Patent Description:
Aspects of the presently disclosed technology relate generally to systems and methods for drilling within a subterranean formation and more particularly to a drilling mud motor clutch.

Drilling fluid is circulated through a wellbore during drilling within certain subterranean formations. A drilling system for drilling subterranean formations is disclosed for example in <CIT>. A mud motor can generate torque from the circulation of drilling fluid. However, vibrations and shocks experienced by the drill string during a drilling operation can damage and/or cause failure of a mud motor. The vibrations and shocks can further damage the drill string drive shaft potentially causing failure and/or separation of the drill bit from the drill string. It is with these observations in mind, among others, that various aspects of the present disclosure were conceived and developed.

Implementations described and claimed herein address the foregoing problems by providing systems and methods for drilling within a subterranean formation. In one implementation, a drill string system includes a drill bit disposed at a distal end of a drill string. A clutch is coupled with the drill bit. A mud motor is coupled to the clutch, and the mud motor is operable to receive a drilling fluid therein and transfer torque to the drill bit through the clutch. The clutch disengages upon application of a torque exceeding a predetermined threshold.

Further, while multiple implementations are disclosed, still other implementations of the presently disclosed technology will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative implementations of the presently disclosed technology. As will be realized, the presently disclosed technology is capable of modifications in various aspects. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not limiting.

The foregoing summary, as well as the following detailed description, will be better understood when read in conjunction with the appended drawings. For the purpose of illustration, there is shown in the drawing certain implementations of the presently disclosed technology. It should be understood, however, that the presently disclosed technology is not limited to the precise implementations and features shown. The accompanying drawings, which is incorporated in and constitutes a part of this specification, illustrates implementations of apparatuses consistent with the presently disclosed technology, and, together with the description, serves to explain advantages and principles consistent with the presently disclosed technology, in which:.

In one aspect of the present disclosure there is provided a drill string system according to claim <NUM> and a method according to claim <NUM>. The present disclosure involves systems and methods for drilling in a subterranean formation. In one example, a clutch is incorporated between a mud motor power section and a drill bit. The drill bit may be disposed at a distal end of a drill string, with the clutch coupled with the drill bit. The mud motor is coupled to the clutch and operable to receive a drilling fluid therein and generate torque to the drill bit through the clutch. The clutch disengages upon application of a torque exceeding a predetermined threshold. The clutch can be bi-directional, and the predetermined threshold may include a first predetermined threshold in a first rotational direction and a second predetermined threshold in a second rotational direction. The first predetermined threshold is a max torque for the mud motor, and the second predetermined threshold is any torque exceeding zero (N*m). The predetermined threshold can be adjustable. A rotor catch can operable couple the drill bit and the clutch, and the rotor catch is operable to maintain a coupling between the drill bit and the clutch in the event of clutch failure.

A mud motor assembly can include a mud motor having a rotor rotationally received within a stator, and a clutch operably coupled with the mud motor and operable to be coupled with a drill bit. The clutch operably disengages upon application of a torque exceeding a predetermined threshold. The mud motor can be operable to receive a drilling fluid therein, with the drilling fluid operable to induce rotation of the rotor relative to the stator. The mud motor can be a progressive cavity positive displacement pump operable to receive a drilling fluid therein. The stator can have a plurality of lobes operable to rotationally receive a corresponding lobe on the rotor during rotation of the rotor within the stator.

A drill string may be disposed in a wellbore within a subterranean environment. In one example, the drill string has a drill bit, a clutch, and a mud motor. The clutch is operable to transfer rotational power from the mud motor to the drill bit, and the drill bit is engaged with at least a portion of the subterranean formation. A drilling fluid is received in the mud motor, and a torque is generated in the mud motor. The torque is transferred from the mud motor to the drill bit. The clutch is disengaged if the torque on the mud motor exceeds a predetermined threshold. The clutch may be reengaged if the toque reduces below the predetermined threshold.

