HIGHLY WEAR RESISTANT COMPOSITE ROTARY SEALS WITH WEAR LAYER AT INNER DIAMETER AND/OR OUTER DIAMETER EMBEDDED INSIDE OR BETWEEN RUBBER LAYERS

BACKGROUND

Drill bits are commonly used in, for example, the oil and gas exploration industry for drilling wells in earth formations. One type of drill bit commonly used in the industry is the roller cone drill bit. Roller cone drill bits generally comprise a bit body connected to a drill string or bottom hole assembly (BHA). Roller cone drill bits typically include a plurality of roller cones rotatably attached to the bit body. The roller cones are generally mounted on steel journals integral with the bit body at its lower end. The roller cones further comprise a plurality of cutting elements disposed on each of the plurality of roller cones. The cutting elements may comprise, for example, inserts (formed from, for example, polycrystalline diamond, boron nitride, and the like) and/or milled steel teeth that are coated with appropriate hardfacing materials.

When drilling an earth formation, the roller cone drill bit is rotated in a wellbore, and each roller cone contacts the bottom of the wellbore being drilled and subsequently rotates with respect to the drill bit body. Drilling generally continues until, for example, a bit change is required because of a change in formation type is encountered in the wellbore or because the drill bit is worn and/or damaged. High temperatures, high pressures, tough, abrasive formations, and other factors all contribute to drill bit wear and failure.

When a drill bit wears out or fails as the wellbore is being drilled, it is necessary to remove the BHA from the well so that the drill bit may be replaced. The amount of time required to make a bit replacement trip produces downtime in drilling operations. The amount of downtime may be significant, for example, when tripping in and out of relatively deep wells. Downtime can add to the cost of completing a well and is a particular problem in offshore operations where costs are significantly higher. It is therefore desirable to maximize the service life of a drill bit in order to avoid rig downtime.

One reason for the failure of a roller cone drill bit is the wear that occurs on the journal bearings that support the roller cones. The journal bearings may be friction-type or roller-type bearings, and the journal bearings are subjected to high loads, high pressures, high temperatures, and exposure to abrasive particles originating from the formation being drilled. The journal bearings are typically lubricated with grease adapted to withstand tough drilling environments, and such lubricants are an important element in the life of a drill bit.

Lubricants are retained within the journal bearing surface area by a journal bearing seal, which is typically an O-ring type seal. The seal is typically located in a seal groove formed on an interior surface of a roller cone. The seal generally includes a static seal surface adapted to form a static seal with the interior surface of the roller cone and a dynamic seal surface adapted to form a dynamic seal with the journal upon which the roller cone is rotatably mounted. The seal must endure a range of temperature and pressure conditions during the operation of the drill bit to prevent lubricants from escaping and/or contaminants from entering the journal bearing. Elastomer seals known in the art are conventionally formed from a single type of rubber or elastomeric material, and are generally formed having identically configured dynamic and static seal surfaces with a generally regular cross section, but are also known to be formed of composite materials so that dynamic and/or static sealing surface is formed from a different material from the rest of the seal.

While journal seals formed from such rubber or elastomeric materials display excellent sealing properties of elasticity and conformity to mating surfaces, they display poor tribiological properties, low wear resistance, a high coefficient of friction, and a low degree of high-temperature endurance and stability during operating conditions. Accordingly, the service life of bits equipped with such seals is defined by the limited ability of the elastomeric seal material to withstand the different temperature and pressure conditions at each dynamic and static seal surface.

Example O-ring seals known in the art that have been constructed in an attempt to improve O-ring seal service life include a multiple hardness O-ring comprising a seal body formed from nitrile rubber, and a hardened exterior skin surrounding the body that is formed by surface curing the exterior surface of the nitrile rubber. Although the patent teaches that the O-ring seal constructed in this manner displays improved hardness and abrasion resistance, the act of hardening the entire outside surface of the seal body causes the seal to loose compressibility and other related properties that are important to the seal's performance at the static seal surface.

