Patent ID: 12241370

Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.

DETAILED DESCRIPTION OF THE INVENTION

This disclosure provides for a compact mechatronic system that enables drilling of very high aspect ratio, small-diameter holes in remote, confined spaces. The system according to the present disclosure addresses some of the challenges associated with drilling such holes by a) limiting the unsupported drill bit length throughout the drilling process, b) actively injecting energy to remove cuttings, and c) enabling the use of flexible drills to extend drillable length. The systems and methods according to the present disclosure automate drilling capability and the ways that the controlled process interacts with drilling mechanics.

In one embodiment, the present disclosure provides a new approach to structural/material integrity that uses small holes to be precisely drilled into a structure/material. In an embodiment, the small holes may be drilled into and potentially through a body to the structure/material to be monitored. In various embodiments, the access to the point of drilling may be distant and/or remote with the space confined and/or restricted in diameter or area. In an embodiment, the confined space may be a steel well casing. In an embodiment, the structural/material integrity may be that of an outer cement well casing. In various embodiments, the small holes may be used to place various sensors to monitor the area surrounding the sensors. The holes may be drilled at an angle from the direction of access to the drilling point, such as orthogonal to the access direction. In one embodiment, the holes may be filled after drilling of the holes. For example, the holes may be filled with sensors, equipment or filler material.

FIG.1shows a drilling system100for drilling high aspect ratio, small diameter holes in a confined space101according to an embodiment of the disclosure. The confined space101has a confined dimension103and a non-confined dimension105having at least one opening101anot in the axis of the confined dimension. The confined dimension103is a dimension that has no access to outside that confined space from that dimension. In an embodiment, the confined dimension103may have restricted access that prevents a drilling tool from having access to the confined space. In the exemplary embodiment shown inFIG.1, the confined space101is the interior space of a wellbore102having a generally cylindrical geometry having a length (L)105to diameter (D)103ratio (L/D). In this exemplary embodiment, the confined space has an L/D greater than 1000:1 In other embodiments, the L/D may be between 5:1 to 50000:1. In an embodiment, the L/D may be between 1000:1 and 10000:1. In various embodiments, the diameter D may be between 5 inches and 48 inches.

As discussed above, in the wellbore102, the confined dimension103is the diameter of the wellbore102. In this exemplary embodiment, the wellbore102has no opening opposing opening101aand the non-confined dimension105is the depth of the wellbore102. In other embodiments, the confined space101is not limited to a cylindrical wellbore102and may include other spaces, such as, but not limited to pipes, pipelines, conduits, ducts, conveyances, and other structures that have limited or restricted access. In those other embodiments, the confined spaces are not limited to cylindrical geometries, but include cylindrical, rectangular prismatic, elliptical prismatic, irregular and other geometries. For example, the confined space101may be an access space created to enable repairs/maintenance to foundations or other underground structures, a storage tank (e.g., underground waste tank or above-ground tank for hazardous materials), a storage container for chemical, nuclear or radiological waste, a tunnel, or a utility chase.

The drilling system100includes an insertion assembly100aand a compact drill assembly104positioned in confined space101. In one embodiment, the compact drill assembly104is directed into the confined space101along the non-confined dimension105. In this exemplary embodiment, the insertion assembly101ais a cable or line107, a control rig109and a winch (101b). In other embodiments, the insertion assembly101amay be a wireline with gravity feed, a crawling or climbing device, a fluid buoyancy mechanism, a drillstring lowered into a cased hole, or a robot that may be wheeled, tracked, legged or otherwise mobile that is capable of inserting the compact drill assembly into a confined space.

In the embodiment shown inFIG.1, the compact drill assembly104is lowered into the confined space101, which is a wellbore102, along the non-confined dimension105. Motion along the non-confined dimension105is a motion in a direction corresponding to an axis downward into the wellbore102. The motion and support for the compact drill assembly104are provided by line107which is suspended from control rig109. The control rig109permits support and motion of compact drill assembly104. Line107may be any support structure, including but not limited to a cable, rope, chain, or other suitable flexible support structure capable of supporting the compact drill assembly104. In some embodiments, wiring and/or electronics may be provided as line107or in addition to line107, such as cabling run parallel to line107, to provide control and/or signal to the drill assembly. In other embodiments, compact drill assembly104may also be powered by batteries or other portable power sources. Signal, for example for control of the assembly, may be provided by line107or wirelessly via any suitable wireless transmission method, such as, but limited to, wireless fidelity (Wi-Fi), Wi-Fi direct, wireless USB (wireless universal serial bus), BLUETOOTH (BLUETOOTH), Radio Frequency Identification (RFID), infrared data association (IrDA), Ultra-Wideband (UWB), Near Field Communication (NFC), point-to-point optical/laser communications, and acoustic communications.

