Patent Abstract:
A swellable system reactive to a flow of fluid including an article having a swellable material operatively arranged to swell upon exposure to a flow of fluid containing ions therein. A filter material is disposed with the swellable material and operatively arranged to remove the ions from the flow of fluid before exposure to the swellable material.

Full Description:
CROSS REFERENCE 
       [0001]    This application is a continuation-in-part of U.S. Non-provisional application Ser. No. 13/211,817 filed on Aug. 17, 2011. The parent application is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    Isolation of downhole environments depends on the deployment of a downhole tool that effectively seals the entirety of the borehole or a portion thereof, for example, an annulus between a casing wall and production tube. Swellable packers, for example, are particularly useful in that they automatically expand to fill the cross-sectional area of a borehole in response to one or more downhole fluids. Consequently, swellable packers can be placed in borehole locations that have a smaller inner diameter than the cross-sectional area of the fully expanded swellable packer. However, certain downhole conditions, such as the presence of monovalent and polyvalent cations (e.g., Ca 2+ , Zn 2+ , etc.) in the aqueous downhole fluids contacting the swellable packer, tend to decrease both the amount of swelling and the rate at which the packer swells, and may also accelerate degradation of the packer. In order to overcome these issues and to continually improve upon swelling efficiency under a variety of conditions, the industry is always desirous of new and alternate swelling systems. 
       SUMMARY 
       [0003]    A swellable system reactive to a flow of fluid, including an article including a swellable material operatively arranged to swell upon exposure to a flow of fluid, the flow of fluid containing ions therein; and a filter material disposed with the swellable material and operatively arranged to remove the ions from the flow of fluid before exposure to the swellable material. 
         [0004]    A method of operating a swellable system including filtering ions from a flow of fluid with a filter material; and swelling a swellable material responsive to the flow of fluid upon exposure to the fluid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0006]      FIG. 1  is a cross-sectional view of a swellable article in an initial configuration; 
           [0007]      FIG. 2  is a cross-sectional view of the swellable article of  FIG. 1  in a swelled configuration; 
           [0008]      FIG. 3  is a swellable system according to an embodiment disclosed herein where a swellable article is disposed with a filter material in a shell covering a swellable core; and 
           [0009]      FIG. 4  is a swellable system according to another embodiment disclosed herein where a filter material is separately disposed from a swellable article. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    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. 
         [0011]    Referring now to  FIG. 1 , a system  10  including a tubular or string  12  and a downhole article  14 , e.g., a packer or sealing element, disposed thereon is illustrated. The downhole article  14  includes, for example, a base composition and a filter component, discussed in more detail below. The base composition comprises an elastomeric material and/or an absorbent material. Due to fluid absorption by the absorbent material, e.g. absorption of water, brine, hydrocarbons, etc., the article  14  expands or swells to a second configuration shown in  FIG. 2 . Various absorbent materials are known and used in the art. For example, with respect to water swellable embodiments any so-called Super Absorbent Polymer could be used, or those marketed by Nippon Shokubai Co., Ltd. under the name AQUALIC® CS-6S. The elastomeric material is included, for example, to provide a seal against a downhole structure  16 , e.g., a borehole in a subterranean formation  18 , shown in  FIG. 2 . Of course, the structure  16  could be any other tubing, casing, liner, etc. located downhole and engagable by the article  14 . The elastomeric material could be any swellable or non-swellable material. In some embodiments, the elastomeric material is absorbent with respect to one or more downhole fluids thus also encompassing the absorbent material. In this way, for example, the article  14  can be run-in having an initially radially compressed configuration, exposed to fluids once located downhole, and expanded to engage between the tubular  12  and the structure  16 . In one embodiment, the structure  16  is isolated by expansion of the article  14  such that fluids (e.g., from the formation  18 ) are substantially prevented from flowing past the article  14  once the article  14  is expanded. 
         [0012]    Downhole fluids typically comprise an aqueous component, which more accurately is a brine containing various ions, e.g., metal cations from dissolved salts. As noted above, monovalent and polyvalent cations can interact with the absorbent material, and decrease the overall rate and ratio of expansion of the absorbent material, thereby hindering the sealing efficacy of the article. It has been generally found that polyvalent cations such as Ca 2+ , Zn 2+ , etc. have a more profound effect on the performance of swellable materials, particularly in water swellable articles, than monovalent cations and are thus usually more desirable to be removed. It is to be appreciated that while water-swellable materials are discussed as an exemplary embodiment that is adversely affected by the presence of cations, other materials may be swellable in response to different fluids and/or adversely affected by anions. For example, in one embodiment the swellable material is adversely affected (e.g., reduced swelling, shorter life span, slower swelling rate, etc.) by the presence of anions. For this reason, the term “ions” as used herein will refer to any cation or anion that has a negative effect on the performance of a corresponding swellable material. 
         [0013]    To mitigate the deleterious effect of such ions on the absorbent material, the filter material acts to remove or filter ions from the downhole fluids before they interact with the swellable material. By remove or filter, it is meant that the filter material captures or holds the ions in, at, or proximate a capture site or location proximate to the filter material, or otherwise neutralizes the ions such that the flow of fluid is at least partially relatively devoid of ions downstream of the filter material. Thus, while the ions are still technically in the fluid, they are prevented from adversely affecting the swelling of the swellable material and therefore considered to be removed or filtered. The removal, filtering, or capture may be done by chemical or physical bonding between the filter material and the ions, physisorption or chemisorption at or by the filter material or a surface thereof, electrostatic and/or van der Waals attraction between the filter material or an atomic structure thereof (e.g., functionalized group) and the ions, etc., examples of which are discussed in more detail below. 
