Downhole friction reduction system with flexible agitator

Abstract

An agitator deployable in a wellbore, comprising: a housing comprising a central axis and a central passage; a valve including a first valve body and a second valve body permitted to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface, the second contact surface configured to contact the first contact surface; a first valve adapter, the first valve adapter including a first housing seat, the first housing seat receiving at least a portion of the first valve body to couple the first valve adapter to the first valve body; and a flexible valve configured to allow the first valve body to flex relative to the first valve adapter, whereby an angular misalignment may be formed between a central axis of the first valve body and a central axis of the first valve adapter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. non-provisional patent application No. 17 / 837,780, filed on June 10, 2022, entitled “Downhole Friction Reduction Systems Having a Flexible Agitator,” the entire contents of which are incorporated herein by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] not applicable. Background Art

[0003] When drilling a wellbore into an earthen formation, for example, to extract hydrocarbons or minerals from a subterranean formation, a drill bit is typically connected to the lower end of a drill string formed by a plurality of pipe joints connected together end to end, and the drill string is then rotated so that the drill bit is advanced downwardly into the ground to form a wellbore along a predetermined trajectory. In some applications, a drilling fluid or "mud" is pumped down the drill string under pressure, out of the face of the drill bit into the wellbore, and then pumped upward to the surface along an annulus between the drill string and the sidewall of the wellbore. The drilling fluid may be water-based or oil-based and is typically viscous to enhance its ability to carry wellbore cuttings to the surface. In addition, the drill string may be connected to a bottom hole assembly (BHA) that includes a downhole mud motor configured to rotate the drill bit in response to the pumping of the pressurized drilling fluid.

[0004] In some cases, the drill string may not rotate from the surface when the rotation of the drill bit is driven by a mud motor, but rather the drill string may slide through the wellbore as the drill bit cuts into the formation. The drill string may form a so-called "mud cake" along the sidewalls of the wellbore, which provides a physical barrier between the wellbore and the soil formation to reduce fluid loss to the soil formation. In addition, as the drill string slides through the wellbore, portions of the drill string may occasionally "stick" to the sidewalls of the wellbore, thereby undesirably increasing the amount of friction between the drill string and the wellbore, which may limit the "reach" or length of the wellbore. In some applications, the drill string is provided with one or more friction reduction tools designed to reduce friction between the drill string and the wellbore. The friction reduction tool may be configured to produce an oscillatory motion in the drill string in response to periodically obstructing or blocking the flow of drilling fluid to the BHA. Summary of the invention

[0005] An embodiment of an agitator deployable in a wellbore includes: a housing including a central axis and a central passage; a valve disposed in the housing and including a first valve body and a second valve body allowed to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface, the second contact surface being configured to contact the first contact surface; a first valve adapter coupled to the housing and including a first receptacle receiving at least a portion of the first valve body to couple the first valve adapter to the first valve body; and a flexible valve seat located between the first valve body and the first valve adapter in a first receptacle of the first valve adapter, and wherein the flexible valve seat is configured to allow the first valve body to flex relative to the first valve adapter, thereby enabling an angular misalignment to be formed between the central axis of the first valve body and the central axis of the first valve adapter. In some embodiments, the flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter to be between 0.01° and 5.00°. In some embodiments, the flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter of between 2.00° and 4.00°. In some embodiments, a stator is positioned in the housing, and a rotor is rotatably positioned in the stator and connected to one of the first valve body and the second valve body. In some embodiments, the flexible valve seat includes a mechanical biasing member configured to apply a biasing force to the first valve body. In some embodiments, the flexible valve seat is formed of an elastomeric material. In some embodiments, the flexible valve seat is formed of a material having a durometer rating between 40 and 120 on the Shore A hardness scale. In some embodiments, the flexible valve seat seals a connection formed between the first valve body and the first valve adapter. In some embodiments, the flexible valve seat includes a body and a spacer ring embedded in the body, wherein the body is formed of a first material having a first hardness, and the spacer ring is formed of a second material having a second hardness, the second hardness being greater than the first hardness.

[0006] An embodiment of an agitator deployable in a wellbore includes: a housing including a central axis and a central passage; a valve disposed in the housing and including a first valve body and a second valve body allowed to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface, the second contact surface being configured to contact the first contact surface; a first valve adapter coupled to the housing and including a first receptacle receiving at least a portion of the first valve body to couple the first valve adapter to the first valve body; and a flexible valve seat positioned in the first receptacle of the first valve adapter and between the first valve body and the first valve adapter, and wherein the flexible valve seat is formed of a material having a durometer rating between 40 and 120 on the Shore A hardness scale. In some embodiments, the material forming the flexible valve seat has a durometer rating between 70 and 90 on the Shore A hardness scale. In some embodiments, the agitator includes: a stator, the stator being positioned in the housing; and a rotor, the rotor being rotatably positioned in the stator and connected to one of the first valve body and the second valve body. In some embodiments, the flexible valve seat is configured to allow the first valve body to flex relative to the first valve adapter, thereby enabling an angular misalignment to be formed between a central axis of the first valve body and a central axis of the first valve adapter. In some embodiments, the flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter to be between 0.01° and 5.00°. In some embodiments, the flexible valve seat seals a connection formed between the first valve body and the first valve adapter.

[0007] An embodiment of an agitator that can be deployed in a wellbore includes: a housing, the housing including a central axis and a central passage; a valve, the valve is disposed in the housing and includes a first valve body and a second valve body that is allowed to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface, the second contact surface being configured to contact the first contact surface; a first valve adapter, the first valve adapter is coupled to the housing, and the first valve adapter includes a first receptacle, the first receptacle receives at least a portion of the first valve body to couple the first valve adapter to the first valve body; and a flexible valve seat, the flexible valve seat is positioned in the first receptacle of the first valve adapter, and the flexible valve seat seals a connection formed between the first valve body and the first valve adapter. In some embodiments, the flexible valve seat adheres to both the first valve body and the first valve adapter. In some embodiments, the agitator includes: a stator, the stator is positioned in the housing; and a rotor, the rotor is rotatably positioned in the stator and connected to one of the first valve body and the second valve body. In some embodiments, the flexible valve seat is configured to allow the first valve body to flex relative to the first valve adapter, thereby potentially forming an angular misalignment between a central axis of the first valve body and a central axis of the first valve adapter. In some embodiments, the flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter to be between 0.01° and 5.00°. In some embodiments, the agitator includes: a second valve adapter, the second valve adapter is coupled to the housing, and the second valve adapter includes a second receptacle, the second receptacle receives at least a portion of the second valve body to couple the second valve adapter to the second valve body; wherein the flexible valve seat includes a first flexible valve seat, and the agitator also includes a second flexible valve seat, the second flexible valve seat is positioned in the second receptacle of the second valve adapter, and the second flexible valve seat seals a connection formed between the second valve body and the second valve adapter. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The disclosed embodiments will now be described in detail with reference to the accompanying drawings, in which:

[0009] Figure 1 is a schematic diagram of a drilling system including an agitator according to some embodiments;

[0010] Figure 2 yes Figure 1 A side view of a stirrer;

[0011] Figure 3Ayes Figure 1 A side cross-sectional view of an uphole section of an agitator;

[0012] Figure 3B yes Figure 1 A side cross-sectional view of a downhole section of a mixer;

[0013] Figure 4 According to some embodiments Figure 1 A perspective partial cross-sectional view of a power joint of an agitator;

[0014] Figure 5 yes Figure 4 An end cross-sectional view of a power joint;

[0015] Figure 6 yes Figure 1 An enlarged side cross-sectional view of an embodiment of a rotary valve of an agitator;

[0016] Figure 7 yes Figure 6 A perspective view of an embodiment of a first valve body of a rotary valve;

[0017] Figure 8 yes Figure 6 A perspective view of an embodiment of a second valve body of a rotary valve;

[0018] Fig.10 is in a closed configuration Figure 6 A schematic end view of a rotary valve;

[0019] Fig.11 yes Figure 6 Another side cross-sectional view of the rotary valve; and

[0020] Figure 12 to Figure 14 is a side cross-sectional view of another embodiment of a rotary valve. DETAILED DESCRIPTION

[0021] The following discussion refers to various embodiments. However, those skilled in the art will appreciate that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant merely as an example of that embodiment and is not intended to imply that the scope of the disclosure, including the claims, is limited to that embodiment. The drawings are not necessarily drawn to scale. Certain features and components herein may be exaggerated in scale or shown in some schematic form, and some details of conventional elements may not be shown for clarity and brevity.