Another example O-ring seal is a drill bit seal having a dynamic and static seal surface formed from different materials. The dynamic seal surface is formed from a relatively low friction material comprising a temporary coating of Teflon that is deposited onto an inside diameter surface of the seal. The static seal surface is formed from the same material that is used to form the seal body. The Teflon surface acts to improve the wear resistance of the seal at the dynamic seal surface. However, the use of Teflon on the dynamic seal surface only provides a temporary improvement in the coefficient of friction and easily wears away due to its low wear resistance.

A still other example O-ring seal is one comprising a dynamic seal surface, formed from a single type of elastomeric material, and that has a static seal surface that is formed from an elastomeric material different than that used to form the dynamic seal surface. The elastomeric materials used to form the static seal surface is less wear resistant than the elastomeric material used to form the dynamic seal surface, and the elastomeric materials forming the dynamic and static seal surfaces are bonded together by chemically cross-linking to form the seal body. Although such seal construction provides an improved wear resistance at the dynamic seal surface, when compared to single-elastomer seals, the amount of wear resistance that is provided is still limited to the ability of an elastomeric material. In such seal construction, the elastomeric materials used to form the static and dynamic seal surfaces, while being somewhat tailored to provide improved service at each such surface, must still remain chemically compatible with one another to permit the two to be chemically bonded together. Accordingly, while this type of seal construction provides a dynamic seal surface having improved wear resistance, when compared to a single-elastomer seal, the dynamic seal surface will still be the point of failure of the seal.

Accordingly, there exists a continuing need for developments in journal seal constructions that possess improved tribiological properties, improved wear resistance, a reduced coefficient of friction, and/or improved high-temperature endurance and stability when compared to conventional journal seals.

SUMMARY

In one aspect, embodiments disclosed herein relate to a composite journal seal for use in a roller cone drill bit that includes a substantially ring shaped elastomeric body having at least two axial, radial, or canted sealing surfaces, at least one of the at least two axial, radial, or canted sealing surface being a dynamic sealing surface, and at least one reinforcement layer embedded at least 0.005 inches from the at least one dynamic sealing surface.

In another aspect, embodiments disclosed herein relate to a roller cone drill bit that includes a bit body; at least one journal extending from a lower portion of the bit body; a roller cone rotatably mounted on the journal; and an annular seal positioned between the cone and the journal, the annular seal comprising an elastomeric seal body having: a first sealing surface for providing a seal along a dynamic rotary surface formed between the seal body and one of the cone or the journal; a second sealing surface for providing a seal between the seal body and the other of the cone or journal; and a reinforcement layer embedded at least 0.005 inches from first sealing surface or the second sealing surface.

In yet another aspect, embodiments disclosed herein relate to a roller cone drill bit that includes a bit body; at least one journal extending from a lower portion of the bit body; a roller cone rotatably mounted on the journal; and an annular seal positioned between the cone and the journal, the annular seal comprising an elastomeric seal body having: a first sealing surface for providing a seal along a dynamic rotary surface formed between the seal body and one of the cone or the journal; a second sealing surface for providing a seal between the seal body and the other of the cone or journal; and a reinforcement layer embedded within the annular seal along at least 40% of the circumference of the first sealing surface.

Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is perspective view of roller cone drill bit.

FIG. 2 is a partial cross-sectional view of a roller cone drill bit.

FIGS. 3A and 3B show longitudinal and axial cross-sectional views of one embodiment of a composite seal of the present disclosure.

FIGS. 4A and 4B show longitudinal and axial cross-sectional views of one embodiment of a composite seal of the present disclosure.

FIGS. 5A and 5B show longitudinal cross-sectional views of two embodiments of a composite seal of the present disclosure.

FIG. 6 shows a longitudinal cross-sectional view of one embodiment of a composite seal of the present disclosure.