The compact drill assembly104includes a housing111having a geometry that allows insertion into the confined space101. The geometry of housing111may include any suitable dimensions that permit the positioning of the compact drill assembly104into the confined space101. The housing111has a dimension less than the confined dimension of the confined space101so the housing111may be inserted into the confined space. The housing111may be cylindrical, cuboid, spherical or other geometry that permits positioning into the confined space101. The housing111includes structures to support and position the drilling equipment. In addition, housing111includes securing features113that are capable of engaging surfaces of the confined space101and securing the compact drill assembly104into a position within the confined space101. Securing features113also include an actuator (not shown) that extend or retract the securing features in a direction away from housing111to secure or release the compact drill assembly104in a location within the confined space101. The securing features113may be protrusions, pads, hooks, friction features or other structures that are capable of securing the compact drill assembly104within the confined space103. In other embodiments, the securing features113may include wheels or other drive mechanisms that allow movement and positioning of the compact drill assembly104. In this embodiment, the wheels or drive mechanisms may secure the compact drill assembly104or securing features113may also be used to secure the compact drill assembly104.

As shown inFIGS.2and6-7, drill assembly104includes a rotatable drilling spindle115that includes an actuated locking collet assembly117arranged and disposed to selectively secure and release a composite bit119. The drilling spindle115also includes a drilling motor200that is a motor or other drive mechanism arranged to provide rotation to the drilling spindle115, including the actuated locking collet assembly117and the composite bit119. Rotation of the drilling spindle115by drilling motor200is sufficient to facilitate drilling by the composite bit119. Drilling rotation provided by drilling motor200includes rotation of the composite bit119at from up to 20,000 RPM or up to 10,000 RPM or up to 5,250 RPM or up to 5,000 RPM. Particularly suitable drilling speeds are up to 5,000 RPM. The actuated locking collet assembly117includes a mechanical arrangement that is capable of exerting a clamping force to secure the composite bit119. The actuated locking collet assembly117according to the present disclosure is actuatable to either secure or release the composite bit119. In the released position, the composite bit119is movable and may be advanced or retracted withing the drilling spindle115. Actuation of the actuated locking collet assembly117can be a mechanical actuation or electronic actuation. Composite bit119is retained when the actuated locking collet assembly117is in a secured position within the rotatable drilling spindle115. When the composite bit119is retained, the composite bit119may be rotated with the rotatable drilling spindle115to facilitate drilling. The composite bit119utilized in the drilling system100may be a bit having a rigid section801and a flexible section803(see for example,FIG.8). In other embodiments, the composite bit119may be a composite bit formed of multiple materials or may be a flexible, single-material bit.

The compact drill assembly104further includes a bit conveying arrangement121that is configured to convey the composite bit119along the non-confined dimension105and along the confined dimension103through the actuated locking collet assembly117. As shown inFIGS.1and2, the composite bit119is aligned in a vertical direction along the axis of the wellbore102and is directed in a direction perpendicular to the wellbore axis to an axis that permits drilling into the sidewall of the wellbore102. As show inFIGS.2-5, the bit conveying arrangement121includes a bit brake201arranged along the non-confined dimension and bit drive203arranged along the confined dimension. The bit brake201includes a brake actuator205and brake member207. The brake actuator205is a linear actuator or other drive mechanism to urge brake member207into engagement with composite bit119. The bit brake201selectively holds the composite bit119in position to provide control of the motion of the composite bit119through the compact drill assembly. The selective engagement permits rotation of the composite bit119. That is, bit brake201does not hold the composite bit119in place during drilling. Rather, for example, bending load forces on the composite bit119bit urge the composite bit119into a groove of a rear plate of the bit brake201that keeps the composite bit119in the same shape while drilling. The brake member207allows rotation of the composite bit119when the drilling spindle115is rotating the composite bit119. Bit brake201provides a mechanical arrangement that retains the composite bit119in place, but allows relative motion between the composite bit119and the compact drill assembly104to allow the compact drill assembly104to retract or feed the bit into the drilled hole125.

