Abstract:
A downhole sealing element includes, a malleable member having at least one closed wall cavity therein positionable downhole in a gap defined between downhole members, and a chemical disposed within the at least one closed wall cavity. The malleable member is deformable to fill variations in a dimension of the gap and the chemical is reactive to form a nonflowable element.

Description:
BACKGROUND 
     Sealing one tubular to another tubular in a downhole wellbore of a hydrocarbon recovery operation is a common task. Metal-to-metal sealing systems have been developed for such seals. Small dimensional deviations in the metal-to-metal contacting surfaces, however, can prevent complete sealing between the two metal surfaces. Systems and methods to permit sealing in the presence of these minor dimensional deviations are well received in the art. 
     BRIEF DESCRIPTION 
     Disclosed herein is a downhole sealing element. The element includes, a malleable member having at least one closed wall cavity therein positionable downhole in a gap defined between downhole members, and a chemical disposed within the at least one closed wall cavity. The malleable member is deformable to fill variations in a dimension of the gap and the chemical is reactive to form a nonflowable element. 
     Further disclosed herein is a method of sealing a downhole gap. The method includes, positioning a malleable sealing element having at least one closed wall cavity therewithin in a gap between downhole members, deforming the malleable sealing element thereby filling variations in a dimension of the gap, and forming a nonflowable element with a chemical housed within at least one of the at least one closed wall cavity. 
     Further disclosed herein is a downhole tubular sealing system. The system includes, a first tubular having a deformable portion positionable downhole within a second tubular, a malleable ring having at least one closed wall cavity therein disposed at the deformable portion, and a chemical disposed within the at least one closed wall cavity being reactive to form a nonflowable element. The malleable ring is deformable to fill a variable radial dimension of an annular gap defined between the deformable portion in a deformed configuration and the second tubular. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a partial cross sectional side view of a downhole sealing element disclosed herein positioned downhole between two tubulars in a sealing configuration; and 
         FIG. 2  depicts a partial cross sectional side view of an alternate downhole sealing element disclosed herein positioned downhole between two tubulars in a sealing configuration. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring to  FIG. 1  an embodiment of a downhole sealing element  10  disclosed herein is illustrated sealing two tubulars  14 ,  18  to one another. The sealing element  10  includes, a malleable ring  22  having a closed cavity  26  therewithin with a chemical  30 , which is flowable and illustrated herein as a liquid, located within the closed cavity  26 . In this embodiment the cavity  26  is continuous around the complete circumferential dimension of the ring  22  similar in fashion to that of a bicycle tire inner tube, for example. Walls  34  of the ring  22  are made of a deformable material such as a polymer or a rubber, for example, such that the ring  22  is conformable to available space, such as the space of an annular gap  38  defined between the two tubulars  14 ,  18 . The annular gap  38  may vary in a radial dimension at different locations around the perimeter thereof. The chemical  30  is free to flow throughout the cavity  26  to redistribute itself within the changing dimensions of the ring  22 . The chemical  30  is reactive in response to specific events or exposure to different substances, as will be discussed below, such that a nonflowable element  42 , such as a solid, forms. Once the nonflowable element  42  is formed, the malleability of the sealing element  10  is reduced and consequently is not easily deformed by pressure, for example. In so doing the sealing element  10  maintains sealing engagement with surfaces  46 ,  50  of the tubulars  14 ,  18 . 
     The sealing element  10  can be sized in relation to the annular gap  38  and radial locating walls  54  so that the volume of the sealing element  10  is about equal to or slightly greater than the volume of the space defined by the annular gap  38  and locating walls  54 . This volumetric relationship will cause the sealing element  10  to exert pressure on the surfaces  46  and  50  to assure it is sealingly engaged therewith. Embodiments wherein the chemical  30  is incompressible can result in significant sealing engagement pressures. 
     In fact, sealing engagement pressures can be selected that result in the walls  34  of the ring  22  rupturing in response to pressures in excess of a burst strength threshold pressure. Upon rupture of the walls  34  the chemical  30  is directly exposed to the downhole environment and can commingle with downhole fluids, such as water, mud and/or oil, for example. As such, the formation of the nonflowable element  42  can be the result of a chemical reaction between the chemical  30  and one of the downhole fluids. Additionally, the chemical  30  can be formulated to volumetrically expand during the nonflowable element  42  forming reaction to further enhance the sealing of the sealing element  10  by increasing the sealing pressures between the element  10  and the surfaces  46  and  50  even further. Examples of chemicals with some of the above properties are found in U.S. Pat. No. 5,942,031 to Cheung and U.S. Pat. No. 4,797,159 to Spangle, the entire contents of which are incorporated herein by reference. 
     Referring to  FIG. 2 , an alternate embodiment of a downhole sealing element  110  is illustrated. The sealing element  110  includes a malleable ring  122  with two closed wall cavities  126  and  128  therewithin. Alternate embodiments may, however, have more than two closed wall cavities. The first cavity  126  has a first chemical  130  housed therein and the second cavity  128  has a second chemical  132  housed therein. A rupturable divider  136  separates the first cavity  126  from the second cavity  128 . Application of stress to the divider  136  causes the divider  136  to rupture thereby permitting commingling of the first chemical  130  with the second chemical  132 . The chemicals  130  and  132  are reactive with one another to form a nonflowable element (not shown) (optionally with volumetric expansion during the reaction). Examples of applicable reactive chemicals are magnesium oxide particle slurry and borate that react to form solid magnesium borate compounds and, sodium carbonate and calcium chloride that react to form solid calcium carbonate. These solids in particular may be well suited to this application since they are inorganic crystals that can tolerate the commonly encountered downhole conditions of high temperatures and high pressures. 
     Although the foregoing embodiments require commingling of chemicals to form the nonflowable element  42 , alternate embodiments may form a nonflowable element without such commingling being required. Such embodiments could use chemicals that form nonflowable elements in response to changes in temperature or pressure, for example. Such an embodiment could rely on the high temperatures or high pressures typically encountered in a downhole environment to initiate the solidification reaction. Yet other embodiments could use chemicals that rely on a specific duration of time to expire before they self-solidify. 
     Referring again to  FIG. 1 , the sealing element  10  is shown herein sealing an inconsistently sized annular gap  38  formed when a radially deformable portion  56  of the tubular  14  is expanded radially outwardly such that each of the locating walls  54  contact the surface  50  of the tubular  18  in at least two places. This situation is due to non-circularity of the inner surface  50  of the tubular  18 , or the non-circularity of the outer surface  46  of the deformable portion  56  or both. Consequently, a radial dimension of the annular gap  38  varies at different locations about the perimeter, as described above. If both the surfaces  46  and  50  were circular, the locating walls  54  could seal directly with the surface  50  negating the need for the sealing element  10 . 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.