Patent Application
20190100965
This invention generally relates to a device, apparatus, and method that provides vibrations from oscillation within and throughout the device. The device is designed so that oscillatory movement can be provided in and along a drill string to overcome static friction downhole. The device is a downhole vibrational oscillator that utilizes the flow of a fluid flowing within a borehole. More specifically, the vibrational oscillator utilizes a shuttle valve assembly that controls fluid flow through a flow diverter using one or more springs that can absorb and later release energy from the fluid flowing in the downhole direction. This downhole flowing fluid, is normally an incompressible fluid (e.g. a liquid such as drilling mud) which when suddenly interrupted, often initiates a water hammer effect through a drillstring in a borehole.
Numerous references describe tools located above a drill bit in a drillstring for periodically interrupting all or most of the drilling fluid flow to the bit. Water hammer (or, more generally known as a fluid hammer) is a pressure surge or wave caused when a fluid (usually a liquid but could also be a gas) in motion is forced to stop or change direction suddenly (which is a sudden momentum change). A water hammer commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe. This phenomenon is also known as “hydraulic shock”.
This pressure wave can be catastrophic depending on its magnitude, often causing major problems downhole. In addition to noise and vibration, which can interfere with and disrupt downhole communication and drilling devices, the pipe or associated pipeline sections could actually collapse. It is possible to reduce the effects of the water hammer pulses by using tools such as accumulators, expansion tanks, surge tanks, and other devices.
Rough calculations can be made either using the Joukowsky equation, or more accurate calculations using the method of characteristics. Specifically, the fundamental equation in water hammer theory relates to pressure changes, Δp, and to velocity changes, Δv, based on fluid flow in a cylinder according to the relationship:
Δp=ρcΔv (1)
where ρ is the fluid mass density and c is the speed of sound.
Korteweg's (1878) formula defines for fluid contained in cylindrical pipes of circular cross-section as:
c=√K*/ρ and K*=K/[1+DK/(eE)] (2)
where D is the diameter of the pipe, e is the wall thickness, E is the modulus of elasticity for the wall, and K is the bulk modulus of the contained fluid.
Relation (1) is commonly known as the “Joukowsky equation”, but it is sometimes referred to as either the “Joukowsky-Frizell” or the “Allievi” equation.
These (water hammer) tools fall into three general categories, based on their intended application.
The first category includes hammer drills that periodically divert drilling fluid flow to cause reciprocation of the drill bit against the bottom of the borehole. This concept was first presented by Wolski in his 1902 U.S. Pat. No. 699,273. More recent developments in downhole hammers by SDS Pty. Ltd. and Novatek Inc. are described in U.S. Pat. No. 5,803,188 (McInnes, 1998); U.S. Pat. No. 5,396,965 (Hall et al., 1995); and U.S. Pat. No. 5,222,425 (Davies, 1993).
The second category includes measurement-while-drilling (MWD) systems that interrupt fluid flow to the bit to generate mud pulses in the fluid column to facilitate telemetry signals transmitted from the downhole equipment to receiving systems on the surface. An early form of this type of system is described by Jakosky in U.S. Pat. No. 1,963,090 (1934). Many patents have been granted since then that utilize mud pulse telemetry in some form.
A third category of tools interrupts flow to the bit causing pressure fluctuations in the borehole at the bit face that enhance drilling efficiency. It is clear that the third category of tools provides a substantial benefit, and it would be desirable to provide further apparatus and a method based on interrupting flow to the bit to generate pulses so as to enhance drilling efficiency.
The benefits of interrupting all or most of the drilling fluid flow to the bit for the purpose of creating pressure fluctuations or pulses in the borehole are well understood and are described in references such as those noted above. These benefits include the following points:
For the present invention, oscillation and agitation is caused primarily by a shuttle valve that can also operate as a pulse generator. The valve operates by both utilizing and providing pressure fluctuations in the vibrational oscillator tool to enhance the action of one or more springs, which cause the oscillation and agitation.
