EP0502938B1 - Drilling bit irrigated by a fluid distributed by a fluidic oscillator - Google Patents

Abstract

A drilling bit having an irrigation system which uses an irrigating fluid. The bit comprises a hollow drill head (14) housing at least one fluidic oscillator (23, 23') which includes an accelerator nozzle (26, 26') supplied by said fluid and opening into a cavity (46, 46') in which a dividing element (34, 34') is mounted which is provided with a ridge (36, 36') located slightly downstream from the nozzle. Said dividing element defines in said cavity two passages (42, 44, 42', 44') towards which the fluid is alternately directed in pulsed jets. Said passages are linked respectively to two series of channels (16 to 22) which open onto the outer surface of the head (14) through a plurality of outlet openings (21) which are oriented so that the pulsed jets they give out are directed to selected portions of the head that need to be cleaned, cooled or lubricated.

Description

The present invention relates to a rotary tool provided with an irrigation system which makes it possible to clean the tool by means of a fluid distributed by a fluidic oscillator. The invention applies in particular to tools for drilling oil or mining wells.

As is known, a fluidic oscillator makes it possible to switch a flow of fluid which passes through it alternately in two different directions, with a frequency which depends on the flow rate of the fluid, as well as on the physical characteristics of the oscillator.

Among the most well-known fluidic oscillators, mention may be made of monostable Coanda effect oscillators, which generally comprise a supply nozzle opening into a distribution chamber for the flow of fluid in two possible directions, defined between concentric surfaces. The latter are shaped so that the fluid attaches stably to one of them, thus favoring flow in one of the directions. The flow can be switched to the other direction under the action of an external force involving low energy. The flow in the new direction being unstable, it tends to spontaneously switch to the stable direction as soon as said action has ceased.

There are also bistable Coanda effect oscillators, in which the flow attaches stably to both surfaces of the oscillator. In this case, an external action must be brought in at each alternation to switch the flow from one direction to the other.

Fluid oscillators are also known which operate on the same principle as a whistle, that is to say by the natural phenomenon of the spontaneous vibration of the air on either side of a pointed rigid piece or ending with an edge.

The present invention relates to the application of fluidic oscillators for the irrigation of rotary tools, and more particularly of drilling tools comprising a head pierced with at least two channels which open onto the surface of the head of the tool.

From patent FR-A-2 399 530, a drilling tool is known which is equipped with a percussive mass freely movable mounted in an envelope and with a fluidic oscillator which drives said mass in alternating vibratory movement. However, no irrigation system is provided on this tool to clean or cool critical areas of the tool.

US-A-3,405,770 relates to a drilling tool in which a fluid is subjected to a cycle of pressure reductions in the vicinity of the borehole and simultaneously increases in the speed of the ejected fluid. The fluid attacks the rock but is not used to clean the tool.

US-A-3,630,689 also relates to a drilling tool comprising a fluidic oscillator intended to generate phase-shifted pressure fluctuations in two channels. Here too, the jets of fluid are used to attack the rock but not to clean the tool.

Also known from US-A-3,532,174 and 3,610,347 are percussion drilling tools. However, no means are provided for cleaning the tool.

The patent FR-A-2 352 943 relates to a drilling tool in which the fluid is sent to the rock in the form of two jets pulsed under pressure, in order to entrain the cuttings towards the outside of the well.

Finally, there is known an irrigation system for a drilling tool, through a network of channels drilled in the tool, and at the outputs of which are mounted suitably oriented nozzles to project, either directly or indirectly, onto selected parts of the tool, such as cutters, continuous jets of fluid capable of removing the particles of rock and mud which adhere to it.

However, this irrigation system keeps a relative efficiency insofar as, the total flow of fluid being divided between the nozzles, the power of each jet represents only a fraction of the total power of the fluid, so that the jets are sometimes too weak to clean the tool completely or in critical areas.

Patent EP-0 171 852 relates to a drilling tool according to the preamble of claim 1. This tool is provided with a filtering element making it possible to retain the particles of material entrained by the fluid and having a diameter greater than that of the orifices formed on the wall of the tool. This tool has the same drawback as the previous one, since the entire fluid flow is shared between all the orifices to form continuous jets of fluid. The individual powers of these jets are too low to ensure proper cleaning of all parts of the tool.

