WO1997028231A1

WO1997028231A1 - Corrosion inhibition in petroleum and natural gas production

Info

Publication number: WO1997028231A1
Application number: PCT/GB1997/000260
Authority: WO
Inventors: Dieter Faul; Matthias Kroner; Michael Ehle; Günter OETTER; Rudi KRÖNER
Original assignee: Baker Hughes Limited
Priority date: 1996-01-29
Filing date: 1997-01-29
Publication date: 1997-08-07
Also published as: DE19603027A1

Abstract

The use of polyaspartic acids which are modified in a hydrophobic manner with amines having at least 4 carbon atoms as corrosion inhibitors in petroleum and natural gas production.

Description

CORROSION INHIBITION IN PETROLEUM AND NATURAL GAS PRODUCTION

The present invention relates to corrosion inhibition in petroleum and natural gas production.

Petroleum and natural gas production involves considerable corrosion problems on plant parts composed mostly of low-alloy steels due to the aggressive constituents such as sulfur dioxide, carbon dioxide and salts dissolved in the formation water and/or water being conveyed. To minimize corrosion damage, therefore, corrosion inhibitors are added to the well fluid. Although a whole range of very effective corrosion inhibitors is known, the most effective products prove to be toxic to the environment. Products that are non-toxic and biodegradable are thus required for the off-shore production sector in particular.

Conventional, commercially used corrosion inhibitors for oil and gas production comprise predominantly condensation products of fatty acids and polyamines (imidazoline structures), quaternary ammonium compounds and fatty alkyl diamines. Said products are not readily biodegradable and are toxic to microorganisms.

A process for preventing scale deposits in, inter alia, water from oil wells is known from US-A 5 306 429 (1 ), wherein polyamino acid derivatives based on reaction products of primary or secondary amines, e.g. stearylamine with polysuccinimides or polyaspartic acid are used as scale inhibitors.

EP-A 644 257 (2) relates to the preparation of derivatives of polyamino acids such as polyaspartic acids by reaction of amino acids in the presence of acid catalysts, e.g. oxo acids of phosphorus such as orthophosphoric acid, and optionally with polyfunctional monomers. Polyfunctional monomers mentioned include, inter alia, diammes and polyamines, but no example is given The derivatives prepared in this way are also suitable as corrosion inhibitors and scale inhibitors in petroleum production

The subject of WO-A 94/01486 (3) is modified polyaspartic acids which can be obtained by polycondensation of aspartic acid with, inter a a, amines, e g C,- to C₂₂-alkylamιnes, aliphatic polyamines, amines containing hydroxyl groups or alkoxylated amines, in the presence of inorganic acids of phosphorus such as phosphoric acid or polyphosphonc acid Said modified polyaspartic acids are suitable as an additive for washing and cleaning agents, as water treatment agents and for preventing deposits duπng the concentration of sugarcane juice

The polycondensates of aspartic acid known from the cited pπor art are not sufficiently effective as corrosion inhibitors for oil and gas production, or their suitability for such a purpose has not yet been examined hitherto

The object of the invention was to provide effective and at the same time biodegradable and non-toxic corrosion inhibitors loi use in oil fields

According to a first aspect of the present invention there is provided the use of polyaspartic acids which are modified in a hydrophobic manner with amines having at least 4 carbon atoms as corrosion inhibitors in petroleum and natural gas production

According to a second aspect of the present invention there is provided a process for preventing corrosion in plant parts of petroleum and natural gas production installations, wherein polyaspartic acids which are modified in a hydrophobic manner with amines having at least 4 carbon atoms aie added to the well fluid as corrosion inhibitors The polyaspartic acids modified in a hydrophobic manner to be used according to the invention are obtained by incoφorating suitable amines with hydrophobic groups or hydrophobic-rendering structural elements in the polyaspartic acid structure. This incoφoration may be carried out either directly during thermal or acid-catalysed polycondensation of the known polyaspartic acid precursors L- or DL-aspartic acid, maleic acid and ammonia, maleic anhydride and ammonia, fumaric acid and ammonia, malic acid and ammonia, maleamide or fumaramide by co-condensation with the corresponding amines, or by subsequent reaction of polyaspartimide, polyaspartic acid or polyaspartic acid derivatives with the corresponding amines.

