OA16602A

OA16602A - Bifunctional anti-deposit and anti-corrosion additives.

Info

Publication number: OA16602A
Application number: OA1201400089
Authority: OA
Inventors: Tong Eak. POU
Original assignee: Ceca S.A.
Priority date: 2011-09-05
Filing date: 2012-09-04
Publication date: 2015-11-20

Abstract

The invention concerns bifunctional compositions usable in the field of extraction of hydrocarbons, oil and/or gas, said compositions being homogeneous, clear and stable and comprising at least one anti-mineral-deposit additive, at least one corrosion inhibitor, and at least one agent for compatibilizing between the anti-mineral-deposit additive and the corrosion inhibitor.

Description

The présent invention relates to the field of the extraction of hydrocarbons and more specifically to the additives which are added to said hydrocarbons and/or to fluids comprising said hydrocarbons in order to limit blockages and corrosion of the plants (ducts, valves and others) used for their extraction.

During the extraction of hydrocarbons (or production of hydrocarbons), more particularly during the extraction of crude oïl and the extraction of gas from subsurface strata, water, gas and hydrocarbons are always produced simultaneously and are raised toward the surface. The presence of water, in relatively large amounts, is thus inhérent in the production of hydrocarbons and is the cause of many problems which will disrupt the production lines.

This is because the water présent with the hydrocarbons extracted is often responsible for the corrosion of the pipes, ducts, tubes, valves and other métal components. This water can optionally be reinjected into the subsurface strata in order to help in the extraction of hydrocarbons. In addition, the water generally comprises dissolved or undissolved minerais which can precipitate and/or agglomerate, according to the température, pressure and pH conditions.

In order to solve these problems, it is well known to use several chemical additives which are injected into the mixtures of hydrocarbons, gas and water when they are extracted and/or into the subsurface strata where they are présent, before their extraction.

These additives can be grouped together as corrosion inhibitors (or anticorrosion additives), bactéricides, minerai scale inhibitors, hydrate inhibitors, demulsifiers, asphaltene inhibitors, paraffin inhibitors and others. These products are generally incompatible with one another and it is today necessary to inject them one by one, separately, which multiplies the operations and the storage, circulation and injection Systems.

D. Ann Davis (Development of combined multifunctional chemical inhibitors, 2^ndInternational Conférence on “Controlling Hydrates, Waxes And Asphaltenes”, October 20^2Γ', (1997), Aberdeen, IBC UK Conférences Ltd.) presented various possible asphaltene inhibitors/paraffin inhibitors/mineral scale inhibitors, hydrate inhibitors/corrosion inhibitors/paraffin inhibitors and also minerai scale inhibitors/paraffin inhibitors combinations.

The formulas combining minerai scale inhibitors, which are used to prevent the formation of deposits of minerai salts, such as, for example and without implied limitation, alkali — 2 — métal and alkaline earth métal salts, such as calcium, barium or strontium salts and in particular calcium carbonate and/or calcium or barium sulfates, are not, however, mentioned in this publication. Likewise, this publication does not mention corrosion inhibitors.

s In point of fact, it will be highly advantageous to be able to hâve available such a bifunctional additive simultaneously combinïng the properties of a corrosion inhibitor and the properties of a minerai scale inhibitor. Such a bifunctional additive would make it possible to reduce in particular the number of operations and also the number of injection lines and points, which would represent a considérable saving in the System for the îo extraction of the hydrocarbons.

It has now been discovered, and this represents a first subject matter of the invention, that it is possible to render a corrosion inhibitor and a minerai scale inhibitor compatible, that is to say to obtain a homogeneous, clear and in particular stable solution of at least one corrosion inhibitor and of at least one minerai scale inhibitor, which can be effectively is used during the extraction of hydrocarbons, crude oil and/or gas, either for the extraction proper or in order to be added to the reinjected fluids which comprise a majority of water extracted from the production wells, referred to as production water in the continuation of the présent account.

Thus, the présent invention relates first of ail to a ready-for-use composition comprising: 20

- at least one corrosion inhibitor,

- at least one minerai scale inhibitor, and

- at least one compatibility agent which is a water-soluble nonionic, cationic or amphoteric surfactant.

In the composition according to the invention, the term corrosion inhibitor is understood to mean ail the corrosion inhibitors known to a person skilled in the art, in particular those commonly used in the field of the extraction of hydrocarbons.

