WO2021078572A1 - Process for treating aqueous fluid containing polymers with zirconium salts and alkali metal carboxylates - Google Patents

Process for treating aqueous fluid containing polymers with zirconium salts and alkali metal carboxylates Download PDF

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WO2021078572A1
WO2021078572A1 PCT/EP2020/078670 EP2020078670W WO2021078572A1 WO 2021078572 A1 WO2021078572 A1 WO 2021078572A1 EP 2020078670 W EP2020078670 W EP 2020078670W WO 2021078572 A1 WO2021078572 A1 WO 2021078572A1
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aqueous fluid
water
polymer
aqueous
carboxylate
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PCT/EP2020/078670
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French (fr)
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Bruno Delfort
Isabelle Henaut
Anne Sinquin
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IFP Energies Nouvelles
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E21B21/06—Arrangements for treating drilling fluids outside the borehole
    • E21B21/068—Arrangements for treating drilling fluids outside the borehole using chemical treatment
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
    • C09K8/588—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of specific polymers

Definitions

  • the present invention relates to the field of exploration and exploitation of an underground formation.
  • the invention relates more particularly to the treatment of an aqueous fluid recovered from the subterranean formation.
  • aqueous fluid means any fluid comprising a continuous aqueous phase.
  • the invention relates in particular to the field of enhanced oil recovery (EOR) and to the field of the treatment of produced water.
  • EOR enhanced oil recovery
  • This additive can take the form of a formulation of organic molecules, such as polymers, copolymers and / or surfactants, etc.
  • This formulation can also contain inorganic molecules such as minerals (clays, barite, etc.), oxide particles (titanium oxides, iron oxides, etc.) etc.
  • additive (s) poses certain problems linked in particular to the presence of the additive or of molecules constituting it in the water produced.
  • the injected fluid also called sweeping fluid
  • compounds such as polymers, surfactants, alkaline compounds, or mixtures of these compounds
  • tertiary enhanced recovery when the injected fluid, also called sweeping fluid, is supplemented with compounds such as polymers, surfactants, alkaline compounds, or mixtures of these compounds, it is referred to as tertiary enhanced recovery.
  • the advantage of the presence of a polymer is to increase the viscosity of the purging fluid and consequently to improve the mobility ratio between the injected fluid and the hydrocarbons. in place in the underground formation.
  • the hydrocarbon recovery yield is increased with the aid of a better efficiency of the formation sweeping (Han DK & al, Recent Development of Enhanced oil Recovery in China, J. Petrol. Sci. Eng. 22 (1-3 ): 181-188; 1999).
  • the polymers used in this method are generally polymers of high molecular masses chosen for their viscosifying properties at moderate concentrations. In petroleum production operations water is frequently co-produced with crude oil, a ratio of three barrels of aqueous effluent to one barrel of crude oil is commonly reported.
  • Crude oil and water must be separated.
  • the oil is transported to its refining site and the water is treated to remove unwanted compounds and meet discharge standards.
  • Different techniques are applied to treat production water, in particular to eliminate dispersed drops of crude: sedimentation by gravity separation, centrifugation, flotation with or without gas injection and filtration.
  • a production effluent comprising a mixture of aqueous fluid and hydrocarbons in the form of an emulsion, the water / hydrocarbon ratio of which changes as a function of the production period.
  • the presence of polymer in the production effluent due to the viscosifying effect thereof, makes it more difficult to separate the different fluids (oil / gas / water) and, in particular, the secondary water treatments.
  • the viscosity of the water in the production effluent becomes an obstacle to the separation between water and hydrocarbons.
  • the conventional polymers used in EOR are polymers of high molar masses which generally belong to the family of polyacrylamides (PAM) or partially hydrolyzed polyacrylamides (HPAM). They may optionally contain monomer units of the N-vinylpyrrolidone or acrylamido-tert-butylsulfonate (ATBS) type.
  • PAM polyacrylamides
  • HPAM partially hydrolyzed polyacrylamides
  • ATBS acrylamido-tert-butylsulfonate
  • Polyacrylamides are obtained by radical polymerization of acrylamide according to the following general scheme.
  • the partially hydrolyzed polyacrylamides are copolymers of acrylamide with either acrylic acid or an acrylate, for example an acrylate of an alkaline element such as, for example, sodium. They can be represented, for example, by the following general formula in which the alkaline element is sodium.
  • the acrylamide monomer unit is generally in the majority.
  • the partially hydrolyzed polyacrylamides can be obtained, for example, by copolymerization of acrylamide with acrylic acid, the carboxylic acid function of which can optionally be neutralized into the carboxylate function of an alkaline element such as for example sodium.
  • the partially hydrolyzed polyacrylamides can also be obtained by copolymerization of acrylamide with an acrylate of an alkaline element such as for example the acrylate of sodium.
  • the partially hydrolyzed polyacrylamides can also be obtained by polymerization of acrylamide to polyacrylamide followed by partial hydrolysis of the amide functions to carboxylic acid functions or to carboxylate functions of alkali salts.
  • HPAMs can be random or block copolymers.
  • aqueous solutions of certain polymers exhibit increased viscosities and sometimes form gels following treatment with zirconium salts. Such a treatment can have applications when it is desired to viscosify a fluid.
  • Document SPE-27720-MS and document US Pat. No. 6,737,386 B1 describe the use of zirconium derivatives in order to crosslink polymers belonging to the guar family in order to increase the viscosity of their aqueous solutions with a view to their application as a fluid for hydraulic fracturing.
  • This type of treatment can be carried out with in particular zirconium tetrachloride.
  • This compound has a major drawback. It reacts spontaneously or even violently with water to lead to oxydichlorozirconium of formula ZrOCI 2 and to hydrochloric acid at a rate of two moles of hydrochloric acid per mole of zirconium tetrachloride. Consequently, this results in risks, in particular of corrosion in the event of industrial application.
  • the Applicant has discovered that it is possible to reduce, or even eliminate or cancel the viscosifying effect provided by the polymers used in the fluids formulated to improve enhanced oil recovery, in particular polymers of the partially hydrolyzed polyacrylamide type.
  • HPAM under the successive or simultaneous action of two families of reagents, the objective being to reach or approach the viscosity of the aqueous matrix or simply the viscosity of water.
  • the invention relates to a method of treating an aqueous fluid comprising at least one water-soluble polymer carrying carboxylate or sulphonate functions in the aqueous phase, said method comprising a step of bringing said aqueous fluid into contact with at least one tetravalent zirconium salt and at least one alkaline carboxylate chosen from alkali citrates or alkali propionates; allowing the viscosity of said aqueous fluid to be reduced, in order to produce an aqueous fluid having a lowered viscosity, preferably close to that of water.
  • Said water-soluble polymer can be chosen from: partially hydrolyzed polyacrylamides (HPAM), or partially hydrolyzed polymers comprising units of the N-vinylpyrrolidone or acrylamido-tertiobutylsulfonate (ATBS) type.
  • HPAM partially hydrolyzed polyacrylamides
  • ATBS acrylamido-tertiobutylsulfonate
  • said zirconium salt is chosen from zirconium sulphate, nitrate, carbonate, phosphate and carboxylate.
  • said salt is a zirconium sulfate.
  • said tetravalent zirconium salt is introduced at a content of between 0.3 to 100, preferably between 0.5 to 50 millimoles per gram of polymer present in said aqueous fluid and said alkali carboxylate is introduced at a content of between 3 and 300, preferably between 5 and 100 millimoles per gram of polymer present in said aqueous fluid.
  • said aqueous fluid is contacted with said at least one tetravalent zirconium salt, then with said alkali carboxylate.
  • said aqueous fluid is contacted with said alkali carboxylate, then with said at least one tetravalent zirconium salt.
  • said aqueous fluid is contacted with said at least one tetravalent zirconium salt and with said alkali carboxylate simultaneously.
  • Said tetravalent zirconium salt and said alkali carboxylate can be introduced and dissolved simultaneously in the aqueous fluid containing the polymer.
  • the temperature of the contacting step is between 5 ° C and 90 ° C, preferably between 10 ° C and 80 ° C, very preferably the temperature is room temperature.
  • the contact time corresponding to the duration of the step of bringing into contact said aqueous fluid, said zirconium salt and said alkaline carboxylate is between 15 seconds and 1 hour, preferably between 30 seconds and 10 minutes.
  • Said aqueous fluid may be produced water from enhanced petroleum recovery, said produced water comprising a continuous aqueous phase containing said water-soluble polymer and an organic phase dispersed in said continuous aqueous phase.
  • the concentration of said polymer in said production water can be between 1 ppm and 1000 ppm.
  • the dispersed organic phase can be crude oil, with a concentration of said crude oil in said produced water of preferably between 1 and 900 ppm.
  • the invention also relates to a method for enhanced recovery of crude oil contained in a geological reservoir in which:
  • a flushing fluid comprising at least one water-soluble polymer is injected into said reservoir so as to displace said crude oil towards at least one producing well, said water-soluble polymer carrying carboxylate or sulphonate functions in the aqueous phase;
  • production water comprising a continuous aqueous phase comprising traces of said polymer and an organic phase consisting of droplets of crude oil dispersed in said aqueous phase is recovered at the surface of the producing well;
  • the Applicant has discovered that it is possible to reduce or eliminate or cancel the viscosifying effect provided by the polymers used in the fluids formulated to improve the enhanced recovery of oil, in particular the polymers of HPAM type under the successive or simultaneous action of two families of reagents.
