Patent Publication Number: US-2005115720-A1

Title: Setting method for coiled tubing run, through tubing bridge plug

Description:
PRIORITY INFORMATION  
      This application claims the benefit of U.S. Provisional Application No. 60/526,214 filed Dec. 2, 2003. 
    
    
     FIELD OF THE INVENTION  
      The field of the invention is high expansion bridge plugs and more particularly those that are run through tubing on coiled tubing and set below the tubing in much larger casing.  
     BACKGROUND OF THE INVENTION  
      Many times during the life of a well certain perforations need to be closed off for a variety of reasons, one of which is that the formation begins to produce water or other contaminants in large quantities. A convenient way to do this is to use a bridge plug. Bridge plugs that are small enough to run through existing tubing and then get set in casing below the tubing can be used to avoid the time and expense of removal of the production tubing from the wellbore. There are several ways to get the bridge plug to the desired position. The faster ways include coiled tubing and electric line. Additionally, rigid tubing stands can be threaded together to deliver the bridge plug. Rigid tubing is a slower process, normally requires the well to be killed and therefore is less economical.  
      Electric line used in combination with a locally set explosive charge can provide the needed force on a small piston area that is necessitated by a through tubing application to get the required amount of setting force to set the bridge plug and release from the setting tool. Such electric line set setting tools can also achieve the very long stroke required to effectively set a through tubing bridge plug in far larger casing. These stroke requirements can reach as long as about 2 meters. However, depending on well depth and trajectory, it may not be possible to advance the bridge plug through the tubing with electric line. In such situations, the coiled tubing alternative is the alternative with the shortest run in time.  
      Another issue with electric line run through tubing bridge plugs is that frequently after the bridge plug is run through tubing and set in casing, cement is delivered on top of the set bridge plug to aid in sealing off the perforations in question. The normal way this cement is delivered is using multiple trips with a slender carrier that is run down to the set bridge plug, where the cement is released. Sometimes 6 or 7 round trips may be required to deliver the requisite volume of cement on top of the bridge plug. This process not only takes time but also introduces other pitfalls in getting the proper cement placement.  
      Coiled tubing also has limitations in an application of a through tubing bridge plug. The pressure that needs to be developed in the coiled tubing at the surface to get the required force to set the packer and release from it could be in the order of 11-15,000 pounds per square inch (PSI). Ordinary coiled tubing is generally limited to about 5,000 PSI maximum working pressure. Special order coiled tubing to take higher pressure can be located in some markets, but its availability is so limited and its cost so prohibitively high so as to make running the bridge plug through tubing not economically worth while. In deviated wellbores, coiled tubing can be effective at delivery of a through tubing bridge plug to the desired location, where an electric line is not workable. The problem is how to get the required setting force with the pressure limitations on generally available types of coiled tubing.  
      The present invention seeks to overcome these shortcomings of coiled tubing for delivery and set of through tubing bridge plugs and other downhole tools that require high forces to set. One solution offered by the present invention is to place a pressure amplifier adjacent the through tubing bridge plug so that lower pressures at the surface can set the tool downhole. While this solution has possibilities, it also brings about additional issues of having to configure amplifiers for particular applications and, as a result, requires technicians with greater skills than may be available at a well site when the bridge plug is run. Additionally, incorporating a pressure booster also ads cost in a situation where the additional cost may make running the through tubing bridge plug not economically feasible. Accordingly, in a preferred embodiment of the present invention a multi-step setting process is envisioned. It begins with hydraulic pressure applied through the tubing to initiate the set and is followed by a pulling force to continue the process. Where pulling alone will not result in a sufficient setting force, tools such as jars or impact hammers can be tripped with the pulling force applied to the coiled tubing to enhance the setting force. Those skilled in the art will more readily appreciate these and other aspects of the present invention by a review of the description of the preferred embodiment, the drawings and the claims, which appear below.  
     SUMMARY OF THE INVENTION  
      A through tubing downhole tool, such as a bridge plug is delivered on coiled tubing. The setting process entails an initial pressurization to anchor the tool and compress its sealing element. The remainder of the needed force for setting the tool can come from an upward pull on the coiled tubing. Should more force than can be delivered from a pull on the coiled tubing be required to finish the setting and releasing process from the downhole tool, a jar or impact tool can be incorporated to boost the applied uphole force that is delivered from the pull on the coiled tubing at the surface. Alternatively, a pressure amplifier can be fitted to the coiled tubing so that a smaller pressure applied to the coiled tubing at the surface can deliver the required force to set and release from the downhole tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a part section view of a bridge plug during the run in and after it has exited the tubing in the wellbore;  
       FIG. 2  is the view of  FIG. 1  in the set position;  
       FIG. 3  is similar to  FIG. 1  except an impact device is added to increase the setting force that results from an upward pull on the coiled tubing; and  
       FIG. 4  is the view of  FIG. 3  in the set position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 1  the bridge plug  10  is in the run in position. Anchor linkage  12  is in the collapsed position and element  14  is at its smallest diameter. An actuating rod  16  extends through element  14  and anchor linkage  12  to a hydraulically operated setting tool  18 . The setting tool  18  is operated by pressure applied to coiled tubing  20 . Such applied pressure provides an uphole force to move rod  16  in the uphole direction. As shown in  FIG. 2 , this initial pressure applied through coiled tubing  20  causes the anchor linkage to get shorter in length and larger in diameter until it makes contact with the casing or wellbore (not shown). In the  FIG. 2  position with the anchor linkage  12  providing resistance, further upward movement of rod  16  responsive to applied pressure in coiled tubing  20  will compress the element  14  as well as the petal type backup rings  22  and  24 . However, the pressure in coiled tubing  20  is not sufficient to complete the setting process and break the link  26  on rod  16  to allow removal of the settling tool  18 . To fully set the tool  10 , surface personnel can apply a pulling force within the limits of the coiled tubing  20  to set the bridge plug  10  and break the link  26 .  
      In some applications the combination of pressure, in the order of about 500-1000 PSI, combined with pulling of the coiled tubing will not be enough force to set the bridge plug  10  and break the link  26 . In that case, as shown in  FIGS. 3 and 4  another device responsive to the pull force on coiled tubing  20  or responsive to a combination of pull force and fluid flow from pumping can be mounted to the coiled tubing  20 , so as to enhance the uphole-applied force to the bridge plug  10  to allow it to fully set. This device  28  can be an impact hammer tool or any one of a variety of known jar tools some of which are used in fishing operations.  
      An alternative way to set the bridge plug  10  is to insert a pressure amplifier in the location where the tool  28  is shown in  FIGS. 3 and 4  and to apply pressure into the coiled tubing  20  to a pressure within its normal working pressure and boost that pressure with the amplifier sufficiently to get the needed force on setting rod  16 .  
      Those skilled in the art will appreciate that a variety of downhole tools, apart from bridge plugs, can be set using the techniques described above. In situations where well conditions do not permit electric line delivery and where through tubing is the preferred technique, the methods of the present invention allow for delivery of required setting and release forces applied to a running tool while making use of the tensile capabilities of the coiled tubing. The incorporation of force enhancing devices to the coiled tubing further broadens the spectrum of applications where a greater setting force could be required. Alternatively, pressure amplifiers can be used with coiled tubing to deliver a setting pressure at the running tool that is well in excess of the capabilities of the surface equipment and the coiled tubing itself. While rigid tubing can be used, coiled tubing is preferred because it is much more economical to run in a through tubing application. The present invention is not limited to through tubing applications, but the greatest economies can be achieved by using the methods of the present invention in such applications.  
      The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: