HIGH PRESSURE STRIPPING ELEMENTS

Abstract

A stripping element can include a backing plate having a top surface, a bottom surface and a bore, a backing ring having a top, a bottom and a bore, a skeleton having a top, a bottom, a bore, and a radially exterior wall with one or more openings, and an elastomeric stripping body having a top, a bottom and a bore. The top of the backing ring can be coupled to the bottom surface of the backing plate. The top of the skeleton can be coupled to the bottom of the backing ring. The stripping body can be coupled to the backing plate, the backing ring and the skeleton. The backing ring and the skeleton can be encased in the stripping body.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. patent application Ser. No. 18/908,942 filed Oct. 8, 2024, which claims the benefit of U.S. Provisional Patent Application No. 63/595,915 filed Nov. 3, 2023 and U.S. Provisional Patent Application No. 63/607,529 filed Dec. 7, 2023. The entire contents of the aforementioned applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to equipment for subterranean wells (e.g., oil and gas wells) and more specifically relates to high pressure stripping elements and high pressure stripping heads for use with such elements.

BACKGROUND

A stripping head (or “stripper head”) is a gland and packing device bolted to a wellhead or other well equipment that utilizes an expendable stripping element (aka “stripper element” or “stripper”) for surrounding drill pipe or other tubing and stripping, or removing, mud and/or other materials from the exterior surface of the tubing as the tubing is brought out of a wellbore. Stripping heads and elements are also used to seal the annular space between the tubing and well casing during stripping operations, i.e., to help prevent a pressurized well, such as a hydrocarbon well, from flowing uncontrollably. Industry standards require having a stripping head for every string of pipe in the hole on every rig that is working.

Key rating metrics of stripping heads are the pressure rating and the longevity of the stripping element. In some stripping heads, the stripping element rotates with the kelly or drillpipe and lubricant is used. In other stripping heads, the stripping element is stationary and the kelly or drillpipe rotates within the stripping element. In both cases, the rubber material of the stripping elements are degraded over time, as the tubing rotates within and/or moves axially through the stripping element. The pressure rating of traditional stripping heads varies, but typically ranges from about 2400 psi to about 3500 psi.

While traditional stripping heads and elements can be used in some circumstances, a need exists in the art for improved stripping heads and stripping elements.

SUMMARY

Applicant has created new and useful devices, systems and methods for high pressure stripping. Embodiments of the disclosure can advantageously provide for stripping elements, stripping heads, and related systems and assemblies that are relatively simple to operate yet can withstand higher pressures and last substantially longer in the field than traditional solutions. In at least one embodiment, a stripping element according to the disclosure can include a unique flexible skeleton disposed within an elastomeric body for advantageously maximizing the service life of the stripping element under the rigors of stripping operations, e.g., due to contact with rotating and longitudinally moving tubing and tubing joints, mud, well fluids, debris, and high pressures.

In accordance with the present disclosure, improved stripping elements and stripping heads including same are described, as well as methods of making the stripping elements, assembling the stripping heads, and using same, which reduce or overcome shortcomings of previously known stripping elements, stripping heads, and methods.

In at least one embodiment, a stripping element according to the disclosure, such as a stripping element for use with a stripping head, can include a tubular backing plate having a top surface, a bottom surface and a backing plate bore, a tubular backing ring having a top, a bottom and a backing ring bore, a tubular skeleton having a top, a bottom, a skeleton bore, and a radially exterior wall with one or more openings disposed radially through the radially exterior wall, and an elastomeric stripping body having a top, a bottom and a stripping body bore. In at least one embodiment, the top of the backing ring can be fixedly coupled to the bottom surface of the backing plate. In at least one embodiment, the top of the skeleton can be fixedly coupled to the bottom of the backing ring. In at least one embodiment, the stripping body can be coupled to the backing plate, the backing ring and the skeleton. In at least one embodiment, the stripping body can include a first upwardly facing surface disposed adjacent to at least a first portion of the bottom surface of the backing plate. In at least one embodiment, the backing ring and the skeleton can be encased in the stripping body.

In at least one embodiment, the backing plate bore can have a minor inside diameter that is less than both (a) a minor inside diameter of the backing ring bore, and (b) a minor inside diameter of the skeleton bore. In at least one embodiment, the minor inside diameter of the skeleton bore can be less than the minor inside diameter of the backing ring bore. In at least one embodiment, the skeleton can have a length from the top of the skeleton to the bottom of the skeleton, and an inside diameter of the skeleton bore can be constant along the length. In at least one embodiment, the skeleton can have a length from the top of the skeleton to the bottom of the skeleton, and an inside diameter of the skeleton bore can vary along at least a portion of the length. In at least one embodiment, the inside diameter of the skeleton bore can include a top inside diameter at the top of the skeleton and a bottom inside diameter at the bottom of the skeleton, and the top inside diameter can be greater than the bottom inside diameter.

In at least one embodiment, the inside diameter of the skeleton bore can further include an interim inside diameter longitudinally between the top inside diameter and the bottom inside diameter. In at least one embodiment, the interim diameter can be less than the top inside diameter and greater than the bottom inside diameter. In at least one embodiment, the skeleton bore can include a first cylindrical interior surface having the top inside diameter and a second cylindrical interior surface having the bottom inside diameter. In at least one embodiment, the skeleton bore can include an angled interior surface longitudinally between the first cylindrical interior surface and the second cylindrical interior surface.

In at least one embodiment, one or more openings can include a plurality of slots disposed radially through at least a portion of the angled interior surface and at least a portion of the second cylindrical interior surface. In at least one embodiment, the plurality of slots can be angled relative to a radial axis that intersects a central longitudinal axis of the skeleton. In at least one embodiment, the stripping body can include a second upwardly facing surface disposed adjacent to at least a second portion of the bottom surface of the backing plate, the first portion of the bottom surface of the backing plate can be radially exterior of the backing ring, and the second portion of the bottom surface of the backing plate can be radially interior of the backing ring. In at least one embodiment, the second portion of the bottom surface of the backing plate can be disposed at least partially within the backing ring bore. In at least one embodiment, the second portion of the bottom surface of the backing plate can be the bottom surface of a locator configured to center the backing ring relative to the backing plate. In at least one embodiment, the locator can be or include a lip, a groove, or a combination thereof.

