`(19) World Intellectual Property
`3‘
`Organization
`Intemationa] Bureau
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`llllllllllllllllllllllllllllllll|l|||||l||||llllllllllllllllllllllllllllIllllllflllllllllllllll
`
`(10) International Publication Number
`
`
`
`& 1
`
`(43) International Publication Date
`8 May 2017 (18.05.2017)
`
`WO 2017/082865 A1
`WI P01 P C T
`
`
`(51)
`
`International Patent Classification:
`E218 33/12 (2006.01)
`E218 23/06 (2006.01)
`E213 33/128 (2006.01)
`
`(21)
`
`International Application Number:
`
`(72)
`
`Inventors: WALTON, Zachary William; 2204 Southern
`Ct., Carrollton, Texas 75006 (US). FRIPP, Michael Lin—
`ley; 3826 Cemetery Hill Rd., Carrollton, Texas 75007
`(US):
`
`(22)
`
`International Filing Date:
`
`(25) Filing Language:
`(26) Publication Language:
`
`PCT/USZOlS/059823
`
`(74)
`
`10 November 2015 (10.11.2015)
`
`English (81)
`English
`
`(71) Applicant: HALLIBURTON ENERGY SERVICES,
`INC. [US/US]; 3000 N. Sam Houston Parkway E, llous-
`ton, Texas 77032-3219 (US).
`
`Agents: KAISER, Iona et a1.; McDerinott Will & Emery
`LLP, 500 North Capitol Street, N.W., Washington, District
`ofColumbia 20001 (US).
`
`Designated States (unless otherwise indicated, for every
`kind ofnational protection available): AE, AG, AL, AM,
`AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY,
`BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM,
`DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT,
`HN, HR, HU, ID, IL, IN, IR, IS, JP, KE, KG, KN, KP, KR,
`KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG,
`MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM,
`e
`
`[Continued on next page]
`(54) Title: WELLBORE ISOLATION DEVICES WITH DEGRADABLE SLIPS AND SLIP BANDS
`
`
`
`230
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`230
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`228
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`218a
`
`(57) Abstract: A wellbore isolation device may include a mandrel; degradable slips dis—
`posed abont the mandrel and composed of a degradable metal alloy selected from the group
`consisting of a magnesium alloy, an aluminum alloy, and any combination thereof; and at
`least one packet element disposed along the mandrel. The degradable slips may be formed of
`a degradable metal material, Optionally, the wellborc isolation device may further include
`degradable slip bands formed of a degradable metal material or a degradable polymer,
`
`200
`/
`
`
`
`
`210
`2161)
`215b
`5 217b
`
`218D
`2161)
`2151)
`217b d
`
`236
`
`
`
`e2.amen:
`W'
`
` 222
`Willi/Illlllllllfll/A
`
`FIG. 2
`
`
`
`wo2017/082865A1Illllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`
`
`
`WO 2017/082865 A1 llllllIllllllllilllllllllllIIIIIIIIIHIIIIllHIIIIIIIIIIIIIIIIIIIIIIlllllllllllllllllllllllllll
`PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC,
`SD, SE, SG, SK, SL, SM, ST, SV, SY, TII, TJ, TM, TN,
`TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW.
`
`SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA,
`GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG).
`Declarations under Rule 4.17:
`
`(84)
`
`Designated States (unless otherwise indicated, jbr every
`kind Q/regionalprotection available): ARIPO (BW, GII,
`GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ,
`TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU,
`TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE,
`DK, FE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT,
`LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE,
`
`— as to applicant’s entitlement to apply fur and be granted
`apalem (Ru/e 4.l7(z'i))
`Published:
`
`—-
`
`with inlermnional search report (Art. 21(3))
`
`
`
`WO 2017/082865
`
`PCT/US2015/059823
`
`WELLBORE ISOLATION DEVICES WITH DEGRADABLE SLIPS
`AND SLIP BANDS
`
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`BACKGROUND
`
`[0001]
`
`The present disclosure describes embodiments of wellbore
`
`isolation devices.