FIGS. 7A and 7B show longitudinal cross-sectional views of two embodiments of a composite seal of the present disclosure.

FIG. 8A shows an axial cross-sectional view of a roller cone assembled on a drill bit journal with a prior seal.

FIG. 8B shows an axial cross-sectional view of a roller cone assembled on a drill bit journal with a composite seal according to the present disclosure.

FIG. 9 shows an axial cross-sectional view of one embodiment of a composite seal of the present disclosure.

FIG. 10 shows a longitudinal cross-sectional view of one embodiment of a composite seal of the present disclosure.

FIG. 11 shows a longitudinal cross-sectional view of one embodiment of a composite seal of the present disclosure.

FIG. 12 shows a longitudinal cross-sectional view of one embodiment of a composite seal of the present disclosure.

FIG. 13 shows a cross-sectional view of a composite seal of the present disclosure.

FIG. 14 shows a cross-sectional view of a composite seal of the present disclosure.

FIG. 15 shows a cross-sectional view of a composite seal of the present disclosure.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to seals used in drilling oil wells and the like. More particularly, embodiments disclosed herein relate to seals used in drill bits that are constructed from composite materials having a wear layer embedded inside or between elastomeric layers along at least a portion of at least one sealing surface.

FIG. 1 shows a drill bit 8 comprising a bit body 9 and three roller cones 11 rotatably attached to the bit body 9. A means for attaching the drill bit 8 to a bottom hole assembly (BHA) (not shown), such as a threaded connection 12, is positioned at an upper end of the bit body 9. A plurality of cutting elements 13 are disposed on the roller cones 11, which may be inserts inserted into holes in the roller cones or milled teeth that are integrally formed with the cone. Nozzles 15 are disposed in the bit body 9 so as to transmit a flow of drilling fluid from an interior of the drill bit 8 to a wellbore (not shown) and to a space proximate the roller cones 11. The flow of drilling fluid serves to cool the drill bit 8 (e.g., to cool the plurality of cutting elements 13) and to transport formation cuttings from the bottom of the wellbore to a wellbore annulus (not shown) and, subsequently, to the surface.

FIG. 2 shows a cross sectional view of one leg 10 of the drill bit 8 shown in FIG. 1. The drill bit 8 further comprises a rotational axis 14 and three legs 10 (one of which is shown in FIG. 2) to which the roller cones 11 are rotatably attached. Each leg 10 includes a journal pin 16 that extends downwardly and radially inwardly. However, it is also within the scope of the present disclosure that the seals of the present disclosure may be used on journals that extend radially outward from the bit centerline, as described in US Patent Pub. No. 2011/0024197, which is assigned to the present assignee and herein incorporated by reference in its entirety. A plurality of radial bearings and axial thrust bearings are disposed between the journal pin 16 and the roller cone 11. The plurality of radial and thrust bearings absorb and transfer loads produced by the roller cones 11 contacting a formation (not shown) and drilling the wellbore. Effectively, loads are transferred from the roller cones 11 to the bit body 9 and, subsequently, to the BHA.

The plurality of radial and thrust bearings include, for example, radial bearing inserts 17, 19. These and other bearing surfaces are lubricated by, for example, high-temperature grease. Grease may be pumped into the interior of the journal pin 16/roller cone 11 interface through, for example, a grease fill passage. Details of the grease fill passage and system, as well as a typical grease system pressure compensation mechanism may be found, for example, in U.S. Pat. No. 6,170,830 assigned to the present assignee and herein incorporated by reference in its entirety. The lubricating grease reduces the friction and, as a result, the operating temperature of the bearings in the drill bit 8. Reduced friction increases drill bit performance and longevity, among other desirable properties. The grease is retained in the load bearing regions of the drill bit 8 by, for example, a seal 20. The seal 20 is typically disposed in a seal groove 22 formed on an internal surface of the roller cone 11. However, the seal groove 22 may alternatively be formed on an external surface of the journal pin 16, and the placement of the seal groove 22 is not intended to be limiting. The seal 20 is typically compressed laterally by a selected amount in the seal groove 22. The compression, which is also referred to as “squeeze,” is produced when the seal 20 is compressed between the surface of the journal pin 16 and an inner surface 21 of the seal groove 22. The selected amount of compression may be varied, for example, by controlling either a radial thickness of the seal 22 of by controlling the depth of the seal groove 22.

