Gas-phase composition for inhibiting corrosion exposed to condensed water

Abstract

The invention relates to a top-of-line corrosion inhibitor composition comprising: at least one amine having a Henry's solubility constant that is strictly less than 20 mol.m-3.Pa-1, preferably less than 10 mol.m-3.Pa-1 and more particularly less than or equal to 5 mol.m-3.Pa-1, even more preferably less than or equal to 1 mol.m-3.Pa-1, at least one compound having both a Henry's solubility constant that is strictly greater than 20 mol.m-3.Pa-1, preferably greater than or equal to 30 mol.m-3.Pa-1, and more particularly greater than or equal to 50 mol.m-3.Pa-1, even more preferably greater than or equal to 100 mol.m-3.Pa-1, preferentially greater than or equal to 500 mol.m-3.Pa-1, even more advantageously greater than or equal to 1000 mol.m-3.Pa-1, and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and at least one sulfur-containing compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and even more preferably greater than or equal to 70°C.

Description

COMPOSITION INHIBITING CORROSION IN THE GAS PHASE EXPOSED TO CONDENSED WATER

[0001] The present invention relates to the field of extraction of hydrocarbons, such as oil and / or gas, and more particularly relates to the problems of corrosion of pipes used for the transport of said hydrocarbons.

[0002] Hydrocarbons from oil deposits most often comprise mixtures of crude oil and gas, with more or less significant quantities of water, forming an aqueous phase in which acid gases, also present in the hydrocarbons, are dissolved at least in part, or even in full.

[0003] Under the effect of the pressure and temperature differences that occur when hydrocarbons rise from deep underground layers to the surface, the water present in said hydrocarbons can condense on the internal walls of the pipes, and mainly on the bottom of the pipes ("Bottom of Line", or "BoL" in English) and on the top of the pipes ("Top of Line", "ToL" in English).

[0004] This acidic aqueous phase causes significant corrosion of the pipes, called "bottom of line corrosion" and "top of line corrosion" or "TLC" on the pipe vaults.

[0005] Top-of-the-Line Corrosion (TLC) is a significant global phenomenon in the crude oil and gas extraction industry, and is particularly problematic for both offshore and onshore fields (see for example the work of M. Singer et al. "Sour Top-of-the-Line Corrosion in the Presence of Acetic Acid", Corrosion, 67, (2011), pages 085003 sqq., or: http: / / corrosion.curtin.edu.au / research / topofline.cfm).

[0006] Indeed, under laminar (or stratified) flow conditions of the transported fluids, and when condensation conditions are met, we very often observe localized internal corrosion at the roof of horizontal pipes. This corrosion is mainly due to condensation water on the roof of the pipes, which contains dissolved acid gases, in particular hydrogen sulfide (H2S) and carbon dioxide (CO2), but also organic acids, for example acetic acid.

[0007] More specifically, in multiphase pipelines for transporting oil and / or wet gas with stratified, wave or wave-stratified flow regimes, the liquid phase flows in the lower part of the pipe, while the gas phase flows in the upper part of the pipe.

[0008] The gas phase most often contains acid gases, such as CO2, H2S, but also acid organic gases, such as acetic acid and formic acid. The liquid phase contains hydrocarbons and a significant amount of water.

[0009] To protect the inner wall of the pipe against corrosion caused by acids, it is common to inject a corrosion inhibitor into the pipe, immediately after leaving the extraction well, which mixes with the liquid phase. However, when the flow regime is stratified, wave or stratified wave, only the lower part of the pipe that is in contact with the liquid phase is effectively protected against corrosion.

[0010] However, at present, hydrocarbon extraction temperatures are increasingly high, which greatly increases the risks of vault corrosion. Indeed, under the action of heat, the water contained in the liquid phase transforms into water vapor, which condenses on the inner wall of the vault of the pipes, when the outer wall of the latter is at a lower temperature (particularly in the case of underwater pipes).

[0011] This condensation water has a very significant corrosive effect on the pipe vault, causing considerable damage to the pipes, ranging from simple corrosion pitting to the destruction of the wall and the leakage of hydrocarbons, which is completely unacceptable from the point of view of environmental protection. Such damage would lead to considerable economic losses, in terms of decontamination, hydrocarbon losses, and also in terms of repairing damaged pipes.

[0012] There are already various chemical treatments, in batch and / or continuous, in association or not with mechanical treatments, but these are little or not at all accepted by manufacturers, in particular because of their unsatisfactory effectiveness.

[0013] Among the various methods and devices proposed in the past, to prevent, or at least limit, the corrosion of the roof of hydrocarbon pipes, one of the said methods consists of sending into the pipe one or more scrapers, of section slightly smaller than the internal section of the pipe and spaced along the pipe, the space between the scrapers being filled with a plug of inhibiting liquid. Patent application FR 2 791 695 proposes another scraper system, in association with corrosion inhibitors.

