Synergistic corrosion inhibitor compositions and methods

Abstract

Corrosion inhibitor compositions including an alkoxylated polyamine and an imidazoline. The alkoxylated polyamine may be derived from aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), or tetraethylenepentamine (TEPA). The imidazoline is typically derived from tall oil fatty acid (TOFA). The composition provides effective corrosion inhibition when present at 5 to 100 ppm in a corrosive medium. Methods of inhibiting corrosion of a metal substrate in contact with a carbon dioxide-containing corrosive medium using the composition are also disclosed, as well as systems for inhibiting corrosion in oil and gas production processes incorporating the composition.

Description

SYNERGISTIC CORROSION INHIBITOR COMPOSITIONS AND METHODS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 743,518, filed January 9, 2025, the entirety of which is incorporated by reference herein.TECHNICAL FIELD

[0002] The present disclosure relates to corrosion inhibitor compositions, and more particularly to synergistic blends of a first co-inhibitor and a second co-inhibitor, one of which is an imidazoline, for inhibiting carbon dioxide corrosion in oil and gas production processes.BACKGROUND

[0003] Corrosion is a serious concern in the oil and gas field processes, especially because nearly 80% of the materials used is carbon steel, which exhibits very poor corrosion resistance in most operating conditions. Often, the corrosion could be due to dissolved gases such as carbon dioxide (sweet corrosion) or hydrogen sulfide (sour corrosion). Another serious corrosion-enhancer is the salt concentrations in the water that is co-produced with the oil and gas. Those corrosion problems are also often carried over all the way to downstream processes, such as in refineries.

[0004] While corrosion can take several forms, it is usually confined to the metal surface. As a result, most conventional corrosion inhibitors act by forming a protective layer on the metal substrate. Historically, nitrogen-containing compounds, such as amines (US 7,468,158), alkoxylated amines (WO 2024 / 030283), amidoamines, imidazolines (US 5,300,235) and quaternary ammonium compounds have been used for corrosion inhibitor formulations used in various kinds of systems. Among those nitrogen-based inhibitors, the imidazolines have been some of the most widely used in the oil and gas field, especially the ones made by the condensation of Tall Oil Fatty Acids (TOFA) and diethylenetriamine (DETA). Recently, TOFA availability and increasing cost have raised significant concerns. Therefore, there is a need for new corrosion inhibitor compositions offering similar or better performances but at a reduced cost.SUMMARY

[0005] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended toidentify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0006] According to an aspect of the present disclosure, a corrosion inhibitor composition is provided. The corrosion inhibitor composition includes an alkoxylated polyamine and an imidazoline.

[0007] According to other aspects of the present disclosure, the corrosion inhibitor composition may include one or more of the following features. The alkoxylated polyamine may be derived from a polyamine, such as aminoethylethanolamine ( AEEA). The alkoxylated polyamine may be an alkoxylated polyethyleneamine. The alkoxylated polyamine may be an alkoxylated polyethyleneamine derived from a polyethyleneamine selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).10008] The alkoxylated polyamine may be an alkoxylated polyethyleneamine having the formula:wherein Ri, R2, R3, R4, Rs, Re, R?, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49.

[0009] The imidazoline may have the formula:wherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10. The imidazoline may be derived from tall oil fatty acid (TOFA). The composition may provide corrosion inhibition when present in a concentration of 5 to 100 ppm in a corrosive medium.

[0010] According to another aspect of the present disclosure, a method of inhibiting corrosion of a metal substrate in contact with a corrosive medium containing carbon dioxide isprovided. The method includes adding to the corrosive medium an effective amount of a corrosion inhibitor composition comprising an alkoxylated polyamine and an imidazoline, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

[0011] According to other aspects of the present disclosure, the method may include one or more of the following features. The alkoxylated poly amine may be an alkoxylated polyethyleneamine having the formula:fr- N-Vwherein Ri, R2, Rs, R4, Rs, Re, R7, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49. The alkoxylated polyamine may be derived from a polyamine, such as aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The alkoxylated polyamine may be an alkoxylated polyethyleneamine derived from a polyethyleneamine selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

[0012] The imidazoline may have the formula:wherein R9 contains at least 12 carbon atoms and in is an integer from 0 to 10.

[0013] The imidazoline may have the formula:wherein R9 contains 18 to 60 carbon atoms and m is an integer from 0 to 3. The effective amount of the corrosion inhibitor composition may be 5 to 100 ppm in the corrosive medium. The effective amount of the corrosion inhibitor composition may be 15 to 25 ppm in the corrosive medium.

[0014] According to another aspect of the present disclosure, a system for inhibiting corrosion in an oil and gas production process is provided. The system includes a metal substrate, a corrosive medium containing carbon dioxide in contact with the metal substrate, and a corrosion inhibitor composition comprising an alkoxylated polyamine and an imidazoline, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

[0015] According to other aspects of the present disclosure, the system may include one or more of the following features. The alkoxylated polyamine may be derived from a polyamine, such as aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The alkoxylated polyamine may be an alkoxylated polyethyleneamine having the formula:A.°A■'e 'Hwherein Ri, R2, R3, Ri, R5, Re, R7, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49. The alkoxylated polyamine may be an alkoxylated polyethyleneamine derived from a polyethyleneamine selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

[0016] The imidazoline may have the formula:wherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10.

[0017] The imidazoline may have the formula:wherein R9 contains 18 to 60 carbon atoms and m is an integer from 0 to 3. The corrosion inhibitor composition may be present in the corrosive medium in a concentration of 5 to 100 ppm.

[0018] The foregoing general description of the illustrative embodiments and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.DETAILED DESCRIPTION

[0019] For purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the disclosure is intended by the illustration and description of certain embodiments of the disclosure. In addition, any alterations and / or modifications of the illustrated and / or described embodiment(s) are contemplated as being within the scope of the present disclosure. Further, any other applications of the principles of the disclosure, as illustrated and / or described herein, as would normally occur to one skilled in the art to which the disclosure pertains, are contemplated as being within the scope of the present disclosure.

[0020] The following description sets forth exemplary aspects of the present di sclosure. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure. Rather, the description also encompasses combinations and modifications to those exemplary aspects described herein.

[0021] As used herein, the term “amine” refers to a class of organic compounds containing one or more nitrogen atoms with a lone pair of electrons. An amine is a compound or functionalgroup derived from ammonia (NH₃), where one or more hydrogen atoms may be replaced by organic or inorganic substituents. Amines include primary amines (R-NH₂), secondary amines (R₂-NH), and tertiary amines (R₃-N), where R represents an alkyl, aryl, or other substituent group. Unless otherwise specified, the term “amine” encompasses both aliphatic and aromatic amines, including those that are substituted or part of a larger molecular structure. Examples of amines include polyamines (e.g., polyethyleneamines) and their alkoxylated derivatives used as components in corrosion inhibitor compositions. These amines may contain primary, secondary, and / or tertiary amine groups, and may be linear or branched. The amine compounds in this invention are capable of interacting with metal surfaces and / or imidazoline compounds to provide corrosion inhibition effects in carbon dioxide-containing environments.

[0022] As used herein, the term “aikoxyiated amine” refers to an amine compound that has been modified by the addition of one or more alkoxy groups, typically ethoxy (derived from ethylene oxide (EO)) and / or propoxy (derived from propylene oxide (PO)) groups. In an alkoxylated amine, alkoxy groups (-R-O-) are introduced onto the nitrogen atom(s) of the amine. The amine may be a primary, secondary, or tertiary amine, and the degree of alkoxylation can vary based on the number of alkylene oxide units added. Unless otherwise specified, the term encompasses both linear and branched alkoxylated amines, as well as mixtures thereof. Examples of alkoxylated amines include alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) with a defined molecular structure as represented by Formula I. The alkoxy groups modify the properties of the amine, such as its solubility and surface activity, which can affect its performance as a corrosion inhibitor.

