Abstract:
A backoff sub includes a housing; and a backoff facilitator at least partially within the housing. Capable of adding energy to a system within which the sub is disposable. A method for managing a stuck string in a wellbore is also included.

Description:
BACKGROUND 
       [0001]    In the hydrocarbon recovery industry, tools can and do get stuck in the wellbore during all types of runs, be they drilling, completion, etc. Stuck tools are a source of inefficiency that cost operators significant sums of money in terms of lost days, rig time, lost production, etc. In general, once a stuck is apparent to the operator, a process to determine a depth of what is vernacularly known as the “free point” is undertaken. The free point is that point in the string that is just uphole of the stuck point. The next operation will be to create a jar as close to this point as possible while putting a left handed torque on the string in order to, hopefully, cause the string to unscrew itself right above the stuck point. This, if successfully accomplished, means that all of the string that is free will come out of the well and only leave what is stuck (the fish) behind. Avoiding having a significant amount of a string above the stuck point simplifies the fishing operation that is to follow. Unfortunately, however, this process is unreliable and therefore the art would well receive alternate systems and methods for resolving the shortcomings present in the art. 
       SUMMARY 
       [0002]    A backoff sub includes a housing; and a backoff facilitator at least partially within the housing and capable of adding energy to a system within which the sub is disposable. 
         [0003]    A well system includes a string having a plurality of joints at least one of the joints being addressable from a remote location; and one or more backoff subs each disposed at one of the plurality of joints and capable of producing one or more of a jarring action and a backoff torque action. 
         [0004]    A method for managing a stuck string in a wellbore includes determining a freepoint of the string; addressing a backoff sub nearest and uphole of the determined freepoint; and activating a backoff facilitator in the backoff sub. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0005]      FIG. 1  is a schematic view of a portion of a wellbore with a portion of a string therein; 
           [0006]      FIG. 2  is a schematic view of a sub having a jar producing energetic configuration; and 
           [0007]      FIG. 3  is a schematic view of a sub configuration that produces a left-handed torque in addition to or independent of a jar. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    Referring to  FIG. 1 , a schematic view of a wellbore  10  with a portion of a string  12  therein is depicted. The string  12  comprises a series of tubular members  14  interconnected together at a number of joints  16 - 22  numbered individually because they are treated individually in the system disclosed herein. Further illustrated in the drawing is a material buildup  22  to simulate one possible stuck scenario. 
         [0009]    Each of the interconnections  16 - 22  is an individually addressable connection configured as a backoff sub having a backoff facilitator disposed at least partially within a housing. The facilitator is such as but not limited to an explosive backoff charge, an acoustic generator, a spark gap tool, a low pressure chamber, a piezoelectric device, a torque producer, etc. The individual sections  14  of the string  12  further include a high bandwidth communications conduit (not shown) that may be provided by, for example, utilizing a wired pipe commercially available from Grant Prideco, Houston, Tex., or may be provided by utilizing an umbilical. The high bandwidth communication provided by the conduit allows for addressability at a number of places along the string, and in some embodiments, each joint of the string  12 . Therefore, upon determining the location of the stuck point/free point of a string that is experiencing difficulty, a specific addressable backoff facilitator may be activated. This may occur while left hand torque is applied to the string simultaneously from a remote location (e.g. surface) or the backoff facilitator itself may create backoff torque, or both. Where only a jar is to be produced, a charge similar to those commercially available (string shot back off tool from Baker Hughes Inc., for example) for use on wireline or any other the other facilitators noted above might be employed and can be incorporated into the string  12  as its own sub, for example, screwing into the string at each joint. This is schematically illustrated in  FIG. 2 . If torque is intended to be generated by the configuration, a torque producing sub is employed in one or more joints as illustrated in  FIG. 3 . 
         [0010]    Referring to  FIG. 2 , a section  14  of the string  12  (see  FIG. 1 ) is illustrated with a pin  26  receivable in a box  28  of a backoff sub  30 . The backoff sub  30  includes its own pin  32  receivable in a box  34  of the next adjacent string section  14 . One of ordinary skill in the art will immediately recognize that without the backoff sub  30 , the connection of pin  26  would be to box  34 . Thus the backoff sub  30  is interposed between sections  14  that would traditionally have been screwed together. The back off sub  30  includes a backoff facilitator  36 , which may be as noted above. A jar, vibration or torque applied by the action of the facilitator in close proximity of the target joint is very helpful in causing the target joint to back off.  FIG. 2  schematically illustrates the facilitator  36  as making up a part of the sub  30 . The facilitator may be an explosive charge, piezoelectric stack, vibrator, etc., disposed within a wall of the sub  30  whether enclosed therein or not. Left hand torque will be applied from the surface or other remote location in this embodiment as the jar produced is non-directional. In this embodiment, either of the threaded connections of the backoff sub might be the one backed off with roughly equivalent results relative to the string  12 . 