  • the first family of reagents corresponds to the family of tetravalent zirconium salts.
  • the second family of reagents corresponds to certain alkali carboxylates, in particular alkali citrates or alkali propionates.
  • the Applicant has surprisingly discovered that said polymer becomes insoluble in aqueous fluid by reaction with the tetravalent zirconium salt and is in the form of a gel or of a precipitate, then by reaction with certain alkali metal carboxylates, the gel. or the precipitate is dissolved in the medium.
  • the medium obtained then has a viscosity reduced or equal to or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of said polymer has been reduced, or even eliminated or canceled, although it is still present. and soluble in the medium.
  • the Applicant has surprisingly discovered that said polymer in solution with certain alkaline carboxylates becomes by reaction with the tetravalent zirconium salt temporarily insoluble in the aqueous fluid and is in the form of a gel or a precipitate which is rapidly solubilized. in the medium, and that the medium obtained then has a viscosity reduced or equal to / or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of said polymer has been reduced or eliminated / canceled although 'it is always present and soluble in the medium.
  • said polymer in solution can also be treated with a mixture of a tetravalent zirconium salt and certain alkali metal carboxylates and that the medium obtained then has a viscosity reduced to or equal to or close to that of the fluid.
  • aqueous without the presence of the viscosifying polymer indicating that the viscosifying effect of said polymer has been reduced or eliminated / canceled although it is still present and soluble in the medium.
  • the method according to the invention consists in reducing, or even eliminating, or canceling the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution: by bringing said aqueous solution into contact with a tetravalent zirconium salt, which causes the insolubilization of the polymer, then by introducing into the medium in a second step (and preferably in the same equipment, without having to transfer the medium from one equipment to another) certain alkali carboxylates, in particular alkali citrates or alkali propionates, which resolubilizes the polymer.
  • the polymer precipitates. It may then be difficult to separate it from the aqueous solution.
  • the successive combination of the two steps makes it possible to reduce or eliminate or cancel the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution.
  • the invention can be applied to all polymers containing functions allowing the creation of bonds between the zirconium salts and the polymer, in particular the carboxylate functions or the sulphonate functions.
  • the method according to the invention consists in reducing or eliminating or canceling the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution by introducing and dissolving in the aqueous solution containing the polymer certain alkaline carboxylates. , in particular alkali metal citrates or alkali metal propionates, then by introducing into the medium in a second step (and preferably in the same equipment, without having to transfer the medium from one equipment to another) a tetravalent zirconium salt.
  • the method according to the invention consists in reducing or eliminating or canceling the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution:
  • a solution is obtained whose viscosity is reduced to or equal to or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of the polymer has been reduced or deleted or canceled although it is still present and soluble in the medium.
  • zirconium salts the salts or complexes of zirconium will be called “zirconium salts”.
  • the zirconium salt can be chosen from zirconium sulfate, zirconium nitrate, zirconium carbonate, zirconium phosphate, certain carboxylates such as zirconium lactate.
  • the zirconium salt will be zirconium sulfate.
  • the content of said zirconium salt in aqueous solution is advantageously between 50 and 5000 ppm, and preferably between 50 and 1000 ppm.
  • the alkaline carboxylates are chosen from alkaline citrates and alkaline propionates, preferably from sodium citrate (also called trisodium citrate) and sodium propionate.
  • Said tetravalent zirconium salt is advantageously introduced at a content of between 0.3 to 100, preferably 0.5 to 50 millimoles per gram of polymer present in solution in said aqueous fluid and said alkaline carboxylate is advantageously introduced at a content of between 3 and 300 millimoles, preferably between 5 and 100 millimoles per gram of polymer present in solution in said aqueous fluid.
  • the temperature of the contacting step is generally between 5 ° C and 90 ° C, preferably between 10 ° C and 80 ° C, very preferably the temperature is room temperature.
  • the contact time corresponding to the duration of the contacting step between said aqueous fluid, said zirconium salt and said alkali carboxylate is advantageously between 15 seconds and 1 hour, preferably between 30 seconds and 10 minutes.
  • An example of application of the treatment process is the treatment of aqueous fluids resulting from enhanced oil recovery, said fluids frequently containing water-soluble polymers bearing carboxylate or sulphonate functions, of the partially hydrolyzed polyacrylamide HPAM type.
  • said aqueous fluid is produced water from enhanced petroleum recovery, said produced water comprising a continuous aqueous phase containing said water-soluble polymer and an organic phase dispersed in said continuous aqueous phase.
  • concentration of said polymer in said production water is between 1 ppm and 1000 ppm.
  • the dispersed organic phase is crude oil, with a concentration of said crude oil in said production water of preferably between 1 and 900 ppm.
  • aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa are introduced with stirring and at room temperature 50 mg of zirconium sulfate Zr (S0 4 ) 2 , 4 H 2 0.
  • the immediate appearance of a white gel is observed, which is the product of the reaction between the polymer and the zirconium salt.
  • 186 mg of trisodium citrate of crude formula C 6 H 5 0 7 Na 3 , 2 H 2 0 are then introduced into the medium with stirring and at room temperature. The medium becomes clear colorless after 3 minutes.
  • aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa a solution prepared beforehand by mixing 20 mg of zirconium sulphate is introduced with stirring and at room temperature.
  • Example 6 (comparative) Into 20.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa, 20 mg of zirconium sulphate Zr ( S0 4 ) 2 , 4 H 2 0. The presence of a white gel is observed.
  • Examples 1 and 2 illustrate the effectiveness of the treatment involving successively the tetravalent salt of zirconium and the trisodium citrate.
  • Example 3 illustrates the effectiveness of the treatment successively involving the tetravalent salt of zirconium and sodium propionate.
  • Example 4 illustrates the effectiveness of the treatment successively involving the trisodium citrate and the tetravalent salt of zirconium.
  • Example 5 illustrates the effectiveness of the treatment simultaneously involving the trisodium citrate and the tetravalent salt of zirconium.
  • Comparative Example 6 shows that the addition of zirconium sulfate to a polymer solution not followed by the addition of trisodium citrate does not make it possible to obtain a clear single-phase solution.
  • the decrease in the viscosity of the solution thus allows, in a context of enhanced oil recovery, better separation between water and crude oil with which water is frequently coproduced.

Abstract

The invention relates to a process for treating an aqueous fluid comprising at least one water-soluble polymer bearing carboxylate or sulfonate functions in aqueous phase, said process comprising a step of contacting said aqueous fluid with at least one tetravalent zirconium salt and at least one alkali metal carboxylate selected from alkali metal citrates or alkali metal propionates, enabling a reduction in the viscosity of said aqueous fluid, so as to produce an aqueous fluid having a lowered viscosity preferably close to that of water. The invention likewise relates to a process for enhanced recovery of crude oil present in a geological reservoir, in which the production water obtained is treated with said process for treating an aqueous fluid.

Description

Procédé de traitement de fluide aqueux contenant des polymères au moyen de sels de zirconium et de carboxylates alcalins Process for treating aqueous fluid containing polymers using zirconium salts and alkali carboxylates
Domaine technique Technical area
La présente invention concerne le domaine de l'exploration et l'exploitation d'une formation souterraine. L'invention concerne plus particulièrement le traitement d'un fluide aqueux récupéré de la formation souterraine. Par « fluide aqueux » on entend dans la suite de la description tout fluide comprenant une phase aqueuse continue. The present invention relates to the field of exploration and exploitation of an underground formation. The invention relates more particularly to the treatment of an aqueous fluid recovered from the subterranean formation. In the remainder of the description, the term “aqueous fluid” means any fluid comprising a continuous aqueous phase.
L'invention concerne notamment le domaine de la récupération assistée des hydrocarbures (EOR de l'anglais Enhanced Oil Recovery) et le domaine du traitement des eaux de production. The invention relates in particular to the field of enhanced oil recovery (EOR) and to the field of the treatment of produced water.
Technique antérieure Prior art
Pour l'exploration et l'exploitation d'une formation souterraine, il est courant d'injecter un fluide dans la formation souterraine afin d'augmenter l'efficacité des procédés (Han D. K. & al, Recent Development of Enhanced oil Recovery in China, J. Petrol. Sci. Eng. 22(1-3) : 181-188 ; 1999). Pour optimiser ces procédés, il est d'usage d'inclure au moins un additif dans le fluide injecté. Cet additif peut prendre la forme d'une formulation de molécules organiques, telles que des polymères, des copolymères et/ou des tensioactifs, etc. Cette formulation peut également renfermer des molécules inorganiques telles que des minéraux (argiles, barytine, etc.), des particules d'oxydes (oxydes de titane, oxydes de fer, etc.) etc. L'ajout d'additif(s) pose certains problèmes liés notamment à la présence de l'additif ou de molécules le constituant dans l'eau produite. For the exploration and exploitation of an underground formation, it is common to inject a fluid into the underground formation in order to increase the efficiency of the processes (Han DK & al, Recent Development of Enhanced oil Recovery in China, J. Petrol. Sci. Eng. 22 (1-3): 181-188; 1999). To optimize these processes, it is customary to include at least one additive in the injected fluid. This additive can take the form of a formulation of organic molecules, such as polymers, copolymers and / or surfactants, etc. This formulation can also contain inorganic molecules such as minerals (clays, barite, etc.), oxide particles (titanium oxides, iron oxides, etc.) etc. The addition of additive (s) poses certain problems linked in particular to the presence of the additive or of molecules constituting it in the water produced.