FIGS.3-4show a portion of the compact drill assembly104, including the drilling spindle115, separated from housing111. As shown inFIGS.2-4, the bit drive203advances or retracts composite bit119through the drilling spindle115. Bit drive203includes a drive wheel301driven by bit motor302and idler wheel303that selectively engage composite bit119to move the composite bit119into or out of drilling spindle115. Bit motor302is any suitable motor arranged and disposed to rotate drive wheel301. As shown inFIG.4, bit drive203further includes a drive actuator401to move idler wheel303into contact with the composite bit and drive wheel301. The drive actuator401is a linear actuator or other drive mechanism to urge idler wheel303into a frictional engagement with composite bit119and drive wheel301. The idler wheel303is permitted to freely rotate while the drive wheel301rotates against composite bit119and idler wheel303to advance or retract composite bit119into the drilling spindle115.FIG.5shows an enlarged section403fromFIG.4illustrating action of the drive actuator401on idler wheel303, directing the idler wheel303into drive wheel301. The top enlarged section403ofFIG.5shows the idler wheel303in the released position, while the lower enlarged section403ofFIG.5shows idler wheel303in the engaged position. When the idler wheel303is in the engaged position, the bit motor302may rotate the drive wheel301and advance or retract composite bit119into or out of drilling spindle115.

As shown inFIGS.1-2, a linear drill drive123is arranged and disposed to advance the rotatable drilling spindle115along the confined dimension103. As shown inFIG.1, the linear drill drive123advances the drilling spindle115along a horizontal axis into the side of the wellbore102to form drilled hole125and provides the force utilized for drilling. The linear drill drive123may provide the advancing motion of the drilling spindle115by any suitable mechanism. For example, as shown inFIG.1, the linear drill drive123may be a worm drive driven by a rotary motor. However, other mechanisms may be utilized, such as linear actuators, rack and pinion arrangements, ball screw or lead screw, electromagnetic linear motor, piezoelectric linear drive, belt or cable driven system or any other mechanism that enables linear motion.

FIGS.2and6-7show cutaway views of the drilling spindle115including the actuated locking collet assembly117to engage and release composite bit within the drilling spindle115. The actuated collet assembly117includes a collet209, collar211and a collar nut212. The collar211includes a tapered geometry that compresses the collet209when the collar211is engaged along the outer surface of the collet209. Collar211includes outside threading213that engages internal threading215of collar nut212that, when the collar nut212is rotated, drives the collar211toward or away from the collar nut212. In a first rotational direction, the collar211is urged toward the collar nut212and includes surfaces of collar211that engage and compress collet209into an engaged position. In a second rotational direction, the collar211is urged away from collar nut212where the engaged surfaces of the collar211allow a releasing of collet209. Specifically, as shown inFIG.2, the collet209engages and retains composite bit119.

The actuated locking collet assembly117is engaged and disengaged via rotation of the driving gear217with respect to locking gear219. Locking gear219is attached to collar211and rotates independently with respect to driving gear217and collar nut212. Driving gear217is attached to and provides rotation of collar nut212with respect to collar211. Collet motor221is rotationally attached to driving pinion223to facilitate rotation of driving pinion223. Locking pinion225is fixed in place and is not permitted to rotate. When actuated, actuated locking collet assembly117is moved from an engaged position to a released position or from a released position to an engaged position by activation of a collet actuator227, which moves collet motor221, driving pinion223, and locking pinion225into engagement with locking gear219and driving gear217. The collet actuator227is a linear actuator or other drive mechanism capable of urging collet motor221, driving pinion223, and locking pinion225into engagement with locking gear219and driving gear217. The collet actuator227may include any suitable linear drive, such as, but not limited to a worm drive driven by a rotary motor, linear actuators, rack and pinion arrangements, ball screw or lead screw, electromagnetic linear motor, piezoelectric linear drive, belt or cable driven system or any other mechanism that enables linear motion. The collet motor221rotates the driving pinion223and, accordingly, driving gear217, to urge the collar211, via outside threading213and collar nut212, via internal threading215, toward or away from each other.

FIG.7illustrates actuation of actuated locking collet assembly117including enlarged section601and enlarged section603fromFIG.6. As shown inFIG.7, the collet209is compressed by frictional engagement with collar211. To begin the actuation into the engaged position, the collet actuator227is activated to urge the driving pinion223and locking pinion225into engagement with driving gear217and locking gear219, respectively (on left). Collet motor221rotates the driving pinion223so that the driving gear217rotates collar nut212and urges collar211via outside threading213and collar nut212via internal threading215toward each other, compressing the collet209to engage and retain composite bit119.

