TECHNICAL FIELD
The present disclosure relates to downhole assemblies utilizing a motor to drive downhole tools, and selective activation of the motor.
TECHNICAL BACKGROUND
When drilling deep bore holes in the earth, sections of the bore hole can cause drag or excess friction which may hinder weight transfer to the drill bit, or cause erratic torque in the drill string. These effects may have the result of slowing down the rate of penetration, creating bore hole deviation issues, or even damaging drill string components.
Friction tools are often used to overcome these problems by vibrating a portion of the drill string to mitigate the effect of friction or hole drag. These friction tools form part of the downhole assembly of the drilling string, and can be driven by the variations in the pressure of drilling fluid (which may be air or liquid, such as drilling mud) flowing through the friction tool. Accordingly, the operation or effectiveness of a friction tool—namely, the frequency of vibrations generated by the friction tool—may be affected by the flow rate of drilling fluid pumped through the string. Controlling the frequency of vibration thus may involve varying the flow rate of the drilling fluid at the surface, and ceasing operation of the friction tool may require cutting off the flow of drilling fluid at the surface. Varying or cutting off the drilling fluid flow, however, may impact the operation of other components in the drilling string.
Furthermore, it is not always desirable to run a friction tool during the entirety of a drilling operation. For instance, it may be unnecessary or undesirable to run the tool while the drill bit is at a shallow depth, or at other stages of the drilling operation where the added vibration of the friction tool is problematic. During those stages, the drill string may be assembled without the friction tool. However, when a location in the bore hole is reached where the need for a friction tool is evident, it is then necessary to pull the downhole assembly to the surface to reassemble the drilling string to include the friction tool, then return the drilling string to the drill point. This process can consume several work hours.
BRIEF DESCRIPTION OF THE DRAWINGS
In drawings which illustrate by way of example only embodiments of the present disclosure, in which like reference numerals describe similar items throughout the various figures,
FIG. 1 is a lateral cross-sectional view of a portion of a downhole assembly.
FIG. 2 is a lateral cross-sectional view of a rotor assembly for use in the downhole assembly.
FIGS. 3 and 4 are perspective and lateral cross-sectional views, respectively, of a catch for use in the downhole assembly.
FIGS. 5 and 6 are sectional views of the downhole assembly of FIG. 1 when the catch is in a first state.
FIGS. 7 and 8 are sectional views of the downhole assembly of FIG. 1 when the catch is in a second state.
FIGS. 9 and 10 are sectional views of the downhole assembly of FIG. 1 with an alternative catch configuration.
FIG. 11 is a further sectional view of the downhole assembly of FIG. 1.
FIGS. 12-13 are lateral cross-sectional views of a rotating valve assembly that may be used with the downhole assembly.
FIGS. 14-15 are lateral cross-sectional views of a variant of the rotating valve assembly of FIGS. 12-13.
FIG. 16 is a lateral cross-sectional view of a portion of a further example downhole assembly.
FIG. 17 is an enlarged view of a section of the downhole assembly of FIG. 16.
FIG. 18 is a side view of a thrust unit of the downhole assembly of FIG. 16.
FIG. 19 is a cross-sectional view of the thrust unit of FIG. 18 taken along the plane indicated by line a-a.
FIG. 20 is a side view of a hanger of the downhole assembly of FIG. 16.
FIG. 21 is a cross-sectional view of the hanger of FIG. 20 taken along the plane indicated by line b-b.
FIGS. 22A and 22B are enlarged views of the section of FIG. 16 before and after activation of the assembly by a blocking implement received in the catch of the assembly.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 generally illustrates a lateral cross-section of a portion of an example downhole assembly 10 as it may be assembled within a drilling string for downhole operation. In this example, the exterior of the assembly 10 is defined by interconnected housing components 11, 40, and 60, and the exterior of the stator 20. These components are provided as independent components to facilitate assembly, transport, and repair in the event of failure of an individual component of the assembly 10 and may be connected using appropriate means, such as threaded connections. However, as those skilled in the art will appreciate, in some implementations these housing components 11, 40, and 60 and/or stator 20 may be modified and/or combined without affecting the operation of the inventions described herein. In this particular illustrated example, housing component 11 can house a drilling string component such as an oscillation assembly 13, while housing 40 is a shaft housing, and housing 60 is a valve housing enclosing a valve assembly. As will also be appreciated by those skilled in the art, the particular features of the motor assembly and the valve assembly discussed herein need not be used together to realize the advantages of these features, nor need they be used with the other subs or downhole assembly 10 components or tools mentioned herein.