[0022] In the following discussion and in the claims, the terms "include" and "comprising" are used in an open-ended manner and should be interpreted to mean "including but not limited to". In addition, the term "coupled" means to connect directly or indirectly. Thus, if a first device is coupled to a second device, the connection may be by direct connection or by indirect connection such as through other devices, components and connections. In addition, as used herein, the terms "axial" and "axially" generally mean along or parallel to a central axis (e.g., the central axis of a body or port), while the terms "radial" and "radially" generally mean perpendicular to the central axis. For example, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance refers to a distance measured perpendicular to the central axis. Any reference to above or below in the specification and claims is for clarity, where "above", "upper", "upward", "uphole" or "upstream" means toward the surface of the wellbore, and "below", "lower", "downward", "downhole" or "downstream" means toward the end of the wellbore, regardless of the wellbore orientation.

[0023] As previously mentioned, friction reduction tools are sometimes used to reduce the friction between the drill string and the sidewall of the wellbore. In particular, the friction reduction tool can induce an oscillating motion in the drill string in an attempt to break static friction and prevent the drill string from adhering to the sidewall of the wellbore. Conventional friction reduction tools may include an agitator and an oscillator or impact tool located upstream of the agitator (e.g., between the agitator and the upper end of the drill string at the surface). The agitator may include a valve that periodically and suddenly blocks or blocks the flow of drilling fluid through the agitator, thereby generating a pressure pulse in the drilling fluid traveling upstream to the impact tool. The impact tool may include a spring-loaded mandrel that can extend in response to the application of a pressure pulse to the mandrel, and the mandrel can also retract in response to a biasing force applied to the mandrel by a biasing member of the impact tool after the pressure pulse has dissipated. Thus, the impact tool can periodically extend and retract axially in response to the periodic application of pressure pulses in the drilling fluid caused by the agitator located downstream of the impact tool. The axial oscillatory motion induced in the percussion tool may be transferred to a drill string coupled to the percussion tool to prevent the drill string from sticking to the sidewall of the wellbore.

[0024] The downhole agitator may include a pair of valve plates or valve bodies that form a metal-to-metal seal therebetween to periodically open and close a flow passage formed in the pair of valve bodies as the pair of valve bodies rotate relative to each other. In this manner, the pair of valve bodies may continuously actuate the agitator between an open configuration and a closed configuration as the pair of valve bodies continue to rotate relative to each other. For example, a first valve body of the pair of valve bodies may be connected to a rotor in a rotor and stator arrangement and may therefore rotate relative to a second valve body of the pair of valve bodies in response to drilling fluid flowing through the agitator.

[0025] Typically, the first valve body or rotating valve body is angularly misaligned relative to the second valve body or fixed valve body, resulting in only a small portion of the contact surface or sealing surface of the rotating valve body contacting the corresponding contact surface or sealing surface of the fixed valve body. In other words, when the rotating valve body slidingly engages the fixed valve body, the central axis of the rotating valve body can be at a non-zero angle relative to the central axis of the fixed valve body.

[0026] Considering manufacturing tolerances and other practicalities, it may be extremely difficult to produce a blender in which a pair of valve bodies remain substantially angularly aligned during operation of the blender. For example, typically, a stator bushing in a rotor and stator arrangement has an offset from a centerline that varies along the length of the stator bushing. Considering that the stator bushing orients and positions the rotor relative to a stator housing in which the stator bushing is positioned, the offset in the stator bushing produces an angular misalignment between the central axis of the rotating valve body and the central axis of the stator housing and the central axis of the fixed valve body, wherein the fixed valve body is typically connected to and aligned with the stator housing. The angular misalignment produced between the pair of valve bodies results in significantly elevated point loads, and a relatively fragile pair of valve bodies are susceptible to breaking when subjected to such point loads. Therefore, the elevated point loads applied to the pair of valve bodies due to the angular misalignment between the pair of valve bodies may potentially damage or otherwise minimize the working life of the pair of valve bodies.

[0027] Thus, embodiments of an agitator and friction reduction system are described herein that include a pair of valve plates or valve bodies, wherein at least one of the pair of valve plates or valve bodies is coupled to a flexible valve seat to allow the valve body to flex relative to a housing (e.g., a stator housing) of the agitator. The flexible valve seat may include a flexible material, such as an elastomeric material having a relatively low durometer rating. Alternatively, the flexible valve seat may be made of a relatively more rigid material, but configured as a mechanical biasing element, such as a wave spring, a bow spring, a flexible gasket, or the like. The flexible valve seat may be rotationally locked with a valve adapter by an adhesive or a mechanical interlock (such as a tongue-and-groove arrangement). In addition, the corresponding outer surfaces of the flexible valve seat and the valve body to which it is coupled may be tapered to help connect the valve body to the flexible valve seat.

[0028] As an example, a fixed valve body can be connected to a stator housing via a fixed valve adapter and a corresponding flexible valve seat, the flexible valve seat being configured to allow the fixed valve adapter to flex, thereby forming an angular misalignment with the fixed valve adapter. In this way, the fixed valve body can flex in response to contact between the rotating valve body and the fixed valve body, whereby the fixed valve body can maintain a basic angular alignment between the central axes of the rotating valve body and the fixed valve body. By allowing at least one of the pair of valve bodies to flex relative to its corresponding valve adapter, point loads applied to the pair of valve bodies can be minimized because the central axes of the pair of valve bodies remain substantially parallel during operation of the agitator. In this way, the flexible valve seat can reduce the extent of wear and breakage-related damage caused by the pair of valve bodies and maximize the working life of the pair of valve bodies.

[0029] refer to Figure 1 , an embodiment of a well or drilling system 10 for drilling or producing hydrocarbons from a well or wellbore is shown. In the exemplary embodiment, the drilling system 10 generally includes a vertical support structure or derrick 12 supported by a drilling platform 14. The platform 14 includes a drilling deck or drill floor 16 that supports a rotary table 18 that is selectively rotated by a prime mover (not shown) (such as an electric motor) controlled by a motor controller. The derrick 12 includes a traveling block 20 controlled by a winch 22 for raising and lowering a drill string 24 suspended from the traveling block 20. The drill string 24 of the drilling system 10 extends downwardly through the rotary table 18, a blowout preventer (BOP) stack 26, and into a wellbore 3 that extends from the surface 7 along a central or longitudinal axis 15 into a subsurface formation 5. The drill string 24 is formed of a plurality of drill pipe joints 28 connected end to end. In the exemplary embodiment, a bottom hole assembly (BHA) 30 is attached to the lowermost tubular joint 28, and a drill bit 32 is attached to the downhole end of BHA 30. In other embodiments, drilling system 10 may include an offshore drilling system including a drill string extending through a marine riser and into a subsea wellbore.

