Abstract:
In order to overcome the limitation of being able to utilize a limited number of sliding sleeves with progressively more restrictive internal diameters in a particular wellbore when selectively opening the sliding sleeve or tool with progressively smaller balls or darts, an encoding dart may be utilized. A wellbore dart or pill is provided with a lock such that upon reaching a corresponding key, dogs are extended radially outward to engage with a tool within the wellbore. Typically the dart will include a lock section having a number of pins wherein each pin must be depressed a proper amount where the amount includes not being depressed to allow a tumbler within the dart to move either rotationally or axially walking a dog in an outward condition.

Description:
BACKGROUND 
       [0001]    In the course of producing oil and gas wells, typically after the well is drilled, the well may be completed. One way to complete a well is to divide the well into several zones and then treat each zone individually. 
         [0002]    Treating each section of the well individually may be accomplished in several ways. One way is to assemble a tubular assembly on the surface where the tubular assembly has a series of spaced apart sliding sleeves. Sliding sleeves are typically spaced so that at least one sliding sleeve will be adjacent to each zone. In some instances annular packers may also be spaced apart along the tubular assembly in order to divide the wellbore into the desired number of zones. In other instances when annular packers are not used to divide the wellbore into the desired number of zones the tubular assembly may be cemented in place. 
         [0003]    The tubular assembly is then run into the wellbore typically with the sliding sleeves in the closed position. Once the tubular assembly is in place in the well and has been cemented in place or the packers have been actuated the wellbore may be treated. 
         [0004]    The wellbore treatment typically consists of high pressure pumping of a viscous fluid containing proppants down through the tubular assembly out of the specified sliding sleeve and into the formation. The high-pressure fluid forms fractures, cracks and fissures in the formation and fills them with proppants. When the treatment ends, the proppants remain in the fractures, holding the cracks and fissures open and allowing wellbore fluid to flow from the formation zone, through the open sliding sleeve, into the tubular assembly, and then to the surface. 
         [0005]    To open a sliding sleeve, an obturator, such as a ball, a dart, etc., is dropped into the wellbore from the surface and pumped through the tubular assembly. The obturator is pumped through the tubular assembly to the sliding sleeve where it lands on the seat of the sliding sleeve and forms a seal with the seat on the sliding sleeve to block all further fluid flow past the ball and the seat. As additional fluid is pumped into the well the differential pressure formed across the seat and ball provides sufficient force to move the sliding sleeve from its closed position to its open position. Fluid may then be pumped out of the tubular assembly and into the formation so that the formation may be treated. 
         [0006]    In order to selectively open a particular sliding sleeve the obturator may be sized so that it will pass through the sliding sleeves until finally reaching the sliding sleeve where the seat size matches the size of the obturator. In practice the sliding sleeve with the smallest diameter seat is located closest to the bottom of toe of the well. Each sliding sleeve above the lowest sliding sleeve has a seat with a diameter that is slightly larger than the seat below it. By using seats that step up in size as they get closer to the surface, a small diameter obturator may be dropped into the tubular assembly and will pass through each of the larger diameter seats on each sliding sleeve above the lowest sliding sleeve. The obturator finally reaches the sliding sleeve with a seat diameter that matches the diameter of the obturator. The obturator and seat block the fluid flow past the sliding sleeve actuating the particular sliding sleeve. 
         [0007]    Progressively larger obturators are launched into the tubular assembly to selectively open each sliding sleeve. Each seat and obturator must be sized so that the seat provides sufficient support for the obturator at the anticipated pressure. Currently there seems to be an upper limit on the number of sliding sleeves that may be actuated by progressively larger obturators and seats thereby limiting the productivity of a single well. An additional limitation of the current technology is that by utilizing progressively smaller seats towards the bottom of the well the productivity of the well is further limited as each seat chokes fluid flow from the bottom of the well towards the top of the well. Therefore in practice there is usually the additional step of drilling out the seats adding further costs to completing the well. 
       SUMMARY 
       [0008]    In order to overcome the limitations of utilizing sequentially sized seats and obturators the current invention provides an actuation dart for actuating the tool in a wellbore. 
