Patent Publication Number: US-2017356269-A1

Title: Composite swellable packer material

Description:
CROSS-REFERENCE TO RELATED CASES 
     This application claims the benefit of U.S. provisional patent application Ser. No. 62/348,467, filed on Jun. 10, 2016, and incorporates such provisional application by reference into this disclosure as if fully set out at this point. 
    
    
     FIELD OF THE INVENTION 
     This disclosure relates to swellable seals in general and, more particularly, to a composite material with controllable swell rates suitable for use as a packer seal. 
     BACKGROUND OF THE INVENTION 
     Annular spaces and other cavities, particularly in downhole and drilling environments may be bifurcated, isolated, sealed, or otherwise divided by a packer. The packer is a mechanical device that may be placed in the appropriate location before being expanded by some means to both remain solidly in place and to seal the bore or other cavity. Other packers are sized appropriately such that they are not expanded after being set in place but fit tightly enough to perform their function. A part of the packer may include a material that reacts with the fluids in the well bore to swell in order to create an effective seal. The total amount of swelling of such a material, as well as the rate of swell, is critical to both proper placement and function of the associated packer. 
     What is needed is a device and composition for a seal that addresses the above, and related, issues. 
     SUMMARY OF THE INVENTION 
     The invention of the present disclosure, in one aspect thereof, comprises a swellable packer element having a composite layer formed from an elastomeric layer backed by a fabric layer. The composite layer is wound to form a seal comprising alternating layers of elastomer and fabric. 
     In some embodiments, the elastomeric layer is backed by the fabric layer having elastomer on an opposite side thereof. The elastomeric layer may be at least partially merged into the fabric layer. The fabric layer may be knit or woven. The elastomeric layer and the fabric layer may be coterminous. The elastomeric may be free of any super absorbent polymers. However, some embodiments comprise a blowing agent contained in the composite layer that is selected to respond with expanding gas products when exposed to predetermined fluids in a well bore 
     The composite layer may be wound about a section of drill pipe or another tool. In some embodiments, a plurality of lengths of composite layer are wound around the section of drill pipe. 
     The invention of the present disclosure, in another aspect thereof, comprises a swellable packer element including an elastomeric material formed into a shape comprising a hollow cylinder and vulcanized, and a fibrous material contained within the elastomeric material that increases the cohesive strength of the elastomeric material. The elastomeric material is selected to swell in contact with a predetermined fluid, and the fibrous material increases transport of fluids into the elastomeric material. 
     In some embodiments, the fibrous material comprises fiber flock mixed into the elastomer before vulcanizing. The fibrous material may also comprise a woven or knit fiber mat. The elastomeric material and the fibrous material may comprise coterminous sheets rolled into a cylinder before vulcanization. The swellable packer may not contain any super absorbent polymers but may include a blowing agent within the elastomeric material. 
     The invention of the present disclosure, in another aspect thereof, comprises a swellable packer element including an elastomeric material formed into a predetermined shape and vulcanized. The packer element of this embodiment includes a blowing agent within the elastomeric material that is selected to produce gas and expand the elastomeric material upon contact with a predetermined fluid. The swellable packer element may include a fiber reinforcement within the elastomeric material but may not include any super absorbent polymer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cutaway view of an exemplary packer in a downhole environment according to aspects of the present disclosure. 
         FIG. 2  is a perspective view of a composite swellable packer according to aspects of the present disclosure. 
         FIG. 3  is a cross section of a packer (unswollen) installed in a well bore according to aspects of the present disclosure. 
         FIG. 4  is a cross section of a multilayer packer according to aspects of the present disclosure. 
         FIG. 5  is a perspective view of a partially unrolled multilayer packer according to aspects of the present disclosure. 
         FIG. 6  is a cross section view of a sheet of composite packer material according to aspects of the present disclosure. 
         FIG. 7  is a perspective view of a completed rolled packer seal wrapped in nylon. 
         FIG. 8  is a perspective view of a packer assembly comprising multiple sealing sections according to aspects of the present disclosure. 
         FIG. 9  is a cross section of fiber reinforced packer according to aspects of the present disclosure. 
         FIG. 10  is a cross section of a cellular rubber packer element according to aspects of the present disclosure. 
         FIG. 11  is a closeup cutaway view of a portion of a swellable packer element according to aspects of the present disclosure. 