`
`[0002]
`
`In the drilling, completion, and stimulation of hydrocarbon~
`
`producing wells, a variety of downhole tools are used. For example,
`
`it
`
`is often
`
`desirable to seal portions of a wellbore, such as during fracturing operations when
`
`various fluids and slurries are pumped from the surface into a casing string that
`
`lines the wellbore, and forced out
`
`into a surrounding subterranean formation
`
`through the casing string.
`
`It thus becomes necessary to seal
`
`the wellbore and
`
`thereby provide zonal
`
`isolation at
`
`the location of
`
`the desired subterranean
`
`formation. Wellbore isolation devices, such as packers, bridge piugs, and fracturing
`
`plugs (i.e., “frac” plugs), are designed for these general purposes and are well
`
`known in the art of producing hydrocarbons, such as oil and gas. Such wellbore
`
`isolation devices may be used in direct contact with the formation face of the
`
`wellbore, with a casing string extended and secured within the weilbore, or with a
`screen or wire mesh.
`
`[0003]
`
`After
`
`the desired downhole operation is complete,
`
`the seal
`
`formed by the wellbore isolation device must be broken and the tool itself removed
`
`from the wellbore. Removing the wellbore isolation device may allow hydrocarbon
`
`production operations to commence without being hindered by the presence of the
`
`downhole tool. Removing wellbore isolation devices, however,
`
`is
`
`traditionally
`
`accomplished by a complex retrieval operation that involves milling or drilling out a
`
`portion of the wellbore isolation device, and subsequently mechanically retrieving
`
`its remaining portions. To accomplish this, a tool string having a mill or drill bit
`
`attached to its distal end is introduced into the wellbore and conveyed to the
`wellbore isolation device to mill or drill out the wellbore isolation device. After
`
`drilling out the wellbore isolation device,
`
`the remaining portions of the wellbore
`
`isolation device may be grasped onto and retrieved back to the surface with the
`
`tool string for disposal. As can be appreciated,
`
`this retrieval operation can be a
`
`costly and time—consuming process.
`
`
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`WO 2017/082865
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`PCT/USZOlS/059823
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0004]
`
`The following figures are included to illustrate certain aspects of
`
`the embodiments, and should not be viewed as exclusive embodiments. The subject
`
`matter disclosed is capable of considerable modifications, alterations, combinations,
`
`and equivalents in form and function, as will occur to those skilled in the art and
`
`having the benefit of this disclosure.
`
`[0005]
`
`FIG. 1 is a well system that can employ one or more principles of
`
`the present disclosure, according to one or more embodiments.
`
`[0006]
`
`FIG. 2 is a cross—sectional side view of a frac plug that can employ
`
`the principles of the present disclosure.
`
`[0007]
`
`FIG. 3 is a perspective view of the frac plug of FIG. 2.
`
`[0008]
`
`FIG. 4 is a perspective view of a frac plug that can employ the
`
`principles of the present disclosure.
`
`[0009]
`
`FIG. 5 is a
`
`cross—sectional view of a
`
`frac plug in operation,
`
`according to one or more embodiments of the present disclosure.
`
`DETAILED DESCRIPTION
`
`[0010]
`
`The present disclosure describes embodiments of wellbore
`
`isolation devices that are made of degrading materials, and their methods of use
`
`during a subterranean formation operation.