[0023] As used herein, the term “polyamine” refers to an organic compound containing two or more primary (-NH₂-), secondary (-NH-), or tertiary (-N-) amine groups. Polyamines may have a linear, branched, or cyclic structure, and the amine groups can be connected through alkyl, aryl, or other organic linkages. Unless otherwise specified, the term polyamine encompasses both aliphatic and aromatic polyamines, as well as substituted or unsubstituted polyamines, where the substituents do not interfere with the functionality of the amine groups. Examples of polyamines include aminoethylethanolamine (AEEA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). These polyamines can serve as precursors for the alkoxylated polyamines used in the corrosion inhibitor compositions. Polyamines such as DETA, TETA, and TEPA are examples of polyethyleneamines, which can serve as precursors for alkoxylated polyethyleneamines used in the corrosion inhibitor compositions. The multiple amine groups in polyamines enable themto form complex structures with metal ions and adsorb onto metal surfaces, contributing to their corrosion inhibition properties.

[0024] As used herein, the term “alkoxylated polyamine” refers to a polyamine compound that has been modified by the addition of one or more alkoxy groups. The alkoxy groups are typically ethoxy (derived from ethylene oxide (EO)) or propoxy (derived from propylene oxide (PO)) units, or combinations thereof. The polyamine framework may be a linear or branched structure containing two or more amine groups. Examples include aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), or tetraethylenepentamine (TEPA). The alkoxylation process involves the reaction of these amine groups with alkylene oxides (e.g., ethylene oxide (EO), propylene oxide (PO)), resulting in the attachment of hydroxyalkyl chains to the nitrogen atoms. The polyamine may be linear, branched, or cyclic and can include primary, secondary, or tertiary amine groups. The degree of alkoxylation can vary depending on the number of alkylene oxide units reacted, typically ranging from 1 to 100 alkoxy units per reactive site on the polyamine. Unless otherwise specified, the term encompasses partially and fully alkoxylated polyamines, as well as mixtures of such compounds. In some cases, alkoxylated polyamines serve as key components in synergistic corrosion inhibitor compositions, particularly for inhibiting carbon dioxide-induced corrosion in oil and gas production processes.

[0025] As used herein, the term “polyethyleneamine” refers to a specific class of polyamines characterized by a linear chain of ethylene units (-CH2CH2-) connecting two or more amine groups. In other words, polyethyleneamines are polyamines containing repeating ethyleneamine units (-CH2CH2NH-). Polyethyleneamines may include linear or branched structures and may have varying chain lengths, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), and higher oligomers or polymers. Unless otherwise specified, the term encompasses both substituted and unsubstituted polyethyleneamines, where the substituents do not interfere with the amine functionality, as well as mixtures of different polyethyleneamines. Examples include ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). In some cases, polyethyleneamines serve as the base compounds for alkoxylation reactions to produce the alkoxylated polyethyleneamine components of the corrosion inhibitor compositions.

[0026] As used herein, the term “alkoxylated polyethyleneamine” refers to a compound derived from a polyethyleneamine by the addition of one or more alkoxy groups. Alkoxylatedpolyethyleneamine can be obtained by reacting a polyethyleneamine with one or more alkylene oxides, such as ethylene oxide (EO), propylene oxide (PO), or their mixtures. The polyethyleneamine backbone typically consists of repeating ethylene units (-CH2CH2-) connecting two or more amine groups. The alkoxy groups may be ethoxy (-CH2CH2O-) or propoxy (-CH(CH3)CH2O~) units, or combinations thereof, attached to the nitrogen atoms of the polyethyleneamine. The degree of alkoxylation can vary, resulting in partially or fully alkoxylated products. In some cases, the total number of alkoxy units (b+c+d+e) is on average at least 30 and less than 49. The alkoxylated polyethyleneamine may have a structure represented by Formula I, where the variables Ri through Rs, a, b, c, d, and e define the specific arrangement and number of ethylene and alkoxy units. Unless otherwise specified, the term encompasses linear, branched, and cyclic alkoxylated polyethyleneamines, as well as mixtures of such compounds. In some cases, these compounds serve as key components in the corrosion inhibitor compositions, contributing to the formation of protective films on metal surfaces in carbon dioxide-containing environments.

[0027] As used herein, the term “imidazoline” refers to a class of heterocyclic organic compounds containing a five-membered ring with two nitrogen atoms. Imidazolines are derivatives of imidazole, in which one of the double bonds in the ring is saturated. In some cases, imidazolines may be corrosion inhibitor compounds derived from the condensation of fatty acids, particularly tall oil fatty acids (TOFA), with polyamines such as aminoethylethanolamine (AEEA), diethylenetriamine (DETA), triethylenetetramine (TETA) or tetraethylenepentamine (TEPA). These imidazolines have the general formula CsHsN?, with substituents optionally attached to the ring structure at one or more positions. Imidazolines may include 2 -imidazoline, 4-imidazoline, and their substituted derivatives, and unless otherwise specified, the term encompasses both unsubstituted and substituted forms. Substituents may include alkyl, aryl, or other functional groups that do not interfere with the characteristic imidazoline ring structure. In some cases, imidazolines serve as a key component in synergistic corrosion inhibitor compositions, particularly for inhibiting carbon dioxide-induced corrosion in oil and gas production processes.

[0028] The present disclosure relates to corrosion inhibitor compositions for protecting metal substrates from corrosion, particularly in oil and gas production processes. In some cases, the corrosion inhibitor compositions may include a synergistic blend of a plurality of coinhibitors, such as a first co-inhibitor and a second co-inhibitor, one of which may be an imidazoline. For example, the first co-inhibitor may be an imidazoline, and the second co-inhibitor may be an amine. In some cases, the corrosion inhibitor compositions may include a synergistic blend of an amine and an imidazoline. In some cases, the corrosion inhibitor compositions may include a synergistic blend of a polyamine and an imidazoline. In some cases, the corrosion inhibitor compositions may include a synergistic blend of an alkoxylated polyamine and an imidazoline. In some cases, the corrosion inhibitor compositions may include a synergistic blend of an alkoxylated polyethyleneamine and an imidazoline. These compositions may provide enhanced corrosion protection compared to the individual components used separately tested in similar conditions, such as in carbon dioxide saturated brine. These compositions may be highly effective for protection of ferrous metals against attack by a corrosive environment, such as brine saturated with carbon dioxide. In some cases, the same or lesser amount of imidazoline when mixed with the second co-inhibitor (e.g., alkoxylated polyamine) provides the same or enhanced corrosion protection of a metal substrate.

[0029] In some cases, the corrosion inhibitor compositions may be used in systems for inhibiting corrosion in oil and gas production processes. Such systems may include a metal substrate in contact with a corrosive medium containing carbon dioxide. The corrosion inhibitor composition may be added to the corrosive medium to protect the metal substrate from corrosion,

[0030] The alkoxylated polyamines used in the corrosion inhibitor compositions may be derived from various polyamines and alkoxylated with ethylene oxide, propylene oxide, or combinations thereof. Similarly, the alkoxylated polyethyleneamines used in the corrosion inhibitor compositions may be derived from various polyethyleneamines and alkoxylated with ethylene oxide, propylene oxide, or combinations thereof. The imidazolines may be derived from fatty acids and polyamines or polyethyleneamines. The specific structures and ratios of these components may be varied to optimize corrosion protection performance.

[0031] In some cases, the corrosion inhibitor compositions may provide effective corrosion protection at relatively low concentrations in the corrosive medium. The compositions may be particularly effective for inhibiting corrosion caused by carbon dioxide in aqueous environments typical of oil and gas production processes.

