Patent Application
20240352803
The present disclosure generally relates to machines that use resonance to transfer energy from the machine to a drill bit or bottom hole assembly to penetrate the earth, concrete, or any material to drill a hole or take a sample.
Generally, sonic drills have used counterrotating eccentrics mechanically timed to generate vertical forces while canceling the horizontal forces. The eccentrics are typically driven directly from an internal combustion engine or by an internal combustion engine driving hydraulics, which have response times longer than the penetration systems response time constant. A throttle controls these systems by engine speed or a valve or driven pump speed.
Hydraulic controls have a slow response time, making the drill hard to control by hand. As the frequency increases and the drill approaches resonance, the system requires less input power, which causes the eccentrics rotation speed to increase. As a result, the system is pulled into the resonant condition. The operator nor the hydraulic system can respond fast enough to avoid speeding up into the resonant peak and remaining on the resonant peak.
What is needed is a resonance-enabled drill with quick response times and finer control so that the drill can stay at the recommended resonance frequency or desired operating condition
The present disclosure provides a resonance-enabled drill, comprising a housing; one or more force generators chosen from one or more voice coil actuators, one or more eccentrics driven by one or more electric motors, or combinations thereof; one or more sonic heads coupled to the one or more force generators; a plurality of springs coupling the housing to the one or more sonic heads; and a drill rod disposed on its proximal end to the one or more sonic heads.
In certain embodiments, the drill further comprises a bit disposed on the distal end of the drill rod.
In certain embodiments, the one or more voice coil actuators comprise a coil assembly rigidly disposed on the housing or on a reflection mass, and a magnet assembly disposed on the one or more sonic heads. In certain embodiments, the coil assembly of each of the one or more voice coil actuators has little to no motion compared to the one or more sonic heads.
In certain embodiments, each eccentric is driven by one electric motor. In certain embodiments, the one or more force generators comprise two paired sets of eccentrics configured to exert no vertical force, using a 180° phase angle between the two paired sets of eccentrics. In certain embodiments, the one or more force generators comprise two paired sets of eccentrics configured to exert full vertical force, using a 0° phase angle between the two paired sets of eccentrics.
In certain embodiments, the drill further comprises a seal disposed between the housing and the drill rod.
In certain embodiments, the drill further comprises a spring-damper disposed between the drill rod and the bit. In certain embodiments, the spring-damper cushions impact of the drill bit by widening and lowering the impulse magnitude, whereby transfer of primary resonant energy to unwanted resonant modes is lowered, and the drill bit is kept in motion and not fused with a workpiece.
In certain embodiments, the drill further comprises an energy transfer rod and flange adaptor disposed between the one or more sonic heads and the drill rod.
In certain embodiments, the drill further comprises a rotor, stator, and stator housing disposed between the one or more sonic heads and the drill rod. The rotor is disposed on the drill string and the stator and stator housing each disposed on the housing, thus allowing the sonic drill rod to rotate. In certain embodiments, this configuration induces torsional resonances when the input force is oscillated on the rotary motor. In these embodiments, between the one or more sonic heads and the adapter, when present, a rotor provide rotation torques onto the pipe. A decoupler/stator can also be between the rotation of the pipe and the one or more sonic heads, which are stationary. In one configuration, the rotor, stator, and stator housing are tied together so that the drill rod does not rotate but can oscillate from the input torque at the rotor.
In certain embodiments, the kinetic energy stored in the drill by the one or more sonic heads is directly offset by potential energy stored within the plurality springs. In certain embodiments, the drill further comprises a reflection mass coupled to the one or more sonic heads through a second plurality of springs and configured to offset the kinetic energy stored in the drill.
In certain embodiments, the housing comprises a plurality of plates and a plurality of standoffs. In certain embodiments, during operation, the drill has a resonance frequency and, when on resonance, an alternating input force is in phase with the oscillation velocity of the one or more sonic heads. In certain embodiments, the oscillating input force is provided from the spinning eccentrics or voice coil force. In these embodiments, the force is not constant but rather oscillates (or alternates) up and down.
The present disclosure also provides a gauge for a sonic drill configured to display information to an operator when the drill is on or near resonance. The sonic drill may be any resonance-enabled drill disclosed herein. In certain embodiments, the information comprises one or more parameters chosen from an amplitude of the drill bit, a resonant frequency of the drill, a stress state, power components of the drill, and safe operating frequencies.
In certain embodiments, the gauge indicates one or more positions chosen from bit decoupling, a lower recommended range, a recommended operating condition, a high recommend range, and fusion. In certain embodiments, the power components of the drill comprise useful power, power delivered at the bit, power absorbed along the drill string's length, energy stored in the drill, and wasted power.
In certain embodiments, the gauge is further configured to display to the operator where mechanical resonance is located compared to operating conditions of the drill.
In certain embodiments, the gauge is further configured to show the ratio of bit motion to motion of the one or more sonic heads.
In certain embodiments, when penetration of the drill slows or ceases, the gauge is configured to display potential problems with options to remedy the lower-than-desired penetration rate.
Any resonance-enabled drill disclosed herein may comprise any gauge disclosed herein.
The present disclosure further provides a method for selecting a resonance frequency in a sonic drill comprising a force generator, one or more sonic heads, and a gauge. The phase is measured between a force generator and one or more sonic heads in the sonic drill. A resonance frequency is selected based on the phase displayed on a gauge to indicate the relative position of the phase for resonance of the sonic drill. In certain embodiments, phase between the force generator and the one or more sonic heads in the sonic drill is measured and resonance on the gauge is displayed to indicates where the resonance frequency is relative to the current operating frequency of the drill based on the phase measurement.
In certain embodiments, when the sonic drill comprises a bit, the method further comprises maximizing the ratio between the bit motion and the motion of the one or more sonic heads. In certain embodiments, when the sonic drill comprises a bit and penetration of the bit is slowed or ceased, the method further comprises reducing the weight on the bit to adjust the resonance frequency of the drill to continue drilling.
In certain embodiments, the method further comprises estimating the stress state of the drill. In certain embodiments, the sonic drill selects the resonance frequency when an operating condition changes. In certain embodiments, the operating condition is chosen from pipe length, the ratio between the drill bit motion and the motion of the one or more sonic heads, weight on the bit, or the workpiece.
In certain embodiments, weight applied to the bit is greater when drilling a workpiece with a lower soil stiffness than when drilling a workpiece with a greater soil stiffness. In certain embodiments, critical weight on the bit is pushed up to allow motion at the drill bit to perform drilling. In certain embodiments, as soil stiffness increases, less weight on bit is required for fusing. In certain embodiments, weight on the bit is inversely proportional to soil stiffness.
In certain embodiments, the weight applied to the bit is great enough to provide fusing with the soil. The bit boundary condition changes from free to fused with the soil. The soil stiffness and viscous damping are now a part of the sonic drill system. The drill system turns into a sensor to measure the soil stiffness and viscous damping at the drill bit.
The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. The drawings provide exemplary embodiments or aspects of the disclosure and do not limit the disclosure's scope.
Table 1 lists reference numerals used throughout the figures and this disclosure.
A “resonance-enabled drill” is a type of resonance-enabled machine, such as a sonic drill or sonic penetration device, within this disclosure. Generally, within this disclosure, “drill,” “sonic drill,” and “resonance-enabled drill” are used interchangeably. In certain embodiments, the drill is configured to function as a corer and can also be referred to as a “resonance-enabled corer.”
Resonance is defined as when an oscillation system over a single oscillation cycle the stored energy of the drill matches the kinetic energy stored in the drill and that results in the force being in phase with the resultant velocity. By the definition of resonance, a person of skill in the art would readily understand how the drill operates. For example, when the system is on resonance, an alternating input force is in phase with the system oscillation velocity of the one or more sonic heads.
To slow a hydraulically driven eccentric system, finer controls may be used for the flow driving the eccentrics. In certain embodiments, an energy-absorbing device, such as a brake or generator, may limit the speed. The system can reduce the input power to keep the input frequency below resonance. Disclosed herein is another method wherein an electric motor drives the counterrotating eccentrics. In certain embodiments, the motor is closed-loop controlled to control the speed. In certain embodiments, a motor brakes the system's speed so that the eccentrics can spin at any desired rate.
The resonance-enabled drills disclosed herein comprise a force generator, such as one or more voice coil actuators or one or more pairs of eccentrics.
Voice Coil actuators
A voice coil actuator commonly drives mechanical systems with linear motion. The coil assembly is disposed on the sonic head because it is lighter than the magnet assembly and losses from the inertia of the oscillating mass prevent the heavier mass from being the sonic head. Examples include loudspeakers to generate sound/music. Care has been taken to reduce the coil assembly's weight mounted to the speaker to provide the best performance with the highest efficiency.
With the coil moving, power wires delivering current to the coil are always being fatigued, limiting the life for the voice coil and the power wires delivering current to the coil. As disclosed herein, the voice coil is mounted to housing to mitigate fatigue and increase reliability. Still, up to now, this configuration caused reduced performance and lower efficiency. By configuring the voice coil assembly in a resonance-enabled drill, the kinetic energy stored in the drill by the voice coil assemblies' moving masses is directly offset by potential energy stored within the drill's springs. Therefore, heavier voice coil assemblies can be mounted on a sonic head of the resonance-enabled drill without losing performance or efficiency.
The one or more sonic heads are configured to operate on a resonant mode shape. The one or more sonic heads are out of phase of one another. Each of the one or more sonic heads is coupled to the housing through a plurality of springs. When more than one sonic head is present, the sonic heads are also coupled with each other through a second plurality of springs. The drill is configured so that the forces transferred to the housing through the coupling springs between the one or more sonic heads and the housing are at or near zero over the drill's operating range around its resonant frequency.
In resonance-enabled drills driven by a voice coil, the range of frequencies can and will vary. A person of skill in the art understands to select a frequency range suitable for operating the resonance-enabled drill under the conditions needed for the selected workpiece. For example, the voice coil may operate between 60 Hz and 2,000 Hz (2 kHz), such as between 60 Hz and 100 Hz, between 100 Hz and 200 Hz, between 200 Hz and 300 Hz, between 300 Hz and 400 Hz, between 400 Hz and 500 Hz, between 500 Hz and 600 Hz, between 600 Hz and 700 Hz, between 700 Hz and 800 Hz, between 800 Hz and 900 Hz, between 100 Hz and 1 kHz, between 1 kHz and 1.1 kHz, between 1.1 kHz and 1.2 kHz, between 1.2 kHz and 1.3 kHz, between 1.3 kHz and 1.4 kHz, between 1.4 kHz and 1.5 kHz, between 1.58 kHz and 1.6 kHz, between 1.6 kHz and 1.7 kHz, between 1.7 kHz and 1.8 kHz, between 1.8 kHz and 1.9 kHz, or between 1.9 kHz and 2 kHz. In certain embodiments, the frequency is greater than 60 Hz. In certain embodiments, the frequency is less than 2 kHz. In certain embodiments, the frequency is between 60 Hz and 250 Hz, such as between 60 Hz and 150 Hz.
Optionally, the resonance-enabled drill 100 further comprised a spring-damper 620 disposed between the drill rod 600 and the bit 630. The spring-damper 620 widens or flattens the impulse load from the drill bit 630. For example, if a resonance-enabled drill 100 made of only steel impacts a rock formation 700, the formation has infinite impedance and reflects the impact fully onto the drill rod 600. The impact creates an impulse load and excites all resonant frequencies of the resonant system. With repeated blows, the energy quickly transitions from the primary resonant mode to a broadband of resonant frequencies, fusing the drill bit 630 with the formation 700.
By disposing a spring-damper 620 (with or without internal damping) between the drill bit 630 and the drill rod 600, the bit 630 can move with the end of the drill rod 600 during normal operation. When a hard substrate is encountered and impulse loads are generated, the spring-damper 620 cushions the impact by widening and lowering the impulse magnitude. This lowers the transfer of the primary resonant energy to unwanted resonant modes, keeping the drill bit 630 in motion and not fused with the strata 700. The bit's 630 susceptibility to fusing is lessened, the useful range of weight on bit 630 is widened, and the acceleration force and energy onto the bit 630 are lessened during drilling, causing less wear and extending the service life.
In certain embodiments, the spring-damper 620 comprises a resilient member, such as a spring or a viscoelastic medium. The damping within the spring-damper 620 is rate-dependent. When present, the spring gives. The load through the transient impact transfers by the damping or viscous part of the viscoelastic medium.
Referring to
In certain embodiments, the resonance-enabled drill further comprises an energy transfer rod 640 and flange adaptor 650 disposed between the sonic head 210 and the drill rod 600. In this configuration, the seal 610 is disposed between the energy transfer rod 640 and the housing 300.
Standoffs provide strength and rigidity to the machine. Separate resonant modes do not occur within the machine's structure. For instance, each sonic head 200 is assumed to be a rigid body, and the standoffs 350 ensure that each mass acts as a rigid body during machine operation. The number of standoffs in the plurality can be selected to accommodate the size of the machine, such as between 1 and, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, or 100. A large machine typically contains more standoffs than a smaller machine for strength and rigidity. Each standoff 350 is matched with springs 410 and fasteners 351, so as the number of standoffs 350 increases, so do the number of springs 410 and fasteners 351.
The second sonic head 220 is coupled to the housing 300 via a plurality of housing-to-second sonic head springs 420 and the first sonic head 210 by a plurality of first-to-second sonic head springs 430. The second voice coil assembly 520 is disposed on the bottom surface of the housing 300 inside the drill 150, pointing in the opposite direction of the first voice coil 510. The second voice coil assembly 520 is coupled to the second magnetic assembly 525. If the housing springs 410,420 are not completely offset, they can be adjusted to cancel the resultant forces to the housing 300.
In certain embodiments, the force generator comprises one or more eccentrics. In certain embodiments, a motor drives each eccentric. In such embodiments, the motors are electrically synchronized. When a primary signal is generated, both motors are controlled by the primary signal. These motors counterrotate in relation to each other. Electric motors have not been used previously because the control system for electrically controlling motors to sync to one another has just recently been achieved. The industry has not understood that the current operating conditions are not recommended and could be improved using electric motors. One favorable operating condition is identified. It is often found below resonance, where the ratio of drill head motion amplitude over drill bit motion amplitude is minimal.
The drill bit generally moves more than the sonic head, permitting a higher transfer of power to the drill bit to drill. The drill may be unstable at this location and need less energy than at lower frequencies. The drill eccentrics rotational speed may increase, and the system is pulled through the favorable operating point. Therefore, with current technology, sonic drills may not be able to operate in such conditions.
In certain embodiments, the resonance-enabled drill comprises double eccentrics, such as four in total, with phase control.
In certain embodiments, the resonance-enabled drill comprises two sets of counterrotating eccentrics. Each set spins at the same frequency, with one set, phased differently from the other set. In certain embodiments, at startup, the eccentrics are driven at 180° out of phase from one another, which cancels all vertical forces. The vertical force amplitude is adjusted by changing the phase between the two sets of eccentrics. As the eccentric's phase approaches 0°, the force approaches 100% force, which is the total force of the four eccentrics (m*r*ω2), where ‘m’ is the mass of the eccentric, ‘r’ is the distance from the center of rotation to the center of mass of the eccentric, and ‘ω’ is the angular speed of the eccentric rotation.
Commercially-available eccentric-driven drills use one set of eccentrics and operate at full force. In certain embodiments, the drill comprises a knob which an operator can use while drilling to adjust the input force amplitude to the drill. The operator can operate on or near resonance and then adjust the input force amplitude until the desired operating conditions are met. The adjustment of the input force amplitude changes the phase between the two pairs of eccentrics. The desired operating conditions include, but are not limited to, head acceleration, bit acceleration, input power, stress state within the system, penetration rate, energy transferred into and stored in various sub-systems, etc. The acceleration is related to the displacement, velocity, and jerk through the frequency of oscillation, and any of these can also be used. The stress state in the system can be maximum, mean, amplitude, etc.
In certain embodiments, torsional modes for the drill string use a rotary motor as the torsional driver. The torsional resonant modes are similar to the axial resonant modes. During operation, the torsional motor drives the oscillations at different frequencies, permitting the bit to impact at different rotational locations with each blow. The buttons on the bit hit virgin material and did not impact the same location. Also, the rotation oscillation acts as a paddle to loosen materials, such as clays, and move the loosened materials during drilling.
