, wherein the downhole-drilling tool has a housing and a mandrel insertable and axially translatable with respect to the housing, includes connecting a first end of a coiled cable to the mandrel. The method further includes connecting a second end of the coiled cable to the housing, wherein the coiled cable stretches and shortens according to axial movement between the housing and the mandrel. The method further includes fixing the coiled cable with respect to at least one of the housing and the mandrel, to accommodate a change of tension in the coiled cable. 
     In selected embodiments, the coiled cable may comprise a transmission cable enclosed within a conduit. In certain embodiments, the conduit may be constructed of a resilient material. For example, constructing the conduit of a resilient material may enable the conduit to be formed into a spring-like coil. Such a spring-like coil, for example, may be in constant compression within the housing. 
     In certain embodiments, fixing may include increasing the grip on the coiled cable in response to an increase in tension in the coiled cable. In certain embodiments, fixing may include resisting at least 10 pounds of tension in the coiled cable. In selected embodiments, the coiled cable may comprise a first straight portion, a coiled portion, and a second straight portion. Fixing may further comprise fixing the coiled cable proximate the junction between the first straight portion and the coiled portion, the junction between the second straight portion and the coiled portion, or both. In this way, the first straight portion, the second straight portion, or both, may be tensioned differently than the coiled portion. In selected embodiments, the first straight portion, the coiled portion, and the second straight portion are formed from a single continuous cable. Fixing may include a step such as welding, gluing, clamping, or a combination thereof, of the coiled cable to the housing, the mandrel, or both, to absorb a change of tension in the cable. 
     In another aspect of the invention, a wired downhole-drilling tool includes a housing and a mandrel insertable into the housing. The mandrel is axially translatable but rotationally fixed with respect to the housing. A cable is coiled around the mandrel and enclosed by the housing. A clamp fixes the cable with respect to the housing, the mandrel, or both, to accommodate changes of tension in the cable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will become more fully apparent from the following description, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments in accordance with the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of one embodiment of a drilling jar for use with the present invention; 
         FIG. 2  is a perspective cross-sectional view of one embodiment of a cable routed through a jar; 
         FIG. 3  is a cross-sectional view illustrating one embodiment of one component of the jar mandrel; 
         FIG. 4  is a perspective view illustrating one embodiment of a component of the jar housing; 
         FIG. 5  is a perspective view illustrating one embodiment of a coiled cable in accordance with the invention; 
         FIG. 6  is a perspective view illustrating one embodiment of the relationship between the coiled cable and components of the jar housing and jar mandrel in an expanded or partially expanded state; 
         FIG. 7  is a perspective view illustrating one embodiment of the relationship between the coiled cable and components of the jar housing and jar mandrel in a compressed or partially compressed state; 
         FIG. 8  is a front view illustrating one embodiment of a coiled cable passing though a recess in a component of the mandrel; 
         FIG. 9  is a front view illustrating one embodiment of a coiled cable retained by a clamp in accordance with the invention; 
         FIG. 10  is a cross-sectional side view of the illustration of  FIG. 9  illustrating one embodiment of a coiled cable passing through a channel in the mandrel into the central bore of the mandrel; 
         FIGS. 11–14  are several perspective views of one embodiment of a clamp in accordance with the invention; and 
         FIGS. 15–16  are several perspective views of one embodiment of a complementary clamping mechanism that may be included with the clamp illustrated in  FIGS. 11–14 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of embodiments of apparatus and methods of the present invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of various selected embodiments of the invention. 
     The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. Those of ordinary skill in the art will, of course, appreciate that various modifications to the apparatus and methods described herein may easily be made without departing from the essential characteristics of the invention, as described in connection with the Figures. Thus, the following description of the Figures is intended only by way of example, and simply illustrates certain selected embodiments consistent with the invention as claimed herein. 
     Referring to  FIG. 1 , a drilling jar  10  adaptable for use with the present invention is illustrated. The drilling jar  10  is illustrated very generally to illustrate various features, components, and functions that may be typical of a wide variety of drilling jars. More specific details of the drilling jar are not described in this specification and are unneeded to accurately describe apparatus and methods in accordance with the invention. For more specific details with respect to the internal functions of selected drilling jars, the reader is referred to issued patents such as U.S. Pat. No. 5,647,466 to Wenzel or U.S. Pat. No. 5,984,028 to Wilson. 
     The majority of drilling jars  10  include a housing  12  and a mandrel  14  inserted into the housing  12 . The mandrel  14  is axially translatable with respect to the housing  12  to permit variation of the jar&#39;s length. That is, the mandrel  14  may slide into or out of the housing  12 . However, the mandrel  14  is typically rotationally fixed with respect to the housing to allow a torque to be applied through the drilling jar  10  to other connected downhole tools. As is customary in most downhole drilling tools, the jar  10  includes a box end  16  and a pin end  18  to enable connection to other components or tools of a drill string. 