[0032] In some cases, the corrosion inhibitor compositions may include alkoxylated polyamines. In some cases, an alkoxylated polyamine may have at least one ethylene oxide unit. In some cases, an alkoxylated polyamine may have at least one propylene oxide unit. Insome cases, an alkoxylated polyamine may have at least one ethylene oxide unit and at least one propylene oxide unit.

[0033] The alkoxylated polyamines may be derived from various polyamines. In some cases, the polyamine may be aminoethylethanolamine (AEEA).

[0034] In some cases, the alkoxylated polyamines may be reaction products of propylene oxide and / or ethylene oxide with amines, such as AEEA.

[0035] The alkoxylated polyamine may include, without limitation, homopolymers, and both random and block co-polymers of any one or more of the following (either alone or mixed with one another in any proportion): oxyethylene units and oxypropylene units.

[0036] The alkoxylation of the polyamines may involve the addition of ethylene oxide (EO) and / or propylene oxide (PO) units. In some cases, different ratios of EO to PO may be used in the alkoxylation process. For example, the ratio of EO to PO may range from 1:10 to 10:1.

[0037] The order of alkoxylation may be varied. In some cases, PO units may be added first, followed by EO units. In other cases, EO units may be added first, followed by PO units. Alternatively, EO and PO units may be added simultaneously or in alternating sequences.

[0038] Specific examples of alkoxylated polyamines that may be used in the corrosion inhibitor compositions include, but are not limited to: monoalkoxylated AEEA with an EO to PO ratio of 1:0 to 0:1 (e.g., N-(2-Hydroxyethyl)-N-(2-ethoxyethyl)ethylenediamine); polyalkoxylated AEEA with an EO to PO ratio of 2:0 to 4:0 or 2:2 (e.g., Triethoxylated AEEA); mixed alkoxylated AEEA with an EO to PO ratio of 2:1, 3:2, or 1:1 (e.g., Ethoxy-propoxy AEEA); highly alkoxylated AEEA with an EO to PO ratio of 5:2, 6:3, or higher (e.g., AEEA with EO: PO ratio of 5:3); or branched alkoxylated AEEA with an EO to PO ratio of 3:2, 4:1, etc. (e.g., Branched triethoxylated AEEA).

[0039] The specific alkoxylated polyamine used and its degree of alkoxylation may be selected based on the desired properties of the corrosion inhibitor composition and the speci fic corrosive environment in which the composition may be used.

[0040] In some cases, the corrosion inhibitor compositions may include alkoxylated polyethyleneamines. The alkoxylated polyethyleneamines may have the general structure represented by Formula 1:

[0041] In Formula I, Ri, R2, R3, R4, R5, Re, R7, and Rs may each independently be hydrogen or methyl. In some cases, Ri, R2, R3, R4, Rs, Re, R7, and Rs may each be hydrogen. In some cases, at least one of Ri or R2 is hydrogen, and each Ri and R? is independently selected in subunit. In some cases, at least one of R3 or R4 is hydrogen, and each R3 or R.: is independently selected in subunit. In some cases, at least one of Rs or Re is hydrogen, and each Rs or Re is independently selected in subunit. In some cases, at least one ofR? or Rg is hydrogen, and each R7 or Rg is independently selected in subunit. For example, R2, R4, Re, and Rg may each be hydrogen, and Ri, R3, Rs, and R? may each be either hydrogen or methyl. For example, Ri, R3, Rs, and R7 may each be hydrogen, and R2, R4, Re, and Rs may each be either hydrogen or methyl.

[0042] In some cases, Formula I may provide an alkoxylated polyethyleneamine with at least one ethylene oxide unit. In some cases, Formula I may provide an alkoxylated polyethyleneamine with at least one propylene oxide unit. In some cases, Formula I may provide an alkoxylated polyethyleneamine with at least one ethylene oxide unit and at least one propylene oxide unit.

[0043] The variable ‘a’ in Formula I may be an integer from 1 to 10. In some cases, ‘a’ may be an integer from 2 to 5.

[0044] The variables b, c, d, and e in Formula I may each independently be integers on average of 15 or less. In some cases, the sum of b, c, d, and e (b+c+d+e) may be on average at least 30 and less than 49.

[0045] The alkoxylated polyethyleneamines may be derived from various polyethyleneamines. In some cases, the polyethyleneamine may be selected from ethylenediamine (EDA), diethylenetriamine (DETA), triethyl enetetramine (TETA), and tetraethylenepentamine ( TEPA).

[0046] In some cases, the alkoxylated polyethyleneamines may be reaction products of propylene oxide and / or ethylene oxide with ethyleneamines, such as EDA, DETA, TETA, or TEPA.

[0047] The alkoxylated polyethyleneamine of formula (I) may include, without limitation, homopolymers, and both random and block co-polymers of any one or more of the following (either alone or mixed with one another in any proportion): oxyethylene units and oxypropylene units.

[0048] The alkoxylation of the polyethyleneamines may involve the addition of ethylene oxide (EO) and / or propylene oxide (PO) units. In some cases, different ratios of EO to PO may be used in the alkoxylation process. For example, the ratio of EO to PO may range from 1:10 to 10:1.

[0049] The order of alkoxylation may be varied. In some cases, PO units may be added first, followed by EO units. In other cases, EO units may be added first, followed by PO units. Alternatively, EO and PO units may be added simultaneously or in alternating sequences.

[0050] Specific examples of alkoxylated polyethyleneamines that may be used in the corrosion inhibitor compositions include, but are not limited to:

[0051] 1. TETA-6EO-30PO: An alkoxylated triethylenetetramine with 6 ethylene oxide units and 30 propylene oxide units.

[0052] 2. TEPA-7EO-40PO: An alkoxylated tetraethylenepentamine with 7 ethylene oxide units and 40 propylene oxide units.

[0053] 3. TETA-30PO-6EO: An alkoxylated tri ethylenetetramine with 30 propylene oxide units and 6 ethylene oxide units.

[0054] 4. TETA-30PO: An alkoxylated triethylenetetramine with 30 propylene oxide units added.

[0055] The specific alkoxylated polyethyleneamine used and its degree of alkoxylation may be selected based on the desired properties of the corrosion inhibitor composition and the specific corrosive environment in which the composition may be used.

[0056] For additional details regarding polyethyleneamine alkoxylate corrosion inhibitors, reference is made to WO 2024030283 Al, entitled “Polyethyleneamine Alkoxylate Corrosion Inhibitors,” which is hereby incorporated by reference in its entirety. The teachings of WO 2024030283 Al may complement the present disclosure, particularly with respect to the preparation, structural variations, and properties of alkoxylated polyethyleneamines suitable for corrosion inhibition.

[0057] In some cases, the corrosion inhibitor compositions may include imidazolines. The imidazolines may have the general structure represented by Formula II: / ! H IKN / '"• N I " XU \NN

[0058] In Formula II, R9 may contain at least 12 carbon atoms. In some cases, R9 may contain 18 to 60 carbon atoms. In some cases, R9 does not exceed 60 carbon atoms. The variable ‘m’ in Formula II may be an integer from 0 to 10. In some cases, ‘m’ may be an integer from 0 to 3.

[0059] The imidazolines may be derived from various fatty acids and polyamines or polyethyleneamines. In some cases, the imidazolines are condensation products of fatty acids and polyamines or polyethyleneamines. The fatty acids may contain aliphatic, aromatic, or cyclic groups and may be linear, branched, saturated, or unsaturated. In some cases, the fatty acids are linear fatty acids, which are either saturated or unsaturated. In some cases, the imidazoline may be derived from tall oil fatty acid (TOFA). A specific example of a TOFA-based imidazoline that may be used in the corrosion inhibitor compositions is SURFONIC® OFC 100 (“OFC 100”), which is a 1:1 TOFA / DETA (diethylenetriamine) imidazoline. In some cases, TOFA / AEEA may be used in the corrosion inhibitor compositions.