The seal 20 is adapted to retain lubricating grease proximate the bearings surfaces of the drill bit 8 and to serve as a barrier to prevent, for example, drilling fluid, hydrocarbons, and/or drilling debris from impinging upon the interior of the journal pin 16/roller cone 11 interface and thereby damaging the radial and thrust bearings. Because of the variety of chemicals, hydrocarbons, and operating conditions experienced when drilling the wellbore, the seal 20 is geometrically designed and formed from selected materials to provide an effective barrier between the bearings surfaces and the wellbore environment.

Referring now to FIGS. 3A and 3B, a seal 30 according to the present disclosure is shown. Seal 30 includes a seal body 32 that is formed in the shape of a substantially flat ring and has seal surfaces on the internal and external diameters 34, 36 thereof. At the ID surface 34, a reinforcement layer 38 is embedded within seal 30 at least a selected distance from the ID surface. Reinforcement layer 38 may be provided to help improve the wear resistance of inner sealing surface 34 as a dynamic sealing surface. While some prior bits may have included a reinforcement layer bonded on the sealing surface, instead of embedded within the seal a selected distance from the sealing surface, to improve the wear resistance of the seals, these layers may be included with some drawbacks, such as difficulty to control fabric alignment, the roughness of the fabric layer can be abrasive to the surface with which the seal interfaces and may also lead to grease leakage, and/or fabric fraying after use. In contrast, the present reinforcement layer may provide the same reinforcing or wear resistance effect to the seal, while simultaneously improving the sealing of the surface without risk of abrasion or fraying and manufacturability.

Referring now to FIGS. 4A and 4B, a reinforcement layer 48 may be embedded in the seal or seal body a selected distance from both the sealing surface at the inner diameter 44 and the sealing surface at the outer diameter 46, which may be particularly desirable for a dual dynamic seal 40.

While the seals of FIGS. 3A-B and 4A-B, are shown as being composite seals formed from two materials, the materials forming the seal body 32, 42 and reinforcement layers 38, 48, the present disclosure is not so limited. For example, as shown in FIG. 5A, the composite seal 50 may include a composite wear layer 55 (forming either the ID or OD) at a sealing surface adjacent a rubber energizer seal body 52. In the embodiment shown in FIG. 5A, seal 50 includes a composite wear layer 55 at the inner sealing surface 54, and (non-composite) wear layer 57 at the outer sealing surface 56. Composite wear layer 55 is formed from elastomeric material 55a and a reinforcement layer 58, whereas wear layer 57 is only formed from elastomeric material 57a. Reinforcement layer 58 is embedded a selected distance from the sealing surface 54 within the elastomeric material 55a. In the embodiment shown in FIG. 5A, elastomeric material 55a is distinct from energizer seal body 52 but is the same material as elastomeric material 57a. However, in other embodiments, elastomeric materials 55a and 57a may be distinct materials. Further, as shown in FIG. 5B, composite seal 50 may include two composite wear layers 55 forming both the ID sealing surface 54 and OD sealing surface 56. Further, while the composite wear layers 55 and 57 are shown as including an elastomeric material 55a on both in the inner and outer sides of reinforcement material, it is within the scope of the present disclosure, for example, that the composite wear layer may only be present on the exterior extent of the reinforcement layer, i.e., there is no elastomeric material 55a between reinforcement layer 58 and seal energizer seal body 52. Further, while the reinforcement layer 38, 48 in FIGS. 3 and 4 has a substantially uniform thickness, the embodiments shown in FIGS. 5A and 5B possess a non-uniform thickness, being radially thicker at an axial cross-sectional plane than regions axially above and below. It is also envisioned that a reinforcement layer with a substantially uniform thickness may be used in a composite wear layer, and a non-uniform thickness may be used in a seal without a composite wear layer. Similarly, it is also envisioned that in seals without a composite wear layer, the reinforcement layer may also have a substantially uniform thickness or a non-uniform thickness.