         FIG. 12  is a closeup cutaway view of a portion of another swellable packer element according to aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In various embodiments, the present disclosure describes a rubber and fiber composite swellable seal for use as a packer element. The seal may be chemically, water, or salt water expandable and may have a controlled or controllable swell rate that exhibits greater pressure sealing capability than previous seals by generating higher contact sealing forces than otherwise achievable with super absorbent polymers (SAP). For purposes of the present disclosure, an SAP is a polymer one that can absorb and retain extremely large amounts of a liquid relative to its own mass. For example, an SAP may retain from 30 to 60 times its own volume in deionized water. When immersed in a 0.9% saline solution, the absorbency drops to approximately 50 times its weight (in distilled water up to 300 times weight increase). The presence of valence cations impedes bonding with water molecules. Prior packer technology relies on an ethylene oxide elastomer and partially neutralized polyacrylic acid sodium salt, in combination with an elastomeric polymer. Existing swellable packers lack the durability provided by the fabric substrate of the embodiments of the present disclosure described below. For example, during processing, existing materials often crumble and lose cohesive strength. 
     Referring now to  FIG. 1 , a side cutaway view of an exemplary packer in a downhole environment according to aspects of the present disclosure is shown. The environment  100  may include a well or hole  102  bored into earth  104  or other substrate. The hole  102  may or may not already be provided with a casing wall  106  previously placed as is known in the art. An exemplary interior packer  108  or other tool may be placed into the well bore and use to isolate one portion of the well bore  102  from another. In the present example, the packer  108  is placed into the well bore  102  creating an open annulus  110  between the packer  108  and wall  106 . A swellable seal  112  may be provided around the packer  108  and hence occupy part of the annulus  110 . The seal  112  may comprise various compositions as described hereinbelow that react with the environmental fluids (e.g., salt water or brine) to swell against the packer  108  and/or wall  106  to effectively seal off a portion of the bore or hole  102 . 
     A swellable rubber packer seal  112  according to the present disclosure may be initially of a smaller diameter than the internal dimensions of the well casing  106 . In the environment of the well bore the packer is configured to swell until contact is made with the well casing  106 . Thus, sections of the well bore  102  may be isolated from above or below, or from one another, by insertion and swelling of one or more packers. 
     Referring now to  FIG. 2 , a perspective view of a composite swellable packer according to aspects of the present disclosure is shown.  FIG. 2  illustrates the geometry of the packer element or seal  112 . The seal  112  may be longer than wide and have the general shape of a hollow cylinder. The packer seal  112  is not necessarily always longer than wide and therefore could be washer-shaped. Moreover, the seal  112  may alter shape as it swells, and to provide an effective seal may mirror or conform to the shape of the well bore  102 . In some embodiments, either prior to, or after, swelling, the seal  112  may be considered to be toroidal. 
     Referring now to  FIG. 3 , a cross section of a packer installed in a well bore according to aspects of the present disclosure is shown. Here the view is downward into the well bore  102 . The seal  112  is shown here unswollen such that it does not fully contact the well bore  102 . In response to fluids and/or temperature in the down hole environment the seal  112  may grow or expand such that it seals against the well bore  102  (e.g., as shown in  FIG. 1 ). 
     Referring now to  FIG. 4  is a cross section of a multilayer packer seal  400  according to aspects of the present disclosure is shown. The seal  400  may be used in place of the seal  112  discussed above. In the present embodiment, the seal  400  comprises alternating layers of elastomer  402  and fabric sheeting  404 . The layers of elastomer  402  and fabric  404  may be concentric such that a complete ring of elastomer  402  overlays a complete ring of fabric  404  repeatedly through a radial thickness of the seal  400 . In other embodiments, the elastomer  402  is backed by a fabric layer  404  and the two are a continuous composite sheet ( 502 ,  FIG. 5 ) that is rolled up into the completed seal  400 . 
     The fabric layer  404  may be coterminous with the elastomer layer  402  such that the fabric  404  extends completely to the ends (top and bottom) of the seal  400  in order to fully support the elastomer layer  402 . The outer layer of the composite (e.g., the portion of the seal  400  that contacts the well bore  102  or casing  106 ) may be the elastomer layer  402  but this will be backed by the fabric layer  404  throughout the thickness of the seal  400  all the way to the innermost portion thereof. In some embodiments, the final innermost layer may comprise fabric  404  or elastomer  402  for sealing purposes. 