Highly effective corrosion inhibitors within the context of the present invention are obtained when polyaspartic acids or derivatives thereof are modified by incoφorating 1 to 99 mol-%, preferably 10 to 90 mol-%, particularly 30 to 80 mol-% of amines bearing one or more hydrophobic groups or structural elements.

Amines of this kind are understood to mean mainly primary, secondary or tertiary aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic mono- or polyamines with 1 to 100, particularly 4 to 50 carbon atoms, and 1 to 12, particularly 1 to 6 nitrogen atoms, C₂- to C₁₂-alkanolmono- di- and triamines, amines reacted with C₂- to C₄-alkylene oxides, and also polyalkylene glycols, the hydroxyl groups of which have been converted to corresponding amino groups by subsequent amination with ammonia, primary or secondary amines. Moreover, said amines should also be understood to include polymer compounds containing basic nitrogen atoms, such as homo- and copolymers containing vinylamine units, polyethylene imines, polypropene amines composed of 5 to 100 units of propene, and polyisobutene amines composed of 5 to 50 units of isobutene.

Typical examples of such amines are: Diethylamine, triethylamine. butylamine, dibutylamine, tributylamine_, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, isononylamine, decylamine, undecylamine, dodecylamine, tridecylamine, isotridecylamine, tetradecylamine_, pentadecylamine, cetylamine, stearylamine, oleylamine, tallow fatty amine, hydrogenated tallow fatty amine, coconut fatty amine, cyclohexylamine, N,N-di-(2- ethylhexyl)amine, N,N-didecylamine, N,N-di-(tridecyl)amine, N,N-di-

(tetradecyl)amine, N,N-dicetylamine, N,N-distearylamine, N,N-dioleylamine, N,N- ditallow fatty amine, hydrogenated N,N-ditallow fatty amine, N,N-dicoconut fatty amine, N,N-dicyclohexylamine, piperidine, moφholine, piperazine, benzylamine, aniline, toluidine, N-alkylimidazoles such as N-mcthyl- or N-ethylimidazole, N- alkylimidazolines such as N-methyl- or N-ethylimidazoline, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentaminc, pentaethylene hexamine, hexamethylene diamine, hexamethylene tetramine, N,N- dimethylaminopropylamine, N-(aminoethyl)fatty amines and N-(aminopropyl) fatty amines such as N-(aminoethyl)- or N-(aminopropyl)dodecylamine, - tetradecylamine, -cetylamine, -stearylamine, -oleylamine, -tallow fatty amine (in the non-hydrogenated or hydrogenated form) or -coconut fatty amine, N-(ami oethyl)- or N- (aminopropyl)piperazine, ethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine, tripropanolamine, isopropanolamine. di- isopropanolamine, triisopropanolamine, butanolamine, dibutanolamine, tributanolamine, polyethylene glycols with amino end groups, aminated nonionic surfactants which are derived from fatty, oxo or Ziegler alcohols and are polyoxyalkylene compounds with amino end groups, copolymers of ethylene oxide, propylene oxide and/or butylene oxide with amino end groups, reaction products of C_[2- to C_jg-alkyl- and alkenylamines such as cetylamine, stearylamine, oleylamine, tallow fatty amine or coconut fatty amine with 2 to 50 mol, mainly 5 to 30 mol of ethylene oxide, and reaction products of ethanolamine, diethanolamine or triethanolamine with 2 to 30 mol, mainly 3 to 20 mol of ethylene oxide. Preferred amines are C₄- to C₃₀-alkyl- or alkenylamines, di-C₄- to C₃₀-alkyl- or alkenylamines and aliphatic C₄- to C₅₀-polyamines with 2 to 4 basic nitrogen atoms. Further preferred amines, in addition to those mentioned, also include C₂- to C₄- alkanolamines and C₂- to C,₂-alkylene diamines. Moreover, amines having 6 to 30 carbon atoms, mainly 12 to 22 carbon atoms are particularly preferred. An individual amine or a mixture of different amines may be used.

The preparation of the polyaspartic acids or their derivatives modified in a hydrophobic manner to be used according to the invention may take place in the following manner.