Another class of tool that has been used, is a pilot-operated poppet valve. In a pilot-operated valve, fluid drives a pilot valve that controls the action of a main poppet valve, which provides a more positive valve action that is self-starting and regulated by the timing of fluid ports in the valve. The use of this type of valve to produce negative pressure pulses in the borehole is described in U.S. Pat. No. 6,237,701 (2001), in which Kollé et al. describe various embodiments of a pilot valve/poppet valve based downhole hydraulic impulse generator for borehole applications, the disclosure and drawings of which are hereby specifically incorporated herein by reference. The primary benefits of the hydraulic impulse generator are associated with the rapid reduction in borehole pressure under the bit. The benefits of this negative pressure pulse for drilling as described in U.S. Pat. No. 6,237,701 include:
Additional applications of the negative pressure pulse in borehole applications other than drilling include:
The rapid reduction of borehole pressure that occurs in the invention described in the patent is accomplished by providing a flow of low compressibility fluid, such as water or drilling fluid, through a conduit in the borehole and momentarily blocking the fluid flow with a pilot-operated poppet valve that reciprocates between open and closed positions. If the poppet valve closes in a time that is equal to or shorter than the two-way travel time of an acoustic wave in the annulus between the conduit and borehole, a negative impulse pressure is generated in the borehole beneath the discharge of the conduit. The annular flow passage may be restricted to increase flow velocity in the annulus and increase the magnitude of the resulting negative impulse pressure. If the tool is used for drilling, the length of the restricted flow area may be limited to be less than 1.5 meters to reduce torque. In this case, the two-way travel time of an acoustic pressure pulse in the restricted flow annulus is about 2 milliseconds. The poppet must therefore close completely in less than 2 milliseconds for the tool to be completely effective. The poppet valve is dynamically unstable; when closed, it is energized to open, and when open, it is energized to close. A pilot spool directs drilling fluid to either side of the poppet spool to energize it. The pilot spool is also dynamically unstable. As the valve oscillates between open and closed positions, the passages in the poppet spool direct drilling fluid to either end of the pilot spool to energize it from one position to the other. The pulse generator valve self-starts from any position and runs at a frequency determined by the flow rate of drilling fluid through the valve mechanism.
One embodiment of the valve disclosed in U.S. Pat. No. 6,237,701 is incorporated in a drillstring within a housing including high speed flow courses. The valve closes in about one millisecond. Valve closure stops the flow of drilling fluid through the bit and through high speed flow courses in the housing around the bit. Stopping the upwards flow of drilling fluid through the flow courses generates a negative pressure pulse around the drill bit. This patent discloses that the valve closing time must be less than the two-way travel time of a pressure wave in the flow courses so that an intense negative pressure is generated below the bit. The valve disclosed in U.S. Pat. No. 6,237,701 can provide pulse amplitudes of from about 500 psi to about 1500 psi, with a cycle rate of from 15 to 25 times per second.
Although the relative locations of the pilot and poppet spools are not claimed with specificity in U.S. Pat. No. 6,237,701, a preferred embodiment described therein and early working models are configured with the pilot and poppet spools vertically in-line and physically separated from each other in interconnected housings. The in-line configuration requires multiple long intersecting passages to carry drilling fluid to and from the pilot and poppet spools. Transverse cross-port passages are required for interconnecting the various axial fluid passages. These cross-port passages are plugged from the outside to seal the internal pressure. Multiple sealing elements are required to seal the interconnecting fluid passages between housings.
While functional, the in-line configuration is extremely complex and is correspondingly difficult to manufacture and assemble. The housings are difficult to align, and the seal elements between the housings are prone to premature failure, particularly in the unforgiving environment associated with drilling operations. The long, interconnecting fluid passages and cross-drilled holes are subject to rapid erosion by the drilling mud at each change of flow direction. The valve is also subject to large pressure drops due to fluid friction through the long, complex passages. It would thus be desirable to provide a shuttle valve with springs that can be loaded for enhancing oil and gas drilling by overcoming static friction and also capable of providing pulses and that does not suffer from the disadvantages of the embodiment described in U.S. Pat. No. 6,237,701.