     A fabric-type construction may be a preferred embodiment for use in packer elements for the oil and gas industry due to the manufacturing methods utilized as well as the end-product application where the arrangement of the fabric layer  404  can be used advantageously to increase the radial stiffness of the packer element  400  when expanded within the well casing  106 . The elastomer layer  402  is easily applied to the fabric  404  during construction (or vice versa). The fabric layer  404  may be the primary strength member, rather than the elastomer  402 . In some embodiments, reducing or eliminating the use of SAPs, combined with the layered construction described, results in a much more resilient and stiff structure creating a greater contact sealing force between the outer surface of the packer element and the well casing  106 . 
     The embodiment of  FIG. 2  illustrates an embodiment for a packer element in which the fabric layer is a continuous web of fabric interspersed between layers of elastomer. The fabric provides for mechanical reinforcement of the elastomer. The fabric provides significant resistance to bulging of the elastomer when swollen and in contact with the well casing, thereby significantly increasing the radial stiffness of the packer element. This very high radial stiffness in conjunction with resistance to axial bulging of the elastomer creates a significantly higher contact sealing force between the outer layer of the packer element and the well casing. This increased contact sealing force results in a much higher resistance to leakage and hydraulic pressure enabling packer elements to be utilized at higher differential pressures than previously utilized. 
     Referring now to  FIG. 5  is a perspective view of a partially unrolled multilayer packer sealing element  400  according to aspects of the present disclosures shown. As can be more easily appreciated from  FIG. 5 , the seal  400  may be constructed as a rolled layer of elastomer  402  backed by fabric layer  404 . Together the elastomer layer  402  backed by the fabric layer  404  form a single composite sheet  502  that is rolled up to the desired thickness to create the seal  400 . The fabric layer  404  may be coterminous with the elastomeric layer  402  such that they have the same length and width, and neither the elastomer layer  402  nor the fabric layer  404  extend substantially (or at all) beyond the other. Similarly, the elastomer layer  402  and the fabric layer  404  may both extend the full length and width of the entire composite layer  502  (which is rolled up to create the completed seal  400 ). A completed packer may comprise a pipe or other work string section with the composite layer  503 , which is rolled thereon to the appropriate thickness. 
     The fabric layer  404  may comprise be a natural or synthetic fabric or a mixture. Generally, natural fibers such as cotton provide for more advantageous swelling and absorption profiles compared to synthetic fibers. The cotton fabric may be woven or knitted in construction and may be treated or untreated. Suitable treatments for the fabric may include treatments that enhance the ability of the fabric layer to bond with the elastomer layer  402 . Such treatments may include resorcinol formaldehyde latex (RFL) treatment or other formaldehyde based treatments. Acid treatments may also be utilized. 
     Suitable elastomers for the elastomeric layer  402  of the present disclosure may include various polymers or polymer alloys. A nitrile may be utilized. Styrene-butadiene rubber (SBR), ethylene propylene diene monomer (EPDM), and/or p-Phenylenediamine (PPD) type rubbers may be utilized. The type of rubber utilized may be matched to the conditions under which the packer is expected to be used. Temperatures and desired swell rates may also be considered when an elastomer is selected or formulated. A polymer alloy may be utilized when it is desirable to slow or delay the swelling of the packer (e.g., to provide more time for final placement in the well bore). 
     It should be appreciated that the packers and seals of the present disclosure are operational without incorporation of any SAP. This makes the final product less susceptible to degradation or loss of integrity in the well bore. Preliminary tests indicate the packers constructed according to the present disclosure can maintain pressures up to and beyond 10,000 psi. 
     In some embodiments, the composite layer  502  of the present disclosure is constructed as one layer of elastomer  402  backed by one layer of fabric  404  (or vice versa). In another embodiment, a layer of fabric is faced on both sides with a layer of elastomer and then rolled up creating the composite layer  602  as shown in  FIG. 6 . The composite layer  602  may replace the composite layer  502  according to some embodiments of the present disclosure. Of course, such an embodiment might provide for effectively up to double the thickness of the elastomer layer  402 . In some cases, concerning either composite layer  502  or composite layer  602 , the elastomer may end up partially or completely dispersed into the fabric, particularly when the packer is swollen and under pressure in the well bore. In such case, the demarcation between the fabric and elastomer layers may not be abrupt. In some embodiments, the composite and the fabric may form the same layer once construction is complete. 
