WO2019120771A1

WO2019120771A1 - Method for exploiting an underground formation by injecting a fluid comprising an additive provided with magnetic nanoparticles

Info

Publication number: WO2019120771A1
Application number: PCT/EP2018/081211
Authority: WO
Inventors: Eric Lecolier; Jean-Francois Argillier; Yves Benoit; Bruno Delfort; Marie MARSIGLIA
Original assignee: IFP Energies Nouvelles
Priority date: 2017-12-21
Filing date: 2018-11-14
Publication date: 2019-06-27
Also published as: FR3075806A1; EP3728511A1; FR3075806B1

Abstract

The present invention concerns a method for exploiting an underground formation, in which at least one fluid is injected. According to the invention, the fluid comprises at least one additive, the additive being constituted by at least one adjuvant linked to at least one magnetic nanoparticle. In this way, by applying a magnetic field, the additive can be separated from the effluent produced.

Description

PROCESS FOR OPERATING A SUBTERRANEAN FORMATION BY INJECTING A FLUID COMPRISING AN ADDITIVE COMPRISING MAGNETIC NANOPARTICLES

The present invention relates to the field of exploration and exploitation of an underground formation. The invention relates more particularly to the treatment of a fluid recovered from the underground formation.

The invention particularly relates to the field of enhanced oil recovery (EOR) and the field of water treatment production.

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. To optimize these processes, it is customary to include at least one adjuvant in the injected fluid. This adjuvant may take the form of organic molecules, such as polymers, copolymers and / or surfactants, etc. It can also take the form of inorganic molecules such as minerals (clays, barite, etc.), oxide particles (titanium oxides, iron oxides, etc.). Although the method is improved, the addition of adjuvant (s) poses certain problems related in particular to the pollution by the adjuvant of the underground formation, to the pollution by the adjuvant of the water contained in the underground formation, pollution of water and / or hydrocarbons produced by the adjuvant, etc. It is therefore necessary to monitor the behavior of the adjuvant in the subterranean formation.

For enhanced oil recovery, it is interesting to know if the adjuvant used, usually polymers, copolymers and surfactants, is found in the water produced, and if so, to remove this adjuvant from the water produced in order to achieve adequate water treatment.

No current method allows a simple and fast treatment of the effluent, in order to eliminate the injected adjuvants from the effluent.

To solve these problems, the present invention relates to a method of operating a subterranean formation, in which at least one fluid is injected. According to the invention, the fluid comprises at least one additive, the additive consisting of at least one adjuvant bonded to at least one magnetic nanoparticle. In this way, by applying a magnetic field, the additive of the produced effluent can be easily separated (without the need for complex equipment) and quickly (without the need for long separation steps). The process according to the invention

The invention relates to a method of operating a subterranean formation, in which at least one fluid is injected into said subterranean formation, said injected fluid comprising at least one additive. For this process, the following steps are carried out:

a) at least one additive is synthesized by bonding at least one magnetic nanoparticle to at least one adjuvant of said fluid;

b) injecting said fluid comprising said additive into said subterranean formation;

c) recovering at least one effluent from said subterranean formation; and

d) removing said additive present in said effluent by the application of a magnetic field.

According to one embodiment of the invention, said adjuvant is an organic compound such as a polymer, a copolymer, or a surfactant.

Advantageously, said adjuvant is a partially hydrolysed polyacrylamide HPAM or a terpolymer composed of acrylamide, acrylic aid and N-vinylpyrrolidone or acrylamido-tert-butylsulfonate (ATBS), a biopolymer such as xanthan or scleroglucan or a schizophyllane .

Alternatively, said adjuvant is an anti-deposition aid, or a corrosion inhibitor or an anti-hydrate adjuvant.

According to one embodiment of the invention, said recovered effluent is a production effluent of said subterranean formation comprising hydrocarbons, or a fluid taken from an aquifer of said subterranean formation, or a drilling fluid.

In one aspect, said magnetic nanoparticle is coated with silica or alumina.

According to one characteristic, said magnetic nanoparticle comprises a ferromagnetic core, in particular iron, preferably magnetite or maghemite.

According to one embodiment, said additive is synthesized by grafting said magnetic nanoparticle onto the adjuvants or by incorporating said magnetic nanoparticle directly into the structure of the adjuvants or by coating the adjuvants and magnetic nanoparticles with another material.