         [0009]    A wellbore dart or pill is provided such that a lock section is provided on the dart. The lock section has housing and a tumbler within the housing. The tumbler has a number of pins that are biased outwards. Each pin may be of a different length such that when the pins are all extended, for instance as the dart moves freely through the wellbore, the base of an individual pin and the leading edge of a follower may or may not align with the interface between the tumbler and the sleeve. Typically when all of the pin bases and leading edges of the followers will align with the interface and some will not. The follower may be a button that is pushed radially outward by a biasing device such as a spring for the follower further pushes a pin radially outward. Each of the individual pins and a lock section has its own distance that it must be pushed radially inward in order to align the base of each individual pin and the leading edge of the corresponding individual follower with the interface between the tumbler and the sleeve. When all of the individual pins&#39; bases and the leading edges of each of the followers align with the interface between the tumbler and the sleeve the tumbler, pushed by its own bias device such as a torsion spring, moves. While it is preferred that the tumbler rotates is also envisioned that the tumbler may move axially. 
         [0010]    In certain embodiments the lock section may be provided as part of a portion of the tubular while the key section may be provided by the dart. 
         [0011]    It is generally envisioned that when the tumbler rotates the tumbler will rotate until a stop within the dart is engaged. The stop may be a simple protrusion on the tumbler, on the sleeve, or may be a biased pin that engages with a port within the sleeve. The stop may also include any other means of preventing rotation known. 
         [0012]    Typically the tumbler will rotate 90° and as the tumbler rotates, a cam attached to the tumbler will rotate to force the dogs radially outwards and for as long as the tumbler is locked in the rotated position will retain the dogs in the radially outward position. 
         [0013]    Once the dart has been unlocked with the dogs radially extended, the dart may continue further downhole to engage a tool such as the sliding sleeve where it may seal the wellbore to both allow the sliding sleeve to be opened and further to provide a seal within the tubular to allow fracturing of the formation adjacent the sliding sleeve. When the dart is no longer required to seal the tubular the dogs are allowed to dissolve so that the dart may flow back up out of the wellbore. Generally the dart may flow easily out of the wellbore as the ceiling section of the dart is separate from the dogs such that when&#39;s the dogs are dissolved the dart continues to effectively block fluid flow through the wellbore thus forcing any fluid below the dart to push the dart towards the surface rather than flowing around the dart. 
         [0014]    It is also envisioned that the dart may be used as a transport mechanism so that the dart may move to a predetermined position and may then release a marker such as a chemical, acoustic, electromagnetic, or electronic signal or device. The dart may carry the marker in an internal chamber when the tumbler rotates the chamber is unsealed allowing an electronic device, such as an RFID tag, to flow back to the surface. In some instances the dart may include a sensor such as a temperature, pressure, wellbore fluid sensor, or etc. The dart may then encode information from the sensor and then release a signal to carry the information back to the surface where the signal may be sent via electromagnetic, acoustic, pressure pulse, RFID tag, or etc. In some instances the dart may be coupled to an electric line where the dart may be sent to an exact predetermined location within the wellbore and then communicate with the surface via the electric line. In certain instances the dart may be shaped such that once the dart has reached its position, wellbore fluid may continue to flow around the sides of the dart. In other instances the dart may include a plug that blocks a through bore where the plug dissolves when released at a predetermined time or upon command. The dart may both unseal the chamber and radially extend dogs with the same action. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  depicts a tubular assembly with multiple sliding sleeves and keys in a wellbore. 
           [0016]      FIG. 2  depicts a tubular assembly having closed sliding sleeves, keys, and an encoding dart in a wellbore. 
           [0017]      FIG. 3  depicts a side cutaway view of an encoding dart having pins, a sleeve, a tumbler, and dogs. 
           [0018]      FIG. 4  depicts a layer of the encoding dart where a portion of the sleeve has been cut away allowing the tumbler to be shown prior to rotation. 
           [0019]      FIG. 5  is a side cutaway view of a pin section engaged with a key section. 
           [0020]      FIG. 6  is a side view of an encoding dart within a tubular having a key section. 
           [0021]      FIG. 7  is a side view of an encoding dart engaged with a sliding sleeve within a tubular. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The description that follows includes exemplary apparatus, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details. 
