Patent Application
20160024848
The present invention relates to the field of oil and gas exploration, and in particular downhole activities, such as, for example, drilling, logging, fishing, completions, etc. More specifically, the present invention is a drive arrangement suitable for various uses, such as, for example, driving a component of a Bottom Hole Assembly (BHA) including, but not limited to, a directional drilling tool.
When drilling wellbores for oil and gas production, a drill-string is used which includes various components, such as the drill-bit, BHA and, in some cases, a drill-pipe rotatable by a topmotor at surface which in turn rotates the BHA, typically, during straight drilling. In other cases, coiled tubing is used, a continuous length of pipe wound on a spool which, typically, cannot rotate about its own axis. A work-string is used within a completed or nearly completed well-bore and includes a tubing string used to convey a treatment or equipment for well service activities. Components of these and similar arrangements for downhole activities may be required to rotate around a central axis. The drill-bit, for example, must usually rotate in order that it abrades the seabed to form the well-bore. The rotation may be the whole of the arrangement or it may be the case, for example, where coiled tubing is used, that the arrangement provides for rotation of only part of the work or a drill-string, or that different sections rotate independently, at different angular velocities and/or with different torques being exerted, or it may be advantageous that only part of the work or a drill-string rotates.
In directional drilling, the BHA typically includes a bent portion near the drill bit. Such a BHA typically includes a bent portion or a bent sub. The bent portion points in a direction slightly different from the axis of the rest of the drillstring including the drill bit. In order to allow the bit to drill in the direction the bent portion points, the drill bit is rotated, typically, by a downhole motor located within the BHA, while the drillstring above the bit and the bent portion do not rotate. The downhole motor is typically a mud motor, also referred to as a Positive Displacement Motor (PDM), driven by the flow of mud inside the drillstring.
In drill pipe drilling, where the drill pipe is rotatable by a topmotor at surface, once a particular wellbore direction has been achieved, the entire drillstring, including the drill pipe and the bent portion are rotated as one piece from surface. This allows the drilling to continue along a straight path with greater speed and torque because the rotations of the mud motor and the topmotor add at the drill bit. The rotation of the bent portion results in a slight enlargement of the wellbore diameter. However, since the bend angle between the drillstring axis and the axis of the bent portion typically lies in the region between 0°-3° and the bent portion is located close to the bit, such an enlargement is negligibly small. When a change in direction is required, the drill string can be rotated slowly to point the bent portion in the required direction downhole.
In conventional coiled tubing directional drilling, the coiled tubing cannot be rotated and thus it is generally not possible to obtain a straight wellbore while drilling with a bent sub. A straight drilling direction is typically achieved by alternately drilling in one direction first, then orienting the bent portion, e.g. by using a mud flow driven actuator, to point in opposite direction and then drilling in the second direction. Such drilling results in a wavy wellbore which generally follows a straight line.
A number of problems exist related to relative rotation of drillstring or workstring components downhole.
One problem associated with the use of a bent sub, regardless whether drill pipe or coiled tubing is used, is that adjustment of the angle of the bend, and consequently, the amount of deviation of the drilling direction from a straight path, invariably must be carried out manually at the surface. This means that the drilling process needs to be stopped and the entire drillstring must be pulled out to the surface and then inserted back into the wellbore. In an arrangement described in U.S. Pat. No. 4,836,303, the bend angle can be remotely adjusted downhole, thereby avoiding the need for the drillstring to be recovered to the surface for adjustment of the bend. However, the drilling operation still has to be halted and the drillstring lifted off-bottom in order for the orientation of the bent sub to be adjusted, thereby still involving a significant amount of non-drilling time (NDT) in any drilling operation. Furthermore, starting and stopping the drilling operation can result in a stuck pipe. Moreover, stopping and starting circulation of the drilling fluid, which interrupts the removal of cuttings and the cleaning of the borehole, can increase the risk of stuck pipe occurrence.