[0014] Among the chemical treatments intended to limit carbonic corrosion (due to CO2) and / or hydrogen sulfide corrosion (due to H2S), the use of numerous inhibitors is recommended to effectively protect the metal of the pipes against one and / or the other of these corrosions, by continuous or batch injection into the corrosive fluid, said fluid thus being distributed homogeneously throughout said pipes.

[0015] However, the treatment conditions prove to be delicate or even difficult, particularly in the case where two or even three of the following parameters are combined: laminar (or stratified) flow of the corrosive fluid, cooling of the pipeline due to lack of insulation and the presence of organic acid (in particular acetic acid) in the liquid phase.

[0016] To combat this type of top of line corrosion (TLC), YM Gunaltun et al. (“Control of Top of line corrosion by chemical treatment”, NACE Corrosion, (2001), n° 01033) recommend batch treatment, or injection, with a persistent inhibitor comprising methyldiethanolamine (MDEA), in order to neutralize the acidity of the corrosive aqueous medium of the base matrix (BLC).

[0017] However, it was found that this amine does not neutralize the acidity of the condensate (condensed water droplets) on the roof of said pipes.

[0018] RL Martin, in "Inhibition of Vapor Phase Corrosion in gas pipelines", NACE Corrosion, (1997), No. 337, and NN Andreev et al., in "Volatile Inhibitors for CO2 Corrosion", NACE Corrosion, (1998), No. 241, proposed volatile corrosion inhibitors (VCIs) at very high dosages (of the order of a few percent).

[0019] G. Schmitt et al., in "Inhibition of the top of line corrosion under stratified flow", NACE Corrosion, (2001), No. 01032, proposed using a so-called "climbing" inhibitor introduced into the corrosive medium like a conventional inhibitor. Due to its very low surface tension, this type of inhibitor would climb all along the wall towards the top inside the pipe (midday position), thus inhibiting crown corrosion.

[0020] There is a real need for new treatments that can effectively combat corrosion of the vault of hydrocarbon pipes.

[0021] International application WO2013038100 describes compositions for inhibiting corrosion of hydrocarbon pipeline vaults that are effective, but which can still be improved. Indeed, corrosion inhibiting compositions are sought which have the highest possible flash points. However, based on this document, the inventors found that by removing the amine with the highest vapor pressure from the composition, and therefore the most volatile, the flash point of the composition was found to be higher.

[0022] Furthermore, the compositions obtained exhibit satisfactory, or even better, corrosion rates, i.e. lower. However, vault corrosion still remains present, in particular due to the lack of the most volatile amine which seems necessary to increase the flash point of the corrosion inhibiting composition.

[0023] The present invention proposes to solve the problem of corrosion of the vault of metal pipes, in particular steel pipes, used during the extraction of hydrocarbons, and in which corrosive fluids circulate and / or are present (i.e. water containing CO2 and / or H2S and / or one or more organic acids, generally acetic acid).

[0024] Thus, and according to a first aspect, the present invention relates to a composition inhibiting corrosion of the upper part (or vault) of a pipe for transporting wet hydrocarbons, that is to say hydrocarbons comprising a more or less significant quantity of water.

[0025] The composition according to the present invention comprises compounds which, once introduced into the corrosive medium by injection, continuously or in batch, preferably continuously, on the one hand neutralize the acidity of the corrosive medium in the phase where there is laminar flow and on the other hand pass into the vapor phase to neutralize the acidity of the water droplets, which are condensed (condensate) on the upper internal vault of the pipe transporting the extracted hydrocarbons.

[0026] More specifically, the present invention relates to a vault corrosion inhibiting composition comprising: - at least one amine with a Henry solubility constant strictly less than 20 mol.rrr 3 .Pa' 1 , preferably less than 10 mol.nr 3 .Pa' 1 and more particularly, less than or equal to 5 mol.nr 3 .Pa' 1 , better less than or equal to 1 mol.rrr 3 .Pa' 1 , - at least one compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 , preferably greater than or equal to 30 mol.rrr 3 .Pa' 1 , and more particularly greater than or equal to 50 mol.nr 3 .Pa' 1 , more preferably greater than or equal to 100 mol.nr 3 .Pa' 1 , preferably greater than or equal to 500 mol.nr 3 .Pa' 1 , still advantageously greater than or equal to 1000 mol.rrr 3 .Pa' 1 and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and - at least one sulfur compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and more preferably greater than or equal to 70°C.

[0027] Other advantageous characteristics of the composition according to the invention are specified below.

[0028] The amine present in the composition is chosen from methylamine, ethylamine, 1-propanamine, 2-propanamine, 1-butanamine, 2-butanamine, 2-methyl-1-propanamine, 2-methyl-2-propanamine, 1-pentanamine, 3-methyl-butanamine, 1-hexanamine, 4-methyl-2-hexanamine, 1-heptanamine, 1-octanamine, 2-ethyl-1-hexanamine, dimethylamine, 1-tridecanamine, diethylamine and dipropylamine and mixtures thereof.