`
`In particular, the present disclosure
`
`describes wellbore isolation devices having slip bands composed of a degradable
`
`material (also referred to herein as “degradable slip bands") that degrade in a
`
`wellbore environment at a desired time during the performance of a subterranean
`
`formation operation (or simply “formation operation”). These degradable materials
`
`(also referred to collectively as “degradable substances”) are discussed in greater
`
`detail below. As used herein, the term “wellbore isolation device,” and grammatical
`
`variants thereof,
`
`is a device that is set in a wellbore to isolate a portion of the
`
`wellbore thereabove from a portion therebelow so that fluid can be forced into the
`
`surrounding subterranean formation above the device. As used herein, the term
`
`“sealing ball” and “frac ball,” and grammatical variants thereof, refer to a spherical
`
`or spheroidal element designed to seal a portion of a wellbore isolation device that
`
`is accepting fluids like the inner diameter of a mandrel, thereby diverting reservoir
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`treatments to other portions of a target zone in a subterranean formation. An
`
`example of a sealing ball
`
`is a frac ball
`
`in a frac plug wellbore isolation device. As
`
`used herein, the term “packer element,” and grammatical variants thereof, refers to
`
`inflatable, or swellable element that expands against a casing or
`an expandable,
`wellbore to seal the wellbore.
`
`[0011]
`
`One or more illustrative embodiments disclosed herein are
`
`presented below. Not all features of an actual
`
`implementation are described or
`
`shown in this application for the sake of clarity.
`
`It
`
`is understood that
`
`in the
`
`development of an actual embodiment incorporating the embodiments disclosed
`
`herein, numerous implementation—specific decisions must be made to achieve the
`
`developer's goals,
`
`such as compliance with system-related,
`
`lithology~related,
`
`business-related, government—related,
`
`and other constraints, which vary by
`
`implementation and over time. While a developer's efforts might be complex and
`
`time-consuming, such efforts would be, nevertheless, a routine undertaking for
`
`those of ordinary skill in the art having benefit of this disclosure.
`
`[0012]
`
`It should be noted that when “about” is provided herein at the
`
`beginning of a numerical list, the term modifies each number of the numerical list.
`
`In some numerical listings of ranges, some lower limits listed may be greater than
`
`some upper limits listed. One skilled in the art will recognize that the selected
`
`subset will require the selection of an upper limit
`
`in excess of the selected lower
`
`limit. Unless otherwise indicated, all numbers expressing quantities of ingredients,
`
`properties such as molecular weight, reaction conditions, and so forth used in the
`
`present specification and associated claims are to be understood as being modified
`
`in all instances by the term “about.” As used herein, the term “about” encompasses
`
`+/— 5% of each numerical value. For example,
`
`if the numerical value is “about
`
`80%,” then it can be 80% +/- 5%, equivalent to 76% to 84%. Accordingly, unless
`
`indicated to the contrary,
`
`the numerical parameters set forth in the following
`
`specification and attached claims are approximations that may vary depending
`
`upon the desired properties sought to be obtained by the exemplary embodiments
`
`described herein. At the very least, and not as an attempt to limit the application of
`
`the doctrine of equivalents to the scope of the claim, each numerical parameter
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`should at least be construed in light of the number of reported significant digits and
`
`by applying ordinary rounding techniques.
`
`[0013]
`
`While compositions and methods are described herein in terms
`
`of “comprising” various components or steps, the compositions and methods can
`
`also “consist essentially of” or “consist of" the various components and steps. When
`
`“comprising” is used in a claim, it is open-ended.
`
`[0014]
`
`As used herein, the term “substantially” means largely, but not
`
`necessarily wholly.
`
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`
`The use of directional terms such as above, below, upper, lower,
`[0015]
`upward, downward, left, right, uphole, downhole and the like are used in relation to
`
`the illustrative embodiments as they are depicted in the figures,
`
`the upward
`
`direction being toward the top of the corresponding figure and the downward
`
`direction being toward the bottom of the corresponding figure, the uphole direction
`
`being toward the surface of the well and the downhole direction being toward the
`toe of the well.