In certain embodiments, the drill comprises two classes of force generators, wherein the one or more voice coil actuators are tuned to a first frequency range and the one or more eccentrics are tuned to a second frequency range.
When drilling in soil, such as non-cemented clay, sand, and the like, the most common configuration for geotechnical drilling, the drill bit is selected accordingly. In these embodiments, the drill bit comprises tungsten carbide, steel with tungsten carbide inclusions or pellets, or the like. In certain embodiments, the drill bit is configured with an aggressive geometry to tear off and remove soil.
When encountering a boulder or hard layer, the conventional drill bit will be unable to progress and wear off rapidly. The sonic bit plug is a downhole wireline tool that latches into the bottom hole assembly (BHA) and expands underneath the conventional drill bit to the full string diameter or slightly more. Sonic motion is activated, and the pushdown force is applied to the drill string. The borehole can be progressed over a short penetration without rotation or circulation.
The sonic generator can be powered with air or fluid pressure or electric power.
In certain embodiments, rotation may remove the cuttings underneath the bit. The whole string can be gently rotated with a wireline bit-plug inside. Alternatively, the sonic bit plug could include a rotation capability, such as powered by electricity or air.
In certain embodiments, circulation cools the drill bit and evacuates the cuttings from the borehole. When present, circulation may be achieved through reverse circulation by injecting air at the bottom but inside the drill string at the top of the sonic bit plug. Reversed circulation is effective but may generate static pressure in the borehole slightly lower than the ambient hydrostatic, destabilizing the borehole. Reversed circulation cannot be applied to some types of soils, such as sand or highly fragmented rock. In certain embodiments, the sonic bit plug is pulled out of the borehole, and the borehole is cleaned up by gentle rotation with low Weight on Bit (WoB). In this instance, conventional fluid circulation and reaming may also be performed.
Commercially available drills have digital displays or analog displays that give the drilling operator the drill frequency and head acceleration but cannot be configured to display the resonance state. In certain embodiments, the resonance-enabled drill comprises a gauge configured to display information to the operator when the drill is on or near resonance. To be clear, the gauge continuously displays information, not just when the drill is on or near resonance. The gauge can indicate to the operator when the drill is operating on or near resonance. For example, the gauge displays to an operator where mechanical resonance is located compared to operating conditions of the drill. In certain embodiments, the drill is no longer at resonance and the gauges displays information on the stress state and safe operating conditions of the drill. In certain embodiments, the display comprises a list or visual cues of the current system setup's resonant frequencies. In certain embodiments, the display is digital, analog, or a combination thereof.
Commercially available drills do not indicate what the bit is doing. In certain embodiments, the resonance-enabled drill comprises a gauge configured to display the amplitude of the drill bit to the operator. The higher the drill bit motion, the better penetration. In these embodiments, the drill shows the bit amplitude to the operator. In certain embodiments, the resonance-enabled drill further comprises a secondary gauge configured to show the ratio of bit motion to the sonic head motion. In many situations, the operator is recommended to maximize this ratio. Commercially available drills only present the penetration rate and sound to the operator to describe the drill's vibratory state. These indicators are misleading because the sound is only generated by motion at the sonic head and is not a good indicator of bit motion.
Based on system parameters and the operating conditions, stress states are also estimated and configured to display on a gauge for the operator in certain embodiments. Failures are common because the readout to the operator is only at the sonic head. Still, with various drilling conditions, bit and bottom hole assembly configurations, and lengths and geometry of pipes, the stress states change. Therefore, the same amplitude of motion at the sonic head can generate drastically different stress conditions below ground.
The displays in commercially available drills show the total power delivered to the sonic head for performing work. The total power is broken into real and reactive power. The real power is what the system uses to do work, such as drilling. The reactive power drives the drill bit may be unused and reflected onto the driver, causing high power input. In certain embodiments, the resonance-enabled drill is configured to display the power components of the drill to the operator. These components include, but are not limited to, useful power, power delivered at the bit, power absorbed along the drill string's length, energy stored in the drill, and wasted power (reactive power).