[0029] The compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and a pKa strictly greater than 7 is chosen from monoethanolamine, diethanolamine, triethanolamine, and 1-aminopropanol.

[0030] The sulfur compound present in the composition is chosen from mercaptoethanol, mercaptopropanol, thioglycolic acid, 3-mercaptopropionic acid (AMP), 2-mercaptopropionic acid (or thiolactic acid (ATL), 3,3'-dithiodiproponic acid (DTDP), diammonium dithiodiglycolate (DTDG), sodium thioglycolate, sodium thiosulfate, ethylhexyl thioglycolate, 1,8-dimercapto-3,6-dioxaoctane (DMDO), mercaptoethyl ether, sodium thiosulfite, ammonium thiosulfite, ammonium thiosulfate, potassium thiosulfate, potassium thiosulfite, thiourea, sodium thiocyanate, thiocyanate ammonium, calcium thiocyanate, sodium thioglycolate, ammonium thioglycolate, 1,2-diethylthiourea, propylthiourea, 1,1-diphenylthiourea, thiocarbanilide, 1,2-dibutylthiourea, dithiourea, thioacetamide, thionicotimide, thiobenzamide, 2-mercaptoethanol, 3-(methylthio)propanal, thioacetic acid, cysteamine, 3-chloro-1-propanethiol, 1-mercapto-2-propanol, 2, 3-dimercapto-1 -propanol, 2-methoxyethanethiol, 3-mercapto-1 -propanol, 2, 3-dimercapto-1 -propanol, 1 -thio-glycerol, 1 ,3-propane-dithiol, mercaptosuccinic acid, cysteine, N-carbomoyl-L-cysteine, N-acetylcysteamine, 4-mercapto-1 -butanol, 1 -butanedithiol, 1 ,4-butanedithiol, 2,2'-thiodietanethiol, 4-cyano-1 -butanethiol, cyclopantanethiol, 1 ,5-pentanedithiol, 2-methyl-1-butanethiol, 2,3,5,6-tetrafluorobenzenethiophenol, 4-chlorothiophenol, 2-mercaptophenol, thiophenol, cyclohexylthiol, 4-mercaptobenzoic acid, thiosalicylic acid, 2-ethylhexanethiol and compounds of formula C n H2n+iSH with n between 1 and 10, limits included.

[0031] The composition includes: - from 10 to 60% by weight relative to the total weight of the composition of an amine having a Henry solubility constant strictly less than 20 mol.rrr 3 .Pa' 1 , - from 20% to 89.9% by weight relative to the total weight of the composition of a compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and having a pKa strictly greater than 7, - from 0.1 to 20% by weight relative to the total weight of the composition of a sulfur compound.

[0032] The composition comprises at least one imidazoline.

[0033] According to another aspect, the invention also relates to the use of an inhibiting composition as defined in any one of the preceding claims, for inhibiting the corrosion of the roof of hydrocarbon pipes in which liquid and / or gaseous hydrocarbons circulate, preferably gases, gas condensates, crude oil, alone or in a mixture.

[0034] Preferably, the inhibitory composition useful in the process is injected, preferably continuously, at a rate of 10 ppm to 10,000 ppm by volume of corrosion inhibiting composition for a part by volume of fluids circulating in the pipe.

[0035] The invention also relates to a method for inhibiting the corrosion of the vault of a pipe comprising at least one step of continuous or batch introduction, preferably continuous, into said pipe in which fluids circulate, in particular liquid and / or gaseous hydrocarbons, preferably gases, gas condensates, crude oil, alone or in a mixture of at least one corrosion inhibiting composition as defined above.

[0036] Preferably, according to this method, the composition as defined above is injected at a rate of 10 ppm to 10,000 ppm by volume of composition for a part by volume of fluids circulating in said pipe. Preferably, the method comprises one or more physical treatment steps, in particular using scrapers.

[0037] Other features, aspects, objects and advantages of the present invention will become even more apparent from the following description.

[0038] It is specified that the expressions “from ... to ...” and “between ... and ....” used in this description must be understood as including each of the limits mentioned.

[0039] The composition according to the invention comprises compounds defined by their Henry solubility constant (Hep). This constant expresses the ratio of the substance studied solubilized and distributed between the aqueous phase and the gas phase. This constant is defined by the following formula: Hep = ca / p, where ca denotes the concentration of the substance in the aqueous phase, p denotes the vapor pressure of this substance in the gas phase under equilibrium conditions.

[0040] The international unit for this constant is mol.nr 3 .Pa' 1 .

[0041] The constants are given at room temperature, i.e. between 20°C and 25°C and at 1 atmosphere (101,325 Pa).