[0030] In this embodiment, the drill bit 32 is rotated with the rotary table 18 via the drill string 24 and the BHA 30. By rotating the drill bit 32 with the applied weight on bit (WOB), the drill bit 32 breaks down the underground formation to drill the wellbore 3. In some embodiments, a top drive may be used to rotate the drill string 24 instead of rotating it by the rotary table 18. In some applications, as an alternative or in addition to rotating the drill string 24 from the surface 7, a downhole motor (mud motor) 35 is provided in the drill string 24 to rotate the drill bit 32. In particular, when the drilling fluid passes through the mud motor 35 under pressure, the mud motor 35 can rotate the drill bit 32. In this exemplary embodiment, a casing string 34 is installed and generally extends downward from the surface 7 into at least a portion of the wellbore 3. In some embodiments, the casing string 34 is cemented within the wellbore 3 to isolate various vertically separated soil zones and prevent fluid transfer between these zones. The BOP stack 26 is fixed to the uphole end of the casing string 34. The casing string 34 may include a plurality of tubular members, such as a plurality of threaded pipes connected end-to-end to form a fluid-tight or gas-tight connection to prevent fluid and pressure exchange between the wellbore 3 and the surrounding earthen region.

[0031] An annular space or annulus 36 is formed between the sidewall 9 of the wellbore 3 and the drill string 24 and between the inner surface of the casing string 34 and the drill string 24. In other words, the annulus 36 extends through the wellbore 3 and the casing string 34. The BOP stack 26 includes an annular space or flow path in fluid communication with the annulus 36. An operator of the drilling system 10 or a drilling control system can selectively and controllably open and close one or more BOPs of the BOP stack 26 to allow, restrict or inhibit the flow of drilling fluid or another fluid through the annulus 36. In the exemplary embodiment, the drilling system 10 includes a drilling fluid circulation system to circulate drilling fluid or mud 40 down the drill string 24 and back along the annulus 36. The drilling fluid 40 is generally used to cool the drill bit 32, remove cuttings from the bottom of the wellbore 3, and maintain a desired pressure or pressure profile in the wellbore 3 during drilling operations. The drilling system also includes a drilling fluid reservoir or mud tank 42 , a supply pump 44 , a supply line 46 connected to an outlet of the supply pump 44 , and a kelly 48 for supplying the drilling fluid 40 to the drill string 24 .

[0032] In the exemplary embodiment, the drill string 24 together with the drill pipe joint 28 includes a friction reduction system 50 including a flexible agitator 100 and configured to reduce friction between the drill string 24 and the sidewall 9 of the wellbore 3 while preventing or at least minimizing damage to the sidewall or mud cake of the wellbore 3. Figure 11 and 2. Only a single friction reduction system 50 is shown in the embodiment of the present invention, but in other embodiments, the drilling system 10 may include multiple friction reduction systems 50 spaced apart along the drill string 24. In addition, while in the exemplary embodiment, the agitator 100 includes components of the friction reduction system 50, in other embodiments, the agitator 100 may not include components of the system 50, but may be associated with other equipment of the drilling system 10. In the exemplary embodiment, the drilling system 10 may be operated whereby drilling fluid 40 is pumped through the drill string 24 and to the mud motor 35 to rotate the drill bit 32. When the mud motor 35 is operated to rotate the drill bit 32, the drill string 24 may not be rotated by the rotary table 18 at the surface, but may slide axially through the wellbore 3. The drilling fluid may be pumped through the friction reduction system 50 under the drilling fluid pressure to induce an axial oscillating motion in the drill string 24, thereby breaking up the static friction between the drill string 24 and the sidewall 9 of the wellbore 3.

[0033] Reference now Figure 2 , Figure 3A and Figure 3B , shows an embodiment of a mixer 100. In the exemplary embodiment, the mixer 100 has a central or longitudinal axis 105 and generally includes a first or top joint 102, a second or bottom joint 120 opposite the top joint 102, a power joint or section 140, and a rotary valve 200. Although in Figure 2 , Figure 3A and Figure 3B Although not shown, the agitator 100 may be combined with an impact joint to form Figure 1 Friction reduction system 50 is shown. Alternatively, agitator 100 may be combined with equipment in addition to or in addition to an impingement joint.

[0034] The top sub 102 and bottom sub 120 of the mixer 100 can each couple the mixer 100 to the drill string 24. The top sub 102 includes a first or uphole end 104, a second or downhole end 106 opposite the uphole end 104, and a central bore or passage 108 extending between the ends 104, 106. The top sub 102 also includes an internal uphole connector 110 at its uphole end 104 and formed on an inner surface of the top sub 102. The uphole connector 110 can be releasably or threadably connected to the drill string 24. Figure 1 The drill pipe joint 28 of the drill string 24 of the drilling system 10 is shown. The top joint 102 also includes an external downhole connector 112 at its downhole end 106 and formed on an outer surface of the top joint 102. The downhole connector 112 can be releasably or threadedly connected to the uphole end of the power joint 140 of the mixer 100.

[0035] In the exemplary embodiment, a dart guide 116 is connected to the top sub 102 and protrudes outwardly from the downhole end 106 of the top sub 102. The dart guide 116 includes a central bore or passageway having a diameter that gradually decreases from a first end or uphole end of the dart guide 116 connected to the downhole end 106 of the top sub 102 to a second end or downhole end opposite the uphole end of the dart guide 116. The dart guide 116 additionally includes a plurality of circumferentially spaced radial openings or ports. The dart guide 116 is configured to guide a flow-carrying obturating member or dart into the power sub 140 of the mixer 100. In addition, the dart guide 116 can help guide the flow of drilling fluid through the power sub 140 of the mixer 100. In addition, the tamper dart guide 116 may function as a rotor catch to prevent the rotor 160 of the power joint 140 from backing off and disengaging from the stator housing 142 of the power joint 140. Furthermore, it is understood that the blender 100 may not include the tamper dart guide 116 in other embodiments.

[0036] The bottom sub 120 includes a first or uphole end 122, a second or downhole end 124 opposite the uphole end 122, and a central hole or passage 126 extending between the ends 122, 124. The bottom sub 120 also includes an external uphole connector 128 at its uphole end 122 and formed on an outer surface of the bottom sub 120. As will be discussed further herein, the uphole connector 128 can be releasably or threadedly connected to a power sub 140 of the agitator 100. The bottom sub 120 also includes an external downhole connector 130 at its downhole end 124 and formed on an outer surface of the bottom sub 120. The downhole connector 130 can be releasably or threadedly connected to a drill pipe joint 28 of a drill string 24 of the drilling system 10.

[0037] Still reference Figure 2 , Figure 3A , Figure 3B , Figure 4 and Figure 5 The power connector 140 of the agitator 100 is generally configured to respond to the Figure 1 The supply pump 44 is shown to circulate the drilling fluid 40 by pumping it along a plurality of different flow paths at the surface. In the exemplary embodiment, the power joint 140 generally includes a housing or stator housing 142 and a rotor 160 rotatably disposed in the stator housing 142. The stator housing 142 has a central or longitudinal axis 145 (in Figure 514), and includes a first or uphole end 144, a second or downhole end 146, and a central passage defined by a generally cylindrical inner surface 148 extending between the ends 144, 146. The inner surface 148 of the stator housing 142 includes an inner first or uphole connector 150 positioned at the uphole end 144 and forming a first or uphole box end of the stator housing 142. The uphole connector 150 is configured for threaded coupling with the downhole connector 112 of the top sub 102 to couple the stator housing 142 with the top sub 102. In addition, an annular seal assembly may be positioned at an interface formed between the uphole end 144 of the stator housing 142 and the downhole end 106 of the top sub 102 to seal the connection formed therebetween.

[0038] The inner surface 148 of the stator housing 142 additionally includes an inner second or downhole connector 152 positioned at the downhole end 146 thereof, thereby forming a second or downhole box end of the stator housing 142. The downhole connector 152 of the stator housing 142 can be connected to the uphole connector 128 of the bottom joint 120. In the exemplary embodiment, a spiral elastomeric stator bushing or insert 154 is formed on the inner surface 148 of the stator housing 142. The spiral inner surface 156 of the stator insert 154 defines a plurality of stator lobes 158 (for clarity, the stator lobes 158 are not shown in FIG. 1 ). Figure 3A and Figure 3B In other embodiments, the stator housing 142 may not include inserts, but may include a single integrally formed body.