In at least one embodiment, the backing ring can have a wall thickness that is greater than a wall thickness of the skeleton. In at least one embodiment, the backing ring can have a major longitudinal dimension, the skeleton can have a major longitudinal dimension, and the major longitudinal dimension of the skeleton can be greater than the major longitudinal dimension of the backing ring. In at least one embodiment, the backing ring and the skeleton can be integral portions of a unitary structure. In at least one embodiment, at least a portion of the skeleton can have a major outside dimension less than a major outside dimension of the backing ring.

In at least one embodiment, the backing ring can include a solid, cylindrical wall. In at least one embodiment, one or more openings can include a plurality of longitudinally-oriented slots disposed radially through the skeleton. In at least one embodiment, the plurality of longitudinally-oriented slots can be disposed about an array of respective radial axes that intersect a central longitudinal axis of the skeleton. In at least one embodiment, the skeleton can have a bottommost surface, and each of the plurality of longitudinally-oriented slots can extend through the bottommost surface of the skeleton.

In at least one embodiment, a stripping element for use with stripping heads can include a one-piece, elastomer body having a top, a bottom, a bore with an inside surface, and an outer surface. In at least one embodiment, the elastomer body can include an upper portion and a lower portion, and the upper portion can include a seal for sealing with an inside surface of a stripping head. In at least one embodiment, a stripping element can include a support disposed at least partially within the elastomer body. In at least one embodiment, the support can include a plurality of holes, slots and/or other openings in or through at least a portion thereof.

In at least one embodiment, a method can include molding an elastomer body according to the disclosure, making a support according to the disclosure, and/or coupling the elastomer body to the support.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element.

FIG. 2 is a perspective view of another one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element.

FIG. 3 is a perspective view of one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element and showing a backing ring that differs from that of FIGS. 1 and 2.

FIG. 4 is a cross-sectional, partial cutaway view of one of many embodiments of a stripping element according to the disclosure, shown upside down and with portions of the elastomer body cut away for illustration.

FIG. 5 is a cross-sectional, partial cutaway view of another one of many embodiments of a stripping element according to the disclosure, shown upside down and with portions of the elastomer body cut away for illustration.

FIG. 6 is a cross-sectional view of the stripping element of FIG. 4.

FIG. 7 is a perspective view of one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element in the absence of the elastomer body for illustration.

FIG. 8 is a perspective view of the backing ring and skeleton of the stripping element of FIG. 7.

FIG. 9 is a perspective, bi-cross-sectional view of the stripping element of FIG. 7, including the elastomer body.

FIG. 10 is a perspective view of one of many embodiments of a stripping head according to the disclosure, in a partially open position.

FIG. 11 is a perspective view of one of many embodiments of a stripping head according to the disclosure, in a closed position.

FIG. 12 is a top view of one of many embodiments of a stripping head according to the disclosure, in a closed position.

FIG. 13 is a side cross-sectional view of one of many embodiments of a stripping head according to the disclosure, including a stripping element of FIG. 5.

FIG. 14 is a schematic top view of one of many embodiments of a stripping head according to the disclosure comprising a port.

FIG. 15 is a side cross-sectional view of a portion of the stripping head of FIG. 14.

FIG. 16 is a detail view of a portion of FIG. 15.

FIG. 17 is a flow chart illustrating one of many embodiments of a method according to the disclosure.

DETAILED DESCRIPTION

The figures described above and the written description of specific structures and functions below are not presented to limit the scope of what Applicant has invented or the scope of the appended claims. Rather, the figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present inventions will require numerous implementation-specific decisions to achieve the developer's ultimate goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related and other constraints, which may vary by specific implementation, location and from time to time. While a developer's efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of skill in this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms.

The use of a singular term, such as, but not limited to, “a,” is not intended as limiting of the number of items. Also, the use of relational terms, such as, but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the like are used in the written description for clarity in specific reference to the figures and are not intended to limit the scope of the inventions or the appended claims. The terms “including” and “such as” are illustrative and not limitative. The terms “couple,” “coupled,” “coupling,” “coupler,” and like terms are used broadly herein and can include any method or device for securing, binding, bonding, fastening, attaching, joining, inserting therein, forming thereon or therein, communicating, or otherwise associating, for example, mechanically, magnetically, electrically, chemically, operably, directly or indirectly with intermediate elements, one or more pieces of members together and can further include without limitation integrally forming one functional member with another in a unity fashion. The coupling can occur in any direction, including rotationally. Further, all parts and components of the disclosure that are capable of being physically embodied inherently include imaginary and real characteristics regardless of whether such characteristics are expressly described herein, including but not limited to characteristics such as axes, ends, inner and outer surfaces, interior spaces, tops, bottoms, sides, boundaries, dimensions (e.g., height, length, width, thickness), mass, weight, volume and density, among others. Relative terms such as “first,” “second,” and the like are used for convenience and clarity, and are not limitative unless otherwise indicated. The term “about” and like terms are inclusive of exactness.

Applicant has created new and useful devices, systems and methods for high pressure stripping. Embodiments of the disclosure can advantageously provide for stripping elements, stripping heads, and related systems and assemblies that are relatively simple to operate yet can withstand higher pressures and last substantially longer in the field than traditional solutions. In at least one embodiment, a stripping element according to the disclosure can include a unique flexible skeleton disposed within an elastomeric body for advantageously maximizing the service life of the stripping element under the rigors of stripping operations, e.g., due to contact with rotating and longitudinally moving tubing and tubing joints, mud, well fluids, debris, and high pressures.