[0042] R. Sander listed in the article Atmos. Chem. Phys., 15, (2015), pp. 4399-4981, “Compilation of Henry's law constants (version 4.0) for water as solvent”, the Henry's constants for 4632 chemical substances.

[0043] The composition according to the invention is defined by its flash point or flash point. The flash point designates the lowest temperature at which a combustible body emits sufficient vapors to form, with the ambient air, a gaseous mixture which ignites under the effect of a heat energy source such as a pilot flame, but not sufficiently for combustion to sustain itself.

[0044] The flash point of the composition is determined by applying the closed cup method according to ISO 3679-2015.

[0045] The composition according to the invention also comprises a compound defined by its pKa. This is the opposite of the logarithmic value of the acidity constant corresponding to the following formula: pKa = -log Ka.

[0046] The chemical equilibrium of acid dissociation can be written symbolically: AH — > A- + H + , a reaction in which the compound AH is a generic acid dissociating into A-, called its conjugate base, and the hydrogen ion H + , commonly called "proton", which, if the reaction takes place in aqueous solution, exists only in the form of hydronium ion, HsO + , or in other words a solvated proton.

[0047] The chemical species AH, A- and H + are said to be in equilibrium if their concentration does not vary with time. The equilibrium constant is usually written in terms of the quotient of the concentrations of the different species at equilibrium (in mol.L' 1), noted [AH], [A-] and [H + ],

[0048] The composition according to the invention comprises at least one amine having a Henry solubility constant strictly less than 20 mol.rrr 3 .Pa' 1 .

[0049] Advantageously, the compound has a Henry solubility constant less than or equal to 10 mol.nr 3 .Pa' 1 , and more particularly, less than or equal to 5 mol.nr 3 .Pa' 1 , better less than or equal to 1 mol.nr 3 .Pa' 1 .

[0050] Preferred amines are primary amines of formula Ra-NH2, where Ra represents a linear or branched alkyl radical containing from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, more preferably from 1 to 8 carbon atoms.

[0051] The amine may for example be chosen, in a non-limiting manner, from methylamine, ethylamine, 1-propanamine, 2-propanamine, 1-butanamine, 2-butanamine, 2-methyl-1-propanamine, 2-methyl-2-propanamine, 1-pentanamine, 3-methyl-butanamine, 1-hexanamine, 4-methyl-2-hexanamine, 1-heptanamine, 1-octanamine, 2-ethyl-1-hexanamine, dimethylamine, 1-tridecanamine, diethylamine and dipropylamine, and their mixture in all proportions.

[0052] Preferably, the amine having a Henry solubility constant strictly less than 20 mol.nr 3 .Pa' 1 present in the composition according to the invention has a flash point greater than or equal to 30°C, preferably greater than or equal to 40°C and more particularly greater than or equal to 50°C.

[0053] Advantageously, the composition comprises n-octylamine, also called 1-octylamine. N-octylamine has a Henry solubility constant of 0.11 mol.nr 3 .Pa' 1 .

[0054] Preferably, the composition comprises from 10 to 60% by weight of the amine relative to the total weight of the composition, more preferably between 15 and 40% by weight.

[0055] The composition according to the invention comprises at least one compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and a pKa strictly greater than 7. This compound has the function of neutralizing the acid(s) present in the condensed water. Preferably, this compound is an amine that is liquid at room temperature and soluble in water.

[0056] Advantageously, the compound has a pKa greater than or equal to 7.5, and more particularly greater than 8.

[0057] Advantageously, the compound has a Henry solubility constant greater than or equal to 30 mol.rrr 3 .Pa' 1 , and more particularly greater than or equal to 50 mol.nr 3 .Pa' 1 , more preferably greater than or equal to 100 mol.nr 3 .Pa' 1 , preferably greater than or equal to 500 mol.rrr 3 .Pa' 1 , still advantageously greater than or equal to 1000 mol.rrr 3 .Pa' 1 .

[0058] Preferably, the compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and a pKa strictly greater than 7 present in the composition according to the invention has a flash point greater than 30°C, preferably greater than 40°C and more particularly greater than 50°C.

[0059] Advantageously, the compound having a Henry solubility constant strictly greater than 20 mol.nr3 .Pa' 1 and having a pKa strictly greater than 7 is an alkanolamine, preferably chosen from monoethanolamine, diethanolamine, triethanolamine, and 1-aminopropanol.

[0060] Advantageously, the composition comprises monoethanolamine.

[0061] Preferably, the composition comprises from 20% to 89.9% by weight of the compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and a pKa strictly greater than 7, relative to the total weight of the composition, and more preferably from 30% to 60% by weight.

[0062] The composition according to the invention comprises at least one sulfur compound.

[0063] The sulfur compound plays the role of corrosion inhibitor. Its presence in the composition according to the invention makes it possible to reinforce its inhibitory properties.

