Patent Publication Number: US-2021171817-A1

Title: Plugging devices having filaments coated with swellable material

Description:
BACKGROUND 
     This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in examples described below, more particularly provides plugging devices having filaments coated with swellable material. 
     It can be useful to be able to control fluid flow through selected perforations or other openings in a well. For example, flow diverters or plugging devices may be used to restrict or prevent flow of a treatment fluid (such as, a fracturing fluid, acid, conformance agent, permeability modifier, etc.) into perforations that have already received adequate amounts of the treatment fluid. In this manner, the treatment fluid will be diverted to other perforations that have not yet received adequate amounts of the treatment fluid. 
     Therefore, it will be appreciated that improvements are continually needed in the art of constructing and utilizing plugging devices for controlling flow through openings in wells. Such improvements may be useful in a variety of different situations, including situations other than those in which it is desired to prevent flow of a treatment fluid into perforations that have received treatment fluid therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative partially cross-sectional view of an example of a well system and associated method which can embody principles of this disclosure. 
         FIG. 2  is a representative side view of an example of a filament yarn that may be used in a plugging device incorporating the principles of this disclosure. 
         FIG. 3  is a representative flowchart for an example method of producing the plugging device. 
         FIG. 4  is a representative flowchart for another example method of producing the plugging device. 
         FIG. 5  is a representative side view of an example of the plugging device. 
         FIG. 6  is a representative flowchart for another example method of producing the plugging device. 
         FIG. 7  is a representative partially cross-sectional view of the plugging device engaged with an opening in a subterranean well. 
         FIG. 8  is a representative cross-sectional view of the filament yarn sealed against a surface of the opening. 
     
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in  FIG. 1  is a system  10  for use with a well, and an associated method, which can embody principles of this disclosure. However, it should be clearly understood that the system  10  and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system  10  and method described herein and/or depicted in the drawings. 
     In the  FIG. 1  example, a tubular string  12  is conveyed into a wellbore  14  lined with casing  16  and cement  18 . Although multiple casing strings would typically be used in actual practice, for clarity of illustration only one casing string  16  is depicted in the drawings. 
     Although the wellbore  14  is illustrated as being vertical, sections of the wellbore could instead be horizontal or otherwise inclined relative to vertical. Although the wellbore  14  is completely cased and cemented as depicted in  FIG. 1 , any sections of the wellbore in which operations described in more detail below are performed could be uncased or open hole. Thus, the scope of this disclosure is not limited to any particular details of the system  10  and method. 
     The tubular string  12  of  FIG. 1  comprises coiled tubing  20  and a bottom hole assembly  22 . As used herein, the term “coiled tubing” refers to a substantially continuous tubing that is stored on a spool or reel  24 . The reel  24  could be mounted, for example, on a skid, a trailer, a floating vessel, a vehicle, etc., for transport to a wellsite. Although not shown in  FIG. 1 , a control room or cab would typically be provided with instrumentation, computers, controllers, recorders, etc., for controlling equipment such as an injector  26  and a blowout preventer stack  28 . 
     As used herein, the term “bottom hole assembly” refers to an assembly connected at a distal end of a tubular string in a well. It is not necessary for a bottom hole assembly to be positioned or used at a “bottom” of a hole or well. 
     When the tubular string  12  is positioned in the wellbore  14 , an annulus  30  is formed radially between them. Fluid, slurries, etc., can be flowed from surface into the annulus  30  via, for example, a casing valve  32 . One or more pumps  34  may be used for this purpose. Fluid can also be flowed to surface from the wellbore  14  via the annulus  30  and valve  32 . 
     Fluid, slurries, etc., can also be flowed from surface into the wellbore  14  via the tubing  20 , for example, using one or more pumps  36 . Fluid can also be flowed to surface from the wellbore  14  via the tubing  20 . 
     In the further description below of the example of  FIGS. 7 &amp; 8 , one or more flow conveyed plugging devices are used to block or plug openings in the system  10  of  FIG. 1 . However, it should be clearly understood that these methods and the plugging device may be used with other systems, and the plugging device may be used in other methods in keeping with the principles of this disclosure. 
     The example methods described below allow existing fluid passageways to be blocked permanently or temporarily in a variety of different applications. Certain plugging device examples described below are made of a filament material and may comprise a central body, a “knot” or other enlarged geometry. 