In the example assembly 10 of FIG. 1, the motor is a Moineau-type motor with a multi-lobe rotor 25 rotating in a multi-lobe stator 20. Appropriate rotor/stator ratios may be selected to drive downhole components according to the desired frequency of operation of the drilling string. In example embodiments, a 6/7 or 7/8 ratio, or a sufficiently high ratio of rotor to stator lobes is employed in order to provide a rotor 25 of sufficiently large cross-sectional area to maximize the size of the bore or passage 22 in the body of the rotor 25, as discussed below. An end of the rotor can be coupled to a driveshaft 45, for instance using a universal joint or other suitable connector, to enable the transmission of torque from the rotor to other components in the assembly 10.
In this particular example, the driveshaft 45 is coupled by another universal joint 50 to a valve assembly including a rotating valve component 65 and a corresponding stationary valve component 70. This valve assembly may be used to activate the oscillation tool 13, for example by varying the flow of drilling fluid and fluid pressure. The oscillation tool 13 can be positioned elsewhere in the downhole assembly 10 sufficiently close to the valve assembly so as to be affected by the variations in fluid pressure. Such a valve assembly includes a rotating flow head 65 and a stationary flow restrictor 70, each with ports that enter into and out of alignment as the flow head rotates against the flow restrictor so as to vary the flow of drilling fluid through the entire valve assembly during operation. Variations of such a flow-varying valve assembly are described in further detail below. As mentioned above, while this valve assembly may operate in concert with the other features of the present motor assembly to be described in further detail below, the motor assembly and the valve assembly can be used independently. In the illustrated embodiment, the downhole assembly 10 can function as a friction tool in the drilling string.
As is generally understood by those skilled in the art, in prior art downhole assemblies employing a similar motor, drilling fluid passes from a bore or passage above the motor (indicated in FIG. 1 at 12) and into the cavities defined between the rotor 25 and stator 20 to thereby activate the motor, and consequently drive any downhole tools coupled to the rotor. Any fluid passing through the motor enters the bore or passage downstream of the rotor (indicted in FIG. 1 at 42). In the particular example of FIG. 1, the drilling fluid then passes through the valve assembly 65, 70 in the valve housing 60, and into the passage 62 downstream of the valve assembly.
The flow of drilling fluid through the motor in part determines the rotation speed and horsepower of the motor, along with the particular lobe configuration of the motor. Thus, once a drilling string is assembled, the rotation speed and power of the motor can be changed only by varying the flow of drilling fluid, or else by retracting the drilling string from the bore hole, disassembling it, and reassembling it with a differently configured motor. However, it may not be desirable to vary the flow rate of the drilling fluid in this manner, and disassembling and reassembling a drilling string can consume several hours of labour.
Accordingly, in the illustrated examples, the motor assembly includes a bypass system which can be selectively activated or deactivated to control the flow of drilling fluid through the motor assembly. This can be better seen in FIG. 2, which provides an enlarged view of the motor assembly portion 100 of the cross-section of FIG. 1. The motor assembly includes the stator 20 and the rotor 25. The rotor 25 is provided with a through bore or passage 22 extending through the entire or a substantial part of the length of the body of the rotor 25. The passage 22, which may be circular in profile, permits fluid communication through a substantial part of the length of the rotor 25 from a first end having an inlet to a second end having an outlet. In this example, when the rotor 25 is in position in a downhole drilling string, the first end is uphole from the second end. The passage 22 can be circular in cross-section, but may have other configurations within the rotor body. At or near the second end of the rotor 25, one or more outlets 27 provide fluid communication from the passage 22 to other parts of the drilling string below. This second end may therefore be referred to as the outlet end. Since the rotor 25 may be connected to other components of the downhole assembly at its second or outlet end (e.g., by the universal joint connected to the driveshaft 45), the outlets 27 may be positioned above this connection.
A further component, a catch component 30 is mounted at the first end of the rotor 25. The catch 30 is configured to receive and retain a blocking implement. The blocking implement can be a substantially spherical ball or another shape configured to block passage through the catch 30 and/or rotor 25, as explained below. In the illustrated examples, the catch 30 is an insert mounted to the rotor using appropriate connectors, such as threaded joins; however, the catch 30 can alternatively be mounted using a separate connector element, not shown. In the illustrated examples, the catch 30 is configured to be inserted in the upper end of the rotor 25. As can be seen in FIG. 2, a connection end 38 of the catch 30 is received within an upper portion of the rotor 25. The connection end 38 terminates at an exterior shoulder 36, which is positioned proximate to the upper end of the rotor 25 when the catch 30 is installed in the rotor 25. When the catch 30 is installed, substantially all fluid is blocked from entering the passage 22 from the upper end of the rotor except through the catch 30. Thus, when the catch 30 is in place, fluid can pass into the catch 30, though the passage 22, and out through the one or more outlets 27. While the catch 30 is illustrated here as a distinct component from the rotor 25, in some implementations the catch 30 may be formed in a single piece with the rotor 25.
With reference to FIGS. 2-4, the catch 30 includes a receiving end 32, which is sized to fit within the surrounding housing and may have a substantially funnel shape to facilitate catching a blocking implement dropped down the drilling string. There may be sufficient clearance within the housing to permit drilling fluid to pass around the exterior of the receiving end 32 and the catch 30 and down towards cavities defined by the rotor 25 and stator 20 of the motor assembly 100. The receiving end 32 can be provided with slots or apertures 34 that also permit fluid entering the receiving end 32 to pass from the interior of the receiving end 32 to the exterior of the catch 30. Defined within the catch 30 is a bore or passage 35 of varying diameter, as will be discussed below. This passage 35 is in fluid communication with the passage 22 of the rotor when the catch 30 is installed in the rotor 25. Thus, the entire rotor assembly (consisting of an integrated catch and rotor, or an assembled catch and rotor) has a passage 35-22 permitting fluid to pass from the catch's receiving end 32 to the outlets 27 when the catch 30 is not blocked.
Within the catch 30, the diameter of the passage 35 varies from a dimension wide enough to receive a blocking implement, such as a ball 15 (shown in FIG. 1) caught by the receiving end 32 after it is dropped into the drilling string to direct the ball 15 towards an interior of the catch 30 and an interior seat 37, which in this example is an angled interior shoulder restricting the diameter of the passage 35 to a size that is smaller than the diameter of the ball 15. Thus, when the ball 15 is received on the seat 37, it substantially blocks fluid passage into the inlet end of the rotor 25 and through the passage 35 into the passage 22 of the rotor 25. It will be appreciated that by selectively placing a ball 15 on the seat 37, fluid passage through the motor assembly 100 can be controlled to thereby control the rotation and horsepower of the motor assembly 100, with or without varying the flow rate of the drilling fluid at the surface.
This is illustrated in greater detail in FIGS. 5-8. FIG. 5 is an enlarged view of the section A indicated in FIG. 1. When no ball 15 is seated in the catch 30, the catch 30 is in a non-engaged state. Drilling fluid can pass from the passage 12 in the drilling string above the catch 30 into the passage 35 of the catch 30, and through the passage 22 of rotor 30. All or a substantial amount of the drilling fluid will therefore bypass the cavities of the motor and exit the outlets 27 of the rotor 35, as illustrated in FIG. 6. While a small amount of drilling fluid may pass around the catch 30 or through the apertures 34 to the exterior of the catch 30 and enter the space defined by the rotor and stator of the motor, it may not be sufficient to activate the motor; or, if the motor is nevertheless activated, the torque generated by the motor may be significantly decreased or even substantially nil. Thus, even though drilling fluid is flowing through the downhole assembly, the torque may not be sufficient to activate a downhole component such that it has a significant effect. Thus, when the passage 35 is not blocked, the motor can be considered to be substantially inactive.