[0064] Preferably, the sulfur compound is chosen from mercapto acids and their salts, for example alkali or ammonium salts, mercapto alcohols, thiols, thio acids, as well as mixtures of two or more of them in all proportions.

[0065] Non-limiting examples of such sulfur compounds are mercaptoethanol, mercaptopropanol, thioglycolic acid, 3-mercaptopropionic acid (MPA), 2-mercaptopropionic acid (or thiolactic acid (ATL), 3,3'-dithiodiproponic acid (DTDP), diammonium dithiodiglycolate (DTDG), sodium thioglycolate, sodium thiosulfate, ethylhexyl thioglycolate, 1,8-dimercapto-3,6-dioxaoctane (DMDO), mercaptoethyl ether, sodium thiosulfite, ammonium thiosulfite, ammonium thiosulfate, potassium thiosulfate, potassium thiosulfite, thiourea, sodium thiocyanate, ammonium thiocyanate, calcium thiocyanate, sodium thioglycolate, ammonium thioglycolate, 1,2-diethylthiourea, propylthiourea, 1,1 -diphenylthiourea, thiocarbanilide, 1,2-dibutylthiourea, dithiourea, thioacetamide, thionicotimide, thiobenzamide, 2-mercaptoethanol, 3-(methylthio)propanal, thioacetic acid, cysteamine, 3-chloro-1-propanethiol, 1-mercapto-2-propanol, 2, 3-dimercapto-1 -propanol, 2-methoxyethanethiol, 3-mercapto-1 -propanol, 2, 3-dimercapto-1 -propanol, 1 -thio-glycerol, 1 ,3-propane-dithiol, mercaptosuccinic acid, cysteine, N-carbomoyl-L-cysteine, N-acetylcysteamine, 4-mercapto-1 -butanol, 1 -butanedithiol, 1 ,4-butanedithiol, 2,2'-thiodietanethiol, 4-cyano-1 -butanethiol, cyclopantanethiol, 1 ,5-pentanedithiol, 2-methyl-1-butanethiol, 2,3,5,6-tetrafluorobenzenethiophenol, 4-chlorothiophenol, 2-mercaptophenol, thiophenol, cyclohexylthiol, 4-mercaptobenzoic acid, thiosalicylic acid, 2-ethylhexanethiol and compounds of formula C n H2n+iSH with n between 1 and 10, limits included.

[0066] Preferably, the sulfur compound present in the composition according to the invention has a flash point greater than or equal to 30°C, preferably greater than or equal to 40°C and more particularly greater than or equal to 50°C.

[0067] Thioglycolic acid is particularly preferred.

[0068] Preferably, the composition according to the invention comprises from 0.1 to 20% by weight of sulfur compound relative to the total weight of the composition, and preferably from 0.1 to 10% by weight.

[0069] The composition according to the present invention may also comprise at least one solvent, generally chosen from water, water-soluble organic solvents and water / water-soluble organic solvent(s) mixtures.

[0070] Among the water-soluble organic solvents, mention may be made of alcohols and ethers in particular, among which alcohols and glycols are preferred, such as, for example, and in a non-limiting manner, those chosen from methanol, ethanol, glycol, monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG), 2-butoxyethanol, and mixtures of two or more of them.

[0071] The composition according to the present invention may comprise one or more additional corrosion inhibitors, i.e. different from the aforementioned sulfur compound.

[0072] The additional inhibitor can be chosen imidazolines and their derivatives, quaternary ammoniums, amphoteric nitrogen compounds, amido-amines, phosphoric esters, carboxylic salts of amines, ethoxylated amides, ethoxylated amines, heterocyclic nitrogen compounds, polyamino acids, polyester amines.

[0073] Preferred are imidazolines originating from the condensation reaction between a fatty acid (or a mixture of fatty acids) of formula RCOOH, where R is a linear or branched alkyl chain comprising from 12 to 22 carbon atoms, and a polyalkylene-polyamine, the carbon number of which can vary from 4 to 20, such as for example DETA (diethylenetriamine), TETA (triethylenetetramine), TEPA (tetraethylenepentamine) or PEHA (pentaethylenehexamine) corresponding to the following formula: R

[0074] Advantageously, the composition comprises an imidazoline as an additional inhibitor.

[0075] The composition according to the invention may comprise from 0.01% to 20% by weight relative to the total weight of the composition of an additional inhibitor. Preferably, the composition according to the invention comprises from 0.10% to 8% by weight relative to the total weight of the composition of an imidazoline.

[0076] The vault corrosion inhibiting compositions according to the present invention can be used in pure form (100% of active materials, i.e. the amine, the neutralizing agent and the sulfur compound) or in diluted form or even in emulsion or suspension, in one or more solvents, as described previously.

[0077] The compositions according to the present invention may further comprise one or more additives, inert with respect to the effectiveness of the vault corrosion inhibitors present in the composition according to the invention.