According to one embodiment, said magnetic nanoparticle is bonded to said adjuvant by a bond of a chemical nature, such as, for example, covalent bonds, or of ionic nature, or of a physical nature such as, for example, electrostatic or hydrophobic or Van der-type associations. Waals.

Preferably, said additive comprising said magnetic nanoparticle present in said effluent is separated by means of at least one magnet located in or near a pipe or a tank or a tank in which the effluent is located. recovered. According to one aspect, said step of separating said additive comprising said magnetic nanoparticle comprises a preliminary step of separating the aqueous and organic phases of said effluent.

According to one characteristic, the process comprises a final step of separating the aqueous and organic phases of said effluent.

Advantageously, said magnetic nanoparticles and / or said labeled additive resulting from the separation step of said additive comprising said magnetic nanoparticle are recycled.

Detailed description of the invention

The present invention relates to a method for operating an underground formation, in which at least one fluid is injected, the fluid comprising at least one additive. For the process according to the invention, the following steps are carried out:

1) Synthesis of the additive, and formulation of the fluid with the additive

2) Injection of the fluid

3) Recovery of an effluent from the underground formation

4) Magnetic separation of the additive and the fluid

According to one embodiment, the method may comprise an optional step:

5) Recycling nanoparticles and / or additive

The injected fluid may be an aqueous fluid or an organic solvent. It may be a drilling fluid, water containing the synthesized additive, a fracturing fluid, a hydrocarbon-assisted recovery fluid, etc.

The fluid additive consists of at least one adjuvant bonded to at least one magnetic nanoparticle

The adjuvant of the injected fluid can take the form of organic molecules, such as polymers, copolymers (for example a polyacrylamide).

Preferably, the adjuvant may be a synthetic polymer such as for example polyacrylamide more or less hydrolysed: HPAM, a copolymer based on acrylamide and sulfonated monomer, or a terpolymer composed of acrylamide, acrylic acid and N - Vinylpyrrolidone or acrylamido-tertiobutylsulfonate (ATBS), or a natural polymer (biopolymer) such as xanthan, scleroglucan or schizophyllan. These polymers are commonly used in the field of enhanced oil recovery (called EOR for Enhanced Oil Recovery) for their viscosifying properties. In addition, these polymers are adapted to be magnetically separable from the fluid in which it has been introduced in a manner that is easy to implement thanks to the grafting of one (or more) magnetic nano or microparticle (s) ( such as iron oxide nanoparticles) on the polymer. By the term "magnetic materials" is meant materials that may have permanent magnetization or that may exhibit magnetization when a magnetic field is applied thereto.

Recovered effluent is understood to mean complex fluids comprising alone or in mixture production water, hydrocarbons, drilling fluids, fracturing fluids, waters of geological formations, etc. The term effluent refers to a complex fluid comprising alone or in combination the production water and hydrocarbons, which can be recovered by a producing well.

1) Synthesis of the additive

According to the invention, the synthesized additive is an adjuvant of the fluid (especially a polymer) which has magnetic properties, and which, when present in the fluid, can be separated and isolated from it using its properties. magnetic, in particular by means of a magnetic field. This step of the process according to the invention consists in bonding at least one adjuvant of the fluid to at least one magnetic nanoparticle. It is recalled that the adjuvants are those used in the petroleum industry and may be of various chemical natures.

The magnetic properties of the additive are provided by one or more magnetic nanoparticles which are bonded to the adjuvant. The bonds may be of a chemical nature, such as, for example, covalent or ionic bonds, or of a physical nature such as, for example, electrostatic or hydrophobic or Van der Waals combinations.

Thus, the magnetic characteristics of the nanoparticles allow their attraction by application of a magnetic field, whatever the fluid in which they are. Thanks to the bond between the adjuvant and the nanoparticle or nanoparticles, the additive thus acquires magnetic properties. Thus, if the additive is present in the recovered effluent, its magnetism allows a simple and rapid separation of the additive present in the recovered effluent (and allow a possible recycling of the additive).

The term fluid adjuvant is any chemical compound that can be added to the fluid to enhance its role in the subsurface formation. The adjuvant may be an organic compound such as a polymer, a copolymer, or a surfactant, especially for an application of an EOR method. Preferably, the adjuvant may be a partially hydrolyzed polyacrylamide HPAM or a terpolymer composed of acrylamide, acrylic acid and N-vinylpyrrolidone or ATBS, a biopolymer such as xanthan or scleroglucan or schizophyllane

The adjuvant may also be an anti-deposition aid, or a corrosion inhibitor or an anti-hydrate adjuvant.

Nanoparticles are objects whose size is typically between 1 and 500 nanometers. Magnetic nanoparticles are formed of a magnetic material or contain a magnetic material.

According to one example, the magnetic material is magnetite, which is iron oxide of formula Fe ₃ O ₄ , which has good magnetic properties Alternatively, the magnetic material is maghemite, which has good magnetic properties.

Magnetic nanoparticles can be synthesized by any means known to those skilled in the art. They can be synthesized by various routes such as the coprecipitation of metal salts, in particular of ferrous and ferric salts, the thermal decomposition of organometallic compounds such as, for example, iron acetylacetonates or iron carboxylates. They can also be synthesized from microemulsions or by hydrothermal syntheses.

These synthetic routes are widely described for example in the documents "magnetic nanoparticles: synthesis, protection, functionnalisation and applications, An-Hui Lu et al, Angew. Chem. int. Ed. 2007, 46, 1222-1244 "or" magnetic iron oxide nanoparticles: synthesis, stabilization, vectorization, physicochemical characterization and biological application, S. Laurent et al., Chem. Rev. 2008, 108, 2064-21 10 ".

For example, the nanoparticles can be synthesized by coprecipitation of ferric and ferrous ions by addition of a base (sometimes called the Massart method), an example of such a method is described in the document "Bee, A .; Massart, R .; Nephew, S. Synthesis of very fine maghemite particles. J. Magn. Magn. Matr. 1995. 149 (1): 6-9 ".

Following the reaction, the nanoparticles can be purified and / or isolated by means of, for example, washing, centrifugation and filtration steps.

The nanoparticles obtained can be isolated or maintained in the form of suspension in a liquid matrix.

Three nonlimiting examples of synthesis of magnetic nanoparticles based on iron are described below:

Example 1: Nanomagnetic MNPs-1 particles: The iron salts FeSO ₄ and FeCl ₃ are mixed in a molar ratio of 1: 2 in 100 ml of water at a temperature of concentration of 0.13 M iron ions. Trisodium citrate is added to the mixture in a molar ratio of 1% based on the total iron concentration. The mixture is stirred vigorously (280 rpm) for 30 minutes with a mechanical stirrer under an argon atmosphere. Then 6 ml of ammonium hydroxide are rapidly injected into the mixture and the reaction is continued for 1 hour at room temperature under argon atmosphere. Example 2: nanomagnetic MNPs-2 particles: This synthesis protocol is similar to the previous one except for the total concentration of iron which is 0.08 M and the addition of citrate which is made after 1 h of synthesis. The medium is then heated at 80 to 90 ° C for 30 minutes. Example 3: Nanomagnetic MNPs-3 particles: This synthesis protocol is similar to the previous one, with the exception of iron sulfate, which is replaced by the same molar amount of ferric chloride FeCl ₂ . The FeCl ₂ and FeCl ₃ salts are mixed at a concentration of 0.08 M in iron ions.

According to one embodiment of the invention, the magnetic nanoparticle may be coated with an inorganic layer, for example silica and / or alumina.

According to one embodiment of the invention, the magnetic nanoparticle may be coated with an organic layer, for example a polymer.

This coating optionally makes it possible to protect the iron oxide from any undesirable reaction, to promote the dispersion of the nanoparticles and also to facilitate the functionalization of the nanoparticle, that is to say the grafting of one or more chemical functions which will allow or promote the bond between the nanoparticle and the adjuvant of the invention such as for example a partially hydrolyzed polyacrylamide type HPAM polymer.

This coating can be carried out by the Stober method described in particular in the document "Stober, W .; Fink, A .; Bohn, E. Controlled growth of monodisperse silica spheres in the micron size range. J. Colloid Interface Sci., 26 (1968), pp. 62-69 ".

According to a non-limiting exemplary embodiment, the magnetic nanoparticle comprises an iron core, for example magnetite or maghemite, covered with a coating which is a layer of silica.

This type of nanoparticle is particularly suitable for grafting on partially hydrolysed polyacrylamide polymers (HPAM). This embodiment is particularly suitable for an EOR enhanced oil recovery process chemical, in which we will inject a formulation containing at least HPAM polymers "magnetic". Thus, when these additives will emerge with the effluent produced, they can be removed in a simple manner, by applying a magnetic field.