As mentioned in the description of all of the above figures, the reinforcement material layer is embedded within the seal, i.e., set back from the sealing surface a selected distance. As shown in FIG. 6, an exemplary composite seal of the present disclosure may have various dimensions and/or relative dimensions involving the reinforcement layer 68 and/or composite wear layer 65a. For example, in various embodiments, T_ymay be more than about 0.005 inches, and ranging from about 0.010 to 0.050 inches in a particular embodiment, and at least about 0.020 inches in yet another particular embodiment. Further, T_xmay be at least 0.01 inches in one embodiment, ranging from 0.010 inches to 0.14 inches in another embodiment, and ranging from 0.015 to 0.08 inches in yet another embodiment. For embodiments incorporating a composite wear layer 65, the composite wear layer 65 extends a thickness T_ithat is at least 0.03 inches, at least 0.06 inches in another embodiment, ranging from 0.075 to 0.280 inches in another embodiment, and ranging from about 0.1 to 0.2 inches in yet another embodiment. The ratio of T_ito T_o(the total thickness of the seal) may be at least 10 percent in one embodiment, at least 20 percent in another embodiment, up to 40 percent in another embodiment, up to 50 percent in yet another embodiment, and ranging from 30 to 50 percent in yet another embodiment. Further, it is also noted that the values of T_x, T_y, and T_imay be non-uniform along the circumference direction of a seal and/or having overlapping thicknesses depending on the arrangement of the layers.

The inventors of the present disclosure have found that by embedding the reinforcement layer under the sealing surface(s), instead of the layer forming or being exposed as the sealing, the sealing performance of sealing surface may be significantly increased. The roughness and rigidity of the reinforcement layer forming the sealing surface(s) may lead to leakage of grease. The inventors also found that by adding reinforcement layer under the sealing surface(s), the amount of deformation in the seal at the dynamic sealing surface may be reduced as compared to a conventional rubber seal. For example, referring to FIGS. 7A and 7B, 7A shows a prior art seal 20 in a seal groove (not shown) in a roller cone 11 having sealing surfaces at its inner diameter 4 and outer diameter 6. In this embodiment, sealing surface at the inner diameter 4 is a dynamic sealing surface as there is continual rotational motion between the seal 20 and the journal 16 on which the cone 11 is disposed. As the roller cone 16 rotates, the inventors have found that no reinforcement layer is included, there is an amount of deformation in the seal surface, represented by the shift between A and A′. In contrast, a seal according to the present disclosure, shown in FIG. 7B may have less shift between A and A′, i.e., seal deformation, for a seal 70 present between journal 16 and roller cone 11 rotating around journal 16 and having a reinforcement layer 78 embedded within the seal 70 adjacent the inner sealing surface 74 and/or outer sealing surface 76. Less deformation in the seal may also result in better sealing properties.

Referring now to FIGS. 8A and 8B, the composite seals 80 in these embodiments include a substantially uniform reinforcement layer 88 in composite wear layers 85; however, unlike the reinforcement layers 38, 48 shown in FIGS. 3 and 4, the reinforcement layers 88 in FIGS. 8A and 8B are embedded a selected distance or thickness from inner and outer sealing surface 84, 86, the layers 88 extend in the axial direction to the upper and lower surfaces 81, 83 and are exposed at such surfaces. Further, Applicants also note that the present disclosure does not exclude a composite seal that has some amount of exposure of the reinforcement layer at a sealing surface. Rather, in accordance with embodiments of the present disclosure, the reinforcement layer may be embedded under a sealing surface for at least 40% of the radial circumference of the seal surface.