FIG. 1 is a perspective view of one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element. FIG. 2 is a perspective view of another one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element. FIG. 3 is a perspective view of one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element and showing a backing ring that differs from that of FIGS. 1 and 2. FIG. 4 is a cross-sectional, partial cutaway view of one of many embodiments of a stripping element according to the disclosure, shown upside down and with portions of the elastomer body cut away for illustration. FIG. 5 is a cross-sectional, partial cutaway view of another one of many embodiments of a stripping element according to the disclosure, shown upside down and with portions of the elastomer body cut away for illustration. FIG. 6 is a cross-sectional view of the stripping element of FIG. 4. FIG. 7 is a perspective view of one of many embodiments of a stripping element according to the disclosure, showing portions of the bottom of the stripping element in the absence of the elastomer body for illustration. FIG. 8 is a perspective view of the backing ring and skeleton of the stripping element of FIG. 7. FIG. 9 is a perspective, bi-cross-sectional view of the stripping element of FIG. 7, including the elastomer body. FIG. 10 is a perspective view of one of many embodiments of a stripping head according to the disclosure, in a partially open position. FIG. 11 is a perspective view of one of many embodiments of a stripping head according to the disclosure, in a closed position. FIG. 12 is a top view of one of many embodiments of a stripping head according to the disclosure, in a closed position. FIG. 13 is a side cross-sectional view of one of many embodiments of a stripping head according to the disclosure, including a stripping element of FIG. 5. FIG. 14 is a schematic top view of one of many embodiments of a stripping head according to the disclosure comprising a port. FIG. 15 is a side cross-sectional view of a portion of the stripping head of FIG. 14. FIG. 16 is a detail view of a portion of FIG. 15. FIG. 17 is a flow chart illustrating one of many embodiments of a method according to the disclosure. FIGS. 1-17 are described in conjunction with one another.

In at least one embodiment, a stripping element (aka “stripper element” or “stripper”) 100 according to the disclosure can include a support 102 for supporting one or more other components of the stripping element 100, and an elastomer body 2, or elastomeric stripping body, coupled to the support 102 for elastically and sealingly cooperating with well equipment (e.g., pipes and joints) during stripping operations. In at least one embodiment, elastomer body 2 can be or include a unitary elastomeric body. In at least one embodiment, elastomer body 2 can be or include a one-piece, formed, elastomeric body. In at least one embodiment, at least a portion of body 102 can be annular and/or cylindrical (i.e., at least substantially cylindrical). In at least one embodiment, elastomer body 2 can be tubular. In at least one embodiment, elastomer body 2 can include a top 4, a bottom 6, an outer surface 12, and a central longitudinal passage or bore 8, such as a stripping body bore, having an inside surface 10.

In at least one embodiment, elastomer body 2 can include an upper portion 14, such as a base, for cooperating with support 102, and a lower portion 16, such as a nose, extending downwardly from upper portion 14 for receiving a tubing string during stripping operations. One or both of upper and lower portions 14, 16 can have or include angled exterior surfaces and/or can include at least a portion having a general shape of a truncated cone. In at least one embodiment, bore 8 of elastomer body 2 can have tapered mouths 11, 13 for facilitating stripping operations. In at least one embodiment, mouth 11 can have a cone angle θ ranging from about 30 to about 60 degrees, and mouth 13 can have a cone angle ρ ranging from about 30 to about 60 degrees, for example. Angles θ and ρ can be the same or different.

In at least one embodiment, elastomer body 2 can include one or more seals 18 on upper portion 14, which can be or include an annular lip or other radially outer lip, for sealingly cooperating with one or more surfaces of a stripping head 300 (further described below), such as the wall of a bore 33 (see, e.g., FIG. 13), to contain wellbore pressure during stripping operations. In at least one embodiment, seal 18 can be or include a wing 132 having an outer surface 134 for engaging a bore, a downwardly facing nose 136, and a recess 138, such as a void, chamber, groove, or annulus, disposed radially between nose 136 and an exterior surface of lower portion 16 of elastomer body 2. In at least one embodiment, outer surface 134 can taper radially outwardly from top to bottom at an angle A relative to central longitudinal axis LA of stripping element 100. In at least one embodiment, angle A can be from 15 degrees to 30 degrees, for example, and the radially outward taper of wing 132 can advantageously improve sealing communication with a bore 33 of a stripping head 300.

In at least one embodiment, recess 138 can advantageously provide surface area on which wellbore pressure P can act behind, or radially interior of, nose 136, which also improves sealing communication with bore 33 by way of utilizing wellbore pressure P to bias nose 136 radially outwardly, towards sealing engagement with bore 33. In at least one embodiment, recess 138 can advantageously have a profile that is at least partially curved. In at least one embodiment, recess 138 can advantageously have a profile that is partially curved and partially linear. In at least one embodiment, recess 138 can advantageously have a profile that includes one or more obtuse angles. In at least one embodiment, the tapered outer surface of lower portion 16 of stripping element 100 can provide surface area on which wellbore pressure P can act for purposes of utilizing wellbore pressure P to bias lower portion 16 radially inwardly, towards sealing and stripping engagement with a portion of a tubing string disposed therein. In at least one embodiment, lower portion 16 can advantageously have a longitudinal dimension greater than a longitudinal dimension of wing 132 of seal 18.

In at least one embodiment, a stripping element 100 according to the disclosure, or a portion thereof, such as support 102, can be or include metal structure coupled to body 2 and arranged for supporting body 2 during stripping operations, such as to enable body 2 to resiliently withstand the rigors of stripping operations and provide for superior operational life of stripping element 100 as a whole. In at least one embodiment, support 102 can include a backing plate 30, such as a base, disk, or substrate, for coupling with a stripping head 300 and supporting one or more other components of stripping element 100. In at least one embodiment, backing plate 30 can be tubular, and can include a top surface, a bottom surface, and one or more openings, such as a backing plate bore 126. In at least one embodiment, backing plate 30 can be or include an annular structure made of relatively thick metal (e.g., steel), and can be arranged for coupling with a stripping head 300 (further described below) and supporting resilient operation of stripping element 100 under the relative harsh environment of stripping operations. In at least one embodiment, backing plate bore 126 can have a tapered mouth 31 for facilitating stripping operations.

In at least one embodiment, a stripping element 100 according to the disclosure, or a portion thereof, such as support 102, can include one or more supporting structures coupled to backing plate 30 for further supporting body 2 during stripping operations. In at least one embodiment, support 102 can include a backing ring 23, or retention ring, coupled to backing plate 30 and extending into elastomer body 2 for providing structural support and rigidity to at least a portion of elastomer body 2 and stripping element 100. In at least one embodiment, backing ring 23 can be or include a tubular metal ring. In at least one embodiment, the backing ring 23 can include a solid, cylindrical wall. In at least one embodiment, backing ring 23 can have a top, a bottom, and a backing ring bore 128, and the top of the backing ring 23 can be fixedly coupled to the bottom of the backing plate 30, such as to one or more surfaces of the bottom of the backing plate 30, radially exterior of backing plate bore 126. In at least one embodiment, backing ring 23 can be welded to backing plate 30, which can advantageously keep backing ring 23 in place relative to backing plate 30, both during use of stripping element 100 and under the high pressures associated with molding of elastomer body 2 onto support 102.