`
`15
`
`[0016]
`
`The embodiments of the present disclosure are directed toward
`
`degradable wellbore isolation devices (e.g., frac plugs, bridge plugs, and packers)
`
`comprising degradable slip bands. As used herein, the term “degradable" and all of
`
`its grammatical variants (e.g., “degrade,” “degradation,” “degrading," “dissolve,”
`
`dissolving," and the like), refers to the dissolution or chemical conversion of solid
`
`materials such that reduced-mass solid end products result or reduced structural
`
`integrity results by at least one of solubilization, hydrolytic degradation, biologically
`
`formed entities
`
`(e.g.,
`
`bacteria
`
`or enzymes),
`
`chemical
`
`reactions
`
`(including
`
`electrochemical and galvanic reactions),
`
`thermal reactions, reactions induced by
`
`radiation, or combinations thereof. In complete degradation, no solid end products
`
`result, or structural shape is
`
`lost.
`
`In some instances,
`
`the degradation of the
`
`material may be sufficient for the mechanical properties of the material
`
`to be
`
`reduced to a point that the material no longer maintains its integrity and,
`
`in
`
`essence,
`
`falls apart or sloughs off
`
`into its surroundings. The conditions for
`
`degradation are generally wellbore conditions where an external stimulus may be
`
`used to initiate or effect the rate of degradation, where the external stimulus is
`
`naturally occurring in the wellbore (e.g., pressure, temperature) or introduced into
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`the wellbore (e.g., fluids, chemicals). For example, the pH of the fluid that interacts
`
`with the material may be changed by introduction of an acid or a base, or an
`
`electrolyte may be introduced or naturally occurring to induce galvanic corrosion.
`
`The term “wellbore environment,” and grammatical variants thereof, includes both
`
`naturally occurring wellbore environments and materials or fluids introduced into
`
`the wellbore. The term “at least a portion,” and grammatical variants thereof, with
`
`reference to a component having at
`
`least a portion composed thereof of a
`
`degradable material or substance (e.g., “at
`
`least a portion of a component
`
`is
`
`degradable” or “at least a portion of the slips and/or slip bands is degradable,” and
`
`variants thereof) refers to at least about 80% of the volume of that part being
`
`formed of the degradable material or substance.
`
`[0017]
`
`The degradable materials of the degradable slip bands may
`
`allow for time between setting the wellbore isolation device and when a particular
`
`downhole operation is undertaken, such as a hydraulic fracturing operation).
`
`Moreover, degradable materials allow for acid treatments and acidified stimulation
`
`of a wellbore.
`
`In some embodiments,
`
`the degradable materials may require a
`
`greater
`
`flow area or
`
`flow capacity to enable production operations without
`
`unreasonably impeding or obstructing fluid flow while the wellbore isolation device
`
`degrades. As a result, production operations may be efficiently undertaken while
`
`the wellbore isolation device degrades and without creating significant pressure
`restrictions.
`
`[0018]
`
`Some embodiments of the present disclosure relate to methods
`
`of using a degradable wellbore isolation device, and in particular, a frac plug, during
`
`a hydraulic fracturing operation. For example, a frac plug may be introduced into a
`
`wellbore
`
`in
`
`a
`
`subterranean formation in accordance with the embodiments
`
`described herein. The wellbore may be an open—hole wellbore or have a casing
`
`string disposed therein. The frac plug comprises a plurality of components
`
`comprising at least a mandrel, degradable slips, optionally degradable slip bands,
`
`and a packer element. The degradable slip bands may be composed of a degradable
`
`metal material like a degradable metal alloy, wherein the degradable metal alloy is
`
`a magnesium alloy, and aluminum alloy, or a combination thereof. Optionally, the
`
`degradable slip bands may be composed of a degradable polymer, wherein the
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`degradable polymer is a polymer that degrades in water-based fluids or in an oil-
`
`based fluid, compositions for which are described further herein. Other components
`
`of the frac plug may additionally be comprised of a degradable material. For
`
`example, the mandrel, the degradable slips, the frac ball, or a combination thereof
`
`may be composed, at
`
`least
`
`in part, of a degradable metal material
`
`(e.g., a
`
`degradable metal alloy), a degradable polymer, or a combination thereof. Further,
`
`the packer elements, the frac ball, or a combination thereof may be composed, at
`
`least in part, of a degradable polymer, without departing from the scope of the
`
`present disclosure.
