Abstract:
A method for assembling a stackable perforating gun system inside a well bore is provided that includes attaching a first gun section of the stackable perforating gun system to a tracking assembly, and transporting the first gun section within the well bore using the tracking assembly. The method also includes disengaging the first gun section from the tracking assembly; retrieving the tracking assembly to the surface; attaching a second gun section of the stackable perforating gun system to the tracking assembly; transporting the second gun section within the well bore using the tracking assembly; and coupling the second gun section with the first gun section using the tracking assembly.

Description:
BACKGROUND 
   1. Field of the Invention 
   Implementations of various technologies described herein generally relate to a stackable gun system for use in a downhole environment, and more particularly, to deploying and retrieving sections of a stackable gun system through a well bore. 
   2. Description of the Related Art 
   The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section. 
   It is often desirable to perforate zones of interest in a subterranean well with very long perforating gun strings to maximize production of well fluids, such as hydrocarbons. This may be particularly true in horizontal or highly deviated wells. Perforating gun strings may range in length from a few hundred feet to several thousand feet. 
   If the perforating gun string is too long to be deployed or retrieved through the well bore in one run, the perforating gun string may be left in the well bore. Leaving the perforating gun string in the well bore may require the creation of a rat hole that is sized to receive the perforating gun string after perforation. This problem may be further exacerbated in highly deviated or horizontal wells. Further, once dropped, the perforating gun string may hinder access to the perforated zone. 
   Alternatively, the perforating gun string may be removed after killing the well following perforation. However, killing the well may have adverse affects on the flow performance of the well once the well is resuscitated into production. 
   SUMMARY 
   In one embodiment, the present invention is a method for assembling a stackable perforating gun system inside a well bore that includes attaching a first gun section of the stackable perforating gun system to a tracking assembly, and transporting the first gun section within the well bore using the tracking assembly. The method also includes disengaging the first gun section from the tracking assembly; retrieving the tracking assembly to the surface; attaching a second gun section of the stackable perforating gun system to the tracking assembly; transporting the second gun section within the well bore using the tracking assembly; and coupling the second gun section with the first gun section using the tracking assembly. 
   In another embodiment, the present invention is a method for assembling a stackable perforating gun system inside a well bore that includes connecting a tracking assembly to a wireline, wherein the tracking assembly comprises a tractor, an anchor and a linear actuator; attaching a first gun section of the stackable perforating gun system to a tracking assembly, and activating the tracking assembly tractor to transport the first gun section within the well bore. The method also includes disengaging the first gun section from the tracking assembly; retrieving the tracking assembly to the surface; attaching a second gun section of the stackable perforating gun system to the tracking assembly; activating the tracking assembly tractor to transport the second gun section within the well bore; and activating the linear actuator to couple the second gun section with the first gun section. 
   The claimed subject matter is not limited to implementations that solve any or all of the noted disadvantages. Further, the summary section is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description section. The summary section is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     It is to be noted that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
       FIG. 1  illustrates a tracking assembly disposed in a horizontal well bore in accordance with implementations of various technologies described herein. 
       FIG. 2  illustrates a flow diagram of a method for assembling a stackable gun system inside a well bore in accordance with implementations of various technologies described herein. 
       FIG. 3  illustrates a flow diagram of a method for disassembling a stackable gun system inside a well bore in accordance with implementations of various technologies described herein. 
   

   DETAILED DESCRIPTION 
   As used here, the terms “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; “upstream” and “downstream”; “above” and “below” and other like terms indicating relative positions above or below a given point or element may be used in connection with implementations of various technologies described herein. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate. 
     FIG. 1  illustrates a tracking assembly  100  disposed in a horizontal well bore  110  in accordance with implementations of various technologies described herein. The well bore  110  may be cased or lined. Although implementations of various technologies described herein are with reference to a horizontal well bore, it should be understood that these implementations may also be performed in a vertical, slightly deviated or highly deviated well bore. The tracking assembly  100  may include a wireline tractor  120 , a wireline  130 , a wireline anchor  140 , a linear actuator  150  and a running or pulling tool  160 . Any type of wireline may be used with the tracking assembly  100 . The wireline  130  may be coupled to the wireline tractor  120 , which may be configured to grip the well bore  100  and push anything attached thereto inside the well bore  100  and pull the wireline  130  behind it. Although the use of the wireline tractor  120  is described herein with reference to a wireline, it should be understood that in some implementations the wireline tractor  120  may be used autonomously, i.e., without a wireline. 