When a ball 15 or other blocking implement is dropped into position in the catch 30, as illustrated in FIG. 7, the catch 30 is in an engaged state. Fluid entering the downhole assembly is prevented from entering the passage 35, and is redirected towards the cavities of the motor as indicated by the arrows in FIGS. 7 and 8. A minimal amount of fluid, or no fluid, passes through passage 22. Consequently the flow rate of drilling fluid through the motor increases, thereby activating the motor or increasing the rotation and the torque of the motor.
The ball 15 or other blocking implement can be manufactured of a breakable material, such as Teflon®. When the ball 15 is in place as in FIG. 7 and the motor is active, the motor can be substantially stopped or slowed down by dropping a fracture implement (not shown), such as a smaller stainless steel ball, to shatter to the ball 15. The fragments of the ball 15 can be flushed out of the catch 30 and rotor passage 22 by the drilling fluid. If the fracture implement has a smaller diameter than the passage 35 and bore 22, it will pass through the motor assembly 100 without substantially blocking fluid flow therethrough.
In some implementations, a further bypass may be included in the catch 30, as illustrated in FIGS. 9 and 10. In this example, one or more bypass ports 39 are included below the receiving end 32, proximate to but above the motor cavities. Thus, even when a ball 15 is seated in the catch 30 as in FIG. 10, some fluid can still bypass the motor cavities, thus permitting the motor to run at a lower rate of rotation.
When the rotor assembly and motor is used in a friction tool, such as the example downhole assembly 10 illustrated in FIG. 1, the vibrations created by the friction tool are produced by the oscillation assembly component 13 due to variations in fluid pressure. The variations in fluid pressure can be generated by any suitable component driven by the rotor 25. In the assembly 10, the valve assembly 65-70 generates these variations. With reference to FIGS. 11, 12, and 13, each of the stationary valve component 70 and rotating valve component 65 include one or more ports 73a, 73b, etc. and 67a, 67b, 67c, etc., respectively. These ports may be arranged regularly or irregularly within their respective component, and may be identically or differently sized.
The rotating valve component 65 is connected to the rotor 25. When the motor is inactive, the rotating valve component 65 is substantially stationary, and fluid flows through the valve components 65, 70 to the extent permitted by the alignment of the ports of the two valve components 65, 70. When the motor is active, the rotating valve component 65 is driven by the rotor 25 and the ports 67a, 67b, 67c, etc. of the rotating valve component move into and out of alignment with the ports 73a, 73b, etc. of the stationary valve component 70. In the examples shown in the figures, an optional further wear component 80 with ports 83a, 83b corresponding to the ports of the stationary valve component 70 is included. As can be seen in FIGS. 12 and 13, depending on the relative position of the rotating valve component 65 to the stationary valve component 70, the fluid flow through the valve assembly can be restricted, or even blocked altogether. The intermittent alignment and non-alignment of the valve components 65 and 70 as the rotating valve component 65 rotates create variations in the fluid flow rate, and consequently variations in fluid pressure in the downhole assembly. The variations may be cyclical and repeating, or may be substantially arrhythmic, depending on the selected arrangement and sizing of the ports in the various components 65, 70 (and optionally wear component 80), and the pattern of rotation of the rotating valve component 65 produced by the rotor 25. These variations in fluid pressure activate the oscillation assembly 13, thereby inducing vibrations in the portion of the drilling string containing the downhole assembly 10.
As mentioned above, prior art friction tools or other tools are often driven by the flow of the drilling fluid. Consequently, control of the tool is accomplished by controlling the flow rate and pressure of drilling fluid into the tool; the tool may accordingly be stopped by halting the flow of drilling fluid. However, when drilling fluid is also required to operate the motor, it may be undesirable to simply stop pumping fluid downhole; this may halt the tool, but it will also halt the motor. For these reasons, with prior art friction tools, it is often necessary to halt drilling operations, pull the drilling string to the surface, disassemble the string, and reassemble the string to remove or add the tool, as the case may be. This activity can consume several hours of labour. Those skilled in the art will appreciate that with a downhole friction tool assembly 10 including the rotor assembly described above (i.e., the rotor 25 with integral passage 22 and catch 30), the drilling string including the downhole assembly 10 can be lowered into the well bore and drilling fluid can be pumped into the downhole assembly without engaging the catch 30 and activating the friction tool, until the operator chooses to activate the motor by dropping a ball or other blocking implement into the catch 30. In other words, the motor can be transitioned from an inactive to an active state while drilling fluid is flowing down the string without substantially varying the flow of drilling fluid entering the downhole assembly, and without pulling the drilling string to surface to add in a friction tool.