[0060] In some cases, ethoxylated versions of imidazolines may be used in the corrosion inhibitor compositions. Examples of ethoxylated imidazolines include OC 105 and OC 110, which are 5-mole and 10-mole ethoxylates of the TOFA / DETA imidazoline, respectively. In some cases, ethoxylates of TOFA / AEEA may be used in the corrosion inhibitor compositions.

[0061] The corrosion inhibitor compositions may also include other types of imidazolines or related compounds. In some cases, bis-imidazolines or tri-imidazolines may be used instead of or in addition to the imidazoline represented by Formula II. These multi-imidazoline compounds may provide additional corrosion protection or modify the properties of the corrosion inhibitor composition.

[0062] In some cases, amides or polyamides may be used instead of or in addition to the imidazoline in the corrosion inhibitor compositions. These compounds may be derived from similar fatty acids and amines as the imidazolines and may contribute to the overall corrosion protection performance of the composition.

[0063] The specific imidazoline or combination of imidazolines and related compounds used in the corrosion inhibitor composition may be selected based on the desired properties ofthe composition and the specific corrosive environment in which the composition may be used. The ratio of imidazoline to alkoxylated polyamine or alkoxylated polyethyleneamine in the composition may be adjusted to optimize corrosion protection performance.

[0064] The corrosion inhibitor compositions of the present disclosure exhibit unexpected synergistic effects that may be attributed to the emulsification properties of the imidazoline component, such as OFC 100 (a TOFA / DETA imidazoline product). It is hypothesized that the imidazoline may act as an emulsifier, facilitating the partitioning of the alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) between the oil and water phases in the biphasic system typically encountered in oil and gas applications.

[0065] The imidazoline component is believed to migrate to the water phase, effectively “pulling” the alkoxylated polyamine (e.g., alkoxylated polyethyleneamine) along with it. This emulsification effect appears to be crucial for the formation of a protective film on the metal surface. It is proposed that the imidazoline forms a primary layer on the metal substrate, while the alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) form a secondary layer on top of this primary layer. This dual-layer structure may contribute to the enhanced corrosion protection observed in the inventive compositions.

[0066] The synergistic effect between the imidazoline and alkoxylated polyamine (e.g., alkoxylated polyethyleneamine) components is particularly noteworthy. While the alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) demonstrated poor performance as corrosion inhibitors when used alone, their effectiveness is significantly enhanced when combined with the imidazoline component. This synergy is believed to be a direct result of the emulsification properties of the imidazoline, which enables the alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) to effectively contribute to corrosion inhibition in the biphasic system.

[0067] It is important to note that the water solubility of the imidazoline component, such as OFC100, is relatively low. To address this, the formulations of the present invention typically include an acid component to increase the water solubility of the imidazoline. This suggests that the emulsification properties of the imidazoline, and consequently the overall performance of the corrosion inhibitor composition, may be pH-dependent or enhanced under acidic conditions. The acid component thus may play a crucial role in optimizing the performance of the inventive compositions in real-world applications.

[0068] An acid, such as glacial acetic acid, may be used to increase the solubility of the imidazoline component, such as OFC 100. Glacial acetic acid can protonate the nitrogen atomsin the imidazoline structure, thereby increasing its water solubility. The protonation of the imidazoline ring creates a positive charge, making the molecule more hydrophilic and thus more soluble in the aqueous phase of the biphasic system. Glacial acetic acid is considered a relatively weak acid, which helps maintain a mildly acidic environment without causing excessive corrosion itself. Glacial acetic acid is compatible with the other components of the corrosion inhibitor formulation. Glacial acetic acid is readily available and cost-effective for industrial applications. The volatility of glacial acetic acid may allow for potential pH adjustment in the system over time, which may be beneficial for long-term corrosion protection. A stoichiometric amount of glacial acetic acid may be used, such that the amount is carefully calculated to neutralize the basic amine groups present in the inhibitor components. The precise control over the acid content ensures optimal solubility of die imidazoline while maintaining the desired pH range for effective corrosion inhibition.

[0069] The unique combination of imidazoline and alkoxylated polyamines (e.g., alkoxylated polyethyleneamines), along with the acid component, results in a corrosion inhibitor composition that outperforms conventional inhibitors while potentially reducing costs. This synergistic effect and the proposed mechanism of action represent a significant advancement in the field of corrosion inhibition for oil and gas applications.

[0070] In some cases, the corrosion inhibitor compositions may include specific ratios of alkoxylated polyamine (e.g., alkoxylated polyethyleneamines) to imidazolines, such as (50— 95):(5— 50), 90:10 or 9:1, 80:20 or 4:1, etc.

[0071] The imidazoline could be present in any concentration from 10 to 90 weight percent of the total composition (wt%). In some cases, the imidazoline concentration is from about 10 wt% to about 30 wt%. In some cases, the imidazoline component may be present in an amount of 15 wt% to 25 wt%’.

[9072] In some cases, the corrosion inhibitors is 5 wt% to 50 wt% of the total composition, such as 24 wt%.

[0073] The corrosion inhibitor compositions may be effective at relatively low concentrations in corrosive media. In some cases, the composition may provide corrosion inhibition when present in a concentration of 5 to 100 parts per million (ppm) in a corrosive medium. The effective amount of the corrosion inhibitor composition may be 5 to 100 ppm in the corrosive medium. In some cases, the effective amount of the corrosion inhibitor composition may be 15 to 25 ppm in the corrosive medium.

[0074] The concentration of the corrosion inhibitor composition in the corrosive medium may be adjusted based on factors such as the severity of the corrosive environment, the type of metal substrate being protected, and the specific components of the inhibitor blend. In some cases, higher concentrations within the 5 to 100 ppm range may be used in more aggressive corrosive environments or for more sensitive metal substrates.

[0075] The corrosion inhibitor compositions may be diluted with solvents or other fluids as necessary for particular applications. In some cases, die compositions may include solvents, coupling agents, viscosity modifiers, wetting agents, substances for lowering the freeze point of the compositions, substances for controlling evaporation of the compositions. In some cases, the compositions may be diluted with water, alcohols, glycols, or hydrocarbon solvents. The dilution may facilitate the handling and dosing of the corrosion inhibitor compositions in various industrial settings.

[0076] In some cases, diethylene glycol monobutyl ether may be used. The corrosion compositions may include 5 wt% to about 25 wt% diethylene glycol monobutyl ether, such as 13 wt%. Diethylene glycol monobutyl ether may act as a solvent to help dissolve and stabilize tire various components of the inhibitor blend, including die imidazoline and alkoxylated polyamines (e.g., alkoxylated polyethyleneamines). Diethylene glycol monobutyl ether may act as a coupling agent to help improve the compatibility between the oil-soluble and water-soluble components of the formulation, enhancing the overall stability of the inhibitor blend in the biphasic oil / water system. Dietliylene glycol monobutyl ether may act as a viscosity modifier to help adjust the viscosity of the formulation, improving its handling and application properties. Diethylene glycol monobutyl ether may act as a wetting agent to enhance the ability of the inhibitor to spread and adhere to metal surfaces, improving corrosion protection. Diethylene glycol monobutyl ether can lower the freezing point of the formulation, which is beneficial for cold weather applications or storage. The relatively low volatility of diethylene glycol monobutyl ether can help prevent rapid evaporation of the formulation, potentially extending the effective lifetime of the inhibitor.