     As was previously described, the jar  10  provides its “jarring” effect by allowing rapid axial movement between the mandrel  14  and the housing  12 . This axial movement is stopped when a hammer  20  rigidly connected to the mandrel  14  comes into contact with an anvil  22 ,  24  of the housing  12 . The hammer  20  may contact a first anvil  22  to send a shock wave in a first direction up the drill string. Likewise, the hammer  20  may contact a second anvil  24  to send a shock wave in the opposite direction. The range of axial movement of the housing  12  with respect to the mandrel  14  is typically on the order of 24 inches or less. 
     Likewise, a drilling jar  10  may include a release mechanism  26 . When it is desired to send a shock wave up or down a drill string, tension or compression is placed on the drill string, depending on the direction the shock wave is to be sent. The release mechanism  26  serves to resist axial translation of the housing  12  with respect to the mandrel  14  caused by this tension or compression, thereby allowing potential energy to be stored in the drill string. The release mechanism  26  may allow slight axial movement between the housing  12  and the mandrel  14 . The release mechanism  26  reaches a threshold wherein resistance to the axial movement is released, thereby allowing the stored potential energy to cause rapid axial movement between the housing  12  and the mandrel  14 . The hammer  20  then strikes one of the anvils  22 ,  24 , causing the shock wave. The release mechanism may operate using hydraulics, springs, or other methods, as desired, to provide functionality to the jar  10 . 
     Referring to  FIG. 2 , one embodiment of a pin end  18  of a selected drilling jar  10  is illustrated. Nevertheless, the technology described herein may be equally applicable to other types of drilling jars having diverse configurations. For example, as illustrated, an apparatus in accordance with the invention is installed near the pin end  18  of a drilling jar  10 . However, in other types of drilling jars  10 , it may be appropriate to install similar apparatus near the box end  16 . This may depend on the design of the mandrel  14  and the housing  12  and the space available or constraints of each particular drilling jar  10 . 
     The drilling jar  10  illustrated in  FIG. 2  illustrates one type of drilling jar  10  that has been found suitable for use with apparatus and methods in accordance with the invention. The drilling jar  10  and corresponding components into which apparatus and methods in accordance the invention are integrated is the Dailey Hydraulic Drilling Jar manufactured by Weatherford Corporation. For further details regarding this drilling jar, the reader should refer to technical materials distributed by the manufacturer. Other types and configurations of drilling jars  10 , produced by either the same or other manufacturers, may be adaptable for use with apparatus and methods in accordance with the invention. These other jars are, therefore, intended to be captured within the scope of this specification and accompanying claims. 
     As was previously discussed, transmission cable or other transmission media may be integrated directly into drill strings. This may allow data to be transmitted at high speed from downhole drilling components, such as those located proximate a bottom hole assembly, to the surface for analysis. Data may also be transmitted from the surface to downhole components. 
     Although most downhole tools have a fixed length, selected downhole tools, such as downhole drilling jars  10 , may actually vary in length. This variable length creates several challenges when integrating transmission cable into the tool. Thus, what are needed are apparatus and methods for integrating transmission cable into these types of tools that can accommodate the variation in length. It is worthy to note that apparatus and methods in accordance with the invention may be applicable in downhole drilling tools of variable length other than downhole drilling jars  10 . These other tools, whatever they might be, are also intended for capture within the scope of the specification and accompanying claims. 
     As previously described, a downhole-drilling jar  10  may include a mandrel  14  that may slide in an axial direction with respect to a housing  12 . In selected embodiments, the mandrel  14  may comprise multiple components  14   a ,  14   b  connected together. Likewise, the housing  12  may also include multiple components  12   a ,  12   b  connected together. That is, the mandrel components  14   a ,  14   b  that are connected together may function as a single rigid component  14  that may slide with respect to housing components  12   a ,  12   b  that may also function as a single rigid component  12 . The components  12   a ,  12   b ,  14   a ,  14   b  may take on various forms, as needed, in accordance with a particular design or configuration of a drilling jar  10 . 
     Various seals  36 , pistons  36 , or other components  36  may be present between the mandrel  14   a ,  14   b , and the housing  12   a ,  12   b  to provide bearing surfaces on which the mandrel  14  or housing  12  slides, or to retain fluids, such as hydraulic fluid, or gasses within various internal chambers  37   a ,  37   b  between the housing  12  and the mandrel  14 . 
     In accordance with the invention, a coiled transmission line  28  may be inserted within the housing  12  and coiled around the mandrel  14 . The coiled transmission line  28  is used to accommodate axial movements between the mandrel  14  and the housing  12 . When movement between the mandrel  14  and the housing  12  occurs, the coil  28  may stretch and compress as a spring, thereby increasing or decreasing in length. The coil may include a first end  30  that may interface or be integrated into the mandrel  14  and a second end  32  that is integrated into housing  12 . In selected embodiments, the coil  28  and corresponding first and second ends  30 ,  32  are formed from a continuous section of transmission cable or other transmission media. 