[0039] In the exemplary embodiment, rotor 160 has a central or longitudinal axis 175 ( Figure 5 ), and includes a first or uphole end 162, a second or downhole end 164 opposite the uphole end 162, and a helical outer surface 165 extending between the ends 162, 164, the helical outer surface 165 defining a plurality of rotor lobes 166 (for clarity, in Figure 3A and Figure 3B The rotor 160 further includes a central hole or passage 168 extending completely through the rotor 160 between the ends 162, 164, and a downhole receptacle 170 extending from the downhole end 164 of the rotor 160 into the rotor 160. As will be further described herein, in the exemplary embodiment, the rotor 160 interfaces with the rotary valve 200 of the agitator 100 via its downhole receptacle 170.

[0040] In the exemplary embodiment, the agitator 100 may include a flow-delivering tamping member or tamping dart 172 (eg, Figure 3A). Specifically, the agitator 100, including the joints 102, 120, the power joint 140, and the rotary valve 200, may initially be lowered into the wellbore 3 along the drill string 24 without the packing dart 172. The agitator 100 may then be operated within the wellbore 3 to induce oscillations in at least a portion of the drill string 24. At some point during the operation of the agitator 100, it may be desirable to adjust the frequency of the oscillations induced in the drill string 24 by the agitator 100. The packing dart 172 may be flowed or pumped through the drill string 24 from the surface 7 and landed within the power joint 140, whereby the agitator 100 may induce oscillations in the drill string 24 at a second frequency different from the first frequency. It will be appreciated that the packing dart 172 comprises an optional component that may not be pumped into the power joint 140 during each use of the agitator 100.

[0041] In the exemplary embodiment, the packing dart 172 includes a packing dart nozzle 174 positioned within the central passage of the packing dart 172. An outer lap profile 173 of the packing dart 172 is configured to overlap against an inner lap profile formed on a cylindrical inner surface of the rotor 160 defining the central passage 168 thereof. The packing dart 172 may additionally include a pair of annular seal assemblies formed on an outer surface thereof that are configured to sealingly engage the inner surface of the rotor 160 when overlapped into the inner surface of the rotor 160. The seal assemblies of the packing dart 172 may restrict fluid flow through an annular interface formed between the inner surface of the rotor 160 and the outer surface of the packing dart 172. Additionally, in the exemplary embodiment, when the packing dart 172 is pumped, the packing dart 172 is guided by the rotor guide 116 into the central passage 168 of the rotor 160. In particular, the gradual reduction in diameter of the central passage of the dart guide 116 centers the dart 172 within the power sub 140 to sufficiently align the central axis of the dart 172 and the central axis of the rotor 160 to allow the dart 172 to enter the central passage 168 of the rotor 160. The dart guide 116 may also prevent the rotor 160 from traveling uphole due to negative pressure that may occur following a wellbore kick.

[0042] like Figure 5As best shown in FIG. 1 , in the exemplary embodiment, the rotor 160 has one less lobe 166 than the stator housing 142. In this configuration, when the rotor 160 and stator housing 142 are assembled, a series of cavities 178 are formed between the outer surface 165 of the rotor 160 and the inner surface 156 of the stator insert 154 of the stator housing 142. Each cavity 178 is sealed from an adjacent cavity 178 by a seal formed along the line of contact between the stator housing 142 and the rotor 160. In addition, the central axis 175 of the rotor 160 is radially offset from the central axis 145 of the stator housing 142 by a fixed value, referred to as the "eccentricity" of the rotor-stator assembly. Therefore, the rotor 160 can be described as rotating eccentrically within the stator housing 142.

[0043] In the exemplary embodiment, the assembly of the stator housing 142 and the rotor 160 forms a progressive cavity device, and in particular, a progressive cavity motor configured to convert fluid pressure applied to the rotor-stator assembly into a rotational torque applied to the rotor 160. Specifically, during operation of the agitator 100, the drilling fluid 40 is pumped under pressure into the upstream end of the agitator 100. A first portion of the drilling fluid 40 entering the agitator 100 flows along a first or first flow path 180 extending through the central passage 168 of the rotor 160. A second portion of the drilling fluid 40 entering the agitator 100 instead flows around the central passage 168 of the rotor 160 along a second flow path 182 and enters the first set of open cavities 178. The pressure differential across adjacent cavities 178 forces the rotor 160 to rotate relative to the stator housing 142. As the rotor 160 rotates within the stator housing 142, adjacent cavities 178 open and are filled with the drilling fluid 40 flowing along the second flow path 182.

[0044] As this rotation and filling process is repeated in a continuous manner, the drilling fluid 40 flowing along the second flow path 182 flows progressively downward along the length of the stator housing 142 and continues to drive the rotation of the rotor 160. The rotor 160 rotates in a first rotational direction (given by Figure 5 In addition, the rotor 160 rotates about the central axis 145 of the stator housing 142 in a second rotation direction (indicated by the arrow 167 in FIG. 1 ) opposite to the first rotation direction of the arrow 167. Figure 5 The device is rotated upward (indicated by arrow 169).

[0045] Reference now Figure 3B , Figures 6 to 11 ,exist Figures 6 to 111. The rotary valve 200 of the agitator 100 is configured to periodically apply pressure of at least some of the drilling fluid 40 flowing through the rotary valve 200 to the bottom joint 120. The pressure pulses generated by the rotary valve 200 can be applied to the impact joint to periodically generate an oscillating motion in the drill string 24. In the exemplary embodiment, the rotary valve 200 generally includes a first or uphole valve adapter 202, a second or downhole valve adapter 230, a first or uphole valve plate or valve body 250, a second or downhole valve plate or valve body 280, and a flexible valve seat 310.

[0046] The uphole valve adapter 202 receives the uphole valve body 250 and couples or fixes the uphole valve body 250 to the rotor 160 of the power joint 140, thereby restricting relative rotation between the uphole valve body 250 and the rotor 160. Figure 6 As shown, the uphole valve adapter 202 includes a first or uphole end 204, a second or downhole end 206 opposite the uphole end 204, and a central hole or passage 208 extending between the ends 204, 206. The uphole valve adapter 202 also includes an external uphole connector 210 at its uphole end 204 and formed on an outer surface of the uphole valve adapter 202. The uphole connector 210 can be releasably or threadedly connected to a downhole connector formed on the receptacle 170 of the rotor 160, whereby the uphole valve adapter 202 can be received and fixed in the receptacle 170 to connect the uphole valve adapter 202 with the rotor 160. An annular seal assembly can be positioned at the interface between the receptacle 170 formed on the rotor 160 and the uphole end 204 of the uphole valve adapter 202 to seal the connection formed therebetween. Alternatively, a metal-to-metal seal can be formed directly between the receptacle 170 and the uphole valve adapter 202. The uphole valve adapter 202 also includes a downhole receptacle 212 formed therein at the downhole end 206 thereof. The downhole receptacle 212 may receive a portion of the uphole valve body 250 to secure the valve body 250 to the uphole valve adapter 202. For example, the uphole valve adapter 202 having the uphole valve body 250 received in the downhole receptacle 212 may be shrink-fitted onto the uphole valve body 250 via heat shrinking to lock the uphole valve adapter 202 to the valve body 250. In other embodiments, various mechanisms and techniques may be used to connect the uphole valve body 250 to the uphole valve adapter 202.

[0047] The downhole valve adapter 230 of the rotary valve 200 has a central or longitudinal axis 235 and similarly includes a first or uphole end 232, a second or downhole end 234 opposite the uphole end 232, and a central bore or passage 236 defined by a generally cylindrical inner surface 237 extending between the ends 232, 234. The downhole valve adapter 230 also includes an uphole receptacle 238 therein at its uphole end 232. The uphole receptacle 238 can receive a portion of a downhole valve body 280 to secure the valve body 280 to the downhole valve adapter 230.