The bond between the one or more nanoparticles and the polymeric adjuvant (s) may be carried out either by chemical grafting or by physical interaction.

There are different possibilities for bonding magnetic nanoparticles with polymers. These different techniques are described in the literature and can be adapted to the process according to the invention. They are listed below in a non-exhaustive way.

According to a first variant embodiment, the grafting by chemical bonding can be carried out by means of a covalent bond. These bonds can be created by reactions of specific functions judiciously chosen and available on magnetic nanoparticles and / or on polymeric additives.

According to a second variant embodiment, the grafting may for example be made from a magnetic nanoparticle whose surface carries amine functions. These functions can react chemically with functions carried by a partially hydrolysed polyacrylamide type polymer.

According to a third variant embodiment, the grafting of a magnetic nanoparticle whose surface bears amine functional groups on a partially hydrolysed polyacrylamide-type polymer may be carried out by the direct amidation reaction of a carboxylic function in its acidic form and the amine function carried by the nanoparticle. This reaction can also be carried out according to a well-known method which consists of reacting a carboxylic acid function with a carbodiimide such as 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride followed by reaction with sodium salt. N-hydroxysulfosuccinimide and the reaction with an amine function carried by the nanoparticle.

According to a fourth variant embodiment, it is also possible to carry out the grafting of a magnetic nanoparticle whose surface bears amine functions on a polyacrylamide-type polymer from a predominantly acrylamide-type polymer which is obtained by copolymerization in addition to acrylamide and optionally other monomers such as for example sodium acrylate or acrylic acid of an acrylate or an alkyl methacrylate such as methyl acrylate or ethyl acrylate. The grafting of the nanoparticle is then effected by an amidation reaction between the amine and ester functions introduced into the polymer.

These synthetic routes are illustrated by reaction schemes 1 and 2 below. On these NP representations illustrate the magnetic nanoparticles.

polyacrylamide

partially hydrolysed

Reaction scheme

polyacrylamide-alkyl co-acrylate

Reaction scheme 2

According to the syntheses described above, the magnetic nanoparticles are distributed along the chain of a polymer if each nanoparticle has only one bond with the polymer, but a nanoparticle may be bonded to several polymer chains or several monomers. of the same polymer chain. Similarly, each nanoparticle can be linked to several polymer chains, themselves linked to several nanoparticles thus forming an aggregate-type structure.

It is also possible to synthesize, according to a well-known prior art, magnetic nanoparticles the surface of which carries thiol functional groups and in this case proceed to the polymerization of unsaturated monomers, such as, for example, without being limited to acrylamide, sodium acrylate or acrylic acid, in the presence of a radical polymerization initiator, such as a peroxide or an azo compound. Thus, according to a well-known principle, the thiol function carried by the nanoparticle written here R-SH is converted into radical R-S ° and this radical initiates the polymerization or copolymerization of the monomer or monomers. This amounts to initiating (co) polymerization of acrylamide-type monomers from a nanoparticle. By this way, we obtain mainly magnetic nanoparticles, in which each nanoparticle is bonded to several polymer chains in a so-called star structure.

This synthetic route is illustrated by reaction scheme 3 below. On this NP representation illustrate the magnetic nanoparticles.

Reaction Scheme 3

This type of structure can also be obtained from magnetic nanoparticles whose surface is carrying unsaturated polymerizable functions, for example vinyls. This consists in carrying out the copolymerization of these nanoparticles with unsaturated monomers such as, for example, acrylamide, sodium acrylate or acrylic acid in the presence of a radical polymerization initiator such as a peroxide or an azo compound. The polymerizable unsaturated functional group carried by the nanoparticle participates in the polymerization or copolymerization of the monomer (s). This amounts to integrating one or more nanoparticles into the (co) polymerization of acrylamide-type monomers. By this route, one obtains either magnetic nanoparticles, in which each nanoparticle is bonded to several polymer chains according to a so-called star structure, ie nanoparticles distributed along the chain of a polymer, or aggregate-type structures, in which each nanoparticle can be linked to several polymer chains or several monomers of the same polymer, themselves linked to several nanoparticles.

Alternatively, the bond between the magnetic nanoparticle (s) and the polymer adjuvant (s) can be achieved by physical interaction, it can be:

- coupling by an electrostatic attraction, or

- Hydrophobic attraction coupling between hydrophobic groups of the additive and hydrophobic groups introduced on the surface of the magnetic nanoparticles.