         [0011]    Referring to  FIG. 3 , a somewhat more complex embodiment is illustrated in that it does not require but can be used in conjunction with left hand torque from the surface or other remote location. In this embodiment, left hand torque is generated by the application of a mechanical load axially on a configuration that is capable of translating that load to a rotational torque. The backoff facilitator in this embodiment is thus not merely passive relative to the application of torque but is productive of the torque. Referring to  FIG. 3 , a schematic cross-section view of a torque inducing backoff sub  40  is illustrated. Similar to the foregoing embodiment, the sub  40  includes a pin  42  and a box  44  to enable the interconnection of the sub within a string  12  (see  FIG. 1 ), and at one or more joints (for example, in FIG.  1 ., numerals  16 ,  18 ,  20  and/or  22 ) thereof. Within a housing  46  of the sub  40  is a series of components that together are capable of producing torque. A linear actuator  48 , which may be an explosive charge, is disposed within a cavity  50 . In the event that the linear actuator  48  is indeed a pressure-creating configuration, such as the explosive noted, the cavity  50  will also include a compartment  58  that is volumetrically expandable. Also disposed within the cavity  50  is a driving torque mass  52 , which in the illustrated embodiment is a piston. The mass  52  is sealed at an inside dimension and at an outside dimension thereof with seals  54  and  56  such as o-rings to inside surfaces of the cavity  50 , respectively. Due to the seals maintaining a compartment  58  of cavity  50  fluidly segregated from the remaining chamber  60  of cavity  50 , a pressure creating configuration within cavity  50 , such as the explosive embodiment of linear actuator  48 , is useful to cause the compartment  58  to expand by pressurizing an end  62  of mass  52  and moving it in a direction consistent with enlargement of compartment  58 . This will bring mass  52  towards one or more torque drive reaction pins  64 . Each torque drive reaction pin  64  presents an angular face  66  that faces a clockwise or right hand direction when the sub  40  is viewed in a transverse cross-section. This is so that when mass  52  is driven into the face  66 , a reaction torque is produced in a counterclockwise or left hand direction thereby acting to back off a threaded interface  68 . The torque created can be a jarring torque only will little actual rotation at the thread interface or the torque reaction pins  64  can be mounted in a spin collar  70 , a rotatable portion of the housing  46 , to allow actual rotation  1  movement of the threaded interface. The spin collar  70  rotates in one direction only, that direction being opposite the direction of tightening of the threaded interface so that upon the creation of torque by linear actuation of the backoff facilitator  48 , the spin collar  70  allows the unthreading of the threaded interface and thus facilitates the retrieval of the string uphole of the targeted joint. 
         [0012]    While the mass  52  may simply be a castellated cut at a torque drive end  72  thereof, in one embodiment, the torque drive end  72  may be configured with one or more angled faces  74  that face a counter clockwise or left have direction so that they will interact with faces  66  during actuation of the sub  40  to help produce the desired torque. Where the faces  74  are provided (as opposed to the castellated embodiment), more torque is generated due to the reduction of frictional losses at the interface between the mass  52  and the reaction pins  64 . While the terms “one or more” as used above indicate that a single reaction pin  64  is contemplated and would be operative with the mass  52 , more than one reaction pin  64 , so that forces may be balanced perimetrically, produces a smoother more effective torque. For example, two pins  64  positioned diametrically opposed to each other (about 180 degrees apart); three pins  64  positioned about 120 degrees apart; four pins  64  positioned about 90 degrees apart; and so on where the included angle is dictated by 360 degrees divided by the number of angles represented will have the balanced result. 
         [0013]    In order to activate the actuator  48 , one embodiment includes an electronics package  80  disposed operably near the actuator  48  and in one embodiment in the cavity  50 , as illustrated. The package is in communication with a wired pipe through such as a conductor  82  connected to an inductive coupling  84  that itself communicates inductively with another inductive coupling  86  across threaded connection  88 . Inductive couplings  90  and  92  are provided at an opposite end of the sub  40  to maintain connectivity to other parts of the string. As will be appreciated by one of skill in the art, the sub  40  includes signal interconnection between inductive couplings  84  and  90  although such is not specifically shown. 
         [0014]    In a particular iteration of the torque producing embodiment disclosed herein, still referring to  FIG. 3 , the seals  54  and  56  function not only to hold fluid pressure in compartment  58  but to hold pressure in chamber  60  of cavity  50 . In this iteration a fluid within chamber  60  is pressurized when the compartment  58  is expanded. The pressurized fluid is ported through one or more ports  94  to the threaded interface  68  causing that interface to grow slightly volumetrically. This action tends to reduce available friction in the threaded interface thereby making backoff of the joint easier and thus making the sub  40  more effective. Adjusting the level of incompressibility of the fluid in chamber  60  while ensuring that the expansion of compartment  58  can still occur as designed will adjust the amount of volumetric growth in the threaded interface  68 . 
         [0015]    While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.