EP0469140B1 - Device for protecting wells from corrosion or deposits caused by the nature of the fluid produced or located therein - Google Patents

Abstract

PCT No. PCT/FR91/00148 Sec. 371 Date Oct. 22, 1991 Sec. 102(e) Date Oct. 22, 1991 PCT Filed Feb. 22, 1991 PCT Pub. No. WO91/13234 PCT Pub. Date Sep. 5, 1991.Device for protecting wells from the risks of corrosion and deposits due to the nature of the fluid produced or present in the well. It is formed of a steel support casing (2), associated with a composite material production string (3), with a free annular space (6) particularly for the injection of inhibiting agents without stopping working. The string (3) is laid on the casing (2) via a device (4) which may be lowered at the same time as the string (3) and which has openings (13) ensuring the hydraulic continuity of the annular space (6). The device is particularly well adapted to wells conveying fluids which are aggressive with respect to traditional steel casings.

Description

The present invention relates to a new concept of well completion using steel support casing associated with a production or injection column made of composite materials, with free annular.

The invention is particularly applicable to the production of geothermal wells to combat the effects of corrosive and encrusting thermochemistry of the geothermal fluid and to preserve the longevity of the works. These problems are particularly well known, for example, in the Paris basin where many geothermal "doublets" (an assembly formed by a production well used to capture the hot water from the reservoir and an injection well used to reinject the fluid in the tank after extraction of calories) have been carried out since the 1970s.

In these installations, the geothermal fluid-hot water whose temperature is between 50 ° C and 85 ° C and with high salinity (15 to 25 g / 1) - comprises a dissolved gaseous phase enriched in CO2 and H2S which give it a slight acidity (pH 6 to 6.4). This aggressiveness is reflected in certain areas of the reservoir captured by repeated and accelerated damage to the structures under the effect of corrosion and deposit affecting the casings and clogging affecting the overflow (reservoir capture area).

• corrosion du tubage du puits producteur et, à un degré moindre, de l'ouvrage d'injection ;
• dissolution du fer du tubage et mise en solution avec formation de sulfures de fer ;
• dépôts des sulfures sur les parois de l'acier du tubage producteur sans protection de celui-ci (poursuite de la cinétique de corrosion sous dépôts) ;
• entraînement sous forme particulaire (suspensions solides) dans l'eau produite et encrassement des échangeurs de chaleur, dépôts/incrustations du tubage injecteur et accumulation au fond et sur les parois du découvert ;
• accroissement des pertes de charge, réductrice du débit de circulation de la boucle géothermale et colmatage des ouvrages et équipements de surface.

The damage mechanism can be summarized as follows:

• corrosion of the casing of the producing well and, to a lesser degree, of the injection structure;
• dissolving the iron in the casing and dissolving it with the formation of iron sulphides;
• deposits of sulphides on the walls of the steel of the producing casing without protection of the latter (continuation of the kinetics of corrosion under deposits);
• entrainment in particulate form (solid suspensions) in the produced water and fouling of the heat exchangers, deposits / encrustations of the injector casing and accumulation at the bottom and on the walls of the overdraft;
• increase in pressure losses, reducing the circulation flow of the geothermal loop and clogging of works and surface equipment.

• . moyens curatifs ; les puits sont libérés de leurs dépôts par descente en rotation et circulation de boue, d'une garniture conventionnelle au câble et aux tiges bien connues des spécialistes ; des produits spécifiques permettant de diminuer les coûts de ces interventions ont été réalisés ; le brevet français 2 631 708 décrit un de ces dispositifs basé sur un système de tube continu bobiné (dit "coiled tubing") ;
• . moyens préventifs chimiques basés sur l'injection en fond du puits d'agents inhibiteurs de corrosion/dépôt à fonctions respectivement filmante (corrosion) et dispersante (dépôts). Cette injection est réalisée au moyen d'un tube auxiliaire d'injection (TAI), dont la mise en place et la tenue dans le temps sont elles aussi sujettes à caution ; les brevets français 2 463 197 et 2 502 239 décrivent respectivement un procédé inhibiteur par injection d'amines aliphatiques et d'un dispositif d'injection en fond de puits ;
• . solutions alternatives pour les matériaux ; celles-ci reposent sur l'utilisation de matériaux soit résistants, soit, de préférence, électrochimiquement inertes vis-à-vis de la corrosion dans le système H2O-CO2-H2S. Le choix d'alliages nobles (Cr, MO, Ni, etc...), d'un coût élevé, présente par ailleurs l'inconvénient d'une fragilisation de la structure solide en présence d'H2S dissous, à faible concentration, inexistante avec les aciers au carbone habituellement utilisés. Les matériaux composites sont passifs au plan de la corrosion ; leur mise en place dans un forge, cependant, n'est pas sans risque en raison des caractéristiques mécaniques du matériau utilisé. Pour la même raison, ce risque d'endommagement existe lors des interventions, en cours d'exploitation. La simple friction d'un câble, utilisé pour descendre des outils de diagraphies électriques, peut ponctuellement créer un trou dans l'épaisseur du tubage.