During penetration, the drill bit may become a node, coupled with and fused to the workpiece. As the resonant condition changes, the resonance-enabled drill has a fixed node at the bottom of the string. When this occurs, the drill bit motion goes to zero or near zero, and penetration stops. When the penetration slows or ceases, the resonance-enabled drill is configured to display potential problems with options to remedy the lower-than-desired penetration rate. For example, when penetration is slowed or ceased, the resonance-enabled drill is configured to indicate to the operator that the weight on the bit should be reduced. In other saturations, the resonance-enabled drill may indicate when the weight on the bit is too great, causing potential fusing of the bit or damage to the workpiece if a sample is being taken. This indication may include a shift in the resonant frequency or be calculated from the drill's measurements. A list of resonant frequencies with the bit fused to the bottom also helps the operator because those are the resonant frequencies to operate on if the operator does not know what they are.
Based on the drilling configuration and system, the resonance-enabled drill is also configured to display safe operating frequencies for the operator in certain embodiments. If the operator tries to operate outside the safe operating ranges, then the resonance-enabled drill indicated such to the operator.
The sonic drill is a resonant system. When the system is operated on mechanical resonance, the system has a low impedance, which means it has a high resultant output compared to the input. The low impedance, allows the system to become a sensor and the system can be monitored through measurements than can be used to calculate changes in the boundary conditions, energy absorption, and damage to the system. An example, is when a force is applied at the sonic head that applies a very large weight on bit. The very large weight on bit is enough to fuse the bit with the soil. The boundary condition changes based on the new boundary condition at the bit. There will be a new resonant frequency based on the soil stiffness at the drill bit. The systems new measured phase between the input force amplitude and the resultant head acceleration oscillation can be used to calculate the soil stiffness at the drill bit.
The preceding description is given for clearness of understanding only. No unnecessary limitations should be understood, as modifications within the disclosure's scope may be apparent to those having ordinary skill in the art. Throughout the specification, where compositions are described as including components or materials, it is contemplated that the compositions can also consist essentially of, or consist of, any combination of the recited components or materials, unless described otherwise. Likewise, where methods are described as including steps, it is contemplated that the methods can also consist essentially of, or consist of, any combination of the recited steps, unless described otherwise. The disclosure illustratively disclosed herein suitably may be practiced in the absence of any element or step which is not specifically disclosed herein.
Referring to
Testing was performed on a GeoProbe™ 8150 LS using 40 ft of 4″ drill pipe and a coring bit. The coring was performed in a riverbed with various sizes of gravel, boulders, and sand. If too much weight was added to the bit by drill pipe, head weight, or push down force fusion was initiated at the bit.
In
A gauge displays the difference between phase estimate from the model for the no coupling at the bit and the actual measurement. As the phase deviates, the gauge moves based on the coupling caused by the weight on the bit. The gauge has a cutoff between 5 and 45 degrees for the critical weight on bit. The gauge has a green zone between 0 and 45 degrees and, on some applications, a yellow zone between a value between 0 and 45 degrees and 45 degrees. After 45 degrees or the determined cutoff for the critical weight on the bit, the gauge will be red, indicating that the controller has exceeded the critical weight on the bit.
Referring to
where msh is the mass of the sonic head, cds is the damping at the sonic head, kas is the spring rate at the sonic head, Fo is the input force amplitude, ωf is the input angular frequency of the input force, t is the time, u is the motion at any point along the x-axis, Eds is the elastic modulus of the drill string, and Ads is the cross-sectional area of the drill string.
The boundary condition at the bit end of the drill string comprised the bit mass and strata coupling internal force, strata damping force, and strata restoring force. The bottom boundary condition can be expressed as Equation 2:
where mdb is the mass of the drill bit, cdb is the damping at the drill bit, kdb is the stiffness at the drill bit, and Lds is the length of the drill system.
The spring rate at the drill bit was minimal when the bit was free. The resonant frequency was lowest compared to when the bit interacted with the soil. Assuming different soil types of dense sand (1250 lbf*in−3 (3.38×108 N*m−3)), extremely stiff clay (4680 lbf*in−3 (1.27×109 N*m−3)), and granite (rock, 1.58×106 1bf*in−3 (4.28×1011 N*m−3)). The equivalent spring rate onto the bit was the values above multiplied by the bit frontal area.