More particularly, the corrosion inhibitor(s) which can be used in the compositions of the présent invention are chosen from fatty amines, fatty amine dérivatives (amino acids, 30 aminoalcohols, aminoamines, quaternary ammoniums, pyridine dérivatives), imidazolines substituted by at least one fatty chain, ester amines, ether amines, fatty alcohol dérivatives and phosphoric esters substituted by at least one fatty chain.

The term fatty chain is understood to mean a hydrocarbon radical comprising at least 8 carbon atoms, preferably at least 10 carbon atoms, in particular a hydrocarbon radical 35 comprising from 8 to 40 carbon atoms, preferably from 10 to 30 carbon atoms, more preferably still from 12 to 28 carbon atoms.

— 3 —

Mention may be made, as examples of corrosion inhibitors which can be advantageously used in the compositions of the présent invention, wîthout implied limitation, of the corrosion inhibitors sold by CECA S.A., and in particular those of the Norust® range, for example Amphoram® CP1, Noramium® DA50, and others.

In the composition according to the invention, the term minerai scale inhibitors” is understood to mean ail the minerai scale inhibitors known to a person skilled in the art and in particular those commonly used in the field of the extraction of hydrocarbons. These scale inhibitors are generally anionic compounds, which renders them incompatible with the corrosion inhibitors defined above, which are generally cationic, nonionic or amphoteric compounds.

As nonlimiting examples, the minerai scale inhibitor(s) which can be used in the compositions of the présent invention are chosen from:

- acidic or neutralized aminophosphonates, for example those sold by Solutia under the Dequest® name or by Lanxess under the Bayhibit®name;

- poly(acrylic acid)s and poly(alkyl acrylate)s, such as those sold by Coatex under the generic name Coatex TH®;

- copolymers based on phosphinocarboxylic acids, for example those sold by BWR under the Bellasol®name;

- tannins;

- lîgnosulfonates;

- polyacrylamides;

- naphthalenesulfonates;

- and other minerai scale inhibitors known to a person skilled in the art.

As indicated above, in the field of the extraction of hydrocarbons, corrosion inhibitors are incompatible with scale inhibitors: the inhibitory effectivenesses of the corrosion inhibitors brought about by carbon dioxide (C0₂) and/or hydrogen sulfate (H₂S) are considerably, and even completely, damaged by the minerai scale inhibitors. The compatibility of these two inhibitors is one of the problems to be taken into considération for the sélection of the corrosion inhibitors.

It has now been discovered that it is possible to préparé formulations combining corrosion inhibitors and scale inhibitors while retaining the same degree of effectiveness or at the very least an acceptable degree of effectiveness, both of the corrosion inhibitor and of the minerai scale inhibitor. According to a very particularly preferred embodiment, these formulations (compositions according to the présent invention) are aqueous formulations.

This combination is rendered possible by virtue of the addition of a compatibility agent which thus makes it possible to obtain a homogenous, clear and stable bifunctional — 4 — formulation, without formation of precipitate, having both the properties of a corrosion inhibitor and of a minerai scale inhibitor, it being possible for this bifunctional formulation to be administered by means of just one line for injection into oil and/or gas extraction products, in particular in deep waters.

The compatibility agent présent in the composition according to the présent invention is a surfactant belonging to the family of the nonionic, cationic or amphoteric surfactants and is preferably a surfactant of the family of the ethoxylated fatty-chain amines, quaternized fatty-chain amines, fatty-chain amino acids, oxyethylated and/or oxypropylated and/or oxybutylated condensâtes, alkylarylsulfonates, oxyethylated and/or oxypropylated fattyîo chain alcohols, and others, and also the mixtures of two or more of them in ail proportions, where the expression fatty-chain is as defined above.

Mention may more specifically be made, as nonlimiting examples of surfactants which make possible the compatibility of corrosion inhibitors and minerai scale inhibitors, of in particularly alkoxylated amino acids, alkoxylated imidazolines, Noramox®C11, is Noramium® DA50, Amphoram® CP1, the Pluronic® products and the Remcopal® products, sold by CECA S.A. The term “alkoxylated” describes compounds which hâve been subjected to one or more alkoxylation reactions, in particular ethoxylation (ethoxylated compounds), propoxylation (propoxylated compounds) or butoxylation (butoxylated products) reactions. Preference is given to ethoxylated and/or propoxylated 20 compounds, more preferably ethoxylated compounds.