For example, referring now to FIG. 9, a composite seal 90 includes reinforcement layers 98 embedded under the inner and outer sealing surfaces 94, 96 along a portion of the circumference of the two surfaces. In one embodiment, this portion may comprise at least 40% of the radial circumference, at least 50% of the radial circumference in another embodiment, and at least 60% in yet another embodiment. It is within the scope of the present disclosure that the circumferential portion of the seal that does not have a reinforcement layer embedded the selected distance (described above) under the sealing surface may have no material along such circumferential portion, or may have the reinforcement layer at a greater or less distance than described above or exposed at the surface along such circumferential portion. Further, while the embodiment shown in FIG. 9 shows two reinforcement layers 98 having substantially the same circumferential coverage of the inner and outer sealing surfaces 94, 96, it is within the scope of the present disclosure that either of such layers may be excluded, that either of such layers may have lesser or greater or full coverage, that the coverage may include differing circumferential portions of the sealing surfaces, and/or that an overlapping of the layers may exist.

Further, while the previous embodiments illustrate the reinforcement layer covering substantially the entire axial extent of the sealing surface, the present invention is not so limited. For example, as shown in FIG. 10, a composite seal 1000 may include a reinforcement layer 1008 that does not cover the entire axial extent of the sealing surfaces 1004, 1006. In this embodiment, a reinforcement material is also embedded along at least a portion of the upper and/or lower surfaces (non-sealing or containment surfaces) 1001, 1003. While the embodiment in FIG. 10 illustrates a partial coverage, it is noted that if full circumferential and/or axial coverage is desired, the reinforcement layer 1008 may take the general form of a torus reinforcement layer 1108, embedded under the sealing surfaces and containment surfaces, as illustrated in FIG. 11. Further, depending on the particular coverage desired, it may be necessary (or desirable from a manufacturing perspective) to have some overlap of the reinforcement layer 1208 within the seal 1200, as illustrated in FIG. 12. This overlap may be along a containment or non-sealing surface (as shown in FIG. 12) or sealing surface. Alternatively, there may be substantially full overlap in the form of a plurality of reinforcement layers 1208 embedded adjacent a sealing surface. For example, in the case of a fabric reinforcement layer, multiple pieces of fabric may be used atop each other to form a plurality of reinforcement layers or one piece of fabric may be folded to create such multiple layers. In the case of fabric or other types of reinforcement layers, it is within the scope of the present disclosure that some amount of elastomeric material may separate the multiple layers.

Further, while the above described embodiments generally described composite seals 1300 as having sealing surfaces that are radial sealing surfaces 1304, 1306, such as shown in FIG. 13, under which reinforcement layer(s) 1308 are embedded, it is also within the scope of the present disclosure that a composite seal 1400 may have axial sealing surfaces 1401 and 1403, under which reinforcement layer(s) 1408 may be embedded. Alternatively, the composite seal of the present disclosure may be a canted (or angled) seal 1500, as shown in FIG. 15, having a canted sealing surface 1515, positioned intermediate axial surface 1501 and radial surface 1506, under which a reinforcement layer 1508 may be embedded. While the embodiment shown in FIG. 15 includes a canted sealing surface 1515 positioned intermediate upper axial and outer radial directions, other canted seals may include a sealing surface under which the reinforcement layer is embedded intermediate either of the upper or lower axial directions and either of the inner or outer radial directions.

Additionally, it is also noted that any of the embodiments illustrated may include a composite wear layer having both a distinct elastomeric material from the remaining seal body and reinforcement layer or the seal may only include the reinforcement layer without multiple elastomeric materials.