`
`[0019]
`
`The degradable slips or a component coupled thereto (e.g.,
`
`buttons coupled thereto) frictionally engage the wall of the wellbore or the casing
`
`string, depending on the configuration of
`
`the wellbore in
`
`the subterranean
`
`formation. As used herein, the term “wall,” and grammatical variants thereof (e.g.,
`
`wellbore wall), with reference to a wellbore refers to the outer rock face that
`
`bounds the drilled wellbore. The packer element of the frac plug is compressed
`
`against the wall of the wellbore or the casing string to set the frac plug within the
`
`wellbore,
`
`as described below. At
`
`least one perforation is created in
`
`the
`
`subterranean formation though the wall of the wellbore or the casing string (and
`
`any cement disposed between the wall of the wellbore and the casing string,
`
`if
`
`included). In some embodiments, a plurality of perforations, or a perforation cluster
`
`are created into the subterranean formation, without departing from the scope of
`
`the present disclosure. As used herein, the term “perforation,” and grammatical
`
`variants thereof, refers to a communication tunnel created through a wall of a
`
`wellbore, including through a casing string,
`
`into a subterranean formation through
`
`which production fluids may flow. Perforations may be formed by any means
`
`suitable in a subterranean formation including, but not limited to, shaped explosive
`
`charges, perforating guns, bullet perforating, abrasive jetting, or high—pressure fluid
`
`jetting, without departing from the scope of the present disclosure.
`
`[0020]
`
`The subterranean formation is hydraulically fractured through
`
`the at least one perforation. As used herein, the term “hydraulic fracturing," and
`
`grammatical variants thereof, refers to a stimulation treatment in which fluids are
`
`pumped at a high rate and pressure to overcome a fracture gradient within a
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`subterranean formation to cause fractures to be created or enhanced. The term
`
`“fracture gradient,” and grammatical variants thereof,
`
`refers to the pressure
`
`required to induce or enhance fractures in a subterranean formation at a given
`
`depth. That
`
`is,
`
`the fracture gradient may vary in a particular subterranean
`
`formation depending on the depth thereof.
`
`[0021]
`
`The degradable slip bands and other degradable components of
`
`the wellbore isolation device are degraded at
`
`least partially in the wellbore
`
`environment. As used herein,
`
`the term “at
`
`least partially degrading," and
`
`grammatical variants
`
`thereof
`
`(e.g.,
`
`“degrading at
`
`least partially,” “partially
`
`degrades,” and the like) with reference to degradation of a component thereof of a
`
`wellbore isolation device refers to the component degrading at least to the point
`
`wherein about 20% or more of the mass of the component degrades. For instance,
`
`the degradable metal alloy forming the degradable slip bands is at least partially
`
`degraded in the presence of an electrolyte in the wellbore environment. The
`
`production of a hydrocarbon (i.e., oil and/or gas) from the subterranean formation
`
`may proceed.
`
`In some instances, degradation of the degradable material and
`
`production of a hydrocarbon may occur simultaneously, or alternatively in series,
`
`without departing from the scope of the present disclosure. That is, the order,
`
`if
`
`any, of degradation and production may depend on selection of the particular
`
`degradable material (e.g., the degradable metal alloy or alloy combination), the
`
`degradation stimuli (e.g., the electrolyte or other stimulus), and the like, and any
`
`combination thereof.
`
`In some embodiments, accordingly, production may begin
`
`before degradation, or degradation may begin before production. Although
`
`degradation may begin and end before production begins,
`
`it is contemplated that
`
`both degradation and production will occur simultaneously during at least some
`
`point in time (or duration), regardless of which process is initiated first.
`
`[0022]
`
`FIG.