It would also be desirable to provide a drill tool that can enhance drilling performance and act as a tool for providing pulsing and overcoming static friction downhole.
Those skilled in the art will recognize that an ideal seismic source for profiling, reflection imaging, or refraction studies should include a point source and have a broad bandwidth. A broadband signal may be generated by a single impulse source, by sweeping a sinusoidal source over a broad range of frequencies, or by generating multiple impulses with a cycle period that varies over a full octave. It would also be desirable to provide a drill tool that can both enhance drilling performance and act as a seismic source for SWD (seismic-while-drilling), providing a broad range of frequencies, to more readily facilitate the imaging of formations ahead of the bit.
The use of a swept impact seismic technique for surface applications using a mechanical impact tool with a variable cycle rate has been suggested before (Park, C. B., Miller, R. D., Steeples, D. W., and Black, R. A., 1996, Swept Impact Seismic Technique (SIST) Geophysics, 61 no. 6, p. 1789-1803). Varying the rate of a pure impulse signal over a full octave generates a continuous broadband signal. The received signal can be cross-correlated with the impact signal to generate a seismic record with high signal-to-noise ratio. The signal-to-noise ratio can be increased substantially by operating the source over a long period of time. U.S. Pat. No. 6,394,221 (Cosma, 2002) discloses a technique and apparatus for generating a swept impact axial or radial load at the bottom of a borehole using an electrically actuated hammer. This tool is designed to be clamped in a borehole at various depths for seismic profiling.
A number of references disclose variable frequency downhole seismic sources. For example, U.S. Pat. No. 4,033,429 (Farr, 1977) describes a drillstring with a sleeve containing a helical pattern of holes that periodically align with holes in the drillstring. Rotation and translation of the string through the sleeve create a signal that sweeps over a broad range of frequencies up to 80 Hz, depending on the drillstring rotation speed. Significantly, the apparatus described in the Farr patent requires an interruption in the drilling process to actuate the tool. U.S. Pat. No. 6,094,401 (Masak et al., 2000) describes the use of a downhole MWD mud pulse telemetry system to generate a sinusoidal frequency sweep over a range of frequencies from 1 to 50 Hz. Masak's device uses an electric motor to drive a rotor at variable rotation rates. The rotor interacts with a stator to restrict the mud flow to the bit. Restricting the flow generates axial shaking loads of up to 3000 lbs. These loads are transmitted through the bit to the formation. The coupling between the bit and the formation is limited by the relative axial stiffness of the drillstring and the reference discloses the use of a thruster subassembly to increase coupling. As with drill bit seismic, axial shaking of the drillstring generates primarily a dipole signal that propagates along the borehole axis. Seismic receivers must therefore be located near the drill rig, which is a source of substantial masking of seismic noise.
A number of options have been studied for generating a strong seismic signal while drilling. Most options involve stopping the drilling process to actuate a downhole source such as a piezoelectric vibrator, hydraulic or mechanical jarring tools, or dropping the drillstring. All of these options interrupt the drilling process and increase the potential for borehole instability. Frequent drilling interruptions would not be an acceptable practice for most operators.
Prior SWD techniques result in low signal-to-noise ratios, and the resulting signals require substantial processing and interpretation. It would also be desirable to provide a broadband high-amplitude SWD source that enables unambiguous real-time interpretation of formation velocity and reflections ahead of the bit.