[0077] In some cases, the ratio of alkoxylated polyamine (e.g., alkoxylated polyethyleneamine) to imidazoline in the corrosion inhibitor composition may be adjusted to optimize performance in specific corrosive environments. For example, a higher proportion of imidazoline may be used in environments with higher carbon dioxide content, while a higher proportion of alkoxylated polyamine (e.g., alkoxylated polyethyleneamine) may be used in environments with higher salt concentrations.

[0078] The specific concentration and ratio of components in the corrosion inhibitor composition may be selected based on factors such as the chemical composition of the corrosive medium, temperature, pressure, flow conditions, and the metallurgy of the system being protected. In some cases, laboratory testing or field trials may be conducted to determine the optimal composition and concentration for a particular application.

[0079] In some cases, the corrosion inhibitor compositions comprising alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) and imidazolines may exhibit synergistic effects, providing enhanced corrosion protection compared to the individual components used separately. The synergistic interaction between these components may result in improved performance across various corrosive environments.

[0080] Linear polarization resistance (LPR) measurements using a three-electrode configuration may be employed to evaluate the corrosion rates and inhibition efficiencies of the corrosion inhibitor compositions. In some cases, the LPR measurements may be conducted using a carbon steel working electrode, an Ag / AgCl reference electrode, and a graphite counter electrode. This method may allow for accurate and reproducible assessment of corrosion inhibition performance.

[0081] The corrosion inhibitor compositions may be tested under various conditions to evaluate their performance across different environments. In some cases, testing may be conducted at different temperatures, ranging from ambient to elevated temperatures typical of oil and gas production processes. The pH levels of the corrosive medium may also be varied to assess the effectiveness of the inhibitor compositions in acidic, neutral, and alkaline conditions. Additionally, the salt concentration of the corrosive medium may be adjusted to simulate different brine compositions encountered in field applications.

[0082] In some cases, the corrosion inhibitor compositions may exhibit foam reduction properties in addition to their corrosion inhibition effects. The foam reduction capabilities of the inhibitor blends may be evaluated using standardized foam testing methods. These tests may assess the ability of the compositions to reduce or prevent foam formation in the corrosive medium, which may be beneficial in certain oil and gas production processes.

[0083] A biphasic test method using kerosene and brine phases may be employed to simulate real-world conditions encountered in oil and gas production. In some cases, this method may involve preparing a mixture of kerosene and brine, typically in an 80:20 ratio of brine to kerosene. The corrosion inhibitor composition may be added to the kerosene phase, and its ability to partition into the brine phase and protect the metal substrate may be evaluated.

[0084] The synergistic effects of the corrosion inhibitor compositions may be observed through improved corrosion inhibition efficiency compared to the individual components. In some cases, blends containing 10 wt% to 30 wt% of imidazoline combined with alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) may provide superior corrosion protection compared to either component used alone at equivalent concentrations.

[0085] The performance improvements of the inhibitor blends may be particularly notable in carbon dioxide-saturated environments. In some cases, tire corrosion rates observed with the inhibitor blends may be significantly lower than those observed with individual components or conventional inhibitors. The synergistic effect may allow for the use of lower overall inhibitor concentrations while maintaining or improving corrosion protection.

[0086] In some cases, the alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) may enhance the film-forming properties of the imidazoline component on the metal surface. This synergistic interaction may result in a more robust and persistent protective film, leading to improved long-term corrosion protection. The combination of hydrophobic and hydrophilic moieties in tire inhibitor blend may also contribute to improved adsorption and surface coverage on the metal substrate.

[0087] The performance of the corrosion inhibitor compositions may be evaluated over extended periods to assess their long-term effectiveness. In some cases, testing may be conducted over several days or weeks to determine the stability and persistence of the protective effects. The inhibitor blends may demonstrate sustained corrosion protection over time, outperforming individual components or conventional inhibitors in long-term tests.

[0088] In some cases, the synergistic effects of the corrosion inhibitor compositions may extend to improved performance in the presence of other corrosive species, such as hydrogen sulfide or organic acids. The inhibitor blends may provide broader spectrum protection against multiple corrosion mechanisms commonly encountered in oil and gas production environments.

[0089] The performance improvements observed with the inhibitor blends may translate to potential cost savings in corrosion protection applications. In some cases, the use of these synergistic compositions may allow for reduced inhibitor dosage rates while maintaining effective corrosion protection, potentially lowering overall treatment costs in industrial applications.

[6090] In some cases, the corrosion inhibitor compositions comprising alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) and imidazolines may be used to inhibitcorrosion of metal substrates in contact with corrosive media containing carbon dioxide. The corrosion inhibitor compositions may be particularly useful in oil and gas industry applications where carbon dioxide-induced corrosion is a significant concern.

[0091] The method of inhibiting corrosion may involve adding an effective amount of the corrosion inhibitor composition to the corrosive medium. In some cases, the corrosion inhibitor composition may be added directly to the corrosive medium. In other cases, the composition may be injected into a flowing stream of the corrosive medium.

[0092] The effective amount of the corrosion inhibitor composition may vary depending on factors such as the severity of the corrosive environment, the type of metal substrate, and the specific composition of the inhibitor blend. In some cases, the effective amount may range from 5 to 100 ppm in the corrosive medium. In other cases, tire effective amount may be 15 to 25 ppm in the corrosive medium.

[0093] In some cases, the corrosion inhibitor composition may be added continuously to the corrosive medium to maintain a constant level of protection. In other cases, the composition may be added intermittently or in batch treatments, depending on the specific application and corrosion risk.

[0094] The corrosion inhibitor compositions may be applied in various oil and gas industry settings. In some cases, the compositions may be used in oil and gas production facilities to protect pipelines, storage tanks, and processing equipment from carbon dioxide-induced corrosion. The inhibitors may be added at various points in the production process, such as at wellheads, in gathering lines, or in separation facilities.

[0095] In some cases, the corrosion inhibitor compositions may be used in gas processing plants to protect equipment exposed to carbon dioxide-rich streams. The inhibitors may be applied to absorbers, strippers, heat exchangers, and other process vessels to mitigate corrosion risks.

[0096] The corrosion inhibitor compositions may also be used in transportation and storage applications within the oil and gas industry. In some cases, the compositions may be added to pipelines carrying carbon dioxide-containing fluids to protect the internal surfaces from corrosion. The inhibitors may also be used in storage tanks and terminals to prevent corrosion during extended periods of fluid storage.

[0097] In some cases, the corrosion inhibitor compositions may be applied using specialized dosing equipment. The dosing equipment may be designed to accurately meter andinject the inhibitor composition into the corrosive medium. In some cases, automated dosing systems may be used to maintain consistent inhibitor concentrations in the corrosive medium.

[0098] The method of applying the corrosion inhibitor compositions may involve monitoring the corrosion rates in the system being protected. In some cases, corrosion monitoring techniques such as linear polarization resistance (LPR) measurements, electrical resistance (ER) probes, or weight loss coupons may be used to assess the effectiveness of the inhibitor treatment and adjust the dosage as needed.

[0099] In some cases, the corrosion inhibitor compositions may be used in combination with other corrosion mitigation strategies. For example, the inhibitors may be used alongside cathodic protection systems, protective coatings, or materials selection to provide comprehensive corrosion protection in challenging environments.

[0100] The method of inhibiting corrosion using the corrosion inhibitor compositions may also involve periodic evaluation of the inhibitor performance. In some cases, this may include analyzing fluid samples to determine inhibitor residuals, conducting corrosion rate measurements, or inspecting protected equipment for signs of corrosion. The results of these evaluations may be used to optimize the inhibitor treatment program and ensure ongoing corrosion protection.EXAMPLES

[0101] The following examples are provided to illustrate specific embodiments of the present disclosure. These examples should not be construed as limiting the scope of the invention. The examples demonstrate the preparation and evaluation of corrosion inhibitor compositions including synergistic blends of alkoxylated alkoxylated polyamines (e.g., polyethyleneamines) and imidazolines. The general procedure outlines the methods used for preparing the inhibitor solutions and conducting corrosion inhibition testing. The specific examples show various compositions and their corrosion inhibition performance under conditions relevant to oil and gas production processes.