It will be appreciated that in some implementations, when the valve assembly is at rest with the rotating valve component 65 relatively stationary with respect to the stationary component 70, the ports of these components may be aligned in a manner that substantially restricts or blocks drilling fluid flow through the valve assembly and down to other lower portions of the drilling string. It may also or alternatively be desirable to delay the pressure-varying effect of the valve assembly even when the motor is active. Thus, in some embodiments, a temporary spacer ring 85 is included in the valve assembly, as shown in FIGS. 14 and 15, to temporarily permit drilling fluid flow though the valve assembly regardless of the relative orientation of the rotating valve component 65 to the stationary component 70. The temporary spacer ring 85 separates the two valve components 65, 70, supporting the rotating valve component 65 above the stationary valve component 70. Because the components 65, 70 are separated, all the fluid passing through the ports 67a, 67b, 67c of the rotating valve component 65 can enter the ports 73a, 73b of the stationary valve component 70 without the intermittent restrictions caused by the ports entering into and out of alignment with each other, and without causing substantial variations in fluid pressure. The spacer ring 85 is manufactured of a material such as aluminum, brass, bronze, cement, and the like, that can break down as the rotating valve component 65 rotates against the spacer ring 85. The valve components 70, 65 are typically manufactured of a high strength carbide material that reaches high temperatures during operation.
While the motor of the downhole assembly 10 is inactive, drilling fluid can flow through the passage 22 of the rotor 25, and down to the valve assembly where it will pass through the ports of the rotating valve component 65, the space defined by the spacer ring, and the ports of the stationary valve component 70, without restriction caused by interference of the rotating valve component 65 with the ports of the stationary valve component 70 or vice versa. When the motor of the drilling assembly is activated as described above, the rotor 25 begins driving the rotating valve component 65. The component 65 rotates against the spacer ring 85 within the valve housing and begins to generate heat and friction against the spacer ring, which will wear down the spacer ring 85. The worn portions of the spacer ring 85 will be flushed by the drilling fluid through the stationary valve component 70, until the spacer ring 85 is effectively destroyed and no longer separates the stationary valve component 70 from the rotating valve component 65. At that stage, the valve assembly operates as originally intended to intermittently restrict fluid flow and vary fluid pressure. By selecting the material and depth of the spacing ring 85, the valve assembly and any tool driven by the valve assembly can be selectively disabled for a desired period of time during initial drilling operations. The spacer ring 85 may be used without the catch 30 described above.
It will be appreciated by those skilled in the art, however, that the spacer ring 85 is effectively a one-time use solution for use the first time the motor is activated and begins driving the rotating valve component 65. The spacer ring's effectiveness in maintaining a separation between the rotating valve component 65 and the stationary valve component 70 for a desired period of time from the time the rotating valve component 65 starts rotating depends on the durability of the spacer ring 85 construction.
FIGS. 16-22B illustrate a further embodiment of the assembly 10, indicated in FIG. 16 as 10′, with similar components (including valve assembly 65-70) but also including a thrust transmission assembly that can be used to selectively engage a downstream tool. The assembly 10′ includes the adapted rotor 25 described with reference to FIGS. 1-2 including the catch 30, but also includes, disposed between the rotor 25 and the valve assembly 65-70, a thrust transmission assembly comprising a thrust unit 110, hanger 120, and spring unit 130. As can be seen more clearly in FIG. 17, the thrust unit 110 is mounted in fixed relation to the rotor 25 and/or driveshaft 45; in this example, the thrust unit 110 is supported by the driveshaft 45 and retained in place by means of an inwardly-projecting lip 116 (indicated more clearly in FIG. 19) between a shoulder 46 on the driveshaft 45 and the rotor 25. The thrust unit 110 therefore moves axially with the rotor 25 and driveshaft 45. The hanger 120 is not mechanically attached to the rotor 25, driveshaft 45, or thrust unit 110, but is disposed in the downhole assembly below the thrust unit 110, and supported by the spring unit 130. The hanger 120 is a structure that effectively surrounds a portion of the driveshaft 45 and permits fluid passage from an exterior to an interior of the hanger 120, while also transmitting thrust from an upper component (in this case the thrust unit) to a lower component (the spring unit 130). While the hanger 120 and thrust unit 110 are not connected, the lower face of the thrust unit 110 (the bottom bearing surface 118 indicated in FIGS. 18-19) may contact hanger 120 on the hanger's upper face 124 (indicated in FIGS. 20-21). This permits the bottom bearing surface of the thrust unit 110 to move with respect to upper face of the hanger 120, thus allowing for rotor run-out during motor operation.