The curative and preventive means making it possible to reduce, failing to eradicate, these damages are of three types:

• . curative means ; the wells are released from their deposits by rotary descent and circulation of mud, from a conventional lining to the cable and to the rods well known to specialists; specific products enabling the costs of these interventions to be reduced have been produced; French Patent 2,631,708 describes one of these devices based on a coiled tubing system (known as "coiled tubing");
• . chemical preventive means based on the injection at the bottom of the well of corrosion / deposit inhibiting agents with film-forming (corrosion) and dispersing (deposits) functions respectively. This injection is carried out by means of an auxiliary injection tube (TAI), the installation and holding over time of which are also subject to caution; French patents 2,463,197 and 2,502,239 respectively describe an inhibitory process by injection of aliphatic amines and of an injection device at the bottom of the well;
• . alternative solutions for materials ; these are based on the use of materials which are either resistant or, preferably, electrochemically inert with respect to corrosion in the H2O-CO2-H2S system. The choice of noble alloys (Cr, MO, Ni, etc.), of a high cost, also has the drawback of embrittlement of the solid structure in the presence of dissolved H2S, at low concentration, nonexistent with the carbon steels usually used. Composite materials are passive in terms of corrosion; their installation in a forge, however, is not without risk due to the mechanical characteristics of the material used. For the same reason, this risk of damage exists during interventions, during operation. The simple friction of a cable, used to descend electrical logging tools, can punctually create a hole in the thickness of the casing.

This observation highlights the fact that the conventional solutions used to prevent problems of damaging wells due to the aggressiveness of the geothermal fluid, involve in their implementation significant risks.
A well completion device has been described by US Pat. No. 4,057,108 (Broussard). In this device, the annular space is pressurized, in order to confine the reservoir fluid in the casing or production column and the lower parts resistant to corrosion. The injection of products such as corrosion inhibitors can only be carried out beyond the suspension device. US Patent 4,615,387 (Johnson and Bednar) describes a well completion device in which intermediate packers allow an inhibition product to pass. However, a downhole device prevents any equipping of the assembly.

• la figure 1 représente un exemple de complétion de puits de production géothermique selon l'invention,
• les figures 2, 3 et 4 mettent en évidence certains risques inhérents aux solutions classiques et évités dans la solution objet de l'invention ;
• la figure 5 représente une variante possible de réalisation de l'invention ;
• la figure 6 représente un détail de l'invention.

The invention which is the subject of the present application constitutes another alternative combining the possibilities of chemical preventive means and material alternatives without having the disadvantages.
Understanding the invention and its advantages will be facilitated by the description of an exemplary embodiment illustrated by the attached figures below:

• FIG. 1 represents an example of completion of geothermal production wells according to the invention,
• Figures 2, 3 and 4 highlight certain risks inherent in conventional solutions and avoided in the object of the invention solution;
• FIG. 5 represents a possible variant embodiment of the invention;
• Figure 6 shows a detail of the invention.

In FIG. 1, the formations up to the roof of the reservoir 1 to be captured are drilled in large diameters. A casing traditional support structure 2 is laid and cemented 8 before drilling the reservoir.

After drilling the reservoir, a production column 3 of composite materials is put in place. To allow the possible installation of a submerged pump, the upper part of the production column 3 is of large diameter, thus constituting a pumping chamber. To avoid "trapping" of the production column between two fixed points, a drawback inherent in conventional laying systems, this is put in place by means of a particular device 4 put in place at the same time as the descent from column 3. The lower part of the column hangs from it, which also serves as a seat for the upper part. The expansions of the latter are caught at the head via a cuff 5. The other end of the lower part slides freely along its axis in the support casing 2. The entire column 3 is centered by the centralizers 7 made of composite material .

The invention thus aims to provide an annular space 6, between the cemented steel casing 2 and the column of composite materials 3, this annular space 6 being free and reduced.

• tubage acier diamètre 18"5/8   e = 30 mm
• tubage acier diamètre 13"3/8   e = 7,1 mm
• tubage acier diamètre 10"3/4   e = 13,3 mm
• tubage acier diamètre 9" 5/8   e = 20,1 mm

Thus, in the case of steel and composite tubing of standard diameters, corresponding to current manufacturers' productions, the thickness e of the annular space 6 is equal to:

• steel tubing diameter 18 "5/8 e = 30 mm
• steel tubing diameter 13 "3/8 e = 7.1 mm
• steel tubing diameter 10 "3/4 e = 13.3 mm
• steel tubing diameter 9 "5/8 e = 20.1 mm

These values can be compared with the completion values commonly practiced in the field of petroleum exploitation in which for conventional diameters, casing with a diameter of 9 "5/8 and 7", the thickness values are respectively 42 and 66 mm.