[0048] The downhole valve adapter 230 also includes an external downhole connector 240 at its downhole end 234 and formed on an outer surface of the downhole valve adapter 230. The downhole connector 240 can be releasably or threadedly connected to the uphole end 122 of the bottom sub 120 to couple the downhole valve adapter 230 and the downhole valve body 280 to the bottom sub 120. An annular seal assembly can be positioned at an interface formed between the downhole end 234 of the downhole valve adapter 230 and the uphole end 122 of the bottom sub 120 to seal the connection formed therebetween. In addition, as will be further described herein, a flexible valve seat 310 is also received in the uphole receptacle 238 and is located between the downhole valve adapter 230 and the portion of the downhole valve body 280 received in the receptacle 238. As will be further described herein, the flexible valve seat 310 provides a flexible connection between the downhole valve body 280 and the downhole valve adapter 230 so that the valve body 280 can flex relative to the valve adapter 230 and the bottom sub 120 connected thereto.

[0049] Especially Figure 6 and Figure 7 As shown, the uphole valve body 250 of the rotary valve 200 has a central or longitudinal axis 251 (eg, Figure 6250 ), and generally includes a first or uphole end 252, a second or downhole end 254 opposite the uphole end 252, a central bore or passage 256 defined by a generally cylindrical inner surface 258 extending between the ends 252, 254, and a generally cylindrical outer surface 260 also extending between the ends 252, 254. The downhole end 254 defines a generally planar downhole contact surface 255 of the uphole valve body 250. In the exemplary embodiment, the uphole valve body 250 additionally includes a plurality of circumferentially spaced uphole flow passages 262. Each uphole flow passage 262 extends from the downhole contact surface 255 to the outer surface 260 of the uphole valve body 250. As will be further discussed herein, when the valve bodies 250 and 280 of the rotary valve 200 are in an open configuration, the uphole flow passage 262 can communicate with a corresponding flow passage of the downhole valve body 280 to maximize the flow area therethrough, thereby minimizing the pressure drop across the rotary valve 200. In the exemplary embodiment, one or more uphole cooling ports 257 are formed in and extend to a downhole contact surface 255 of uphole valve body 250 .

[0050] Additionally, in the exemplary embodiment, uphole valve body 250 includes a plurality of circumferentially spaced radial ports 264. In particular, each radial port 264 is circumferentially aligned with a corresponding flow channel 262. In this configuration, each radial port 264 extends from a corresponding flow channel 262 to central channel 256 of uphole valve body 250, thereby providing fluid communication between flow channel 262 and central channel 256.

[0051] The downhole valve body 280 of the rotary valve 200 has a central or longitudinal axis 281 and generally includes a first or uphole end 282, a second or downhole end 284 opposite the uphole end 282, a central bore or passage 286 defined by a generally cylindrical inner surface 288 extending between the ends 282, 284, and a generally cylindrical outer surface 290 also extending between the ends 282, 284. The uphole end 282 of the downhole valve body 280 defines a generally planar uphole contact surface 285 of the downhole valve body 280. As will be further described herein, a metal-to-metal seal is formed between the downhole contact surface 255 of the uphole valve body 250 and the uphole contact surface 285 of the downhole valve body 280, whereby relative rotation between the valve bodies 250 and 280 causes the rotary valve 200 to cyclically shift between an open configuration and a closed configuration. In the exemplary embodiment, one or more downhole cooling ports 287 (in Figure 82 (shown in FIG. 2 ) is formed at and extends to the uphole contact surface 285 of the downhole valve body 280. The downhole cooling port 287 of the downhole valve body 280 is in fluid communication with the uphole cooling port 257 of the uphole valve body 250. The cooling ports 257, 287 of the valve bodies 250 and 280 hold a fluid (e.g., drilling fluid) for cooling the valve bodies 250 and 280. It will be appreciated that in other embodiments, the valve bodies 250 and 280 may not include cooling ports 257 and 287, respectively.

[0052] In the exemplary embodiment, the downhole valve body 280 includes a plurality of circumferentially spaced apart downhole flow passages 298. Each downhole flow passage 298 extends from the uphole contact surface 285 to the outer surface 290 of the downhole valve body 280. As will be discussed further herein, when the rotary valve 200 is in the open configuration, the downhole flow passage 298 may communicate with a corresponding uphole flow passage 262 of the uphole valve body 250, while when the rotary valve 200 is in the closed configuration, fluid communication directly between the flow passages 262 and 298 is restricted.

[0053] The uphole valve body 250 is positioned axially adjacent to the downhole valve body 280, whereby the downhole contact surface 255 of the uphole valve body 250 may contact the uphole contact surface 285 of the downhole valve body 280. In some embodiments, a substantially planar metal-to-metal sealing interface 275 (at the interface 275) is formed between portions of the downhole contact surface 255 of the uphole valve body 250 that contact the uphole contact surface 285 of the downhole valve body 280. Figure 6 ), thereby limiting fluid communication across the sealing interface 275. The valve bodies 250 and 280 may be formed of a hardened material configured to resist frictional wear, such as a tungsten-based material, such as tungsten carbide. In this exemplary embodiment, the uphole valve body 250 is rotationally locked to the rotor 160 of the power joint 140, while the downhole valve body 280 is typically rotationally locked to the stator housing 142 of the power joint 140 (the flexible valve seat 310 allows a limited degree of movement between the valve body 280 and the stator housing 142).

[0054] Especially Fig.11 As shown, the downhole valve body 280 is connected to the downhole valve adapter 230 via a flexible valve seat 310, which allows a limited degree of relative movement between the downhole valve body 280 and both the downhole valve adapter 230 and the bottom joint 120. Although in this exemplary embodiment, the downhole valve body 280 is connected to the flexible valve seat 310, in other embodiments, only the uphole valve body 250 can be connected to the flexible valve seat 310, and in other embodiments, each valve body 250 and 280 can be connected to a separate flexible valve seat. It can be understood that in embodiments in which each valve body 250 and 280 is connected to a separate flexible valve seat, the stiffness of the flexible valve seat can be greater.

[0055] The flexible valve seat 310 is formed of a flexible material to allow a limited degree of relative movement or flexure between the downhole valve body 280 and the downhole valve adapter 230. For example, in some embodiments, the flexible valve seat 310 is formed of an elastomeric material or a 6 rubber material. In some embodiments, the flexible valve seat 310 includes a material having a hardness between about 40 and 120 on the Shore A hardness scale. In some embodiments, the flexible valve seat 310 includes a material having a hardness between about 70 and 90 on the Shore A hardness scale. It will be appreciated that in other embodiments, the hardness of the flexible valve seat 310 may be different from the exemplary ranges listed above.

[0056] Especially Fig.11 As shown, in the exemplary embodiment, the flexible valve seat 310 includes a first or uphole end 312, a second or downhole end 314 opposite the uphole end 312, and a central bore or passage defined by an inner surface 316 extending between the ends 312 and 314, and an outer surface 318 also extending between the ends 312 and 314. The inner surface 316 contacts and is attached to the outer surface 290 of the downhole valve body 280, while the outer surface 318 of the flexible valve seat 310 contacts and is attached to the inner surface 237 of the downhole valve adapter 230. In the exemplary embodiment, the inner surface 316 seals against the outer surface 290 of the downhole valve body 280, while the outer surface 318 seals against the inner surface 237 of the downhole valve adapter 230, thereby sealing the connection between the downhole valve body 280 and the downhole valve adapter 230.

[0057] In some embodiments, an adhesive (such as a vulcanized adhesive) is positioned along an interface formed between the inner surface 316 of the flexible valve seat 310 and the outer surface 290 of the downhole valve body 280 and / or along an interface formed between the outer surface 318 of the flexible valve seat 310 and the inner surface 237 of the downhole valve adapter 230. The adhesive may help resist relative rotation between the downhole valve body 280 and the downhole valve adapter 250 due to frictional contact between the valve adapters 250 and 280 during operation of the mixer 100. In other embodiments, the downhole valve body 280 may be mechanically interlocked with the downhole valve adapter 250 to resist relative rotation therebetween. For example, the downhole valve body 280 may include an external tongue that is interlockingly received in an internal groove of the downhole valve adapter 250 as part of a tongue-and-groove or dovetail arrangement.