         [0023]      FIG. 1  depicts a completion where a wellbore  10  has been drilled through one or more formation zones  22 ,  24 , and  26 . A tubular assembly  12 , consisting of casing joints, couplings, annular packers  32 ,  34 ,  36 , and  38 , sliding sleeves  42 ,  44 , and  46 , seats  70 ,  72 , and  74 , and keys  76 ,  78 , and  80  have been run into the wellbore  10 . The seats  70 ,  72 , and  74  are initially pinned in place in the closed position by shear pins  62 ,  64 , and  66 . The well  10 , if it is a horizontal or at least non-vertical well, may have a heel  30  and at its lower end will have a toe  40 . Typically the casing assembly  12  is made up on the surface  20  and is then lowered into the wellbore  10  by the rig  30  until the desired depth is reached so that sliding sleeves  42 ,  44 , and  46  are adjacent formation zones  22 ,  24 , and  26 . The annular packers are arranged along the tubular assembly so that annular packer  32  is placed below formation zone  22  and annular packer  34  is placed above formation zone  22  and both annular packers  32  and  34  actuated to isolate formation zone  22  from all of the zones in the well  10 . Annular packer  34  is placed so that while it is above formation zone  22  it is below formation zone  24  and annular packer  36  is placed above formation zone  24  and both annular packers  34  and  36  are actuated to isolate formation zone  24  from all other zones in the well  10 . Annular packer  36  is placed so that while it is above formation zone  24  it is below formation zone  26  and annular packer  38  is placed above formation zone  26  and both annular packers  36  and  38  are actuated to isolate formation zone  26  from all other zones in the well  10 . In certain instances formation isolation will be accomplished by pumping cement out of the toe  40  of tubular assembly  12  and backup the annular region  58  between the wellbore  10  and the tubular assembly  12 . 
         [0024]      FIG. 2  depicts the wellbore  10  and the tubular assembly  12  from  FIG. 1  with an encoded dart  90  deployed therein. Encoded dart  90  is initially pumped into the wellbore  10  with an encoded lock that matches the key at or above the location of the tool such as sliding sleeve  42  that the operator desires to actuate or in the case of sliding sleeve  42 , to open. The encoded dart  90 &#39;s dog&#39;s  102  and  108  are locked radially outward after the locking pins such as pin  104  and  106  have found the corresponding key  80 . References to specific portions of the encoding dart  90  may be more readily seen in  FIGS. 3, 4, and 5 . As shown in  FIG. 2  the encoding dart  90  would have passed through key  76  and key  78 . However in this instance the key sequence in each of keys  76  and  78  would not match the pin sequence required to unlock the tumbler within encoding dart  90  which would, in turn, extend locking dogs  102  into the radially extended position. 
         [0025]      FIG. 3  depicts an encoding dart  100  having a sleeve  122  and a tumbler  120 . Within the sleeve  122  are a number of pins such as pins  124  and  126 . As shown in  FIG. 3  encoding dart  100  has a second set of pins such as pins  128  and  130  that are 180° offset from the first set of pins such as pins  124  and  126 . While the second set of pins are shown to be offset from the first set of pins by 180° a second set of pins are neither necessary nor are they limited to two sets of pins offset at 180° from one another. Additionally the first set of pins such as pins  124  and  126  are indicated to be dimensionally similar to the second set of pins  128  and  130 . It is envisioned that in certain instances pins that are dimensionally dissimilar may be used in the event that more codes are required. As can be seen pin  124  has a barrel  132  that resides within port  136  in sleeve  122 . Pin  124  also has an extension  138  that protrudes beyond retaining sleeve  140 . Barrel  132  has a larger diameter than extension  138  such that where barrel  132  and extension  138  meet a shoulder  142  is formed. Shoulder  142  abuts retaining plate  140  thereby retaining pin  124  within port  136 . Pin  126  has a barrel  144  the length  146  of barrel  144  is less than the length  148  of barrel  132  of pin  124  such that each pin  126  and  124  must be moved radially inward differing amounts in order align the base of each pin with the interface between the tumbler and sleeve. Pin  124  has a base  150  while pin  126  has a base  152 . 
         [0026]    The tumbler  120  has a series of ports such as ports  160  and  162  within tumbler  120 . Within port  160  is a follower  164  that is forced radially outward by biasing device  166 , in this case a spring, such that face  168  of follower  164  abuts base  150  of pin  124 . Sleeve  122  and tumbler  120  have an interface  170  that extends the length of the pin section of sleeve  122  and tumbler  120 . 