     In one embodiment, the fabric  404  thickness is on the order of 0.040″ and the total composite  502  thickness (including the attached elastomer layer  402 ) is around 0.080″. Thus, the composite elastomer/fabric layer  502 / 602  may be rolled many times to construct the packer. The final content of the composite material comprising the packer may be on the order of 25% fiber (in the form of the fabric layer) by weight. It should be understood that the layers of composite fabric (e.g.,  502 ,  602 ) are not shown to scale. 
     As shown in  FIG. 7 , the composite fabric  502  (or  602 ) may be rolled onto the pipe or other implement to the desired, pre-swelling thickness and wrapped in nylon 702. The wrapped material may be autoclaved for bonding purposes and the nylon wrap  702  removed. 
     The final product may be a packer  800  comprising multiple bonded sections. In one embodiment, three 5 foot sections of seals  400  are combined to create a 15 foot packer  800  to be included as part of the work string for placement into the well bore  102 . In other embodiments, the packer may comprise more or fewer sections  400  and the sections  400  may be longer or shorter than 5 feet. 
     Referring now to  FIG. 9 , a cross section of a fiber reinforced packer seal  900  according to aspects of the present disclosure is shown. In the seal  900 , individual fabric fibers are utilized to achieve similar results as the packer seal  400 . In various embodiments, the seal  900  may be substituted for the seal  400 . With the seal  900  of  FIG. 9 , in addition to the mechanical strength improvement gained in the use of fiber reinforcement of the elastomer layer  902 , the fibers also permit fluid in communication with the outer surfaces of the packer element  900  to travel more directly into the elastomer matrix through a “wicking action”. The fibers also act as a strength member providing structural reinforcement of the elastomer matrix while improving the penetration of the fluid on the outside surface of the packer element  900  deep into the elastomer permitting a more controlled and uniform swelling of the elastomer. 
     The packer seal  900  may be constructed by mechanical mixing of the fibers into the rubber prior to curing in an autoclave. As before, a wrap, possibly made of nylon or another material, may be used to contain the rubber/fiber composition during curing. Discrete lengths of packer material of varying lengths may be prepared (possibly onto a pipe or other work string section) and combined to create the final product. The fibers utilized in this embodiment may comprise cotton or another material with wicking capabilities. The fibers may be untreated or they may be treated to increase their propensity for bonding with rubber. The fibers may vary in length but in one embodiment the fibers are a finely prepared flock with fiber lengths on the order of about 75-150 microns. 
     Referring now to  FIG. 10 , a top down cutaway view of a composite swellable packer seal  1000  utilizing blowing agents according to aspects of the present disclosure is shown. In addition to the use of fibers as disclosed with respect to the seal  900 , it has been found that chemical blowing agents can be effectively used to cause expansion or “swelling” of an elastomer  1002  when exposed to various fluids. Chemical blowing agents, which are typically utilized in the manufacture of foam or cellular rubber, can be utilized in elastomeric rubber compounds to produce a packer element  1000  that achieves high contact sealing force and controlled swelling. 
     It has been observed through experimentation and development that the presence of small voids or cells within the molded packer element  1000  permit more controlled expansion of the packer element through a mechanism in which the cells absorb and retain absorbed fluid while the relatively thin cell boundary walls facilitate rapid transport of fluid from the outside surface of the packer element to the inner layers. As outer cells fill with liquid, adjacent empty cells gradually fill with fluid as the osmotic pressure acting across the cell membranes tend to equalize pressure through fluid migration. The cellular structure of the elastomer provides greater available void space for absorption of fluid which causes more significant swelling with or without a SAP. 
     In certain applications in the relevant industries, packers are subjected to highly acidic fluids after initially swelling in oil, water, brine, diesel, or diesel mud based drilling fluids. Rubber compounds typically used in packer elements will shrink or contract when exposed to acids. This contraction causes loss of contact sealing force between the well casing and the packer element. When chemical blowing agents are utilized, unreacted blowing agents remain in the vulcanized packer element and these blowing agents chemically react with the acid liberating gas from the chemical blowing agents, thereby offsetting potential loss of contact sealing pressure caused by contraction or shrinkage. Additional strength and contact sealing force can be achieved with the cellular structure by incorporating fiber reinforcement and/or fabric as discussed previously. 
     Various blowing agents may be utilized in the packers of the present disclosure. Blowing agents may include, but are not limited to sodium bicarbonate, Cellogen® CMC, a urea-based product, or another nitrogen or carbon dioxide liberating product. The blowing agent may be selected to be acid activated or activated by the presence of another chemical or substance. 