Journal seals conventionally employed in roller cone bits are shaped in the form of an O-ring and are formed from elastomeric or rubber materials, such as acrylonitrile polymers including acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile-butadiene rubber (HNBR), carboxylated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, ethylene propylene, ethylene propylene diene, fluoroelastomers including those available under the trade names Viton and Kalrez manufactured by DuPont, tetrafluoroethylene-propylene copolymers (FEPM) available under the trade name AFLAS® from Asahi Glass Co.), fluorocarbon (FKM) and perfluoroelastomer (FFKM), and the like. Other components sometimes used in the polymers include activators or accelerators for the curing, such as stearic acid, and agents that improve the heat resistance of the polymer, such as zinc oxide and curing agents, or additives that affect the material properties of the cured polymer, such as carbon nanotubes, carbon fibers, nano-sized polytetrafluoroethylene (PTFE), or silica- or silicate-containing materials such as mica or diatomaceous earth.

The reinforcement layer(s) used in the present disclosure may include harder elastomeric materials relative to the rubber matrix, non elastomeric materials including plastic, fabric, and any other materials, including composite materials, that have a hardness higher compared to the seal matrix material and can be bonded to the rubber matrix. One example nonelastomeric component is in the form of fibers such as those selected from the group consisting of polyester fiber, cotton fiber, stainless steel fibers aromatic polyamines (Aramids) such as those available under the Kevlar family of compounds, polybenzimidazole (PBI) fiber, poly m-phenylene isophthalamide fiber such as those available under the Nomex family of compounds, and mixtures or blends thereof such as PBI/Kevlar/stainless steel staple fabric. The fibers can either be used in their independent state and/or combined with an elastomeric composite component, or may be combined into threads or woven into fabrics with or without an elastomeric composite component.

Other composite materials suitable for use in forming composite seals include those that display properties of high-temperature stability and endurance, wear resistance, and have a coefficient of friction similar to that of the polymeric material specifically mentioned above. If desired, glass fiber can be used to strengthen the polymeric fiber, in such case constituting the core for the polymeric fiber. An exemplary nonelastomeric polymeric material used for making the composite construction is a polyester-cotton fabric having a density of approximately eight ounces per square yard. The polymeric material is provided in the form of a fabric sheet having a desired mesh size.

In the embodiments where the composite seals of the present disclosure include a reinforcement material and a single elastomeric material, the reinforcement layer may be a fabric layer(s) or may have a durometer-hardness Shore A of at least 5 units greater than the elastomeric material, at least 10 greater in other embodiments, and at least 20 greater in yet other embodiments.

In embodiments where the composite seal includes a composite wear layer, the seal may have a multi-piece construction comprising an elastomeric energizing seal body and the composite wear layer having a elastomeric portion that is formed from a different material than the seal body and that is selected to provide improved properties at a desired seal location, e.g., to provide improved properties of wear resistance along a sealing surface of the seal. The seal body and remaining seal portion are assembled together to form the multi-piece seal and do not require chemical cross-linked bonding, but may include such crosslinked bonding if desired. It is understood, however, that multi-piece seals of this invention can be assembled together by adhesive, i.e., by means that does not create chemical cross-linked bonding between the seal body and remaining sealing portion.

In such a particular embodiment, the seal body, for example, may be formed from an elastomer or rubber material that is capable of providing an energizing function to urge the dynamic seal surface against a dynamic roller cone bit surface. Suitable elastomer and rubber materials include those mentioned above and others such as those selected from the group of fluoroelastomers including those available under the trade names Viton and Kalrez manufactured by DuPont, carboxylated elastomers such as carboxylated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR) and the like. Suitable elastomeric materials have a modulus of elasticity at 100 percent elongation of from about 500 to 2,000 psi (3 to 12 megapascals), a minimum tensile strength of from about 2,000 to 7,000 psi (6 to 42 megapascals), elongation of from 100 to 500 percent, die C tear strength of at least 200 lb/in. (1.8 kilogram/millimeter), durometer hardness Shore A in the range of from about 60 to 95, and a compression set after 70 hours at 100° C. of less than about 18 percent, and preferably less than about 16 percent. Particular elastomeric materials useful in the present disclosure include proprietary NBR compounds manufactured by Smith Bits and Smith Services, A Schlumberger Company, under the product names HSN-8A, W-122, W-77, 401, and E-77. In a particular embodiment, where high temperature applications are intended, the seal body and/or composite layer may include one of FKM, FEPM, and FFKM.