FIG.8shows a composite bit119according to the present disclosure. The configuration of the confined space101may not allow sufficient length for a conventional rigid drill bit to be positioned along the axis of the confined dimension103to provide drilled holes125of desired depth. Accordingly, composite bit119includes a rigid section801and a flexible section803. In one embodiment, the rigid section801is carbon tool steel, high-speed steel, cobalt high-speed steel. Rigid section801may also include carbide, ceramic, or titanium. Other suitable materials for rigid section801may include cutting materials, such as, but not limited to, polycrystalline diamond composite inserts or diamond cutting elements. In one embodiment, the flexible section803is nitinol or carbon fiber. Flexible section803may include, but is not limited to, titanium, spring steel, polymers (e.g., Nylon). In another embodiment, the rigid section801and the flexible section803are a unitary component, such as a component having unitary material. In this embodiment, the rigid section801may have at least some flexibility. For example, in the embodiment where a unitary material is utilized, the composite bit119may be a spring steel part with a sharp cutting edge that is locally heat treated for hardness. The rigid section801and flexible section803are joined utilizing any suitable technique, including but not limited to welding, soldering, brazing, adhesion, mechanical interconnection, interference fits, geometric fits (e.g., keys, flats on shafts, or set-screws). The rigid section801and the flexible section803are joined utilizing techniques that allow sufficiently high torque capabilities for drilling, sufficient flexibility of the flexible section803for drilling and permit sufficient cutting ability of the rigid section801for drilling.

FIG.9shows such an alternate embodiment for composite bit119drilling at a 90-degree bend. As shown inFIG.9, the composite bit119is directed through a conduit901to facilitate controlled drilling at angles to the original direction from which the composite bit119is fed. The conduit901may be utilized within the compact drill assembly104or outside of the compact drill assembly104to permit drilling in locations that are otherwise could not be reached due to the angle at which the drilling is to take place. The composite bit119arrangement, as shown inFIG.9allows the composite bit119to pass entirely through it with a bend at a significant angle. For example, while not so limited the composite bit119may bend at 90-degrees or within 5 degrees or within 10 degrees or within 15 degrees or within 30 degrees or within 45 degrees of 90 degrees. In other embodiments, multiple conduits901of arbitrary lengths and angles may be used to guide the composite bit119. In theory bits of arbitrary length could be used. Conduit901may allow standoff from the compact drill assembly104to the point of drilling. For example, in one embodiment, the compact drill assembly104may be aligned along the unconfined dimension105and the bend of the composite bit119along the confined dimension103may be downstream of the collet assembly117. Conduit901may be utilized in particularly tight confined spaces101, such as confined spaces101having small diameters or irregular diameters. Conduit901may also be used if it is not possible to bring the collet assembly119close enough to the entry point of the composite bit119. For example, in one embodiment, the conduit901may be utilized to direct the composite bit119to drill a ½″ diameter hole at the bottom of a confined space101that is a few inches deep. Conduit901may permit drilling in arbitrarily complex geometries.

In other embodiments, the composite bit119may be a rigid bit and the conveying arrangement121is disposed within the housing111to allow for feeding the rigid bit in the confined dimension.

Embodiments according to the present disclosure include drilling methods for drilling small diameter, high aspect ratio drilled holes in a confined space101. A compact drill assembly104is secured within the confined space with securing features113. Composite bit119is conveyed by the compact drill assembly104along the non-confined dimension105and along the confined dimension103, at an angle to the wellbore102. For example, while not so limited the composite bit119may be conveyed at an angle of 90-degrees or within 5 degrees or within 10 degrees or within 15 degrees or within 30 degrees or within 45 degrees of 90 degrees to the non-confined dimension105. The composite bit119is advanced along the confined dimension103and is rotated with the compact drill assembly104to drill into a surface along an edge of the confined space101. The compact drill assembly104includes a drilling spindle115that includes an actuated locking collet assembly117that can clamp and release a composite bit119, a rotary motor to produce drilling torque and rotary motion, and a linear drill drive123to produce drilling force and linear motion, and a drill bit feed mechanism capable of clamping, releasing, and translating the drill bit relative to the drilling spindle along the drilling direction. The method and system minimize the unsupported drill bit length throughout the process, enabling the bit to be progressively fed from the drilling spindle as depth increases. The compact drill assembly, when used with flexible composite bits119, drills holes of arbitrary depth and aspect ratio may be drilled orthogonal to the wellbore. The method and system achieve holes with substantially greater aspect ratios than conventional methods with very long drill bits.