         [0027]    In use, the encoding dart  100  will pass through a key. With the encoding dart  100  in position within the key each of the pins such as pins  124  and  126  may be pushed radially inward. When each of the keys press their corresponding pins radially inward in the amount required to align the interface between the follower such as follower  164  and the base  150  of pin  124  with the interface  170  between tumbler  120  and sleeve  122  the tumbler  120  is allowed to rotate within sleeve  122 . The variations in the length of each base such as the length  148  of base  132  of pin  124  and the length  146  of the base  144  of pin  126  cause each pin  124  and  126  to move radially inward in differing amounts in order to align the interface between the followers and bases with the interface  170  between the tumbler  120  in the sleeve  122 . For instance as depicted in  FIG. 3  the interface between the base  150  and follower  164  is aligned with the interface  170  when the pin  124  is in its fully extended condition as shown. Therefore moving pin  124  radially inward will cause barrel  132  to move into the interface  170  preventing tumbler  120  from rotating within sleeve  122 . However pin  126  must be forced radially inward some distance (as shown) in order to cause the interface between base  152  and follower  153  to align with the interface  170  between tumbler  120  and sleeve  122 . When follower  153  is forced radially outward by biasing device  162  such that shoulder  163  abuts retaining plate  140  the follower  153  is moved into the interface  170  thereby preventing tumbler  120  from rotating within sleeve  122 . 
         [0028]    Encoding dart  100  has a leading edge  172  and a trailing edge  174 . A first anti-rotation device  176 , such as a castellation, is at the leading edge  172  of encoding dart  100  while a second anti-rotation device  178  is at the trailing edge  174  of encoding dart  100 . The first anti-rotation device  176  is provided such that in the event the encoding dart is milled out as the encoding dart  100  is forced all words the anti-rotation device  176  is non-uniform allowing it to resist rotation. The second anti-rotation device  178  is provided in the event that multiple encoding darts or other tools must be milled out the non-uniform profile allows a trailing tool to resist rotation. 
         [0029]    The tumbler  120  has a first axle  180  and the second axle  182 . In this case axle  182  is formed integrally with tumbler  120  while axle  180  is a separate pin. The axles  180  and  182  allow the tumbler  122  to rotate. The tumbler  120  has a forward section  184  that extends axially beyond dogs  186  and  188 . The forward section  184  is formed as a cam so that as tumbler  120  rotates 90° about axles  180  and  182  dogs  186  and  188  are forced radially outward and as long as tumbler  120  remains rotated 90° from its initial condition dogs  186  and  188  are locked radially outwards. 
         [0030]    Encoding dart  100  has at least one ring  190 . The ring  190  extends throughout the circumference of encoding dart  100 . The ring  190  forms a seal with the tool or the adjacent wellbore where the encoding dart  100  lands. The ring  190  may be an elastomeric seal, a metallic seal, a combination of overlapping rings, or any other compatible sealing device. Encoding dart  100  may also incorporate a drag mechanism such as drag mechanism  192 . In this instance drag mechanism  192  is a semirigid plate that interacts with the internal diameter of the bore through which encoding dart  100  passes to slow but not stop the encoding dart as the dart moves through the wellbore. 
         [0031]      FIG. 4  depicts a layer of the encoding dart  100  where a portion of the sleeve  122  has been cut away but the tumbler  120  is shown to be solid but prior to rotation. Upon the alignment of the interface between the pin base and follower with the interface  170  between the tumbler  120  and the sleeve  122  a rotationally directed biasing device such as a torsional spring (not shown) rotates the tumbler  120  by about 90°. While a 90° rotation is preferred it is not necessary and other rotation angles may be used. The rotation may be stopped by set screw  200  abutting a portion of the sleeve  122  while the tumbler is held in its rotated position by the torsional spring. In other instances other rotational locking mechanisms may be used for instance the tumbler may incorporate an interior port having a pin within the port biased radially outward where upon rotation of the tumbler the tumbler port aligns with the recess in the sleeve allowing the biased pin to extend partway out of the port and into the recess thereby locking the tumbler against further rotation in any direction. 
         [0032]    The tumbler  120  has a flat surface  196  formed so that after rotation of the tumbler  120  depends such as pin  124  and pin  130  have sufficient clearance within the encoding dart to retract preventing the most radially outward portion of the pins such as pin  124  and pin  130  from extending beyond the outer circumference of the encoding dart  100 . Upon rotation the tumbler cams, such as tumbler cam  198 , will rotate, in this instance 90°, the dogs  188   186  are forced radially outward. 
