EP0069019A1 - Apparatus for well perforation - Google Patents

Abstract

The invention relates to a perforation device for welding comprising a support (25) and encapsulated shaped charges (26) fixed unidirectionally on this support. Positioning rings (35, 36) are snapped onto loads (26) at regular intervals along the support (25). These rings have a rounded external surface on which the perforating device can tilt to a correct equilibrium position for which the front faces of the loads are applied against the casing (13). Use for perforators comprising loads fixed on the rear face of a support bar whose front face is applied against the casing.

Description

The invention relates to perforation devices used in soundings and more particularly to a perforation device used through a production column and carrying encapsulated charges oriented in at least one direction.

There are many types of encapsulated charge perforators that can be lowered into the boreholes through the production column. One of them described in the patent of the United States of America No. 3,965,993 (J. Lavigne, P. Chesnel and G. Bouguyon), comprises a bar forming a support on which are fixed, by their front part , encapsulated shaped charges oriented in a single direction. The performance of such a unidirectional device is excellent provided that the front face of the bar is correctly applied against one side of the casing, the axes of the loads being directed towards this side.

During detonation, the spacing is then minimal between the casing and the front face of the charges, this position providing the best perforation performance. In addition, it is in this firing position that the deformation of the bar and the damage to the casing are the least significant and that a maximum number of charge covers remain attached to the bar after detonation.

The perforating device described in U.S. Patent ^No. 3,965,993 is commercially used with a magnetic positioning system placed at the head of the device. This system is formed by permanent magnets arranged on the side of the support bar to apply the front face of the bar against the casing. Unfortunately it may be that the strength of the magnets is insufficient to correctly apply the support bar against the casing. This application of the bar against the casing may be incorrect if the magnets have lost their strength or in the case of a large number of loads placed on a long support. The addition of another magnetic positioning system at the bottom of the support is not possible because the debris of the load envelopes would agglomerate after the shooting on this magnetic member causing risks of jamming during the ascent. bar surface and remaining load covers.

Another positioning system for a perforation device of the same type is described in US Patent No. 3,858,651. Safety pin-shaped springs push the support bar of a perforator against one side of the casing while resting on the other side. Such a system presents risks of jamming in the casing or the production column. In addition, after firing, debris can accumulate on the lower spring which partially closes the casing. This possible accumulation of debris further increases the risk of entrapment.

The object of the invention relates to an improved perforation device whose positioning is improved and which presents reduced risks of jamming.

According to the invention, a drilling perforation device comprises: an elongated support adapted to be moved in the drilling and encapsulated hollow charges fixed along the support so that their axes are oriented in the same direction perpendicular to the longitudinal direction of the support. At least one positioning member, fixed to a receiving load, has a cross section having a rounded external profile so that the perforating device can tilt on this rounded profile, around the longitudinal direction, towards an equilibrium position for which the front face of the device is applied against one side of the borehole and the axes of the loads are directed: towards this side.

The positioning member is fixed on a receiving load located at the lower part of the support. Other identical positioning members can be fixed on receiving loads situated at determined intervals along the support.

Generally magnetic means placed on a predetermined side of the device at the upper part of the support tilt the device to apply its front face against one side of the borehole casing. In addition, the external profile of the positioning member is substantially circular and eccentric with respect to the center of gravity of the device so that, in deviated soundings, the device rocks by gravity on this external profile towards the equilibrium position.

Preferably, the positioning member is a ring of substantially spherical external surface and comprising elastic fingers adapted to engage by snap-fastening on the receiving load. The fingers are produced by cutting out regularly distributed radial slots in the crown. Multiple fingers of small width are thus obtained which break into small elements during detonation.

These positioning members are particularly advantageous in the case of devices comprising a bar-shaped support having a front face adapted to be applied against one side of the borehole and a rear face against which the loads are fixed from the front.

• - la figure 1 est une vue d'un dispositif de perforation selon l'invention, représenté dans un sondage,
• - la figure 2 est une coupe transversale montrant un dispositif de l'art antérieur ayant une position incorrecte dans un sondage,
• - la figure 3 est une coupe transversale partielle montrant un organe de positionnement de l'invention fixé sur une charge ; et
• - la figure 4 est une vue de face de l'organe de positionnement de la figure 3 pris isolément.

The characteristics and advantages of the invention will emerge more clearly from the description which follows, given by way of nonlimiting example with reference to the appended drawings in which:

• FIG. 1 is a view of a perforation device according to the invention, represented in a survey,
• FIG. 2 is a cross section showing a device of the prior art having an incorrect position in a borehole,
• - Figure 3 is a partial cross section showing a positioning member of the invention fixed on a load; and
• - Figure 4 is a front view of the positioning member of Figure 3 taken in isolation.

With reference to FIG. 1, a perforation device 10 is suspended in a borehole 11 at the end of an electric cable 12. The borehole 11 is fitted with casing 13 surrounded by a ring of cement 14 and a production column 15 fixed to its lower part, in a packer 16. The cable 12 is wound on the surface on a winch (not shown) which makes it possible to move the device 10 along the borehole. In the case of such perforation operations, the cable 12 generally comprises a single insulated conductor connected to surface equipment (not shown) capable of supplying electric current for igniting the perforating device.

The perforation device 10 connected to a cable head 17 comprises a conventional detector of casing joints 20, a magnetic positioning system 21 and a support 22 including, between a head 23 and a lower end piece 24, one or more bars 25 fixed end to end.

Encapsulated shaped charges 26 are fixed at regular intervals along the internal face of the bars 25 so that their axes are oriented in the same direction, perpendicular to the longitudinal direction of the bars. The magnetic positioning system 21 comprises permanent magnets placed on one side of the system to apply the external face of the bars 25 against the wall of the casing. The charges are fired by means of a detonating cord 27 which passes through a passage at the rear of each charge. The upper end of the cord 27 is connected to an electric detonator 30 fixed to the bar 25. The electrical conductors of the detonator 30 are connected to the head 23 so as to allow the sending of an electric firing current in this detonator from the surface via cable 12.

The perforating device 10 and the fixing of the charges 26 on a bar 25 are described in more detail in the already cited patent of the United States of America No. 3,965,993. As shown in FIG. 3, each charge comprises at the front a thread 31 which is screwed into a tapped hole in the bar 25. At the rear part of each charge is made a passage 32 for the detonating cord 27. The front face convex 33 of the bar 25 is intended to be applied against the inside of the casing.

We have seen that, under certain conditions, the known perforation devices do not place themselves correctly in the casing, in particular in inclined boreholes, when the number of charges is large or if the strength of the magnetic positioning system has weakened . Such an incorrect position is shown in FIG. 2, in an inclined casing 13, for a device of the prior art comprising loads 26 'fixed on a support bar 25'. The front face 33 ′ of the bar is not applied against the casing 13 and the axis xx of the loads is not directed towards the side of the casing against which comes supports the perforation device. The spacing e between the front of the loads and the casing is large and the side of the loads 26 ′ comes to rest on the lower part of the casing at points A and B. The arrow P ′ represents the component of the weight of the perforating device in the cross section, this component being applied to the center of gravity G '. It can be seen that the support base AB of the device on the casing is wide so that neither the component P 'nor the torque due to the magnetic positioning system has the effect of tilting the device around the longitudinal direction towards the correct shooting position for which the XX axis is directed downwards. In the device of the invention, incorrect positions are avoided because such tilting is possible.

For this purpose, the perforation device 10 comprises at least one positioning crown 35 (FIG. 1) fixed on a receiving load located at the lower part of the support 22. Other identical positioning crowns such as 36 are fixed on loads receptors located at regular intervals along the support, for example at the bottom of each bar 25. The crown 35 is shown in more detail in FIGS. 3 and 4.

The crown 35 is fixed by snap-fastening to a receiving charge 26 after screwing this charge onto a bar 25 but before fitting the detonating cord 27. By analogy, the same conventions "front" and "rear" defined with respect to the axis XX 'previously mentioned, will be used for the load and the crown assuming the latter snapped onto the load.

Referring to Figures 3 and 4, the crown 35 has a spherical outer surface 40 whose center C is substantially coincident with the center of curvature of the convex front face 33 of the bar 25. This crown comprises an annular rear portion 41 delimited towards the exterior by a flat surface 42 and extending forwards by a recessed part 43 which surrounds the load 26. The annular part 41 of the crown has a frustoconical internal surface 44 which bears on a rear shoulder of the load 26 The cutting of this annular part allows the rear part of the charge to protrude from the crown, thus leaving uncovered the passage 32 of the detonating cord.

In the hollowed out part 43 are cut eight radial slots 45 regularly distributed around the crown. These slots 45 open from the front of the crown to the flat surfaces 49 of the rear annular part. These radial slots 45 form between them eight fingers 46 capable of deviating elastically from the center C during the latching. The elastic fingers 46 have at their ends lugs 47 adapted to engage in a recessed portion of the load cover 26. The lugs 47 have inclined surfaces 48 which allow the introduction of the crown 35 on the receiving load 26 spreading the fingers 46.

If the perforation device 10 takes, in the borehole, an incorrect position similar to that of FIG. 2, the part of this device which comes to bear against the casing is no longer formed by a broad base AB but by the external profile rounded positioning rings 35 and 36. The support base is then practically punctual and a very low torque due to the magnetic system 21 is enough to tilt the device to the correct position for which the front face 33 is pressing against one side casing with the axes Mr perpendicular to this side.

In a cross section such as that of FIG. 3, the center of gravity of the device is located at a point G situated forward relative to the center C of the external surface. In other words, the circular external profile of a crown 35 is eccentric rearward relative to the center of gravity G. Consequently, in a borehole inclined relative to the vertical, the radial component P of the weight is sufficient, by itself, to tilt the perforation device, on this circular profile, towards the equilibrium position indicated in FIG. 3. In fact, this force of gravity is added to the magnetic force of the positioning system 21 to bring back the perforating device in the correct position.

Note that crowns 35 and 36 only slightly increase the amount of debris left in the borehole. Indeed, these crowns are few and represent a small amount of material. These crowns are made of the same steel, breaking into small elements, as that used for the envelopes of loads. The large number of radial slots 45 made in the crown further reduces the size of the debris.

The embodiment which has just been described can obviously be the subject of numerous variants without departing from the scope of the invention. The external shape of the crown, in particular, is not necessarily spherical and one could conceive positioning elements with cylindrical external shape provided that, in cross section, that is to say perpendicular to the longitudinal direction, the profile external is appropriately rounded.

Claims (6)

1. Perforation device for sounding comprising an elongated support (22) adapted to be moved in the sounding, sealed encapsulated hollow charges (26) fixed along the support so that their axes (XX ') are oriented in the same direction perpendicular to the longitudinal direction of the support, and positioning means (21) placed at the upper part of the support to apply the face (33) of the device located at the front of the axes (XX ') against one side of a casing installed in the borehole, characterized in that it comprises at least one positioning member (35) fixed to a receiving load spaced longitudinally from the positioning means, said member comprising a cross section having a rounded external profile (40) around the receiving load to facilitate tilting of the device on said rounded profile, around the longitudinal direction, under the effect of the positioning means, towards the equilibrium position for which the face has vant (33) of the device is applied against one side of the casing, the axes (XX ') of the loads being directed towards this side. 2. A perforation device according to claim 1, characterized in that it comprises other identical positioning members (36) fixed respectively on receiving charges located at determined intervals along the support (22). 3. Perforation device according to one of claims 1 and 2, characterized in that said rounded external profile (40) of the positioning member (35) is circular and eccentric relative to the center of gravity (G) of the device so that, in the deviated soundings, gravity is added to the positioning means to tilt the device on this external profile towards the equilibrium position. 4. A perforation device according to one of claims 1 to 5, characterized in that said positioning member is a ring of substantially spherical external surface adapted to engage by snap-fastening on the receiving load. 5. A perforation device according to claim 4 in which the support (22) is a bar (25) having a front face (33) adapted to be applied against one side of the borehole, and a rear face against which are fixed, by l 'front, said loads (26), characterized in that said crown comprises: - A rear part (41) comprising a bearing surface (44) on the rear of the receiving load (26) and a cut leaving uncovered the passage (32) of a firing cord at the rear of this charge; and - A hollowed-out part (43) surrounding the load and comprising elastic fingers (46) having at their front ends internal latching lugs (47) adapted to engage in a part set back from the receiving load in order to fix the crown on this charge. 6. A perforation device according to claim 5, characterized in that said elastic fingers are obtained by cutting in said recessed part (43) radial slots (45) regularly distributed over its periphery to produce multiple fingers (46) and weak width adapted to break into small elements when the detonation of the charge.

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