Pour la récupération assistée de pétrole, lorsque le fluide injecté, aussi appelé fluide de balayage, est additionné de composés de type polymères, tensioactifs, composés alcalins, ou mélanges de ces composés, on parle de récupération assistée tertiaire. Par rapport à une simple injection d'eau ou de saumure, l'intérêt de la présence d'un polymère est d'augmenter la viscosité du fluide de balayage et par conséquent d'améliorer le rapport de mobilité entre le fluide injecté et les hydrocarbures en place dans la formation souterraine. For enhanced oil recovery, when the injected fluid, also called sweeping fluid, is supplemented with compounds such as polymers, surfactants, alkaline compounds, or mixtures of these compounds, it is referred to as tertiary enhanced recovery. Compared to a simple injection of water or brine, the advantage of the presence of a polymer is to increase the viscosity of the purging fluid and consequently to improve the mobility ratio between the injected fluid and the hydrocarbons. in place in the underground formation.
Le rendement de récupération en hydrocarbures est augmenté à l'aide d'une meilleure efficacité du balayage de la formation (Han D. K. & al, Recent Development of Enhanced oil Recovery in China, J. Petrol. Sci. Eng. 22(1-3) : 181-188 ; 1999). Les polymères utilisés dans cette méthode sont généralement des polymères de fortes masses moléculaires choisis pour leurs propriétés viscosifiantes à concentrations modérées. Lors des opérations de production pétrolière, de l'eau est fréquemment coproduite avec le pétrole brut, un rapport de trois barils d'effluent aqueux pour un baril de pétrole brut est couramment annoncé. The hydrocarbon recovery yield is increased with the aid of a better efficiency of the formation sweeping (Han DK & al, Recent Development of Enhanced oil Recovery in China, J. Petrol. Sci. Eng. 22 (1-3 ): 181-188; 1999). The polymers used in this method are generally polymers of high molecular masses chosen for their viscosifying properties at moderate concentrations. In petroleum production operations water is frequently co-produced with crude oil, a ratio of three barrels of aqueous effluent to one barrel of crude oil is commonly reported.
Le pétrole brut et l'eau doivent être séparés. Le pétrole est transporté sur son lieu de raffinage et l'eau est traitée pour en éliminer les composés indésirables et être conforme aux normes de rejet. Différentes techniques sont appliquées pour traiter les eaux de production notamment pour éliminer les gouttes de brut dispersées : sédimentation par séparation gravitaire, centrifugation, flottation avec ou sans injection de gaz et filtration. Crude oil and water must be separated. The oil is transported to its refining site and the water is treated to remove unwanted compounds and meet discharge standards. Different techniques are applied to treat production water, in particular to eliminate dispersed drops of crude: sedimentation by gravity separation, centrifugation, flotation with or without gas injection and filtration.
L'utilisation de polymères dans la récupération assistée tertiaire pose néanmoins des problèmes pratiques. Au niveau des puits producteurs, on récupère un effluent de production comprenant un mélange de fluide aqueux et d'hydrocarbures sous forme d'une émulsion dont le rapport eau/hydrocarbure évolue en fonction de la durée de production. La présence de polymère dans l'effluent de production, du fait de l'effet viscosifiant de celui-ci, rend plus difficile la séparation des différents fluides (huile/gaz/eau) et, en particulier, les traitements secondaires de l'eau (Zhang Y.Q & al. Treatment of produced water from polymer flooding in oil production by the combined method of hydrolysis acidification dynamic membrane bioreactor-coagulation process, J. Petrol. Sci. Eng., 74 (1- 2) : 14-19, 2010). Lorsque l'effluent de production arrive en surface, il est traité dans une unité de surface. Cette unité permet de séparer les différents fluides, gaz, huile et eau. A l'issue du traitement de surface, les hydrocarbures sont prêts à être raffinés. L'eau est traitée et dépolluée afin de minimiser les rejets de produits toxiques dans l'environnement, dont les seuils sont soumis à des normes. La présence du polymère dans les fluides produits, comme il est rapporté dans le document SPE 65390 (2001) "Emulsification and stabilization of ASP Flooding Produced liquid", peut entraîner la stabilisation des émulsions dans les fluides produits et poser des problèmes au niveau des procédés de traitement de surface, au niveau de la séparation eau/huile/gaz et en particulier, au niveau des procédés de traitement secondaire de l'eau. The use of polymers in tertiary enhanced recovery nevertheless poses practical problems. At the level of the producing wells, a production effluent is recovered comprising a mixture of aqueous fluid and hydrocarbons in the form of an emulsion, the water / hydrocarbon ratio of which changes as a function of the production period. The presence of polymer in the production effluent, due to the viscosifying effect thereof, makes it more difficult to separate the different fluids (oil / gas / water) and, in particular, the secondary water treatments. (Zhang YQ & al. Treatment of produced water from polymer flooding in oil production by the combined method of hydrolysis acidification dynamic membrane bioreactor-coagulation process, J. Petrol. Sci. Eng., 74 (1-2): 14-19, 2010). When the production effluent reaches the surface, it is treated in a unit area. This unit makes it possible to separate the various fluids, gas, oil and water. At the end of the surface treatment, the hydrocarbons are ready to be refined. The water is treated and depolluted in order to minimize the discharge of toxic products into the environment, the thresholds of which are subject to standards. The presence of the polymer in the produced fluids, as reported in the document SPE 65390 (2001) "Emulsification and stabilization of ASP Flooding Produced liquid", can lead to the stabilization of the emulsions in the produced fluids and pose problems at the level of the processes. of surface treatment, at the level of water / oil / gas separation and in particular, at the level of secondary water treatment processes.
Si l'intérêt de la présence d'un polymère est d'augmenter la viscosité de l'eau de balayage pour améliorer l'extraction des hydrocarbures en place dans la formation souterraine, la viscosité de l'eau dans l'effluent de production devient un obstacle à la séparation entre l'eau et les hydrocarbures.If the interest of the presence of a polymer is to increase the viscosity of the flushing water to improve the extraction of hydrocarbons in place in the underground formation, the viscosity of the water in the production effluent becomes an obstacle to the separation between water and hydrocarbons.
Ce problème a amené les opérateurs du domaine à envisager des moyens pour réduire la viscosité de l'eau produite, c'est-à-dire de la phase aqueuse dans l'effluent de production, afin d'améliorer la séparation entre l'eau et les hydrocarbures. Parmi ces moyens, la dégradation du ou des polymères viscosifiants dans l'eau produite est envisagée et est décrite dans l'art antérieur. This problem has led operators in the field to consider means of reducing the viscosity of the water produced, that is to say of the aqueous phase in the production effluent, in order to improve the viscosity of the water produced. separation between water and hydrocarbons. Among these means, the degradation of the viscosifying polymer (s) in the water produced is envisaged and is described in the prior art.
Les polymères conventionnels utilisés en EOR sont des polymères de masses molaires élevées qui appartiennent généralement à la famille des polyacrylamides (PAM) ou des polyacrylamides partiellement hydrolysés (HPAM). Ils peuvent éventuellement renfermer des motifs monomères de type N-vinylpyrrolidone ou acrylamido-tertiobutylsulfonate (ATBS). The conventional polymers used in EOR are polymers of high molar masses which generally belong to the family of polyacrylamides (PAM) or partially hydrolyzed polyacrylamides (HPAM). They may optionally contain monomer units of the N-vinylpyrrolidone or acrylamido-tert-butylsulfonate (ATBS) type.
Les polyacrylamides sont obtenus par polymérisation radicalaire de l'acrylamide selon le schéma général suivant. Polyacrylamides are obtained by radical polymerization of acrylamide according to the following general scheme.
Chem 1
Figure imgf000004_0001
acrylamide polyacrylamide (PAM) Chem 1
Figure imgf000004_0001
acrylamide polyacrylamide (PAM)
Les polyacrylamides partiellement hydrolysés sont des copolymères de l'acrylamide avec soit de l'acide acrylique soit un acrylate par exemple un acrylate d'un élément alcalin tel par exemple le sodium. On peut les représenter par exemple par la formule générale suivante dans laquelle l'élément alcalin est le sodium. Le motif monomère acrylamide est généralement majoritaire. The partially hydrolyzed polyacrylamides are copolymers of acrylamide with either acrylic acid or an acrylate, for example an acrylate of an alkaline element such as, for example, sodium. They can be represented, for example, by the following general formula in which the alkaline element is sodium. The acrylamide monomer unit is generally in the majority.