To bind magnetic nanoparticles and polymeric additives, it is noted that the methods described above involve functionalizing the magnetic nanoparticles; the functionalization consists in either modifying the surface state of the magnetic nanoparticles or by coating the nanoparticle with a material having reactive functions, or by grafting chemical groups which will make it possible to establish a link with the chemical groups of the additive to be bonded either to carry out the synthesis of the magnetic nanoparticle or its coating simultaneously with the incorporation of the chemical functions necessary for the bonds with the polymeric additive. Functionalization methods have been well known since the late 1990s. The following articles describe these methods:

Brush Jr. M., Moronne M., Gin P., Weiss S., Alivisatos A.P., 1998, Semiconductor nanocrystals as fluorescent biological labels, Science.

- Chan W.C.W., S. Nie, 1998, Quantum dot bioconjugates for ultrasensitive nonisotopic detection, Science.

Functionalization may consist of grafting organic ligands on the surface of the magnetic nanoparticles. The grafting of the ligands can be carried out on the metal oxide surface or if the magnetic nanoparticle is coated with an inorganic or organic layer, on the surface of the inorganic coating such as for example silica or on the surface of the coating organic.

The coating may be a shell of a polymer or a copolymer having the desired properties, for example, hydrophilicity for use in aqueous media, or, conversely, hydrophobicity for uses in organic solvents .

By way of example, the ligands may be amine, carboxyl, amide, thiol, and the like.

According to an exemplary embodiment, the functionalization of nanoparticles may be carried out by reaction of well-known grafting agents, such as 3-aminopropyltriethoxysilane or 3-mercaptopropyltriethoxysilane, which react with the hydroxyl functions, for example the silanol functions present on the surface of a silica coating. These grafting agents can also react directly with the surface of a nanoparticle made of Fe ₃ O ₄ iron oxide by creating Fe-O-Si chemical bonds. This type of grafting is illustrated by the following reaction schemes 4 or 5.

Reaction Scheme 5 According to one embodiment of the invention, the adjuvant and the magnetic nanoparticle may be embedded in a coating in another material, for example silica and / or alumina.

Following the synthesis, the formulation of the fluid to be injected is carried out with the additive. The type of fluid, the type of additives, and the amount of additives depend in particular on the function of the fluid and the underground formation (constitution, porosity, etc.).

The injected fluid may comprise a single additive. Alternatively, the injected fluid may comprise a plurality of adjuvants, for which a single adjuvant is made magnetic, for example the adjuvant that is the most polluting and that must be treated, or the adjuvant that may end up in the fluid recovered first or the adjuvant most impacting the water / hydrocarbon (oil) separation of the effluent on the surface.

In addition, the injected fluid may comprise a plurality of additives.

2) Injection of the fluid

The fluid prepared with the additive is injected into the subterranean formation. The injection of a fluid into an underground formation can be carried out by any method known in the field of the petroleum industry. This may include an injection of a fluid into an injector well by means of a pumping system.

3) Recovery of an effluent

This step consists in recovering an effluent, called recovered fluid, from the underground formation, which is used during the next separation step. The recovered fluid comprises complex fluids comprising alone or in mixture at least one of the hydrocarbons produced by a producing well, or the water produced by a producing well, or the water taken from the underground formation, in particular the water taken from a well. aquifer of the subterranean formation, or a drilling fluid raised to the surface during the drilling operation, etc.

In addition, the effluent comprises at least a portion of the additive (s) synthesized in step 1) (magnetic renderings) of the injected fluid.

4) Magnetic separation

During this step, the additive (s) synthesized in step 1) (magnetic renderings) contained in the recovered effluent are separated. For this, we use the property magnetic nanoparticle magnetic: the separation is achieved by the application of a magnetic field. Thus, after this step, the remaining effluent is free of any additives injected into the subterranean formation quickly and in a simple manner.

According to one embodiment of the invention, the separation can be carried out by means of a magnet or a series of magnets. For example, the magnet or series of magnets may be placed near a pipe or tank or tank in which the recovered effluent is located. Alternatively, the magnet or series of magnets may be located in a pipe or in a tank or tank.

According to one embodiment of the invention, this separation step may comprise a preliminary step of separating the aqueous (water) and organic (oil) phases of the effluent. The aqueous phase can be treated for recycling (for example reinjected into the subterranean formation). The treatment of the aqueous phase then comprises the step of separating the additive or additives contained in the aqueous phase by magnetism.