Another problem associated with the use of a bent sub in directional drilling is caused by the fact that that during directional drilling, the drill bit is rotated downhole by the mud motor whereas the drillstring including the bent sub above the bit do not rotate. The drillstring and the bent sub thus slide in the wellbore as the drill bit is advancing in the direction determined by the bent sub. Slide-drilling, along with low rate of penetration, also brings along friction problems between the drillstring and the wellbore walls, including the risk of a stuck drillstring. US 2004/0079552 attempted to address this problem in drill pipe drilling by providing a BHA with an offsetting arrangement to provide a deviation from a straight path and by connecting the drill pipe directly to the bit, dispensing with the need for a mud motor. This allows the drill pipe to rotate during directional drilling, while the BHA housing does not rotate. However, this is achieved at the expense of not being able to drill along a straight path. Furthermore, this arrangement is inherently not suitable for coiled tubing drilling. And yet furthermore, the bend angle still has to be set at surface.
A further problem in directional drilling, whether using drill pipe or coiled tubing, is caused by reactive torque created by the drilling fluid hitting against the stator (which is typically the motor housing) of the downhole motor. Since the stator constitutes the body of the motor and comprises part of the BHA housing, the reactive torque twists the motor together with the BHA anticlockwise. The reactive torque at the motor housing is equal to the active drilling torque at the bit. Reactive torque causes a problem during directional drilling because the twisting of the BHA caused by reactive torque changes the toolface orientation of the bent sub over time. Reactive torque which exceeds a certain threshold (over torque) is dangerous as the twisting of the drillstring results in stresses which can lead to damage or sticking of the drillstring. Furthermore, sticking of drillstring causes highly variable RPM and drillstring torque transmitted to the BHA. This torque is reacted by the BHA, which can result in difficulty in maintaining drilling direction in directional and horizontal wells.
A still further problem associated with drill pipe drilling is that rotation of the drill pipe can result in drill string components, including the BHA experiencing excessive torque from surface rotation, which can be damaging to the drill string joints and the components of the BHA.
Some further examples of downhole activities where rotating components are involved and where problems exist related to aspects of relative rotation of components of downhole tools include:
It is an aim of the present invention to obviate or mitigate one or more of the disadvantages associated with existing downhole tools.
Accordingly, the present invention provides a downhole tool assembly, comprising:
Preferably, the remaining one of the wave generator, flexible gear and outer gear is adapted to function as a stationary component of the harmonic drive.
The downhole tool arrangement preferably includes a Bottom Hole Assembly (BHA) wherein at least one of the first and second bodies is included in the BHA. The downhole tool assembly preferably forms part of a drill-string or work-string.
A harmonic drive is a special type of drive and typically comprises a wave generator (typically an elliptical hub or cam sometimes also referred to as an oval bearing), an intermediate gear, aka a flexible gear, and an outer gear, commonly referred to as a circular gear. Typically, in a harmonic drive, when the outer gear is fixed, the wave generator and the flexible gear rotate in opposite directions; when the flexible gear is fixed, the outer gear and the wave generator rotate in the same direction; and when the wave generator is fixed, the outer gear and the flexible gear rotate in the same direction. Arrangements are possible where all the three components of the harmonic drive rotate so that the harmonic drive functions as a differential. Due to its unique principle of construction, a harmonic drive provides very high or very low, depending on what is used as an input, transmission ratios (typical ratios include 100:1, 200:1, 300:1 or vice versa etc.) along with high torque transmission (due to a plurality of teeth meshing at the same time), torque multiplication (or reduction depending on what is used as an input), very compact construction, rotation precision, low vibration and absence of backlash. Since harmonic drives are known, it is not necessary to describe its construction and operation in detail.
Preferably, the first and the second bodies have a common axis of rotation.
The motor preferably comprises a rotor component for driving the component of the downhole tool assembly and a stator component wherein the rotary input component of the harmonic drive is arranged in a couplable relationship with the motor so as to transmit rotation from the motor via the harmonic drive to the rotary output component of the harmonic drive.