[0102] General procedure for the preparation of the inhibitor solutions:

[0103] The alkoxylated polyamines (e.g., alkoxylated polyethyleneamines) used in the following examples were prepared from the corresponding alkoxylated polyamines (e.g., polyethylenamines) by applying typical ethoxylation and propoxylation procedures using potassium hydroxide as a catalyst and acetic acid as neutralizing agent when needed. The imidazoline used in the following examples is Surfonic OFC 100, the 1:1 TOFA / DETA imidazoline, available from Indorama Ventures, The Woodlands, Texas.

[0104] The corrosion inhibitors were formulated as a 24% by weight aqueous solution. The solutions were prepared by mixing 24 wt% inhibitor, 13 wt% diethylene glycol monobutyl ether and the stoichiometric amount of glacial acetic acid needed to neutralize the amines in the inhibitor. The difference to 100% was made by addition of deionized water.

[0105] General procedure for corrosion inhibition testing:

[0106] Corrosion rates were measured in carbon dioxide (CO₂) saturated brine / kerosene at 60°C using linear polarization resistance (LPR) using a Squidstat Solo potentiostat (Admiral Instrument) in a three-electrode configuration consisting of one 1.72 x 0.25 inch 1080 carbon steel cylindrical electrode (working electrode), one Ag / AgCl in saturated KC1 electrode (reference electrode) and one graphite electrode (counter electrode). The corrosive test solutions were biphasic mixtures of 80% brine (3.5% aqueous NaCl) and 20% kerosene. 500 g of a stock solution of 3.5% aqueous NaCl were first de-oxygenated overnight using a nitrogen sparge. Subsequently, 450 g of the de-oxygenated solution was added with 112.5 g kerosene to the corrosion cell mounted with a condenser at 5°C. The mixture was then heated up to 60°C with stirring. Then, CO₂ was sparged at 0.5 L / min through the brine phase for one hour. At the end of the one-hour CO₂ saturation of the medium, the flow of CO₂ was reduced to 1 to 2 bubbles per second. After installation of the three electrodes, the LPR measurements were started and recorded every 20 minutes. The desired amount of inhibitor solution was added after 2h and the test was continued for another 14h (total of 16h of LPR data collection). The corrosion rates reported correspond to the average corrosion rate over the last 2h of the test.

[0107] Example 1: 20 ppm TETA-6EO-30PO / OFC100 (9:1)

[0108] The main inhibitor was prepared from a mixture of 10% by weight Surfonic OFC 100 and 90% by weight TETA-6EO-30PO. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 5.5 milli-inch per year (mpy), corresponding to about 93.0% inhibition efficiency.

[0109] Example 2: 20 ppm TETA-6EO-30PO / OFC100 (4:1)

[0110] The main inhibitor was prepared from a mixture of 20% by weight Surfonic OFC 100 and 80% by weight TETA-6EO-30PO. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 0.6 mpy, corresponding to about 99.3% inhibition efficiency.

[0111] Example 3: 10 ppm TETA-6EO-30PO / OFC100 (4: 1)

[0112] The main inhibitor was prepared from a mixture of 20% by weight Surfonic OFC 100 and 80% by weight TETA-6EO-30PO. 10 ppm of active inhibitor were use for thecorrosion test according to the procedure described above. The final corrosion rate was 0.7 mpy, corresponding to about 99.0% inhibition efficiency.

[0113] Example 4: 20 ppm TEPA-7EO-40PO / OFC100 (9:1)

[0114] The main inhibitor was prepared from a mixture of 10%’ by weight Surfonic OFC 100 and 90% by weight TEPA-7EO-40PO. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 2.4 mpy, corresponding to about 96.4% inhibition efficiency.

[0115] Example 5: 20 ppm TEPA-7EO-40 / OFC 100 (4: 1)

[0116] The main inhibitor was prepared from a mixture of 20% by weight Surfonic OFC 100 and 80% by weight TEPA-7EO-40PO. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 0.5 mpy, corresponding to about 99.4% inhibition efficiency.

[0117] Example 6: 10 ppm TEPA-7EO-40PO / OFC100 (4: 1)

[0118] The main inhibitor was prepared from a mixture of 20% by weight Surfonic OFC 100 and 80% by weight TEPA-7EO-40PO. 10 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 0.8 mpy, corresponding to about 98.9% inhibition efficiency.

[0119] Example 7: 20 ppm TETA-30PO-6EO / OFC100 (4:1)

[0120] The main inhibitor was prepared from a mixture of 20% by weight Surfonic OFC 100 and 80% by weight TETA-30PO-6EO. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 2.6 mpy, corresponding to about 96.7% inhibition efficiency.

[0121] Example 8: 20 ppm TETA-30PO / OFC100 (4:1)

[0122] The main inhibitor was prepared from a mixture of 20% by weight Surfonic OFC 100 and 80% by weight TETA-30PO. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 2.0 mpy, corresponding to about 97.4% inhibition efficiency.

[0123] Comparative example 1: 20 ppm OFC 100

[0124] The main inhibitor was prepared with only Surfonic OFC100 for comparison. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 1.0 mpy, corresponding to about 98.7% inhibition efficiency.

[0125] Comparative example 2: 4 ppm OFC 100

[0126] The main inhibitor was prepared with only Surfonic OFC 100. For comparison, only 4 ppm of active inhibitor were use for the corrosion test according to the procedure described above. That dosage corresponds to the amount of Surfonic OFC 100 present in the previous examples when it was used at 20% by weight in a 20 ppm dose. The final corrosion rate was 1.8 mpy, corresponding to about 97.7% inhibition efficiency.

[0127] Comparative example 3: 2 ppm OFC 100

[0128] The main inhibitor was prepared with only Surfonic OFC 100. For comparison, only 2 ppm of active inhibitor were use for the corrosion test according to the procedure described above. That dosage corresponds to the amount of Surfonic OFC 100 present in the previous examples when it was used at 10% by weight in a 20 ppm dose or at 20% by weight in a 10 ppm dose. The final corrosion rate was 10.3 mpy, corresponding to about 87.0% inhibition efficiency.

[0129] Comparative example 4: 20 ppm TETA-6EO-30PO

[0130] The main inhibitor was prepared with only TETA-6EO-30PO, for comparison with the examples where a mixture with Surfonic OFC 100 was used. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 112.4 mpy, well above the average corrosion rate of 79.2 mpy observed prior to the addition of any inhibitor.

[0131] Comparative example 5: 20 ppm TEPA-7EO-40PO

[0132] The main inhibitor was prepared with only TEPA-7EO-40PO, for comparison with the examples where a mixture with Surfonic OFC 100 was used. 20 ppm of active inhibitor were use for the corrosion test according to the procedure described above. The final corrosion rate was 124.5 mpy, well above the average corrosion rate of 79.2 mpy observed prior to the addition of any inhibitor.