The invention relates to a drilling tool provided with an irrigation system free from the drawbacks of the cited prior art.

The invention relates to a drilling tool according to the characterizing part of claim 1.

An advantage of the irrigation system according to the invention lies in the fact that the fluid flow is switched from one channel to the other a great number of times per second and that at each switching, all or almost - total flow passes through the corresponding channel. As a result, with the same useful outlet section, the impact energy obtained with the system according to the invention will be double that obtained with conventional systems where the total flow is shared between the outputs.

Another advantage of the invention lies in the fact that it becomes possible to increase the useful outlet section without compromising the quality of the cleaning of the selected areas. In addition, alternating pulses emitted at relatively high frequency are more effective than a continuous jet.

Advantageously, on the walls of said passages are formed respectively two shoulders with a concavity facing the nozzle, so that each of them can intercept part of the flow of fluid flowing in the corresponding passage and return it to the other passage.

According to one embodiment of the invention, the acceleration nozzle has an annular section and the dividing element is tubular with an outer frustoconical face flaring in the direction of flow of the fluid and an inner frustoconical face narrowing in the direction of flow, said faces defining at the upper end of the dividing element a circular edge of the same diameter as the outlet orifice of the nozzle and coaxial with the latter.

In a simpler variant, the nozzle has a straight outlet slot and the dividing element is in the form of a dihedral with a straight edge.

The irrigation system according to the invention allows the cleaning of blades, cutters, diamonds or other elements for cutting diamond tools, knurling wheels, teeth or spikes of tricone tools, etc.

According to the invention, it is possible to increase the frequency of the pulses and to cause hydraulic effects improving the washing (alternating crossed jets, jets of different frequencies), by using several fluidic oscillators mounted in cascade.

• La figure 1 est une vue en coupe axiale d'un outil de forage selon un premier mode de réalisation;
• La figure 2 est une vue en coupe suivant la ligne II-II de la figure 1;
• La figure 3 est une vue en coupe suivant la ligne III-III de la figure 1;
• La figure 4 montre une vue en coupe axiale d'un outil de forage selon un second mode de réalisation;
• La figure 5 est une vue en coupe selon la ligne V-V de la figure 4;
• La figure 6 montre schématiquement un montage d'oscillateur permettant d'obtenir deux jets alternés et un jet constant; et
• La figure 7 représente schématiquement un système d'irrigation à trois oscillateurs fluidiques permettant d'augmenter la fréquence des jets alternés.

The invention will now be described with reference to the appended drawings given by way of nonlimiting examples and in which:

• Figure 1 is an axial sectional view of a drilling tool according to a first embodiment;
• Figure 2 is a sectional view along line II-II of Figure 1;
• Figure 3 is a sectional view along line III-III of Figure 1;
• Figure 4 shows an axial sectional view of a drilling tool according to a second embodiment;
• Figure 5 is a sectional view along line VV of Figure 4;
• FIG. 6 schematically shows an oscillator arrangement making it possible to obtain two alternating jets and a constant jet; and
• FIG. 7 schematically represents an irrigation system with three fluidic oscillators making it possible to increase the frequency of the alternating jets.

In FIGS. 1 to 3, a rotary drilling tool has been designated by 10. This comprises a tubular portion 12 fixed to a drive element (not shown), and a head 14 having on its surface attack elements which can have a wide variety of shapes. The head is pierced with a plurality of channels for the passage of an irrigation fluid, for example a central channel 16 parallel to the axis of the tool and three lateral channels 18, 20, 22 distributed regularly around the channel central. These channels can branch in the vicinity of their ends so as to open out through several groups of outlet orifices 21 suitably oriented so that they project jets of fluid towards selected parts of the tool, which in particular require washing. , cooled or lubricated. The outlet ports may be provided with nozzles.

In the tool is inserted a fluidic oscillator 23 formed of two superimposed cylindrical bodies 19, 24. The upper body 19 is provided with an acceleration nozzle 26 of tubular shape, through which the fluid arrives. The lower body 24 is tubular, and has at its upper part a cylindrical bore 28 of relatively large diameter followed by a bore 30 of smaller diameter and which expands in the direction of flow. These two bores define between them a shoulder annular 32 facing the nozzle.

