Wave seal to resist extrusion during equalization

The present invention provides for dynamic sealing in a flow control device. In an embodiment, the flow control device comprises a closure sleeve adapted to slide over the tubing hole. The closure sleeve has a front edge having a wave-like surface. One or more seals are mounted downstream of the tubing hole. The one or more seals cooperate in a fluid-tight manner with the closure sleeve. A protective sleeve is mounted in alignment with the closure sleeve and proximate to the one or more seals. The protective sleeve has a top edge adapted for mating engagement with the wave-like surface of the front edge of the closure sleeve. A return mechanism is provided for automatically returning the protective sleeve to a covering position in which the protective sleeve covers the first seal when the first seal is not covered by the closure sleeve.

FIELD OF THE INVENTION

The present invention relates to the dynamic sealing of pressure ports. More specifically, the present invention provides an apparatus adapted to prevent seal extrusion from occurring during the sealing and equalizing of pressure ports.

BACKGROUND OF THE INVENTION

Variable flow rate valves as well as two position on-off valves, such as slidably-mounted sleeve valves, play an essential part in optimized well management in oil wells of recent design. It is thus important for them to offer good reliability so that they can operate without maintenance for several years. Any maintenance on such valves is costly (removal and re-insertion of the production tubing), and it results being interrupted, which goes against the object that they are supposed to achieve (optimized well profitability).

One of the essential problems lies in the need to provide dynamic sealing gaskets on the production tubing, on either side of the holes formed therein, so that the valve is properly closed when the closure sleeve occupies the corresponding position.

Such dynamic sealing gaskets are inevitably made of a relatively soft material such as an elastomer or plastic. They are thus very fragile. In particular, they are very sensitive to wear, to abrasion, and to fatigue, and they are very poor at withstanding the flow of the petroleum fluid.

An additional problem appears when the valve is opened after being closed for a certain amount of time. There is then a pressure difference that is sometimes large between the dynamic pressure inside the production tubing and the higher or lower static pressure outside the tubing in the underground reservoir being tapped. On valve opening, the pressure equalization that tends to occur between the outside and the inside (or inside to outside) of the production tubing immediately imparts a high flow rate to the petroleum fluid. The high-rate flow sweeps the surface of the sealing gasket. If no particular precaution is taken, the gasket is then torn away or else it wears very rapidly.

In an attempt to remedy that drawback, it is common to limit the rate of the flow reaching the sealing gasket in question by interposing rings (generally made of metal or of polytetrafluoroethylene) between the gasket and the holes provided in the production tubing. However, such rings are not very effective, and they do not prevent the gasket from suffering accelerated damage as a result of the valve being opened.

SUMMARY OF THE INVENTION

In an embodiment, the present invention provides a flow control device for controlling the flow rate through tubing placed in an oil well. The tubing includes at least one hole therethrough.

The flow control device comprises a closure sleeve adapted to slide over the tubing hole (but can also slide inside the tubing hole). The closure sleeve has a front edge having a wave-like surface. One or more seals are mounted downstream of the tubing hole. The one or more seals cooperate in a fluid-tight manner with the closure sleeve. A protective sleeve is mounted in alignment with the closure sleeve and proximate to the one or more seals. The protective sleeve has a top edge adapted for mating engagement with the wave-like surface of the front edge of the closure sleeve. A return mechanism is provided for automatically returning the protective sleeve to a covering position in which the protective sleeve covers the first seal when the first seal is not covered by the closure sleeve.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention provides an improvement to U.S. Pat. No. 6,325,150 (the '150 patent), issued on Dec. 4, 2001, and incorporated herein by reference. More specifically, the present invention provides an improvement to the seal protector described in the '150 patent.

It should be understood that the flow control device upon which the seal protector of the '150 patent is located is exemplary and not limitative of the devices for which the seal protector can be used to advantage. Likewise, the present invention is not so limited. However, for purposes of illustration, the present invention will be described with reference to the flow control device of the '150 patent.

InFIG. 1of the '150 patent, reference10designates an oil well in production, only a bottom region of which is shown. It should be noted that said bottom region may extend vertically, as shown, or horizontally, or on a slope, without going beyond the ambit of the invention. When the flow rate control device is placed in a horizontal or deviated region of a well, the expressions such as “downwards” and “upwards” used in the following description then mean respectively “away from the surface” and “towards the surface”.

The walls of the oil well10are reinforced with casing12. In the region of the well shown inFIG. 1, the casing12is perforated at14so as to cause the well to communicate with a natural deposit of petroleum fluid (not shown).

To enable the petroleum fluid to be conveyed to the surface, production tubing16is received coaxially in the well10over its entire depth. The production tubing16is made up of a plurality of tubing segments interconnected end-to-end. One of the segments, shown inFIG. 1, forms the body of the flow rate control device18of the invention. To simplify the description, the expression “production tubing” is used below to cover both the entire string of tubing, and also the specific segment of tubing.

Internally, the production tubing16defines a channel20via which the petroleum fluid rises towards the surface. The annular space22defined between the production tubing16and the casing12of the well10is closed, on either side of the flow rate control device18by annular sealing systems (not shown). Therefore, the petroleum fluid coming from the natural deposit (not shown) and admitted into the well via the perforations14can rise to the surface via the central channel20only by flowing through the flow rate control device18.

Essentially, the flow rate control device18comprises at least one hole24formed in the production tubing16, a closure sleeve26, and drive means28.

In practice, the flow rate control device18comprises a plurality of holes24distributed uniformly over the entire circumference of the production tubing16. For example, each of the holes24has a shape that is elongate in the axial direction of the tubing. The holes24may however be of any number or of any shape without going beyond the ambit of the invention.

The closure sleeve26is mounted on the production tubing in a manner such that it can move parallel to the axis of the production tubing. More precisely, the closure sleeve26is suitable for moving between a “bottom” or “front” position shown inFIGS. 1 and 3, corresponding to the flow rate control device18being closed, and a “top” or “rear” position (FIG.2), corresponding to the device18being fully open. Between these two extreme positions, the closure sleeve26may be moved continuously so as to vary the through section of the flow rate control device18and, as a result, so as to vary the flow rate of the petroleum fluid flowing through the device.

As shown, the closure sleeve26is mounted on the outside of the production tubing16. However, the flow rate control device18of the invention is not limited to this mounting configuration, and it also covers configurations in which the closure sleeve26is placed inside the production tubing.

The drive means28comprise an actuator mounted outside the production tubing16. The actuator, which is, for example, of the electromechanical type or of the hydraulic type, is suitable for moving the closure sleeve26continuously and in controlled manner parallel to the axis of the production tubing16as represented diagrammatically by arrow F in FIG.1.

As mentioned above, installing the closure sleeve26outside the production tubing16makes it possible to simplify the device and to facilitate assembly thereof. The actuator can thus act on the closure sleeve without it being necessary for it to pass through the production tubing. In addition, the various parts can be assembled together by being fitted together axially, with the closure sleeve26being formed in one piece, and the corresponding segment of production tubing16being in one piece as well.

The drive means28act on the closure sleeve26via a link part29which may be of any shape without going beyond the ambit of the invention.

Sealing means are provided on the production tubing16on either side of the holes24so as to co-operate in fluid-tight manner with the closure sleeve26when said sleeve is in its closed state, as shown inFIGS. 1 and 3. More precisely, sealing means30are mounted on the tubing16above the holes24, and sealing means32are mounted on the tubing16below the holes24.

As shown, the sealing means30and32are placed in annular grooves formed in the outside surface of the tubing16so as to co-operate in fluid- tight manner with the cylindrical inside surface of the closure sleeve26.

The sealing means30and32are usually constituted by dynamic sealing gaskets that are annular in shape and that are made of a flexible material such as an elastomer.

In addition, below the closure sleeve26and in alignment therewith, the flow rate control device18includes a protective sleeve34. Essentially, the function of the protective sleeve34is to provide continuity in covering the sealing means32when the closure sleeve26moves upwards, i.e. when the drive means28are actuated in the opening direction of the flow rate control device18.

Finally, the flow rate control device18also includes return means36designed and organized in a manner such as to bring the protective sleeve34automatically into a position in which it covers the sealing means32when said sealing means do not co-operate with the closure sleeve26.

The bottom portion of the flow rate control device18is described in more detail below with reference toFIGS. 2 and 3.

In its portion situated below the sealing means32, the production tubing16has a portion16aof relatively small diameter, defined at the top by a first shoulder38and at the bottom by a second shoulder40. As shown inFIGS. 2 and 3, the second shoulder40may in particular be implemented in the form of the top face of another segment of the production tubing16or by some other separate part screwed to the bottom end of the portion16aof relatively small diameter.

The protective sleeve34includes a top portion24of relatively large diameter, and a bottom portion34bof relatively small diameter. The top portion34ais organized to slide snugly on that portion of the production tubing16which carries the sealing means32, while the bottom portion34bis received with clearance around the portion16aof relatively small diameter of the tubing16. The top portion34aand the bottom portion34bof the protective sleeve34are separated from each other internally by a shoulder42suitable for coming into abutment against the first shoulder38which thus forms an abutment surface on the production tubing16.

As shown inFIGS. 2 and 3, the return means36comprise resilient means constituted by a compression spring. This compression spring is disposed around the portion16of relatively small diameter of the production tubing16. Its top end is in abutment against the bottom face of the protective sleeve34, and its bottom end is in abutment against the second shoulder40formed on the tubing16.

By means of this configuration, when the closure sleeve26takes up a fully open or partially open position, as shown inFIG. 2, the return means36hold the protective sleeve34in abutment against the abutment surface formed by the first shoulder38. Under these conditions, the top portion34of relatively large diameter of the protective sleeve34covers the sealing means32snugly over their entire height. More precisely, the top end of the protective sleeve34is then flush with the bottoms of the holes24provided in the production tubing16. Thus, the sealing means32are substantially not in contact with the fluid in the well, and they are maintained in a compressed state.

As also shown inFIGS. 2 and 3, the compression spring constituting the return means36is advantageously protected from the fluid in the well by a cover44. This cover44is tubular in overall shape, and it is provided with a bottom flange44interposed between the second shoulder40and the bottom end of the compression spring. The cover44is thus prevented from moving relative to the production tubing16.

The cover44is mounted on the bottom portion34bof the protective sleeve34in a manner such that it co-operates therewith and with the compression spring36to form an assembly suitable for being mounted as a single unit on the production tubing16.

As shown inFIGS. 2 and 3, the top portion44bof the protective cover44is beveled and reinforced so as to form a scraper flush with the outside surface of the bottom portion34bof the protective sleeve34. The scraper formed in this way makes it possible to clean the surface when the protective sleeve34moves downwards against the return means36.

In the flow rate control device18formed in this way, the closure sleeve26has no holes. The through section of the device, which section enables the flow rate to be controlled, is defined between the bottom or front edge46of the closure sleeve26and the holes24provided in the production tubing16. More precisely, the further the front edge46moves upwards, the greater the through section of the device, and vice versa.

So long as the front edge46of the closure sleeve26remains in a partially open or fully open position as shown inFIG. 2, the protective sleeve34remains in abutment against the abutment surface formed by the shoulder38.

When the closure sleeve26moves downwards to close the flow rate control device18, the front edge46of the sleeve comes into abutment against the top or rear edge48of the protective sleeve34, so as to push said protective sleeve progressively downwards against the return means36(FIG.3). During this movement, the plane edges46and48are in abutment against each other over their entire circumference so that the sealing means32are constantly covered either by the protective sleeve34, or in part by the protective sleeve34and in part by the closure sleeve26while said closure sleeve is descending, or else entirely by the closure sleeve26when the device is in the closed position, as shown in FIG.3.

The present invention provides a wave seal device adapted to provide additional protection of the sealing means32during high equalization pressures. Because the interface between the closure sleeve26and the protective sleeve34is typically a flat plane that the sealing means32is aligned with, in some instances high equalization pressures (external to internal or internal to external) acting on the sealing means32can cause the sealing means32to extrude between the interface.

To combat such seal extrusion, one embodiment of the wave seal of the present invention, illustrated inFIG. 4, provides a wavy interface between the closure sleeve26and the protective sleeve34. As shown, the front edge46of the closure sleeve26and the top edge48of the protective sleeve34are formed with mating wavy surfaces. Accordingly, total alignment of the sealing means32with the interface between the sleeves26,34is prevented. The wavy interface provides support for and contains the sealing means32even when larger gaps exist between the front edge46of the closure sleeve26and the top edge48of the protective sleeve34during equalization.

It should be understood that the wavy interface illustrated inFIG. 4is exemplary and not intended to limit the scope of the wave seal of the present invention. There are a number of geometries and configurations that can be used to prevent total alignment of the sealing means32and the interface between the sleeves26,34.

Another embodiment of the wave seal of the present invention, illustrated inFIG. 5, provides a wavy sealing means32aadapted to prevent seal extrusion. The wavy sealing means32aprevents total alignment of the sealing means32awith the interface between the closure sleeve26and the protective sleeve34. Accordingly, when subjected to high equalization pressures, the sealing means32ais prevented from extruding between the interface of the sleeves26,34. The extrusion is prevented even when the interface between the sleeves26,34is a flat plane. Further, the extrusion is prevented even when larger gaps exist between the front edge46of the closure sleeve26and the top edge48of the protective sleeve34during equalization.

It should be understood that the wavy sealing means32ashown inFIG. 5is exemplary and not intended to limit the scope of the present invention. There are a number of geometries and configurations that can be used to prevent the sealing means32afrom total alignment with the interface between the sleeves26,34.

Naturally, the invention is not limited to the embodiments described above by way of example. The wave seal of the present invention can be used for any number of downhole devices requiring the dynamic sealing of pressure ports.