`
`1
`
`illustrates a well system 100 that may embody or
`
`otherwise employ one or more principles of the present disclosure, according to one
`
`or more embodiments. As illustrated, the well system 100 may include a service rig
`
`102 (also referred to as a “derrick") that is positioned on the earth’s surface 104
`
`and extends over and around a wellbore 106 that penetrates a subterranean
`
`formation 108. The service rig 102 may be a drilling rig, a completion rig, a
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`workover rig, or the like.
`
`In some embodiments,
`
`the service rig 102 may be
`
`omitted and replaced with a standard surface wellhead completion or installation,
`
`without departing from the scope of the disclosure. While the well system 100 is
`
`depicted as a landvbased operation, it will be appreciated that the principles of the
`
`present disclosure could equally be applied in any sea-based or sub~sea application
`
`where the service rig 102 may be a floating platform or sub-surface wellhead
`
`installation, as generally known in the art.
`
`[0023]
`
`The wellbore 106 may be drilled into the subterranean formation
`
`108 using any suitable drilling technique and may extend in a substantially vertical
`
`direction away from the earth’s surface 104 over a vertical wellbore portion 110. At
`
`some point in the wellbore 106, the vertical wellbore portion 110 may deviate from
`
`vertical
`
`relative to the earth’s surface 104 and transition into a substantially
`
`horizontal wellbore portion 112, although such deviation is not required. That is,
`
`the wellbore 106 may be vertical, horizontal, or deviated, without departing from
`
`the scope of the present disclosure. In some embodiments, the wellbore 106 may
`
`be completed by cementing a string of casing 114 within the wellbore 106 along all
`
`or a portion thereof. As used herein, the term “casing” refers not only to casing as
`
`generally known in the art, but also to borehole liner, which comprises tubular
`
`sections coupled end to end but not extending to a surface location.
`
`In other
`
`embodiments, however, the string of casing 114 may be omitted from all or a
`
`portion of the wellbore 106 and the principles of the present disclosure may equally
`
`apply to an “open~hole" environment.
`
`[0024]
`
`The well system 100 may further include a wellbore isolation
`
`device 116 that may be conveyed into the wellbore 106 on a conveyance 118 (also
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`referred to as a “tool string”) that extends from the service rig 102. The wellbore
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`isolation device 116 may include or otherwise comprise any type of casing or
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`borehole isolation device known to those skilled in the art including, but not limited
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`to, a frac plug, a bridge plug, a deployable baffle, a wellbore packer, a wiper plug, a
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`cement plug, or any combination thereof.
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`[0025]
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`The conveyance 118 that delivers the wellbore isolation device
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`116 downhole may be, but
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`is not
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`limited to, wireline, slickline, an electric line,
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`coiled tubing, drill pipe, production tubing, or the like. The wellbore isolation device
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`116 may be conveyed downhole to a target
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`location (not shown) within the
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`wellbore 106. At the target location, the wellbore isolation device may be actuated
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`or “set” to seal the wellbore 106 and otherwise provide a point of fluid isolation
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`within the wellbore 106. In some embodiments, the wellbore isolation device 116 is
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`pumped to the target location using hydraulic pressure applied from the service rig
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`102 at the surface 104.
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`In such embodiments,
`
`the conveyance 118 serves to
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`maintain control of the wellbore isolation device 116 as it traverses the wellbore
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`106 and provides the necessary power to actuate and set the wellbore isolation
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`device 116 upon reaching the target location. In other embodiments, the wellbore
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`isolation device 116 freely falls to the target location under the force of gravity to
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`traverse all or part of the wellbore 106.
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`[0026]
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`It will be appreciated by those skilled in the art that even
`
`though FIG.
`
`1 depicts the wellbore isolation device 116 as being arranged and
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`operating in the horizontal portion 112 of the wellbore 106,
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`the embodiments
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`described herein are equally applicable for use in portions of the wellbore 106 that
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`are vertical, deviated, or otherwise slanted. It should also be noted that a plurality
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`of wellbore isolation devices 116 may be placed in the wellbore 106.