The spring unit 130, in turn, is mounted in fixed relation to the housing of the downhole assembly between the hanger 120 and a spacer component 140. In the example of FIGS. 16-17, the thrust transmission assembly and spacer component 140 are provided within the shaft housing 40, which houses the driveshaft 45. The interior of the shaft housing 40 includes a connector (e.g. a threaded connector) for connecting to an exterior of the adjacent valve housing 60. The upper end 61 of the valve housing 60, which lies on the interior of the shaft housing 40, provides an internal shoulder at its upper end to abut the spacer component 140 at a lower end of the spacer component 140. An upper end of the spacer component 140 supports a lower end of the spring unit 130, by which means the spring unit 130 is retained in a substantially fixed position with respect to the shaft and valve housings 40, 60. The length of the spacer component 140 can be selected according to the length of the shaft housing 40 to ensure that contact can be made between the thrust unit 110 and hanger 120 in all operational states of the assembly 10′ (e.g., with or without drilling fluid flow). However, it will be appreciated by those skilled in the art that other means for retaining the spring unit 130 in fixed relation to the housing components of the assembly 10′ may be provided instead, such as an interior abutment in the shaft housing 40, which may not require the use of the spacer component 140.
The spring unit 130 can comprise a suitable coil compression spring disposed between the interior of the housing 40 and the driveshaft 45. Other spring assemblies known to those skilled in the art (e.g., an assembly comprising Belleville washers) may be used in place of the illustrated coil spring. The spring unit 130 is selected such that when it is subject to a first amount of downward force due primarily to the weight of the hanger 120 and the drilling string components exerting downward force on the hanger 120 (e.g., rotor 25, thrust unit 110, driveshaft 45 attached to the rotor 45, and any downstream components mounted to the driveshaft 45 such as the rotating valve component 65), the spring unit 130 sufficiently supports the hanger 120, thrust unit 110, and driveshaft 45, so the rotating valve component 65 is spaced from the stationary valve component 70. In this manner, the rotating valve component 65 is effectively suspended or hanging above the stationary valve component 70 as a result of the hanger 120 and other components supported by the spring unit 130. As can be seen in FIG. 17, a gap or passage 142 is defined within the valve assembly 65, 70 due to the elevation of the rotating valve component 65 above the stationary component 70. The valve assembly 65, 70 may thus be considered to be in an unengaged state when the rotating valve component 65 is thus elevated. This state is analogous to the state of the valve assembly 65, 70 when the spacer 85 is in place between the rotating valve component 65 and stationary valve component 70 as described above; when drilling fluid flows through the passage 22 of the rotor 25, it enters the valve assembly where it will pass through the ports of the rotating valve component 65, the gap 142, and the ports of the stationary valve component 70, without restriction caused by interference of the rotating valve component 65 with the ports of the stationary valve component 70 or vice versa.
The thrust unit 110 is illustrated in detail in FIGS. 18 and 19. The thrust unit 110 comprises a substantially hollow body having an upper surface 114, a lower bearing surface 118, a wall 117, and an interior bore 115. The interior bore 115 is sized to admit passage of the driveshaft 45, as illustrated in FIGS. 16 and 17. Connection means are provided on the thrust unit 110 to maintain this component in fixed relation to the rotor 25 and/or driveshaft 45 (the latter being coupled to the rotor 25). The connection means may be provided by mating threaded connectors on the washer 110 and the corresponding component 25 or 45, although in this example, an inwardly-projecting lip 116 extends from the wall 117 and fits over a corresponding shoulder 46 in the driveshaft 45, as indicated in FIG. 17. During assembly of the drilling string, the thrust unit 110 can be placed on the driveshaft 45 prior to connecting the driveshaft 45 to the rotor 25. The exterior dimensions of the thrust unit 110 provide sufficient clearance between the exterior of the thrust unit 110 and the housing containing the thrust transmission assembly to permit sufficient radial or sideways movement of the thrust unit 110 to as to avoid restricting motor run-out. Sufficient clearance is also provided to permit drilling fluid flow from the motor section of the string over the exterior of the thrust unit 110, and into the inlets of the hanger 120, described below. The thrust unit is generally smaller in diameter than the hanger 120.