Starting from L- or DL-aspartic acid, it is possible to prepare polyaspartimide by purely thermal means or with acid catalysis or by reaction of maleic anhydride with ammonia. The polyaspartimide obtainable in this manner is then reacted with the corresponding amine or amine mixture substituted with hydrophobic groups. Optionally, the amide units still remaining are then opened up with alkali. Depending on the stoichiometry chosen, polyaspartic acid derivatives are obtained in this way which mostly contain, in addition to polyaspartamide units, polyaspartic acid and alkali salts thereof and polyaspartimide units. If polyaspartimide, which has been condensed with acid catalysis, is used, the products prepared therefrom may also have structural units that are derived from inorganic radicals of the catalyst acid. These may be, e.g. : orthophosphoric acid, phosphorous acid, phosphinic acid or phosphonic acids and derivatives thereof, sulfuric acid, sulfurous acid or sulfonic acids and derivatives thereof. The inorganic groups may be bound in a salt-like manner or chemically by way of oxygen-phosphorus bonds, nitrogen-phosphorus bonds or by way of oxygen-sulfur bonds, or nitrogen-sulfur bonds.

Co- condensation of L- or DL-aspartic acid, maleic acid and ammonia, maleic anhydride and ammonia, fumaric acid and ammonia or malic acid and ammonia with the corresponding amines or amine mixtures substituted with hydrophobic groups is also possible. In all cases, the reaction may be catalyzed optionally by the addition of acid (e.g. orthophosphoric acid, sulfuric acid or hydrogen chloride). In these cases, the polymers may contain inorganic structural units of the corresponding acid radicals. These may be, e.g.: orthophosphoric acid, phosphorous acid, phosphinic acid or phosphonic acids and derivatives thereof, sulfuric acid, sulfurous acid or sulfonic acids and derivatives thereof. The inorganic groups may be bound in a salt-like manner or chemically by way of oxygen-phosphorus bonds, nitrogen-phosphorus bonds or by way of oxygen-sulfur bonds, or nitrogen-sulfur bonds.

The diluents used for the preparation of the polycondensates may be nonionic surfactants of the alkoxylated fatty, Ziegler and oxoalcohol type and also homo- and copolymers of ethylene oxide, propylene oxide and/or butylene oxide in a random or block type of polymerization. Further suitable diluents are orthophosphoric acid, sulfuric acid, alkali metal hydrogen sulfate melts, trimethylammonium hydrogen sulfate melts, dimethylformamide. dimethylsulfoxide, N-methylpyrrolidone, polyalkylene glycols or low-boiling solvents such as water, acetone or alcohols, e.g. methanol or ethanol, if their solvent power is sufficient.

The preparation may also take place by neutralizing polyaspartic acids (obtainable by hydrolysis of the corresponding polyaspartimide) with amines substituted with hydrophobic groups, or by adding aqueous solutions of amine hydrochlorides substituted with hydrophobic groups to aqueous solutions of polyaspartic acid sodium salt.

The preparation by reaction of polyaspartimide with preferably 30 to 80 mol- % of one or more mono- or polyamines bearing one or more hydrophobic groups is particularly preferred. The reaction takes place preferably in an organic solution at temperatures between 20 and 100°C, e.g. N-methylpyrrolidone or dimethylformamide being suitable solvents. The remaining imide units may then be partly or wholly opened up with alkali. The other conditions of polycondensation to polyaspartic acids not mentioned here are known to the expert and do not, therefore, need to be explained in more detail.

Depending on the quantity and type of amine components, the end products of the reactions described may be used as an organic solution (e.g. toluene solution), aqueous emulsion or aqueous solution.

The invention also provides a process for preventing corrosion in plant parts of petroleum and natural gas production installations, wherein polyaspartic acids which are modified in a hydrophobic manner with amines having at least 4 carbon atoms are added to the well fluid as corrosion inhibitors.

The polyaspartic acids or polyaspartic acid derivatives prepared according to the process described and modified in a hydrophobic manner with the amines mentioned are highly effective corrosion inliibitors for the specific applications of petroleum and natural gas production and are also biodegradable and non-toxic to the environment.