The elastomeric material forming the composite wear layer may include a different elastomer than selected for the seal body, or may include additives selected to alter the material properties of the elastomeric body. For example, the elastomeric material of the wear layer may have a durometer hardness Shore A of at least 5 or at least 10 units greater than the elastomeric material of the seal body. Further, a reinforcement material may have a durometer hardness Shore A of at least 5 or at least 10 units greater than the elastomeric material of the wear layer in which it is embedded.

The seal construction may include one or more lubricant additives, disbursed uniformly through the elastomeric material, to further reduce wear and friction along the surface of the seal. Suitable lubricant additives include those selected from the group consisting of polytetrafluoroethylene (PTFE), hexagonal boron nitride (hBN), flake graphite, molybdenum disulfide (MoS₂) and other commonly known fluoropolymeric, dry or polymeric lubricants, and mixtures thereof. The lubricant additive may be used to provide an added degree of low friction and wear resistance to the elastomeric component of the composite material that is placed in contact with a rotating surface. A particular lubricant additive is hBN manufactured by Advanced ceramics identified as Grade HCP, having an average particle size in the range of from about five to ten micrometers. Multi-piece seals constructed according to principles of this disclosure may comprise up to about 20 percent by volume lubricant additive.

The composite seals of the present disclosure may be formed from a multi-piece construction. Specifically, a seal body portion may be extruded as one piece, onto which a reinforcement layer may be placed at the appropriate surface (depending on the type of sealing surface to be reinforced). A separate piece or separate pieces of elastomer may be extruded and placed atop the reinforcement layer. Alternatively, multiple coats of uncured liquid elastomeric material in a suitable solvent may be applied to the reinforcement layer to form an elastomeric coating thickness so that the reinforcement material is sufficiently embedded within the seal from the sealing surface. Further, in the case of multiple layers of reinforcement layer being used, particularly in the case of a fabric sheet being used, coatings of elastomeric material dissolved in a solvent may be applied onto the fabric to saturate the fabric and also build up an amount of elastomeric material between multiple sheets of fabric. All components are placed in a mold, the mold is heated and pressurized to simultaneously form the seal and cure or vulcanize (and optionally crosslink) the elastomer component(s) of the composite seal.

Embodiments of the present disclosure may provide at least one of the following advantages. The presence of reinforcement layer(s) may result in enhanced wear resistance of the sealing surfaces, and do so in a manner that results in better sealing characteristics. Further, the embedding of the reinforcement layer and multi-piece construction of the composite seal may result in easier manufacturing particularly because the sealing surface remains a uniform elastomeric material and with more consistent performance by reducing the amount of deformation in the seal surface and the potential breakdown of the reinforcement layer, which can result in failure of the seal, the bit body surfaces and cause bit failure.

Even further, the composite seals of the present disclosure may be particularly suitable for high temperature applications. Specifically, when drilling into oil, gas, and geothermal reservoirs, high temperatures often experienced in deep and/or geologically active areas with hard lithologies (necessitating use of roller cone drill bits) place high demands on the seal (and thus bit) performance, specifically resistance to thermal degradation to avoid bearing failure. Various embodiments of the composite seals of the present disclosure may be particularly suitable for such high temperature applications.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

HIGHLY WEAR RESISTANT COMPOSITE ROTARY SEALS WITH WEAR LAYER AT INNER DIAMETER AND/OR OUTER DIAMETER EMBEDDED INSIDE OR BETWEEN RUBBER LAYERS

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