   The wireline tractor  120  may be coupled to the wireline anchor  140 , which may be configured to anchor the tracking assembly  100  and any tool attached thereto to the well bore  110 . The anchor  140  may then be coupled to a linear actuator  150 , which may be actuated to couple or uncouple sections of a stackable gun system, which will be described in the paragraphs below. The linear actuator  150  may be coupled to the running or pulling tool  160 . Any type of running/pulling tool, such as slickline or coiled tubing tool, may be used with the tracking assembly  100 . In one embodiment, actuation of the linear actuator  150  moves the running/pulling tool  160  and any tool attached thereto, without moving the wireline tractor  120  and/or the wireline  130 . Also, the linear actuator  150  may be actuated in either direction along a longitudinal axis of the tracking assembly  100 . 
   The running/pulling tool  160  may be coupled to a stackable gun system  170 , which may be assembled and disassembled downhole. The stackable gun system  170  may be any type of gun system that may be assembled and disassembled down hole, such as one described in commonly assigned U.S. Pat. No. 6,059,042 entitled COMPLETIONS INSERTION AND RETRIEVAL UNDER PRESSURE (CIRP) APPARATUS INCLUDING THE SNAPLOCK CONNECTOR, which is incorporated herein by reference. The stackable gun system  170  may include a number of perforating guns. 
   The stackable gun system  170  may be disposed on a downhole platform  180 , which may be used to support the guns or gun sections during assembly of the gun sections. The downhole platform  180  may be a mechanically releasable anchor (MRA), a bridge plug, a sump packer and the like. In one implementation, an anchor latch adaptor  190  may be disposed between the stackable gun system  170  and the downhole platform  180 . In another implementation, the anchor latch adaptor  190  may be an integral component of the downhole platform  180 . 
     FIG. 2  illustrates a flow diagram of a method  200  for assembling the stackable gun system  170  inside the well bore  110  in accordance with various implementations described herein. At step  210 , the downhole platform  130  may be run into the well bore  110 . The downhole platform  180  may be run into the well bore  110  using a setting device, which may be any standard wireline plug/packer setting device, such as the casing packer setting tool (CPST) tool and the like. Once the downhole platform  180  is set in place (shown in  FIG. 1  as dashed lines), the setting device may be retrieved to the surface (step  220 ) by use of the tracking assembly  100 . In one implementation, the downhole platform  180  may be positioned in the well bore  110  using a self-releasing positioning tool. At step  230 , the anchor latch adaptor  190  may be run into the well bore  110  using the tracking assembly  100  and be set on the downhole platform  180 . 
   In one implementation, the downhole platform  180  and the anchor latch adaptor  190  disposed thereon may be indexed to the well bore  110  by engaging a gyro device with a stackable gun connector therebelow and measuring the relative bearing of the gyro device at the surface. The indexing of the stackable gun connector may then be determined based on the gyro device measurement, thereby enabling the orientation of the stackable gun system  170  with respect to the well bore  110 . The gyro device may be deployed and retrieved in and out of the well bore  110  using the tracking assembly  100 . 
   At step  240 , one or more sections of the stackable gun system  170  may be coupled to (or rigged up with) the tracking assembly  100 . This may be done at the surface At step  245 , the one or more sections of the stackable gun system  170  may be run into the well bore  110  using the tracking assembly  100  until the stackable gun section(s)  170  are supported by and/or connected to the downhole platform  180 . 
   In one embodiment, at step  245  the wireline tractor  120  is activated to transport one or more sections of the stackable gun system  170  to a position in proximity to the downhole platform  180 ; the wireline anchor  140  is then activated to anchor the tracking assembly  100  to the well bore  110 ; and the linear actuator  150  is activated to apply a linear force to the gun section(s)  170  in the direction of the platform  180  to connect the gun section(s)  170  to the platform  180 . Alternatively, the wireline tractor  120  may be used to both transport the gun section(s)  170  and to supply the necessary force to connect the gun section(s)  170  to the platform  180 . In one embodiment, the section(s)  170  form a snap fit type of connection both with each other and with the tracking assembly  100  and the platform  180 . 