[0133] Corrosion Inhibition Results: The main results for the corrosion inhibition study are summarized in Table 1 below.Dosage Corrosion Inhibition Sample Inhibitor(ppm) Rate (mpy) (%) TETA-6EO-30PO / OFC100Example 1 20 5.5 93(9:1)TETA-6EO-30PO / OFC100Example 2 20 0.6 99.3(4:1)TETA-6EO-30PO / OFC100Example 3 10 0.7 99(4:1)TEPA-7EO-40PO / OFC 100Example 4 20 2.4 96.4(9:1)Example 5 TEPA-7EO-40PO / OFC100 20 0.5 99.4(4:1)TEPA-7EO-40PO / OFC 100Example 6 10 0.8 98.9(4:1)TETA-30PO-6EO / OFC100Example 7 20 2.6 96.7(4:1)Example 8 TETA-30PO / OFC100 (4:1) 20 2 97.4 ComparativeOFC 100 20 1 98.7Example 1ComparativeOFC 100 4 1.8 97.7Example 2ComparativeOFC 100 2 10.3 87 Example 3ComparativeTETA-6EO-30PO 20 112.4 - Ex ample 4ComparativeTEPA-7EO-40PO 20 124.5 - Example 5Table 1. Corrosion Rates and Inhibition Efficiencies.

[0134] The average corrosion rate recorded for the C1018 carbon steel probes before addition of any inhibitor used in this study was about 79.2 mpy. The corrosion rate while using 20 ppm of only OFC 100 as inhibitor was measured at about 1.0 mpy (98.7% inhibition efficiency), confirming that the TOFA / DETA (1:1) imidazoline is indeed an excellent inhibitor for corrosion in CO₂, saturated brine. Also, if OFC 100 is used only by itself, when the amount dosed in is decreased to 4 and 2 ppm, the corrosion rates increase to about 1.8 mpy (97.7% inhibition efficiency) and 10.3 mpy (87.0% inhibition efficiency), respectively.

[0135] Notably, when 20 ppm active TETA-6EO-30PO or TEPA-7EO-40PO are used as sole inhibitor, there is no inhibition observed as the corrosion rates measured are 112.4 mpy and 124.5 mpy, respectively. Those corrosion rates are well above the average corrosion rate of 79.2 mpy observed prior addition to any inhibitor, as if the inhibitors never partitioned between the organic and aqueous phases and just stayed in the kerosene phase.

[0136] However, when at least 10% by weight of OFC100 in added to TETA-6EO-30PO or TEPA-7EO-40PO, the corrosion inhibition is greatly improved. For 20 ppm of TETA-6EO-30PO / OFC100 (9: 1), the corrosion rate measured is about 5.5 mpy (93% inhibition efficiency) and for 20 ppm of TEPA-7EO-40PO / OFC100 (9: 1), the corrosion rate measured is about 2.4 mpy (96.4% inhibition efficiency). The synergistic effect is clearly apparent when those corrosion rates are compared the corrosion rate of 10.3 mpy (only 87.0% inhibition efficiency) observed for the experiment run with only 2 ppm OFC 100, which corresponds to the equivalent amount of OFC100 present in 20 ppm of TETA-6EO-30PO / OFC100 (9:1) or 20 ppm of TEPA-7EO-30PO / OFC100 (9:1).

[0137] The synergy is even greater when the amount of OFC100 mixed with TETA-6EO-30PO or TEPA-7EO-40PO is increased to 20% by weight. Indeed, when only 10 ppm of TETA-6EO-30PO / OFC100 (4:1) is added, the corrosion rate drops to about 0.7 mpy (99.0% inhibition efficiency). Similarly, when 10 ppm of TEPA-7EO-40PO / OFC100 (4:1) is added, the corrosion rate is about 0.8 mpy (98.9% inhibition efficiency). Those corrosion rates are much better than the one obtained while using only 2 ppm OFC100, the equivalent amount of OFC100 present in 10 ppm of TETA-6EO-30PO / OFC100 (4:1) or 20 ppm of TEPA-7EO-30PO / OFC100 (4:1). Those corrosion rates are very similar (or even better, within the experimental error) to the one obtained while using 20 ppm OFC. Also, when 20 ppm of TETA-6EO-30PO / OFC100 (4:1) or 20 ppm of TEPA-7EO-40PO / OFC100 (4:1) are used, the corrosion rates further decrease to 0.6 mpy (99.3% inhibition efficiency) and 0.5 mpy (99.4% inhibition efficiency), respectively.

[0138] The following clauses illustrate example subject matter described herein.

[0139] Clause 1. A corrosion inhibitor composition, comprising: an alkoxylated polyethyleneamine having the formula:4 " Hwherein Ri, R2, R3, R4, Rs, Rs, R?, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49; andan imidazoline having the formula:wherein R contains at least 12 carbon atoms and m is an integer from 0 to 10, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

[0140] Clause 2. The corrosion inhibitor composition of clause 1, wherein the alkoxylated polyethyleneamine is derived from a polyethyleneamine selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethyl enetetramine (TETA), and tetraethylenepentamine (TEPA).

[0141] Clause 3. The corrosion inhibitor composition of any one of clauses 1 or 2, wherein R1, R2, R3, R4, R5, R6, R7, and R8 are each independently hydrogen.

[0142] Clause 4. The corrosion inhibitor composition of any one of clauses 1 through 3, wherein a is an integer from 2 to 5.

[0143] Clause 5. The corrosion inhibitor composition of any one of clauses 1 through 4, wherein Ry in the imidazoline contains 18 to 60 carbon atoms.

[0144] Clause 6. The corrosion inhibitor composition of any one of clauses 1 through 5, wherein the imidazoline is derived from tall oil fatty acid (TOFA).

[0145] Clause 7. The corrosion inhibitor composition of any one of clauses 1 through 6, wherein the composition provides corrosion inhibition when present in a concentration of 5 to 100 ppm in a corrosive medium.

[0146] Clause 8. A method of inhibiting corrosion of a metal substrate in contact with a corrosive medium containing carbon dioxide, the method comprising: adding to the corrosive medium an effecti ve amount of a corrosion inhibitor composition comprising an alkoxylated polyethyleneamine and an imidazoline, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

[0147] Clause 9. The method of clause 8, wherein the alkoxylated polyethyleneamine has the formula:wherein Ri, R2, R3, R4, R5, Re, R7, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49.

[0148] Clause 10. The method of any one of clauses 8 or 9, wherein the alkoxylated polyethyleneamine is derived from a polyethyleneamine selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

[0149] Clause 11. The method of any one of clauses 8 through 10, wherein the imidazoline has the formula:wherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10.

[0150] Clause 12. The method of any one of clauses 8 through 11, wherein R9 contains 18 to 60 carbon atoms and m is an integer from 0 to 3.

[0151] Clause 13. The method of any one of clauses 8 through 12, wherein the effective amount of the corrosion inhibitor composition is 5 to 100 ppm in the corrosive medium.

[0152] Clause 14. The method of any one of clauses 8 through 13, wherein the effective amount of the corrosion inhibitor composition is 15 to 25 ppm in the corrosive medium.

[0153] Clause 15. A system for inhibiting corrosion in an oil and gas production process, the system comprising: a metal substrate; a corrosive medium containing carbon dioxide in contact with the metal substrate; and a corrosion inhibitor composition comprising an alkoxylated polyethyleneamine and an imidazoline, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

[0154] Clause 16. The system of clause 15, wherein the alkoxylated polyethyleneamine has the formula:wherein Ri, R2, R3, R4, R5, Re, R7, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49.

[0155] Clause 17. The system of any one of clauses 15 or 16, wherein the alkoxylated polyethyleneamine is derived from a polyethyleneamine selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

[0156] Clause 18. The system of any one of clauses 15-17, wherein the imidazoline has the formula:wherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10.

[0157] Clause 19. The system of any one of clauses 15 through 18, wherein R9 contains 18 to 60 carbon atoms and m is an integer from 0 to 3.

[0158] Clause 20. The system of any one of clauses 15 through 19, wherein the corrosion inhibitor composition is present in the corrosive medium in a concentration of 5 to 100 ppm.