     The plugging devices may be conveyed into the passageways or leak paths to be plugged using pumped fluid. Filaments, yarn or twine extending outwardly from a body of a device can “find” and follow the fluid flow, pulling the enlarged geometry and/or filaments into a restricted portion of a flow path, causing the enlarged geometry and additional strands to become tightly wedged into the flow path, thereby sealing off fluid communication. 
     The plugging devices can comprise degradable or non-degradable materials. The degradable materials can be either self-degrading, or can require degrading treatments, such as, by exposing the materials to certain acids, certain base compositions, certain chemicals, certain types of radiation (e.g., electromagnetic or “nuclear”), or elevated temperature. The exposure can be performed at a desired time using a form of well intervention, such as, by spotting or circulating a fluid in the well so that the material is exposed to the fluid. 
     In some examples, the material can be an acid degradable material (e.g., nylon, etc.), a mix of acid degradable materials (for example, nylon fibers mixed with particulate such as calcium carbonate), self-degrading material (e.g., poly-lactic acid (PLA), poly-glycolic acid (PGA), etc.), material that degrades by galvanic action (such as, magnesium alloys, aluminum alloys, etc.), a combination of different self-degrading materials, or a combination of self-degrading and non-self-degrading materials. 
     In certain examples described below, the plugging device can be made of knotted filament materials. Multiple knots can be used with any number of loose ends. The ends can be splayed outward. The filament material can be incorporated into twine, rope, fabric, metal wool, cloth or another woven or braided structure. 
     The plugging device can be used to block open sleeve valves, perforations or any leak paths in a well (such as, leaking connections in casing, corrosion holes, etc.). Any opening or passageway through which fluid flows can be blocked with a suitably configured plugging device. For example, an intentionally or inadvertently opened rupture disk, or another opening in a well tool, could be plugged using the plugging device. 
     In some examples, the bottom hole assembly  22  can comprise a perforator that is used to form perforations through the casing  16  and cement  18 . In this manner, fluid communication is established between an interior of the casing  16  and an earth formation penetrated by the wellbore  14 . Plugging devices can be used to control the flow of fluid (such as a treatment fluid) through some or all of the perforations. 
     Referring additionally now to  FIG. 2 , an example of a filament yarn  40  is representatively illustrated. The filament yarn  40  may be used to construct a plugging device for use in the  FIG. 1  well system  10  and method, or it may be used to construct plugging devices for use with other systems or methods. 
     In the  FIG. 2  example, the yarn  40  comprises multiple continuous filaments  42  that are twisted together to form the yarn. In other examples, the filaments  42  may not be twisted together to form the yarn  40 . The filaments  42  and yarn  40  can be either be as spun, or texturized. Texturizing may be accomplished by imparting a “false twist” or by air entanglement. Any number of filament(s)  42  may be used in the yarn  40 , the filaments are not necessarily continuous, and the filaments are not necessarily twisted together, in other examples. 
     The filaments  42  may be formed from a variety of different materials. These materials include, but are not limited to, polyethylene terephthalate (PET), nylon, acrylics, polyurethanes, polypropylene, rayon, aramid, modacrylic, olefin, polyester, saran, polylactic acid (PLA), polyether ether ketone (PEEK), polyphenylene sulfide, etc. Each filament  42  could comprise a combination of different materials in some examples. 
     If multiple filaments  42  are used in the yarn  40 , then the different filaments may comprise respective different materials. The scope of this disclosure is not limited to use of any particular material or combination of materials for the filaments  42 . 
     In some examples, the yarn  40  can be used to produce a rope or twine (see  FIG. 5 ) as an intermediate step in constructing a plugging device. In that case, multiple strands of yarn  40  may be braided together to form the twine, and the twine (or multiple twines) may then be used to form the plugging device. 
     Referring additionally now to  FIG. 3 , a flowchart for an example method  50  of producing a plugging device is representatively illustrated. In this example, a certain configuration of the plugging device is produced, but it will be appreciated by those skilled in the art that different plugging device configurations may be produced using certain steps of the method  50 , without departing from the principles of this disclosure. 
     In step  52 , a yarn (such as, the  FIG. 2  filament yarn  40 ) is impregnated with a swellable material (see  FIG. 8 ). In this example, the swellable material is selected so that it swells (increases in volume) in response to contact with water in a well. Each of the filaments  42  of the yarn  40  is coated with the swellable material in the impregnating step  52 . 
     A suitable water-swellable polymer for use as the swellable material is sodium polyacrylate. In order to facilitate the impregnating of the yarn  40 , the sodium polyacrylate may be dispersed in a polyvinyl chloride (PVC) plastisol resin matrix, so that the material coats the individual filaments  42 . 