In at least one embodiment, backing plate 30 can include one or more locators 27, such as a lip, groove, boss, stop, wall, or any combination thereof, for supporting positioning of backing ring 23 relative to backing plate 30 during manufacturing and providing structural integrity to stripping element 100. In at least one embodiment, locator 27 can be or include a cylindrical lip machined into the bottom face of backing plate 30. In at least one embodiment, locator 27 can be or include a face groove machined into the bottom face of backing plate 30. Locator 27 can be continuous, or segmented. In at least one embodiment, locator 27 can be disposed on the bottom surface of backing plate 30, radially exterior of backing plate bore 126, and a radially interior surface of backing ring 23 can be disposed adjacent to a radially exterior surface of locator 27, which can, but need not, include being in direct contact. Similarly, lower edge 23A of backing ring 23 can be disposed against portion 30A of the bottom surface of backing plate 30. In this manner, locator 27 can prevent lateral movement of backing ring 23 relative to backing plate 30, including under the rigors of stripping operations, and thus prevent, for example, backing ring 23 from moving into the path of backing plate bore 126.

In at least one embodiment, backing ring 23, or backing ring bore 128, can have an internal diameter greater than an internal diameter of backing plate bore 128, and a length (or height) extending longitudinally downwardly from a bottom surface of backing plate 30. In at least one embodiment, the length of backing ring 23 can advantageously be more than 50% of the distance from the bottom surface of backing plate 30 to the recess 138 of seal 18. In at least one embodiment, the length of backing ring 23 can advantageously be more than 70% of the distance from the bottom surface of backing plate 30 to the recess 138 of seal 18. In at least one embodiment, the length of backing ring 23 can advantageously be at least about the same as the distance from the bottom surface of backing plate 30 to the recess 138 of seal 18.

In at least one embodiment, backing ring 23 can have one or more openings 26 disposed radially through the body or wall of backing ring 23. For example, in at least one embodiment, backing ring 23 can include an array of circular openings 26 disposed there through, and the array of circular openings 26 can be equally spaced (i.e., radially) about axis LA. As illustrated in FIG. 4 for exemplary purposes, in at least one embodiment, the openings 26 can be located longitudinally closer to the bottom of backing ring 23 than to the top of backing ring 23, and can have diameters of from about 30% to about 60% of the length of backing ring 23. While openings 26 are shown to be of uniform size, shape and location for illustrative purposes, in at least one embodiment, the sizes, shapes, locations, or any combination thereof, of openings 26 can vary about or along backing ring 23 (or a portion thereof, such as a skeleton), as required or desired for a given implementation of the disclosure. In this manner, backing ring 23 can advantageously provide for both increased rigidity along a portion of stripper element 100, and increased flexibility along a portion of stripper element 100, in a direction from backing plate 30 downwardly. As a result, stripper element 100 can provide for a superior combination of both failure resistance and adequate flexibility for cooperating with tubing string components of varying outside dimensions during stripping operations.

In at least one embodiment, a stripping element 100 according to the disclosure, or a portion thereof, such as support 102, can include a skeleton 25, such as a tubular skeleton, coupled to backing ring 23 and extending downwardly from back ring 23. In at least one embodiment, skeleton 25 can include a top, a bottom, a skeleton bore 142, and a body or radially exterior wall with one or more openings 24 disposed radially through the body or radially exterior wall of skeleton 25. For example, in at least one embodiment, skeleton 25 can include an array of openings 24 disposed there through, and the array of openings 24 can be equally spaced (i.e., radially) about axis LA. In at least one embodiment, the openings 23, 24 in a support 102 according to the disclosure, including without limitation the locations, shapes, number, and relative sizes in relation to that of all or a portion of the remainder of support 102, can advantageously provide for both a strong bond between support 102 and elastomer body 2 and superior flexibility when, e.g., a tubing coupler 56 or other tool joint passes through stripping element 100 during stripping operations.

In at least one embodiment, the top of skeleton 25 can be fixedly coupled to the bottom of backing ring 23, which can, but need not, including being formed integrally with backing ring 23. In at least one embodiment, elastomer body 2, (aka stripping body) can be coupled to the backing plate, the backing ring and the skeleton. In at least one embodiment, elastomer body 2 can include a first (or other) upwardly facing surface disposed adjacent to at least a first (or other) portion of the bottom surface of the backing plate 30, such as a portion radially exterior of backing ring 30. In at least one embodiment, elastomer body 2 can include a second (or other) upwardly facing surface disposed adjacent to at least a second (or other) portion of the bottom surface of the backing plate 30, such as a portion radially interior of backing ring 30, which can be or include at least a portion of locator 27.

In at least one embodiment, backing ring 23 and skeleton 25 can be at least partially enclosed in or surrounded by elastomer body 2. In at least one embodiment, all exterior surfaces of backing ring 23 and skeleton 25 can be surrounded by elastomer body 2. In at least one embodiment, backing ring 23 and skeleton 25 can be encased in elastomer body 2 (see, e.g., FIGS. 4-6 and 9). In at least one embodiment, elastomer body 2 can line all or a portion of backing plate bore 126 (see, e.g., FIGS. 4-6 and 9).

In at least one embodiment, the backing plate bore 126 can have a minor inside diameter that is less than both a minor inside diameter of the backing ring bore 128 and a minor inside diameter of the skeleton bore 142. In at least one embodiment, the minor inside diameter of the skeleton bore 142 can be less than the minor inside diameter of the backing ring bore 128. In at least one embodiment, the skeleton 25 can have a length from the top of the skeleton to the bottom of the skeleton, and an inside diameter of the skeleton bore 142 can be constant along the length (see, e.g., FIG. 5). In at least one embodiment, the backing ring 23 and/or the skeleton 25 can have a major dimension smaller than a minor dimension of wing 132. In at least one embodiment, the backing ring 23 and/or the skeleton 25 can be disposed radially inwardly of wing 132. In at least one embodiment, two or more of the backing plate bore 126, the backing ring bore 128, and the skeleton bore 142 can be concentric. In at least one embodiment, two or more of the backing plate bore 126, the backing ring bore 128, and the skeleton bore 142 can be cylindrical. In at least one embodiment, two or more of the backing plate bore 126, the backing ring bore 128, and the skeleton bore 142 can be parallel.