The present disclosure describes a vibrational oscillator comprising; a shuttle valve assembly disposed along the length of and within a casing wherein the shuttle valve assembly comprises at least a plunger, a receiving assembly, a cavity, and a valve, residing within the shuttle valve assembly within which fluid can flow into and out of the shuttle valve assembly and a conduit with an inlet port and an outlet port through which fluid can flow into an upstream section of the oscillator toward and out of a downstream section of the oscillator with at least one fluid passage configured to selectively couple in fluid communication with the inlet port and the outlet port through which fluid passes;
such that the plunger is capable of receiving fluid and fits into the receiving assembly and the shuttle valve assembly is sealed so as to always allow at least some volume of the fluid to enter or escape the cavity;
and the oscillator includes the plunger that can be at least partially positioned within the receiving assembly to at least partially interrupt fluid flow through the conduit which is in contact with and allows for movement of a fully assembled oscillator component of the oscillator and provides compressive forces that compress at least one spring or set of springs from the receiving assembly and eventually releases the compressive forces when the plunger is removed from the receiving assembly thereby providing for expansion of the springs so that oscillations within the springs located along and/or within the casing are created.
The casing is a cartridge assembly that houses the d oscillator.
The plunger that is disposed within the shuttle valve assembly is actuated by pressurized fluid so that the valve can cycle between an opened position and a closed position, such that when in the closed position, the plunger at least partially interrupts a flow of the pressurized fluid through the outlet port; and such that the plunger reciprocates back and forth between at least a first and a second position during cycling of pressurized fluid into and through the oscillator such that position of the plunger controls fluid into and out of the inlet port of the valve thereby causing a variable force to act on one or more set of springs resulting in oscillations of the springs.
The oscillator is an agitator in that the oscillator causes vibrations that vibrate within the oscillator causing agitation along at least a portion of a drill string and thereby overcomes static friction downhole.
A first aspect of the present disclosure provides an agitator that requires the control of a shuttle valve that when opened and closed causes movement within a device designed to provide vibrations along a drill string due to oscillations from internal springs. The valve is a leaky shuttle valve in that the plunger, disposed coaxially within the cavity of the cartridge, includes the leaky shuttle valve that does not fully open or fully close during operation. In some cases, the at least partial interruption of fluid flow occurs without generating an upstream positive pressure pulse or water hammer pulse associated with prior flow pulsing apparati.
The oscillations of the springs occurs along a longitudinal direction and become self-oscillating after an initial oscillation is initiated due to operation of the shuttle valve assembly.
In at least one embodiment, an extreme upstream positive pressure pulse (water hammer) is avoided by providing a shuttle valve configuration with a plurality of fluid passages that include at least one fluid passage configured to divert a flow of pressurized fluid upstream of the outlet port when the plunger is in an open or closed position, thereby substantially reducing a water hammer effect, that enables an incompressible fluid to continually flow into the valve through a flow restrictor into an inlet port and subsequently flow from the valve through an outlet port or through a drain port.
At least one fluid passage includes:
(a) a fluid passage through which pressurized fluid is applied to the plunger to cause the plunger to cycle toward a closed position, thereby partially closing the outlet port, when the plunger is in a first position;
(b) the same or a different fluid passage through which pressurized fluid is applied to the plunger to cause the plunger to shift to the second position and;
(c) a same or different fluid passage through which the pressurized fluid is applied to the plunger to allow the plunger to cycle back toward an initial position thereby defining a cycle time of the valve.
The cycle time of the valve is a function of a size of the at least one fluid passage and the cycle time required for the plunger to cycle between the open position and the closed position is less than or equal to a two-way travel time of an acoustic pressure wave in a length of the casing.
The plunger is configured to move with the receiving assembly when the plunger is in a first position, such that when the plunger moves from an open position to a closed position, a momentum imparted to the plunger facilitates compression of at least a pilot of the shuttle valve that shifts the valve toward either an open or the closed position.
The plunger can be a ball, a poppet, or other geometrically symmetrical device that at least partially seals the shuttle valve so that fluid can enter and exit the cavity within the valve.