   At step  250 , a slight over pull may be made on the running/pulling tool  160  to determine whether the tracking assembly  100  has successfully connected the gun section(s)  170  with the anchor latch adaptor  190  and/or the downhole platform  180 . The over pull may be made by pulling on the wireline  130 , such as with a surface winch, or activating the wireline tractor  120  in a direction away from the platform  180 . 
   At step  260 , the tracking assembly  100  is disengaged from the gun section(s)  170  by disengaging the wireline anchor  140  from the wellbore  110  and activating the linear actuator  150  in a direction away from the platform  180 , or by pulling on the wireline  130 , such as with a surface winch. This disengaging step  260  is similar to the over pull step  250  described above, but performed with a larger force, i.e. the force applied at step  260  is sufficient to disengage the tracking assembly  100  from the gun section(s)  170  (i.e. sufficient to overcome the snap fit type connection), while the force applied at step  250  is not sufficient to disengage the tracking assembly  100  from the gun section(s)  170 . 
   At step  270 , the tracking assembly  100  may then be retrieved to the surface by activating the wireline tractor  120  in a direction away from the platform  180 . At step  280 , additional sections of the stackable gun system  170  may be coupled to the tracking assembly  100 ; run into the well bore  110 ; and connected to the other sections of the stackable gun system  170  in the same manner as is described above. In one implementation, the gun sections may be latched to each other by the use of connectors, which are described in more detail in commonly assigned U.S. Pat. No. 6,059,042 entitled COMPLETIONS INSERTION AND RETRIEVAL UNDER PRESSURE (CIRP) APPARATUS INCLUDING THE SNAPLOCK CONNECTOR, which is incorporated herein by reference. 
   One or more sections of the stackable gun system  170  may be retrieved using the tracking assembly  100  at any time during this deployment process. At step  290 , a firing head assembly may be run into the well bore  110  and be stacked on top of the stackable gun system  170 . The firing head assembly may be any type of firing head assembly that may be used inside a well bore, such as a pressure actuated firing head assembly and the like. The firing head assembly may then be used to fire the stackable gun system  170 . 
     FIG. 3  illustrates a flow diagram of a method  300  for disassembling the stackable gun system  170  inside the well bore  110  in accordance with various implementations described herein. The stackable gun system  170  may be disassembled in a manner similar to its assembly inside the well bore  110 . In one embodiment, the firing of the firing head causes the gun sections  170  to disengage from each other, the platform  180  and the firing head. 
   At step  310 , the tracking assembly  100  may be run into the well bore  110  and latched to the firing head assembly. At step  320 , the firing head assembly may be retrieved to the surface by the tracking assembly  100 . In one implementation, the wireline anchor  140  and the linear actuator  150  may each be activated to connect the tracking assembly  100  to the firing head. With the firing head already detached from the gun sections  170 , due to the firing of the guns, the firing head may then be retrieved to the surface. At step  330 , the tracking assembly  100  may be run into the well bore  110  and latched to the stackable gun system  170 . At step  340 , the stackable gun assembly  170  may be retrieved to the surface using the tracking assembly  100 . In one implementation, the stackable gun system  170  may be retrieved sections at a time. 
   At step  350 , the tracking assembly  100  may be run into the well bore  110  and latched to the anchor latch adaptor  190  and/or the downhole platform  180 . At step  360 , the anchor latch adaptor  190  may be retrieved to the surface using the tracking assembly  100 . At step  370 , the tracking assembly  100  may be run into the well bore  110  and latched to the downhole platform  180 . At step  380 , the downhole platform  180  may be retrieved to the surface using the tracking assembly  100 . In one embodiment any or all of steps  330 / 340 ,  350 / 360 ,  370 / 380  may be performed as described above from steps  310 / 320 . 
   Implementations of various technologies described herein are with reference to assembling and disassembling a stackable gun system  170  inside the well bore  110 . However, it should be understood that these implementations may also be used to assemble and disassemble other tool strings inside the well bore  110 , such as well bore components, intelligent completion components and the like. 
   While the foregoing is directed to implementations of various technologies, other implementations may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.