In at least one embodiment, the openings 24 in skeleton 25 can be or include a plurality of slots, such as longitudinally-oriented slots, disposed radially through at least a portion of skeleton 25, such as at least most of the length of skeleton 25. In at least one embodiment, the plurality of longitudinally-oriented slots can be disposed about an array of respective radial axes that intersect axis LA, or a central longitudinal axis of the skeleton 25. In at least one embodiment, the skeleton 25 can have a bottommost surface, and each of the plurality of longitudinally-oriented slots can extend through the bottommost surface of the skeleton 25, such as at the bottom ends 24B of the slots. In at least one embodiment, each of the plurality of longitudinally-oriented slots can stop short of the top of skeleton 25, such as at the top ends 24B of the slots. In at least one embodiment, the top ends 24B of the slots can be rounded or otherwise curved. In at least one embodiment, the top ends 24B of the slots can be another shape, such as squared. While openings 24 are shown to be of uniform size, shape and location for illustrative purposes, in at least one embodiment, the sizes, shapes, locations, or any combination thereof, of openings 24 can vary about or along skeleton 25, as required or desired for a given implementation of the disclosure.

In at least one embodiment, the backing ring 23 can have a wall thickness that is greater than a wall thickness of the skeleton 25. In at least one embodiment, the backing ring 23 can have a major longitudinal dimension, the skeleton 25 can have a major longitudinal dimension, and the major longitudinal dimension of the skeleton 25 can be greater than the major longitudinal dimension of the backing ring 23. In at least one embodiment, the backing ring 23 and the skeleton 25 can be integral portions of a unitary structure. In at least one embodiment, at least a portion of the skeleton 25 can have a major outside dimension less than a major outside dimension of the backing ring 23.

In the aforementioned manners, backing ring 23 and skeleton 25 can advantageously provide for both increased rigidity along a portion of stripper element 100, and increased flexibility along a portion of stripper element 100, in a direction from backing plate 30 downwardly. As a result, stripper element 100 can provide for a superior combination of both extrusion failure resistance and adequate flexibility for cooperating with tubing string components of varying outside dimensions during stripping operations.

In at least one embodiment, the skeleton 25 can have a length from the top of the skeleton to the bottom of the skeleton, and an inside diameter of the skeleton bore 142 can vary along at least a portion of the length (see, e.g., FIGS. 7-9). In at least one embodiment, the inside diameter of the skeleton bore 142 can include a top inside diameter D1 at the top of the skeleton 25 and a bottom inside diameter D2 at the bottom of the skeleton 25, and the top inside diameter can be greater than the bottom inside diameter.

In at least one embodiment, the inside diameter of the skeleton bore 142 can include an interim inside diameter D3 longitudinally between the top inside diameter and the bottom inside diameter. In at least one embodiment, the interim diameter D3 can be less than the top inside diameter D1 and greater than the bottom inside diameter D2. In at least one embodiment, the skeleton bore 142 can include a first cylindrical interior surface having the top inside diameter D1 and a second cylindrical interior surface having the bottom inside diameter D2. In at least one embodiment, the skeleton bore 142 can include an angled or tapered portion 144 having an angled interior surface longitudinally between the first cylindrical interior surface and the second cylindrical interior surface.

In at least one embodiment, the openings 24 in skeleton 25 can be or include a plurality of slots, such as longitudinally oriented slots, disposed radially through at least a portion of skeleton 25, such as along at least a portion of the length of the angled interior surface and/or at least a portion of the second cylindrical interior surface. In at least one embodiment, the plurality of slots can be parallel to axis LA. In at least one embodiment, the plurality of slots can be concentric about axis LA. In at least one embodiment, the plurality of slots can be perpendicular to corresponding radial axes that intersect axis LA. In at least one embodiment, the plurality of slots can be angled relative to corresponding radial axes that intersect a central longitudinal axis of the skeleton 25, such as axis LA. While the angled slots are shown to be of uniform size, shape and location for illustrative purposes, in at least one embodiment, the sizes, shapes, locations, or any combination thereof, of the angled slots can vary about or along skeleton 25, as required or desired for a given implementation of the disclosure. In at least one embodiment, the plurality of slots can be angled at or about 15 degrees. In at least one embodiment, the plurality of slots can be angled from at or about 5 degrees to at or about 60 degrees.

In the aforementioned manners, backing ring 23 and skeleton 25 can advantageously provide for both increased rigidity along a portion of stripper element 100, and increased flexibility along a portion of stripper element 100, in a direction from backing plate 30 downwardly. As a result, stripper element 100 can provide for a superior combination of both extrusion failure resistance and adequate flexibility for cooperating with tubing string components of varying outside dimensions during stripping operations.

In at least one embodiment, some or all of support 102 can be metal, such as steel, stainless steel, or another steel alloy. In at least one embodiment, some or all of elastomer body 2 can be or include one or more natural elastomers, one or more synthetic elastomers, or any combination or mixture thereof. Examples of such elastomers include, but are not limited to, natural rubber (NR), otherwise known as isoprene, styrene-butadiene rubber (SBR), butyl rubber (IIR), nitrile rubber (otherwise known as NBR rubber and Buna-N), hydrogenated nitrile (HNBR), neoprene (CR), ethylene propylene diene monomer (EPDM) rubber, fluoroelastomers, and polyurethanes (AU).