In another embodiment of the invention, the step of magnetic separation of the additive (s) may precede the water / oil separation step to facilitate the latter.

For the embodiment in which the additive is the partially hydrolysed polyacrylamide HPAM and in which the magnetic nanoparticles comprise an iron core (for example magnetite or maghemite) covered with a layer of silica, this step consists in separating the HPAM polymer. marked by the magnetic nanoparticles of the recovered effluent.

5) Recycling nanoparticles

It is recalled that this is an optional step of the method according to the invention. Recycling can correspond to:

• the re-use of only magnetic nanoparticles and / or

• the re-use of additives.

According to one embodiment of the invention, the magnetic nanoparticles can be recycled for use again for the synthesis of additives. This step makes it possible to limit the cost of the process according to the invention, by limiting the quantity of magnetic nanoparticles used.

According to one aspect of the invention, for this step, the following steps can be implemented: the additives comprising the magnetic nanoparticles are recovered from the previous step;

the magnetic nanoparticles are separated from the adjuvants, for example by a pyrolysis method;

the magnetic nanoparticles are regenerated to render them suitable for their use; and

the magnetic nanoparticles are recycled at the stage 1) of synthesis of the additives.

According to a variant of this embodiment, this step may also include the regeneration and / or recycling of the additive. This makes it possible to limit the costs associated with the additive injected.

According to a second preferred variant, the additive comprising at least one magnetic nanoparticle (that is to say the adjuvant-mNP assembly) which has been magnetically separated can be directly reused in the formulation of the EOR fluid injected into the underground formation. This is a direct recycling that requires the least amount of operations.

Process applications

The method of operating a subterranean formation according to the invention can be applied to all the processes for which a fluid, which comprises at least one additive, is injected into a subterranean formation, in particular for the exploration and production processes. exploitation of an underground formation. In particular, the operating method according to the invention can be used in an EOR enhanced oil recovery process, a process for treating the water produced, a drilling method, a method for producing oils and / or of bedrock gas, etc.

The various processes of exploration and exploitation of an underground formation are briefly recalled. However, the method according to the invention is not limited to the applications described.

Enhanced Hydrocarbon Recovery (EOR) Process

At the beginning of the operation of an oil reservoir, the pressure prevailing in the deposit is sufficient to produce the hydrocarbons in place. However, over time, the pressure in the reservoir drops and is no longer sufficient to expel the oil from the reservoir rock. After this primary recovery, it becomes necessary to compensate for this pressure drop by injecting either water or gas into the tank. This stage of production is called secondary recovery, but the rate of recovery of hydrocarbons in place is limited to about 30%. The oil industry has developed enhanced oil recovery (EOR). These so-called tertiary recovery techniques aim to modify the mobility and / or saturation of the oil in place in the reservoir rock. Among these improved recovery techniques, there are the EOR-C0 ₂ which consists of the injection of C0 ₂ into the reservoir, and the chemical EOR which consists of injecting solutions of surfactants, microemulsions, or aqueous solutions of synthetic polymers, such as polyacrylamide (for example HPAM), or biopolymers such as xanthan or any other biopolymer (the injection of these polymer solutions is called "polymer flooding").

One of the problems is the presence in the recovered effluent of injected additives. These impacts include the separation of the recovered effluent, the quality of the separated water and the quality of the separated oil, in addition to being a potential pollutant. The method according to the invention makes it possible to solve these problems.

Water / oil separation

When hydrocarbons are recovered, water is also produced, either that which was initially present in the subterranean formation or that which was injected. The water and oil produced are mixed within the effluent. The effluent recovered can be polluted by the various additives injected. There are processes for separating oil and water. However, these separation processes can be rendered less efficient because of the additives present in the effluent. This is why water treatment operations are planned to clean up the effluent produced. In this context, the process according to the invention provides a simple and fast solution to allow a separation of water and oil from a petroleum effluent.

Water treatment on fields with chemical EOR

When hydrocarbons are recovered, water is also produced, either that which was initially present in the subterranean formation or that which was injected. The recovered water can be polluted by the various additives injected. As a result, this water may be unsuitable for reuse or spill into the environment in a natural water reserve. This is why water treatment operations are planned to clean up the water produced. These operations are complex and expensive. The method according to the invention provides a simple and quick solution to this problem.