Among the abovementioned surfactants which can be used as compatibility agents for the compositions according to the présent invention, some of them also exhibit intrinsic corrosion-inhibiting properties. This is the case, for example, for Noramium® DA50, Amphoram® CP1, ethoxylated amines, in particular ethoxylated imidazolines, and 25 Noramox® C11.

As a general rule, in the field of the extraction of hydrocarbons, it is standard to separately treat the extracted fluids with at least one minerai scale inhibitor and with a corrosion inhibitor in a proportion by weight of approximately T.2. In point of fact, in these proportions, the scale inhibitor and the corrosion inhibitor are incompatible. It has now 30 been discovered, entirely surprisingly, that the addition of a compatibility agent, which can itself be a corrosion inhibitor, makes it possible to obtain a homogeneous, clear and stable composition, without the corrosion inhibitor significantly disrupting the scaleinhibiting activity and without the minerai scale inhibitor significantly disrupting the corrosion-inhibiting activity.

According to a preferred embodiment, the composition according to the présent invention also comprises at least one solvent, generally chosen from water, water-soluble organic solvents and water/water-soluble organic solvent(s) mixtures, more preferably from water — 5 — and water/water-soluble organic solvent(s) mixtures. Mention may be made, among water-soluble organic solvents, of alcohols and ethers in particular, among which preference is given to alkanols and glycols, such as, for example and without implied limitation, those chosen from methanol, éthanol, glycol, monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG), 2-butoxyethanol and the mixtures of two or more of them in ail proportions.

Also according to a preferred embodîment, the composition of the présent invention comprises:

- from 10% to 40%, preferably from 15% to 40%, more preferably from 20% to 40%, by weight, of at least one minerai scale inhibitor,

- from 15% to 60%, preferably from 20% to 55%, more preferably from 25% to 50%, by weight, of at least one corrosion inhibitor,

- from 1% to 20%, preferably from 4% to 20%, of at least one compatibility agent as defined above, and

- optionally at least one solvent as defined above in a quantîty suffirent for (q.s. for) reaching 100%.

Unless otherwise indicated, in the description of the présent invention, ail the percentages are expressed in weight.

The composition according to the invention is a stable, homogeneous and clear bifunctional composition exhibiting both the properties of a corrosion inhibitor and of a scale inhibitor. The compatibility agent présent in said bifunctional composition makes it possible to counter or at the very least very greatly reduce the antagonîst effect of the minerai scale inhibitor toward the corrosion inhibitor.

Thus, by virtue of the composition according to the présent invention, a person skilled in the art can hâve available a corrosion inhibitor exhibiting minerai scale-inhibiting properties or alternatively a person skilled in the art can hâve available a minerai scale inhibitor having corrosion-inhibiting properties.

According to another aspect, the présent invention also relates to a bifunctional composition as described above additionally comprising an additive which makes it possible to further Improve the effectiveness of the corrosion-inhibiting composition. This is because, in some cases, it has been observed that the corrosion-inhibiting properties can be detrimentally affected due to the presence of the minerai scale inhibitor, this being the case despite the presence of the compatibility agent.

This problem has been effectively solved by virtue of the presence, in the bifunctional composition according to the invention, of at least one sulfur-comprising additive chosen from mercapto acids, mercapto alcohols, and others, and also mixtures of two or more of them in ail proportions.

— 6 —

According to another aspect, the invention relates to the use of at least one sulfurcomprising additive as defined above in a bifunctional composition comprising at least one minerai scale inhibitor and at least one corrosion inhibitor, this bifunctional composition preferably being used in the field of the extraction of hydrocarbons.

Nonlimiting examples of such sulfur-comprising additives which can advantageously be présent in the bifunctional composition of the invention are mercaptoethanol, mercaptopropanol, thioglycolic acid and mercaptopropionic acid, to mention only the most readily available among them.

Thus, and according to yet another aspect, the présent invention relates to a composition comprising:

- from 1% to 10%, preferably from 3% to 10%, by weight, of at least one sulfurcomprising additive as defined above, and

- optionally at least one solvent as defined above in a quantity sufficient for (q.s. for) reaching 100%.

The bifunctional compositions according to the présent invention can additionally comprise one or more other additives, fillers, and others, which are inert with respect to the effectivenesses of the corrosion inhibitors and minerai scale inhibitors présent in said bifunctional composition.