In at least one embodiment, a stripping head 300 according to the disclosure, such as a stripping head assembly or system, can include a stripping head body 32 and a clamp 34 for cooperating with stripping element 100 during stripping operations. In at least one embodiment, stripping head 300 can include a flange 44 having a plurality of holes 42 for cooperating with fasteners (e.g., bolts) and/or one or more seals 60 (e.g., a chevron seal) to couple stripping head 300 to a wellhead or other equipment in fluid communication with a wellbore (not shown), and clamp 34 can be arranged for selectively and removably coupled a stripping element 100 at least partially within a bore 33 of stripping head 300. For example, clamp 34 can include a pair of rotatable jaws 34A, 34B having radially inwardly oriented grooves 35 arranged to couple with a lip 36 of stripping head body 32 and to lock stripping element 100 in an operable position relative to stripping head body 32.

In at least one embodiment, stripping head 300 can include a bore 33 having a diameter 50, such as a diameter from about 6 inches to about 8 inches, or another dimension required or desired in accordance with an implementation of the disclosure. In the exemplary embodiment of FIG. 13, the broken lines illustrate the normal, relaxed, or initial dimensions of the elastomer body 2 of one embodiment of a stripping element 100 according to the disclosure, i.e., prior to interacting with a tubing string during stripping operations. The inside diameter 52 of central through passage 8 of elastomer body 2 is smaller initially than the outside diameter 58 of tubing 54 (e.g., pipe) and the outside diameter of the relatively larger tubing couplings 56, e.g., at the connections or joints along a tubing string. As tubing 54 and coupling 56 are moved longitudinally through stripping element 100, elastomer body 2 tightly surrounds tubing 54 and coupling 56 to strip mud or other contents off of the outside surfaces of tubing 54 and coupling 56, and elastomer body 2 is forced (aka “squeezed”) radially outwardly (and/or upwardly or downwardly), including in the area beneath backing plate 30 and often into (or at least towards) an extrusion gap 112 radially between an interior surface of backing plate 30 and an exterior surface of tubing 54 or coupling 56 (as the case may be). Stripping elements can be exposed to substantial friction, temperature, pressure, and forces during stripping operations, and a common mode of failure among traditional elements involves forcing of the elastomer (or a portion thereof, as the case may be) upwardly through the extrusion gap 112, thereby rendering the element inoperable and requiring replacement with a new element before operations can continue. However, stripping elements 100 according to the disclosure advantageously provide for improved circumferentially flexibility, and improved resistance to failure via extrusion through the extrusion gap 112, as tubing 54 and each coupling 56 passes through element 100. For example, in at least some cases, a stripping element 100 according to the disclosure can provide a 5-to-1 lifespan advantage over other elements.

In at least one embodiment, the bore 33 of stripping head 300 can include a seat 114, such as one or more grooves, notches, or contours, for coupling with backing plate 30 to position stripping element 100 relative to bore 33 and prevent stripping element 100 from moving downwardly during stripping operations. In at least one embodiment, clamp 34 can have a closed position and one or both jaws 34A, 34B can have a bottom surface or other portion positioned above stripping element 100, such as adjacent to and/or in direct contact with a top surface of backing plate 30, for preventing stripping element 100 from moving upwardly during stripping operations. In at least one embodiment, stripping head 300 can include one or more locks for securely maintaining clamp 34 in the closed positioned during stripping operations. For example, in at least one embodiment, one of jaws 34A, 34B can have one end of a swing bolt 38 rotatably coupled to the jaw and the other of the jaws 34A, 34B can include a seat 116 for securely coupling with a head 118 (e.g., a nut) arranged to be removably coupled with another end of the swing bolt 38. In at least one embodiment, seat 116 can advantageously be or include one or more flat surfaces 122 and/or one or more lips 124 for supporting a secure connection with head 118 and resisting accidental loosening and/or uncoupling of jaws 34A, 34B. In at least one embodiment, jaws 34A, 34B can advantageously include a groove 40 for receiving at least a portion of swing bolt 38 (e.g., in the closed position), which can help prevent damage to swing bolt 38 and/or further support a secure connection with head 118 and resistance of accidental loosening and/or uncoupling of jaws 34A, 34B.

In at least one embodiment, the jaws 34A, 34B of stripping head 300 can have hinge points 148, such as respective axes of rotation, disposed radially within an outside dimension of stripping head body 32 or a portion thereof, such as lip 36. In at least one embodiment, the hinge points 148 of the jaws 34A, 34B can be laterally spaced from one another. In at least one embodiment, the rear, or hinged, ends of jaws 34A, 34B can be contoured or profiled (see, e.g., FIG. 12) to avoid interfering with one another when clamp 34 is open, which can include a fully open position. In this manner, a stripping head 300 according to the disclosure can advantageously provide for a more compact, convenient and/or robust structure versus traditional stripping heads.

In at least one embodiment, stripping head body 32 can be or include a unitary, metal structure and, for example, can be machined and/or forged (e.g., instead of cast), and absent of welds or the like. In at least one embodiment, such a structure can advantageously resist failure substantially better than traditional stripping head bodies, such as failure due to cyclic stress. In at least one embodiment, such a structure can eliminate a need for pull testing (tensile testing) in offshore applications. In at least one embodiment, stripping head 300 can include one or more lifting features 39, such as an anchor point, ear, through hole, eye, D-ring block, or the like, formed therein or coupled thereto for cooperating with one or more manipulator cables or chains (not shown) to transport or position stripping head 300. In at least one embodiment, one or more lifting features 39 can be located on opposite sides of stripping head 300 and/or otherwise positioned for safe and convenient cooperation with a rig hoist, crane, or the like, such as during alignment with and/or connection to other well-related equipment. In at least one embodiment, stripping head 300 can include one or more ports 70, such as an inlet or outlet for fluid communication with at least a portion of bore 33 (and/or a well bore with which stripping head 300 is utilized). In at least one embodiment, one or more ports 70 can be or include a threaded connection for cooperating with one or more fluid fittings, e.g., to provide for fluid flow out of bore 33 and/or pressure readings within bore 33. In at least one embodiment, one or more ports 70 can be disposed adjacent to and/or beneath a stripping element 100 coupled to stripping head 300. In at least one embodiment, one or more ports 70 can be positioned at an angle alpha ranging from about 40 to about 50 degrees offset from a centerline of bore 33 or stripping head 300.