Process for producing oil and gas from parent rocks

The production of these unconventional oils requires the fracturing of bedrock. The most commonly used technique is hydraulic fracturing. Hydraulic fracturing involves pumping under a very high pressure a fluid containing various additives (solid particles called propellants, polymers-polyacrylamide, ...-, clays, ...) so as to crack the rock. During poorly controlled hydraulic fracturing operations, it is possible that upwellings of the fluids used for fracturing occur and cause pollution. The method according to the invention makes it possible to limit this phenomenon.

Well drilling method

For the drilling of a well, a fluid is injected which fulfills four functions which are: the raising of the rock cuttings, the maintenance in suspension of the cuttings during stops of circulation, the maintenance of the pore pressure at the right of the training as well as the cooling and lubrication of the drill tool. The drilling fluid contains several additives to fulfill these four functions such as viscosifiers, lubricants, defoamers, filtrate reducers, and the like. The dosage of each of the additives of the formulation of the drilling fluid is optimized so that this formulation has the desired properties. The additives can be either organic molecules, such as polymers, copolymers, associative polymers, surfactants, or inorganic particles (clays, barite, etc.). However, a variation in the concentration of additive (s) results in the drilling fluid no longer fulfilling the functions mentioned above. On the drilling platform, a person is responsible for constantly checking that the properties of the drilling fluid are in accordance with the initial specifications. For this purpose, it may be advantageous to have a method for recovering certain additives contained in the drilling fluid once raised to the surface, in particular for the purpose of dosing or reuse for a next formulation.

Method of maintaining the flow (in English flow assurance)

Such a method makes it possible to maintain the flow of hydrocarbons in the subterranean formation, by injecting a fluid comprising flow-enhancing additives, for example anti-scale additives, anti-corrosion additives, and anti-hydrate additives. Examples of anti-deposition additives are polymers (polyacrylates, polycarboxylates, etc.). These additives can be found in the effluent. The method according to the invention makes it possible to limit this pollution.

Claims

claims

1) A method of operating an underground formation, in which at least one fluid is injected into said subterranean formation, said injected fluid comprising at least one additive, characterized in that the following steps are carried out:

c) recovering at least one effluent from said subterranean formation; and

2) The method of claim 1, wherein said adjuvant is an organic compound such as a polymer, a copolymer, or a surfactant.

3) The method of claim 2, wherein said adjuvant is a partially hydrolyzed polyacrylamide HPAM or a terpolymer composed of acrylamide, acrylic acid and N-vinylpyrrolidone or acrylamido-tert-butylsulfonate (ATBS), a biopolymer such as xanthan or scleroglucan or schizophyllane.

4) Process according to claim 1, wherein said adjuvant is an anti-deposition aid, or an anticorrosion adjuvant or an anti-hydrate adjuvant.

5) Method according to one of the preceding claims, wherein said recovered effluent is a production effluent of said subsurface formation comprising hydrocarbons, or a fluid taken from an aquifer of said subterranean formation, or a drilling fluid.

6) Method according to one of the preceding claims, wherein said magnetic nanoparticle is coated with silica or alumina.

7) Method according to one of the preceding claims, wherein said magnetic nanoparticle comprises a ferromagnetic core, in particular iron, preferably magnetite or maghemite.

8) Method according to one of the preceding claims, wherein said additive is synthesized by grafting said magnetic nanoparticle on said adjuvant or by incorporation of said magnetic nanoparticle directly into the structure of said adjuvant or by coating said adjuvant and said magnetic nanoparticle with another material.

9) Method according to one of the preceding claims, wherein said magnetic nanoparticle is connected to said adjuvant by a chemical bond, such as for example covalent bonds, or of ionic nature, or of a physical nature such as electrostatic associations, or hydrophobic or Van der Waals type.

10) Method according to one of the preceding claims, wherein said additive comprising said magnetic nanoparticle present in said effluent is separated by means of at least one magnet located in or near a pipe or reservoir or d a tank in which the recovered effluent is located.

1 1) Method according to one of the preceding claims, wherein said step of separating said additive comprising said magnetic nanoparticle comprises a prior step of separating the aqueous and organic phases of said effluent.

12) Method according to one of claims 1 to 10, wherein the method comprises a final step of separating the aqueous and organic phases of said effluent.

13) Method according to one of the preceding claims, wherein recycling said magnetic nanoparticle and / or said additive from step d) removal of said additive comprising said magnetic nanoparticle.