Chem 2
Figure imgf000004_0002
Les polyacrylamides partiellement hydrolysés peuvent être obtenus par exemple par copolymérisation de l'acrylamide avec de l'acide acrylique dont la fonction acide carboxylique pourra être éventuellement neutralisée en fonction carboxylate d'un élément alcalin tel par exemple le sodium. Les polyacrylamides partiellement hydrolysés peuvent être également obtenus par copolymérisation de l'acrylamide avec un acrylate d'un élément alcalin tel par exemple l'acrylate de sodium. Les polyacrylamides partiellement hydrolysés peuvent également être obtenus par une polymérisation de l'acrylamide en polyacrylamide suivie d'une hydrolyse partielle des fonctions amides en fonction acides carboxyliques ou en fonctions carboxylates de sels alcalins. Chem 2
Figure imgf000004_0002
The partially hydrolyzed polyacrylamides can be obtained, for example, by copolymerization of acrylamide with acrylic acid, the carboxylic acid function of which can optionally be neutralized into the carboxylate function of an alkaline element such as for example sodium. The partially hydrolyzed polyacrylamides can also be obtained by copolymerization of acrylamide with an acrylate of an alkaline element such as for example the acrylate of sodium. The partially hydrolyzed polyacrylamides can also be obtained by polymerization of acrylamide to polyacrylamide followed by partial hydrolysis of the amide functions to carboxylic acid functions or to carboxylate functions of alkali salts.
Les HPAM peuvent être des copolymères statistiques ou à blocs. HPAMs can be random or block copolymers.
La dégradation de ces polymères afin d'atténuer ou de supprimer leur effet viscosifiant est décrite notamment dans le document « SPE-163751 Chemical dégradation of HPAM by oxidization in produced water, (2013) » dans lequel les HPAM sont dégradés par l'action d'agents oxydants tels que le peroxyde d'hydrogène ou le persulfate de sodium ou par photodégradation en présence de dioxyde de titane. The degradation of these polymers in order to attenuate or eliminate their viscosifying effect is described in particular in the document “SPE-163751 Chemical degradation of HPAM by oxidization in produced water, (2013)” in which the HPAMs are degraded by the action of oxidizing agents such as hydrogen peroxide or sodium persulfate or by photodegradation in the presence of titanium dioxide.
Le document SPE-169719-MS « Treating back produced polymer to enable use of conventional water treatment technologies , (2014) » décrit, afin de réduire la viscosité de l'eau produite, la dégradation de polymères HPAM par l'action de différents oxydants tels le persulfate de potassium, le percarbonate de potassium, le peroxyde d'hydrogène, l'hypochlorite de sodium, le réactif de Fenton ou le permanganate de potassium. The document SPE-169719-MS “Treating back produced polymer to enable use of conventional water treatment technologies, (2014)” describes, in order to reduce the viscosity of the water produced, the degradation of HPAM polymers by the action of different oxidants such as potassium persulfate, potassium percarbonate, hydrogen peroxide, sodium hypochlorite, Fenton's reagent or potassium permanganate.
Le document « SPE-179776-MS Management of viscosity of the back produced viscosified water, (2016) » décrit, afin de réduire la viscosité de l'eau produite, la dégradation de polymères HPAM par voie mécanochimique, par voie thermique et par voie chimique notamment au moyen de dérivés chlorés. The document “SPE-179776-MS Management of viscosity of the back produced viscosified water, (2016)” describes, in order to reduce the viscosity of the water produced, the degradation of HPAM polymers by a mechanochemical route, by a thermal route and by a thermal route. chemical, in particular by means of chlorinated derivatives.
Il est également envisageable de ne pas dégrader le polymère pour en supprimer les effets, mais de le séparer du milieu, c'est-à-dire de réduire la concentration en polymère dans le milieu aqueux. It is also conceivable not to degrade the polymer in order to eliminate its effects, but to separate it from the medium, that is to say to reduce the polymer concentration in the aqueous medium.
Il est connu que les solutions aqueuses de certains polymères présentent des viscosités accrues et parfois forment des gels suite à un traitement avec des sels de zirconium. Un tel traitement peut avoir des applications lorsque l'on cherche à viscosifier un fluide. Le document SPE-27720-MS e le document US 6,737,386 B1 décrivent l'utilisation de dérivés du zirconium afin de réticuler des polymères appartenant à la famille des guars afin d'augmenter la viscosité de leurs solutions aqueuses en vue de leur application comme fluide pour la fracturation hydraulique. It is known that aqueous solutions of certain polymers exhibit increased viscosities and sometimes form gels following treatment with zirconium salts. Such a treatment can have applications when it is desired to viscosify a fluid. Document SPE-27720-MS and document US Pat. No. 6,737,386 B1 describe the use of zirconium derivatives in order to crosslink polymers belonging to the guar family in order to increase the viscosity of their aqueous solutions with a view to their application as a fluid for hydraulic fracturing.
Ce type de traitement peut être réalisé avec notamment du tétrachlorure de zirconium. Ce composé présente cependant un inconvénient majeur. Il réagit spontanément voire violemment avec l'eau pour conduire à de l'oxydichlorozirconium de formule ZrOCI2 et à de l'acide chlorhydrique à raison de deux moles d'acide chlorhydrique par mole de tétrachlorure de zirconium. En conséquence, il en résulte des risques notamment de corrosion en cas d'application industrielle. This type of treatment can be carried out with in particular zirconium tetrachloride. This compound, however, has a major drawback. It reacts spontaneously or even violently with water to lead to oxydichlorozirconium of formula ZrOCI 2 and to hydrochloric acid at a rate of two moles of hydrochloric acid per mole of zirconium tetrachloride. Consequently, this results in risks, in particular of corrosion in the event of industrial application.
De manière surprenante, la Demanderesse a découvert que l'on pouvait réduire, voire supprimer ou annuler l'effet viscosifiant apporté par les polymères utilisés dans les fluides formulés pour améliorer la récupération assistée du pétrole, notamment les polymères de type polyacrylamides partiellement hydrolysés de type HPAM sous l'action successive ou simultanée de deux familles de réactifs, l'objectif étant d'atteindre ou de se rapprocher de la viscosité de la matrice aqueuse ou simplement de la viscosité de l'eau. Surprisingly, the Applicant has discovered that it is possible to reduce, or even eliminate or cancel the viscosifying effect provided by the polymers used in the fluids formulated to improve enhanced oil recovery, in particular polymers of the partially hydrolyzed polyacrylamide type. HPAM under the successive or simultaneous action of two families of reagents, the objective being to reach or approach the viscosity of the aqueous matrix or simply the viscosity of water.
Résumé de l'invention Summary of the invention
L'invention concerne un procédé de traitement d'un fluide aqueux comprenant au moins un polymère hydrosoluble porteur de fonctions carboxylates ou sulfonates en phase aqueuse, ledit procédé comprenant une étape de mise en contact dudit fluide aqueux avec au moins un sel de zirconium tétravalent et au moins un carboxylate alcalin choisi parmi les citrates alcalins ou les propionates alcalins ; permettant de réduire la viscosité dudit fluide aqueux, afin de produire un fluide aqueux ayant une viscosité abaissée, de préférence proche de celle de l'eau. The invention relates to a method of treating an aqueous fluid comprising at least one water-soluble polymer carrying carboxylate or sulphonate functions in the aqueous phase, said method comprising a step of bringing said aqueous fluid into contact with at least one tetravalent zirconium salt and at least one alkaline carboxylate chosen from alkali citrates or alkali propionates; allowing the viscosity of said aqueous fluid to be reduced, in order to produce an aqueous fluid having a lowered viscosity, preferably close to that of water.
Ledit polymère hydrosoluble peut être choisi parmi : les polyacrylamides partiellement hydrolysés (HPAM), ou les polymères partiellement hydrolysés comprenant des motifs de type N- vinylpyrrolidone ou acrylamido-tertiobutylsulfonate (ATBS). Said water-soluble polymer can be chosen from: partially hydrolyzed polyacrylamides (HPAM), or partially hydrolyzed polymers comprising units of the N-vinylpyrrolidone or acrylamido-tertiobutylsulfonate (ATBS) type.
De préférence, ledit sel de zirconium est choisi parmi les sulfate, nitrate, carbonate, phosphate, carboxylate de zirconium. Preferably, said zirconium salt is chosen from zirconium sulphate, nitrate, carbonate, phosphate and carboxylate.
De manière très préférée, ledit sel est un sulfate de zirconium. Very preferably, said salt is a zirconium sulfate.
Avantageusement, ledit sel de zirconium tétravalent est introduit à une teneur comprise entre 0,3 à 100, de préférence entre 0,5 à 50 millimoles par gramme de polymère présent dans ledit fluide aqueux et ledit carboxylate alcalin est introduit à une teneur comprise entre 3 et 300, de préférence entre 5 et 100 millimoles par gramme de polymère présent dans ledit fluide aqueux. Advantageously, said tetravalent zirconium salt is introduced at a content of between 0.3 to 100, preferably between 0.5 to 50 millimoles per gram of polymer present in said aqueous fluid and said alkali carboxylate is introduced at a content of between 3 and 300, preferably between 5 and 100 millimoles per gram of polymer present in said aqueous fluid.
Dans un mode de réalisation, ledit fluide aqueux est mis en contact avec ledit au moins un sel de zirconium tétravalent, puis avec ledit carboxylate alcalin. In one embodiment, said aqueous fluid is contacted with said at least one tetravalent zirconium salt, then with said alkali carboxylate.