Generally, the clutch may be located in relation to different parts of a direction drilling rig bottom hole assembly (BHA), which uses a displacement or mud motor. A mud motor is generally a screw-type motor utilizing an incoming fluid to rotate at approximately <NUM>-<NUM> RPM, for example. The BHA may be bent at some point, for example by approximately two degrees. When drilling straight, the entire BHA may be rotated (e.g., at about <NUM>-<NUM> RPM). The mud motor also turns (e.g., at about <NUM>-<NUM> RPM), and the drill bit itself may rotate with both rotations (e.g., turning approximately <NUM>-<NUM> RPM). Where a bent section is rotating, the overall direction may be predominately straight. In one example, during directional drilling, the drill string strops rotating and the drill bit is only rotated by the mud motor (e.g., <NUM>-<NUM> RPM), which refers to slide drilling.

In some cases, a sub may be used to insert a bend angle, and in some cases dual bend angles in opposite directions may be used for straight drilling and aligned toward a turn for directional drilling. The mud motor rotates, creating an off-centered rotation or wobbly drive. The flex shaft takes the off-centered rotation of the mud motor and creates a concentric drive for the rest of the drive shaft. Universal joints may be placed between sections of the drive shaft to allow flex and bending. Bearings may be placed above or below the bend to transfer weight from the drive to the drill string.

The clutch may be positioned directly above the drill bit, for example using a clutch sub that is threaded to fit in the drive and receive the drill bit. In another example, the clutch may be positioned at the end of the drive shaft. The clutch may allow the remaining drive shaft, bearings, universal joints, and flex shaft to be made of a lower grade metal, while enabling a drilling with a higher RPM without damaging the bit or shaft. In another example, the clutch may be incorporated anywhere after the mud motor, including, without limitation being incorporated into the bearing assembly, at a bend, at a universal join, before the flex shaft, after the flex shaft, and/or the like.

As used herein, the term "motor," "mud motor," "drilling motor," and the like refers to a device that converts hydraulic, electrical, or other energy into mechanical energy or imparts motion. In the case of a mud motor, the device converts hydraulic pressure into rotational motion. The mud motor may be a progressive cavity positive displacement pump (PCPD) motor, turbine, or other motor.

As used herein, the term "clutch," refers to a coupling used to connect and disconnect a driving and a driven part of a mechanism, especially a coupling that permits the former part to engage the latter gradually and without shock. In the oil field, a clutch permits gradual engaging and/or disengaging of the equipment driven by a motor. In one implementation, an overrun clutch may be used to mechanically separate the driveshaft from the driven shaft when the driveshaft behaves in a certain way. The overrunning clutch operates when the driveshaft or input rotates slower than the driven shaft or output. It also disengages when the driveshaft completely stops. In another implementation, an overload clutch, torque clutch, or guard clutch quickly disengages the drive system in overload or jam conditions. The clutch then re-engages when torque is reduced or under specific conditions dependent upon the clutch design and specifications.

For example, a process, product, article, or apparatus that comprises a list of elements is not necessarily limited only those elements but can include other elements not expressly listed or inherent to such process, process, article, or apparatus.

The term substantially, as used herein, is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder.

Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead these examples or illustrations are to be regarded as being described with respect to one particular example and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized encompass other examples as well as implementations and adaptations thereof which can or cannot be given therewith or elsewhere in the specification and all such examples are intended to be included within the scope of that term or terms. Language designating such non-limiting examples and illustrations includes, but is not limited to: "for example," "for instance," "e.g.," "In some examples," and the like.

Although the terms first, second, etc. can be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the presently disclosed technology.

The present disclosure is drawn to a clutch operable to be implemented with a mud motor in a downhole environment. The mud motor can be operably arranged within at least a portion of a bottom hole assembly (BHA) and/or a drill string for formation of a wellbore through at least a portion of a subterranean environment. The mud motor can be operated by circulating a drilling fluid through the wellbore and/or transfer power from the mud motor to the drill bit, thereby increasing the rate of penetration (ROP) of the drill string the subterranean formation. The drill string can have a clutch disposed between the mud motor and the drill bit to prevent stalling of the mud motor in the event a torque exceeding a predetermined threshold.