• . la partie inférieure de la colonne en matériaux composites 3 est descendue dans le puits non éruptif par gravité, au moyen d'équipements tels qu'élévateurs, clés hydrauliques dynamométriques, treuils et de procédures utilisés de manière classiques dans le domaine de l'exploitation pétrolière pour la pose des tubages.
• . il est ensuite procédé à la fixation par vissage du dispositif siège/réceptacle 4, du raccord d'accrochage et de la réduction de diamètre situés au dessus du dispositif 4, puis un vissage du premier élément de la partie supérieure, en gros diamètre, de la colonne de matériaux composites.

The installation of the column of composite materials 3 can advantageously be illustrated in the following manner:

• . the lower part of the composite material column 3 is lowered into the non-erupting well by gravity, using equipment such as elevators, dynamometric hydraulic keys, winches and procedures conventionally used in the field of petroleum exploitation for laying tubing.
• . it is then proceeded to the fixing by screwing of the seat / receptacle device 4, of the coupling and the reduction of diameter located above the device 4, then a screwing of the first element of the upper part, in large diameter, of the column of composite materials.

In the case where the relative fragility of the large diameter column may require it, the descent of the latter can be assisted by means of a string of rods and a suspension device designated in Anglo-Saxon terms by "liner hanger "attached to the first composite column element 3, in a housing provided for this purpose in a suitable connector. After the receptacle seat has been placed, and not hung as in the case of a packer, on the lower steel support tube, in telescoping with the pumping chamber, the wellhead is then assembled.

Furthermore, the receptacle 4 is designed so as to ensure hydraulic continuity in the annular space 6.

• . la mise en équipression de l'intérieur de la colonne de production et de l'annulaire, évitant la création d'efforts dommageables au composite 3 et offrant un meilleur amortissement des a-coups de pression et des coups de bélier en production ;
• . le contrôle de l'étanchéité, à la fois du tubage acier 2 et de la colonne composite 3 ;
• . l'injection à faible débit depuis la tête de puits en surface d'agents inhibiteurs, sans nécessiter de tube auxiliaire d'injection ; tout risque inhérent à la mise en place d'un tel dispositif (perte de débit, rupture, perte du tube, arrêt de l'exploitation) est ainsi évité ;
• . d'éviter les problèmes inhérents au packer de pied (pose, ancrage, tenue dans le temps).

The annular space 6 between the composite casing 3 and the retaining casing 2, left free, allows:

• . equipping the interior of the production column and the ring finger, avoiding the creation of damaging forces on composite 3 and offering better damping of pressure surges and water hammer in production;
• . tightness control, both of the steel casing 2 and of the composite column 3;
• . low-flow injection from the wellhead at the surface of inhibiting agents, without the need for an auxiliary injection tube; any risk inherent in the installation of such a device (loss of flow, rupture, loss of the tube, cessation of operation) is thus avoided;
• . to avoid the problems inherent in the packer of foot (installation, anchoring, held in time).

The injection of inhibitors at slight overpressure into the ring finger 6 avoids any contact (and thus any risk of corrosion) between the geothermal fluid and the retaining casing 2. Another important advantage, this injection can be done without stopping operation .

The conventional solutions of the prior art, shown in Figures 2, 3 and 4, require the installation of foot packers whose drawbacks are well known to specialists.

The solutions of Figures 2 and 3 include a sliding of the composite tubing 3 in the foot packer 9 via an anchor "skirt" 11; the sliding is external in the solution of FIG. 2 and internal in that of FIG. 3.

The tightness of the ring finger in the solutions shown in FIGS. 2 and 3 is ensured by the seals 10. This cannot be guaranteed in the long term. It then requires a special intervention (work-over) with all the hazards of this type of work in composite casing.

Likewise, often in the case of deviated wells, the bases for calculating the traction to be applied to the casing, to take account, before anchoring at the wellhead, of the elongations induced by thermal and mechanical expansion, are often subject to hazards: knowledge of the friction forces of composite tubing / steel tubing, nominal path and actual path of the casings.

The solution shown in Figure 4 is a simplification of the previous solutions with the same drawbacks; moreover, the composite tubing 3 is taken between two fixed points without the possibility of sliding in the skirt of the packer as in the solutions of FIGS. 2 and 3.

The invention which is the subject of the present application eliminates these drawbacks. The simplicity of design facilitates the installation of composite tubing. The absence of a fixed point at the base allows the relaxation of the stresses possibly introduced by local friction during the descent.