Through a series of sequential steps, the compact drill assembly104is capable of remote and/or automated drilling. To begin the drilling process, the composite bit119is placed into the feeding mechanism including the bit drive203which consists of a geared brushed DC motor with drive wheel and an electromagnetic solenoid connected to the idler wheel303. To advance the bit forward the feeding mechanism, as shown inFIGS.4-5, drive actuator401is actuated which clamps the composite bit119between the drive wheel301and idler wheel303. The DC motor turns the drive wheel301until the composite bit119is fed to the minimum desired unsupported drilling length. The composite bit119is then locked in place by the actuated locking collet assembly117, as seen inFIGS.2and6-7. To clamp the composite bit119, collet actuator227is actuated, forcing the drive pinion223and locking pinion225to mesh with driving gear217and locking gear219, respectively. The driving gear217and locking gear219are attached to the collar nut212and collar211, respectively. With the collet actuator227actuated, the locking pinion225meshes with the locking gear219attached to the drilling spindle115, thus locking the drilling spindle115in place. The brushless DC (BLDC) collet motor221rotates the driving pinion223that is meshed with the driving gear217attached to collar nut212. Once the required torque to clamp the composite bit119is achieved, the collet actuator227disengages and the BLDC drilling motor200rotates the composite bit119. The required motor torque to clamp may depend on the transmission ratio between the collet motor221and collet assembly117. In one embodiment, the torque utilized to clamp at the composite bit119is a minimum of the drilling torque/coefficient of friction of composite bit119and collet assembly117. The drilling torque/coefficient of friction, as utilized herein, is drilling torque divided by the coefficient of friction. Examples of suitable values for the transmission ratio between the collet motor221and collet assembly117include, but are not limited to,1:1or5:1or10:1or20:1. To clamp the composite bit119, in one embodiment, while not limited, collet motor217may be run to clamp the composite bit119until the motor stalls resulting in approximately 12.5 Nm of torque at the composite bit119. The linear drill drive123advances the mechanism forward towards the desired area to be drilled to begin drilling. The linear drill drive123continues to advance the drill spindle115forward for the full length or near full length of the unsupported composite bit119, while periodically reversing to clear chips as needed. Once the length of the unsupported composite bit119has been drilled, the linear drill drive123reverses, the composite bit119is released by the actuated locking collet assembly117, and the composite bit119is fed to the minimum desired unsupported drilling length. This process is repeated until the desired hole depth is achieved.

The compact drill assembly and method according to the present disclosure form small diameter, deep holes having a length/diameter (L/D) greater than 75:1 or greater than 100:1 or greater than 125:1 or greater than 150:1. L/D, as utilized herein, is a ratio of length of the drilled hole to the diameter of the drilled hole. In one embodiment, the L/D ratio is 144:1 or greater. Specifically, in one embodiment, drilled hole125may be a 1/16 inch or less diameter hole with a depth of 9 inches or greater at a L/D ratio of at least 144:1. In other embodiments, the diameter may be less than 5% of the confined dimension. In another embodiment, the diameter can be between 0.25 inch and 3 inches. In yet another embodiment, the diameter can be between 0.75 inch and 3 inches. The hole length may have an L/D of up to 1000:1. In another embodiment, the L/D can be up to 500:1. In yet other embodiments, the L/D can be up to 144:1. Hole diameters correspond to the bit diameter and hole lengths correspond to the length the bit is inserted into the material being drilled.

In other embodiments, the sequence of the process steps described above may be performed in different ways with similar outcomes achieved. For example, the actuated locking collet assembly117may be released and the composite bit119may be fed simultaneous to the linear drive123reversing, such that the composite bit119is kept in a constant axial position in the drilled hole125. Alternatively, a clutch may be engaged while the linear drill drive123reverses, and the composite bit119may subsequently be fed back into the hole after the linear drill drive123has reached a fully retracted position. Additional sequences of operation are possible and may be desirable depending on specifics of the composite bit119utilized, the drilling medium, the properties of the cuttings, and the properties of the surrounding environment.