     Referring to  FIG. 3 , one component  14   b  of the mandrel  14  may appear as illustrated. As was previously mentioned, the component  14   b  is specific to the drilling jar illustrated and is not necessarily representative of all or even the majority of drilling jars  10  available. Thus, apparatus and methods in accordance with the invention should not be limited to this particular configuration, the same being used only as an example. 
     The mandrel component  14   b  may include an outer cylindrical surface  40  that may or may not contact the inner surface of the housing  12 . The mandrel component  14   b  may also include an opening  38  or junction point  38  where the mandrel component  14   b  may connect, using threads or other means, to other components or sections of the mandrel  14 . An anti-rotation mechanism  42 , which may consist of a series of flat faces, may be integrated into the mandrel  14  to prevent the mandrel  14  from rotating with respect to the housing  12 . The mandrel component  14   b  may also be formed to include one or several apertures  44  that may provide various functions. For example, the apertures may perform tasks such as permitting the flow of fluids or gases through the mandrel component, releasing pressure buildup in chambers of the jar  10 , permit the dissipation of heat, or the like. 
     Referring to  FIG. 4 , a corresponding housing component  12   b , into which the mandrel component  14   b  slides, may appear as illustrated. The housing component  12   b  includes an interior surface  46  that slides with respect to and in close proximity to the corresponding outer surface  40  of the mandrel component  14   b . A channel  48  may be formed or milled into the housing component  12   b  to accommodate a transmission line. The channel  48  may be open to permit the transmission line to transition from the housing component  12   b  to another component of the housing  12 . 
     An aperture  50  is provided in the housing component  12   b  to allow the exit of the transmission line from the housing component  12   b . A contoured support  52  may be provided to support and relieve stress from bends present in the transmission line. The housing component may also include one or several apertures  54 , providing any of various functions such as those mentioned with respect to apertures  44  described in  FIG. 3 . 
     Referring to  FIG. 5 , a coiled transmission line  28  is illustrated. The coiled transmission line  28  may include multiple coils  56  to expand and contract in a spring-like manner to accommodate axial variations in the jar&#39;s length. The coils  56  may transition to substantially straight sections  30 ,  32  by way of bends  58   a ,  58   b  in the coiled line  28 . In selected embodiments, the transmission line  28  may include an outer conduit enclosing one or several transmission cables. For example, the outer conduit may be constructed of a material, such as stainless steel, to resist corrosion as well as to provide the spring-like characteristics of the coiled transmission line  28 . The stainless steel is sufficiently resilient to return to its original shape after being stretched or compressed. 
     It has also been found advantageous to form the transmission line  28  from a single continuous section of conduit, although this is not mandatory. Prior to this application, the forming of a stainless steel conduit into multiple spring-like coils was not known. Continuity of the transmission line  28  prevents various problems that may arise from having multiple connections within the jar and also facilitates higher tensioning of the straight sections  30 ,  32  of the transmission line  28  compared to the coils  56 . 
     Referring to  FIG. 6 , the coiled transmission line  28  is integrated with the mandrel component  14   b  and the housing component  12   b . As illustrated, the housing and mandrel components  12   b ,  14   b  are in an extended state  62 . Likewise, the coiled transmission line  28  is also in an extended or expanded state  62 . In selected embodiments, the coiled transmission line  28  may be in constant compression. That is, the coiled transmission line  28  may be “sprung” such that it is always in compression, whether the housing and mandrel components  12   b ,  14   b  are in an extended or non-extended state. This may keep the coiled transmission line  28  stable and prevent rattling or unnecessary movements of the transmission line  28  with respect to the housing and mandrel components  12   b ,  14   b.    
     As illustrated, the contoured support  52  conforms to the shape or bend of the transmission line  28  as it transitions from the coiled portion to the straighter section  32 . Likewise, a clamp  64  may also be used where the coiled transmission line  28  transitions to a straighter section  30 . 
     In certain embodiments, such as may be the case with the section  30  of the transmission line, the section may be routed a significant distance through the central bore  17  of the jar  10  (not shown). In order to keep the section  30  tautly strung through the central bore  17  and to prevent the movement of the section  30  that may occur in the midst of drilling mud, pressure, and other substances and activity within the central bore  17  of the jar  10 , the section  30  may be tensioned significantly. Thus, apparatus and methods are needed to securely hold the ends of the section  30  to maintain a desired tension. The clamp  64  may serve to securely hold the transmission line and enable a significant change in tension between the coiled section  28  and the straighter section  30 . 