Dans un autre mode de réalisation, ledit fluide aqueux est mis en contact avec ledit carboxylate alcalin, puis avec ledit au moins un sel de zirconium tétravalent. In another embodiment, said aqueous fluid is contacted with said alkali carboxylate, then with said at least one tetravalent zirconium salt.
Dans un troisième mode de réalisation, ledit fluide aqueux est mis en contact avec ledit au moins un sel de zirconium tétravalent et avec ledit carboxylate alcalin de manière simultanée. On peut introduire et solubiliser simultanément dans le fluide aqueux contenant le polymère ledit sel de zirconium tétravalent et ledit carboxylate alcalin. In a third embodiment, said aqueous fluid is contacted with said at least one tetravalent zirconium salt and with said alkali carboxylate simultaneously. Said tetravalent zirconium salt and said alkali carboxylate can be introduced and dissolved simultaneously in the aqueous fluid containing the polymer.
Il est possible également d'introduire et de solubiliser simultanément dans le fluide aqueux contenant le polymère un mélange préalablement préparé, éventuellement en solution aqueuse, dudit sel de zirconium tétravalent et dudit carboxylate alcalin. It is also possible to introduce and dissolve simultaneously in the aqueous fluid containing the polymer a mixture prepared beforehand, optionally in aqueous solution, of said tetravalent zirconium salt and of said alkali carboxylate.
Avantageusement, la température de l'étape de mise en contact est comprise entre 5°C et 90°C, de préférence entre 10°C et 80°C, de manière très préférée la température est la température ambiante. Advantageously, the temperature of the contacting step is between 5 ° C and 90 ° C, preferably between 10 ° C and 80 ° C, very preferably the temperature is room temperature.
Avantageusement, le temps de contact correspondant à la durée de l'étape de mise en contact entre ledit fluide aqueux, ledit sel de zirconium et ledit carboxylate alcalin est compris entre 15 secondes et 1 heure, de préférence entre 30 secondes et 10 minutes. Advantageously, the contact time corresponding to the duration of the step of bringing into contact said aqueous fluid, said zirconium salt and said alkaline carboxylate is between 15 seconds and 1 hour, preferably between 30 seconds and 10 minutes.
Ledit fluide aqueux peut être une eau de production issue de la récupération assistée de pétrole, ladite eau de production comprenant une phase aqueuse continue contenant ledit polymère hydrosoluble et une phase organique dispersée dans ladite phase aqueuse continue. Said aqueous fluid may be produced water from enhanced petroleum recovery, said produced water comprising a continuous aqueous phase containing said water-soluble polymer and an organic phase dispersed in said continuous aqueous phase.
La concentration dudit polymère dans ladite eau de production peut être comprise entre 1 ppm et 1000 ppm. The concentration of said polymer in said production water can be between 1 ppm and 1000 ppm.
La phase organique dispersée peut être du pétrole brut, avec une concentration dudit pétrole brut dans ladite eau de production de préférence comprise entre 1 et 900 ppm. The dispersed organic phase can be crude oil, with a concentration of said crude oil in said produced water of preferably between 1 and 900 ppm.
L'invention concerne également un procédé de récupération assistée de pétrole brut contenu dans un réservoir géologique dans lequel : The invention also relates to a method for enhanced recovery of crude oil contained in a geological reservoir in which:
- on injecte dans ledit réservoir un fluide de balayage comprenant au moins un polymère hydrosoluble de manière à déplacer ledit pétrole brut vers au moins un puits producteur, ledit polymère hydrosoluble étant porteur de fonctions carboxylates ou sulfonates en phase aqueuse ;- A flushing fluid comprising at least one water-soluble polymer is injected into said reservoir so as to displace said crude oil towards at least one producing well, said water-soluble polymer carrying carboxylate or sulphonate functions in the aqueous phase;
- on collecte un effluent comprenant la majeure partie du pétrole brut par ledit puits producteur ;an effluent comprising the major part of the crude oil is collected by said producing well;
- on récupère en surface du puits producteur un fluide aqueux appelé eau de production comprenant une phase aqueuse continue comprenant des traces dudit polymère et une phase organique constituée de gouttelettes de pétrole brut dispersées dans ladite phase aqueuse ;an aqueous fluid called production water comprising a continuous aqueous phase comprising traces of said polymer and an organic phase consisting of droplets of crude oil dispersed in said aqueous phase is recovered at the surface of the producing well;
- on traite ladite eau de production au moyen du procédé de traitement selon l'une quelconque des variantes décrites. Description des modes de réalisation - Said production water is treated by means of the treatment process according to any one of the variants described. Description of the embodiments
La Demanderesse a découvert que l'on pouvait réduire ou supprimer ou annuler l'effet viscosifiant apporté par les polymères utilisés dans les fluides formulés pour améliorer la récupération assistée du pétrole, notamment les polymères de type HPAM sous l'action successive ou simultanée de deux familles de réactifs. The Applicant has discovered that it is possible to reduce or eliminate or cancel the viscosifying effect provided by the polymers used in the fluids formulated to improve the enhanced recovery of oil, in particular the polymers of HPAM type under the successive or simultaneous action of two families of reagents.
La première famille de réactifs correspond à la famille des sels tétravalents de zirconium. The first family of reagents corresponds to the family of tetravalent zirconium salts.
La deuxième famille de réactifs correspond à certains carboxylates alcalins, notamment des citrates alcalins ou des propionates alcalins. The second family of reagents corresponds to certain alkali carboxylates, in particular alkali citrates or alkali propionates.
La Demanderesse a découvert de façon surprenante que ledit polymère devient insoluble dans le fluide aqueux par réaction avec le sel de zirconium tétravalent et se présente sous la forme d'un gel ou d'un précipité, puis par réaction avec certains carboxylates alcalins, le gel ou le précipité est solubilisé dans le milieu. Le milieu obtenu présente alors une viscosité réduite ou égale à ou proche de celle du fluide aqueux sans la présence du polymère viscosifiant, ce qui indique que l'effet viscosifiant dudit polymère a été réduit, voire supprimé ou annulé bien qu'il soit toujours présent et soluble dans le milieu. The Applicant has surprisingly discovered that said polymer becomes insoluble in aqueous fluid by reaction with the tetravalent zirconium salt and is in the form of a gel or of a precipitate, then by reaction with certain alkali metal carboxylates, the gel. or the precipitate is dissolved in the medium. The medium obtained then has a viscosity reduced or equal to or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of said polymer has been reduced, or even eliminated or canceled, although it is still present. and soluble in the medium.
La Demanderesse a découvert de façon surprenante que ledit polymère en solution avec certains carboxylates alcalins devient par réaction avec le sel de zirconium tétravalent temporairement insoluble dans le fluide aqueux et se présente sous la forme d'un gel ou d'un précipité lequel est rapidement solubilisé dans le milieu, et que le milieu obtenu présente alors une viscosité réduite ou égale à /ou proche de celle du fluide aqueux sans la présence du polymère viscosifiant ce qui indique que l'effet viscosifiant dudit polymère a été réduit ou supprimé/annulé bien qu'il soit toujours présent et soluble dans le milieu. The Applicant has surprisingly discovered that said polymer in solution with certain alkaline carboxylates becomes by reaction with the tetravalent zirconium salt temporarily insoluble in the aqueous fluid and is in the form of a gel or a precipitate which is rapidly solubilized. in the medium, and that the medium obtained then has a viscosity reduced or equal to / or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of said polymer has been reduced or eliminated / canceled although 'it is always present and soluble in the medium.
La Demanderesse a découvert de façon surprenante que ledit polymère en solution peut également être traité avec un mélange d'un sel de zirconium tétravalent et de certains carboxylates alcalins et que le milieu obtenu présente alors une viscosité réduite ou égale à ou proche de celle du fluide aqueux sans la présence du polymère viscosifiant, ce qui indique que l'effet viscosifiant dudit polymère a été réduit ou supprimé/annulé bien qu'il soit toujours présent et soluble dans le milieu. La méthode selon l'invention consiste à réduire, voire à supprimer, ou annuler l'effet d'un polymère viscosifiant de type HPAM, dissout dans une solution aqueuse : en mettant en contact ladite solution aqueuse avec un sel de zirconium tétravalent, ce qui provoque l'insolubilisation du polymère, puis en introduisant dans le milieu dans un deuxième temps (et de préférence dans le même équipement, sans avoir à transvaser le milieu d'un équipement à un autre) certains carboxylates alcalins, notamment des citrates alcalins ou des propionates alcalins, ce qui resolubilise le polymère. The Applicant has surprisingly discovered that said polymer in solution can also be treated with a mixture of a tetravalent zirconium salt and certain alkali metal carboxylates and that the medium obtained then has a viscosity reduced to or equal to or close to that of the fluid. aqueous without the presence of the viscosifying polymer, indicating that the viscosifying effect of said polymer has been reduced or eliminated / canceled although it is still present and soluble in the medium. The method according to the invention consists in reducing, or even eliminating, or canceling the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution: by bringing said aqueous solution into contact with a tetravalent zirconium salt, which causes the insolubilization of the polymer, then by introducing into the medium in a second step (and preferably in the same equipment, without having to transfer the medium from one equipment to another) certain alkali carboxylates, in particular alkali citrates or alkali propionates, which resolubilizes the polymer.