[0078] Such additives are well known to those skilled in the art, and among these, mention may be made, without limitation, of stabilizers, preservatives, anti-UV agents, flame retardants, solvents, colorants, anti-foam agents, demulsifiers, H2S scavengers, oxygen scavengers, hydrate anti-agglomerants, hydrate kinetic inhibitors, mineral deposit inhibitors and others.

[0079] As indicated above, the composition according to the invention may comprise one or more solvents and / or one or more additives. However, the composition must have a flash point above 60°C, preferably a flash point above 65°C.

[0080] Preferably, the vault corrosion inhibiting composition comprises: - at least one amine with a Henry solubility constant strictly less than 10 mol.nr 3 .Pa' 1 at least one compound having both a Henry solubility constant strictly greater than 50 mol.nr 3 .Pa' 1 , and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and - at least one sulfur compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and more preferably greater than or equal to 70°C.

[0081] More preferably, the vault corrosion inhibiting composition comprises: - at least one amine with a Henry solubility constant strictly less than 5 mol.nr 3 .Pa' 1 , - at least one compound having both a Henry solubility constant strictly greater than 100 mol.nr 3 .Pa' 1 , and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and - at least one sulfur compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and more preferably greater than or equal to 70°C.

[0082] Even more preferably, the vault corrosion inhibiting composition comprises: - at least one amine with a Henry solubility constant strictly less than 1 mol.nr 3 .Pa' 1 , - at least one compound having both a Henry solubility constant strictly greater than 500 mol.nr 3 .Pa' 1 , and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and - at least one sulfur compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and more preferably greater than or equal to 70°C.

[0083] Very advantageously, the vault corrosion inhibiting composition comprises: - at least one amine with a Henry solubility constant strictly less than 1 mol.m Pa' 1 , - at least one compound having both a Henry solubility constant strictly greater than 1000 mol. nr 3 .Pa' 1 and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and - at least one sulfur compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and more preferably greater than or equal to 70°C.

[0084] According to a particular embodiment, the composition according to the invention comprises: - from 10% to 60% by weight relative to the total weight of the composition of an amine having a Henry solubility constant strictly less than 20 mol.nr 3 .Pa' 1 , - from 20% to 89.9% by weight relative to the total weight of the composition of a compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and having a pKa strictly greater than 7, - from 0.1% to 20% by weight relative to the total weight of the composition of a sulfur compound.

[0085] According to a preferred embodiment of the invention, the composition according to the invention comprises: - from 15% to 40% by weight relative to the total weight of the composition of an amine having a Henry solubility constant strictly less than 20 mol.nr 3 .Pa' 1 , - from 30% to 60% by weight relative to the total weight of the composition of a compound having both a Henry solubility constant strictly greater than 20 mol.m Pa' 1 and having a pKa strictly greater than 7, - from 0.1% to 10% by weight relative to the total weight of the composition of a sulfur compound.

[0086] According to a preferred embodiment of the invention, the composition according to the invention comprises: - from 15% to 40% by weight relative to the total weight of the n-octylamine composition, - from 30% to 60% by weight relative to the total weight of the monoethanolamine composition, - from 0.1 to 10% by weight relative to the total weight of the thioglycolic acid composition.

[0087] The compositions according to the invention can be prepared by any known means, and in general by simple mixing of the various components of the composition according to the invention, in any order. However, it is preferred to mix, with stirring, the amine(s) and the compound(s) having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and a pKa strictly greater than 7 and the sulfur compound(s), then possibly the additives.

[0088] The composition according to the invention can be used in the field of protection against the roof corrosion of hydrocarbon pipes, in which liquid and / or gaseous hydrocarbons circulate, such as gases, gas condensates, crude oil, alone or in a mixture. The use of the compositions according to the invention for inhibiting the roof corrosion of said pipes thus forms another subject of the present invention.

[0089] These compositions can be injected according to any methods well known to those skilled in the art, continuously or in batch, preferably continuously, into the extraction lines of said hydrocarbons, or into the injection lines of production water, and generally into any aqueous, organic or hydro-organic fluid used in hydrocarbon extraction fields. For example, these compositions can also be injected via the so-called "gas-lift" system, well known to those skilled in the art.

[0090] The inhibitor compositions are used, preferably in continuous treatment, at a rate of 10 ppm to 10,000 ppm by volume of corrosion inhibitor composition for a part by volume of fluids circulating in the pipe.

[0091] According to another object, the present invention relates to a method for inhibiting the corrosion of a vault of a pipe, said method comprising at least one step of continuous or batch introduction, preferably continuous, into said pipe, in which fluids circulate, in particular liquid and / or gaseous hydrocarbons, preferably gases, gas condensates, crude oil, alone or in a mixture of at least one corrosion inhibiting composition as defined above.