In at least one embodiment, a method according to the disclosure, such as a method of making a stripping element, can include providing or otherwise utilizing a mold for forming an elastomer body according to the disclosure. In at least one embodiment, a method can include selecting an elastomer for the body. In at least one embodiment, a method can include positioning a support according to the disclosure within or otherwise relative to the mold. In at least one embodiment, a method can include filling at least a portion of the mold with an elastomer. In at least one embodiment, a method can include surrounding at least a portion of the support with the elastomer. In at least one embodiment, a method can include heating the mold and the elastomer, which can include heating to one or more temperatures sufficient to cause the elastomer to flow and/or to form the elastomer body. In at least one embodiment, a method can include coupling the elastomer body to the support. In at least one embodiment, a method can include cooling the mold, the elastomer and/or the support, which can include active cooling or passive cooling, such as cooling under ambient conditions.

In at least one embodiment, a method 500 according to the disclosure can be or include a method of making a stripping element according to the disclosure (Box 502). In at least one embodiment, a method can include providing or otherwise utilizing a mold for forming an elastomer body according to the disclosure, such as a body having a top, a bottom, a central longitudinal through passage with an inside surface, and an outer surface, an upper portion, a lower portion, a skirt, an annulus, a seal, or any combination thereof (Box 504). In at least one embodiment, a method can include selecting an elastomer (Box 506). In at least one embodiment, a method can include selecting a support according to the disclosure (Box 508). In at least one embodiment, a method can include welding or brazing a backing ring and/or skeleton to a backing plate, which can include coupling an edge of a cylindrical ring to an insert or disk, such as a steel insert or disk (Box 510). In at least one embodiment, a method can include positioning a support within or otherwise relative to the mold (Box 512). In at least one embodiment, a method can include filling at least a portion of the mold with an elastomer and/or surrounding at least a portion of a support with the elastomer (e.g., except for an edge or surface of a support disposed against another component) (Box 514). In at least one embodiment, a method can include heating the mold and the elastomer, such as to one or more temperatures for causing the elastomer to flow and/or to form the elastomer body (Box 516). In at least one embodiment, a method can include coupling the elastomer body to the support. In at least one embodiment, a method can include cooling the mold, the elastomer and/or the support, which can include active cooling or passive cooling, such as cooling under ambient conditions (Box 518).

Stripping elements according to the disclosure can be arranged for use with tubing of any of various sizes, such as tubing having an external diameter from 2⅜ inches to 3½ inches, or larger or smaller, as required or desired for an implementation of the disclosure. In at least one embodiment, for tubing having an external diameter of 2⅜ inches, for example, an initial inside diameter of a stripping element bore according to the disclosure can be from about 1.35 inches to about 1.41 inches. This can be expressed as a “squeeze factor” ranging from about 0.56 to about 0.59. Similar squeeze factors can be applied to tubing of different sizes. Stripping elements and heads according to the disclosure can be arranged for exposure to wellbore pressures from 1,000 psi to 4,000 psi, or higher, such as may be experienced during frac plug drilling operations.

In at least one embodiment, a stripping element according to the disclosure, such as a stripping element for use with a stripping head, can include a tubular backing plate having a top surface, a bottom surface and a backing plate bore, a tubular backing ring having a top, a bottom and a backing ring bore, a tubular skeleton having a top, a bottom, a skeleton bore, and a radially exterior wall with one or more openings disposed radially through the radially exterior wall, and an elastomeric stripping body having a top, a bottom and a stripping body bore. In at least one embodiment, the top of the backing ring can be fixedly coupled to the bottom surface of the backing plate. In at least one embodiment, the top of the skeleton can be fixedly coupled to the bottom of the backing ring. In at least one embodiment, the stripping body can be coupled to the backing plate, the backing ring and the skeleton. In at least one embodiment, the stripping body can include a first upwardly facing surface disposed adjacent to at least a first portion of the bottom surface of the backing plate. In at least one embodiment, the backing ring and the skeleton can be encased in the stripping body.

In at least one embodiment, the backing plate bore can have a minor inside diameter that is less than both (a) a minor inside diameter of the backing ring bore, and (b) a minor inside diameter of the skeleton bore. In at least one embodiment, the minor inside diameter of the skeleton bore can be less than the minor inside diameter of the backing ring bore. In at least one embodiment, the skeleton can have a length from the top of the skeleton to the bottom of the skeleton, and an inside diameter of the skeleton bore can be constant along the length. In at least one embodiment, the skeleton can have a length from the top of the skeleton to the bottom of the skeleton, and an inside diameter of the skeleton bore can vary along at least a portion of the length. In at least one embodiment, the inside diameter of the skeleton bore can include a top inside diameter at the top of the skeleton and a bottom inside diameter at the bottom of the skeleton, and the top inside diameter can be greater than the bottom inside diameter.

In at least one embodiment, the inside diameter of the skeleton bore can further include an interim inside diameter longitudinally between the top inside diameter and the bottom inside diameter. In at least one embodiment, the interim diameter can be less than the top inside diameter and greater than the bottom inside diameter. In at least one embodiment, the skeleton bore can include a first cylindrical interior surface having the top inside diameter and a second cylindrical interior surface having the bottom inside diameter. In at least one embodiment, the skeleton bore can include an angled interior surface longitudinally between the first cylindrical interior surface and the second cylindrical interior surface.

In at least one embodiment, one or more openings can include a plurality of slots disposed radially through at least a portion of the angled interior surface and at least a portion of the second cylindrical interior surface. In at least one embodiment, the plurality of slots can be angled relative to a radial axis that intersects a central longitudinal axis of the skeleton. In at least one embodiment, the stripping body can include a second upwardly facing surface disposed adjacent to at least a second portion of the bottom surface of the backing plate, the first portion of the bottom surface of the backing plate can be radially exterior of the backing ring, and the second portion of the bottom surface of the backing plate can be radially interior of the backing ring. In at least one embodiment, the second portion of the bottom surface of the backing plate can be disposed at least partially within the backing ring bore. In at least one embodiment, the second portion of the bottom surface of the backing plate can be the bottom surface of a locator configured to center the backing ring relative to the backing plate. In at least one embodiment, the locator can be or include a lip, a groove, or a combination thereof.