Such additives are well known to a person skilled in the art and mention may be made, among them, without implied limitation, of stabilizing agents, preservatives, UV inhibitors, flame retardants, solvents, colorants and others.

The bifunctional compositions according to the invention can be prepared by any known means and generally by simple mrxing of the various components of said compositions in any order. However, it is préférable to mix, with stirring, the corrosion inhibitor(s) and the compatibility agent(s), optionally in the solvent(s), then the minerai scale inhibitor(s) and, finally, optionally the sulfur-comprising additive(s) and the other additives defined above.

The bifunctional compositions according to the présent invention thus hâve an entirely advantageous use in the field of the extraction of hydrocarbons, oil and/or gas. These compositions can be injected according to ail methods well known to a person skilled in the art, continuously, batchwise or by the squeeze method, preferably continuously, into the lines for the extraction of said hydrocarbons, into the lines for the injection of — 7 — production waters and generally into any aqueous, organic or aqueous/organic fluîd employed in the fields of extraction of hydrocarbons. It is also possible, for example, to inject these compositions via the gas-lift System well known to a person skilled in the art. The amount of bifunctional formulation according to the invention injected can vary within wide proportions, according to the requirements and the nature and the composition of the products extracted. As a general rule, the amount injected is between 1 ppm and 1000 ppm, preferably between 50 ppm and 800 ppm, where “ppm represents parts by weight of bifunctional composition per one million parts by volume of aqueous, organic or aqueous/organic fluid to be treated.

The présent invention is now illustrated by means of the examples which follow and which do not under any circumstances limit the scope of the protection as applied for in the appended daims.

EXAMPLES

Measurement methods

Minerai scale-inhibiting effectiveness (calcium carbonate):

The calcium carbonate scale-inhibiting effectiveness is determined according to the method of the National Association of Corrosion Engineers (NACE), Standard TM-03074. This method is based on the quantitative détermination of calcium in water in the absence and in the presence of scale inhibitor.

The tests are carried out at 25 ppm (weight/volume) of scale inhibitor in an aqueous calcium carbonate solution.

The scale-inhibiting effectiveness is expressed as a percentage of effectiveness, according to the following relationship:

%Eff (SI) = ([Cæ] - [Cæ]) ([Cai]-[Ca2]) x 100 where: %Eff (SI) represents the percentage of effectiveness of the scale inhibitor, [Ca1] represents the concentration of dissolved calcium ions, before déposition and without inhibitor, [Ca2] represents the concentration of dissolved calcium ions, after déposition and without inhibitor, and [Ca3] represents the concentration of dissolved calcium ions, after déposition and with inhibitor.

Corrosion-inhibiting effectiveness:

The corrosion-inhibiting effectiveness is expressed in the form of rate of corrosion of a carbon steel as a function of time. The rate of corrosion of a steel is determined by the — 8 —

LPR (Linear Polarization Résistance) method. In the presence of corrosion inhibitor, the lower the rate of corrosion, the more effective the inhibitor.

The measurements of rate of corrosion by the LPR method are carried out under the following conditions: The corrosive medium is a 30 g/l aqueous sodium chloride (NaCI) s solution. This solution is deaerated beforehand by sparging with nitrogen for at least one hour. Finally, it is saturated with carbon dioxide (CO₂). The sparging with CO₂ is maintained throughout the duration of the test. The working température is 80°C. The tests are carried out at 50 ppm (weight/volume) of corrosion inhibitor.

The effectiveness of the corrosion inhibitor is expressed as percentage of effectiveness, îo according to the following relationship:

%Eff(CI)J^(RcOn)-^(RcOr2» x 100 (Rcon) where: %Eff (Cl) represents the percentage of effectiveness of the corrosion inhibitor, Rcorl represents the rate of corrosion in the absence of corrosion inhibitor and Rcor2 represents the rate of corrosion in the presence of corrosion inhibitor.

is However, it is standard practice in the field of corrosion inhibition to consider only the residual rate of corrosion (that is to say, after treatment or after injection of the corrosion inhibitor). The lower this residual rate of corrosion, the more effective the corrosion inhibitor. An effective corrosion inhibitor, at a given dose, generally exhibits a residual rate of corrosion of the steel of less than 0.1 mm/year.

Example 1

It is known that a minerai scale inhibitor added to a corrosive medium comprising a corrosion inhibitor brings about a loss of the corrosion-inhibiting activity of the latter.