         [0014]    In the embodiment of  FIGS. 1 and 2 , the filter material, the elastomeric material, and/or the absorbent material can all be mixed together, e.g., homogeneously, then formed into the article  14 . An alternate embodiment for a system  22  is shown in  FIG. 3 , the system  22  including an article  24  on a tubular or string  26 . The article  24  is formed from a core  28  and a shell  30 . In this embodiment, the core  28  includes the aforementioned swellable material, while the shell  30  includes the filter material. The core  28  and the shell  30  may both, for example, include suitable elastomeric and/or filler materials to provide sealing for the article  24  and to impart chemical and physical properties to the article  24 . In this way, the flow of fluid to which the swellable material in the core  28  is reactive will first be filtered of ions by the filter material in the shell  30 . 
         [0015]    A system  32  according to another embodiment is shown in  FIG. 4  in which a swellable article  34  is disposed with a tubular or string  36 . In this embodiment, a formation  38  is separated from the article  34  by a radially disposed tubular or string  40 , e.g., a casing, liner, tubing, etc. The tubular/string  40  includes at least one port or opening  42  for enabling a flow of fluid, generally designated by an arrow  44 , to encounter the article  34 . The filter material can be arranged in a plug  46  positioned in the opening  42 , in a membrane or film  48  positioned over the opening  42 , etc. The plug  46  can be formed as any suitable fluid permeable member for creating a passageway for communicating fluid to the swellable material. In this way, the flow of fluid is filtered by the filter material before it reaches the article  34 . The plug  46  and/or the membrane  48  could be formed from any suitable permeable material, e.g., a porous foam, fibers, with the filter material disposed in or with the permeable material, e.g., in pores of the permeable material. 
         [0016]    In another embodiment, essentially a combination of the above, the shell  30  could be a protective or elastomeric shell impermeable to downhole fluids and resistant to corrosion and degradation. A permeable plug, such as discussed with respect to the plug  46  could be included in the shell  30  as opposed the an outer tubular  40 . In this way, the swellable article will benefit from an outer shell made of an elastomeric or other material that can be selected to provide beneficial properties such as corrosion resistance, fluid impermeability, etc., while also maintaining the advantageous ion filtering properties provided by the current invention as discussed herein. 
         [0017]    In one embodiment, the filter material comprises one or more graphene-based compounds. By graphene-based it is meant a compound that includes or is derived from graphene, such as graphene itself, graphite, graphite oxide, graphene oxide, etc. The compounds could take any form used with such graphene-based compounds, such as sheets or nanosheets, particles, flakes, nanotubes, etc. Advantageously, the unique properties of graphene enable effective donor—acceptor interactions between both the anions and the cations and the graphene flakes or particles. The graphene-based materials, associated oxides, or other derivatives or functionalized compounds thereof may contain a corresponding relatively large number of capture sites for attracting and binding ions via van der Waals and/or Coulombic interactions. Of course, other materials with electron-rich surfaces can be used for similarly filtering cations, while highly electron deficient materials may be utilized with respect to anions. 
         [0018]    To further increase the ability of graphene-based filter materials to capture the aforementioned polyvalent cations, the filter materials can be functionalized to include one or more functional groups. The process of forming graphite or graphene oxide, for example, results in the inclusion of various functional groups that are relatively negatively charged (e.g., carboxylic acid groups) or polar (e.g., carbonyl groups). Polyvalent cations will be attracted to and captured by these groups. In one embodiment the filter material is covalently modified with thiol groups according to known diazonium chemistry procedures. Thiol groups are naturally excellent at capturing positively charged ions, notably doubly charged mercury cations, although other metallic cations ions such as the aforementioned Ca 2+ , Zn 2+ , etc., contained in downhole brines will also be readily captured by thiol groups. Other functional groups such as disulfide groups, carboxylic acid, sulfonic acid groups may also be used for their ability to capture polyvalent cations, particularly doubly charged cations. Other functional groups include chelating ligand groups, such as iminodiacetic acid, iminodiacetic acid group, N-[5-amino-1-carboxy-(t-butyl)pentyl]iminodi-t-butylacetate) group, N-(5-amino-1-carboxypentyl)iminodiacetic acid group, N-(5-amino-1-carboxypentyl)iminodiacetic acid tri-t-butyl ester group, aminocaproic nitrilotriacetic acid group, aminocaproic nitrilotriacetic acid tri-tert-butylester group, 2-aminooxyethyliminodiacetic acid group, and others that would be recognized by those of ordinary skill in the art in view of the disclosure herein. 
         [0019]    The graphene-based materials could also be functionalized to filter anions, e.g., with quaternary ammonium, quaternary phosphonium, ternary sulfonium, cyclopropenylium cations, or primary, secondary, ternary amino, or other groups. These groups are either positively charged or become protonated in acidic environments and thus require anions to compensate for the charge. In some situations, the anion can be exchanged with another anion while preserving charge. For example, in one embodiment, the graphene-based material is functionalized with a quaternary ammonium group, the positive charge of which is balanced by hydroxide anions. In this example, in brine containing SO 4   2−  anions, one SO 4   2−  anion will be captured and two hydroxide anions (OH − ) will be released. In an embodiment, a mixture of graphene-based material functionalized with sulfonic acid groups and graphene-based material functionalized with quarternary ammonium groups balanced by hydroxide anions is used to neutralize a CaCl 2  brine. In the cation-exchange process, Ca 2+  cations are captured with a simultaneous release of two H +  ions for each Ca 2+  cation. In the anion-exchange process, Cl −  ions are captured by the quaternary ammonium group with a simultaneous release of OH −  anion for each Cl −  ion. Recombination of released H +  and OH −  ions results in the formation of water molecules, which may contribute to the swelling process of water-swellable materials. 
         [0020]    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.

Technology Classification (CPC): 4