[0058] In the exemplary embodiment, the flexible valve seat 310 includes a cylindrical portion or segment 320, and an annular flange or shoulder 322 located at its downhole end 314 and extending radially inward from the cylindrical segment 310 of the flexible valve seat 310. Deformation of the cylindrical segment 320 and the flange 322 allows a limited degree of angular misalignment between the central axis 281 of the downhole valve body 280 and the central axis 235 of the downhole valve adapter 230.

[0059] In the exemplary embodiment, the inner surface 316 of the flexible valve seat 310 tapers along the longitudinal length of its cylindrical section 320 such that the inner diameter (ID) of the inner surface 316 decreases from its uphole end 312 to the flange 322. The taper of the flexible valve seat 310 matches the taper formed along the portion of the outer surface 290 of the downhole valve body 280 that is received in the uphole receiving seat 238 of the downhole valve adapter 230. In some embodiments, the taper formed along the inner surface 316 of the flexible valve seat 310 and the outer surface 290 of the downhole valve body 280 is between about 0° and 10°; however, in other embodiments, the taper along the surfaces 290 and 316 may vary. The taper of the flexible valve seat 310 and the downhole valve body 280 may strengthen the connection formed between the downhole valve body 280 and the flexible valve seat 310, such that the connection formed therebetween is less likely to be compromised or damaged during operation of the mixer 100.

[0060] In particular, in some embodiments, the flexible material is compression molded with the downhole valve body 280 and the downhole valve adapter 250 to form an assembly including the adapter 250, the body 280, and the flexible valve seat 310, wherein the body 280 and the valve seat 310 are each received in an uphole receiving seat 328 of the downhole valve adapter 250. For example, with the flexible material (e.g., an elastomeric material) first positioned in the uphole receiving seat 328 of the downhole valve adapter 230, the downhole end 284 of the downhole valve adapter 280 is inserted into the uphole receiving seat 328. The downhole end 284 of the downhole valve adapter 280 can then be pressed against the flexible material to form the flexible valve seat 310 and connect the flexible valve seat 310 to both the downhole valve body 280 and the downhole valve adapter 230. However, it is understood that the flexible valve seat 310 can be formed and the assembly of the valve adapter 230, the valve body 280, and the flexible valve seat 310 can be assembled using a variety of different techniques.

[0061] Reference now Fig.12, another embodiment of a downhole valve body 400 and a flexible valve seat 420 is shown, along with a downhole valve adapter 230. The downhole valve body 400 and the flexible valve seat 420 share features common to the downhole valve body 280 and the flexible valve seat 310 described above, and the shared features are similarly labeled. In particular, the downhole valve body 400 is similar to the downhole valve body 280, and the flexible valve seat 420 is similar to the flexible valve seat 310, but neither the valve body 400 nor the flexible valve seat 420 is tapered. In particular, the portion of the outer surface 402 of the downhole valve body 400 that is received in the uphole receiving seat 238 of the downhole valve adapter 230 is not tapered along its longitudinal length. Similarly, the inner cylindrical surface 422 of the cylindrical portion or segment 424 of the flexible valve seat 420 is also not tapered along its longitudinal length.

[0062] Additionally, in the exemplary embodiment, the flexible valve seat 420 includes a plurality of circumferentially spaced preformed holes or openings 426. Specifically, the openings 426 are formed in the cylindrical section 424 of the flexible valve seat 420; however, it is understood that in other embodiments, the openings 426 may be formed in the flange 322 of the flexible valve seat 420. The openings 426 provide space for the flexible material comprising the flexible valve seat 420 to flow or deform in response to flexing of the downhole valve body 400 relative to the downhole valve adapter 230. The presence of such openings 426 may reduce the amount of stress and strain applied to the flexible valve seat 420 as the downhole valve body 400 flexes and moves relative to the downhole valve adapter 230.

[0063] Reference now Fig.13 , another embodiment of a flexible valve seat 440 is shown along with a downhole valve body 400 and a downhole valve adapter 230. The flexible valve seat 440 shares features common to the flexible valve seats 310 and 420 described above, and the shared features are similarly labeled. In particular, the flexible valve seat 440 is similar to the flexible valve seat 400 described above, except that the flexible valve seat 440 does not include an opening 426, but rather includes a body 441 and an annular spacer ring 442 located or embedded within a cylindrical portion or segment 444 of the body 41. In this configuration, the spacer ring 442 extends completely around the downhole valve body 400 and is oriented in a direction parallel to the central axis of the downhole valve body 400. The body 441 can be formed of a first material (e.g., an elastomeric material or other flexible material), while the spacer ring 442 can be formed of a second rigid material having a greater hardness than the first material.

[0064] The spacer ring 442 is formed of a rigid material and is configured to substantially prevent the downhole valve body 400 from being laterally deflected from the downhole valve adapter 230 (wherein the central axis of the body 400 becomes laterally spaced apart from the central axis 235 of the downhole valve adapter 230) via interference between the downhole valve body 400 and the spacer ring 442. Limiting the formation of lateral deflection between the downhole valve body 400 and the downhole valve adapter 230 can limit the stresses and strains experienced by the flexible valve seat 440 during operation, and thus can extend the working life of the flexible valve seat 440 and / or the downhole valve body 400. However, while intended to limit or prevent the formation of lateral deflection between the downhole valve body 400 and the downhole valve adapter 230, the spacer ring still allows a limited degree of angular misalignment between the central axis of the valve body 400 and the valve adapter 230.

[0065] Reference now Fig.14 , another embodiment of a downhole valve adapter 460 and a flexible valve seat 480 is shown, along with a downhole valve body 400. The downhole valve adapter 460 and the flexible valve seat 480 share features common to the downhole valve adapter 230 and the flexible valve seat 310 described above, and the shared features are similarly labeled. In particular, in this exemplary embodiment, the flexible valve seat 480 includes an annular mechanical biasing member in the form of a wave spring or washer that acts on the downhole end 284 of the downhole valve body 400 and an annular flange 462 of the downhole valve adapter 460, which is formed along the uphole receiving seat 238 of the valve adapter 460. In this exemplary embodiment, the flexible valve seat 480 can be formed of a more rigid material (e.g., a metallic material or a metal alloy) than the material that constitutes the flexible valve seat 310 described above, while still allowing a limited degree of angular misalignment between the central axis of the downhole valve body 400 and the central axis 235 of the downhole valve adapter 460.

[0066] Additionally, in the exemplary embodiment, given that the flexible valve seat 480 does not seal the connection formed between the downhole valve body 300 and the downhole valve adapter 460, the downhole valve adapter 460 includes an annular seal assembly 464 positioned along its uphole receiving seat 238 that seals against the outer surface 290 of the downhole valve body 460. In this configuration, the seal assembly 464 seals the connection formed between the downhole valve body 400 and the downhole valve adapter 460.

[0067] Reference now Figures 1 to 3BDuring operation of the mixer 100, pressurized drilling fluid 40 may be pumped from the supply pump 44 through the drill string 24 and into the top sub 102 of the mixer 100. A first portion of the drilling fluid 40 entering the mixer 100 flows along a first flow path 180 through the central passage 168 of the rotor 160, into and through the rotor nozzles 177 of the power sub 140. Different from the first portion, a second portion of the drilling fluid 40 flows along a second flow path 182 into a first set of open cavities 178 formed between the stator housing 142 and the rotor 160. The flow of the pressurized drilling fluid along the second flow path 182 causes the rotor 160 to rotate relative to the stator housing 142 about the central axis 175.

