Patent Publication Number: US-7708080-B2

Title: Packer

Description:
This application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/595,338, entitled “PACKER ELEMENT SECONDARY FOLD BACK RING,” which was filed on Jun. 23, 2005, and is hereby incorporated by reference in its entirety. 

   BACKGROUND 
   The invention generally relates to a packer. 
   A packer is a tool that typically is used in a well for purposes of forming an annular seal between the outer surface of a string (a production tubing, for example) and either the surrounding casing or borehole wall, depending on whether the well is cased. The packer typically includes a ring-like elastomer seal element, which is longitudinally compressed by the thimbles, or gages, of the packer to cause the seal element to radially expand to form the annular seal when the packer is set. 
   When compressed, the seal element has a tendency to undergo longitudinal extrusion. Because significant longitudinal extrusion may cause a loss of the annular seal (and potentially a catastrophic blowout), the packer typically includes a seal backup system to limit the extent of the longitudinal extrusion. Ideally, a backup system prevents catastrophic blowout of the elastomer seal element at the well pressure; is fully set with a limited setting force; and allows the packer to be unset (for retrievable packers). It may be challenging for a conventional backup system to accomplish these goals, due to ever-increasing well pressure in the environment in which the packer operates. 
   SUMMARY 
   In an embodiment of the invention, a packer includes a sealing element, a gage and a plurality of foldback rings. The rings are located between the gage and the sealing element. 
   In another embodiment of the invention, a system includes a packer and tubular member, which defines an annulus in the well. The packer is adapted to seal off the annulus in response to the packer being set. The packer includes a sealing element, a gage and a plurality of foldback rings, which are located between the gage and the sealing element. 
   In yet another embodiment of the invention, a technique that is usable with a well includes compressing a sealing element between gages to form an annular seal in the well. The technique includes controlling extrusion of the sealing element, a control that includes deforming a plurality of rings that are located between one of the gages and the sealing element. 
   Advantages and other features of the invention will become apparent from the following drawing, description and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a schematic diagram of a packer before the packer is set according to an embodiment of the invention. 
       FIG. 2  illustrates cross-sectional profiles of foldback rings of the packer according to an embodiment of the invention. 
       FIG. 3  is a schematic diagram depicting a more detailed view of a section of the packer of  FIG. 1  when the packer is set according to an embodiment of the invention. 
       FIG. 4  is a schematic diagram illustrating features of another packer before the packer is set according to another embodiment of the invention. 
       FIG. 5  is a schematic diagram depicting the features of  FIG. 4  when the packer is set according to an embodiment of the invention. 
       FIG. 6  is a schematic diagram depicting features of another packer before the packer is set according to another embodiment of the invention. 
       FIG. 7  is a schematic diagram of a well according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , in accordance with embodiments of the invention, a packer  20  (depicted before being set in  FIG. 1 ) includes a seal element  32 , which may be formed from several elastomer seal rings (seals rings  32   a ,  32   b  and  32   c , depicted as examples). The seal rings  32   a ,  32   b  and  32   c  surround an inner tubular member  24  (which contains the packer&#39;s central passageway) of the packer  20 ; circumscribe a longitudinal axis  62  of the packer  20 ; and are exposed to an annulus  12  that exists between the rings  32   a ,  32   b  and  32   c  and the inner surface of a well casing  10 . It is noted that the seal element  32  may be formed from more or less than three seal rings (one seal ring, for example), depending on the particular embodiment of the invention. The seal element  32  is constructed to be radially expanded when the packer  20  is set to form an annular seal between the outer surface of the tubular member  24  and the interior surface of the casing  10 . For other embodiments of the invention in which the borehole is uncased, the seal element  32  expands (when the packer  20  is set) to form a seal with the surrounding borehole wall. 
   For purposes of compressing the seal element  32  when the packer  20  is set, the packer  20  includes collars, or gages (also called “thimbles”), that slide together to compress the seal element  32 , which is located in between. More specifically, in accordance with some embodiments of the invention, the packer  20  includes upper  35  and lower  36  gages, which longitudinally compress the seal element  32  (when the packer  20  is set) to radially expand the element  32 . In this regard, the packer  20  may include a mandrel (not shown in  FIG. 1 ) that moves when the packer  20  is being set for purposes of moving one or both of the gages  35  and  36  to compress the seal element  32 . 
   For purposes of limiting, if not preventing, the longitudinal extrusion of the seal element  32  when the packer  20  is set, the packer  20  includes a seal backup system, which includes multiple foldback rings between each gage  35 ,  36  and the seal element  32 . More particularly, the seal backup system includes foldback rings  46  and  50  that are concentric with the longitudinal axis  62  of the packer  20  and surround the inner tubular member  24 . Longitudinally, the foldback rings  46  and  50  are located between an upper edge  33  of the seal element  32  and the upper gage  35 . The seal backup system also includes foldback rings  48  and  52  that are concentric with the longitudinal axis  62 ; surround the tubular member  24 ; and are longitudinally located between a lower edge  34  of the seal element  32  and the lower gage  36 . 