In one arrangement, the rotary input component of the harmonic drive is arranged in a couplable relationship with the rotor component of the motor so as to transmit rotation of the rotor component of the motor via the harmonic drive to the rotary output component of the harmonic drive.
In another arrangement, the rotary input component of the harmonic drive is arranged in a couplable relationship with the stator component of the motor so as to permit the stator component of the motor to rotate under the influence of reactive torque acting on the stator component during rotation of the rotor component of the motor.
In one arrangement, a pair of harmonic drives is provided, wherein in a first harmonic drive the rotary input component is arranged in a couplable relationship with the rotor component of the motor so as to transmit rotation of the rotor component of the motor via the harmonic drive to the rotary output component of the harmonic drive, and wherein the rotary input component of the second harmonic drive is arranged in a couplable relationship with the stator component of the motor so as to permit the stator component of the motor to rotate under the influence of reactive torque acting on the stator component during rotation of the rotor component of the motor and, preferably, wherein the first harmonic drive is incorporated into the rotary output component of the second harmonic drive so that when the rotary output component of the second harmonic drive is rotated, the first harmonic drive rotates as a unit with the rotary output component of the second harmonic drive in the direction opposite to the direction of rotation of the rotary output component of the first harmonic drive. In this arrangement, rotation of the rotary output component of the first harmonic drive in opposite directions is made possible.
In one arrangement, one of the first and second bodies comprises one of the rotor component or the stator component of the motor.
In one arrangement, the motor is a downhole motor for rotating a component of the downhole tool, such as for example a drill bit. The downhole motor is preferably arranged in a power section of the BHA of the downhole tool assembly and wherein the rotor component of the motor comprises a motor shaft extending substantially coaxially with the rotation axis of the first body relative to the second body and the stator component comprises a tubular motor housing wherein the housing encloses the motor shaft. The down hole motor may comprise a mud motor, but it will be appreciated that alternative types of downhole motor can be utilised, e.g. a turbine motor. The motor shaft is preferably connected to an end component, which can be a drill bit or some other tool.
In another case, the motor comprises a topmotor at surface wherein the rotor component of the motor comprises a drill pipe extending between the BHA and the topmotor. Preferably, the harmonic drive is coupled to the drill pipe at the rotary input component and to the second body at the rotary output component. Where drill pipe is used, the downhole tool assembly preferably comprises a second motor in the form of a downhole motor.
The present invention is usable with either drill pipe or coiled tubing. Thus, in one arrangement, the first body comprises a drill pipe rotatable by a topmotor. In another arrangement, the first body comprises non-rotatable coiled tubing. In either of the above arrangements, i.e. where the first body comprises a drill pipe or coiled tubing, the second body preferably comprises a rotatable component of a BHA.
Thus, in one arrangement, the harmonic drive can be connected between the motor shaft of downhole motor and the rotatable component of the BHA, e.g. a bent portion or a bent sub, so as to utilise the active torque of the downhole motor to rotate the rotatable component of the BHA with considerable reduction, e.g. in order to orient a bent sub. Rotation in opposite direction can be achieved by coupling the harmonic drive to the stator component of the downhole motor and coupling the stator component to the rotatable component of the BHA and utilising the reactive torque acting on the stator component to rotate the rotatable component of the BHA.
In another arrangement, the harmonic drive is coupled between a drill pipe and a rotatable component of the BHA, e.g. a bent portion or a bent sub, wherein rotation of the drill pipe is transmitted to the rotatable component of the BHA with considerable reduction, e.g. in order to orient a bent sub or to allow the bent sub to rotate constantly but considerably slower than the drill pipe. In the latter case, the drill pipe can thus rotate during directional drilling and thereby slide drilling can be avoided while the bent portion remains non-rotating or rotates so slowly that the effect of this rotation on the drilling direction is negligibly small. Furthermore, the harmonic drive of the present invention can be equipped with a clutch arrangement, as specified in more detail below, for selective interruption of the rotary connection between the drill pipe and the BHA, e.g. in case of excessive torque exerted on the BHA by the drill pipe. The clutch arrangement is also preferably adapted to selectively lock the harmonic drive between the drill pipe and the BHA so that the drill pipe and the BHA rotate as one piece thereby providing for the possibility of drilling straight. The clutch arrangement is also preferably adapted to alter connection sequence between the motor, the wave generator, the flexible gear, the outer gear and the first or the second body of the BHA so that the first or the second body can be rotated in opposite directions.