[0068] The rate of rotation of the rotor 160 about the central axis 175 depends on the amount of drilling fluid 40 diverted to the second flow path 182. In turn, the amount of drilling fluid 40 diverted to the second flow path relative to the amount of drilling fluid 40 flowing along the first flow path 180 can be controlled by the degree of flow restriction along the flow paths 180 and 182. In addition, as described above, if desired, the packing dart 172 can be pumped through the drill string 24 and overlapped within the central passage 168 of the rotor 160. The overlap of the packing dart 172 within the rotor 160 positions the packing dart nozzle 174 along the first flow path 180, thereby providing additional flow restriction along the first flow path 180. The additional flow restriction provided by the packing dart nozzle 174 increases the amount of drilling fluid 40 flowing along the second flow path 182 relative to the first flow path 180, thereby increasing the rate of rotation of the rotor 160 at a given flow rate of drilling fluid 40 entering the power sub 140. Increasing the rotation rate of the rotor 160 may increase the frequency of the pressure pulses generated by the agitator 100 .

[0069] Although in this exemplary embodiment, the power joint 140 is used to drive the relative rotation of the valve bodies 250 and 280, in other embodiments, the mixer 100 may not include the power joint 140, but may use different mechanisms to provide relative rotation between the valve bodies 250 and 280. For example, an electric motor that can be driven by a battery or a generator can be used to drive the rotation of the uphole valve body 250. The downhole electric motor can communicate with a downhole sensor group configured to determine the axial displacement of the bottom joint 120. The electric motor can be controlled by a controller to use the sensor group by adjusting the rotation rate of the uphole valve body 250 relative to the downhole valve body 280, thereby achieving the desired size or frequency of the axial displacement of the bottom joint 120. In other embodiments, the power joint 140 may include a solid rotor that does not include a central channel extending therethrough.

[0070] Due to the rotational lock to the rotor 160, the uphole valve body 250 also rotates about the central axis 175 relative to the downhole valve body 280, wherein the downhole valve body 280 remains stationary relative to the stator housing 142. Generally, in this manner, the relative rotation between the uphole valve body 250 and the downhole valve body 280 corresponds to the rotation rate of the rotor 160 relative to the stator housing 142. As the uphole valve body 250 rotates relative to the downhole valve body 280, the flow passage 262 of the uphole valve body 250 moves into and out of circumferential alignment or overlap with the flow passage 298 of the downhole valve body 280. In the open configuration of the rotary valve 200, fluid communication is directly provided between the flow passage 262 of the uphole valve body 250 and the flow passage 298 of the downhole valve body 280. However, when the rotary valve 200 is in closed communication, the fluid communication is directly limited between the flow passages 262 by the sealing interface 275 formed between the valve bodies 250, 280. As the uphole valve body 250 rotates relative to the downhole valve body 280 , the rotary valve 200 is cyclically actuated between the open configuration and the closed configuration at a rate that depends on the relative rotational speed between the uphole valve body 250 and the downhole valve body 280 .

[0071] When the rotary valve 200 is in the open configuration, the first portion of the drilling fluid 40 flowing along the second flow path 182 flows along the third flow path 184 (at Figure 6 100 , wherein the third flow path 184 extends from the second flow path 182 and enters the flow passage 262 of the uphole valve body 250, extends through the flow passage 298 of the downhole valve body 280, and enters the central passage 236 of the downhole valve adapter 230. The drilling fluid 40 flowing along the third flow path 184 exits the mixer 100 via the central passage 126 of the bottom sub 120, wherein the drilling fluid 40 may be communicated to downstream components, such as a portion of the drill string 24 positioned downstream of the mixer 100 and a BHA 30 connected to the end of the drill string 24.

[0072] When the rotary valve 200 is in the closed configuration, the sealing contact between the contact surface 255 of the valve body 250 and the contact surface 285 of the valve body 280 accordingly prevents the drilling fluid 40 from passing directly between the flow channel 262 of the valve body 250 and the flow channel 298 of the valve body 280. In contrast, the drilling fluid 40 flowing along the second flow path 182 can only pass through the fourth flow path 186 (such as Figure 7The fourth flow path 186 extends from the second flow path 182 into the flow channel 262 of the uphole valve body 250, and from the flow channel 262 into the central channel 256 of the valve body 250 via a plurality of radial ports 264 connected to the flow channel 262. The drilling fluid 40 flowing along the fourth flow path 186 can continue to flow from the central channel 256 through the central channel 236 of the downhole valve adapter 230, and from there can leave the mixer 100 via the central channel 126 of the bottom joint 120.

[0073] However, it will be appreciated that the radial port 264 has a smaller flow area than the flow passage 262 of the uphole valve body 250. In this configuration, the minimum flow area through the rotary valve 200 when the rotary valve 200 is in the open configuration is greater than the minimum flow area through the rotary valve 200 when the valve 200 is in the closed configuration. As the valve 200 cycles between the open configuration and the closed configuration, the difference in the minimum flow area of ​​the rotary valve 200 triggers the generation of cyclic or repetitive fluid or hydraulic pressure pulses emanating from the agitator 100, and the fluid or hydraulic pressure pulses can be converted into oscillatory axial motion in the drill string 26 by a percussion tool connected to the agitator 100.

[0074] Furthermore, due to misalignment between the stator housing 142 and the stator insert 154 received therein, a central axis 175 of the rotor 160 (the rotor 160 being positioned within the stator housing 142 via the stator insert 154) may extend at a non-zero angle relative to a central axis of the stator housing 142. The magnitude of the angle formed between the central axis 175 of the rotor 160 and the central axis of the stator housing 145 may vary as the rotor 160 rotates within the stator housing 142.

[0075] Misalignment between the stator housing 142 and the stator insert 154 may result from an eccentric stator liner 154 resulting from manufacturing tool tolerances and process variations that naturally occur during the formation of the stator liner 154. Typically, the longitudinally opposing ends of the stator liner 154 (and other stator liners like the stator liner 154) tend to be offset in opposite directions (approximately 180° apart) relative to the centerline of the stator liner 154. The offset of the stator liner 154 (which varies along the longitudinal length of the liner 154) creates a corresponding offset in the rotor 160 positioned within the stator liner 154, resulting in an angular misalignment between the rotor 160 and the stator housing 142. In addition, considering that the uphole valve body 250 is fixed to the downhole accommodating seat 170 of the rotor 160, the central axis 251 of the uphole valve body 250 is similarly positioned to form a non-zero angle with the central axis of the stator housing 142, wherein the size of the non-zero angle can change as the uphole valve body 250 rotates in unison with the rotor 160 relative to the stator housing 142.

[0076] As described above, the valve bodies 250 and 280 may be formed of a hardened, wear-resistant material in order to resist frictional contact occurring between the contact surface 255 of the valve body 250 and the contact surface 285 of the valve body 280. However, such materials may be relatively brittle and susceptible to damage in response to elevated point loads (areas of localized elevated stress and strain) applied to the hardened material. Additionally, in the absence of a corresponding angular misalignment between the downhole valve body 280 and the stator housing 142, an angular misalignment between the uphole valve body 250 and the stator housing 142 may result in a corresponding angular misalignment between the central axis 251 of the valve body 250 and the central axis 281 of the valve body 280. Such an angular misalignment between the valve bodies 250 and 280 may result in only a small portion of the contact surface 255 of the uphole valve body 250 being in contact with the contact surface 285 of the downhole valve body 280 at a given time, thereby resulting in potentially damaging point loads being applied to the valve bodies 250 and 280 due to the angular misalignment between the valve bodies 250 and 280.

