seal bodies formed in accordance with the present invention comprise two primary elements : ( 1 ) a base material and ( 2 ) a hydrogel . the term “ seal ” as used herein means any apparatus or means for preventing , or significantly limiting , material transport from a particular wellbore zone or region of a formation , to another isolated zone within the wellbore , unless otherwise indicated of clear from the context in which it is used . the terms “ seal body ”, or “ seal bodies ”, means a physical structure placed in a wellbore for forming a seal in the wellbore once exposed to a particular external stimulus ( factors , parameters ) or combination of stimuli . the respective ratios of base material and hydrogel in the composition forming the seal body is determined the specific nature of the application in which the seal will be used . as previously mentioned , hydrogels can change their swelling behavior upon exposure to an external stimulus , such as ph , temperature , light , and electric field . therefore , factors which may contribute to the selection of a proper ratio of base material to hydrogel may include the temperature to which the seal will be exposed , the ph at which the seal will be used , the nature of any chemicals the seal may come into contact with ( including , for instance , the oil / water ratio ), the differential pressure which the seal must withstand and the electronic environment of the application . any number of these factors may effect the performance of the seal . the base material of the seal body composition is generally selected from any suitable material known in the industry for forming seals . preferably , the base material is a polymer . more preferably , the base material is an elastomer or a thermoplastic . elastomers that are particularly useful in the present invention include nitrile rubber ( nbr ), hydrogenated nitrile rubber ( hnbr ), carboxyl nitrile rubber ( xnbr ), silicone rubber , ethylene - propylene - diene copolymer ( epdm ), fluoroelastomer ( fkm , fepm ) and perfluoroelastomer ( ffkm ). thermoplastics which are particularly useful in the present invention include teflon ®, polyetheretherketone , polypropylene , polystyrene and polyphenylene sulfide . as used herein the term hydrogel is a broad phrase referring in general to a polymer that swells when used in aqueous environment . hydrogel polymers useful in the present invention are preferably formed of a crosslinked polymer network . when this polymer network is exposed or immersed in a suitable solvent , the polymer chains in the network become solvated . in certain cases , crosslinkers may be provided to prevent the complete mixing of the polymer chains and the solvent by providing an elastic restoring force that counters the expansion of the network . the polymer network of the hydrogel may be formed from any suitable polymeric material . in a preferred embodiment , the polymer network is formed from cross - linked polymers including water - soluble methylcellulose , cellulose acetate phthalate , and hydroxypropyl methylcellulose polymers , poly ( ethylene oxide ) polymers , guar and its derivatives , polyacrylamide , polyvinylpyrolidone , polyacrylic acid , polyvinylpyrolidone , oligo maleinate copolymers , oligo maleinate oligomers , allyl maleate oligomers , silicon - based materials , and flouro - silicone based materials . the polymer used to form the hydrogel may also be in a metal complex form . seals described in the present invention comprise a base material , such as a polymer , and a hydrogel . the base material and hydrogel may be combined in any suitable ratio using any suitable method . in a preferred embodiment , polymer / hydrogel blends may be prepared using any of the following methods : ( 1 ) a solution process ; ( 2 ) a mesophase mediated process ; ( 3 ) physical mixing / compounding , ( 4 ) injection or extrusion , ( 5 ) in - situ polymerization or ( 6 ) melt processing . curing methods may be any suitable method , but is preferably thermal curing , microwave radiation or electronic beam radiation . chemical modification , such as branching or grafting , of the hydrogel may be performed prior to manufacturing of polymer / hydrogel blends to achieve optimum dispersion of the hydrogel polymer . in - situ polymerization can mean polymerization of monomers or oligomers forming the polymer , hydrogel , or both , where the polymerization occurs simultaneous with the mixing of the base material and hydrogel , simultaneous to the formation of the seal body , or simultaneous with both processes . weight ratios of hydrogel to base material include any suitable amount of hydrogel to form a seal body with good swelling and resetting properties . preferably , the ratio of hydrogel to base material is from about 10 to about 90 parts by weight hydrogel based upon 100 parts of base material . more preferably , the ratio of hydrogel to base material is from about 20 to about 70 parts by weight hydrogel based upon 100 parts of base material any other materials useful in forming seal bodies known to those of skill in the art may be included . examples of such materials include , but are not necessarily limited to , carbon black powder reinforcement , surfactants , catalysts , and the like . without limiting the scope of the invention , the following examples show specific seal body configurations which may particularly benefit from the incorporation or inclusion of hydrogel in the seal body material . fig1 shows three - piece rubber element array or packer element 10 , such as that commonly used in downhole packers . the packer elements are external packer seal bodies that seal the annulus space between tubing and casing ( not shown ). elements are energized by axial deflection of the seal bodies after the packer is run into the hole . commonly used packer elements typically consist of backup end rings 16 and a center seal or element 18 . the center seal 18 typically includes a ring 20 which establishes the inner diameter of the seal . hydrogel may be included or incorporated into any or all of the seal body elements . the hydrogel allows the seal bodies to be energized in response to external stimuli , as previously described . fig2 shows a garter spring element