In one arrangement, the harmonic drive is coupled between the motor and the first or the second body of the BHA, so that the first or the second body of the BHA is coupled with either the flexible gear or the outer gear so that the first or the second body can be rotated in the desired direction, or a clutch means is provided enabling first or the second body to be selectively coupled with either the outer gear or the flexible gear, so that the first or the second body can be rotated in opposite directions.
In one arrangement, the outer gear is provided in the form of a stabiliser mounted around an outer circumference of the downhole tool assembly. In one arrangement, the stabiliser is a non-rotating stabiliser.
In one arrangement, the outer gear is adapted to function as a stationary component in the harmonic drive. Preferably, the outer gear is configured so that it remains stationary in a borehole due to friction between the outer gear and a wall of the borehole while one of the flexible gear or, preferably, the wave generator functions as the rotary input component. However, the friction can be overcome when the outer gear is coupled to the motor to be rotated by the motor and the harmonic drive is locked to rotate as a unit together with the motor. In one arrangement, the outer gear can be provided with a device, e. g. a flywheel, which prevents rotation of the outer gear in the direction opposite to the rotation of the outer gear when it is coupled to the motor and the harmonic drive is locked to rotate as a unit together with the motor, when the outer gear is required to remain stationary during, the operation of the harmonic drive, and permits rotation of the outer gear when the outer gear is coupled to the motor and the harmonic drive is locked to rotate as a unit together with the motor. For example, the direction opposite to the rotation of the outer gear when it is coupled to the motor and the harmonic drive is locked to rotate as a unit together with the motor, when the outer gear is required to remain stationary during the operation of the harmonic drive is a direction of reactive torque acting on the outer gear from a stator component of the motor, when the rotary input component of the harmonic drive is arranged in a couplable relationship with the stator component of the motor so as to permit the stator component of the motor to rotate under the influence of reactive torque acting on the stator component during rotation of the rotor component of the motor.
In one embodiment, the BHA is an orienting sub in which the relative rotation between the first body and the second body results in the change of orientation of one of the two bodies with regard to the other. This change in the orientation can be angular, i.e. a change in the rotational angle between the first and second bodies due to relative rotation of the first and second bodies about a common axis or longitudinal, i.e. involving a change in the angle between longitudinal axes of the first and the second bodies.
In a preferred arrangement, the BHA comprises a bent sub or a bent portion wherein the second body of the downhole tool assembly comprises the bent portion. The bent portion has an axis positioned at an angle to a central axis of the downhole tool assembly, wherein rotation of the bent portion around the central axis of the downhole tool assembly results in a change of circumferential orientation of the bent sub, and thus in the eventual direction of advancement of the downhole tool. The bent portion is preferably provided in the form of a bent housing rotatable about the central axis of the downhole tool assembly.
The bent portion or the bent sub may be arranged so that the bend angle in relation to the central axis of the downhole tool assembly can be adjusted downhole. This is achieved, preferably, by providing a bent portion comprising first and second bend members, wherein the first bend member is co-axial with the central axis of the downhole tool assembly, and the second bend member is rotatably coupled to the first bend member and rotatable relative thereto about a second axis of rotation which is at a non-zero angle relative to the central axis whereby the relative rotation of the first and second bend members results in the change in the bend angle between the bent portion and the central axis and wherein the first and second bend members are arranged to rotate relative to each other by a harmonic drive according the aspects described above.