[0092] Preferably, the corrosion inhibiting composition is used to treat hydrocarbon transport lines, in other words, lines in which hydrocarbons flow. Thus, the composition can be introduced at the start of the line, to treat the entire pipeline or the first sections of the line. It is also possible to treat one or more sections of the pipeline locally. In this case, the treatment can only be done locally on the sections to be treated.

[0093] In the method of the invention, the inhibiting compositions are injected, preferably in continuous treatment, at a rate of 10 ppm to 10,000 ppm, by volume of corrosion inhibiting composition for a part by volume of fluids circulating in the pipe.

[0094] The method according to the present invention, which is a chemical treatment using at least one composition inhibiting vault corrosion as defined above, may also comprise the implementation of one or more physical treatments, in particular using scrapers, as described for example in patent application FR2791695.

[0095] Another aspect of the present invention is embodied by the use of at least one composition inhibiting the corrosion of the vault of hydrocarbon pipes used in the extraction of gas and / or oil, said at least one composition being as defined above in the present description, with one or more physical (i.e. mechanical) treatments, such as for example treatments using scrapers, and others.

[0096] The following examples illustrate the present invention, but are in no way limiting. Examples Preparation of the compositions

[0097] The following compositions were prepared by mixing the reagents in the proportions shown in Table 1 below. Compositions 1 and 2 are comparative compositions. Composition 3 is a composition according to the invention. - Table 1 - * The values ​​of Henry's solubility constants are taken from the article Atmos. Chem. Phys., 15, (2015), pp. 4399-4981, “Compilation of Henry's law constants (version 4.0) for water as solvent”, by R. Sander. < 1 * Imidazoline is supplied by Arkema under the name NORUST 900 C.

[0098] The flash points of the compositions are determined by applying the ISO 3679-2015 standard, using the closed cup method. The results are reported in Table 2 below: - Table 2 --

[0099] Composition 3 is indeed a composition according to the invention. Composition 2 has a flash point which is not compatible with the intended uses. Evaluation of anti-corrosion properties of compositions

[0100] The effectiveness of the "Top of Line" anti-corrosion formulas is achieved in a glass reactor with a total volume of 1 L. It contains 700 mL of an acidic salt water solution (NaCl 1 gL' 1 + 1000 mg.L 1 glacial acetic acid). The reactor is equipped with a coolant. Continuous bubbling of CO2 is carried out using a submerged frit.

[0101] The temperature of the liquid is brought to 80°C by circulating water in the reactor jacket. The solution is stirred using a magnetic bar rotating at a speed of 300 rpm. min -1 . A cylindrical, 3.5 cm, unalloyed steel (UNS G10180) coupon 2of total surface area, is placed in the gas phase at a distance of at least 5 cm above the liquid in order to avoid liquid splashes. It is previously polished to SiC600 grade, rinsed then dried with acetone and then weighed to 10 e to within mg.

[0102] Under these operating conditions, drops of condensed water form on the surface of the metal coupon. The condensation rate is estimated to be between 0.5 mL.rrr 2 .s' 1 and 0.7 mL.m' 2 .s' 1 based on the number of droplets that fall back into the solution in a given time.

[0103] The solution as it has a pH = 3.2 at room temperature. The amount of anti-corrosion composition injected is done in such a way that a partial neutralization takes place up to a pH of 5.6.

[0104] After 48 hours of exposure to the gas phase of the reactor, the metal coupon is removed, rinsed with water, stripped, dried and then weighed.

[0105] The corrosion rate noted v and expressed in mm / year is calculated using the following formula: A mass v = - density x area of ​​V sample x test duration Or Mass represents the initial mass of the sample (coupon) - mass of the sample (coupon) after the corrosion test, the density of the tested sample is 7.89 g. cm' 3 , the sample area is 3.52 cm 2 .

[0106] The results are reported in Table 3 below: - Table 3 -

[0107] It is found that the composition according to the invention leads to a very significantly reduced corrosion rate.

Claims

CLAIMS 1. Vault corrosion inhibiting composition comprising: - at least one amine with a Henry solubility constant strictly less than 20 mol.rrr 3 .Pa' 1 , preferably less than 10 mol.nr 3 .Pa' 1 and more particularly, less than or equal to 5 mol.nr 3 .Pa' 1 , better less than or equal to 1 mol.m^.Pa -1 , - at least one compound having both a Henry solubility constant strictly greater than 20 mol.m Pa' 1 , preferably greater than or equal to 30 mol.rrr 3 .Pa' 1 , and more particularly greater than or equal to 50 mol.nr 3 .Pa' 1 , more preferably greater than or equal to 100 mol.nr 3 .Pa' 1 , preferably greater than or equal to 500 mol.nr 3 .Pa' 1 , still advantageously greater than or equal to 1000 mol.rrr 3.Pa' 1 and a pKa strictly greater than 7, preferably greater than or equal to 7.5, and more particularly greater than 8, and - at least one sulfur compound, and the composition having a flash point greater than or equal to 60°C, preferably strictly greater than 60°C, and more preferably greater than or equal to 70°C.