To enable remote and/or automatic drilling, the compact drill assembly104is tethered to a host PC that enables the operator to send commands to the system via keystroke. All subsystems are controlled by a master microcontroller. While not so limited, the master microcontroller may be an Arduino Mega 2560 or any other suitable microcontroller. The master microcontroller communicates with and coordinates the low-level actions of all the subsystems and associated electronics.

The compact drill assembly104may further include features, equipment, specialized drill bits or other mechanisms to store and/or implant sensors into drilled hole125. For example, in the case of implanting wellbore integrity sensors behind the casing of a wellbore102, sensors may be placed inside the drilled holes125. In order to place the sensors, the compact drill assembly104is lowered to a desired depth of the wellbore along the non-confined dimension105by line107(see for exampleFIG.1). The tethered or wirelessly controlled compact drill assembly104braces itself in place using securing features113and commence the drilling sequence as described above. Once the drilled hole125is formed with a desired depth, either the compact drill assembly104implants the sensor in the drilled hole125or a separate mechanism is lowered into position to implant the sensor. While not so limited, the compact drill assembly104may include a tool changing mechanism, such as tool changing mechanisms in known CNC machine tools or robotic systems to implant sensors into drilled hole125. A sensor implantation tool would be an alternate tool to change from the composite bit119. In this embodiment, during the changing of tools to the tool to implant the sensors, securing features113are kept engaged, so the tool changer would automatically align the sensor emplacement with the drilled hole125. In another embodiment, sensors could be integrated into the drilling process. In this embodiment, a sensor mounted within the compact drill assembly104may be utilized to measure released pressure or gas/liquid flow as the drilled hole125is created. Such a measured release may indicate drilling into a defect that has accumulated pressure.

In other applications, the systems and methods may be used to place sensors at restricted points in structures such as, but not limited to buildings, dams, bridges, piers, mines and mineshafts, caves and caverns, utility pipes and other infrastructure, and any access-restricted environments. In particular, the systems and methods may be used to place sensors to monitor underground or underwater portions of buildings, dams, bridges, piers, or other infrastructure.

In an embodiment, the systems and methods according to the present disclosure permit direct measurements of the casing of the wellbore102(see for example 1 and 10). As shown inFIG.10, wellbore102is surrounded by cement1001and formation1003. Cement1001surrounds the wellbore102between formation1003and the casing of wellbore102. Formation1003is, for example, a rock formation through which the wellbore was drilled. The cement1001and formation1003may include undesirable features such as a micro annulus1005or cement fractures1007. Drilled hole125, formed by compact drill assembly104, includes a space into which one or more sensors may be placed. By placing sensors, either temporary or permanent, in these areas, the presence of micro annulus1005or cement fracture1007may be sensed. The method and system are not so limited and may include other sensors that may sense other features of the wellbore102and the surrounding structure. Positioning of one or more of these sensors may permit initial measurements to be taken from wellbore102to provide gross indications and locations of potential failures. Subsequently, small holes may be drilled, and sensors emplaced to further characterize and localize any damage so that it may be repaired or monitored for further remediation. These sensor access holes must be deep enough to reach the desired depths (typically up to 8-12 inches, and potentially up to 3-4 feet or more), but their diameters must be minimized (typically well below 0.25 inches, and perhaps as small as ˜0.01 inches) to avoid lasting damage to the wellbore102. These small, deep drilled holes125are drilled from inside a wellbore102that may be as small as 6 inches in diameter, far removed (e.g., miles or kilometers down a wellbore) from human operators. In addition, multiple drilled holes125may be formed to provide a sensor array that provide additional data over larger areas within the wellbore102. The arrays and sensor arrangements may further be used to map out locations of where defects are present.

In various embodiments, the sensors may be, but are not limited to stress/stain gauges, acoustic sensors, humidity sensors, pH sensors, temperature sensors, vibration sensors, pressure sensors, flow sensors, chemical sensors, optical sensors or imagers, ultrasound sensors, conductivity or other electrical sensors, radiation sensors, or any combination of the sensors.

In other embodiments, sensor technology may include sensing with the compact drill assembly while drilling, inserting temporarily after drilling, and inserting and leaving as a permanent sensor. In addition, compact drill assembly104may condition the drilled sensing holes for permanent emplacement, and/or repair or plug drilled holes125once temporary sensors have been removed. In another embodiment, a tool changer may be utilized by the compact drill assembly104to transition between drilling, sensor placement, and hole remediation, all referenced to the hole location.

