EP0125993B1 - Centralizer for a tool in a cased well, especially for deviated wells - Google Patents

Description

The invention relates to devices for centering a tool in a cased well, in particular for a deviated well.

Many works carried out deep in the wells require good centering of the tool. This is the case, in particular, when measuring the transverse dimensions of the well, described in French Patent Application No. 81 24021 published 24.06.83 under No. 2,518,638, filed on December 22, 1981 in the name of SOCIETE DE SCHLUMBERGER ELECTRICAL PROSPECTION.

The development of fully satisfactory centering devices raises technical difficulties. First, the production column of a well has localized variations in diameter, at the joints, and also at the valves located at the well head. It is therefore necessary that the centering device can adapt to these variations in diameter. Such an adaptive centering device is often called in the technique "centralizer".

Besides this, the modern trend, especially for drilling at sea, leads to deviated wells, which, in one or more times, deviate significantly from the vertical. It follows that the operation of the centering device is disturbed by the effect of gravity which it then feels laterally.

Finally, to achieve centering, the device must naturally rest on the walls of the well. In many devices of the prior art, the support on the wall of the casing is effected by sliding. This is the case in particular for the centralizers described in American Patents No. 3,555,689 and No. 3,915,229 (to which corresponds the French Patent published under No. 2,267,442). This type of support is no longer entirely satisfactory, in particular in the case of deviated wells, since it tends to alter the internal surface condition of the casing, and thereby accelerate corrosion; moreover, it tends to limit the critical angle of deflection from which the tool no longer advances under the effect of its own gravity.

In order to remedy these drawbacks, a centralizer has been proposed in which the contact with the wall of the tube is ensured by rollers (Article entitled “Improved Technique for Logging High-Angle Wells •, by MW BRATOVICH, WT BELL, KD KAAZ, published under the reference SPE 6818 by the American Institute of Mining Metallurgical Petroleum Engineers Inc.). FIG. 3b of this document shows a centering device which comprises a central bar capable of being integrated into the chain for lowering the tool into the casing, two movable slides with limited sliding on this central bar, a series of radial structures carries -galet, of general triangular geometry, defined by arms articulated on the two slides, a series of rollers each mounted free in rotation on one of the radial structures, so that its periphery projects radially outwards, and elastic return means acting to urge the rollers radially outwards. Although it allows certain work to be carried out in deviated wells, this centralizer is not without drawbacks.

First of all, its centering or bearing force on the walls of the tube tends to decrease too rapidly when the diameter of the casing increases. Then, to comply with overall diameter constraints in the retracted position, for example less than 50 mm, the rollers must be given a small diameter; these then rotate very quickly during the descent into the well, which considerably reduces their lifespan. Finally, this centralizer is subjected to severe shocks each time it passes over a casing joint, shocks which quickly put it out of service.

The present invention solves the technical problems encountered with this prior art roller centering device.

A first object of the present invention is to provide a centering device which has an enlarged roller diameter, while respecting the same constraints of overall diameter in the retracted position.

Another object of the present invention is to provide a device whose radial bearing force on the casing is substantially constant over a wide range of casing diameter.

Yet another object of the present invention is to provide a device which has, in all circumstances, an exterior surface without roughness, thus avoiding that shocks during its descent do not quickly put it out of service.

The objects of the invention are achieved by the characteristics which will now be set out.

According to an essential characteristic of the present invention, each roller is mounted to rotate in an inclined plane with respect to the radial plane of the roller-bearing structure which supports it, and the central bar is hollowed out, so as to partially accommodate the rollers when said roller support structures are retracted to the maximum on the central bar.

In a preferred embodiment, each roller-bearing structure comprises a yoke in the general shape of a U, on the branches of which the external ends of the arms are articulated, articulated moreover on the two slides, while the roller is mounted on the bottom of the U, on the internal side thereof, so that the external periphery of the roller projects slightly outside the associated roller support structure, substantially in the radiated plane thereof; for their part, the bottoms of the U of the different yokes are offset at the periphery in the same direction with respect to the radial plane of each roller-holder structure, when one rotates around the central bar.