2. Composition according to claim 1, characterized in that the amine is chosen from methylamine, ethylamine, 1-propanamine, 2-propanamine, 1-butanamine, 2-butanamine, 2-methyl-1-propanamine, 2-methyl-2-propanamine, 1-pentanamine, 3-methyl-butanamine, 1-hexanamine, 4-methyl-2-hexanamine, 1-heptanamine, 1-octanamine, 2-ethyl-1-hexanamine, dimethylamine, 1-tridecanamine, diethylamine and dipropylamine and their mixture.

3. Composition according to claim 1 or 2, characterized in that the compound having both a Henry solubility constant strictly greater than 20 mol.m Pa' 1 and a pKa strictly greater than 7 is chosen from monoethanolamine, diethanolamine, triethanolamine, and 1-aminopropanol.

4. Composition according to any one of the preceding claims, characterized in that the sulfur compound is chosen from mercaptoethanol, mercaptopropanol, thioglycolic acid, 3-mercaptopropionic acid (AMP), 2-mercaptopropionic acid (or thiolactic acid (ATL), 3,3'-dithiodiproponic acid (DTDP), dithiodiglycolate diammonium (DTDG), sodium thioglycolate, sodium thiosulfate, ethylhexyl thioglycolate, , 1,8-dimercapto-3,6-dioxaoctane (DMDO), mercaptoethyl ether, sodium thiosulfite, ammonium thiosulfite, ammonium thiosulfate, potassium thiosulfate, potassium thiosulfite, thiourea, sodium thiocyanate, ammonium thiocyanate, calcium thiocyanate, sodium thioglycolate, ammonium thioglycolate, 1,2-diethylthiourea, propylthiourea, 1,1-diphenylthiourea, thiocarbanilide, 1,2-dibutylthiourea, dithiourea, thioacetamide, thionicotimide, thiobenzamide, 2-mercaptoethanol, 3-(methylthio)propanal, thioacetic acid, cysteamine, 3-chloro-1-propanethiol, 1-mercapto-2-propanol, 2, 3-dimercapto-1-propanol, 2-methoxyethanethiol, 3-mercapto-1-propanol, 2, 3-dimercapto-1-propanol, 1-thioglycerol, 1,3-propanedithiol, mercaptosuccinic acid, cysteine,N-carbomoyl-L-cysteine, N-acetylcysteamine, 4-mercapto-1-butanol, 1-butanedithiol, 1,4-butanedithiol, 2,2'-thiodietanethiol, 4-cyano-1-butanethiol, cyclopantanethiol, 1,5-pentanedithiol, 2-methyl-1-butanethiol, 2,3,5,6-tetrafluorobenzenethiophenol, 4-chlorothiophenol, 2-mercaptophenol, thiophenol, cyclohexylthiol, 4-mercaptobenzoic acid, thiosalicylic acid, 2-ethylhexanethiol and compounds of formula C, n H2n+iSH with n between 1 and 10, limits included.

5. Composition according to any one of the preceding claims, characterized in that it comprises: - from 10% to 60% by weight relative to the total weight of the composition of an amine having a Henry solubility constant strictly less than 20 mol.nr 3 .Pa' 1 , - from 20% to 89.9% by weight relative to the total weight of the composition of a compound having both a Henry solubility constant strictly greater than 20 mol.nr 3 .Pa' 1 and having a pKa strictly greater than 7, - from 0.1% to 20% by weight relative to the total weight of the composition of a sulfur compound.

6. Composition according to any one of the preceding claims, characterized in that it comprises at least one imidazoline.

7. Use of an inhibiting composition as defined in any one of the preceding claims, for inhibiting the corrosion of the vault of hydrocarbon pipes in which fluids, in particular hydrocarbons, circulate. liquids and / or gases, preferably gases, gas condensates, crude oil, alone or in mixture.

8. Use according to claim 7, in which the inhibiting composition is injected, preferably continuously, at a rate of 10 ppm to 10,000 ppm by volume of corrosion inhibiting composition for a part by volume of fluids circulating in the pipe.

9. Method for inhibiting the corrosion of the vault of a pipe, characterized in that it comprises at least one step of continuous or batch introduction, preferably continuous, into said pipe in which fluids circulate, in particular liquid and / or gaseous hydrocarbons, preferably gases, gas condensates, crude oil, alone or in a mixture, of at least one corrosion inhibiting composition as defined in any one of claims 1 to 6.

10. Method according to claim 9, characterized in that the composition as defined in any one of claims 1 to 6 is injected at a rate of 10 ppm to 10,000 ppm by volume of composition for a part by volume of fluids circulating in said pipe.

11. Method according to claim 9 or claim 10, characterized in that it comprises one or more physical treatment steps, in particular using scrapers.

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