[0159] Clause 21. A corrosion inhibitor composition for use in a biphasic system, comprising: (a) an unreacted imidazoline compound; (b) an alkoxylated polyethyleneamine; and (c) a solvent, wherein the imidazoline compound acts as an emulsifier to partition the alkoxylated polyethyleneamine between an oil phase and a water phase of the biphasic system.

[0160] Clause 22. The composition of clause 21, wherein the imidazoline compound is derived from tall oil fatty acid (TOFA) and diethylenetriamine (DETA).

[0161] Clause 23. The composition of any one of clauses 21 or 22, wherein the alkoxylated polyethyleneamine is derived from triethylenetetramine (TETA) or tetraethyl enepentamine (TEPA).

[0162] Clause 24. The composition of any one of clauses 21 through 23, wherein the imidazoline compound comprises about 10% to about 30% by weight of the total composition.

[0163] Clause 25. The composition of any one of clauses 21 through 24, wherein the alkoxylated polyethyleneamine comprises about 70% to about 90% by weight of the total composition.Clause 26. A method for inhibiting corrosion in a biphasic system, comprising: (a) providing a corrosion inhibitor composition comprising an unreacted imidazoline compound and an alkoxylated polyethyleneamine; (b) introducing the composition into a biphasic system comprising an oil phase and a water phase; and (c) allowing the imidazoline compound to partition the alkoxylated polyethyleneamine between the oil phase and the water phase.

[0164] Clause 27. The method of clause 26, wherein the biphasic system is saturated with carbon dioxide.

[0165] Clause 28. The method of any one of clauses 26 or 27, wherein the corrosion inhibitor composition is present in the biphasic system at a concentration of about 10 ppm to about 25 ppm.

[0166] Clause 29. A synergistic corrosion inhibitor system for use in a carbon dioxide-saturated environment, comprising: (a) an unreacted imidazoline compound derived from tall oil fatty acid (TOFA) and diethylenetriamine (DETA); (b) an alkoxylated polyethyleneamine derived from tri ethylenetetramine (TETA) or tetraethylenepentamine (TEPA); and (c) a solvent, wherein the system exhibits improved corrosion inhibition compared to the imidazoline compound alone at equivalent concentrations.

[0167] Clause 30. The system of clause 29, wherein the improved corrosion inhibition is demonstrated by a lower corrosion rate as measured by Linear Polarization Resistance (LPR) in a biphasic oil-water system.

[0168] Clause 31. A method for measuring corrosion rates using Linear Polarization Resistance (LPR), the method comprising: a) providing a corrosive environment comprising a biphasic mixture of brine and kerosene saturated with carbon dioxide; b) immersing a working electrode comprising 1080 carbon steel, a reference electrode comprising Ag / AgCl in saturated KC1, and a counter electrode comprising graphite in the corrosive environment; c) maintaining the corrosive environment at a temperature of about 60°C; d) applying a potential to the working electrode using a potentiostat; e) measuring the current response to the applied potential; f) recording LPR measurements at predetermined intervals over a test period; g) calculating corrosion rates based on the recorded LPR measurements; and h) determining the effectiveness of a corrosion inhibitor composition by comparing the calculated corrosion rates in the presence and absence of the corrosion inhibitor composition.

[0169] Clause 32. A corrosion inhibitor composition, comprising: an alkoxylated polyamine; and an imidazoline.

[0170] Clause 33. The corrosion inhibitor composition of CLAUSE 32, wherein the alkoxylated polyamine is an alkoxylated polyamine derived from a polyamine selected from the group consisting of aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

[0171] Clause 34. The corrosion inhibitor composition of CLAUSE 32, wherein the alkoxylated polyamine is aminoethylethanolamine (AEEA).

[0172] Clause 35. The corrosion inhibitor composition of CLAUSE 32, wherein the imidazoline is derived from tall oil fatty acid (TOFA) and the alkoxylated polyamine is aminoethylethanolamine ( AEEA).

[0173] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

[0174] While the disclosure has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the disclosure is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore, it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the disclosure, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and / or “a portion” is used the item may include a portion and / or the entire item unless specifically stated to the contrary.

Claims

CLAIMSWhat is claimed is:

1. A corrosion inhibitor composition, comprising:an alkoxylated polyamine; andan imidazoline.

2. The corrosion inhibitor composition of claim 1, wherein the alkoxylated polyamine is derived from a polyamine selected from the group consisting of aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

3. The corrosion inhibitor composition of claim 1, wherein the alkoxylated polyamine is derived from aminoethylethanolamine (AEEA).

4. The corrosion inhibitor composition of claim 1, wherein the alkoxylated polyamine is an alkoxylated polyethyleneamine having the formula:0---H-dR»wherein Ri, R2, R3, R4, Rs, Re, R7, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 495. The corrosion inhibitor composition of claim 1, wherein the imidazoline has the formula:V! Hwherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10.

6. The corrosion inhibitor composition of claim 1, wherein the imidazoline is derived from tall oil fatty acid (TOFA), and the alkoxylated polyamine is derived from aminoethylethanolamine (AEEA).

7. The corrosion inhibitor composition of claim 1, wherein the composition provides corrosion inhibition when present in a concentration of 5 to 100 ppm in a corrosive medium.

8. A method of inhibiting corrosion of a metal substrate in contact with a corrosive medium containing carbon dioxide, the method comprising:adding to the corrosive medium an effective amount of a corrosion inhibitor composition comprising an alkoxylated polyamine and an imidazoline, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

9. The method of claim 8, wherein the alkoxylated polyamine is an alkoxylated polyethyleneamine having the formula:wherein Ri, R2, R3, R4, Rs, Re, R7, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49.

10. The method of claim 8, wherein the alkoxylated polyamine is an alkoxylated polyamine is derived from a polyamine selected from the group consisting of aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

11. The method of claim 8, wherein the imidazoline has the formula:wherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10.

12. The method of claim 8, wherein the imidazoline has the formula:i \ / H \X twherein R9 contains 18 to 60 carbon atoms and m is an integer from 0 to 3.

13. The method of claim 8, wherein the effective amount of the corrosion inhibitor composition is 5 to 100 ppm in the corrosive medium.

14. The method of claim 8, wherein the effective amount of the corrosion inhibitor composition is 15 to 25 ppm in the corrosive medium.

15. A system for inhibiting corrosion in an oil and gas production process, the system comprising:a metal substrate;a corrosive medium containing carbon dioxide in contact with the metal substrate; and a corrosion inhibitor composition comprising an alkoxylated polyamine and an imidazoline, wherein the imidazoline is present in an amount of 10 to 30 weight percent of the total composition.

16. The system of claim 15, wherein the alkoxylated polyamine is an alkoxylated polyethyleneamine having the formula:wherein Ri, R2, R3, R4, R5, Re, R?, and Rs are each independently hydrogen or methyl, a is an integer from 1 to 10, and b, c, d and e are each independently integers on average of 15 or less with the proviso that b+c+d+e is on average at least 30 and less than 49.

17. The system of claim 15, wherein the alkoxylated polyamine is an alkoxylated polyamine derived from a polyamine selected from the group consisting of aminoethylethanolamine (AEEA), ethylenediamine (EDA), diethylenetriamine (DETA), tri ethylenetetramine (TETA), and tetraethylenepentamine (TEPA).

18. The system of claim 15, wherein the imidazoline has the formula:wherein R9 contains at least 12 carbon atoms and m is an integer from 0 to 10.

19. The system of claim 15, wherein the imidazoline has the formula:wherein R9 contains 18 to 60 carbon atoms and m is an integer from 0 to 3.

20. The system of claim 15, wherein the corrosion inhibitor composition is present in the corrosive medium in a concentration of 5 to 100 ppm.

Images