The hanger 120, illustrated in FIGS. 20 and 21, comprises a substantially hollow body having an upper surface 124, a lower surface 128, a wall (indicated at 125 and 127), and an interior bore 122 to permit passage of both the driveshaft 45 and drilling fluid. One or more inlets 126 are provided in an upper portion of the wall 125 to permit passage of drilling fluid from the exterior of the hanger 120 to its interior bore 122. The interior bore 122 directs the fluid to other portion of the drilling string. The upper portion of the wall 125 in this example is generally frustoconical in shape, increasing in diameter between the upper face 124 and the lower portion of the wall 127, to permit sufficient clearance for drilling fluid into the inlets 126. The lower portion of the wall 127 is dimensioned to fit within the housing 40, while permitting the hanger 120 to slide up and down within the housing 40. The hanger 120 may be configured to retain O-ring seals to seal the exterior of the hanger 120 against the interior of the drilling string.
As described above, the hanger 120 is mounted between the thrust bearing 110 and the spring unit 130. The upper surface 124 of the hanger 120 contacts the lower bearing surface of the thrust unit 110, but the hanger 120 and the thrust unit 110 are not attached to each other.
The exterior dimensions of the thrust unit 110 and the hanger 120 are dimensioned to permit passage of drilling fluid from the motor section of the drilling string (whether from the cavities defined by the rotor and stator 25, 20 or outlets 27 in the rotor 25), over the exterior of the thrust unit 110 (indicated in FIG. 17 as passage 122) and into the inlets 126 of the hanger 120, into interior bore 122 of the hanger 120. The interior bore 122 is, in turn, dimensioned to permit passage of the driveshaft 45 up and down through the hanger 120, while also permitting passage of drilling fluid down towards the valve assembly 65-70.
In operation, drilling fluid can pass from the motor section of the drilling string to the friction tool or other tool downstream of the thrust transmission assembly, but the amount of thrust transmitted by the thrust transmission assembly is determined by the path followed by the drilling fluid through the motor section. The drilling fluid path, in turn, can be selectively controlled through use of the catch 30, as illustrated in FIGS. 5-8. FIG. 22A illustrates drilling fluid flow in the assembly 10′ when the catch is not engaged, as in the example of FIGS. 5 and 6. As discussed above, without a blocking implement seated in the catch 30, drilling fluid can pass through the passage 35 of the catch 30, then through the bore 22 and outlets 27 of the rotor 25, as indicated by the upper arrows in FIG. 22A. The drilling fluid then passes through over the thrust bearing 110 through passage 112, and through the slots of the hanger 120 into the interior bore 122, between the wall of the hanger 120 and the driveshaft 45. Continuing to follow the arrows of FIG. 22A, the drilling fluid then passes through the spring unit 130, and down towards the valve assembly 65-70.
As discussed above, when the spring unit 130 is subject to only a first amount of force due primarily to the weight of the hanger 120 and drilling string components whose weight is borne by the hanger 120, the spring unit 130 supports the hanger 120, and consequently the thrust unit 110 and driveshaft 45, at a height that defines a gap 142 between the stationary and rotating valve components 70, 65 of the downstream tool assembly. It will be appreciated by those skilled in the art that the flow of drilling fluid as illustrated in FIG. 22A can result in an incidental downward force on the thrust unit 110 and other components as well; however, the spring unit 130 is selected such that the gap 142 is present even under the additional force supplied by the downward flow of the drilling fluid. Because the gap 142 is present, fluid passing down from the motor section of the drilling string can then pass through any ports 67a, 67b etc. of the rotating valve component 65 without being substantially obstructed by the alignment of the rotating valve component ports with the ports 73a, etc. of the stationary valve component 70, and little or no change will result to the fluid pressure downstream of the valve assembly 65-70.