The phase between the input force at the sonic head and the resultant acceleration of the sonic head was measured. The critical weight on the bit was defined when the weight onto the bit during oscillation coupled with the soil/strata being drilled and the boundary condition at the bit changed because the soil stiffness acted onto the bit. If the bit were suspended, the bit impacted the soil/strata and did not couple but instead received quick transient impulses from the short contact with the strata each cycle. If the sonic drill were operating under the critical weight on the bit, the drill had equivalent phase readouts as the model without spring coupling at the bit for the drill during drilling operations. As the bit started to interact enough with the soil, where the soil stiffness acted as a boundary condition onto the sonic drill system at the drill bit, the resultant phase started to shift.
A commercial sonic drill has been modeled with 40 feet of drill pipe, a 2-foot stub, and a drill bit on the end. The sonic drill modeled with a minimal spring rate on the drill bit provided a measured phase reading similar to FIG. 34. At −90° of phase difference between the input force and the resultant acceleration at the sonic head, the system is on mechanical resonance (Point A on
When the weight on the bit was too great, the bit coupled with the soil or strata. The soil stiffness influenced the bit. If the weight on the bit was very great, the bit fully coupled to the soil or strata, and the soil stiffness acted as a spring on the bit. Here, the bit fused onto the soil and became a node. This transition took the bit from a freer boundary condition to a fixed boundary condition. If the soil or strata is rock, the soil stiffness is so great that it allows no motion at the bit.
If the soil is dense sand and enough weight on bit is applied that the drill bit is fused with the soil so that all the soil stiffness is pushing on the drill bit, then the boundary of the system changes and the measured phase changes based on the soil stiffness. At the point of fusing with dense sand, the measured phase reads −46°, shifted from Point A to Point B in
With stiff clay, the resonant frequency can shift from 104.5 Hz to 112 Hz, and the phase measured at 104.5 Hz now drops to −10°, a shift from Point A to Point C in FIG. 34. Hard rock is an extreme case. If drilling through granite, the phase will shift above the 150 Hz operating range of the drill, and the phase will be within 10° of −180° out of phase, which is the case when the system is very far from mechanical resonance, shift from A to D in
From these plots, with soils with lower soil stiffness, sands, and low stiffness clays, the weight applied to the bit can be greater than the systems with large soil stiffness, high stiffness clays, and rock. Because the system behaves similarly with the low weight on the bit with the low stiffness clays and sands, whereas pushing up to the critical weight on bit allows motion at the drill bit to perform drilling, and the system performs as intended with a free boundary condition at the drill bit. However, with stiff clays, the weight on the bit needs to be more closely monitored. After all, it can become fused, and then the drill will be in a refusal state where the bit cannot move because it has fused to the boundary condition. The resonant condition has shifted, but the resonant condition is the new boundary condition where the bit is fused with the strata, making it impossible to uncouple the drill bit from the strata once fusing has. As the soil stiffness increases, less weight on bit is required for fusing. Therefore, less weight on bit should be used when drilling through stiff clays than sands and even less weight when drilling through rock than clays.
If the weight on bit is intentionally applied large enough to provide fusing of the drill bit to the soil, then the drill system may be used as a sensor to detect the change in system response of phase difference between the input force and the resultant acceleration at the sonic head to determine the soil stiffness. In
The practice of a method disclosed herein, and individual steps thereof, can be performed manually and/or with the aid of or automation provided by electronic equipment. Although processes have been described concerning embodiments, a person of ordinary skill in the art will readily appreciate that other ways of performing the methods' acts may be used. For example, the order of various of the steps may be changed without departing from the method's scope or spirit unless described otherwise. Some of the individual steps can also be combined, omitted, or further subdivided into additional steps.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination. All patents, publications, and references cited herein are fully incorporated by reference. In case of conflict between the present disclosure and incorporated patents, publications, and references, the present disclosure should control.
This application claims the benefit of the filing date as a divisional of U.S. patent application Ser. No. 17/690,450, filed on Mar. 10, 2021, and also claims the benefit of priority of the U.S. Provisional Patent Application Ser. No. 63/159,435, filed on Mar. 10, 2021, the disclosures of which are incorporated by reference in their entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63159435 | Mar 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17690450 | Mar 2022 | US |
| Child | 18645754 | US |