In the lower bore 30 of the tubular body is fixed coaxially, for example by means of connecting bridges not shown in Figure 1, a tubular divider element 34 provided with a frustoconical outer face flaring in the direction of flow and of a frustoconical inner face narrowing in the direction of flow. The dividing element ends at its upper end with a circular edge 36 of diameter equal to that of the annular outlet orifice for the nozzle 26. This edge is coaxial with said orifice, slightly downstream of it, and is located at above the level of the shoulder 32.

In the cavity of the dividing element 34 is mounted coaxially a central core 38 extending over the entire height of the lower body 24. This core has an internal annular shoulder 40 facing the nozzle and being at the same level as the shoulder external 32. Under the shoulder 40, the core has a frustoconical shape, with the same conicity as the external surface of the dividing element. It follows from this geometry that the dividing element defines with the central core an internal annular passage 42 and, with the lower body 24, an external annular passage 44. These passages are dimensioned with diameters chosen so that they open respectively into the central channel 16 and lateral channels 18, 20, 22.

It will be noted that the central core 38 can be eliminated and the shoulders 40 formed on the internal frustoconical wall of the divider element 34.

The operation of the system of FIGS. 1 to 3 is as follows: the drilling mud is accelerated in the nozzle 26 and opens at high speed in a distribution chamber 46 defined above the shoulders 32, 40. Due to the vibrational phenomenon explained previously, the mud flow alternately passes inside the dividing element, through the internal passage 42, towards the central channel 16, then outside of said element, by the passage 44, towards the lateral channels 18, 20 and 22, and this at a frequency which depends on the speed of the flow and on the geometry of the dividing element. This vibratory phenomenon is favored by the presence of the annular shoulders 32, 40, since they have the effect of returning part of the fluid flow from one passage to the other. However, the device can also function satisfactorily even in the absence of any shoulder.

In the embodiment of FIGS. 4 and 5, the fluidic oscillator 23 ′ comprises a nozzle 26 ′ of square or rectangular section, with rectilinear outlet slot which opens into a distribution chamber 46 ′ of dihedral shape, the walls of which have two parallel shoulders 32 ′, 32˝. In this cavity is mounted a dividing element 34 ′ in the form of a dihedral with a straight edge 36 ′ which defines two passages 42 ′ and 44 ′ communicating respectively with the channels 16, 18 of the tool.

The operation of this oscillator is similar to that of FIG. 1. Here also the shoulders 32 ′, 32˝ return part of the flow of the fluid from one passage to the other, thus promoting the vibratory phenomenon.

It will be noted that a fluidic oscillator can be produced, one of the passages of which receives more fluid than the other, by slightly shifting the dividing element 34 or 34 ′ with respect to the axis of the nozzle. In this case, the flow rate in the passage which receives the most fluid is only partially switched to the other passage. It follows that the nozzles connected to said passage receive a constant flow to which is added a variable flow giving rise to alternating jets.

In one embodiment of the invention, instead of mounting a single oscillator in the tool, it is possible to put in place removably in the orifices 21, respectively several oscillators in the form of oriented pulses. It is thus possible to carry out alternating irrigation with multidirectional flow.

The hydraulic system shown in FIG. 6 comprises a fluidic oscillator 23₁ according to one of the types presented above. The oscillator is supplied with drilling mud by a pipe 48 and emits, through several channels (for example two channels 16, 18), two alternating and intermittent jets. Part of the drilling mud flow is taken upstream of the oscillator through a conduit 50 in order to be directed onto an area which requires permanent irrigation. All of these elements are integrated into the tool, which has not been represented for the sake of simplification.

It is also possible to produce an irrigation system comprising several fluidic oscillators mounted in cascade. For example, the system of FIG. 7 comprises a first fluidic oscillator 23₂ which emits two intermittent and alternating jets through two channels 52, 54, which are respectively connected to two fluidic oscillators 23₃, 23₄. Each of these jets is therefore transformed into two jets of higher frequency, and which are emitted by channels 56,58, for the oscillator 23₃, and by channels 60, 62 for the oscillator 23₄. If the three oscillators are identical, it is possible to obtain at the output of the oscillators 23₃, 23₄ jets of frequency twice that of the jets leaving the oscillator 23₂. Here too, all of the oscillators and channels are integrated inside the tool.