Preferably, the harmonic drive comprises at least one clutch arranged so as to selectively vary the transmission of rotation between the harmonic drive and the motor, so as for example to disable the transmission or enable transmission of rotation with or without reduction and/or so as to change the direction of rotation at the output.
The clutch may be selected from many suitable types, including conical clutches, freewheels, viscous coupling, Hele-Shaw clutches, fluid drive, wet multi-plate clutch, epicyclical planetary gear system, wet clutch, magnetic inductance and other suitable.
Preferably, actuating means is provided for actuating the clutch, which can be provided in any suitable form, including a motor actuator, such as, for example, an electric actuator, pressure differential actuator (e.g. a spring), weight-on-bit (WOB) actuation, flow rate or flow pulse operated actuator.
A clutch may be adapted to selectively alternately cooperate with one or more of the wave generator, the flexible gear and the outer gear so as to enable or restrict rotation of that gear and so as to permit or restrict rotation of another gear, thereby enabling the change in the direction of rotation to occur between the first and the second body. The clutch can be active or passive, i.e. adapted to be activated/deactivated conditionally, e.g. when a certain condition is met. For example, a passive clutch can be provided between the harmonic drive and the BHA, the clutch being operable so that when torque exerted on the BHA from the drill pipe exceeds predetermined value, the clutch is activated and the rotary connection between the drill pipe and the BHA is interrupted so that the drill pipe can continue to rotate without exerting torque on the BHA.
Each of the first and second bodies preferably comprises a longitudinal axis. In a preferred embodiment, the longitudinal axes are collinear. Also, in a preferred embodiment, the longitudinal axes coincide with the mutual rotational axis of the bodies.
In a further advantageous variation, the harmonic drive may include one or more additional sets of an wave generator, a flexible gear and an outer gear, wherein the additional set of gears is linked to the existing set of gears so that the transmission ratio of the harmonic drive is a product of the transmission ratios of the existing and the additional sets. The provision of an additional gear set enables the transmission ratio of the harmonic drive to be set within a wide range of ratios, wherein each such ratio provides for a high level of precision in moving the first body in relation to the second body. For example, by providing a high reduction ratio between (such as the order of 1/100 or 1/10000 and so on) it is possible to rotate a rotatable component of a BHA very slowly, sufficiently slow so that the relative positions of the first and second bodies can be adjusted with high level of accuracy, or to make the rotation so slow that it can be regarded as non existent, where it is necessary to restrict the rotation of one of the two bodies while allowing the other body to rotate. In such an arrangement however, output torque is considerably higher than in a single-step harmonic drive and it is thus preferred to provide a torque limiting device at the output of the harmonic drive in order to prevent components of the downhole assembly from becoming damaged due to excessive torque.
In one arrangement, where a drill pipe is used in combination with a downhole motor and a bent sub, the harmonic drive is located above the downhole motor, but within the BHA and is connected between the drill pipe and a bent portion of the BHA so as selectively to permit the rotation of the drill pipe from surface above the harmonic drive while minimising or preventing altogether rotation of the bent portion. This is achieved by carefully selecting the reduction ratio of the harmonic drive such that the resulting rotation of the bent sub is negligibly slow compared with the rotation of the drill pipe that it can be regarded as non-existent. Such an arrangement enables directional drilling in the preset direction (i.e. when orientation of the bent sub is fixed and the bent portion slides as the bit is being rotated) with the drilling action powered by the downhole motor within the BHA and at the same time permits the drill pipe to be rotated by the topmotor above the bent portion. This arrangement eliminates the need to stop surface rotation of the drill pipe during directional drilling thereby minimising considerably friction problems in directional drilling.