     In other examples, the swellable material could swell in response to other types of stimuli. The swellable material could swell in response to contact with a particular swelling agent in the well, such as, hydrocarbons or a fluid having a selected pH range. The swellable material could swell in response to exposure to elevated temperature in the well. The swellable material could swell in response to passage of time. Thus, the scope of this disclosure is not limited to any particular technique, mechanism or stimulus for causing the swellable material to swell. 
     Additional suitable swellable materials include the following:
         1. Poly(acrylic acid), crosslinked, sodium or potassium salt thereof;   2. Poly(acrylic acid-co-acrylamide), crosslinked, sodium or potassium salt thereof;   3. Poly(acrylic acid), sodium or potassium salt-graft-poly(ethylene oxide), crosslinked;   4. Poly(2-hydroxyethyl methacrylate);   5. Poly(2-hydroxyethyl acrylate);   6. Starch;   7. Starch grafted with acrylic acid or methacrylic acid, sodium or potassium salt thereof;   8. Water-swellable clay (e.g., sodium bentonite); and   9. Cellulose derivatives (e.g., hydroxyethylcellulose).       

     In step  54 , the impregnated yarn  40  is heat cured. Application of heat binds the swellable material coating to the filaments  42  of the yarn  40 . 
     In step  56 , the yarn  40  is braided to form a twine. The term “twine” is used herein to indicate a string or rope formed of multiple strands braided or twisted together. 
     In step  58 , the twine is knotted to form an enlarged body of the plugging device (see  FIG. 5 ). A knot may be formed in the twine by interlacing ends of the twine, so that a compact bundle, knob or knot in the twine serves as the body of the plugging device. 
     In step  60 , after the plugging device has been produced, it is deployed into a well. In the  FIG. 1  system  10  and method, one or more plugging devices may be deployed into the wellbore  14  to plug or block fluid flow through perforations formed in the casing  16  and cement  18 . 
     The plugging devices may be deployed into the wellbore  14  before or after the perforations are formed. The plugging devices may be individually or collectively deployed into the wellbore  14  from a surface location, or the plugging devices may be conveyed into the wellbore in a container (for example, as a component of the bottom hole assembly  22 ) and then released from the container downhole. The scope of this disclosure is not limited to any particular method for deploying the plugging devices into a well. 
     Referring additionally now to  FIG. 4 , another example flowchart for the method  50  is representatively illustrated. In this example, the steps  54 ,  56 ,  58 ,  60  of the  FIG. 3  method  50  are used, but the steps are performed in a different order. 
     In the  FIG. 4  method  50 , the yarn  40  is braided to form the twine in step  56 , and then the twine is impregnated with the swellable material in step  62 . This step  62  is similar to the step  52  of the  FIG. 3  method, except that the filaments  42  of the yarn  40  are coated with the swellable material after the twine is formed from the yarn. 
     In order to ensure that each of the individual filaments  42  is coated with the swellable material, the impregnating step  62  may be performed after a vacuum has been applied to the twine. For example, the twine could be placed in a vacuum chamber or flexible enclosure, a vacuum could be applied to the chamber or enclosure, and then the swellable material could be introduced into the chamber or enclosure. After the twine is impregnated with the swellable material, the steps  54 ,  58  and  60  are performed to bind the swellable material to the filaments  42 , form the knot and then deploy the plugging device  70  into the well. 
     Referring additionally now to  FIG. 5 , an example of a plugging device  70  that the method  50  may be used to produce is representatively illustrated. However, it should be understood that other plugging device configurations could be produced by the method  50  examples described herein, in keeping with the principles of this disclosure. 
     In the  FIG. 5  example, multiple strands of the yarn  40  are braided together to form a rope or twine  72 . An enlarged body  74  of the plugging device  70  is formed by knotting the twine  72 , such as, by interlacing ends of the twine to form a compact knot (for example, a double overhand knot or other type of knot). 
     A size of the knot is selected so that the knot or the body  74  will engage but not pass through an opening in the well. For example, if it is desired to prevent flow through a perforation in the well, the body  74  can be configured so that it has an outer dimension that is larger than a diameter of the perforation. In this manner, the plugging device  70  can engage the perforation or other opening and block flow of fluid through the opening. 
     As depicted in  FIG. 5 , the strands of yarn  40  are splayed outward at ends of the twine  72 . This configuration increases fluid drag on the plugging device  70 , so that the plugging device is carried with fluid flow to an opening which it is desired to plug. Even more fluid drag may be produced by splaying outward the individual filaments  42  of the yarn  40  at the ends of the twine  72 . 