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`In some
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`embodiments, for example, several (e.g., six or more) wellbore isolation devices
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`116 may be arranged in the wellbore 106 to divide the wellbore 106 into smaller
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`intervals or “zones” for hydraulic stimulation.
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`[0027]
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`FIGS. 2 and 3, with continued reference to FIG. 1, illustrate a
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`cross-sectional view and a perspective view,
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`respectively, of
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`two different
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`exemplary frac plug 200 that may employ one or more of the principles of the
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`present disclosure. As used herein,
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`the term “frac plug” (also referred to as a
`
`“fracturing plug”), and grammatical variants thereof, refers to a wellbore isolation
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`device that isolates fluid flow in at least one direction relative to the plug, typically
`
`the isolation is from above the plug. While the present disclosure uses frac plugs to
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`illustrate various embodiments of degradable slips and degradable slip bands, these
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`embodiments may be applied to the slips and slip bands of the other foregoing
`
`wellbore isolation devices and are within the scope of the present application.
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`[0028]
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`The frac plug 200 may be similar to or the same as the wellbore
`
`isolation device 116 of FIG. 1. Accordingly, the frac plug 200 may be configured to
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`be extended into and seal
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`the wellbore 106 at a target
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`location, and thereby
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`prevent fluid flow past the frac plug 200 for wellbore completion or stimulation
`
`operations. In some embodiments, as illustrated, the wellbore 106 may be lined
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`with the casing 114 or another type of wellbore liner or tubing in which the frac
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`plug 200 may suitably be set. In other embodiments, however, the casing 114 may
`
`be omitted and the frac plug 200 may instead be set or otherwise deployed in an
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`uncompleted or “open-hole” environment.
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`[0029]
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`As illustrated, the frac plug 200 may include a ball cage 204
`
`extending from or otherwise coupled to the upper end of a mandrel 206. A sealing
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`ball, frac ball 208,
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`is disposed in the ball cage 204 and the mandrel 206 defines a
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`longitudinal central flow passage 210. The mandrel 206 also defines a ball seat 212
`
`at its upper end. In other embodiments, the frac ball 208 may be dropped into the
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`conveyance 118 (FIG. 1) to land on top of the frac plug 200 rather than being
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`carried within the ball cage 204.
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`[0030]
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`One or more spacer rings 214 (one shown) may be secured to
`
`the mandrel 206 and otherwise extend thereabout. The spacer ring 214 provides an
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`abutment, which axially retains a set of upper degradable slips 216a that are also
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`positioned circumferentially about the mandrel 206. As illustrated, a set of lower
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`degradable slips 216b may be arranged distally from the upper degradable slips
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`216a. The upper degradable slips 216a constrain the degradable slip bands 215a;
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`and the lower degradable slips 216b are constrained by the degradable slip bands
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`215b. As used herein,
`
`the term “constrained" means at least partially enclosed
`
`within a supporting substance material. The degradable slip bands 215a, 215b may
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`constrain the degradable slips 216a, 216b, respectively, by any known method.
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`Examples of suitable methods may include, but are not limited to, via a press fit,
`
`via a thermal shrink fit, via an adhesive, interference fit, clearance fit, via a snap
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`ring, and the like. For example, the degradable slips 216a, 216b, the degradable
`
`slip bands 215a, 215b, or a combination thereof may be machined from a
`
`degradable metal material. In another example, the degradable slips 216a, 216b,
`
`the degradable slip bands 215a, 215b, or a combination thereof may be cast from
`
`molten or otherwise liquid degradable metal material. In yet another example, the
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`degradable slip bands 215a, 215b may be formed of a degradable polymer.