The provision of a harmonic drive for rotating components of a downhole tool eliminates the need for a separate actuator motor. Instead, the harmonic drive uses the power of the primary motor (i.e. a topmotor or a downhole motor) of the downhole tool thereby reducing power consumption. A further effect of this arrangement is that it is not necessary to stop drilling or other downhole activity in order to adjust the tool orientation as the adjustment can now be done simultaneously with the drilling or the other activity while the primary motor is in operation. The considerable reduction ratio provided by the harmonic drive provides for a high precision in the adjustment of the orientation of the tool and requires low torque for functioning or the possibility to slow down the rotation of a bent portion of a bent sub to a negligible level during directional drilling so that the drill pipe upstring the bent sub can rotate at the same speed as the topmotor whereas the bent portion slides thereby setting the required drilling direction for the BHA. Furthermore, a harmonic drive has an inherently compact configuration and fits coaxially around a main longitudinal axis of the tool, thus making it easier to manufacture and assemble the tool compared to a tool with a separate actuator motor which is typically offset from the longitudinal axis of the drilling tool and thus requires asymmetric linkage components to be used to connect a drive shaft of the actuator motor with the rotating components of the sub.
In one arrangement, the rotatable component of the motor comprises an eccentric drive shaft of a downhole motor and the rotary input component of the harmonic drive is coupled directly to the eccentric drive shaft. The advantage of this arrangement over coupling to the motor shaft of the downhole motor is that this reduces the overall length of the tool.
According to a second aspect of the present invention there is provided a directional drilling tool, comprising:
The drilling tool may further comprise a remote control system having an operator control interface which may include a graphical display means indicating the path of the tool.
Further preferably, the drilling tool comprises a measuring device, for example a measurement while drilling (MWD) tool installed, preferably, below the swivel section and, ideally, above the power section. The MWD tool serves to read and measure drilling parameters. The BHA may also comprise a logging-while-drilling (LWD) tool in place of or in addition to MWD.
Embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention and vice versa.
According to a third aspect of the invention there is provided a directional drilling system, comprising:
Each of the swivel and adjustable bend sections may further comprise one or more positional sensors adapted to communicate the rotational position of the swivel and adjustable bend sections to the controller.
Embodiments of the third aspect of the present invention may comprise one or more features of the first or second aspect of the present invention and vice versa.
According to a fourth aspect of the invention, there is provided a downhole tool assembly, comprising:
Embodiments of the fourth aspect of the present invention may comprise one or more features of the first, second and third aspects of the present invention.
According to a fifth aspect of the present invention there is provided a directional drilling tool, comprising:
Embodiments of the fifth aspect of the present invention may comprise one or more features of the first, second, third and fourth aspects of the present invention.
According to a sixth aspect of the invention there is provided a directional drilling system, comprising:
Embodiments of the sixth aspect of the present invention may comprise one or more features of the first, second, third, fourth and fifth aspects of the present invention.
One of the advantages of the use of a planetary gear box is that a planetary gearbox has a considerable durability in high shock environments compared to other transmission devices, especially in coaxial transmission.
The present invention is particularly useful in a directional drilling sub having a bent portion where it is necessary to be able to rotate the bent portion with respect to the central axis of the drillstring in order to change the rotational orientation of the bent portion and thereby to change the direction of drilling.
It will be however will be appreciated that the present invention is not limited to the use in a bent sub only and indeed is useful in other applications where it is necessary control relative rotation of at least a pair of components in a downhole tool assembly. Coupling the harmonic drive to a primary motor of a downhole tool assembly, e.g. a topmotor or a downhole motor causes the harmonic drive to use the rotation of the primary motor to induce relative rotation of various parts of a down hole tool assembly which need to be controlled in a desired manner and which cannot be directly rotated by the primary motor. At the same time, and equally importantly, the incorporation of the harmonic drive into a downhole tool assembly of the present invention does not result in the loss of important primary functions of the downhole tool, e.g. the ability to drill or advance straight in the well bore.
