Patent Publication Number: US-2010122819-A1

Title: Inserts with Swellable Elastomer Seals for Side Pocket Mandrels

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to devices and methods for forming seals within tubular members. In particular aspects, the invention relates to devices and methods for sealing inserts within a side pocket mandrel. 
     2. Description of the Related Art 
     Gas lift arrangements are used to improve the rate of production of hydrocarbons from a well by enhancing flow through a production tubing string. Gas lift valves are inserts that are typically removably emplaced in side pocket mandrels in a production string. Gas is then injected into the annulus surrounding the production string. The gas is then transmitted by the gas lift valves from the annulus to the flowbore of the production tubing string. Gas lift arrangements are described in U.S. Pat. No. 7,360,602 entitled “Barrier Orifice Valve for Gas Lift” issued to Kritzler et al. and U.S. Pat. No. 6,810,955 entitled Is “Gas Lift Mandrel” issued to Roth et al. These patents are owned by the assignee of the present application and are hereby incorporated by reference. 
     Dummy gas lift valves are inserts that are placed into a gas lift side pocket mandrel to entirely close off flow through the side pocket mandrel. Typically, dummy gas lift valves employ stacks of generally v-shaped elastomeric seals (i.e., v-rings) to form a fluid seal against a surrounding seal bore of the side pocket mandrel. The v-ring seals are energized to seal by differential pressure, which isolates fluid communication through the side pocket mandrel. When the seal bores of the side pocket mandrel get eroded or otherwise damaged, the v-rings are no longer able to fully seal and prevent pressure integrity loss. 
     Other flow control devices are often used within side pocket mandrels, including water flood valves and chemical injection valves. 
     SUMMARY OF THE INVENTION 
     In preferred embodiments, the invention provides improved inserts for use in side pocket mandrels and methods of sealing such inserts within side pocket mandrels. In preferred embodiments, the insert includes an insert body that carries one or more annular sealing elements that are formed of an elastomeric material that swells in response to heat or fluid saturation. When the insert is emplaced within a side pocket mandrel, the swellable elastomer can then be swelled, using either heat or fluid saturation, to cause the sealing element(s) to expand and seal against the seal bore of the side pocket mandrel. In one preferred embodiment, the insert is a dummy gas lift valve which will block fluid flow through the side pocket. In an alternative embodiment, the insert is a gas lift valve which selectively transmits gas from the surrounding annulus into the primary flowbore of the gas lift mandrel. In still other embodiments, the insert is another flow control device, such as a chemical injection valve or a water flood valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein: 
         FIG. 1  is a side, one-quarter cross-sectional view of an exemplary dummy gas lift valve constructed in accordance with the present invention. 
         FIG. 2  is a side, cross-sectional view of an exemplary side pocket mandrel containing a dummy valve constructed in accordance with the present invention. 
         FIG. 3  is a side, cross-sectional view of the side packet mandrel and dummy valve shown in  FIG. 2 , now with the dummy valve having been sealed within. 
         FIG. 4  is a detail cross-sectional view depicting a sealing element in its unexpanded state. 
         FIG. 5  is a detail cross-sectional view depicting the sealing element of  FIG. 4 , now in an expanded state. 
         FIG. 6  is a side, cross-sectional view of an alternative embodiment of the invention incorporating a gas lift valve. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an exemplary dummy gas lift valve  10  that has been constructed in accordance with the present invention. The dummy valve  10  includes a generally cylindrical valve body  12  which is preferably made up of an upper body portion  14  and a lower body portion  16  affixed to one another via a threaded connection  18 . The upper axial end of the valve body  12  presents a threaded portion  20  which permits the dummy valve  10  to be affixed to a running tool. The valve body  12  preferably carries a pair of annular sealing members  22 ,  24  which are fashioned from an elastomeric material. The sealing members  22 ,  24  are preferably formed from an elastomeric material that is physically swellable in response to a particular stimulus. In a currently preferred embodiment, the elastomeric material will swell or expand in response to contact with wellbore fluids, including water and/or hydrocarbon fluids. Elastomeric materials of this type are described in, for example, U.S. Pat. No. 5,384,370 issued to Vondracek et al., entitled “Rubbers Swellable with Water and Aqueous Solutions and the Method for Producing the Same” and U.S. Pat. No. 4,590,227 issued to Nakamura et al., entitled “Water-Swellable Elastomer Composition.” Preferably, the sealing members  22 ,  24  are solid annular rings. In preferred embodiments, the energizing fluid may be a hydrocarbon fluid or water, or a mixture of both, depending upon the particular composition of the sealing element  22 ,  24 . Thus, the sealing members  22 ,  24  can be selectively changed from a first, reduced-size, condition to a second, enlarged size condition. 