[0077] However, as described above, the flexible valve seat 310 (and Figure 12 to Figure 14 The flexible valve seats 420, 440, and 480 shown in FIG. 4A and 4B allow the central axis 281 of the downhole valve body 280 to enter a limited degree of misalignment with the central axis 235 of the downhole valve adapter 230 (and thus also with the stator housing 142 and with the adapter 230 connected to the housing 142 via the bottom sub 120) in response to contact between the valve bodies 250 and 280. For example, the flexible valve seat 310 allows the central axis 281 of the downhole valve body 280 to enter an angular misalignment whereby the central axis 281 extends at a non-zero acute angle relative to the central axis 235 (e.g., Fig.11 ). In some embodiments, the flexible valve seat 310 allows a maximum angular misalignment between the central axis 281 of the downhole valve body 280 and the central axis 235 of the downhole valve adapter 235 of between about 0.01° and 5.00°. In some embodiments, the flexible valve seat 310 allows a maximum angular misalignment between the central axis 281 of the downhole valve body 280 and the central axis 235 of the downhole valve adapter 235 of between about 2.00° and 4.00°. However, it will be appreciated that the degree of angular misalignment allowed by the flexible valve seat 310 may vary.

[0078] The non-zero angle formed between the central axis 281 of the downhole valve body 280 and the central axis 235 of the downhole valve adapter 230 may result from contact between the downhole valve body 280 and the uphole valve body 250, which, as described above, is misaligned relative to the stator housing 142. The non-zero angle formed between the central axis 281 of the downhole valve body 280 and the central axis 235 of the downhole valve adapter 230 may thus substantially match or correspond to a corresponding non-zero angle formed between the central axis 251 of the uphole valve body 250 and the central axis 235 of the downhole valve adapter 230. In this way, as the downhole valve body 280 continuously flexes within the downhole valve adapter 230 in response to the continuously changing misalignment that occurs between the uphole valve adapter 250 and the stator housing 142 as the adapter 250 rotates within the housing 142, any angular misalignment between the valve bodies 250 and 280 caused by misalignment between the uphole valve body 250 and the stator housing 142 (e.g., due to an offset in the formation of the stator bushing 154) is automatically minimized (the central axes 251 and 281 of the valve bodies 250 and 280 remain substantially parallel).

[0079] Minimization of the angular misalignment between the central axis 251 of the valve body 250 and the central axis 281 of the valve body 280 in turn minimizes point loads and associated maximum stresses and strains applied to the valve bodies 250 and 280 along their contact surfaces 255 and 285, respectively. In contrast, the loads generated by the frictional contact between the valve bodies 250 and 280 are relatively evenly distributed along the contact surfaces 255 and 295 of the valve bodies 250 and 280, respectively. The reduction in point loads applied to the contact surface 255 of the valve body 250 and the contact surface 285 of the valve body 280 can reduce the likelihood of damage to the valve bodies 250 and 280 during operation, and thus can maximize the operating life of the valve bodies 250 and 280.

[0080] Although the disclosed embodiments have been shown and described, modifications thereto may be made by those skilled in the art without departing from the scope or teachings herein. The embodiments described herein are intended to be exemplary only and not restrictive. Many variations and modifications of the systems, devices, and processes described herein are possible and are within the scope of the present disclosure. Therefore, the scope of protection is not limited to the embodiments described herein, but is limited only by the appended claims, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recording of identifiers such as (a), (b), (c) or (1), (2), (3) before the steps in a method claim is not intended to and does not specify a particular order of the steps, but is used to simplify subsequent references to those steps.

Claims

1. A stirrer that can be deployed in a wellbore, the stirrer comprising: a housing, the housing comprising a central axis and a central passage; a valve disposed in the housing and comprising a first valve body and a second valve body allowed to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface configured to contact the first contact surface; a first valve adapter coupled to the housing and including a first receptacle that receives at least a portion of the first valve body to couple the first valve adapter to the first valve body; as well as a flexible valve seat positioned in the first receiving seat of the first valve adapter between the first valve body and the first valve adapter, and wherein the flexible valve seat is configured to allow the first valve body to flex relative to the first valve adapter, thereby potentially creating an angular misalignment between a central axis of the first valve body and a central axis of the first valve adapter.

2. The agitator according to claim 1, wherein The flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter of between 0.01° and 5.00°.

3. The agitator according to claim 1, wherein: The flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter of between 2.00° and 4.00°.

4. The agitator according to claim 1, further comprising: a stator positioned in the housing; as well as A rotor is rotatably positioned in the stator and is connected to one of the first valve body and the second valve body.

5. The agitator according to claim 1, wherein The flexible valve seat includes a mechanical biasing member configured to apply a biasing force to the first valve body.

6. The agitator according to claim 1, wherein The flexible valve seat is formed of an elastomeric material.

7. The agitator according to claim 1, wherein: The flexible valve seat is formed from a material having a durometer rating between 40 and 120 on the Shore A hardness scale.

8. The agitator according to claim 1, wherein The flexible valve seat seal forms a connection between the first valve body and the first valve adapter.

9. The agitator according to claim 1, wherein: The flexible valve seat includes a body and a spacer ring embedded in the body, wherein the body is formed of a first material having a first hardness, and the spacer ring is formed of a second material having a second hardness greater than the first hardness.

10. An agitator capable of being deployed in a wellbore, comprising: a housing, the housing comprising a central axis and a central passage; a valve disposed in the housing and comprising a first valve body and a second valve body allowed to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface configured to contact the first contact surface; a first valve adapter coupled to the housing and including a first receptacle that receives at least a portion of the first valve body to couple the first valve adapter to the first valve body; as well as A flexible valve seat is positioned in the first receiving seat of the first valve adapter between the first valve body and the first valve adapter, and wherein the flexible valve seat is formed of a material having a durometer rating between 40 and 120 on the Shore A hardness scale.

11. The agitator according to claim 10, wherein The material forming the flexible valve seat has a durometer rating of between 70 and 90 on the Shore A hardness scale.

12. The agitator according to claim 10, further comprising: a stator positioned in the housing; as well as A rotor is rotatably positioned in the stator and is connected to one of the first valve body and the second valve body.

13. The agitator according to claim 10, wherein The flexible valve seat is configured to allow the first valve body to flex relative to the first valve adapter, thereby enabling an angular misalignment between a central axis of the first valve body and a central axis of the first valve adapter.

14. The agitator according to claim 13, wherein The flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter of between 0.01° and 5.00°.

15. The agitator according to claim 10, wherein The flexible valve seat seal forms a connection between the first valve body and the first valve adapter.

16. An agitator capable of being deployed in a wellbore, comprising: a housing, the housing comprising a central axis and a central passage; a valve disposed in the housing and comprising a first valve body and a second valve body allowed to rotate relative to the first valve body, the first valve body having a first contact surface, the second valve body having a second contact surface configured to contact the first contact surface; a first valve adapter coupled to the housing and including a first receptacle that receives at least a portion of the first valve body to couple the first valve adapter to the first valve body; as well as A flexible valve seat is positioned in the first receiving seat of the first valve adapter and seals a connection formed between the first valve body and the first valve adapter.

17. The agitator according to claim 16, wherein The flexible valve seat is adhered to both the first valve body and the first valve adapter.

18. The agitator according to claim 16, further comprising: a stator positioned in the housing; as well as A rotor is rotatably positioned in the stator and is connected to one of the first valve body and the second valve body.

19. The agitator according to claim 16, wherein The flexible valve seat is configured to allow the first valve body to flex relative to the first valve adapter, thereby enabling an angular misalignment between a central axis of the first valve body and a central axis of the first valve adapter.

20. The agitator according to claim 19, wherein The flexible valve seat is configured to allow a maximum angular misalignment between the central axis of the first valve body and the central axis of the first valve adapter of between 0.01° and 5.00°.

21. The blender of claim 16, further comprising: a second valve adapter coupled to the housing and including a second receptacle that receives at least a portion of the second valve body to couple the second valve adapter to the second valve body; Wherein, the flexible valve seat includes a first flexible valve seat, and the agitator further includes a second flexible valve seat, the second flexible valve seat is positioned in the second receiving seat of the second valve adapter, and the second flexible valve seat seal forms a connection between the second valve body and the second valve adapter.

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