The valve is comprised of a housing in which the valve is disposed, wherein the housing is adapted to be incorporated in a drillstring and configured to isolate a section of the casing such that an at least partial interruption of pressurized fluid in the casing by the valve generates a negative pressure pulse in the section of casing wherein the negative pulse is isolated, propagating away from the valve.
The rapid reduction or total interruption of flow of the pressurized fluid through the valve outlet produces large oscillations in the springs and can result in large vibrational agitation, which if controlled in the proper manner, can cause pressure pulses in the drilling fluid or drilling mud.
The vibrational oscillator which provides agitation along the drill string has the following advantages and related benefits;
The frequency and modulation of the vibration-induced (vibrational) oscillations of the agitator of the present disclosure has several advantages and related benefits for overcoming static friction and providing seismic type sources compared with other apparatus and methods. For example, the vibrational oscillations provide agitation and possible seismic sources independent of the drill bit employed.
Pulses from the shuttle valve produce an omnidirectional radiation pattern, making it particularly attractive for deviated wells and horizontal drilling, where SWD data can be critical for bit steering applications.
The oscillations and associated vibrations can be controlled to produce seismic signals by controlling the shuttle valve precisely and thereby producing pulses that are highly coherent. This is particularly true if the agitator is located near the point where the bit meets the end of the hole when the shuttle valve is disposed on the drillstring proximate the drill bit. This configuration enables higher resolution geological data to be obtained.
Throughout the present disclosure, the words vibrational oscillator refers to a device that causes agitation downhole. As such, the agitator (vibrational oscillator) as a cartridge contained tool functions continuously and can be fitted with an optional pressure controlled on/off mechanism to prevent oscillations and consequent vibrations from cycling until a preset pressure for controlling the shuttle valve is reached. When the on/off mechanism is in an off position, the plunger is held in the open position, preventing the valve or the vibrational oscillator from cycling;
wherein the on/off mechanism is sensitive to a pressure in the casing, such that the on/off mechanism changes from an off position to an on position after the pressure within the casing reaches a preset level.
The valve further comprises a frequency modulator configured to repeatedly vary a cycle rate of the valve;
wherein the frequency modulator utilizes a variable volume in fluid communication with a timing shaft, the timing shaft being coupled with the plunger, such that a change in the variable volume produces a corresponding change in a motion of the plunger, thereby changing the cycle rate of the valve.
In this case, the words “agitator” and “vibrational oscillator” refer to the same device.
The agitator can be implemented as a purely hydraulic-mechanical device that is powered by the drilling fluid normally used within drilling operations. No other energy source or control logic is required. Also, no downhole electronics, programming, gears, or electric motors are required, although the use of such devices/systems is not excluded.
True SWD functionality can be achieved with the oscillator and tripping or interruption of operations is not required to obtain data. Most other seismic sources require drilling operations to be interrupted to obtain seismic data. In many hard rock formations, the pressure pulses generated at the bit will enhance drilling operations by increasing drilling rate and reducing improper bit motions such as stick-slip, and whirl.
Unlike bit sources, the seismic signals from the oscillations and resulting vibrations generated by the present invention can be discrete pulses that vary in frequency in a regular pattern. Since the source can be operated continuously, data can be stacked to enhance signal-to-noise ratio.
The agitator preferably has the same cross-sectional size as the shuttle valve and is accommodated in a common cartridge housing. Such a cartridge is easy to install and remove from an adapter sub housing disposed directly above the bit in a drillstring. In some applications, it may be advantageous to wire-line install or retrieve the cartridge through the drillstring without pulling the string from the borehole, and this option can be employed with the present invention.