A l'issue de la succession des deux étapes, on obtient une solution dont la viscosité est réduite ou égale à ou proche de celle du fluide aqueux sans la présence du polymère viscosifiant ce qui indique que l'effet viscosifiant du polymère a été réduit, voire supprimé ou annulé bien qu'il soit toujours présent et soluble dans le milieu. At the end of the succession of the two stages, a solution is obtained whose viscosity is reduced to or equal to or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of the polymer has been reduced, even deleted or canceled although it is still present and soluble in the medium.
Lorsque l'on effectue seulement la première étape mentionnée, c'est-à-dire la réaction entre la solution de polymère et le sel de zirconium, le polymère précipite. Il peut-être alors difficile de le séparer de la solution aqueuse. When only the first mentioned step is carried out, i.e. the reaction between the polymer solution and the zirconium salt, the polymer precipitates. It may then be difficult to separate it from the aqueous solution.
La combinaison successive des deux étapes permet de réduire ou de supprimer ou d'annuler l'effet d'un polymère viscosifiant de type HPAM, dissout dans une solution aqueuse. L'invention peut s'appliquer à tous les polymères renfermant des fonctions permettant la création de liaisons entre le sels de zirconium et le polymère notamment les fonctions carboxylates ou les fonctions sulfonates. The successive combination of the two steps makes it possible to reduce or eliminate or cancel the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution. The invention can be applied to all polymers containing functions allowing the creation of bonds between the zirconium salts and the polymer, in particular the carboxylate functions or the sulphonate functions.
La Demanderesse a également découvert que l'on pouvait inverser l'ordre des étapes précédentes, c'est-à-dire que l'on pouvait effectuer la deuxième précédemment décrite suivie de la première étape précédemment décrite . Dans ce cas, la méthode selon l'invention consiste à réduire ou à supprimer ou annuler l'effet d'un polymère viscosifiant de type HPAM, dissout dans une solution aqueuse en introduisant et en solubilisant dans la solution aqueuse contenant le polymère certains carboxylates alcalins, notamment des citrates alcalins ou des propionates alcalins, puis en introduisant dans le milieu dans un deuxième temps (et de préférence dans le même équipement, sans avoir à transvaser le milieu d'un équipement à un autre) un sel de zirconium tétravalent. The Applicant has also discovered that it is possible to reverse the order of the preceding steps, that is to say that it is possible to carry out the second previously described followed by the first step previously described. In this case, the method according to the invention consists in reducing or eliminating or canceling the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution by introducing and dissolving in the aqueous solution containing the polymer certain alkaline carboxylates. , in particular alkali metal citrates or alkali metal propionates, then by introducing into the medium in a second step (and preferably in the same equipment, without having to transfer the medium from one equipment to another) a tetravalent zirconium salt.
A l'issue de la succession de ces deux étapes, on obtient une solution dont la viscosité est réduite ou égale à ou proche de celle du fluide aqueux sans la présence du polymère viscosifiant ce qui indique que l'effet viscosifiant du polymère a été réduit ou supprimé ou annulé bien qu'il soit toujours présent et soluble dans le milieu. At the end of the succession of these two steps, a solution is obtained whose viscosity is reduced to or equal to or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of the polymer has been reduced or eliminated or canceled although it is still present and soluble in the medium.
La Demanderesse a également découvert que l'on pouvait opérer la mise en contact avec les deux réactifs en une seule étape en combinant les deux étapes précédemment décrites. Dans ce cas, la méthode selon l'invention consiste à réduire ou à supprimer ou annuler l'effet d'un polymère viscosifiant de type HPAM, dissout dans une solution aqueuse : The Applicant has also discovered that it is possible to bring the two reagents into contact in a single step by combining the two steps described above. In this case, the method according to the invention consists in reducing or eliminating or canceling the effect of a viscosifying polymer of HPAM type, dissolved in an aqueous solution:
- Soit en introduisant et en solubilisant simultanément dans la solution aqueuse contenant le polymère un sel de zirconium tétravalent ainsi que certains carboxylates alcalins, notamment des citrates alcalins ou des propionates alcalins. - Either by introducing and simultaneously dissolving in the aqueous solution containing the polymer a tetravalent zirconium salt as well as certain alkali carboxylates, in particular alkali citrates or alkali propionates.
- Soit en introduisant et en solubilisant simultanément dans la solution aqueuse contenant le polymère un mélange préalablement préparé, éventuellement dans une solution aqueuse, d'un sel de zirconium tétravalent et de certains carboxylates alcalins, notamment des citrates alcalins ou des propionates alcalins. - Either by introducing and simultaneously dissolving in the aqueous solution containing the polymer a mixture prepared beforehand, optionally in an aqueous solution, of a tetravalent zirconium salt and certain alkali carboxylates, in particular alkali citrates or alkali propionates.
A l'issue de la mise en contact simultanée avec les deux réactifs, on obtient une solution dont la viscosité est réduite ou égale à ou proche de celle du fluide aqueux sans la présence du polymère viscosifiant ce qui indique que l'effet viscosifiant du polymère a été réduit ou supprimé ou annulé bien qu'il soit toujours présent et soluble dans le milieu. At the end of the simultaneous contact with the two reagents, a solution is obtained whose viscosity is reduced to or equal to or close to that of the aqueous fluid without the presence of the viscosifying polymer, which indicates that the viscosifying effect of the polymer has been reduced or deleted or canceled although it is still present and soluble in the medium.
Dans l'ensemble de la description, on appellera les sels ou les complexes du zirconium « sels de zirconium ». Throughout the description, the salts or complexes of zirconium will be called “zirconium salts”.
Le sel de zirconium peut être choisi parmi le sulfate de zirconium, le nitrate de zirconium, le carbonate de zirconium, le phosphate de zirconium, certains carboxylates comme le lactate de zirconium. De préférence, le sel de zirconium sera le sulfate de zirconium. The zirconium salt can be chosen from zirconium sulfate, zirconium nitrate, zirconium carbonate, zirconium phosphate, certain carboxylates such as zirconium lactate. Preferably, the zirconium salt will be zirconium sulfate.
La teneur dudit sel de zirconium en solution aqueuse est avantageusement comprise entre 50 et 5000 ppm, et de préférence entre 50 et 1000 ppm. The content of said zirconium salt in aqueous solution is advantageously between 50 and 5000 ppm, and preferably between 50 and 1000 ppm.
Les carboxylates alcalins sont choisis parmi les citrates alcalins et les propionates alcalins, de préférence parmi le citrate de sodium (également appelé citrate trisodique) et le propionate de sodium. Ledit sel de zirconium tétravalent est avantageusement introduit à une teneur comprise entre 0,3 à 100, de préférence 0,5 à 50 millimoles par gramme de polymère présent en solution dans ledit fluide aqueux et ledit carboxylate alcalin est avantageusement introduit à une teneur comprise entre 3 et 300 millimoles, de préférence entre 5 et 100 millimoles par gramme de polymère présent en solution dans ledit fluide aqueux. The alkaline carboxylates are chosen from alkaline citrates and alkaline propionates, preferably from sodium citrate (also called trisodium citrate) and sodium propionate. Said tetravalent zirconium salt is advantageously introduced at a content of between 0.3 to 100, preferably 0.5 to 50 millimoles per gram of polymer present in solution in said aqueous fluid and said alkaline carboxylate is advantageously introduced at a content of between 3 and 300 millimoles, preferably between 5 and 100 millimoles per gram of polymer present in solution in said aqueous fluid.
La température de l'étape de mise en contact est généralement comprise entre 5°C et 90°C, de préférence entre 10°C et 80°C, de manière très préférée la température est la température ambiante. Le temps de contact correspondant à la durée de l'étape de mise en contact entre ledit fluide aqueux, ledit sel de zirconium et ledit carboxylate alcalin est avantageusement compris entre 15 secondes et 1 heure, de préférence entre 30 secondes et 10 minutes. The temperature of the contacting step is generally between 5 ° C and 90 ° C, preferably between 10 ° C and 80 ° C, very preferably the temperature is room temperature. The contact time corresponding to the duration of the contacting step between said aqueous fluid, said zirconium salt and said alkali carboxylate is advantageously between 15 seconds and 1 hour, preferably between 30 seconds and 10 minutes.
Un exemple d'application du procédé de traitement est le traitement des fluides aqueux issus de la récupération assistée de pétrole, lesdits fluides contenant fréquemment des polymères hydrosolubles porteur de fonctions carboxylates ou sulfonates, de type polyacrylamides partiellement hydrolysés HPAM. An example of application of the treatment process is the treatment of aqueous fluids resulting from enhanced oil recovery, said fluids frequently containing water-soluble polymers bearing carboxylate or sulphonate functions, of the partially hydrolyzed polyacrylamide HPAM type.
Dans un mode de réalisation, ledit fluide aqueux est une eau de production issue de la récupération assistée de pétrole, ladite eau de production comprenant une phase aqueuse continue contenant ledit polymère hydrosoluble et une phase organique dispersée dans ladite phase aqueuse continue. De manière générale, la concentration dudit polymère dans ladite eau de production est comprise entre 1 ppm et 1000 ppm. In one embodiment, said aqueous fluid is produced water from enhanced petroleum recovery, said produced water comprising a continuous aqueous phase containing said water-soluble polymer and an organic phase dispersed in said continuous aqueous phase. In general, the concentration of said polymer in said production water is between 1 ppm and 1000 ppm.