In at least one embodiment, the backing ring can have a wall thickness that is greater than a wall thickness of the skeleton. In at least one embodiment, the backing ring can have a major longitudinal dimension, the skeleton can have a major longitudinal dimension, and the major longitudinal dimension of the skeleton can be greater than the major longitudinal dimension of the backing ring. In at least one embodiment, the backing ring and the skeleton can be integral portions of a unitary structure. In at least one embodiment, at least a portion of the skeleton can have a major outside dimension less than a major outside dimension of the backing ring.

In at least one embodiment, the backing ring can include a solid, cylindrical wall. In at least one embodiment, one or more openings can include a plurality of longitudinally-oriented slots disposed radially through the skeleton. In at least one embodiment, the plurality of longitudinally-oriented slots can be disposed about an array of respective radial axes that intersect a central longitudinal axis of the skeleton. In at least one embodiment, the skeleton can have a bottommost surface, and each of the plurality of longitudinally-oriented slots can extend through the bottommost surface of the skeleton.

Other and further embodiments utilizing one or more aspects of the disclosure can be devised without departing from the spirit of Applicant's disclosure. For example, the devices, systems and methods can be implemented for numerous different types and sizes in numerous different industries. Further, the various methods and embodiments of the devices, systems and methods can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements can include plural elements and vice versa. The order of steps can occur in a variety of sequences unless otherwise specifically limited. The various steps described herein can be combined with other steps, interlineated with the stated steps, and/or split into multiple steps. Similarly, elements have been described functionally and can be embodied as separate components or can be combined into components having multiple functions.

The inventions have been described in the context of preferred and other embodiments and not every embodiment of the inventions has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art having the benefits of the present disclosure. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the inventions conceived of by the Applicant, but rather, in conformity with the patent laws, Applicant intends to fully protect all such modifications and improvements that come within the scope or range of equivalents of the following claims.

Claims

1. A stripping element for use with a stripping head, the stripping element comprising:

a tubular backing plate having a top surface, a bottom surface and a backing plate bore;

a tubular backing ring having a top, a bottom and a backing ring bore;

a tubular skeleton having a top, a bottom, a skeleton bore, and a radially exterior wall with one or more openings disposed radially through the radially exterior wall; and

an elastomeric stripping body having a top, a bottom and a stripping body bore;

wherein the top of the backing ring is fixedly coupled to the bottom surface of the backing plate;

wherein the top of the skeleton is fixedly coupled to the bottom of the backing ring;

wherein the stripping body is coupled to the backing plate, the backing ring and the skeleton;

wherein the stripping body comprises a first upwardly facing surface disposed adjacent to at least a first portion of the bottom surface of the backing plate; and

wherein the backing ring and the skeleton are encased in the stripping body.

2. The stripping element as set forth in claim 1, wherein the backing plate bore has a minor inside diameter that is less than both (a) a minor inside diameter of the backing ring bore, and (b) a minor inside diameter of the skeleton bore.

3. The stripping element as set forth in claim 2, wherein the minor inside diameter of the skeleton bore is less than the minor inside diameter of the backing ring bore.

4. The stripping element as set forth in claim 1, wherein the skeleton has a length from the top of the skeleton to the bottom of the skeleton, and wherein an inside diameter of the skeleton bore is constant along the length.

5. The stripping element as set forth in claim 1, wherein the skeleton has a length from the top of the skeleton to the bottom of the skeleton, and wherein an inside diameter of the skeleton bore varies along at least a portion of the length.

6. The stripping element as set forth in claim 5, wherein the inside diameter of the skeleton bore comprises a top inside diameter at the top of the skeleton and a bottom inside diameter at the bottom of the skeleton; and wherein the top inside diameter is greater than the bottom inside diameter.

7. The stripping element as set forth in claim 6, wherein the inside diameter of the skeleton bore further comprises an interim inside diameter longitudinally between the top inside diameter and the bottom inside diameter; and wherein the interim diameter is less than the top inside diameter and greater than the bottom inside diameter.

8. The stripping element as set forth in claim 7, wherein the skeleton bore further comprises a first cylindrical interior surface having the top inside diameter and a second cylindrical interior surface having the bottom inside diameter.

9. The stripping element as set forth in claim 8, wherein the skeleton bore further comprises an angled interior surface longitudinally between the first cylindrical interior surface and the second cylindrical interior surface.

10. The stripping element as set forth in claim 9, wherein the one or more openings comprise a plurality of slots disposed radially through at least a portion of the angled interior surface and at least a portion of the second cylindrical interior surface.

11. The stripping element as set forth in claim 10, wherein the plurality of slots are angled relative to a radial axis that intersects a central longitudinal axis of the skeleton.

12. The stripping element as set forth in claim 1, wherein the stripping body comprises a second upwardly facing surface disposed adjacent to at least a second portion of the bottom surface of the backing plate; wherein the first portion of the bottom surface of the backing plate is radially exterior of the backing ring; and wherein the second portion of the bottom surface of the backing plate is radially interior of the backing ring.

13. The stripping element as set forth in claim 12, wherein the second portion of the bottom surface of the backing plate is disposed at least partially within the backing ring bore.

14. The stripping element as set forth in claim 13, wherein the second portion of the bottom surface of the backing plate is the bottom surface of a locator configured to center the backing ring relative to the backing plate.

15. The stripping element as set forth in claim 14, wherein the locator comprises a lip, a groove, or a combination thereof.

16. The stripping element as set forth in claim 1, wherein the backing ring has a wall thickness that is greater than a wall thickness of the skeleton.

17. The stripping element as set forth in claim 1, wherein the backing ring has a major longitudinal dimension, wherein the skeleton has a major longitudinal dimension, and wherein the major longitudinal dimension of the skeleton is greater than the major longitudinal dimension of the backing ring.

18. The stripping element as set forth in claim 1, wherein the backing ring and the skeleton are integral portions of a unitary structure.

19. The stripping element as set forth in claim 1, wherein at least a portion of the skeleton has a major outside dimension that is less than a major outside dimension of the backing ring.

20. The stripping element as set forth in claim 1, wherein the backing ring comprises a solid, cylindrical wall; wherein the one or more openings comprise a plurality of longitudinally-oriented slots disposed radially through the skeleton; wherein the skeleton has a bottommost surface; and wherein each of the plurality of longitudinally-oriented slots extends through the bottommost surface of the skeleton.