BE1003211A3 - METHOD AND DEVICE FOR DAMPING VIBRATIONS IN A ROTATED DRIVED ROD TRAIN. - Google Patents

Abstract

Method of damping vibrations in a drill string (2) placed end to end and driven in rotation in a cavity, in particular in a drill string (2) provided with a drilling head (3) or coring, comprising the possible use of a heavy material element, further comprising: the selection of at least one material having an impact damping characteristic and the metering by volume or by weight of this damping material and of any heavy material as a function of the vibrations to be damped, the addition of this damping material in possible association with the heavy material in at least one location of the drill string, and a possible adjustment of the aforementioned dosage.

Description

"Method and device for damping vibrations in a train of rods driven in rotation".

The present invention relates to a method of damping vibrations in a drill string placed end to end and driven in rotation in a cavity, in particular in a drill string equipped with a drilling or coring head, comprising the 'possible use of a heavy element.

We know from US-A-4,881,605 a method and a device of this kind in which, in order to reduce the vibrations of the drill string and increase the rates of penetration in the materials to be drilled or cored, it is applies directly to the drilling head or to its support for fixing to the drill string a heavy mass separate from the latter, a large part of the drill string can thus be kept in tension in an attempt to reduce the risk of buckling of this large part .

This process does not however eliminate vibrations resulting for example from the work of the drilling head or coring against rock or sediments or resulting from the part of the drill string rotated and maintained in compression so that the weight of the heavy mass acts fully on the drilling head. These vibrations in fact constitute a serious drawback with regard to the lifetime of a drilling head formed for example by a multitude of diamond plates which are fixed to a very resistant matrix but which can detach or break under the effect of shocks resulting from vibrations, these can be amplified by the presence of the heavy mass which is in direct connection with the drilling head and which consists for example of metal tubes fitted in a train parallel internal to the train stems. In addition, this internal train of tubes is difficult to adapt to variations in conditions during drilling.

This known method leads to a considerable increase in the masses used and therefore of the inertias to be overcome, for example for the rotation of all of the rod trains. In addition, during a reaction of these increased masses, for example to a shock, the energy accumulated by these masses and restored increases the risk of significant damage both to the drilling head, to the drill string and to the installation. drilling themselves to which this known process is applied.

The object of the invention is to remedy these drawbacks and to provide a method which makes it possible to perform drilling under considerably improved conditions by absorbing the vibrations which appear in the drill string, without however requiring tensioning of 'an important part of the latter. In addition, it is preferable that the method according to the invention allows constant adaptation to the drilling conditions.

To this end, according to the invention, said method further comprises: - the selection of at least one material having an impact damping characteristic and the metering by volume or by weight of this damping material and of the material heavy, depending on the vibrations to be damped, - the addition of this damping material, possibly in association with the heavy material, to the drill string in at least one location thereof, and - a possible adjustment of the dosage cited above.

By damping material must be understood a material having a certain elasticity and / or ability to absorb a shock, a vibration etc., as can for example be a rubbery material, a more or less viscous and possibly laminated fluid, etc. ..

According to one embodiment of the invention, the method comprises the distribution of the damping material and, where appropriate, of the heavy material in one or more locations along the drill string, and the possible adjustment of this distribution . Where appropriate, the method according to the invention also comprises either separately or in combination with said distribution, the addition of a damping material and possibly a heavy material to the drilling or coring head. In addition, if the method involves the introduction of damping material and / or heavy material into a hollow body which is connected to the drill string, it may also include the possible introduction into this hollow body of a damping fluid, the quantity of which may be subject to adjustment.

According to an advantageous embodiment of the invention, the method comprises: - the detection of a level of vibrations in the drill string, - the comparison of the level of vibrations detected with a determined maximum threshold, and - if the level of vibration detected is greater. at said maximum threshold, a modification of the above-mentioned setting.

The invention also relates to a device for damping vibrations in a drill string placed end to end and driven in rotation in a cavity, in particular in a drill string equipped with a drilling or coring head. , comprising a vibration absorption element attached to the drill string.

According to the invention, this device comprises at least one aforementioned vibration absorption element which is at least partially made of a damping material.

Other details and particularities of the invention will emerge from the description of the drawings appended to this memo and which illustrate, by way of nonlimiting examples, the method and particular embodiments of the device according to the invention.

Figure 1 shows a section of a particular vibration damping device according to the invention, acting directly on the drilling head.

Figures 2 and 3 show two embodiments of the vibration damping device arranged in the drill string.

The damping device 1 according to the invention is intended to considerably dampen vibrations appearing in a drill string 2 which rotates for example a drilling head 3, particularly when the latter attacks sediments or rocks, during drilling an oil well among others. Similar vibrations can also occur during core drilling operations.

The damping device 1, shown schematically by way of example in FIG. 1, is arranged and fixed between the drilling head 3 and the drill string 2 proper which is of substantially cylindrical section and of which only the lower end 4 in the drilling position is drawn. This end 4 has an axial channel 102 which is used for supplying drilling liquid to the drilling head 3 from a drilling platform not shown but well known in the art. At this lower end 4 is for example screwed a connecting element 5 which has inter alia a bell shape and to which is fixed in a known manner a fixing part 6 in the form of a bowl to form with the connecting element 5 a chamber 7. In addition, the fixing part 6 and one or more sections of tube 8 of substantially cylindrical section connected respectively to each other and to the fixing part 6, axially with respect to the connecting element 5 , constitute a hollow body 9 whose internal volume 10 can be adapted by, for example, having more or less tube sections 8. At the lower end of the lowest tube section 8 is fixed the actual drilling head 3.

In the exemplary embodiment of FIG. 1, the lower end 4 of the drill string 2, the connecting element 5, the fixing piece 6, and each section of tube 8 are respectively screwed one into the other, by carrying out a centering interlocking, so as to be arranged coaxially with respect to each other and with respect to the drill string 2 and in order to transmit to the drilling head 3 the necessary torque provided by the drill string 2.

A conduit 11 arranged axially to the tube sections 8 and formed for example in one piece connects in a known manner the chamber 7, which is supplied with drilling liquid through the axial channel 102, to a distribution chamber 12 of the head drilling, from which said drilling liquid is supplied to the usual nozzles 13. This duct can also be used for fixing the assembly formed by the fixing part 6, the drilling head 3 and the tube sections S which constitute the aforementioned hollow body 9 in the embodiment described.

In the example illustrated in FIG. 1, the connecting element 5 is also profiled to produce a gradual transition between the external diameter of the end of the rod 4 and the diameter of the sections of tubes 8.

The element of. fitting 5, the fixing part 6, the tube sections 8, the conduit 11, etc. can be considered as part of the drill string, their purpose being to provide the above-mentioned volume 10 in the drill string 2, particularly near the drilling head 3.

The aforementioned volume 10 of the embodiment described by way of example with the aid of FIG. 1 is of cylindrical shape and can receive, for example, a mixture of metal balls (steel, cast iron, etc.) and balls of rubber filling partially, at 14, or completely the volume 10 so as to constitute a vibration absorption element. The metal balls constitute a heavy material, the rubber balls constituting a damping material.

The oscillations of the vibrations recorded in the drill string 2 and caused for example by the work of the drill head generally have a main component oriented longitudinally along the axis of the drill string 2. The rubber and metal balls subject to these oscillations but not directly linked to the drill string 2 or the drill head 3 oscillate at another frequency and / or amplitude and counteract the oscillations of the drill head 3 and / or the drill string 2 at point d '' cancel these oscillations or at least prevent their maintenance. In addition, these balls act in the same way against radial oscillations of the drill string 2 or of the drilling head 1.

According to the invention, instead of the aforementioned mixture of balls, it is also possible, for example, to insert into the volume 10, more or less freely relative to the side walls of the volume 10 formed by the tube sections 8, a rubber block which can be substantially cylindrical, which is arranged around the conduit 11 and which can coat one or more masses of metal forming the heavy material, to constitute a vibration absorbing element. The height of this rubber block can be chosen to be less than the free height of the volume 10 so that this block can be displaced longitudinally in the volume 10 by the longitudinal components of oscillations that the drilling head inter alia communicates with the drill string 2 during drilling. However, since the block is not fixed directly or indirectly to the drilling head, its longitudinal oscillations are out of phase with those of the entire drilling head and the drill string and at least partially oppose the oscillations of this assembly, preventing at least the maintenance of these vibrations in the aforementioned assembly or canceling them. It should be remembered that this aforementioned assembly constitutes a considerable mass which in oscillation develops a very high energy and therefore significant forces.

A damping fluid can, if necessary, complete the filling of the volume 10, designed in a sufficiently watertight manner in this case, and brake all the more the movements of the above-mentioned rubber block.

In the case of the embodiment of FIG. 1, the method of damping vibratioris in a drill string 2 according to the invention consists of selecting, according to known drilling parameters (weight of the drilling head 3, weight of the drill string 2 at various stages of drilling, rotational speeds, geological terrain at the place of drilling, etc.) a damping material, for example a particular rubber, and possibly a heavy material, for example example a steel and to determine a shape to give to these materials, for example the shape of balls. Then, these two materials should be dosed in the form chosen, for example as a function of the weight of the drill string 2 and of the drilling head 3 used and the speed of rotation of these elements. Depending on the materials dosed, for example, the volume 10 which will contain these heavy and damping materials is determined, possibly taking into account a free space allowing movement of these materials when they are subjected to vibrations during drilling. The volume 10 is then constituted, inter alia in the case of the example of FIG. 1, by fixing at the upper end of the drilling head 3 a stack of tube sections 8 in sufficient number and a conduit 11 of length corresponding. The steel and rubber balls are then poured into the volume 10, possibly providing means to avoid separation of the steel balls into separate layers of the rubber balls, and the volume 10 is closed by fixing the fixing piece. 6 to the upper tube section 8 in the above-mentioned stack and to the conduit 11, then the connecting element 5 is fixed between the fixing part 6 and the end k of the drill string 2. By this construction, the element vibration absorption advantageously acts directly on the drilling head 3 which seems to constitute the main source of vibrations, given the multitude of diamonds which decorate the periphery.

If during drilling, we still notice vibrations, we can among other things either raise the drilling head 3 to the surface, open the volume 10 to modify it, depending on experience for example, the dosage or the amount of heavy and / or damping materials either add to the drill string 2 a vibration absorbing element 1, for example like that described below with reference to FIG. 2 or 3. This addition will preferably be made as the drill string 2 lengthens.

In addition, in order to adjust the damping rate of the device described above, it is possible, for example, to provide a complementary pipe, not shown, bringing in a known manner in volume 10, from the drilling platform. , a fluid which can be viscous and which is introduced or withdrawn from volume 10.

Figure 2 shows another embodiment of the vibration damping device 1 according to the invention, arranged along a rod 15 of the drill string 2. In this example, the heavy material consists of two metal discs 16 and the damping material by three rubber discs 17 disposed between the metal discs 16 and on either side of the stack of discs thus formed. These discs 16 and 17 are for example drilled in their center so that they can be arranged around the rod 15 and guided along the latter between a rest position bearing on a plate 18 fixed in a known manner (by welding for example) to the rod 15 under the stack of discs lé, 17 and an extreme upper position determined by a stop 19 which can be adjustable along the rod 15 and which is located above the stack of discs 16, 17 either to be in permanent contact with the latter either to allow this stack to move along the rod 15 as a function of the vibrations transmitted via the plate 18. The plate 18 and the stopper 19 advantageously respectively have a surface d 'support 20 and an abutment surface 21 perpendicular to the longitudinal axis of the rod 15. The shape and material dimensions of the elements described with reference to Figure 2 will be determined by those skilled in the art depending on the circumstances drilling.

Within the framework of the present invention, it is possible to conceive arrangements of the vibration damping device according to FIG. 2, such as for example the insertion of a spring system between the upper disc 17 and the stop 19, etc.

The same type of damping device as that of FIG. 2 can be built outside a drilling head 3, particularly when the drilling head 3 (FIG. 1) has a large diameter on the side 23 lined with diamonds compared to a small body diameter 24 located on the side of the attachment of the head to the drill string 2. A transition collar between these two diameters can indeed serve as a support plate for discs 16, 17 having a hole central adapted to pass around the body 24 and a sufficient external diameter but less than that of the side 23 garnished with diamonds.

FIG. 3 represents a vibration damping device 1 according to the invention arranged on a drill pipe 15 and which can be constituted inter alia by a section of metal tube 26 coaxial with the pipe 15 and external to the latter and by metal discs respectively upper and lower 27, 28 perpendicular to the rod 15 and closing the ends of the tube section 26 while fixing the latter in a known manner to the rod 15 to form a hollow body 128 on the latter . The annular space 126 between rod 15 and tube section 26 can for example be partially filled also with a mixture of rubber balls and steel balls which can be introduced through an orifice 29 of the disc 28, this orifice being able to be closed in a known manner.

According to the invention, it is possible for example to introduce a viscous fluid into the remainder of the annular space 26 not occupied by the aforementioned balls, so as to change the damping characteristics of the device 1. This introduction of fluid or a withdrawal, partial or total can also possibly be carried out during drilling, for example using a pipe coming from the drilling platform and descending, through the orifice 29, to the bottom of the annular space 126 .

On the basis of FIG. 3, it is also conceivable for example that the tube section 26 is metallic and forms the heavy material while the discs 27, 28 are made of rubber or of another relatively flexible material which forms the material of damping and which can be fixed in a known manner to the rod 15 and to the tube section 26. In this case, too, the annular space 126 can possibly be filled at least partially with a damping fluid, possibly air whose pressure and therefore the quantity can be modified using suitable means, such as a pressure reducer, to possibly modify the damping produced by the rubber discs 27, 28 and the tube section 26.

In the case of FIG. 1, the embodiment described above can be supplemented according to the invention for example by a disc 32, shown in broken lines, which can simply rest by its own weight on the mixture of metal balls and rubber disposed in 14 · and partially filling the volume 10. This disc 32 can however also be provided with sealing means with respect to the internal surfaces of the tube sections 8 and to the external surfaces of the conduit 11 so as to be able to pressurize the part of volume 10 located above this disc, the latter, guided for example by the conduit 11, acting in the manner of a piston to compress more or less strongly the mixture of balls and thus to modify the damping characteristics of the vibration absorption element while retaining in case of large amplitudes of oscillations a possibility of displacement to this vibration absorption element until in this volume part above the disc 32, the pressure thus given, for example pneumatically, does not increase the mass inertia of the device.

The damping material can for example also consist of a viscous fluid which sufficiently brakes the movements of the heavy material, with possible rolling of this fluid.

The vibration damping device 1 according to FIG. 2 or 3 can be provided with means known per se so as to be able to adjust the position of the device along the rod and thus to be able to adapt this position for example as a function of conditions of drilling or special vibrations.

In the examples illustrated in FIGS. 1 and 3, the vibration absorption element formed by metal and rubber balls can be supplemented by known means such as supply and suction conduits for these balls to modify the filling the volume 10 or the annular space 126 as a function, for example, of a vibration level recorded by means of a known vibration detector 103 (FIG. 1) or 226 (FIG. 3). The detected vibration level can be compared with one or more vibration thresholds set in a comparison and reference device which is not shown, so that this device, for example, triggers automatically, if a determined threshold is exceeded and according to the vibration damping device used, a modification of the quantity of damping fluid in the device 1, or an adjustment of the position of the device 1, or a compression of the damping material, or a variation in the weight or of the volume of the heavy and / or damping materials, these materials being able for example also to be stored separately in the volume 10 so that the metal balls can be withdrawn separately from the rubber balls which would form inter alia a cushion separated from the balls of metal by a flexible partition.

In addition, the aforesaid comparison device can emit a signal for example when an automatic adjustment is no longer possible and it is necessary to supplement the damping device with other vibration absorption elements or when a critical frequency for the head and / or for the rods appears and that a specific vibration damping device according to the invention must be arranged, etc.

It should be understood that the invention is in no way limited to the embodiments described and that many modifications can be made to these without departing from the scope of the present invention. Thus, the stacking of the discs, described according to FIG. 2, in greater or lesser number can also be carried out in the volume 10 of the device according to FIG. 1. This stacking in this case can possibly be supplemented with granular materials ( heavy and / or damping balls. In either case, spring elements can also be added to give, for example, a prestress to the vibration absorbing element, etc.

Still other means than those described can advantageously be implemented within the framework of the present invention by arranging each time between these means and the drilling head 3 and / or the drill string 2, at the place of fixing of these means, a depreciation material. In addition, the tube sections 8 can be constituted by core tubes known to those skilled in the art.

It is understood that the vibration sensor 103, 226 can be placed at any suitable location on the drill string.

Claims (16)

1. Method for damping vibrations in a drill string (2) placed end to end and driven in rotation in a cavity, in particular in a drill string (2) provided with a drilling head (3) or coring, comprising the possible use of a heavy material element, characterized in that it further comprises: - the selection of at least one material having a shock absorption characteristic and the dosage. by volume or by weight of this damping material and any heavy material, depending on the vibrations to be damped - the addition of this damping material, possibly in association with heavy material, to the drill string in at least a location thereof, and - any adjustment of the above dosage. 2. Method according to claim 1, characterized by the distribution of the damping material and, if necessary, the heavy material in one or more locations along the drill string (2) and by the possible adjustment of this distribution . 3. Method according to either of claims 1 and 2, characterized by the addition of a damping material and optionally a heavy material to the drilling head (3) or coring. k. Method according to any one of Claims 1 to 3, characterized by the introduction of the damping material and / or the heavy material into a hollow body (9, 128) which is connected to the string of rods (2), as well as the possible introduction into this hollow body of a damping fluid, the amount of which may be subject to adjustment. 5. Method according to any one of claims 1 to 4, characterized in that it comprises: - the detection of a level of vibrations in the drill string (2), - the comparison of the level of vibrations detected with a determined maximum threshold, and - if the level of vibration detected is greater than said maximum threshold, a modification of the abovementioned setting. 6. Device for damping vibrations in a drill string (2) placed end to end and driven in rotation in a cavity, in particular in a drill string (2) provided with a drilling head (3) or coring, comprising a vibration absorption element attached to the drill string, characterized in that it comprises at least one absorption element. said vibration which is at least partially made of a damping material. 7. A vibration damping device according to claim 6, characterized in that the vibration absorbing element acts directly on the drilling head (3) and / or coring. 8. A vibration damping device according to either of claims 6 and 7, characterized in that in addition at least one vibration absorption element is arranged along the drill string (2 ). 9. A vibration damping device according to any one of claims 6 to 8, characterized in that the damping material and possibly the heavy material of the vibration absorption element are enclosed in a hollow body (9 , 128) connected to the drill string (2). 10. A vibration damping device according to claim 9, characterized in that in addition a damping fluid is enclosed in the hollow body (9, 128). 11. A vibration damping device according to claim 10, characterized in that it comprises means for modifying the quantity of damping fluid ... 12. A vibration damping device according to any one of claims 9 to 11, characterized in that the heavy material is constituted at least in part by the aforementioned hollow body (128). 13. Device according to any one of claims 6 to 12, characterized in that it comprises means for adjusting the position in or on the drill string (2) of at least one vibration absorption element. 14. A vibration damping device according to any one of claims 6 to 13, characterized in that it comprises means for compressing the damping material. 15. A vibration damping device according to any one of claims 6 to 14, characterized in that it comprises means for varying the weight or volume of the heavy material and / or damping. 16. A vibration damping device according to any one of claims 11 to 15, characterized in that it comprises - means for detecting the level of vibrations (103, 226) in the drill string (2) , - means for setting a vibration threshold, and - actuating means connected to these means for detecting and setting and produced to act in addition on at least one of the means constituted by means for modifying the quantity of fluid, means for adjusting the position of one or more absorption elements, means for compressing damping material and means for varying the weight or volumes of heavy material and / or damping, if the vibration level is above the vibration threshold. e 17. Device according to either of claims 9 and 10, characterized in that the aforesaid hollow body (9) can be constituted by at least one core barrel.