EP0512330B1 - Drill bit - Google Patents

Description

Technical field

The present invention relates to a rock-destroying drilling tool and in particular relates to a drill bit.

Underlying state of the art

A drill bit is known which contains a hollow body with attached stones-destroying organs - rollers. A replaceable cylinder is arranged in the body and is fixed with respect to the former by pins. A chisel transition piece is connected to the body by means of a threaded connection, within which a slide sleeve of an assembly for generating hydrodynamic shafts with side channels and a central channel, in which wear-resistant attachments are mounted, is accommodated axially to the body. The chisel transition piece has an inner ring shoulder, which serves as a support for a spring which surrounds the bush and cooperates with the flanged edge of the bush.

After the drill bit has been inserted into a borehole, the valve sleeve is first flushed through the central channel. In this case, a force acts on the flanged edge of the sleeve, which is caused by a pressure drop on the attachment, which is arranged in the central channel. Under the effect of this force, the spring is compressed until the side channels come to rest under the end face of the cylinder. Here the side channels open and the fluid pressure in the sleeve drops so much that the spring brings the sleeve back up until these channels have been covered, and the cycle repeats. During the downward movement of the bushing, the flushing liquid located in the space between it and the bit transition piece is expelled upward through overflow openings.

The frequency of the pendulum movements of the sleeve can be regulated by the pump power and the cross-sectional area of the hydromonitor attachments.

• die erzeugten hydrodynamischen Pulsationen der Bohrflüssigkeit tragen zur Gesteinszerstörung wegen deren niedriger Frequenz und geringer Amplitude nicht bei und sichern keine Vergrößerung von Bohrkennziffern - der mechanischen Geschwindigkeit und meißelstandlänge;
• die Kompliziertheit der Konstruktion vom Standpunkt der :Herstellung und Montage erhöht die Herstellungskosten;
• das Vorhandensein beweglicher Baugruppen und Elemente in der Konstruktion gewährleistet keine erforderliche Betriebsdauer und -sicherheit, insbesondere in einem abrasiven Medium der Bohrflüssigkeit.

The well-known drill bit does not meet today's demands on drilling technology and does not ensure effective borehole drilling for the following reasons:

• the generated hydrodynamic pulsations of the drilling fluid do not contribute to the destruction of the rock due to its low frequency and low amplitude and do not ensure an increase in drilling parameters - the mechanical speed and the length of the bit;
• the complexity of the construction from the standpoint of: manufacturing and assembly increases the manufacturing cost;
• the presence of movable assemblies and elements in the construction does not guarantee the required operating time and safety, especially in an abrasive medium of the drilling fluid.

The invention is based on the design of a drill bit described in GB-A-2 224 094 according to the preamble of claim 1. A swirl of the flushing medium is generated in a swirl chamber, which leaves the swirl chamber via the outlet channel so that the radii enlarge the vertebra with the distance from the outlet channel. A negative pressure is generated in the center of the vortex, in which flushing medium flows against the direction of the vortex propagation. In the known drill bit, the swirl chamber with the outlet channel has a mushroom shape in cross section. However, the performance of the drill bit or its service life in operation is still in need of improvement.

The invention is therefore based on the object of improving a drill bit of this type by making the design change as simple as possible to the extent that it is distinguished by a longer service life or greater output.

The invention is characterized in the independent claims 1-3.

In the drawing, preferred embodiments are shown in detail; they are described in the following description of the figures also explained in more detail.

Just as in the prior art according to GB-A-2 224 054, the swirl chamber is narrowed in the outlet channel, so that when the Channel diameter, the frequency of rotation of the liquid proportional to the ratio of the diameter of the swirl chamber and the outlet port decreases and accordingly the frequency of the wave radiation increases.

The design of the end face of the outlet channel with a radial rounding is due to the need to keep hydraulic losses when guiding the drilling fluid into the annulus lower, and also improves the quality of the vacuum in the zone near the borehole.
According to an embodiment of the invention, it is expedient to make the cavity of the swirl chamber spherical. The choice of the shape of the swirl chamber in the shape of a sphere is due to a high amplitude of the waves generated by spherical emitters working in self-oscillation mode with a periodic hydraulic self-locking of the outlet channel.