Of course, channels 56 to 62, or some of them, can in turn supply other oscillators. It is thus possible to constitute an irrigation system with two, three or more stages of oscillators providing intermittent jets of different frequencies.

Modifications can be made to the embodiments described without departing from the scope of the invention. For example, the divider element of Figure 1 can be simply tubular without having internal and external taper. Similarly, the divider element of Figure 4 can be constituted by a single wall, with parallel or substantially parallel faces.

Claims (10)

1. Boring tool with an irrigation system intended to clean, cool, or lubricate chosen parts of the tool, of the type comprising a hollow boring head pierced with two series of ducts emerging on the outer surface of the head via a plurality of outlet orifices equipped with jet nozzles, capable of spraying jets of fluid in different directions, characterized in that in the boring head (14) is housed at least one fluid oscillator (23; 23′) including an acceleration nozzle (26; 26′) fed by the said fluid and which emerges into a cavity (46; 46′) in which is mounted a splitter element (34; 34′) provided with a ridge (36; 36′) located slightly downstream of the nozzle, the said splitter element defining, in the said cavity, two passages (42, 44; 42′, 44′) which communicate respectively with the said two series of ducts (16; 18, 20, 22) and towards which all of the flow rate of fluid is directed alternately in pulsed jets, following natural vibrations of the fluid which are induced by the splitter element (34; 34′).
2. Boring tool according to Claim 1, characterized in that on the walls of the said passages 42, 44; 42′, 44′) are respectively formed two shoulders (32, 40; 32′, 32˝) with concavity pointing towards the nozzle, such that each of them can intercept part of the flow rate of fluid flowing in the corresponding passage and send it back towards the other passage.
3. Irrigation system according to one of Claims 1 and 2, characterized in that the acceleration nozzle (26) has an annular cross-section and the splitter element (34) is tubular with a frustoconical outer face widening in the direction of the flow of the fluid and a frustoconical inner face narrowing in the direction of the flow, the splitter element ending slightly downstream of the orifice of the nozzle in a circular ridge (36) of the same diameter as the said orifice and coaxial with it, a central core (38) being mounted concentrically inside the splitter element (34) in order therein to define an annular internal passage (42), the walls of the cavity (46) and of the core (38) respectively exhibiting an external annular shoulder (32) and an internal annular shoulder (40) with concavities pointing towards the nozzle.
4. Boring tool according to one of Claims 1 and 2, characterized in that the splitter element is tubular with a frustoconical outer wall widening downstream and a frustoconical inner wall narrowing downstream, an internal annular shoulder and an external annular shoulder respectively being formed on the inner frustoconical wall of the splitter element and on the wall of the cavity (46).
5. Boring tool according to one of Claims 1 and 2, characterized in that the nozzle (26') exhibits a straight outlet split, and in that the splitter element (34′) is in the shape of a dihedron with a straight ridge (36′), the walls of the cavity (46) respectively comprising two shoulders (32′, 32˝) with concavities pointing towards the nozzle.
6. Boring tool according to one of Claims 1 and 2, characterized in that the splitter element consists of a tubular element, the external and internal walls of which exhibit no concavity.
7. Boring tool according to Claim 5, characterized in that the splitter element consists of a flat partition with parallel or substantially parallel faces.
8. Boring tool according to one of Claims 1 and 2, characterized in that the splitter element (34; 34′) is centred exactly on the axis of the nozzle (26, 26′) or is slightly offset with respect to the said axis.
9. Boring tool according to Claim 1, characterized in that it includes a fluid oscillator (23₁) which emits at least two alternating and intermittent jets, part of the flow rate of fluid being taken off upstream of the oscillator by a pipe (50) in order to be directed to a zone of the tool which requires permanent irrigation.
10. Boring tool according to one of Claims 1 and 2, characterized in that it comprises at least two stages of oscillators mounted in cascade and comprising a first fluid oscillator (23₂) which emits two intermittent and alternating jets through two ducts (52, 54) which are respectively connected to the inlets of at least two other fluid oscillators (23₃, 23₄), each of the latter in turn emitting at least two jets of fluid with a frequency higher than that of the jets which feed it, it being possible for these jets, or some of them, in turn to serve to feed one or more other fluid oscillators.

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