The composite materials in production column 3 can combine epoxy (resin), aliphatic amines (hardeners) and E-type glass fibers (reinforcement), double filament winding and axial reinforcement; in petroleum applications, the threaded joints will be of the sleeved type to API standards. Carbon and polyaramides may constitute material alternatives to glass with regard to the reinforcing fibers.
To avoid punctual wear of column 3 in the event of repeated descents of logging tools, it is possible to add anti-abrasion agents to the composite material constituting the casing.

The support tubes 2 can be conventional carbon steel tubes.

FIG. 5 represents a possible application for a geothermal well or a conventional petroleum application well that does not require a pumping chamber.

FIG. 6 gives the detail of the receptacle seat assembly 4.

• . le système de suspension 4 est maintenu en cours de descente de la colonne 3 entre un manchon supérieur 14 et un manchon inférieur 17 d'un tube court 18 de la colonne 3, positionné en fonction de la cote de la partie supérieure du tube de soutènement 2 et des longueurs respectives des parties haute et basse de la colonne 3 séparées par ce tube 18 ;
• . ce système 4 comprend en outre un siège 12 reposant sur la partie supérieure du tube de soutènement 2 muni d'ouvertures 13 assurant la continuité hydraulique de l'annulaire 6.
• . ce siège 12 supporte l'ensemble de la colonne 3 par l'intermédiaire du manchon supérieur 14 reposant sur une bride 15 et éventuellement d'une protection 16 pouvant être par exemple un matériau polymérique.

In a preferred embodiment of the suspension device 4, it is produced and implemented as follows:

• . the suspension system 4 is maintained during the descent of the column 3 between an upper sleeve 14 and a lower sleeve 17 of a short tube 18 of the column 3, positioned as a function of the dimension of the upper part the support tube 2 and the respective lengths of the upper and lower parts of the column 3 separated by this tube 18;
• . this system 4 also comprises a seat 12 resting on the upper part of the support tube 2 provided with openings 13 ensuring the hydraulic continuity of the ring finger 6.
• . this seat 12 supports the entire column 3 by means of the upper sleeve 14 resting on a flange 15 and possibly of a protection 16 which may for example be a polymeric material.

Claims (12)

1. A well completion device for the production and/or the injection of underground or geothermal fluid using a steel support casing (2) positioned and cemented according to the usual rules of the art associated with a production or injection string (3) or suspended casing of the fluid with a possible injection without stopping working at a low rate of corrosion inhibiting agents in the annular space between said casings (2) and (3), characterized by said casing or production or injection string (3) being solely and freely suspended and supported by an assembly (4), said assembly comprising, on the one hand, a seat (12) resting onto said steel support casing (2) at the level of the upper part or head of said casing (2), and, on the other hand, means (15) for positioning of said casing or production string (3) on said seat (12), said seat (12) ensuring hydraulic continuity of the annular space (6) behind the production or injection string (3), which together with its centering means are made from composite materials, thereby allowing the annular space (6) to be kept free, excepted the presence of the centering means, and to put said annular space (6) and production or injection string (3) under equal pressure while isolating said steel casing (2) from the geothermal fluid or other one which is produced or injected.
2. Device according to claim 1, characterized in that the support of the production string formed by the assembly (4) is designated so as to be able to be lowered and positioned at the same time as the string (3).
3. Device according to claims 1 and 2, characterized in that the assembly (4) supporting the production string (3) is held in position between an upper sleeve (14) and a lower sleeve (17) of a short tube (18) of the string (3) and comprises a seat (12), having openings (13) ensuring the hydraulic continuity of the annular space (6), on which a flange (15) bears with, sandwiched between the seat (12) and the flange (15), a protection (16), the flange (15) blocking the upper sleeve (14) of the production string (3).
4. Device according to claims 1 and 2, characterized in that the production casing (3) comprises a composite material combining for example epoxy resin, aliphatic amines as hardeners, type E glass fibre reinforcement, double filament winding and axial reinforcement.
5. Device according to claims 1 and 4, characterized in the the reinforcement fibres of the casing (3) may be made from carbon or polyaramide.
6. Device according to claims 1, 4 and 5, characterized in that the composite material of the casing (3) comprises anti-abrasion agents.
7. Use of said device according to claim 1, 2 or 3, in an oil well requiring a particular protection with respect to corrosion or deposits.
8. Use of said device according to claim 1, 2 or 3 in any type of well containing, producing or injecting fluids which are aggressive with respect to traditional casings.
9. Use of said device according to claim 1, 2 or 3 in drinking water supply wells.
10. Use of said device according to claim 1, 2 or 3 in residual water injection wells.
11. Use of said device according to claim 1, 2 or 3 in thermal wells.
12. Use of said device according to claim 1, 2 or 3 in production or injection wells within the scope of secondary recovery.

Images