According to a further embodiment of the invention, the swirl chamber is provided with a conical wave reflector arranged in its upper part in the direction of its longitudinal axis, the angle of inclination of the generatrix of the conical surface of the reflector being below the critical value of the sliding angle of a wave incident on the conical surface. Equipping the swirl chamber with the tapered shaft reflector allows hydroacoustic and cavitation wear on the central part of the chamber head to be prevented and the service life of the drill bit to be increased.

worin

c

die Schallgeschwindigkeit in der Spülflüssigkeit;

c₁

die Schallgeschwindigkeit im Metall;

n

der Brechungskoeffizient

sind.The choice of the angle of inclination XX of the generatrix of the conical surface of the wave reflector not above the critical value 0'd of the slip angle of the acoustic incident wave is due to the fact that the interface of the two media (rinsing liquid and metal) with different densities and compressibilities has a reflection, absorption and represents refractive surface. If the sliding angle 0 of the incident wave is not greater than the critical sliding angle 0 ', that is 0 <0', total reflection takes place. Such a wave does not transfer energy from the first medium (rinsing liquid) into the second medium (metal), which is why the total energy of the incident wave is reflected back to the first medium. An angle between the Direction of wave propagation and the interface. The cosine of the critical sliding angle 0 'is equal to the refractive index of the second medium with respect to the first (Snellius's law) ie $${\text{cos 0 '= n = c / c}}_{\text{1}}\text{,}$$

wherein

c

the speed of sound in the rinsing liquid;

c ₁

the speed of sound in the metal;

n

the refractive index

are.

According to another embodiment of the invention, the assembly for generating hydrodynamic waves is provided with a resonance chamber, the cavity of which is connected to the cavity of the swirl chamber and the volume of which is variable and in which a piston with a rod, with the possibility of displacement in the longitudinal direction, is accommodated .

This is due to the need to tune the waves generated to a resonant frequency at different flow rates and densities of the drilling fluid. The tuning to the resonance frequency takes place by moving the piston by means of a worm rod and by changing the volume of the resonance chamber under the piston.

The drill bit designed according to the invention ensures a high effectiveness of the borehole sinking. In addition, it enables shaft colmatation of the borehole wall when crossing geologically complex horizons (in fall-up, swallowing zones, in the event of water, oil, or natural gas leaks). The application of the registered drill bit also makes it possible to significantly increase the mechanical drilling speed and the bit stand length.

• Fig. 1 die Gesamtansicht eines erfindungsgemäßen Bohrmeißels;
• Fig. 2 einen erfindungsgemäßen kegeligen Wellenreflektor;
• Fig. 3 die Gesamtansicht des erfindungsgemäßen Bohrmeißels, mit einer in dessen Körper ausgeführten Wirbelkammer;
• Fig 4 einen IV-IV-Schnitt nach Fig. 2;
• Fig. 5 die Gesamtansicht des erfindungsgemäßen Bohrmeißels mit einer Wirbelkammer;
• Fig. 6 die Gesamtansicht des erfindungsgemäßen Bohrmeißels mit einer Resonanzkammer;
• Fig. 7 eine Skizze zur Veranschaulichung der Arbeit des erfindungsgemäßen Bohrmeißels in einem Bohrloch.

The present invention will be explained below using specific exemplary embodiments with reference to the accompanying drawings. Show it :

• 1 shows the overall view of a drill bit according to the invention;
• 2 shows a conical wave reflector according to the invention;
• 3 shows the overall view of the drill bit according to the invention, with a swirl chamber executed in its body;
• 4 shows an IV-IV section according to FIG. 2;
• 5 shows the overall view of the drill bit according to the invention with a swirl chamber;
• 6 shows the overall view of the drill bit according to the invention with a resonance chamber;
• Fig. 7 is a sketch to illustrate the work of the drill bit according to the invention in a borehole.

The drill bit according to the invention contains a body 1 (FIG. 1) with attached rock-destroying organs - rollers 2. In the body 1, an assembly for generating hydrodynamic waves is arranged, which represents a swirl chamber 3 with tangential inlet channels 4. The vortex chamber 3 has a very conically tapering outlet channel 5. The end face 6 of this channel 5 is radially rounded. The swirl chamber 3 is provided with a conical wave reflector 7 (Fig. 1, 2). The conical reflector 7 serves to prevent wear of the head of the swirl chamber 3 under the action of hydroacoustic and hydro shock, high-frequency and ultrasonic waves and occurs as a hydroacoustic wave concentrator.

The body 1 of the drill bit 1 can also serve as the body of the swirl chamber 3 (FIGS. 3, 4).

In order to increase the amplitude of the waves generated and the effectiveness of the rock destruction, the swirl chamber 3 (FIG. 5) is designed in a spherical shape with tangential inlet channels 4 and a central outlet channel 5.