<FIG> illustrates a diagrammatic view of a drilling operation through a subterranean formation, according to at least one instance of the present disclosure. The drilling operation <NUM> can include a drilling rig <NUM> having a drill string <NUM> operably forming a wellbore <NUM> through at least a portion of a subterranean formation <NUM>. A bottom hole assembly (BHA) <NUM> can be disposed at a downhole distal end <NUM> of the drill string <NUM>. The BHA <NUM> can include a drill bit <NUM> and a mud motor <NUM>. The drill bit <NUM> can be operably arranged to rotational engage a portion of the subterranean formation <NUM>, thereby operably forming the wellbore <NUM> therethrough. The mud motor <NUM> can be arranged uphole of the drill bit <NUM> and is operable to generate power via the flow of a drilling fluid (e.g. drilling mud). In some instances, the mud motor <NUM> and the drill bit <NUM> can be in fluidic communication allowing the drilling fluid to be expelled through one or more openings in the drill bit <NUM> to circulate formation cuttings away from the drill bit <NUM> and/or provide lubrication between the drill bit <NUM> and the subterranean formation <NUM>.

In some instances, the BHA <NUM> can have a slight deviation (e.g. <NUM>°, <NUM>°, <NUM>°) along its longitudinal length. In operation, the drill string <NUM> and/or the mud motor <NUM> can be rotated to provide energy transfer to the drill bit <NUM>, thereby assisting in the formation of the wellbore <NUM> in the subterranean formation. Due to rotation of the slight deviation, the drill string <NUM> produces a substantially straight wellbore <NUM> when the drill string rotates. During directional drilling, the drill string rotation is stopped with the deviated section directed in the direction of borehole deviation and the mud motor become the primary rotational force. This drives the borehole in the direction of the deviation until the well bore reaches the desired directional drilling. In some instances, the well bore is horizontal with respect to the formation allowing a horizontal well to access the length of the formation.

In some instances, the BHA <NUM> can have a slight deviation from longitudinal (e.g. <NUM>°) along its longitudinal length. In operation, the drill string <NUM> and/or the mud motor <NUM> can be rotated to provide energy transfer to the drill bit <NUM>, thereby assisting in the formation of the wellbore <NUM> in the subterranean formation. Due to rotation of the slight deviation, the drill string <NUM> produces a substantially straight wellbore <NUM>. In other instances, the BHA <NUM> can have two deviations from longitudinal in which the two deviations are arranged in opposite directions to produce straight wellbore <NUM>, and the deviations can be aligned in the same direction to form the wellbore <NUM> in toward the deviation in directional drilling.

As the drilling fluid is pumped through the mud motor <NUM>, the mud motor <NUM> can convert hydraulic horsepower from the flow of the drilling fluid to torque and/or bit speed to the drill bit <NUM>. The power transferred to the drill bit <NUM> by the by mud motor <NUM> can increase the efficiency of the drilling operation <NUM> and increase the ROP of the drill string <NUM> through the subterranean formation <NUM>. The mud motor <NUM> can have a flex shaft disposed between the mud motor <NUM> and a drive shaft <NUM> coupled with the drill bit <NUM>. One or more universal joints can be implemented along the drive shaft <NUM> to allow flex and/or bending between sections of the drive shaft <NUM>. One or more bearing assemblies can also be disposed above and/or below the bend to assist in weight transfer from the drive to the drill string <NUM>.

The BHA assembly <NUM> can include one or more flex shafts and/or universal joints arranged between the mud motor <NUM> and/or the drill bit. The one or more flex shafts and/or universal joints can be operable to receive the substantially concentric power and create true concentric rotation to the drill bit <NUM>. In some instances, specifically instances directionally drilling, the mud motor can be operated at a predetermined speed while the drill string <NUM> is maintained substantially stationary.