Methods are disclosed for using a vibrational oscillator device comprising;
(i) allowing fluid to enter an upstream section of at least one fluid cavity within the device through an upstream mechanical stop and flow diverter section attached to an outer casing with an upstream shuttle valve spacer used to provide spacing between an upper section of a shuttle valve and an upstream mechanical stop assembly, wherein the shuttle valve includes a plunger positioned to be activated by forces exerted from an entrance of fluid into the vibrator,
wherein
(ii) the fluid forces the shuttle valve to move in a downstream direction until the shuttle valve plunger engages with a shuttle valve receiving assembly causing an upstream spring located above the shuttle valve assembly to lengthen;
and wherein
(iii) using a downstream spacer for the shuttle valve assembly for spacing at a bottom of the upstream spring is provided so that pressure is building within the shuttle valve receiving assembly, causing downstream directional motion of the shuttle valve receiving assembly and a fully assembled mass portion of the vibrator during compression of a first downhole oscillator spring that allows the shuttle valve plunger to disengage from the shuttle valve receiving assembly, causing the upstream spring for the shuttle valve assembly to return elastically to its initial or starting position;
and wherein;
(iv) a downstream surface of the shuttle valve receiving assembly is connected to at least one downhole spring receiving shaft which runs axially and is aligned with downstream components housing at least the first downhole oscillator spring positioned on either side of a casing mechanical stop and attached to at least a portion of a fully assembled oscillator component portion such that the downhole spring receiving shaft is allowing for movement in a linear fashion based on loading of the at least one downhole oscillator spring and positioning of the shuttle valve plunger in a partially and/or fully engaged or disengaged position with the shuttle valve receiving assembly causing oscillations of the at least one downhole oscillator spring and along a length of the oscillator thereby allowing for agitation due to vibration along a drillstring.
The method for generating pressure pulses within a conduit using a vibrational oscillator comprises at least partially interrupting flow of a pressurized fluid flowing through a casing of the oscillator comprising the steps of:
(i) introducing a pressure activated flow interruption shuttle valve into the casing, the valve being configured to periodically at least partially interrupt a flow of pressurized fluid within the casing;
(ii) allowing flow of the pressurized fluid through the casing; and
(c) directing the pressurized fluid through the valve to actuate the valve, actuation of the valve being implemented by:
(iii) using the pressurized fluid to cause at least a first spring section to compress such that when the valve is in a closed position the at least first spring section fully compresses thereby also at least partially interrupting a flow of the pressurized fluid in the casing ; and
(iv) using energy stored in at least the first spring when released is causing oscillatory cycling of pulses within the pressurized fluid.
A step of redirecting at least a portion of flow of the pressurized fluid within the casing comprises the step of redirecting at least a portion of the flow of the pressurized fluid upstream of a section of the casing such that the valve at least partially interrupts flow of the pressurized fluid in the conduit.
Energy from the vibrator is coupled to one or more devices, wherein the devices provide, electrical, mechanical, pneumatic, and/or hydraulic power.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The present invention is a vibrational oscillator device that creates movement along a drill-string utilizing borehole fluid flow of an incompressible liquid that normally generates a water-hammer effect which is usable for overcoming downhole static friction during drilling.
More specifically, as shown in
As also shown in
The first downstream oscillator spring assembly [140] and the second downstream oscillator spring assembly [150] work together with the upstream spring assembly [130] to absorb and later release the energy which can be initiated by either the drilling fluid and/or a water hammer effect causing any downhole pressure differential. Linear elastic restoring forces allow the compression (or “loading”) of the first downstream oscillator spring assembly [140] to provide the compression (or “loading”) of the second downstream oscillator spring assembly [150] upon return of the first downstream oscillator spring assembly [140] to its initial or starting position. An “unloaded” spring constitutes an “at rest” position of any of the spring(s) assemblies contained within the vibrational oscillator [100]. In this manner, the vibrational oscillator operates on the same principal as an oscillating pendulum. More specifically, the pendulum is a weight suspended from a pivot so that it can swing freely. When the pendulum is displaced sideways from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. In the present disclosure, the restoring force is from the first and second downstream oscillator spring assemblies [140] and [150]. When released, the restoring force combined with the pendulum's mass, causes it to oscillate about the equilibrium position, swinging back and forth. This is simply a weight (or bob) on the end of a massless cord suspended from a pivot, without friction. When given an initial push, it will swing back and forth at constant amplitude. Real pendulums are subject to friction and air drag, so the amplitude of their swings declines.