When a blocking implement 15 is engaged in the catch 30, as illustrated in FIGS. 7 and 8, drilling fluid flow through the bore 22 of the rotor 25 is substantially blocked, resulting in most or all fluid being diverted through the motor and generating torque, as discussed above. FIG. 22B illustrates the flow of drilling fluid exiting the motor section of the assembly 10′. As indicated by the arrows, drilling fluid exits the cavities of the motor and passes through the passage 112 over the thrust unit 110, and through the inlets of the hanger 120 to enter the passage 122 within the hanger 120. The torque produced by the motor is transmitted via the driveshaft 45 to rotate the rotating valve component 65. However, due to blockage of the bore 22 in the rotor 25, the drilling fluid also exerts more downward pressure on the rotor 25, and consequently on the driveshaft 45 and thrust unit 110. The lower surface 118 (as shown in FIGS. 18-19) of the thrust unit 110 bears on the upper surface 124 (as shown in FIGS. 20-21) of the hanger 120. The hanger 120 in turn bears on the spring unit 130, which is thus subject to a second amount of force greater than the first amount of force mentioned above. The spring unit 130 consequently compresses, reducing the height of the passage 142 until the rotating valve component 65 engages the stationary valve component 70. The valve components 65, 70 thus being engaged and the rotating valve component 65 now rotating, the valve assembly operates to intermittently restrict flow of drilling fluid through the corresponding ports of the rotating and stationary valve components 65, 70 as described above. If the second amount of force is removed (e.g., if the fluid pressure above the rotor 25 is reduced, for example due to removal of the blocking implement 15), the spring unit 130 can relax to some degree, thus raising the hanger 120, thrust unit 110 and driveshaft 45 and creating the gap 142 between the valve components 65, 70.
Since the valve components 65, 70 are only engaged once a blocking implement 15 has been seated in the catch 30, the operator can run the drilling string with full drilling fluid flow for any desired duration without activating the friction tool or other tool controlled by the valve assembly 65, 70. The tool can be activated by dropping the blocking implement 15 into the catch 30. As described above, if a durable blocking implement 15 is used, the tool will continue to operate until the blocking implement is withdrawn from the assembly 10′, which may involve bringing the assembly 10′ to the surface; but if a breakable blocking implement 15 is used, the tool can be deactivated while still downhole by breaking the blocking implement 15 with a fracture implement. The thrust transmission assembly, together with the catch 30 and rotor 25, thus provide a reusable mechanism for selectively engaging and disengaging a downstream valve assembly, friction tool, or other assembly in the drilling string. The thrust transmission assembly provides the initial spacing between the rotating and stationary valve components 65, 70 like the spacer ring 85, but with the advantage that the thrust transmission assembly is reusable and need not be replaced each time the benefit of the thrust transmission assembly is desired.
As can be seen most clearly in FIG. 16, the overall load-bearing surface area at the top of the motor section provided by the combination of the rotor 25 and ball catch is relatively smaller than the surface area of the rotating valve component 65. Thus, the catch 30 and thrust transmission assembly operate to reduce the load from the rotating valve component 65 on the upper face of the stationary component 70 even when the components 65, 70 are engaged, reducing the rate of wear on the stationary component 70 and rotating valve component 65.
It will be appreciated by those skilled in the art that while the example of FIGS. 16-22B was described with reference to the flow-varying valve assembly 65, 70 shown in the illustrations, the thrust transmission assembly can also be used to provide for selective engagement of two or more downhole components, where one of the components can be moved into and out of engagement with another through motion in an axial direction.
Throughout the specification, terms such as “may” and “can” are used interchangeably and use of any particular term should not be construed as limiting the scope or requiring experimentation to implement the claimed subject matter or embodiments described herein. Various embodiments of the present invention or inventions having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention(s). The inventions contemplated herein are not intended to be limited to the specific examples set out in this description. For example, where appropriate, specific components may be arranged in a different order than set out in these examples, or even omitted or substituted. The inventions include all such variations and modifications as fall within the scope of the appended claims.
Patent Grant
10619437