A clutch <NUM> can be operably arranged between and adjacent to the drill bit <NUM> and the mud motor <NUM> at the distal end <NUM> of the drill string <NUM>. The clutch <NUM> can be coupled with the driveshaft and/or the drill bit <NUM>. In one implementation, the clutch is attached directly to the motor drive shaft, protecting the drive shaft, joints and drill bit from motor torque. In another implementation, the clutch may be attached directly to the drill bit, protecting the drive shaft and mud motor from jarring by the drill bit.

The drill string <NUM> can be operably arranged to form a wellbore <NUM> through at least a portion of the subterranean formation <NUM> through rotation of the drill bit <NUM>. Rotation of the drill string <NUM> and/or the drill bit <NUM> can engage the drill bit <NUM> with the subterranean formation <NUM>, thereby grinding and/or eroding the subterranean formation <NUM> and forming the wellbore <NUM> therethrough. A drilling fluid can be circulated through the wellbore <NUM> to remove the drill cuttings (e.g. fragments of the subterranean formation <NUM>) formed by the erosive engagement between the drill bit <NUM> and the subterranean formation <NUM>.

<FIG> illustrates a detailed isometric view of a distal end of a drill string, according to at least one instance of the present disclosure. The mud motor <NUM> can be operably arranged to receive a portion of the drilling fluid therethrough. The flow of the drilling fluid through the mud motor <NUM> can generate a rotation motion along the drive shaft <NUM> coupling the mud motor <NUM> and the drill bit <NUM>. The mud motor <NUM> can be operably arranged to transfer the rotational energy generated by the flow of the drilling fluid to the drill bit <NUM>, thereby increasing the rate of penetration (ROP) of the drill string <NUM>.

As the drill bit <NUM> engages the subterranean formation <NUM>, various shocks, vibrations, and/or motions can be felt along the drill bit, the mud motor, and/or the drill string <NUM>. The clutch <NUM> can be operably arranged between the mud motor <NUM> and the drill bit <NUM> to protect the mud motor <NUM> from damage in the event of a torque spike along the drive shaft <NUM> from drill bit <NUM>. In at least one instance, the clutch <NUM> can be threadingly engaged with the driveshaft <NUM> and operable to receiver the drill bit <NUM> therein. In other instances, the clutch <NUM> can be disposed at any location on the drill string <NUM> downhole of the mud motor <NUM>.

The drill string <NUM> can experience a torque spike and/or other shock event in instances where the drill bit <NUM> over engages the subterranean formation <NUM>, thereby generating a drill bit stall. A drill bit stall occurs with the torque supplied by the drill string <NUM> and/or the mud motor <NUM> is not sufficient to keep rotating the drill bit.

A mud motor <NUM> arranged along a drill string <NUM> can be optimized to withstand the desired drive torque to be generated by the drilling fluid passing therethrough, but also any drill bit stalls, torque spikes, and/or other shock events occurring during a drilling operation. Therefore, mud motors are frequently operated at far below their optimal torque output to provide a threshold to absorb torque spikes. This excessive operating threshold in the mud motor <NUM> results in inefficiency as the mud motor <NUM> cannot be operated at its peak design parameters to prevent potential damage during a torque spike. The clutch <NUM> can provide a buffer between the drill bit <NUM> and the mud motor <NUM>, thereby allowing the mud motor <NUM> to be operated at an optimal toque output without the need for an excessive operating threshold. Further, the clutch <NUM> can allow any elements disposed between the mud motor <NUM> and the clutch <NUM> including, but not limited to, drive shaft sections, bearings, universal joints, and/or flex shafts to be made of lower grade materials as they no longer require a threshold to absorb potential torque spikes.

The clutch <NUM> can prevent damage to the mud motor <NUM> in the event of the torque spike and/or other shock even by allowing the mud motor <NUM> to "slip" if the torque experienced from the mud motor <NUM> by the clutch exceeds a predetermined threshold. The clutch <NUM> allowing the mud motor <NUM> to "slip" can allow the mud motor to continue rotational movement a substantially continuous RPM despite the drill bit <NUM> stall or other shock event, thereby preventing damage to the mud motor <NUM>.