   The foldback rings  46  and  48 , which are located closest to the seal element  32 , are primary foldback rings that generally conform to the profiles of the edges  33  and  34 , respectively; and provide the overall strength to minimize longitudinal extrusion of the seal element  32 . Foldback ring  50  is a secondary foldback ring that forms a buffer between the primary ring  46  and the upper gage  35 ; and likewise, foldback ring  52  is a secondary foldback ring that forms a buffer between the primary foldback ring  48  and the lower gage  36 . As described further below, the secondary foldback rings  50  and  52  allow the seal element  32  to achieve higher pressure ratings without compromising the seal element&#39;s ability to be set or retrieved, because the secondary foldback rings  50  and  52  do not touch the casing  10  when the packer  20  is set. 
   Each of the secondary foldback rings  50  and  52  effectively increases the outer diameter of its associated gage,  35 , 36 , which, in turn, increases the pressure handling capability of the seal element  32 . Furthermore, each secondary foldback ring  50 ,  52  effectively reduces the longitudinal extrusion of the seal element  32  by a minimum of the thickness of the ring  50 ,  52  itself. Additionally, the secondary foldback rings  50  and  52  reduce the stress risers that are applied to the primary foldback rings  46  and  48  by the gages  35  and  36 , as further described below. 
     FIG. 1  depicts features of the packer  20  relevant to the annular seal element  32  and its backup system. However, as can be appreciated by one skilled in the art, the packer  20  may have many additional features, such as slips to secure the packer  20  to the casing  10 , one or more mandrels to activate the slips and move the gages  35  and  36 , etc. 
   As depicted in  FIG. 1 , when the packer  20  is first run downhole and unset, only the outer portion of an inner surface of the secondary foldback ring  50  and  52  touch the adjacent primary foldback ring  46 ,  48 . This arrangement maximizes the moment forces that are applied to the secondary foldback rings  50  and  52  when the packer  20  is set and thus, reduces the overall force that is needed to set the packer  20 . 
   The specific geometries of the primary  48  and secondary  52  foldback rings are illustrated in  FIG. 2 , which is an enhanced view of section  60  of  FIG. 1 . The primary  46  and secondary  50  foldback rings may have similar designs to the primary  48  and secondary  52  foldback rings, in accordance with some embodiments of the invention. Thus, the primary foldback rings  46  and  48  may be identical and the secondary foldback rings  50  and  52  may be identical, in accordance with some embodiments of the invention. 
   Referring to  FIG. 2  in conjunction with  FIG. 1 , the primary foldback ring  48 , in accordance with some embodiments of the invention, generally follows the profile of the lower edge  34  of the seal element  32  when the packer  20  is unset. As shown in  FIG. 2 , the primary foldback ring  48  radially extends between an inner edge  48   d  (closest to the outer surface of the tubular member  24 ) of the ring  48  and an outer edge  48   e  of the ring  48 . In this regard, the primary foldback ring  48  includes three annular sections: a first annular section  48   a , which is radially closest to the tubular member  24  and extends radially away from the longitudinal axis  62  with generally no longitudinal variation; a middle annular section  48   b  that radially extends away from the annular section  48   a  and longitudinally increases at an angle  64 ; and an outer section  48   c  that extends upwardly from the annular section  48   b  and has a generally constant radius with respect to the longitudinal axis  62 . 
   In accordance with some embodiments of the invention, the secondary foldback ring  52  is constructed so that only an outermost edge  52   c  of the ring  52  contacts the primary foldback ring  48  when the packer  20  is unset. For purposes of forming this relationship between the primary  48  and secondary  52  foldback rings, the foldback ring  52  has an inclined section  52   b , which rises at a steeper angle  66  (with respect to the longitudinal axis  62 ) than the section  48   b  of the primary foldback ring  48 . More specifically, in accordance with some embodiments of the invention, the secondary foldback ring  52  radially extends between an innermost edge  52   d  and the outermost edge  52  and includes two annular sections: a first inner annular section  52   a , which closely circumscribes the outer surface of the tubular member  24  ( FIG. 1 ) and generally has no longitudinal variation; and an outer annular section  52   b , which radially extends away from the annular section  52   a  and longitudinally increases at the angle  66 . 