     In other embodiments, a non-homogeneous arrangement of cellular structure or structures, and/or location, type and concentration of the fibers or fabric can be utilized to provide additional control of swell rate and localized rigidity and stiffness of the packer element. Such packers, in addition to those disclosed above, provide a much higher degree of control and tailoring of performance of the swellable packer than currently available using existing technology. 
     Referring now to  FIG. 11 , a closeup cutaway view of a portion of a swellable packer element according to aspects of the present disclosure is shown. The view of  FIG. 11  may be considered as a closeup of a portion of  FIG. 10 . Here, individual pockets or voids  1102  containing blowing agents can be seen to occupy the elastomer comprising the packer element  1002 . Also shown are optional fibers  1104  which, as described, served to increase transport of fluids through the elastomer and to increase cohesive strength. 
     Blowing agents can also be used in layered embodiments as shown in  FIG. 12 . Layers of elastomer  402  are alternated with layers of fiber  404  as described with respect to  FIGS. 4-5 , for example. The elastomer layers  402  may contain pockets of blowing agent  1102 . It is also optional in such embodiments to include separate fibers (e.g., flock)  1104  in the elastomer layers  402 . 
     A difficulty that may be encountered when dealing with an SAP immersed in various saline solutions is the undesirable absorbency drop due to the presence of valence cations which impede bonding with water molecules. The overall result is unsatisfactory swelling. Various embodiments of the present disclosure do not rely on water absorbency to produce swelling, but rather a volume increase created by the sudden release of gas from the thermal decomposition of a sponging, or blowing, agent incorporated in the rubber compound. 
     It is to be understood that the terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, or integers or groups thereof and that the terms are to be construed as specifying components, features, steps or integers. 
     If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element. 
     It is to be understood that where the claims or specification refer to “a” or “an” element, such reference is not be construed that there is only one of that element. 
     It is to be understood that where the specification states that a component, feature, structure, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included. 
     Where applicable, although state diagrams, flow diagrams or both may be used to describe embodiments, the invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described. 
     Methods of the present invention may be implemented by performing or completing manually, automatically, or a combination thereof, selected steps or tasks. 
     The term “method” may refer to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the art to which the invention belongs. 
     The term “at least” followed by a number is used herein to denote the start of a range beginning with that number (which may be a ranger having an upper limit or no upper limit, depending on the variable being defined). For example, “at least 1” means 1 or more than 1. The term “at most” followed by a number is used herein to denote the end of a range ending with that number (which may be a range having 1 or 0 as its lower limit, or a range having no lower limit, depending upon the variable being defined). For example, “at most 4” means 4 or less than 4, and “at most 40%” means 40% or less than 40%. 
     When, in this document, a range is given as “(a first number) to (a second number)” or “(a first number)-(a second number)”, this means a range whose lower limit is the first number and whose upper limit is the second number. For example, 25 to 100 should be interpreted to mean a range whose lower limit is 25 and whose upper limit is 100. Additionally, it should be noted that where a range is given, every possible subrange or interval within that range is also specifically intended unless the context indicates to the contrary. For example, if the specification indicates a range of 25 to 100 such range is also intended to include subranges such as 26-100, 27-100, etc., 25-99, 25-98, etc., as well as any other possible combination of lower and upper values within the stated range, e.g., 33-47, 60-97, 41-45, 28-96, etc. Note that integer range values have been used in this paragraph for purposes of illustration only and decimal and fractional values (e.g., 46.7-91.3) should also be understood to be intended as possible subrange endpoints unless specifically excluded. 
     It should be noted that where reference is made herein to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously (except where context excludes that possibility), and the method can also include one or more other steps which are carried out before any of the defined steps, between two of the defined steps, or after all of the defined steps (except where context excludes that possibility). 
     Further, it should be noted that terms of approximation (e.g., “about”, “substantially”, “approximately”, etc.) are to be interpreted according to their ordinary and customary meanings as used in the associated art unless indicated otherwise herein. Absent a specific definition within this disclosure, and absent ordinary and customary usage in the associated art, such terms should be interpreted to be plus or minus 10% of the base value. 
     Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While the inventive device has been described and illustrated herein by reference to certain preferred embodiments in relation to the drawings attached thereto, various changes and further modifications, apart from those shown or suggested herein, may be made therein by those of ordinary skill in the art, without departing from the spirit of the inventive concept the scope of which is to be determined by the following claims.