     However, it is not necessary for the strands of yarn  40  to be splayed outward at the ends of the twine  72 . For example, the twine itself extending outwardly from the body  74  may be sufficient to produce a desired amount of fluid drag on the plugging device  70 . 
     Referring additionally now to  FIG. 6 , another example flowchart for the method  50  is representatively illustrated. In this example, the knot is formed in the step  58  prior to impregnating the knot with the swellable material in a step  78 . 
     The knot may be formed as described above for the  FIGS. 3 &amp; 4  examples. The yarn  40  is braided to form the twine  72  (see step  56 ) and the resulting twine is used to form the knot or body  74  of the plugging device  70  in this example. 
     As depicted in  FIG. 6 , a vacuum is applied to the plugging device  70  after the knot or body  74  is formed in step  76 . This is similar to the technique described above in relation to impregnating the twine  72  in the  FIG. 4  example. However, in the  FIG. 6  method  50 , the knot is formed prior to the vacuum being applied to the plugging device  70 . The plugging device  70  could be placed in a vacuum chamber or flexible enclosure, a vacuum could be applied to the chamber or enclosure, and then the swellable material could be introduced into the chamber or enclosure. 
     In step  78 , the knot is impregnated with the swellable material. If the technique described above is used (e.g., a vacuum is applied to the entire plugging device  70 ), then the entire plugging device can be impregnated with the swellable material. Preferably, each of the individual filaments  42  in at least the knot or body  74  of the plugging device  70  is coated with the swellable material as a result of this step  78 . After the knot is impregnated with the swellable material, the steps  54  and  60  are performed to bind the swellable material to the filaments  42  and then deploy the plugging device  70  into the well. 
     Referring additionally now to  FIG. 7 , the plugging device  70  is representatively illustrated in the well system  10  and method after the plugging device has engaged an opening  80  in the well. In this example, the plugging device  70  is deployed into the well and is conveyed into engagement with the opening  80  by fluid flow in the well. The twine  72  and yarn  40  extending outwardly from the body  74  enhances fluid drag on the plugging device  70 , so that it is conveyed by the flow to the opening  80  (through which the fluid flows prior to the plugging device engaging the opening). 
     The plugging device  70  engages the opening  80 , but the body  74  of the plugging device  70  is too large to permit the plugging device  70  to pass through the opening. In this manner, the plugging device  70  blocks flow through the opening  80 . 
     The opening  80  in the  FIG. 7  example is in the form of a perforation formed through the casing  16  and cement  18 . The perforation provides fluid communication between an interior of the casing  16  and an earth formation  82 . Other types of openings may be blocked by the plugging device  70  in other examples. 
     The plugging device  70  includes features that enhance the engagement between the plugging device and the opening  80 , so that the plugging device can more effectively prevent fluid flow through the opening. For example, the use of the swellable material on the filaments  42  of the yarn  40  can enable the plugging device  70  to sealingly engage a surface of the opening  80 , and can provide for sealing between the filaments so that leakage of fluid through the plugging device itself is prevented, thereby decreasing a permeability of the plugging device. 
     Referring additionally now to  FIG. 8 , an enlarged scale cross-sectional view of engagement between the plugging device  70  and the opening  80  is representatively illustrated. In this view, one of the yarns  40  of the plugging device body  74  is depicted in contact with a surface  80   a  of the opening  80 . The yarn  40  shown in  FIG. 8  could instead be part of the twine  72  extending outwardly from the body  74 . Thus, it will be appreciated that portions of the plugging device  70  other than the body  74  can engage and seal against the surface  80   a  of the opening  80 . 
     As described above, each of the filaments  42  is coated with a swellable material  84 . After the plugging device  70  is deployed into the well, the swellable material  84  swells. For example, the swellable material  84  may be contacted by a suitable swelling agent (such as, water, hydrocarbons, a fluid having a particular pH range, etc.) or may experience another type of stimulus (such as, heat, passage of time, etc.), which causes the swellable material to swell. 
     In the  FIG. 8  example, the swellable material  84  has swollen and sealingly engages the inner surface  80   a  of the opening  80 . In this manner, the ability of the plugging device  70  to effectively block flow through the opening  80  is significantly enhanced, especially in circumstances in which the surface  80   a  of the opening is irregularly shaped as depicted in  FIG. 8 . 