For example, in drill pipe drilling, the present invention, in one mode of operation, provides for the rotation of the drill pipe during directional drilling while the bent housing is practically not rotating, thereby mitigating the friction problems associated with slide drilling and increasing the rate of penetration during directional drilling compared to the conventional slide drilling. Whereas in another mode of operation, the present invention provides for the rotation of the drillstring and the bent housing as one piece, thereby keeping the ability of the downhole tool assembly to drill straight ahead as opposed to drilling alternately in opposite directions when a generally straight path is required. Furthermore, the present invention allows the rotation of the drill pipe rotated by the topmotor to be used to orient the toolface and/or adjust the bend angle. Also, in drill pipe drilling, the harmonic drive in combination with an active clutch provide for the rotation of the drill pipe together with a BHA as one piece thereby permitting straight drilling. Also in drill pipe drilling, the harmonic drive in combination with a passive clutch provide for overtorque relief by interrupting the rotary connection between the drill pipe and the BHA so that the drill pipe can rotate without imparting torque on the BHA.
In both coiled tubing drilling and drill pipe drilling, the present invention allows the rotation of the downhole motor to be used to orient the toolface and/or to adjust the bend angle.
In both coiled tubing drilling and drill pipe drilling, the present invention allows the reactive torque acting on the stator component of the downhole motor to be utilised to orient the rotatable component of the BHA, such as the bent portion, as well as to correct the toolface which tends to be displaced due to the reactive torque during directional drilling. The use of both the active and reactive torques of a downhole motor permits the rotation of the rotatable component in opposite directions.
Thus, advantages of the present invention include the ability for the upper string to be rotated independently of any down-hole apparatus that is run below without imparting any torque or rotation to the apparatus being deployed and/or allowing the upper string to be rotated faster than the apparatus being deployed with a reduction in torque transmitted from the work-string to the said apparatus.
Further still, it may allow a predetermined torque to be held on the downhole tool without rotation of said downhole tool being deployed by maintaining a predetermined rotational speed in the work string above.
Further still, it may allow a predetermined torque limit to be set to avoid excess torque being transmitted into downhole tool and/or it may allow multiple tools to be run and functioned independently in the same work string so as to allow a combination of variable speed and torque to be conveyed to many parts of the same work string.
Moreover, it may allow multiple tools to be run and functioned independently in the same work string so as to allow a combination of variable speed and torque and tool lock out to be conveyed to many parts of the same work string and/or it may allow tools to be locked to provide full one to one drive from work string to the downhole tool that is being deployed.
Further still, it may allow the upper string to be rotated slower than the apparatus being deployed with a considerable reduction in torque transmitted from the work-string to the said apparatus and/or it may allow the upper string to be rotated faster than the apparatus being deployed with an increase in torque transmitted from the work-string to the said apparatus.
The present invention may find application in several applications, including:
Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:
b is a transverse cross-section of an outer gear having a device permitting rotation of the outer gear in one direction and preventing rotation in the opposite direction;
In the presently described embodiments the downhole tool assembly of the invention is described in the form of a directional drilling tool, as will be described in more detail below, comprising a BHA having a bent portion having a bent axis wherein the orientation of the bent axis in relation to a central axis of the BHA can be adjusted downhole. It will be appreciated that embodiments of the invention as described below, suitably adapted as would be readily apparent to a person skilled in the art, can be used in other downhole tools, such as for example logging, fishing, completions etc, where it is required to rotate a first body relative to a second body about a rotation axis.
Initially, referring to
A downhole tool assembly 1, 2, 3, 4, 5, 5a, 6, 7, 8, 9, 5000 according to a first aspect of the present invention comprises a BHA 10, 20, 30, 40, 50, 50a, 60, 70, 80, 90, 5050 comprising a bent portion (not shown). The downhole tool assembly 1, 2, 3, 4, 5, 5a, 6, 7, 8, 9, 5000 comprises a first body 11, 21, 31, 41, 51, 51a, 61, 71, 81, 91, 5051 and a second body 12, 22, 32, 42, 52, 52a, 62, 72, 82, 92, 5052 arranged to rotate one relative to the other about a rotation axis 1000 which is also a common axis of the first and second bodies. In the presently described embodiments, the downhole tool assembly 1, 2, 3, 4, 5, 5a, 6, 7, 8, 9, 5000 forms part of a drill string, but it will be appreciated that the present invention can be incorporated into other workstrings. At least one of the first or second bodies belongs to the BHA 10, 20, 30, 40, 50, 50a, 60, 70, 80, 90, 5050.