In order to demonstrate this phenomenon, a corrosion-inhibiting test is carried out 25 according to the LPR method described above, in which test a curve of rate of corrosion as a function of time is plotted for each of the following compositions:

- Composition 1 : CECA Norust® 740 at 50 ppm (weight/volume) in water;

	- Composition 2 (weight/volume) c	!: CECA Norust® 740 at 50 ppm	(weight/volume)	with	10 ppm
)f Bellasol®	S50 from BWR in water;
30	- Composition 3	i: CECA	Norust® 740	at	50 ppm	(weight/volume)	with	25 ppm
	(weight/volume) of Bellasol®	S50 from BWR in water;
	- Composition A	I: CECA	Norust® 740	at	50 ppm	(weight/volume)	with	50 ppm

(weight/volume) of Bellasol® S50 from BWR in water.

The curves of rates of corrosion (Rcor, expressed in mm/year) observed as a function of time, expressed in minutes, for each of compositions 1 to 4 described above are presented in figure 1. As shown in figure 1, the presence of the scale inhibitor — 9 — (Bellasol® S50) results in a loss in effectiveness of the corrosion inhibitor (Norust® 740). The greater the amount of scale inhibitor, the more the corrosion-inhibiting activity decreases.

The antagonist effect of the corrosion inhibitor on the effectiveness of the minerai scale inhibitor is similar. Example 2 illustrâtes this effect.

Example 2

The effectiveness of two calcium carbonate scale inhibitors, Bayhibit® AM50 from Lanxess (25 ppm weight/vol) and Bellasol® S50 from BWR (25 ppm weight/vol), is measured according to the method of the NACE described above, in the absence and in the presence of corrosion inhibitor, Norust® 740 from CECA (50 ppm weight/vol).

The mixture of Norust® 740 with Bayhibit® AM50, in these proportions, exists in the form of a slightly cloudy liquid which might be acceptable in the uses envisaged. However, the effectiveness of this mixture is altogether inadéquate, as is shown by the results presented in table 1 below.

The mixture of Norust® 740 with Bellasol® S50, in these proportions, is not stable and a phase séparation is observed, with précipitation of a viscous gel. This already shows the physical incompatibility of the two types of inhibitors. Furthermore, the antagonist influence of the corrosion inhibitor on the minerai scale inhibitor, as in the case of the mixture described in the preceding paragraph, is presented in table 1 below.

Table 1 -

	Bayhibit® AM50	Bayhibit® AM50 + Norust® 740	Bellasol® S50	Bellasol® ί + Norust® 7
% scaleinhibiting effectiveness	93%	21%	91%	10%

The results of examples 1 and 2 indisputably show the incompatibility between a minerai scale inhibitor and a corrosion inhibitor.

Example 3

A formula F, according to the invention, based on Norust® 740, on Bellasol® S50 and, as compatibility agent, on Noramox® C11 from CECA is prepared. This formula F is clear, stable and homogeneous.

More specifically, the composition of formulation F is as follows:

— 10 —

- Norust® 740: 9%

- Bellasol® S50: 18%

- Noramox® C11: 12%

- Glycolic solvent: q.s. for 100%

The glycolic solvent used is a solvent based on monoethylene glycol.

This formula F is used in tests of corrosion inhibition and of minerai scale-inhibiting effectiveness, as described in examples 1 and 2. The results of the calcium carbonate scale-inhibiting effectiveness are 91% with Bellasol® S50 and 90% with formula F.

From the viewpoint of the minerai scale-inhibiting properties, it is found that formula F exhibits the same effectiveness as the reference inhibitor.

Example 4

A corrosion test according to the LPR method is carried out, as described in example 1, in order to compare the rates of corrosion of formula F with respect to the reference Norust® 740.

At the dose of 50 ppm, Norust® 740 exhibits a stabilized rate of corrosion of less than 0.1 mm/year. At this same dose, formula F exhibits a stabilized rate of corrosion of approximately 0.45 mm/year.

It is thus clearly established that the presence of a compatibility agent in a formulation comprising both a minerai scale inhibitor (SI) and a corrosion inhibitor (Cl) makes it possible to counter the antagonist activity of the SI toward the Cl, and vice-versa. Although this formulation is both corrosion-inhibiting and minerai scale-inhibiting, it is possible to further improve the performance of the corrosion-inhibiting activity.

Example 5

Another formulation of SI and Cl is prepared by adding a sulfur-comprising additive in order to further improve the corrosion-inhibiting performance. This formulation is denoted formula A.