         [0033]      FIG. 5  depicts a lock or pin section  210  interacting with the key section  212 . In this instance it can be seen that while most of the pins such as pins  216 ,  218 ,  220 ,  222 ,  224 ,  226 , and  228  are in position to allow rotation of the tumbler  2032  within sleeve  234  where the interface between the base and follower of each pin are aligned with the interface  230  between the tumbler  232  and sleeve  234 . However protrusion  236  of key section  212  prevents pin  214  from extending radially outward such that base  238  has forced follower  240  radially inward and that at least a portion of base  238  extends radially inward at least partially within port  242  in tumbler  232  causing base  238  to be partially within tumbler  232  and partially within sleeve  234  bridging interface  232  thereby preventing rotation of tumbler  232  within sleeve  234 . Additionally protrusion  244  of key section  212  allows pin  246  to extend radially outward. As pin  246  moves radially outward to contact protrusion  244  or such that shoulder  248  abuts retaining plate  250  follower  252  is forced radially outward by spring  254 . As follower  252  moves radially outward from port  256  within tumbler  232  into port  258  within sleeve  234  a portion of follower  252  is within both sleeve  234  and tumbler  232  bridging the interface  230  such that tumbler  232  is prevented from rotating within sleeve  234 . 
         [0034]    Pin  214  has a length  260  while pin  216  has a length  262  where length  260  is greater than length  262 . Generally it is the variation in the length of each of the pins that determines whether the key should force the pin radially inward or allow the pin to extend in order to align the interface between each pins base and follower with the interface between the tumbler and the sleeve in order to allow the tumbler to rotate. In the current embodiment each protrusion on the key section  212  in combination with the length of each pin in the pin section is adjusted such that there are only two positions for each pin but as can be readily seen by varying the protrusion height in combination with the overall pin length there are many various combinations that would allow the interface between the base of the pin and its corresponding follower to align with the interface between the tumbler and the sleeve. In certain instances it is been found preferable to vary the length of each pin by changing only the length of the base. Each of the pins such as pin  220  has a small chamfer  266  and each follower such as follower  268  has a chamfer portion  270 . The chamfers  266  and  270  provide some margin of error such the interface between the base of pin  220  and follower  268  does not have to align exactly with the interface  230  between tumbler  232  and sleeve  234 . In other embodiments the ports such as port  258  and port  256  may be chamfered at the interface  230  and in some instances the follower, the base, and each port may be chamfered. 
         [0035]      FIG. 6  depicts an embodiment of the encoding dart  300  within a section of tubular  302  section of tubular incorporates a key section  304  having a number of circumferential protrusions such as protrusion  306 ,  324 , and  308  the encoding dart  308  has a leading edge having a castellation  310 , a drag section  312 , a dog  314 , and a pin section  316  having pins such as pins  318 ,  320 ,  322 , and  326 . As depicted the key section  304  is fully engaged with the pin section  316  where protrusion  308  pushes pin  322  radially inward, protrusion  306  pushes pin  320  radially inward, and protrusion  324  allows pin  326  to extend radially outward. As dog  314  is radially extended key section  304  matched the lock of pin section  316  to allow the internal tumbler (not shown) to push the dog  314  radially outward and lock it into place. 
         [0036]      FIG. 7  depicts a tubular section  400  having a sliding sleeve  402  within the tubular section  400 . The encoding dart  300  from  FIG. 6  is shown after the encoding dart  300  has progressed out of the key section of tubular  302  and has moved into tubular section  400  such that dogs  314  engage with a portion  404  of sleeve  402 . The ceiling portion  408  of the encoding dart  300  seals on portion  404  of sleeve  402 . With the seal formed across the internal bore of the tubular at seal  408  differential pressure provided from the surface exerts a pressure across the encoding dart  300  to force the sleeve  402  downwards thereby exposing ports  410  and  412 . With the board blocked and the ports  410  and  412  open a formation adjacent the ports  410  and  412  may be fractured. 
         [0037]    Bottom, lower, or downward denotes the end of the well or device away from the surface, including movement away from the surface. Top, upwards, raised, or higher denotes the end of the well or the device towards the surface, including movement towards the surface. While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. 
         [0038]    Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.