Avantageusement, la phase organique dispersée est du pétrole brut, avec une concentration dudit pétrole brut dans ladite eau de production de préférence comprise entre 1 et 900 ppm. Advantageously, the dispersed organic phase is crude oil, with a concentration of said crude oil in said production water of preferably between 1 and 900 ppm.
EXEMPLES Exemple 1 EXAMPLES Example 1
Dans 50,00 g d'une solution aqueuse contenant 500ppm d'un polymère viscosifiant, de type copolymère d'acrylamide partiellement hydrolysé, appelé également HPAM, de masse molaire 6 MDa, on introduit sous agitation et à la température ambiante 25 mg de sulfate de zirconium Zr(S04)2, 4H20. On constate l'apparition immédiate d'un gel blanc qui est le produit de la réaction entre le polymère et le sel de zirconium. On introduit alors dans le milieu sous agitation et à la température ambiante 131mg de citrate trisodique de formule brute C6H507Na3, H O. Le milieu devient limpide incolore après 3 minutes. In 50.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of the partially hydrolyzed acrylamide copolymer type, also called HPAM, of molar mass 6 MDa, are introduced with stirring and at room temperature 25 mg of sulfate of zirconium Zr (S0 4 ) 2 , 4 H 2 0. We note the immediate appearance of a white gel which is the product of the reaction between the polymer and the zirconium salt. Then introduced into the medium with stirring and room temperature 131 mg of trisodium citrate of crude formula C 6 H 5 0 7 Na 3 , H O. The medium becomes clear colorless after 3 minutes.
Exemple 2 Example 2
Dans 50,00 g d'une solution aqueuse contenant 500ppm d'un polymère viscosifiant, de type copolymère HPAM, de masse molaire 6 MDa on introduit sous agitation et à la température ambiante 50 mg de sulfate de zirconium Zr(S04)2, 4H20. On constate l'apparition immédiate d'un gel blanc qui est le produit de la réaction entre le polymère et le sel de zirconium. On introduit alors dans le milieu sous agitation et à la température ambiante 186mg de citrate trisodique de formule brute C6H507Na3, 2H20. Le milieu devient limpide incolore après 3 minutes. Into 50.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa, are introduced with stirring and at room temperature 50 mg of zirconium sulfate Zr (S0 4 ) 2 , 4 H 2 0. The immediate appearance of a white gel is observed, which is the product of the reaction between the polymer and the zirconium salt. 186 mg of trisodium citrate of crude formula C 6 H 5 0 7 Na 3 , 2 H 2 0 are then introduced into the medium with stirring and at room temperature. The medium becomes clear colorless after 3 minutes.
Exemple 3 Example 3
Dans 20,00 g d'une solution aqueuse contenant 500ppm d'un polymère viscosifiant, de type copolymère HPAM, de masse molaire 6 MDa, on introduit sous agitation et à la température ambiante 300 mg d'une solution de sulfate de zirconium Zr(S04)2, 4H20 à 5,0% en masse. On constate l'apparition immédiate d'un gel blanc qui est le produit de la réaction entre le polymère et le sel de zirconium. On introduit alors dans le milieu sous agitation et à la température ambiante 251mg de propionate de sodium. Le milieu devient limpide incolore après 8 minutes. Into 20.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa, are introduced with stirring and at room temperature 300 mg of a solution of zirconium sulphate Zr ( S0 4) 2 .4H 2 0 to 5.0% by mass. The immediate appearance of a white gel is observed, which is the product of the reaction between the polymer and the zirconium salt. Then introduced into the medium with stirring and at room temperature 251 mg of sodium propionate. The medium becomes clear colorless after 8 minutes.
Exemple 4 Example 4
Dans 20,00 g d'une solution aqueuse contenant 500ppm d'un polymère viscosifiant, de type copolymère HPAM, de masse molaire 6 MDa on introduit sous agitation et à la température ambiante lOOmg de citrate trisodique de formule brute C6H507Na3, 2H20. On introduit ensuite dans le milieu sous agitation et à la température ambiante 300mg d'une solution aqueuse de sulfate de zirconium Zr(S04)2, 4H20 à 2,5% en masse. On constate l'apparition d'un léger trouble blanc qui disparaît après quelques minutes. In 20.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa, 100 mg of trisodium citrate of crude formula C 6 H 5 0 7 are introduced with stirring and at room temperature. Na 3 , 2 H 2 0. Then introduced into the medium with stirring and at room temperature 300 mg of an aqueous solution of zirconium sulphate Zr (S0 4 ) 2 , 4 H 2 0 at 2.5% by mass. A slight white cloudiness appears which disappears after a few minutes.
Exemple 5 Example 5
Dans 20,00 g d'une solution aqueuse contenant 500ppm d'un polymère viscosifiant, de type copolymère HPAM, de masse molaire 6 MDa on introduit sous agitation et à la température ambiante une solution préalablement préparée en mélangeant 20mg de sulfate de zirconium Zr(S04)2, 4H20 et 85mg de citrate trisodique de formule brute C6H507Na3, 2H20 dans 2,00g d'eau. On n'observe aucune présence de gel ou de précipité. Into 20.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa, a solution prepared beforehand by mixing 20 mg of zirconium sulphate is introduced with stirring and at room temperature. Zr (S0 4 ) 2 , 4 H 2 0 and 85 mg of trisodium citrate of the crude formula C 6 H 5 0 7 Na 3 , 2 H 2 0 in 2.00 g of water. No presence of gel or precipitate is observed.
Exemple 6 (comparatif) Dans 20,00 g d'une solution aqueuse contenant 500 ppm d'un polymère viscosifiant, de type copolymère HPAM, de masse molaire 6 MDa on introduit sous agitation et à la température ambiante 20mg de sulfate de zirconium Zr(S04)2, 4H20. On observe la présence d'un gel blanc. Example 6 (comparative) Into 20.00 g of an aqueous solution containing 500 ppm of a viscosifying polymer, of HPAM copolymer type, of molar mass 6 MDa, 20 mg of zirconium sulphate Zr ( S0 4 ) 2 , 4 H 2 0. The presence of a white gel is observed.
Sur chacun des échantillons issus des exemples 1 à 6, ainsi que sur un échantillon de référence composé d'une solution aqueuse contenant 500ppm du même polymère viscosifiant, on a effectué une mesure de viscosité à l'aide d'un rhéomètre rotatif (DHR3 de TA Instruments). Une géométrie de type double cylindre est utilisée. Un balayage logarithmique en écoulement est effectué entre 1 et 200s 1. Les valeurs sont mesurées à 10s 1. Les valeurs mesurées sont reportées dans le tableau 1 suivant. Sur l'échantillon issu de l'exemple 6, aucune mesure de viscosité n'a pu être effectuée. Tableau 1
Figure imgf000013_0001
On each of the samples from Examples 1 to 6, as well as on a reference sample composed of an aqueous solution containing 500 ppm of the same viscosifying polymer, a viscosity measurement was carried out using a rotary rheometer (DHR3 of TA Instruments). Double cylinder geometry is used. A logarithmic flow sweep is performed between 1 and 200s 1 . The values are measured at 10s 1 . The measured values are reported in Table 1 below. On the sample from Example 6, no viscosity measurement could be performed. Table 1
Figure imgf000013_0001
Ces résultats illustrent l'efficacité du procédé de traitement selon l'invention. These results illustrate the effectiveness of the treatment method according to the invention.
Les exemples 1 et 2 illustrent l'efficacité du traitement faisant intervenir successivement le sel tétravalent de zirconium et le citrate trisodique. L'exemple 3 illustre l'efficacité du traitement faisant intervenir successivement le sel tétravalent de zirconium et le propionate de sodium. Examples 1 and 2 illustrate the effectiveness of the treatment involving successively the tetravalent salt of zirconium and the trisodium citrate. Example 3 illustrates the effectiveness of the treatment successively involving the tetravalent salt of zirconium and sodium propionate.
L'exemple 4 illustre l'efficacité du traitement faisant intervenir successivement le citrate trisodique et le sel tétravalent de zirconium. L'exemple 5 illustre l'efficacité du traitement faisant intervenir simultanément le citrate trisodique et le sel tétravalent de zirconium. Example 4 illustrates the effectiveness of the treatment successively involving the trisodium citrate and the tetravalent salt of zirconium. Example 5 illustrates the effectiveness of the treatment simultaneously involving the trisodium citrate and the tetravalent salt of zirconium.
L'exemple comparatif 6 montre que l'addition de sulfate de zirconium à une solution de polymère non suivie par l'addition de citrate trisodique ne permet pas d'obtenir une solution monophasique limpide. Comparative Example 6 shows that the addition of zirconium sulfate to a polymer solution not followed by the addition of trisodium citrate does not make it possible to obtain a clear single-phase solution.
C'est donc bien l'addition des deux familles de réactifs quel que soit l'ordre d'addition qui provoque la meilleure réduction de l'effet du polymère viscosifiant. It is therefore the addition of the two families of reagents regardless of the order of addition which causes the best reduction in the effect of the viscosifying polymer.