In the present disclosure, the actual vibrational oscillator is subject to friction and fluid drag occurring downhole. The shuttle valve plunger [225] moves similar to the action of a pendulum, however the movement is not along an arc but in a linear fashion. The first and second downstream oscillator spring assemblies [140] and [150] allow for continued back and forth movement that is initiated by the shuttle valve assembly [120]. The valve is designed to leak slightly so that fluid can always exert pressure, but still allow for fluid to escape when the compressive forces become excessive, leading to potential damaging of the spring. Controlling of the escaping drilling fluid is also desirable in order to control compression and thereby also control pressure pulses when so desired. By controlling the operation of the valve, it is possible to adjust the amplitude, oscillations and the frequency of the resulting vibrations. Measurement of pressure below the valve is also always possible even when there is no flow. This is desirable, as knowledge of pressure downhole is useful for controlling all aspects of oil and gas exploration including well completion and production.
It is important to understand that pressure differential can be generated by operation of the shuttle valve by controlling the opening and closing of the valve. This opening and closing operation can be performed by direct or indirect contact with the valve. The valve can be operated from uphole wireless or wired signals or can be operated downhole with devices within the casing or probes that activate a receiver located on or near the shuttle valve. It is desirable to control the flow of fluid into and out of the shuttle valve, so that the resulting oscillation can also be controlled. By controlling the oscillation, it is possible to control the frequency and amplitude of the vibrations that allow the agitator to function according to need. Complete opening or closing of the shuttle valve is possible and could either initiate or terminate the oscillations and the resulting vibrations. Fluid pressure that opens and subsequently closes the shuttle valve enhances drilling performance in several ways. A vibrational thrust can act on the drill bit, increasing the force with which it contacts the rock face. Furthermore, if the magnitude of the force is sufficiently great, i.e., any static friction along the drill string will be overcome. The pulsing vibrational action could even reach the rock face when vibrational pulses from the agitator are large enough to influence the drill bit. Overcoming static friction and providing the necessary energy to the drill string to keep the dynamic drilling operation functional and functioning (without interruption) is a major purpose of the agitator.
Although the vibrational agitator [100] in
F=kX, (3)
where k is the spring constant and X is the displacement of the spring(s)
The downhole spring receiving shaft [250] fits within the sleeve for the downstream sleeve for mechanical stop [260] which has a diameter that houses and supports the upper portion of the downstream collar [265]. The lower portion of the downstream collar [265] physically contacts the upper portion of the downstream mechanical stop assembly [160], which corresponds to movement of the fully assembled oscillator component [310] thereby causing return of the first and second downstream oscillator spring assemblies [140,150] (as shown in
Oscillations as needed to overcome static downhole forces are generated based on “loading” of the first downhole oscillator spring [245]. The more the first downhole oscillator spring [245] is “loaded” the more oscillations are produced, while the variability of the “loading” force determines the magnitude of the oscillation produced allowing for tailoring of the vibrational forces and subsequent seismic pulses (if so desired) utilized downhole.
To illustrate the onset of oscillatory motion of the device,
Eventually the fully assembled oscillator component [310] moves back to its original (initial starting) position (as shown in
This application is a National Phase filing under 35 USC 371 of and claims priority to PCT International application number PCT/US2015/063901, filed Dec. 4, 2015 entitled “Down-Hole Vibrational Oscillator”, which claims priority under 35 USC 119(e) from Provisional Application No. 62/087,9043 filed Dec. 5, 2014 of the same title.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/063901 | 12/4/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62087904 | Dec 2014 | US |