array 50 . the array 50 includes a main element or seal body 52 , a garter spring 54 and backup end rings 56 . the array also includes an id ring 58 . hydrogel may be included in any or all of the seal bodies of the array . as with the assembly of fig1 , the garter spring array also benefits from the inclusion of hydrogel seal body components by allowing them to respond to external stimuli . fig3 shows yet another packer element array 100 . this array includes a main seal body 70 , backup seal bodies 72 and an id ring 74 . as with the seal bodies shown in fig1 and 2 , hydrogel may be included in any or all of the seal bodies . o - rings are simple bi - directional static seal bodies . for high temperature and / or high pressure sealing applications , backup rings are used to prevent o - ring extrusion . as shown in fig4 , the o - ring 150 includes two backup rings 152 which are formed of thermoplastic materials blended with hydrogel polymer . the o - ring may also be formed of elastomers blended with hydrogel polymer . in this application , the hydrogel is able to seal off potential leak paths as well as keep the o - ring energized via swelling . these characteristics are not achievable with existing conventional rubber materials used for o - ring applications . t - seal bodies are typically used as reciprocating bi - directional dynamic seals . as shown in fig5 , t - seal 200 including seal body 202 and retaining ring 204 . the seal body is formed of a hydrogel modified thermoplastic or elastomer . hydrogel can seal off potential leak paths as well as keep the t - seal energized via swelling . these benefits are not achievable with existing conventional rubber materials used for t - seal application . vee packing or chevron seal body stacks are multiple seal lip multi - component seal body sets that are energized by differential pressure . seal stacks are also suited to internal dynamic seal applications . most conventional packing stacks are combinations of softer elastomer parts and harder plastic parts . the incorporation of hydrogel in the seal elements allows any potential leak paths to be sealed , as well as keeping seal body stacks energized via swelling . this is not achievable with existing conventional rubber materials used for seal body stack applications . fig6 shows a seal body stack 250 having first hydrogel / elastomer elements 252 and second hydrogel / plastic elements 254 . these first and second elements are preferably alternating , as shown . however , depending on the specific nature of the application any configuration of first and second elements may be used . spring - energized seals are uni - directional seals and may be either static or dynamic . these seals combine the benefits of packing , as seen in vee or chevron seals and radial compression as seen in o - rings . as shown in fig7 , a spring - energized seal 300 will be made of hydrogel modified thermoplastic or rubber materials . hydrogel can seal off potential leak path as well as keep seal energized via swelling which is not achievable with existing conventional rubber materials used for seal application . examples 6 through 16 below illustrate useful compositions for forming some seal bodies comprising a hydrogel and a base material ( i . e . rubber ) according to the invention . in the examples below , . hydrogel / rubber mixtures are unfilled and filled with carbon black powder and based on therban ® 3446 hydrated nitrile butadiene rubber . the hydrogels used in examples 6 to 11 are based upon polyvinylpyrrolidone k 90 . examples 12 to 16 use a hydrogel composed of monomers which polymerized in situ during the formation of the seal composition , where the monomers are maleinate oligomers and allyl maleate oligomers with polar links content of 65 %. testing methods and parameters used to evaluate properties of the seal compositions were as follows : strength , relative elongation , and residual elongation were determined using astm test d412 at 23 ° c . in air medium ; shore a hardness was tested per astm test d2240 at 23 ° c . in air medium ; change of mass after swelling in liquid media was evaluated according to astm test d624 using a 2 % by wt nacl / 25 % by wt cacl 2 water solution at temperature of 90 ° c . ingredients ex . 6 ex . 7 ex . 8 ex . 9 ex . 10 ex . 11 all ingredient amounts are given in parts by weight : therban ® 3446 ( hnbr ) 100 100 100 100 100 100 ( hydrogenated acrylonitrile - butadiene rubber available from lanxess ag ) polyvinylpyrrolidone k - 90 hydrogel — 50 50 20 30 40 ( available from brainerd chemical company , inc ., tulsa , ok 74106 ) thiuram d dithiocarbamate — — 1 . 7 1 . 7 1 . 7 1 . 7 carbon black reinforcement — — 50 50 50 50 vulcanization time @ 151 ° c . 20 ′ 40 ′ 40 ′ 40 ′ 40 ′ 40 ′ tested properties approx . strength , mpa 9 . 9 4 . 2 11 17 14 . 3 11 . 9 relative elongation , % 535 500 240 320 290 260 residual elongation , % 14 26 15 10 14 12 shore a hardness ( shore a units ) 51 71 90 80 83 85 change of % mass after swelling in 0 . 1 22 . 1 40 . 5 14 . 1 22 . 7 28 . 0 water at 90 ° c . for 10 days ingredients ex . 12 ex . 13 ex . 14 ex . 15 ex . 16 all ingredient amounts are given in parts by weight : therban ® 3446 ( hnbr ) 100 100 100 100 100 ( hydrogenated acrylonitrile - butadiene rubber available from lanxess ag ) perkadox ® catalyst 8 8 8 8 8 copolymer of maleinate oligomers and 30 15 20 30 20 allyl maleate oligomers op - 10 surfactant — — — 2 2 carbon black reinforcement 50 50 50 50 50 vulcanization time @ 151 ° c . 50 ′ 50 ′ 50 ′ 50 ′ 50 ′ tested properties approx . strength , mpa 19 . 7 23 . 2 23 . 6 18 . 4 23 relative elongation , % 430 340 430 420 390 residual elongation , % 17 10 15 18 14 shore a hardness ( shore a units ) 53 62 58 53 60 change of % mass after swelling in 40 . 9 9 . 3 17 . 6 33 . 0 20 . 6 water at 90 ° c . for 10 days the particular embodiments disclosed above are illustrative only , as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein . furthermore , no limitations are intended to the details of construction or design herein shown , other than as described in the claims below . it is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention . accordingly , the protection sought herein is as set forth in the claims below .