     In addition, the swellable material  84  on each of the filaments  42  sealingly contacts the swellable material on adjacent filaments, thereby sealing between the filaments. This prevents fluid flow through the plugging device  70  itself, thereby decreasing a permeability of the plugging device. 
     Note that the swellable material  84  may swell before or after the plugging device  70  engages the opening  80 . A swelling agent that causes the swellable material  84  to swell may be present in the well when the plugging device  70  is deployed into the well, or it may be introduced into the well after the plugging device is deployed or after the plugging device engages the opening  80 . 
     As mentioned above, the plugging device  70  may comprise a degradable material. After it is no longer desired for the plugging device  70  to block flow through the opening  80  (such as, when it is desired to produce fluid from the formation  82 ), all or a portion of the plugging device may degrade, so that it can no longer block flow through the opening. For example, the filaments  42 , the swellable material  84  or both of them may comprise a degradable material. 
     Any technique or mechanism for degrading a material of the plugging device  70  may be used, including but not limited to those described in US Publication No. 2017/0260828, the entire disclosure of which is incorporated herein by this reference for all purposes. Alternatively, the plugging device  70  could be dislodged from the opening  80  by production fluid flow from the formation  82  or by mechanical means, including but not limited to those described in U.S. Pat. No. 9,920,589, the entire disclosure of which is incorporated herein by this reference for all purposes. 
     It may now be fully appreciated that the above disclosure provides significant advancements to the art of constructing and utilizing plugging devices for controlling flow through openings in wells. In some examples described above, individual filaments  42  of a plugging device  70  are coated with a swellable material  84 . The swellable material  84  swells in the well, so that sealing is enhanced between the individual filaments  42  and/or between the filaments  42  and a surface  80   a  of an opening  80 . 
     The above disclosure provides to the art a method  50  of constructing a plugging device  70  for use in a subterranean well. In one example, the method  50  can comprise: incorporating multiple filaments  42  into the plugging device  70 , and coating each individual filament  42  with a swellable material  84 . 
     In any of the examples described herein: 
     The incorporating step may include incorporating the filaments  42  into multiple strands of yarn  40 . 
     The incorporating step may include forming a twine  72  with the multiple strands of yarn  40 . 
     The coating step may include coating the filaments  42  after the twine  72  forming step. 
     The method may include forming a knot in the twine  72 . 
     The coating step may include coating the filaments  42  after the knot forming step. 
     The swellable material  84  may comprise a water-swellable material. 
     The swellable material  84  may swell in the well. 
     Also described above is a plugging device  70  for use in a subterranean well. In one example, the plugging device  70  can comprise: a body  74  comprising multiple filaments  42 , and a swellable material  84  on each of the individual filaments  42 . 
     In any of the examples described herein: 
     The body  74  may comprise a knot. 
     The swellable material  84  may comprise a coating on each of the filaments  42 . 
     The swellable material  84  may seal between the filaments  42 . 
     The swellable material  84  may prevent fluid flow between the filaments  42 . 
     The filaments  42  may be incorporated into multiple strands of yarn  40 . 
     The strands of yarn  40  may be incorporated into a twine  72 , and a knot may be formed in the twine  72 . 
     The yarn  40  may be splayed outward at ends of the twine  72 . 
     A system  10  for use with a subterranean well is also described above. In one example, the system  10  can comprise: a plugging device  70  conveyed by fluid flow into engagement with an opening  80 , whereby the plugging device  70  blocks flow through the opening  80 . The plugging device  70  in this example comprises multiple filaments  42 , each of the multiple filaments  42  being coated with a swellable material  84 . The swellable material  84  seals against a surface  80   a  of the opening  80 . 
     In any of the examples described herein: 
     The filaments  42  may be incorporated into a body  74  of the plugging device  70 . 
     The body  74  may comprise a knot. 
     The body  74  may be larger than the opening  80 , whereby the body  74  is prevented from passing through the opening  80 . 
     The swellable material  84  may comprise a water-swellable material. 
     The swellable material  84  may seal between the filaments  42 . 
     The swellable material  84  may prevent fluid flow between the filaments  42 . 
     The filaments  42  may be incorporated into multiple strands of yarn  40 . 
     The strands of yarn  40  may be incorporated into a twine  72 , and a knot may be formed in the twine  72 . 
     The yarn  40  may be splayed outward at ends of the twine  72 . 
     The swellable material  84  may reduce a permeability of the plugging device  70 . 
     Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example&#39;s features are not mutually exclusive to another example&#39;s features. Instead, the scope of this disclosure encompasses any combination of any of the features. 
     Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used. 
     The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.” 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents.