EP0457879B1 - Device and method for cleaning an underground well - Google Patents

Abstract

PCT No. PCT/FR90/00895 Sec. 371 Date Sep. 26, 1991 Sec. 102(e) Date Sep. 26, 1991 PCT Filed Dec. 10, 1990 PCT Pub. No. WO91/09205 PCT Pub. Date Jun. 27, 1991.Method has been provided for cleaning a vertical, deviated or horizontal underground well. In which a maintenance tubing having a cleaning head at its end is lowered into a production pipe for suction of sediments. At a certain level above the region of the well to be cleaned, a hydraulic isolation device is installed in the annulus between the maintenance tubing and the production pipe. Fluid is injected into the annulus to activate the hydroejector which is located above the hydraulic isolation device to cause the suction of the sediments. The sediments downhole therefore can be cleaned out without introducing foreign fluid downhole.

Description

The present invention relates to a method for cleaning an underground well and to a device for implementing such a method.

In the presence of downhole deposits, in particular sandy sediments of unconsolidated formations, a first method consists in reconditioning by means of a drilling device the production conduit at the level of the layer. The application of this method is very expensive because it is necessary to dismantle the equipment in place and after cleaning carry out a new completion. To avoid recourse to such heavy "repair" operations, there are various means of concentric maintenance of the well bottoms.

Known in particular, according to United States patent No. 4,671,359, a cleaning system for extracting sediment from a lost column (with gravel or not), which system requires a rigid tubular extension lowered to the cable and anchored in a suitable receptacle at the bottom of the production column. Through this extension is lowered a flexible and continuous tube called "coiled tubing" equipped at its end with nozzles for distributing a cleaning fluid coming from the surface and the flow of which is directed towards the wall of the bottom of the well. The sediments are entrained in the fluid current pumped to the surface through the flexible tube, more precisely the sediments rise to the surface by the annular between the "coiled tubing" and the production column.

According to such a system, by adding this tubular extension to the production column and by using the technique of the flexible and continuous tube known as "coiled tubing", the speed of the fluid is increased and the evacuation of the sediments by the annular is thus improved. between the "coiled tubing" and the said extension.

However, this system has drawbacks.

A first drawback lies in the fact that the circulation of the cleaning fluid exerts a back pressure on the often brittle and very sensitive layer (loss, emulsion, precipitate, etc.).

A second drawback lies in the fact that the method requires a cable operation beforehand, the limitations in length, load and deviation of which are known.

A third drawback relates to training in a sub-hydrostatic or depleted regime: the system by the back pressure that it develops requires the use of fluids produced with low specific weight and compatible with the training; this can become prohibitive.

The significant development of deflected, highly deflected wells and horizontal drains poses many new cleaning problems by the very fact that the direction and speed of the flow of fluid for discharging solid matter by known and conventional methods and devices does not can oppose the forces which tend to disintegrate the layer.

Thus, there is also known from US Pat. No. 4,744,420 a device for removing solid accumulations, such as sandy aggregates or the like, in strongly deviated or horizontal underground wells. This device comprises a train of concentric tubes intended to be introduced into the well: one for the supply of the working fluid to the bottom of the well and the other for the return of the fluid charged with the sediments. The device also includes at the end of the train a hydro-ejector which projects part of the working fluid onto the sediment before aspirating it.

In addition to the drawbacks already mentioned, the train of tubes is injected into the well after dismantling the existing completion. In addition, the device cannot operate continuously over a large range of sediment accumulation without heavy intervention, such as the addition of additional concentric tubes.

The implementation of this process disturbs the completion, which is a major drawback.

To overcome these drawbacks, the present invention provides a cleaning method according to claim 1.

According to this method, there is therefore a suction of the sediments, this suction thus avoiding all the drawbacks due to the pressure exerted on the layer by the return fluid loaded with sediments.

In addition, the hydraulic separation isolating the bottom of the well, the working fluid does not have to be compatible.

According to a preferred embodiment of the invention, said hydraulic separation is carried out by means of a cable gland mounted, with the possibility of sliding in the cleaning position of the device, on the maintenance tube, which cable gland cooperates with a polished connection (in English: "landing nipple") of the production column to achieve a watertight and sliding separation.

Such an arrangement constitutes a considerable advantage over the prior art since the implementation of the method according to the invention does not disturb the existing completion. Indeed, it is necessary and sufficient that the existing completion includes a polished connection to the base of the production column for the location of the hydraulic separation.

According to an also preferred embodiment of the invention, the maintenance tube is a so-called "coiled tubing" tube with a diameter less than or equal to 38 mm. The "coiled tubing" is flexible and by this means the process applies equally to vertical wells, deviated wells, strongly deviated wells, or horizontal drains. The "coiled tubing" is remarkable in that it comes into perfect contact with the low generatrix of the highly deviated or horizontal drain.

Preferably, the cable gland includes a set of seals on its internal diameter to allow leaktight sliding of the maintenance tube on said cable gland.

The cable gland is shaped to be immobilized in abutment against a shoulder of the polished fitting, and also includes external seals applying to the internal surface of said polished fitting. It is the overpressure in operation that keeps it in this position.

The cleaning is then done, in one or more progressive passes, by moving the cleaning head in the part of the well to be cleaned by sliding the maintenance tube through the hydraulic separation, that is to say by sliding the tube to through the cable gland.

The cleaning device includes a cleaning device cleaning for carrying out the method of claim 1 comprising a maintenance tube and means for descending inside a production column said maintenance tube, said maintenance tube comprising a cleaning head (7), suitable for the suction of sediment to be extracted, mounted at the end of a tubular extension (5), a cable gland (6) mounted with the possibility of sliding on said tubular extension (5) above said cleaning head (7), a hydro-ejector (3) mounted at the other end of said tubular extension (5), the outlet of the hydro-ejector being connected to the surface by a tube (1) called coiled tubing, said cable gland ( 6) being able to form with a polished connection (12) a hydraulic separation of the directory comprised between the maintenance tube and the production column which isolates the directory under pressure from the bottom of a well, the cleaning device comprising in addition to the means for injec ter in said annular a working fluid for the operation of said hydro-ejector.

The cleaning head has an outer diameter less than the internal passage diameter of the polished fitting while the cable gland has an outside diameter greater than the internal passage diameter of the polished fitting, so as to come to a stop in translation on said polished fitting .

During introduction into the well, the cable gland is temporarily immobilized in translation on the cleaning head by means of a pin or any other equivalent means, the rupture of which can be caused by hydraulic overpressure or mechanical support to the 'arrival in the polished fitting.

The cleaning head has an ejectable plug for closing the external fluid inlet to the maintenance tube, the ejection of the plug being caused by an overpressure in the maintenance tube.

The use of a well-known and widely used intervention technique such as the so-called "coiled tubing" technique is an important advantage. The present invention does not relate to this technique per se, which is known to require surface devices, known per se, such as a well shutter block (BOP), an airlock, a coiled tubing storage reel ", an injector and pumping means, all not described in detail and not shown in the context of the present patent application.

• on insère l'extension - avec la tête de nettoyage montée à l'extrémité - sous la garniture d'étanchéité ou "stripper" du "coiled tubing", le presse-étoupe étant solidaire de la tête de nettoyage,
• on suspend l'extension dans le bloc obturateur de puits, et on ferme les mâchoires autour du tube,
• on ouvre le sas,
• on coupe ledit "coiled tubing",
• on insère l'hydroéjecteur au moyen de raccords rapides,
• on ferme le sas,
• on ouvre les mâchoires du bloc obturateur de puits,
• on poursuit la descente du "coiled tubing" jusqu'à l'engagement du presse-étoupe dans le raccord poli solidaire de la colonne de production, avec cisaillement de la goupille de maintien,
• on éjecte le bouchon dans la tête par une surpression dans le tube de maintenance,
• on injecte le fluide moteur dans l'espace annulaire entre la colonne de production et le "coiled tubing" (au-dessus donc de la séparation hydraulique) pour la mise en marche de l'hydroéjecteur,
• on poursuit la descente progressive de la tête de nettoyage en observant le retour de sédiments en surface,

   D'autres avantages et caractéristiques de la présente invention apparaîtront dans la description qui va suivre d'un exemple de réalisation non limitatif de l'objet de l'invention, accompagné du dessin dans lequel :

• la figure 1 représente le dispositif de nettoyage d'un fond de puits à la descente dans le puits,
• la figure 2 représente le même dispositif en position de nettoyage dans le puits,
• la figure 3 représente le presse-étoupe du dispositif des figures 1 et 2,
• la figure 4 représente un exemple de réalisation de la tête de nettoyage, avec son bouchon éjectable,
• la figure 4a représente un exemple de réalisation de la face extérieure de cette tête de nettoyage pouvant être mise en rotation par le fluide aspiré,
• la figure 5 représente un exemple de réalisation du connecteur à obturation utilisé pour le retrait de l'hydroéjecteur après opération de nettoyage.

A cleaning method is also proposed, comprising the complete lowering of the maintenance tube, according to which:

• the extension is inserted - with the cleaning head mounted at the end - under the seal or "stripper" of the "coiled tubing", the cable gland being integral with the cleaning head,
• we suspend the extension in the well shutter block, and close the jaws around the tube,
• we open the airlock,
• we cut said "coiled tubing",
• the hydro ejector is inserted by means of quick couplings,
• we close the airlock,
• we open the jaws of the well shutter block,
• the “coiled tubing” is lowered until the gland is engaged in the polished connection integral with the production column, with shearing of the retaining pin,
• the plug is ejected in the head by an overpressure in the maintenance tube,
• the working fluid is injected into the annular space between the production column and the "coiled tubing" (above therefore the hydraulic separation) to start the hydro-ejector,
• the gradual descent of the cleaning head is continued by observing the return of sediments to the surface,

Other advantages and characteristics of the present invention will appear in the following description of a non-limiting exemplary embodiment of the subject of the invention, accompanied by the drawing in which:

• FIG. 1 represents the device for cleaning a bottom of a well when going down into the well,
• FIG. 2 represents the same device in the cleaning position in the well,
• FIG. 3 represents the cable gland of the device of FIGS. 1 and 2,
• FIG. 4 represents an exemplary embodiment of the cleaning head, with its ejectable plug,
• FIG. 4a represents an exemplary embodiment of the external face of this cleaning head which can be rotated by the aspirated fluid,
• FIG. 5 represents an exemplary embodiment of the plug connector used for removing the hydro-ejector after cleaning operation.

In the drawing in FIG. 1, the reference 1 represents a continuous tube of relatively small diameter, less than or equal to 38 mm (1 "1/2). This tube is that of a tool used for intervention operations under pressure in production wells, known as the "coiled tubing" technique, a technique in which a flexible and continuous tube stored on a drum is injected into a pressure well. This technique adapts to any head configuration well and offers a rapid maneuver. The injection system with the well shutter block and the airlock in particular, as well as the "coiled tubing" storage system, the means fluid injection and surface pumping are not shown.

At the end of the coiled tubing tube 1 is mounted, via a 38 mm (1 "1/2) connection 2, a Venturi effect pump or hydro-ejector 3 operating in reverse pumping. valve 3a integrated in the Venturi prevents any return of liquid to the space surrounding the pump, as will be explained below.

Via a sealing connection, referenced 4, with a diameter of 38 mm (1 "1/2), the pump 3 is connected to a tubular extension 5 whose diameter is equal to that of the tube 1 and whose length is adjustable according to the dimensional characteristics of the well to be cleaned This length is at least equal to the distance between the level of hydraulic separation chosen (L in the drawing of FIG. 2) and the most distant part of the well to be cleaned.

A cable gland 6 is mounted with the possibility of sliding along the tubular extension 5. It is shown in more detail in the drawing of Figure 3. it has on its inner bore 6a a set of O-rings and lip 6b and on its outer bore 6c a set of compressible resilient lip seals 6d, the seals 6b sealing the tubular extension 5 while the outer seals 6d cooperate with an element of the production column (the polished connector or "landing nipple ") to perform the hydraulic separation as will be seen later.

In the lowering position shown in the drawing of Figure 1, the cable gland 6 is immobilized in translation on the upper part of a cleaning head 7 by a pin 8 (see Figure 3), which can be sheared under the conditions explained below to allow the maintenance tube to slide into the internal bore of the cable gland 6.

The end of the extension 5 is temporarily closed by an ejectable plug 7a (see FIG. 4) which has the function in the closed position of allowing the mounting of the pump 3 on the surface.

The cleaning head 7, which extends the tubular extension 5, is designed to facilitate cleaning by turbulence and induced rotation.

The cleaning head 7 and its mounting at the end of the tubular extension 5 are shown in the drawing in FIG. 4. The ejectable plug 7a is immobilized in the closed position by means of the pin 13. The head is rotatably mounted on a ball bearing bearing 14. A conventional gripping connector 18 comprising the parts 15, 16, 17 allows the attachment of the head 7 to the extension 5.

The head is pierced with oblong grooves 19 pierced in non-radial directions, but oriented helically or almost helically, so as to impart, under the effect of the through fluids, a rotational movement to the cleaning head 7 (FIG. 4a) .

It can also be provided on the outer surface of the turbulence fins 20 (FIG. 4a).

In the drawing of FIG. 2, the reference 9 schematically represents the casing of the well, which can be a vertical well, deviated, or even strongly deviated and even a horizontal drain. The production column is referenced 10. The annular space between the production column 10 and the casing 9 is closed by a seal or packer 11. The cleaning assembly or maintenance tube of FIG. 1 is introduced in the production column 10, which comprises a polished downhole connection 12 forming, by its shoulder 12a, seat for the cable gland 6. In the example presently described, the production column 10 is of any diameter.

The cleaning system works as follows:
The "coiled tubing" wound on the surface on a reel, is inserted without disturbing the pressure prevailing at the top of the well in a seal and operating (stripper), not shown, with the addition of a lubricating grease, with the cleaning head 7 at its free end. Above the cleaning head is inserted the cable gland 6, immobilized in translation with the cleaning head 7 by the pin 8 (Figure 3). The length of "coiled tubing" inserted in this way in the "stripper" depends on the distance between the most distant part of the well to be cleaned and the location (L) of the polished fitting 12 forming the sliding bearing of the maintenance and separation tube hydraulic. The length of the tubular extension 5 is equal to or greater than the distance indicated above.

The "coiled tubing" is suspended in the jaws of a well shutter block (B.O.P) and the airlock is opened. These conventional materials of the "coiled tubing" technique are not shown in the drawing, and are not described in detail.

The "coiled tubing" tube is cut at the surface, security being obtained by the position of the ejectable plug 7a in the cleaning head 7 which prevents any rise of fluid by the "coiled tubing" tube constituting the maintenance tube.

In a manner known per se, the hydro-ejector 3 is inserted by means of a plugging connector 4 shown in the drawing in FIG. 5. This connector 4 comprises a quarter-turn valve 4a, housed in a bore 4b and can be oriented by an axis 4c. This type of connector also includes a plurality of seals 4d and an outer surface of curvilinear profile in the recesses from which the tubular parts of the elements to be connected are forcibly crushed (FIG. 5).

The airlock is reconnected, the jaws of the well shutter block are open and the descent of the "coiled tubing", assembled to the hydro-ejector 3 by means of the connector 2 also 38mm (1 "1/2), is continued so as to form the tubular part referenced 1 in the drawing of FIGS. 1 and 2.

When the cable gland 6 reaches the localization level L of hydraulic separation, therefore engages in the polished fitting 12 at the bottom of the well, the pumping of the driving liquid in the annular space comprised between the production column 10 and the tube of maintenance 1,2,3,4,5,6 and 7 can start; the pressure of the engine liquid makes it possible to immobilize in translation and in perfect abutment the cable gland 6 on the seat 12a of the polished connector 12. The hydraulic separation is carried out, the part of the production column located below the hydraulic separation ( referenced LB) and, therefore, also the bottom of the well are isolated from the volume of annular overpressure (LH) located above the hydraulic separation.

This hydraulic separation constitutes an important characteristic of the present invention. Indeed, this separation makes it possible to set in motion and evacuate the sediments without overpressure on the layer, without contact of working fluid with the wall of the well. The cleaning operations take place with isolation of the part of the well to be cleaned thanks to the hydraulic separation carried out by immobilizing the cable gland 6 on the polished connection 12 at the location level L.

It will also be noted that, like the implementation of the process itself, the realization of this separation does not require the addition of new materials or the modification of existing materials in the completion.

By an overpressure in the maintenance tube, the ejectable plug 7a is ejected (shearing of the pin 13 or any other means known per se) and falls to the bottom of the cleaning head 7, the bottom of the well is then connected to the surface (see figure 4).

The working fluid pumped from the surface starts the suction of the hydro-ejector 3 through the cleaning head 7 and the tubular extension 5.

An additional descent of the "coiled tubing" then shears the pin 8 for holding the cable gland 6 on the cleaning head 7. The "coiled tubing" can then be gradually pushed so that the cleaning head 7 is brought to proximity of the parts of the well to be cleaned, by sliding the extension tube 5 in the internal bore 6a of the cable gland 6.

The sediments are sucked in through the orifices 19 of the cleaning head, rise up through the extension tube 5, the connector 4, the hydro-ejector 3 and the tube 1 towards the surface.

The cleaning head 7 can be a rotary head with a cyclone effect by the conformation of the orifices along helical lines, as already mentioned.

Several passes are possible while maintaining the overpressure on the cable gland 6 on the seat 12a of the polished fitting 12.

At the end of cleaning, the working fluid is replaced by a fluid which does not pollute the tank and which may or may not stabilize the well. If this fluid is gas, the well generates overhead pressure. In this case the maintenance tube is closed internally when arriving at the surface by a shutter 4a housed in the connector 4 placed under the hydro-ejector 3, which allows the withdrawal of the hydro-ejector and the joining of the "coiled tubing" to continue the extraction thereof under contained pressure.

Finally, there is an additional advantage of the method according to the invention: any leak in the packing gland does not condemn the cleaning method, it simply results in a reduction in energy efficiency compensated by an increase in the flow of engine liquid .

Claims (11)

1. Method for cleaning a vertical, sloping or horizontal underground shaft, provided with a production column, during which there is lowered into the interior of the said column (10) a maintenance tube (1 to 7) comprising, at its end, a cleaning head (7), for the aspiration of the sediments to be extracted, a hydraulic separation of the annular space between the maintenance tube (1 to 7) and the production column (10) is produced in a given vicinity (L) below the part of the shaft to be cleaned, and there is injected into the said annular space a driving fluid for the operation of a hydroejector, which hydroejector (3) induces the aspiration, by the maintenance tube (1 to 7), of the sediments to be extracted, the hydraulic separation isolating the annular space under excess pressure (LH) from the base of the shaft under vacuum, characterised in that the cleaning head (7) is displaced in the part of the shaft to be cleaned by sliding the maintenance tube (1 to 7) across the hydraulic separation.
2. Method for cleaning an underground shaft according to Claim 1, characterised in that the said hydraulic separation is performed by means of a packing box (6) mounted such that it can slide on a tubular part or an extension (5) of the maintenance tube (1 to 7) which, in the vicinity of a hydraulic separation, cooperates, by correspondence of the shapes and in a leaktight manner, with a polished connection (12) of the production column (10).
3. Method for cleaning an underground shaft according to Claim 1, characterised in that the maintenance tube is constructed from a tube called coiled tubing, the diameter of which is less than or equal to 38 mm.
4. Method for cleaning an underground shaft according to Claim 3, characterised in that the said packing box (6) is shaped to be immobilised in translation in abutment against the polished connection (12), and comprises leaktight exterior joints (6d) which are pressed against the internal surface of said polished connection (12) in such a manner as to produce a leaktight hydraulic separation.
5. Cleaning device for performing the method of Claim 1, comprising a maintenance tube and means for lowering the said maintenance tube into the interior of a production column, the said maintenance tube comprising a cleaning head (7), suitable for the aspiration of sediments to be extracted, mounted at the end of a tubular extension (5), a packing chamber (6) mounted such that it is possible for it to slide on the said tubular extension (5) above the cleaning head (7), the hydro-ejector (3) mounted at the other end of the said tubular extension (5), the outlet of the hydro-ejector being connected to the surface by a tube (1) called coiled tubing, the said packing chamber (6) being suitable for forming, together with a polished connection (12), a hydraulic separation of the annular space between the maintenance tube and the production column, which isolates the annular space under excess pressure from the base of a shaft, the cleaning device furthermore comprising means for injecting, into said annular space, a driving fluid for the operation of the said hydro-ejector.
6. Device according to Claim 5, characterised in that the cleaning head (7) has an exterior diameter that is less than the diameter of the internal passage of the polished connection (12).
7. Device according to Claim 5, characterised in that the packing chamber (6) has an exterior diameter which is greater than the diameter of the internal passage of the polished connection (12), in such a manner as to abut on the polished connection (12).
8. Device according to Claim 5, characterised in that the packing chamber (6) is provisionally immobilised in translation on the said tubular extension (5) by means of a pin (18), the breakage of which is induced by a hydraulic excess pressure on the upper surface of the said packing chamber.
9. Device according to Claim 5, characterised in that the hydro-ejector (3) has a reduced external diameter of between 50 and 63 mm, and comprises an integral flap (3a) to prevent any return of the liquid towards the annular space between the production column (10) and the maintenance tube (1 to 7).
10. Device according to Claim 5, characterised in that the said cleaning head (7) comprises an ejectable plug (7a), closing the inlet of the fluid towards the maintenance tube (1 to 7), the ejection of the plug (7a) being caused by excess pressure on the said maintenance tube.
11. Device according to Claim 5, characterised in that the said cleaning head (7) is a rotatable head with a cyclone effect.

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