According to another characteristic of the invention, the elastic return means comprise on the one hand, two compression springs, which bear between the sliders and shoulders of the central bar which are located on either side of the two sliders, respectively, in order to urge these two sliders one towards the other, and, on the other hand, in parallel on the arms, between the slide and the bearing carrier concerned, a curved leaf spring, with concavity turned inward.

According to yet another characteristic of the present invention, the yokes are shaped externally to define together a substantially cylindrical periphery, when the roller-bearing structures are retracted to the maximum on the central bar.

Very advantageously, the angle of inclination of the rollers relative to the radial plane concerned is of the order of 10 °.

• la figure 1 illustre schématiquement une chaîne de descente d'un outil dans un tubage, avec des dispositifs de centrage selon la technique antérieure ;
• la figure 2 illustre schématiquement en perspective, un dispositif de centrage selon la présente invention ;
• les figures 3 et 4 sont deux vues de dessus et en coupe longitudinale de l'un des coulisseaux selon la présente invention ;
• les figures 5 à 7 sont trois coupes transversales du coulisseau des figures 3 et 4 ;
• les figures 8 et 9 sont deux vues respectivement de côté et de dessus d'une partie d'une structure radiale porte-galet, avec sa chape et l'une de ses lames-ressorts ;
• la figure 10 est une vue en coupe transversale du dispositif de centrage selon l'invention, dans sa position entièrement rétractée ; et la figure 11 est une vue en bout correspondant aux figures 8 et 9.

Other characteristics and advantages of the invention will appear on examining the detailed description which follows, as well as the appended drawings, in which:

• Figure 1 schematically illustrates a chain for lowering a tool into a casing, with centering devices according to the prior art;
• Figure 2 schematically illustrates in perspective, a centering device according to the present invention;
• Figures 3 and 4 are two views from above and in longitudinal section of one of the slides according to the present invention;
• Figures 5 to 7 are three cross sections of the slide of Figures 3 and 4;
• Figures 8 and 9 are two views respectively from the side and from above of a part of a radial roller carrier structure, with its yoke and one of its leaf springs;
• Figure 10 is a cross-sectional view of the centering device according to the invention, in its fully retracted position; and FIG. 11 is an end view corresponding to FIGS. 8 and 9.

In FIG. 1, the symbol T generally designates a casing, inserted in a deviated well which successively meets various formations of the subsoil. Inside the casing is placed a chain for lowering a tool, consisting of successive elements 1 and 2, pivotally connected to one another. An element 3, provided at its two ends with seals 3A and 3B, allows angular movement. The seal 3B is connected to a first centering device 4, followed by a tool 5, then a second centering device 6, and a new tool 7.

The tool 5 is for example the device for measuring the transverse dimensions of a hole described in French Patent Application No. 81 24021, published under No. 2,518,638, already cited. The tool 7 then includes a reference sensor, intended to measure the speed of propagation of the acoustic waves in the medium which fills the casing.

In FIG. 1, the schematic representation given for the centering devices 4 and 6 corresponds to the centralizer described in the article reference SPE 6818, already cited.

We will now look at Figure 2, which schematically shows a centering device or centralizer according to the present invention.

A central bar 10 is provided at its two ends with threads (not shown) for fixing two parts 12 and 13 forming opposite shoulders. These parts 12 and 13 will also serve to ensure the connection of the central bar in the descent chain, on the one hand, on the side of the universal joint 3B, on the other hand, on the side of a tool, for example ( figure 1). It will also be noted in FIG. 1 that two centering devices are generally necessary.

On the central bar 10 slide two slides 20 and 30, which will be described in more detail below.

These slides are used to establish three radial roller-bearing structures, illustrated as a whole at 40 and 40A (the third structure 40B, located at the rear, is not shown to clarify the drawing). These three structures have the same constitution, and are distributed at 120 ° from one another around the central bar 10 and slides 20 and 30. We will only describe in the following the structure 40.

This comprises firstly a first pair of arms 71 and 72, which are pivotally articulated on the slide 20, and a second pair of arms 73 and 74, similarly articulated on the slide 30. At their other ends, the arms 71 and 72 are pivotally articulated on one side of a roller carrier yoke 50. The other two arms 73 and 74 are similarly pivoted on the other side of the yoke 50. Both pivot axes provided in the yoke are parallel. These axes appear at 67 and 68 in FIG. 8.

Again in FIG. 2, one of the sides of the yoke 50 is fixed to a curved leaf spring 41, the other end of which is guided in axial sliding in the slide 20. It is the same for the other side with curved leaf spring 42.

Each yoke such as 50 supports a roller, which is mounted for rotation on it.

Finally, the elastic return means are completed by two springs 17 and 19 bearing between the extreme stops 12 and 13 and the slides 20 and 30.

Reference will now be made to FIGS. 3 to 7, which illustrate, in more detail, the structure of one of the sliders, supposed to be the slider 20. In its intermediate part, the slider 20 is provided with three protuberances arranged at the periphery at 120 ° one from the other, and which will each serve to define the pivot axis of a pair of arms such as 71 and 72. Take, for example, the projection or protuberance 25, which is radially sized large enough to allow the establishment of a bore 27 serving as a pivot axis for the two bars 71 and 72. On the top, an intermediate recess 26 is provided to allow the housing of the leaf springs such as 41 in the fully position retracted from the centering device. We note equal ment, in Figure 3, the other pivot axes 27A and 27B.

The slide 20 is also provided at its left end with a tip 21 internally forming a stop 28 for the spring 17. This tip is provided, with the same planes of symmetry as the protrusions 25, with longitudinal recesses distributed at 120 ° one from the other (Figures 3, 4, 5 and 6). Completely outside, the recess 22 is provided, which extends over the entire length of the end piece, thus allowing the end of the leaf spring 41 to be housed when the device is fully retracted. Over a part of its length, from the free end, the recess 22 is provided with lateral grooves 23. These allow sliding housing of the transverse rod 43 (FIG. 9) mounted at the end of the curved leaf spring 42 concerned. Over the length of the grooves 23, the recess 22 is traversing at 24, to facilitate the machining of the grooves. Finally, in its lower part (FIG. 4), the end piece 21 is provided with a housing 25 designed to receive a pin capable of immobilizing the slide pivotally relative to the central bar, by cooperating with a groove homologous to the bar. central (if such immobilization is desired). There is also an orifice 29 which allows the passage of the fluid contained in the casing towards the inside of the slide, in order to equalize the pressures.

We now understand how the pairs of arms such as 71 and 72 are pivotally articulated on their slide, and also how the curved leaf spring 41 is guided to slide on the same slide.

Figures 8, 9 and 11 show in more detail the arrangement made on the side of one of the yokes, such as 50. As previously indicated, the axes 67 and 68 serve as other pivot points for the pairs of arms 71 and 72 on the one hand. 73 and 74 on the other hand. This fixing is carried out in the two lateral parts 51 and 52 of the U-shaped yoke 50. These lateral parts are extended, in the radial plane of the roller-bearing structure concerned, by two plates, one of which 61 appears well in FIG. 8. The plate 61 is provided with a protuberance 62 which serves as a fulcrum at the end of the leaf spring 42. The latter is moreover rigidly fixed to the yoke 50 by brazings 64 and 63. At this level, it will be recalled that the centralizing device of the prior art has radial structures of triangular geometry. The structure according to the invention is however only roughly triangular. Those skilled in the art will indeed understand that the articulation points 67 and 68 of the arms on the yoke are quite distant from each other, which allows, in combination with the role played by the leaf springs 41 and 42 , a much more flexible suspension of the yoke 50 and the roller 80 which it carries (this roller is not shown in FIGS. 8, 9 and 11). Figures 8, 9 and 11 also show a very important feature of the invention. The roller carrier yoke 50 houses the roller on the bottom side 53 of its U, more precisely on the side of the inner face 56 thereof, when we observe things from the center of the structure. In addition, the mounting in lateral offset of the yoke 50 is accompanied by an inclination of its inner face 56 and therefore of the plane of the roller, relative to the radial plane defined by the roller-bearing structure concerned. The angle of inclination in question is of the order of 10 °.

As shown in FIG. 2, the tread of each roller such as 80 projects slightly outside the associated roller support structure, and inside the U defined by each yoke 50, that is to say - say substantially by the radial plane of the roller-bearing structure concerned.

Finally, the bottoms 53 of the U of the different yokes such as 50 are offset on the periphery in the same direction relative to the general direction defined by the leaf springs 41 and 42 (that is to say the radial plane of the structure roller holder), when turning around the central bar 10.

It is then very advantageous for the external surfaces 54 of the yokes 50 to be shaped so as to define together a substantially cylindrical periphery, when the roller-bearing structures are retracted to the maximum on the central bar. In other words, the outer contour 54 of the yoke is curved in such a way that it approaches the axis of the centering device when one moves away from the radial plane of the associated roller support structure. We can say that the yoke 50 is therefore placed in lateral offset, in a slightly closed position towards the inside.

Reference will now be made to FIG. 10 which is a cross section of the centering device according to the invention, in its fully retracted position. This figure also makes it possible to better understand the mounting of each roller on the associated yoke.

It will be observed first of all that the recesses 11, 11A and 11B of the central bar 10, illustrated as flats, are used to partially accommodate the rollers, thus helping to minimize the size of the device in the fully retracted position. Figure 10 similarly shows the substantially cylindrical peripheral contour in the retracted position.

The central bar 10 is internally bored at 15, to let conductors pass to a tool located downstream.

We will now focus on the assembly of the roller 80. The inner face 56 of the yoke 50 is provided with an annular central shoulder note 59. This supports a pad 81. And it is on the pad 81 that the actual roller 80. Note the hollow shape of the roller, which allows it to be held by a flange 83, integral with a rod 82 which engages in the bore of the yoke 50, where it is fixed by a key 54. Such an assembly allows easy rolling of the roller, while helping to minimize its size, and thereby that of the entire centralizing device in the fully retracted position.

The periphery of the roller 80 is chosen in one suitable material to allow it a long service life under the harsh conditions encountered inside the casings.

For the same reasons, it is advantageous that all of the external parts of the yoke 50, as well as the curved leaf springs 41 and 42 resist well the wear likely to be generated by episodic contacts with the wall of the casing. .

In the currently preferred embodiment, as just described, the sliders come into contact, or almost in contact, with their respective stops 12 and 13 when the roller support structures are in their fully retracted position. In the other positions, the two slides are free to move together on the axis defined by the central bar 10, against the springs 17 and 19.

At full opening, the angle of the inner arms such as 71 and 72 on the axis of the central bar is of the order of 30 °.

This full opening is defined by all of the elements of each radial roller carrier structure, namely its bars, the geometry of the curved leaf springs 41 and 42, as well as the characteristics of the springs 17 and 19 taking account of their stops.

In addition, it has been observed that the arrangement of the springs 17 and 19, according to the present invention, makes it possible to obtain at the level of the rollers a radial force which increases with the diameter of the casing. For their part, the curved leaf springs such as 41 and 42 provide a radial force which, on the contrary, decreases with the diameter. By combining the two effects, it is possible to obtain a substantially constant radial centering force, independent of the diameter, over a fairly wide range of diameters (of course less than the diameter obtained when the two elastic systems constituted by the compression springs and the leaf springs reach their rest position). This characteristic is very important in highly deviated wells, where two of the roller-bearing structures will have to support the radial component, relative to the casing, of the weight of the centering device as well as of the tool with which it cooperates.

The Applicant currently considers that it is preferable to immobilize the slides with pivoting with respect to the central bar, as previously indicated. A variant of the invention consists, on the contrary, in leaving these slides 20 and 30 free to pivot on the central bar. It has in fact been observed that it suffices to slightly round off the edges of the flats 11, 11A and 11B formed on the central bar so that the rollers can come to fit themselves in the fully folded position, even if the position of the two slides at the time of approach does not exactly correspond to the desired geometry. In general, it is possible to machine the central bar to facilitate the insertion of the rollers on the recesses which it carries, when the roller-bearing structures approach their fully retracted position.

The above description relates to a single centering device. As shown in Figure 1, most applications require two centering devices, placed on either side of a tool 5, another tool 7 can however be installed cantilevered at the free end of the descent chain. This naturally falls within the scope of the invention.

Claims (10)

1. A device for centering a tool inside a cased well, the device being of the type comprising :

a central bar (10) suitable for being integrated in a string for lowering the tool inside the tubing and having two slides (20, 30) which are slidable over a limited range (12, 13) of said central bar ;

a series of wheel-carrying structures (40, 40A, 40B) of generally triangular geometry defined by arms (71 to 74) which are hinged to the two slides ( 20, 30) ;

a series of wheels (80, 80A, 80B), each wheel being mounted free to rotate on one of the radial structures (40, 40 A, 40B) in such a manner that its periphery projects radially outwardly ; and resilient return means urging the wheels radially outwardly ;

characterized in that each wheel (80, 80A, 80B) is mounted to rotate in a plane which is inclined relative to a radial plane through the wheel-carrying structure (40, 40A, 40B) on which it is mounted, and in that the outer surface of the central bar (10) is recessed to partially receive the wheels when said wheel-carrying structures are fully retracted against the central bar.

2. A device according to claim 1, characterized in that each wheel-carrying structure (40) comprises a generally U-shaped fork (50) having two tines on which are hinged the outer ends of the arms (71, 74) which are also hinged to the two slides (20, 30), while the wheel (80) is mounted on the bottom of the U on the inside thereof (56) in a manner such that the outer periphery of the wheel projects slightly beyond the associated wheel-carrying structure, substantially in the radial plane therethrough, and in that the bottoms (53) of the Us of the various forks are peripherally offset relative to the radial plane through each wheel-carrying structure and in the same direction when going round the central bar (10).

3. A device according to claim 1 or 2, characterized in that the resilient return means comprise both a pair of compression springs (17, 19) which act between the slides (20, 30) and shoulders (12, 13) which are situated on the central bar on the side of each of the slides which is opposite to the other slide in such a manner as to urge the slides towards each other, and in parallel with the arms between each slide and the relevant wheel-carrying fork, a curved spring blade with its concave side facing inwardly.

4. A device according to claim 2 or 3, characterized in that the forks are shaped on the outside (53) so that together they define a substantially cylindrical periphery when the wheel-carrying structures are fully retracted against the central bar.

5. A device according to any one of claims 1 to 4, characterized by the fact that the wheels are inclined at an angle of about 10°.

6. A device according to any one of claims 1 to 5, characterized in that the two slides (20, 30) are prevented from rotating about the central bar.

7. A device according to any one of claims 1 to 5, characterized in that the two slides (20, 30) are free to rotate about the central bar.

8. A device according to claim 7, characterized in that the central bar is machined to facilitate insertion of the wheels into recesses included thereon while said. the wheel-carrying structures approach their fully retracted position.

9. A device according to any one of claims 1 to 8, characterized in that the central bar (10) includes a through bore (15) to pass conductors towards a tool situated down stream therefrom.

10. A device for centering a tool in a casing, characterized in that it includes two devices according to any preceding claim, said devices being placed on either side the tool.

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