In addition to sensor placement, the systems and methods according to the present disclosure may be utilized for fluid and sample extraction, formation of mechanical features (e.g., location identifiers or anchors), geologic access (e.g., as in fracking) or other processes that benefit from high aspect ratio, small diameter holes formed at remote locations in a confined space.

The methods according to the present disclosure include performing engineering analysis and testing utilizing the compact drill assembly104to support physical limitations of conventional feed systems is disclosed that includes predicting buckling load limits associated with specific hole and drill bit geometries and physical properties, predicting chip loading in drill bit flutes based on distance drilled, drilling properties, and material properties, predicting and monitoring drilling dysfunction based on these predictions and on measurements of the drilling system; and autonomously changing rotary speed, and axial translation speed, force and location to stop the onset of drilling dysfunction.

Vibrations, especially those near harmonic resonance, are a primary cause of drill string failures, resulting in lost time and abandonment of drill holes. Drill bit vibrations are relevant in the lateral, angular, and longitudinal axis of drill bits, and in bits with large aspect ratios lateral and angular vibrational modes appear to be primary contributors to stresses that result in drill string failures. In conventional boring or drilling, the speed of the cutting surface is dictated by the material being drilled. Consequently, the rotational speed is inversely proportional to the bit diameter.

In the above case, the lateral bit deflection can be treated like a cantilever beam, while the torsional deflection can be modeled as a fixed-free shaft. The lateral deflection of the drill bit can be determined from Euler beam theory which can appropriately describe bit wobble

y=∂U∂Fy=[L23⁢EI]⁢Fy(1)
while the angular deflection of the bit is

θ=∂U∂T=[2⁢(1+r)⁢LEJ]⁢T(2)

Factoring out and inverting the bracketed terms in (1) yields the lateral bit stiffness.

ky=3⁢EIL2(3)

With the same done to (2) that results in the torsional stiffness as

kθ=EJ2⁢(1+y)⁢L=GJL(4)

The lateral and torsional stiffnesses of the bit in Equations (3) and (4) can be devised by n number of segments and lumped masses which can then be used for dynamic analysis of the bit. An n-segmented drill bit results in the following equations of motions for the lateral motion
[M]nxn[ÿ]nx1+[K]nxm[y]nx1={F(t)}nx1(5)
and for the angular rotation
[J]nxn{{umlaut over (θ)}}nx1+[κ]nx1={F(t)}nx1(6)
where the vibrational modes can be analyzed by solving for the eigenvalues of the characteristic equation of (5) and (6). By analyzing the natural frequencies, it can be determined if vibrational excitation near natural modes are a relevant issue. All of the natural frequencies move into the operating regime of drilling speeds (hundreds to several thousand revolutions per minute) that typically have lower order modes of natural frequency. In addition to this, high aspect ratios can have large deflections from relatively small loads (from misalignment and/or machining reaction forces) that can be problematic.

Considering lateral deflections and empirical drill force and torque data, the principal stress can be estimated for a variety of different aspect ratios for a constant bit length of 10 inches as depicted inFIG.11, with consideration of a 13 times increase in bending stresses at harmonic resonance.FIG.11shows that increasing aspect ratios for bits see higher principal stresses that are approximately 60% of the yield strength of high-speed steel (HSS). This basic analysis shows that excitations near harmonic resonances may induce failure of the bit material, where at resonance the stresses can increase by over an order of magnitude and can even be further exacerbated by additional loading due to chip clearing.

FIG.12is a schematic of the drill-bit assembly with different cases of plausible models of end conditions as they affect buckling. Case 1 illustrates the drill-bit assembly prior to and when initiating contact where the constraints are fixed-free, case 2 illustrates initial drilling where the constraints are fixed-pinned, and case 3 illustrates when the bit is inside the drill bore which has a fixed-fixed column constraint.

The first scenario (case 1), where the tip is first beginning/prior to contacting the tool piece, the bit has a free end, resulting in the effective length of the column as
L1′=2L(7)

In case 2, the bit end in contact with the tool piece (e.g., in a dimple created by a spot drill) is considered a pin joint, giving a fixed-pin column constraint that has the following effective length in Equation (8).
L2′=0.7L(8)

The fixed-fixed condition for case 3 is defined by Equation (9).
L3′=0.5L(9)

The effective length allows the critical loading of the column to be determined by

Pcr=π2⁢EI(Li′)2(10)
where E is the modulus of elasticity of the bit material, and I is the second area moment of inertia. The technical challenge can be better understood by analyzing the critical load for different aspect ratios. For this, the length of the bit is assumed to be 10 inches, while we sweep the diameter of the bit from 0.025-0.125 inches. The critical loading of the bit for this parameter sweep and effective length conditions are depicted inFIG.13.FIG.13show that aspect ratios greater than 250 with a bit length of 10 inches require less than 1.5 lb force to buckle with the highest aspect ratio case requiring only a few ounces of axial force to cause buckling.