Formula A exhibits the following composition:

Norust® 740:	9%
Bellasol® S50:	18%
Noramox® C11 :	12%
Thioglycolic acid:	4.5%
Glycolic solvent:	q.s. for 100%

— 11 —

This formula A exhibits a minerai scale-inhibiting effectiveness altogether similar to that of the reference scale inhibitor (approxîmately 90%). The formula A is also used in a corrosion inhibition test according to the LPR method.

The curves of rate of corrosion (Rcor, expressed in mm/year) as a functîon of time (expressed in minutes) of composition 1 (reference), of formula F and of formula A are presented in figure 2. It clearly emerges from this figure that the formula A exhibits a stabilized rate of corrosion of less than 0.1 mm/year, of the order of 0.03 mm/year, that is to say altogether similar to that observed for composition 1, which is the reference ίο corrosion inhibitor, Norust® 740.

Claims

1. A composition comprising at least one corrosion inhibitor, at least one minerai scale inhibitor and at least one compatibility agent, in which composition the compatibility agent is

5 a water-soluble nonionic, cationic or amphoteric surfactant.

2. The composition as claimed in claim 1, in which the corrosion inhibitor is chosen from fatty amines, fatty amine dérivatives (amino acids, aminoalcohols, aminoamines, quaternary ammoniums, pyridine dérivatives), imidazolines substituted by at least one fatty îo chain, ester amines, ether amines, fatty alcohol dérivatives and phosphoric esters substituted by at least one fatty chain.

3. The composition as claimed in claim 1 or claim 2, in which the minerai scale inhibitor is chosen from acidic or neutralized aminophosphonates, poly(acrylic acid)s, poly(alkyl is acrylate)s, copolymers based on phosphinocarboxylic acids, tannins, lignosulfonates, polyacrylamides, naphthalenesulfonates and others.

4. The composition as claimed in any one of the preceding daims, in which the compatibility agent is chosen from nonionic, cationic or amphoteric surfactants, preferably

20 from ethoxylated fatty-chain amines, quaternized fatty-chain amines, fatty-chaîn amino acids, oxyethylated and/or oxypropylated condensâtes, alkylarylsulfonates, oxyethylated and/or oxypropylated fatty-chain alcohols, and others, and also the mixtures of two or more of them in ail proportions.

25

5. The composition as claimed in any one of the preceding daims, additionally comprising at least one solvent preferably chosen from water, water-soluble organic solvents and water/water-soluble organic solvent(s) mixtures.

6. The composition as claimed in any one of the preceding daims, comprising: 30 - from 10% to 40%, preferably from 15% to 40%, more preferably from 20% to 40%, by weight, of at least one minerai scale inhibitor,

- from 1% to 20%, preferably from 4% to 20%, by weight, of at least one compatibility agent 35 as defined above, and

- optionally at least one solvent in a quantity sufficient for (q.s. for) reaching 100%.

— 13 —

7. The composition as claimed in any one of the preceding daims, additionally comprising at least one sulfur-comprising additive chosen from mercapto acids, mercapto alcohols and others.

8. The composition as daimed in daim 7, in which the sulfur-comprising additive is chosen from mercaptoethanol, mercaptopropanol, thioglycolic acid and mercaptopropionic acid.

ίο

9. The composition as daimed in either of daims 7 and 8, comprising:

- from 15% to 60%, preferably from 20% to 55%, more preferably from 25% to 50%, by weight, of at least one corrosion inhibitor, is - from 1% to 20%, preferably from 4% to 20%, of at least one compatibility agent as defined above, and

- from 1% to 10%, preferably from 3% to 10%, by weight, of at least one sulfur-comprising additive as defined above, and

10. The use of a composition as daimed in any one of the preceding daims in the field of the extraction of hydrocarbons, oil or gas, continuously, batchwise or by the squeeze method, preferably continuously, in the lines for the extraction of said hydrocarbons.

25

11. The use as daimed in the preceding daim, in which the amount of bifunctional composition injected is between 1 ppm and 1000 ppm, preferably between 50 ppm and 800 ppm (weight/volume).

12. The use of at least one sulfur-comprising additive chosen from mercapto acids or

30 mercapto alcohols in a bifunctional composition used in the field of the extraction of hydrocarbons, said composition comprising at least one minerai scale inhibitor and at least one corrosion inhibitor.