     FIG. 3  generally depicts the detailed section  60  (see  FIG. 1 ) in a state that occurs when the packer  20  is set. In this configuration, the primary  48  and secondary  52  foldback rings are deformed between the seal ring  32   c  (of the seal element  32 ) and lower gage  36 . As shown in  FIG. 3 , in this state, the primary foldback ring  48  bends upwardly at edge  104  to contain the seal element  32 . The secondary foldback ring  52  also bends (at edge  102 ) toward the lower gage  36  due to the contact of an outer upper shoulder  100  of the lower gage  36  with the secondary foldback ring  52 . As shown in  FIG. 3 , in the absence of the second foldback ring  52 , the shoulder  100  of the lower gage  36  is capable of introducing a significant stress riser to the primary foldback ring  48 , which may degrade the pressure rating of the packer  20 . However, the intervening secondary foldback ring  52  serves as a buffer to more evenly distribute the forces on the primary foldback ring  48 , which are caused by the shoulder  100 . Therefore, when the packer  20  is set, the shoulder  100  does not introduce a sharp edge on the primary foldback ring  48 . As a result, the pressure rating of the packer  20  is maximized. Additionally, the secondary foldback ring  48  reduces the extrusion gap of the seal element  32  by effectively increasing the outer diameter of the lower gage  36 . 
   The secondary foldback ring  50  ( FIG. 1 ) performs functions similar to the functions performed by the secondary foldback ring  52 . 
   Other embodiments are within the scope of the appended claims. For example, in accordance with some embodiments of the invention, multiple secondary foldback rings may be used between a gage and the seal element of a packer.  FIG. 4  depicts a detailed section  120  of a packer that includes such features according to another embodiment of the invention. The detailed section  120  illustrates a section similar to the section  60  (see  FIG. 1 ) of the packer  20 . However, this packer includes multiple secondary foldback rings  52 . Due to this arrangement, the seal extrusion gap is further reduced by the thickness of the additional secondary foldback ring  52 , as depicted in  FIG. 5 . 
   Although  FIGS. 4 and 5  depict two identical secondary foldback rings  52  between the gage and the sealing element, it is noted that the secondary foldback rings may have different profiles in accordance with other embodiments of the invention. 
   For example,  FIG. 6  depicts a detailed section  150  of a packer according to another embodiment of the invention. Unlike the packer  20  or the packer in  FIGS. 4 and 5 , this packer includes the secondary foldback ring  52 ; and a secondary foldback ring  160 , which has a different profile. As shown in  FIG. 6 , in accordance with some embodiments of the invention, the secondary foldback ring  160  may be located between the secondary foldback ring  52  and the gage  36 . 
   The secondary foldback ring  160  has the same general two annular section design as the secondary foldback ring  52 . In this regard, the secondary foldback ring  160  includes an inner annular section  160   a , which is generally longitudinally flat and has an inner edge  160   a  that closely circumscribes the outer surface of the tubular member  24 . However, an outer annular section  160   b  of the secondary foldback ring  160  is longitudinally inclined at a greater angle than the outer annular section  52   b  (see  FIG. 2 ) of the secondary foldback ring  52 . Due to this arrangement, the only portion of the secondary foldback ring  160  that touches the secondary foldback ring  52  (before the packer is set) is an outer edge  160   c  of the secondary foldback ring  160 . This maximizes the moment force that is applied to the secondary foldback ring  160  when the packer is set. 
   Other embodiments are within the scope of the appended claims. For example, in accordance with other embodiments of the invention, the packer may have more than two secondary foldback rings between the seal element of the packer and each gage. As another example, in accordance with some embodiments of the invention, some of the secondary foldback rings may be identical and other of the secondary foldback rings may have different profiles (such as outer annular sections that have different longitudinal inclines, for example). Thus, many variations are possible and are within the scope of the appended claims. 
   Referring to  FIG. 7 , in accordance with some embodiments of the invention, the packer  20  (or any of the other packers that are described herein) may be used in a subterranean well  200 . More specifically, the packer  20  may be part of a tubular string, such as a production tubing  220  that extends downhole from the surface of the well. As depicted in  FIG. 7 , the well may include a wellbore  240  that is lined by the casing  10 , although the packer  20  may likewise be used in uncased wellbores in accordance with some embodiments of the invention. Additionally, although  FIG. 7  depicts a vertical wellbore, the packer  20  may be used in lateral wellbores. Furthermore, in accordance with some embodiments of the invention, the packer  20  may be used in a subsea well. Thus, many variations are possible and are within the scope of the appended claims. 
   For the embodiment that is depicted in  FIG. 7 , the production tubing string  220  may include, for example, a circulation or sleeve valve  290  to receive a flow of fluid from a particular production zone  230 . As an example, the production zone  230  may be formed by the firing of a perforating gun  280 , which produces corresponding perforation tunnels  260  into a formation  250  of the zone  230 . Thus, production fluid from the zone  230  may flow into a central passageway  222  of the production tubing  220  and through the central passageway of the tubular member  24  to the surface of the well. 
   Although terms of orientation and direction, such as “upper,” “lower,” etc. have been used in the description herein for purposes of convenience, it is noted that such orientations and directions described herein are not needed to practice the invention. Therefore, in accordance with other embodiments of the invention, the packers that are described herein may be used in other orientations. For example, in accordance with some embodiments of the invention, the gages may move laterally about a lateral tubular member for purposes of compressing a sealing element in between. 
   The packers that are described herein may be a variety of different packers, such as weight set and hydraulically set packers, as just a few examples. 
   While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.