       FIGS. 2 and 3  depict a section of an exemplary side pocket mandrel  26  of a type which is well-known in the art. The side pocket mandrel  26  is typically incorporated into a string of production tubing within a wellbore. The mandrel  26  has a mandrel body  28  which defines a primary flowbore  30  therein. The mandrel body  28  includes threaded upper and lower ends (not shown) which permit the mandrel body  28  to be affixed to neighboring sections of a production tubing string in a manner known in the art. A side pocket  34  is also defined within the mandrel body  28  and is generally parallel to and in fluid communication with the primary flowbore  30 . The side pocket  34  preferably includes a pair of cylindrical polished seal bores  38 ,  40  and an enlarged diameter portion  42  disposed between the seal bores  38 ,  40 . Lateral gas injection passages  44  extend through the mandrel body  28  to interconnect the enlarged diameter portion  42  with the radially surrounding annulus  36 . 
     In operation, the dummy valve  10  is inserted into the side pocket  34  using a running tool in a manner known in the art. The dummy valve  10  is moved generally to the position depicted in  FIG. 2  so that the sealing element  22  is located within the seal bore  38  and the sealing element  24  is located within the seal bore  40 . Once the dummy valve  10  is in this position, the sealing elements  22  and  24  are swelled to cause them to expand radially outwardly and into sealing contact with the seal bores  38 ,  40  of the side pocket mandrel  26 . In the event that the seal bores  38 ,  40  have been corroded, eroded or otherwise damaged, the expansion of the sealing members  22 ,  24  will compensate. 
       FIGS. 4 and 5  illustrate in further detail the expansion of the sealing members  22 ,  24  to cause them to seal against the surrounding seal bores  38 ,  40  by illustrating the upper sealing member  22  in greater detail. The exemplary seal bore  38  in  FIGS. 4 and 5  is shown to include a damaged portion  46  which has resulted from erosion or physical impact.  FIG. 4  depicts the sealing member  22  in an initial, unexpanded condition, immediately following the dummy insert  10  having been inserted into the side pocket  34 . Following insertion, the sealing member  22  is activated to move to its expanded condition depicted in  FIG. 5  so that the sealing member  22  expands radially outwardly and against the seal bore  38 . Additionally, the expansion of the sealing member  22  will fill in the damaged portion  46 , as  FIG. 5  illustrates. Typically, an appropriate fluid (water, hydrocarbon, or a mixture thereof) is used in conjunction with the elevated wellbore temperature to expand the sealing members  22 ,  24 . The ambient elevated temperature within the wellbore applies heat to the sealing members  22 ,  24 . In most cases, reservoir fluid containing hydrocarbons and water will be present within the flowbore  30 , the annulus  36  and the side pocket  34  when the insert  10  is inserted into the side pocket  34 . This fluid will act as the swelling fluid that will saturate and will swell the sealing members  22 ,  24 . Preferably also, a swellable elastomer composition is chosen for the sealing members  22 ,  24  to be activated by the reservoir fluid (swelling fluid) within the wellbore. In cases where the reservoir pressure within the wellbore cannot support a fluid level to the insertion depth for the insert  10 , a plug (not shown) could be placed within the flowbore of the production tubing string below the side pocket mandrel  26 . Thereafter, a suitable swelling fluid may be flowed from the surface down through the production tubing string. The swelling fluid will enter the side pocket  34  and saturate the sealing members  22 ,  24  causing them to swell. 
     The inventive sealing concept may also be used in conjunction with standard gas lift valves as well as dummy valve inserts.  FIG. 6  illustrates an alternative embodiment of the invention wherein the gas lift insert is a gas lift valve  48  which can be removably emplaced within a side pocket mandrel to cause gas from the annulus  36  to be transmitted through the side pocket  34  and into the primary flowbore  30  of the side pocket mandrel  26  and, hence, the production tubing string of which the side pocket mandrel  26  is a part. A suitable gas lift valves for use as the gas lift valve  48  include the Model BCO-1™ (J™, C™, CJ™ injection pressure operated gas lift valve which are available commercially from Baker Oil Tools of Houston, Tex. The gas lift valve  48  carries sealing elements  50 ,  52 , which are fashioned from the same swellable elastomeric material as the sealing elements  22 ,  24  described previously. 
     It can be seen that the gas lift inserts  10  and  48  can be used in conjunction with the gas lift mandrel  26  in order to provide a gas lift assembly that can be incorporated into a wellbore production string. The sealing techniques of the present invention may also be used with a number of other inserts that might be used within a side pocket mandrel. For example, swellable sealing elements may be used in conjunction with water flood or chemical injection valves that are emplaced within a side pocket mandrel. 
     The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.