The clutch <NUM> can allow the mud motor <NUM> to be operated much closer to the peak torque and/or RPM output because the clutch <NUM> can disengage and/or allow the mud motor <NUM> to "slip" in the event of the torque spike event. The disengagement between the drill bit <NUM> and the clutch <NUM> can prevent damage to the mud motor <NUM> during the torque spike. In at least one instance, the clutch <NUM> can re-engage upon the torque falling below the predetermined threshold.

In some instances, the clutch <NUM> can be a bi-directional clutch having a first predetermined threshold in a first rotational direction (e.g. clockwise) and a second predetermined threshold in a second rotational direction (e.g. counter-clockwise). The clutch <NUM> can thus be operable to disengage (e.g. "slip") if the drill bit <NUM> experiences a torque event above the first predetermined threshold in the drilling rotational direction (e.g. clockwise), but also allow the clutch <NUM> to disengage if the drill bit <NUM> begins to rotate in a reverse direction. In at least one instance, the first predetermined threshold can be operably arranged for the maximum desired operating torque output by the mud motor <NUM>, while the second predetermined threshold can be a minimal torque threshold. The second predetermined threshold can thus disengage the clutch upon the application of any measurable torque in a rotational direction opposite of the first predetermined threshold. In at least one instance, the second predetermined threshold is any torque greater than zero (Newton-meter). The clutch <NUM> can re-engage upon the torque falling below either the first predetermined threshold and/or the second predetermined threshold.

The clutch <NUM> can have an adjustable and/or user-defined first predetermined threshold and/or second predetermined threshold. In at least one instance, an operator can select the first predetermined threshold and second predetermined threshold of the clutch <NUM> based on the drill bit <NUM> and/or the mud motor <NUM> being implemented in a particular drilling operation. In some instances, the second predetermined threshold is not user-adjustable.

The clutch <NUM> can have a rotor catch engagement <NUM> with the drill bit <NUM>. The rotor catch engagement <NUM> can be operably arranged to maintain engagement between the clutch <NUM> and/or the drill bit <NUM> in the event the clutch <NUM> breaks in a downhole environment. The rotor catch engagement <NUM> can be operably arranged to allow the drill string <NUM> to be pulled-out-of-hole (POOH) in the event of damage to the drill bit <NUM>, mud motor <NUM>, and/or clutch <NUM> without risking leaving the drill bit <NUM> downhole, and thereby requiring an expensive and/or time consuming operation. In at least one instance, the rotor catch engagement <NUM> can be a tongue and groove arrangement disposed around an inner surface of the drill bit <NUM> and an outer surface of the clutch <NUM>, thereby allowing free rotation of the drill bit <NUM> relative to the clutch during operation, but preventing disengagement between the drill bit <NUM> and the clutch.

It is understood that the specific order or hierarchy of steps in the methods disclosed are instances of example approaches and can be rearranged while remaining within the disclosed subject matter. The accompanying method claims thus present elements of the various steps in a sample order, and are not necessarily meant to be limited to the specific order or hierarchy presented.

Claim 1:
A drill string system comprising:
a drill bit (<NUM>) disposed at a distal end of a drill string (<NUM>);
a clutch (<NUM>) coupled with the drill bit (<NUM>);
a mud motor (<NUM>) coupled to the clutch (<NUM>), the mud motor (<NUM>) operable to receive a drilling fluid therein and transfer torque to the drill bit (<NUM>) through the clutch (<NUM>); wherein the clutch (<NUM>) disengages upon application of a torque exceeding a predetermined threshold; the system being characterised in that comprises
a rotor catch (<NUM>) operably coupling the drill bit (<NUM>) and the clutch (<NUM>), the rotor catch (<NUM>) operable to maintain a coupling between the drill bit (<NUM>) and the clutch (<NUM>) in event of clutch failure of the clutch (<NUM>).