     Likewise, the section  32  may also be tensioned higher than that of the coiled portion  28 . However, since this section  32  may be significantly shorter than the section  30 , the tension may not be as high and a clamp may not be needed. The bend  58   b  in the conduit may be sufficient to withstand the change in tension. Nevertheless, in selected embodiments, it may be desirable to provide a clamp at or near the bend  58   b.    
     Referring to  FIG. 7 , as illustrated, the housing and mandrel components  12   b ,  14   b  are in a compressed or non-extended state  62 . Likewise, the coiled transmission line  28  is also in a compressed state  66 . The compressed state illustrated in  FIG. 7  shows the approximate relationship of components when the hammer  20  strikes the lower anvil  24 , while the state illustrated in  FIG. 6  shows a relationship of components when the hammer  20  strikes the upper anvil  22 . 
     Referring to  FIG. 8 , a channel  68  or recess  68  may be formed in the mandrel component  14   b  to route the coiled transmission line  28  to the central bore  17  of the jar  10 . In selected embodiments, one or several threaded apertures  70  may be provided to securely mount the clamp  64  (not shown). The clamp  64  may be used to securely fix the transmission line  28  and also provide support to the bend  58   a.    
     Referring to  FIG. 9 , in selected embodiments, the clamp  64  may be attached to the mandrel component  14   b  to secure the transmission line  28 . In this embodiment, the clamp  64  has several tabs  74  that engage apertures  44  to provide additional strength to the clamp  64 , although this is not mandatory. One or several fasteners  74 , such as screws  74 , may be used to secure the clamp  64  to the mandrel component  14   b . The clamp  64  may optionally include a support mount  76  to provide structural support  76  to the bend  58   a  in the transmission line  28 . The structural support  76  may include an elastomeric, plastic, metal, or other contoured support  78  to support the bend  58   a , and may be connected thereto with a fastener  80 . 
     Referring to  FIG. 10 , a cross-sectional view of the apparatus of  FIG. 9  is illustrated. The coiled transmission line  28  may be routed through a channel  82  in the wall of the mandrel component  14   b . In selected embodiments, several bends  84   a ,  84   b  may be formed in the transmission line such that it may extend through the wall and be routed through the central bore  17  of the jar  10 . 
     Also illustrated is the clamp  64 , providing a clamping force on the transmission line  28 , and an optional bottom grip  81  configured to assist the clamp  64  in gripping the transmission line  28 . The clamp  64  and corresponding bottom grip  81  may be configured to increase their grip on the transmission line  28  in response to increased tension in the line  28 . For example, an increase in tension in the line  30  may urge the bottom grip  81  in an upward direction. Since the bottom grip  81  is rigid and will resist going around the bend  84 , the net effect will be to squeeze the line  28  tighter, thereby providing a better grip. 
     Referring to  FIGS. 11 through 14 , various perspective views of a clamp  64  in accordance with the invention are illustrated. One or several apertures  86  may be included in the body  96  of the clamp  64  to provide a means for attaching the clamp  64  to the mandrel component  14   b . The clamp body  96  may also be rounded to better conform to the cylindrical contour of the mandrel component  14   b.    
     In order to grip the transmission line  28 , a grip mechanism  90  may be integrated or attached to the clamp  64 . The grip mechanism may include teeth  92  or other surface textures to grip or engage the transmission line  28 . The grip mechanism  90  may also have a rounded contour  92  to conform to the transmission line  28 . In selected embodiments, an aperture  88  may be included in the clamp body  96  to align, connect, or both, the grip mechanism  90  to the clamp  64 . 
     As was previously mentioned, the clamp body  96  may include one or several tabs  74   a ,  74   b  to engage apertures  44  in the mandrel component  14   b . Likewise, a support  78  may also be integrated into or attached to the clamp body  96 . The support  78  may be constructed of any suitable material, including rubber, plastic, metal, and the like, and may be attached to the clamp body  96  with an adhesive or a fastener  72 , such as a washer  94  and screw  72 . 
     Referring to  FIGS. 15 and 16 , in one embodiment, a bottom grip  81 , as described in  FIG. 10 , may include a contoured surface  104  having teeth or other gripping texture to grip the transmission line  28 . The bottom grip  81  may also include an angled portion  102  having teeth  106  or other texture  106  to grip the transmission line  28  at or near the bend  84   b  (See  FIG. 10 ). Likewise, the bottom grip  81  may have a bottom surface  100  that slides with respect to the bottom of the channel  68  or recess  68 . Thus, when the transmission line  30  is pulled tighter, the bottom grip  81  may move slightly toward the bend  84   b  with the transmission line  30 . This may cause the teeth  106  to dig into or grip the transmission line  30  in proportion to the increased tension. 
     The present invention may be embodied in other specific forms without departing from its essence or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes within the meaning and range of equivalency of the claims are to be embraced within their scope.