To increase the drilling capacity, the swirl chamber 3 (FIG. 6) is equipped with a resonance chamber 8, in the interior of which a piston 9 with a rod 10 is accommodated. By screwing the rod 1 in and out, the volume of the chamber 8 under the piston 9 is changed.

The drill bit works as follows. The drilling fluid is passed through a drill string 11 (FIG. 7) into the tangentially directed inlet channels 4. Furthermore, the drilling fluid flows through the tangential channels. 4 in the swirl chamber 3. In the swirl chamber 3, the drilling fluid is set in rotation and directed through the outlet channel 5 into the annular space.

As a result of the narrowing of the outlet channel 5, the intensity of the rotation of the drilling fluid increases suddenly at its outlet. The kinetic energy of the turbulent flow directs the drilling fluid into the annulus in radially declining directions. In this case, a negative pressure is generated in the swirl chamber 3 and in the central zone of the sole. As a result of a periodic breakthrough of the drilling fluid from the zone near the borehole into the swirl chamber 3, powerful hydrodynamic pressure pulses of the self-oscillation type are generated in the zone near the borehole. The amplitude and the frequency of the waves generated depend on the geometric parameters of the swirl chamber 3, the pressure drop in the device, the density and the amount of the liquid to be pumped through.

The hydroacoustic waves generated by the assembly propagate mainly in two directions: inside the swirl chamber 3 and on the bottom of the borehole. The inwardly directed hydroacoustic waves are received by the conical wave reflector 7, from the conical surface of which is totally reflected and scattered, without having a destructive effect on the head of the swirl chamber 3. This increases the operational safety and duration of the chisel, while the hydroacoustic waves directed at the bottom of the borehole intensively destroy the central part of the bottom of the borehole and are superior in some rocks to tooth-shaped mechanical rock destruction.

The application of the registered drill bit allows the mechanical drilling speed and the length of the bit to be significantly increased compared to the prototypes and the best applicable bits.

The effectiveness is achieved by generating a high wave energy directed effect in the zone near the borehole. In addition, the present chisel ensures wave colmatation of the borehole wall when passing through geologically complex horizons (in fall-up, swallowing zones, in the event of water, oil, natural gas leaks).

Industrial applicability

The invention can be used in well drilling using rock-destroying organs of the roller type.

Claims (4)

1. A trepan comprising a body (1) with rock-destroying members fixed thereon and an assembly disposed therein for generating hydrodynamic waves of a washing medium, wherein the assembly for generating hydrodynamic waves comprises a whirl chamber (3) with tangentially disposed entrance channels (4) and a conically tapering exit channel (5) with a rounded front face,
   characterized in
   that the whirl chamber (3) is provided in the upper part thereof with a conical wave reflector (7) disposed in the direction of its longitudinal axis, having a cone point oriented in the direction of the exit channel (5), the inclination angle (ϕ) of the generatrix of the conical surface of the reflector (7) being less than the critical value (Θ') of the gliding angle (Θ) of a wave incident on the conical surface, the gliding angle (Θ) constituting the angle between the wave incident on the conical surface and the conical surface and the cosine of the critical gliding angle value (Θ') corresponding to the refractive indices n between the washing medium and the material of the reflector (7) according to the relation n = c/c₁ (c = sound velocity in the washing medium; c₁ = sound velocity in the reflector material).
2. A trepan comprising a body (1) with rock-destroying members fixed thereon an assembly disposed therein for generating hydrodynamic waves of a washing medium, wherein the assembly for generating hydrodynamic waves comprises a whirl chamber (3) with tangentially disposed entrance channels (4) and a conically tapering exit channel (5) with a rounded front face,
   characterized in
   that the cavity of the whirl chamber (3) is configured to be spherical in shape and that the exit channel (5) is disposed centrally.
3. A trepan comprising a body (1) with rock-destroying members fixed thereon and an assembly disposed therein for generating hydrodynamic waves of a washing medium, wherein the assembly for generating hydrodynamic waves comprises a whirl chamber (3) with tangentially disposed entrance channels (4) and a conically tapering exit channel (5) with a rounded front face,
   characterized in
   that the assembly for generating hydrodynamic waves is provided with a resonance chamber (8) the cavity of which is connected with the cavity of the whirl chamber (3) and the volume of which is variable.
4. A trepan according to claim 3,
   characterized in
   that the size of the cavity of the resonance chamber (8) may be set by an adjustable piston (9) having a rod (10) via which the piston (9) is adjustable in the longitudinal direction.

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