The total torque and force required for drilling is the combination of chip generation torque and force and chip evacuation torque and force. Chip generation loads are independent of depth and can be estimated from tool geometry, formation material, and operating conditions. The chip evacuation loads are a result of friction and back pressure generated between the bit and borehole wall due to chips packing the flute volume. Modeled effects of flute geometry on drilling torque and force show, through modeling and experimental data, that there exists a non-linear increase in both torque and force as the flutes load up with increasing depth. They established a critical depth at which the torque values exceed a threshold based on estimated mechanical failure of the drill bit. This critical depth is used to determine the peck depth of a peck drilling operation. For deep holes, it is noteworthy that even if flutes are extended to the full depth of the hole, to potentially allow for chip clearing while drilling, the drilling torque and force will increase substantially as the flutes fill up, ultimately causing dysfunction or bit failure.

The compact drill assembly104according to the present disclosure has the ability to drill small diameter (0.01 inches-0.25 inches), arbitrarily deep holes. For the compact drill assembly104to overcome the dysfunctions and limitations associated with a standard unsupported drilling operation, the compact drill assembly104includes the ability to incrementally drill with a minimal unsupported drill length.

EXAMPLE

A test specimen fixture was instrumented with a load cell and torque sensor to measure and record the thrust force and drilling torque throughout the drilling operation. A set of drilling experiments was conducted with this instrumented system. For a second set of experiments, the ability of the system to drill deep holes was evaluated with a long (˜9 inches) acetal homopolymer test sample. To accommodate the length of the long test specimen while maintaining a rigid drill setup, the instrumented mounting fixture was removed, and the long test specimen was attached to the bench top linear drive stage with a non-instrumented fixture. For both experimental setups the mechanism performed an incremental drilling sequence, enabling the system to drill while maintaining a minimal unsupported drill length. In addition to the incremental drilling sequence, the mechanism also attempted to perform a “standard” drilling operation with the starting unsupported drill length matching the final desired hole depth. This enabled a performance comparison to standard drilling methods.

To quantify the performance of the system, force and torque time histories from the instrumented experiments are compared and analyzed considering the dysfunctions explored above. The instrumented experiments consist of sequential drill and dwell operations in which the mechanism actively drills forward, stops forward movement, dwells, and continues forward motion. To evaluate the performance of the system, the maximum achievable hole depths from the non-instrumented deep hole experiments are measured and compared.

FIG.14presents the force and torque measurements for both “standard” (with the full drill bit length unsupported) and “mechanized” (using the advancement system) drilling of an acetal homopolymer test sample with a 5/32-inch drill bit. Both standard and mechanized drilling operations successfully drilled the entire depth of 9 inches during the non-instrumented deep hole tests. Considering the testing parameters, none of the dysfunctions discussed in earlier sections would be expected during standard or mechanized drilling of an acetal homopolymer test sample with a 5/32-inch drill bit. As seen in the collected force data, the drilling force throughout standard and mechanized drilling are far below the theoretical critical buckling load presented inFIG.13.FIG.15presents the force and torque measurements for standard and mechanized drilling of an acetal homopolymer test sample with a 1/16-inch drill bit. The standard drilling operation was unsuccessful at drilling at an unsupported length of 9 inches and resulted in buckling of the bit. As seen inFIG.15, during the initial drill the measured force for the standard drilling operation increases until the drill bit buckles. FromFIG.15, it can be seen that the experimental buckling load (˜5 lbs.) roughly matches the theoretical critical buckling load for the fixed-pin case presented inFIG.13. The bit continued to buckle after continual pullback and dwell operations, indicated by the relatively constant average force on the bit as seen inFIG.15. In contrast, the 1/16-inch diameter hole drilled with the custom mechanism was able to successfully transfer the required loads through the bit to facilitate drilling regardless of depth. These drilling conditions enabled a full 9-inch hole to be completed—achieving a ratio of 144:1.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.