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`[0031]
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`The degradable slips 216a, 216b have buttons embedded
`
`therein. The buttons 217a, 217b, which may be composed of a degradable metal
`
`material, protrude from the degradable slips 216a, 216b respectively to penetrate
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`or bite a downhole surface and frictionally engage the degradable slips 216a, 216b
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`therewith downhole surface (e.g., a wellbore wall, a tubing string wall, such as
`
`casing string, and the like) when the frac plug 200 is actuated. Although each
`
`degradable slip 216a, 216b is shown having two degradable slip bands 215a, 215b
`
`and three or four buttons 217a, 217b embedded therein, respectfully,
`
`it will be
`
`appreciated that any number of degradable slip bands and buttons, including one or
`
`a plurality (two, three, four, five, six, eight, ten, twenty, and the like) of degradable
`
`slip bands and/or buttons may be embedded in each degradable slip, without
`
`departing from the scope of the present disclosure. Moreover,
`
`the number of
`
`degradable slip bands in the upper degradable slips 216a and lower degradable
`
`slips 216b, and any additional degradable slips included as part of the frac plug
`
`200, may have the same or different number of degradable slip bands, without
`
`departing from the scope of the present disclosure. Additionally, although the
`
`degradable slip bands 215a, 215b shown in FIG. 2 are depicted as rectangular or
`
`square in cross section, the degradable slip bands 215a, 215b may be any other
`
`shape, without departing from the scope of the present disclosure. For example, the
`
`shape of the degradable slips bands may be cylindrically shaped, frustrum shaped,
`
`conical shaped, spheroid shaped, pyramid shaped, polyhedron shaped, octahedron
`
`shaped,
`
`cube
`
`shaped,
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`prism shaped,
`
`hemispheroid
`
`shaped,
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`cone
`
`shaped,
`
`tetrahedron shaped, cuboid shaped, and the like, and any combination thereof,
`
`without departing from the scope of the present disclosure. That is, the degradable
`
`slip bands may be partially one shape and partially one or more other shapes.
`
`[0032]
`
`One or more slip wedges 218 (shown as upper and lower slip
`
`wedges 218a and 218b,
`
`respectively) may also be positioned circumferentially
`
`about the mandrel 206, as described in greater detail below. Collectively, the term
`
`“slip assembly” includes at least the degradable slips 216a, 216b, the degradable
`
`slip bands 215a, 215b, the buttons 217a, 217b, and slip wedges 218a, 218b. In
`
`some instances,
`
`the buttons and slip wedges may be composed of degradable
`
`materials. Accordingly,
`
`in
`
`some embodiments,
`
`the slip assembly may be a
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`degradable slip assembly where all components thereof are at
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`least partially
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`degradable.
`
`[0033]
`
`Alternatively, FIG. 4, with continued reference to FIGS. 2 and 3,
`
`illustrates a perspective view of an upper portion of an exemplary frac plug 300
`
`that may employ one or more of the principles of the present disclosure. FIG. 4,
`
`specifically, illustrates an alternative slip assembly where the remaining portions of
`
`the frac plug 300 correspond to the frac plug 200 of FIGS. 2 and 3. Juxtaposing
`
`upper degradable slips 316a are connected by tabs 321. The slip wedges 318
`
`include fins 319 that are shaped to slide through a space 323 between the
`
`juxtaposing upper degradable slip 316a and break the tabs 321. The degradable
`
`slips 316a then extend outwardly, and the buttons 317a bite into, penetrate, or bite
`
`a downhole surface and frictionally engage the degradable slips 316a with the
`
`downhole surface when the frac plug 200 is actuated.
`
`In embodiments of FIG. 4
`
`and similar embodiments, the slip assembly includes at least the degradable slips
`
`316a with tabs 321 connecting juxtaposing degradable slips 316a,
`
`the buttons
`
`317a, and the slip wedges 318a with fins 319.
`
`In some embodiments,
`
`the slip
`
`assembly may be a degradable slip assembly where all components thereof are at
`
`least partially degradable.
`
`[0034]
`
`In some instances, a hybrid of the embodiment of FIGS. 2 and 3
`
`and the embodiment of FIG. 4 may be implemented where the upper slip assembly
`
`is configured as illustrated and described in FIGS. 2 and 3 and the lower slip
`
`assembly is