La diminution de la viscosité de la solution permet ainsi, dans un contexte de récupération assistée du pétrole, une meilleure séparation entre l'eau et le pétrole brut avec lequel l'eau est fréquemment coproduite. The decrease in the viscosity of the solution thus allows, in a context of enhanced oil recovery, better separation between water and crude oil with which water is frequently coproduced.

Claims

REVENDICATIONS
1. Procédé de traitement d'un fluide aqueux comprenant au moins un polymère hydrosoluble porteur de fonctions carboxylates ou sulfonates en phase aqueuse, ledit procédé comprenant une étape de mise en contact dudit fluide aqueux avec au moins un sel de zirconium tétravalent et au moins un carboxylate alcalin choisi parmi les citrates alcalins ou les propionates alcalins ; permettant de réduire la viscosité dudit fluide aqueux, afin de produire un fluide aqueux ayant une viscosité abaissée, de préférence proche de celle de l'eau. 1. A method of treating an aqueous fluid comprising at least one water-soluble polymer carrying carboxylate or sulphonate functions in the aqueous phase, said method comprising a step of bringing said aqueous fluid into contact with at least one tetravalent zirconium salt and at least one. alkali carboxylate chosen from alkali citrates or alkali propionates; allowing the viscosity of said aqueous fluid to be reduced, in order to produce an aqueous fluid having a lowered viscosity, preferably close to that of water.
2. Procédé de traitement selon la revendication 1 dans lequel ledit polymère hydrosoluble est choisi parmi : les polyacrylamides partiellement hydrolysés (HPAM), ou les polymères partiellement hydrolysés comprenant des motifs de type N-vinylpyrrolidone ou acrylamido- tertiobutylsulfonate (ATBS). 2. Treatment process according to claim 1, in which said water-soluble polymer is chosen from: partially hydrolyzed polyacrylamides (HPAM), or partially hydrolyzed polymers comprising units of the N-vinylpyrrolidone or acrylamido-tertiobutylsulfonate (ATBS) type.
3. Procédé de traitement selon l'une des revendications 1 à 2, dans lequel ledit sel de zirconium est choisi parmi les sulfate, nitrate, carbonate, phosphate, carboxylate de zirconium. 3. Treatment process according to one of claims 1 to 2, wherein said zirconium salt is chosen from zirconium sulphate, nitrate, carbonate, phosphate, carboxylate.
4. Procédé de traitement selon la revendication 3 dans lequel ledit sel est un sulfate de zirconium. 4. The treatment method according to claim 3 wherein said salt is zirconium sulfate.
5. Procédé de traitement selon l'une des revendications 1 à 4 dans lequel ledit sel de zirconium tétravalent est introduit à une teneur comprise entre 0,3 à 100 millimoles, de préférence 0,5 à 50 millimoles par gramme de polymère présent dans ledit fluide aqueux et ledit carboxylate alcalin est introduit à une teneur comprise entre 3 et 300 millimoles, de préférence entre 5 et 100 millimoles par gramme de polymère présent dans ledit fluide aqueux. 5. Treatment method according to one of claims 1 to 4 wherein said tetravalent zirconium salt is introduced at a content of between 0.3 to 100 millimoles, preferably 0.5 to 50 millimoles per gram of polymer present in said. aqueous fluid and said alkaline carboxylate is introduced at a content of between 3 and 300 millimoles, preferably between 5 and 100 millimoles per gram of polymer present in said aqueous fluid.
6. Procédé de traitement selon l'une des revendications 1 à 5 dans lequel ledit fluide aqueux est mis en contact avec ledit au moins un sel de zirconium tétravalent, puis avec ledit carboxylate alcalin. 6. Treatment method according to one of claims 1 to 5 wherein said aqueous fluid is contacted with said at least one tetravalent zirconium salt, then with said alkali carboxylate.
7. Procédé de traitement selon l'une des revendications 1 à 5 dans lequel ledit fluide aqueux est mis en contact avec ledit carboxylate alcalin, puis avec ledit au moins un sel de zirconium tétravalent. 7. Treatment process according to one of claims 1 to 5 wherein said aqueous fluid is contacted with said alkali carboxylate, then with said at least one tetravalent zirconium salt.
8. Procédé de traitement selon l'une des revendications 1 à 5 dans lequel ledit fluide aqueux est mis en contact avec ledit au moins un sel de zirconium tétravalent et avec ledit carboxylate alcalin de manière simultanée. 8. Treatment method according to one of claims 1 to 5 wherein said aqueous fluid is contacted with said at least one tetravalent zirconium salt and with said alkali carboxylate simultaneously.
9. Procédé de traitement selon la revendication 8 dans lequel on introduit et on solubilise simultanément dans le fluide aqueux contenant le polymère ledit sel de zirconium tétravalent et ledit carboxylate alcalin. 9. The treatment process according to claim 8, wherein said tetravalent zirconium salt and said alkali carboxylate are simultaneously introduced and dissolved in the aqueous fluid containing the polymer.
10. Procédé de traitement selon la revendication 8 dans lequel on introduit et on solubilise simultanément dans le fluide aqueux contenant le polymère un mélange préalablement préparé, éventuellement en solution aqueuse, dudit sel de zirconium tétravalent et dudit carboxylate alcalin. 10. The treatment process according to claim 8, in which a previously prepared mixture, optionally in aqueous solution, of said tetravalent zirconium salt and of said alkali carboxylate is introduced and simultaneously dissolved in the aqueous fluid containing the polymer.
11. Procédé de traitement selon l'une des revendications précédentes dans lequel la température de l'étape de mise en contact est comprise entre 5°C et 90°C, de préférence entre 10°C et 80°C, de manière très préférée la température est la température ambiante. 11. Treatment method according to one of the preceding claims wherein the temperature of the contacting step is between 5 ° C and 90 ° C, preferably between 10 ° C and 80 ° C, very preferably. the temperature is the ambient temperature.
12. Procédé de traitement selon l'une des revendications précédentes dans lequel le temps de contact correspondant à la durée de l'étape de mise en contact entre ledit fluide aqueux, ledit sel de zirconium et ledit carboxylate alcalin est compris entre 15 secondes et 1 heure, de préférence entre 30 secondes et 10 minutes. 12. Treatment method according to one of the preceding claims wherein the contact time corresponding to the duration of the contacting step between said aqueous fluid, said zirconium salt and said alkali carboxylate is between 15 seconds and 1. hour, preferably between 30 seconds and 10 minutes.
13. Procédé de traitement selon l'une des revendications précédentes dans lequel ledit fluide aqueux est une eau de production issue de la récupération assistée de pétrole, ladite eau de production comprenant une phase aqueuse continue contenant ledit polymère hydrosoluble et une phase organique dispersée dans ladite phase aqueuse continue. 13. Treatment process according to one of the preceding claims wherein said aqueous fluid is a produced water from enhanced oil recovery, said produced water comprising a continuous aqueous phase containing said water-soluble polymer and an organic phase dispersed in said. continuous aqueous phase.
14. Procédé de traitement selon la revendication 13 dans lequel la concentration dudit polymère dans ladite eau de production est comprise entre 1 ppm et 1000 ppm. 14. The treatment process according to claim 13 wherein the concentration of said polymer in said produced water is between 1 ppm and 1000 ppm.
15. Procédé de traitement selon l'une des revendications 13 ou 14 dans lequel la phase organique dispersée est du pétrole brut, avec une concentration dudit pétrole brut dans ladite eau de production de préférence comprise entre 1 et 900 ppm. 15. Treatment process according to one of claims 13 or 14 wherein the dispersed organic phase is crude oil, with a concentration of said crude oil in said production water preferably between 1 and 900 ppm.
16. Procédé de récupération assistée de pétrole brut contenu dans un réservoir géologique dans lequel : 16. Process for the enhanced recovery of crude oil contained in a geological reservoir in which:
- on injecte dans ledit réservoir un fluide de balayage comprenant au moins un polymère hydrosoluble de manière à déplacer ledit pétrole brut vers au moins un puits producteur, ledit polymère hydrosoluble étant porteur de fonctions carboxylates ou sulfonates en phase aqueuse ; - A flushing fluid comprising at least one water-soluble polymer is injected into said reservoir so as to displace said crude oil towards at least one producing well, said water-soluble polymer carrying carboxylate or sulphonate functions in the aqueous phase;
- on collecte un effluent comprenant la majeure partie du pétrole brut par ledit puits producteur ; an effluent comprising the major part of the crude oil is collected by said producing well;
- on récupère en surface du puits producteur un fluide aqueux appelé eau de production comprenant une phase aqueuse continue comprenant des traces dudit polymère et une phase organique constituée de gouttelettes de pétrole brut dispersées dans ladite phase aqueuse ; an aqueous fluid called production water comprising a continuous aqueous phase comprising traces of said polymer and an organic phase consisting of droplets of crude oil dispersed in said aqueous phase is recovered at the surface of the producing well;
- on traite ladite eau de production au moyen du procédé de traitement selon l'une des revendications 1 à 15. - Said production water is treated by means of the treatment process according to one of claims 1 to 15.
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