In the presently described embodiments, in the BHA 10, 20, 30, 40, 50, 50a, 60, 70, 80, 90, 5050 rotation of the first body 11, 21, 31, 41, 51, 51a, 61, 71, 81, 91, 5051 relative to the second body 12, 22, 32, 42, 52, 52a, 62, 72, 82, 92, 5052 results in the change of orientation of one of the two bodies with regard to the other. The change in the orientation can be angular, i.e. involve a change in the relative rotational disposition of the first and second bodies or longitudinal, i.e. involving a change in the angle between longitudinal axes of the first and second bodies or both.
The downhole tool assembly 1, 2, 3, 4, 5, 5a, 6, 7, 8, 9, 5000 comprises a drive arrangement 1001 for rotating the first and the second bodies relative to each other. The drive arrangement comprises a harmonic drive 13, 23, 33, 43, 53, 53a, 63, 73, 83, 93, 5053 comprising a wave generator 14, 24, 34, 44, 54, 54a, 64, 64′, 74, 84, 94, 5054 a flexible gear 15, 25, 35, 45, 55, 55a, 65, 65′, 75, 85, 95, 5055 and an outer gear 16, 26, 36, 46, 56, 56a, 66, 66′, 76, 86, 96, 5056. As will become more apparent from the following description, one of the wave generator, flexible gear and outer gear is adapted to function as a rotary input component and another of the wave generator, flexible gear and outer gear is adapted to function as a rotary output component.
Still referring to
The motor comprises a rotor component 17, 47, 57, 57a, 67, 77, 87, 97, 5057 (
In the embodiments shown in
In the embodiments shown in
In
In the embodiments of
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In
In
Often, a downhole assembly comprises a measuring device, for example a measurement while drilling (MWD) tool to read and measure drilling parameters. As shown in
The harmonic drive 13, 53, 53a, 63, 73, 83, 93 comprises a clutch or clutches arranged so as to selectively vary the transmission of rotation between the harmonic drive and the motor or to selectively alternately cooperate with one or more of the wave generator, the flexible gear and the outer gear so as to enable or restrict rotation of a gear and so as to permit or restrict rotation of another gear, thereby enabling the change in the direction of rotation between the first and the second body, or to selectively interrupt the rotary connection between the drill pipe and the BHA, e.g. in case of too high torque exerted on the BHA by the drill pipe. The clutch can be a passive clutch, i.e. adapted to be activated/deactivated conditionally, e.g. when a certain condition is met, e.g. when torque exerted on the BHA from the drill pipe exceeds predetermined value, the clutch is activated and the rotary connection between the drill pipe and the BHA is disconnected; or an active clutch, i.e. activatable by a positive control signal, such as operator's signal from surface.
In
In
In
In
In
Although not illustrated, in the arrangement of
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In the embodiments described with reference to
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In
The clutches may be selected from many suitable types, including conical clutches, freewheels, viscous coupling, Hele-Shaw clutches, fluid drive, wet multi-plate clutch, epicyclical planetary gear system, wet clutch, magnetic inductance and other suitable.
Although not illustrated, a planetary gearbox can be used in place of a harmonic drive. Such a planetary box comprises a sun, a planet carrier and an annulus, wherein one of the sun, planet carrier and annulus is adapted to function as a rotary input component and another of the sun, planet carrier and annulus is adapted to function as a rotary output component in the downhole assembly of the invention.
These and other modifications and improvements may be incorporated without departing from the scope of the present invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2013/000411 | 3/15/2013 | WO | 00 |