Examples

Preparation of the polyaspartimides used

Polyaspartimide 1

100 g of maleic acid monoamide which was prepared by reaction of maleic anhydride and ammonia in acetone were introduced into a 500 ml flask and the flask was evacuated by means of a filter pump. The evacuated flask was immersed in an oil bath pre-heated to 170°C and the reaction vessel was left for 5 hours at this temperature. During this period, the contents of the flask swelled with foaming. After cooling, the foam could be crushed to a fine powder. The molecular weight (weight-average) of the polyaspartimide was 3,000. The K value in a 1 wt.% solution in dimethylformamide was 12.

Polyaspartimide 2

133 g of aspartic acid were introduced into a one liter round-bottomed flask and heated to 240°C whilst passing a stream of nitrogen through until 95% of the theoretically possible quantity of water had formed. The contents of the flask were composed of a yellowish orange powder. The polyaspartimide had a molecular weight (weight-average) of 6,000. The K value in a 1 wt.% solution in dimethylformamide was 18.

Polyaspartimide 3

133 g of aspartic acid and 326 g of 75 wt.% orthophosphoric acid were introduced into a one liter reactor with an anchor agitator and the reactor was evacuated by means of a filter pump. Water was distilled by gradually heating the flask to 180°C and the reaction mixture was polycondensed. After 5 hours the contents were cooled and the reaction product was taken up with 500 ml of water. The polyaspartimide was washed with water to remove the phosphoric acid and dried in the drying cabinet at 80°C. The molecular weight was 30,000. The K value in a 1 wt.% solution in dimethylformamide was 24. The phosphorus content in the polyaspartimide was 0.1 wt.%. Preparation of Examples no. 1 to 9

The quantity of the corresponding polyaspartimide given in Table 1 was dissolved in the stated quantity of dimethylformamide (DMF), and the stated quantity of the correspondmg amine(s) was added thereto at 60°C. After all the amine(s) had been added, the mixture was stirred for 5 hours at this temperature. The solvent was then removed under vacuum. Depending on the Example in question, the solid obtained in this way was used directly as a toluene solution or underwent controlled alkaline hydrolysis. Hydrolysis was carried out in such a way that a suspension of the solid was formed in water to which the stated quantity of a 30 wt.% NaOH solution was then added at 60°C. The aqueous solution or emulsion thus obtained was used in these cases.

Preparation of Examples no. 10 to 12

A mixture of 133 g of L-aspartic acid, 326 g of a 75 wt.% orthophosphoric acid and of the quantity of the corresponding amine indicated in Table 2 was prepared in a 2 liter laboratory reactor and the water was removed at 100°C by applying a vacuum by means of a filter pump. The temperature was then raised to 180°C and polycondensation was continued for 3 hours. The contents of the reactor were then cooled and the polycondensation product was taken up in one liter of water and the insoluble residue was washed with one liter of water. A suspension of the washed polycondensate was formed in 500 ml of water at 60°C. 20 wt.% sodium hydroxide solution was then added such that the pH of the reaction solution was between 8 and 10. Hydrolysis was completed when no more insoluble or non-emulsified proportions were present. Clear to cloudy solutions or milky emulsions were obtained.

Table 2

Preparation of polyaspartic acids modified in a hydrophobic manner by co-condensation

Ex. Amine Quantity of Solids content K value (2 wt.% No. amine (g) (wt.%) in H₂0)

10 octadecylamine 135 24.2 25

1 1 N-aminopropyl 89.4 18.5 37 tallow fatty amine

12 N-aminopropyl 179 16.7 58 tallow fatty amine Testing the Examples as corrosion inhibitors

The products obtained were tested in the standardized "wheel test" for their corrosion-inhibiting effect for use in oil and gas production. Iron test bars are incoφorated in glass bottles which rotate on an axis at 40 φm. The test medium is a mixture of 50 parts by wt. of a 3 wt.% aqueous NaCl solution and 50 parts by wt. of n-octane. To simulate "sweet corrosion", the test solution is saturated with C0₂ gas. To simulate a "sour corrosion medium", the solution is additionally saturated with H₂S gas. The reference sample remains without additive, whilst in each case 25 ppm of active substance of the corresponding Example is added to the other test bottles. The test time is 16 h, the test temperature is 80°C. The corrosion-inhibiting effect is obtained from the percentage by weight reduction in the metal removal determined in relation to the reference sample, and is calculated according to the following formula:

removal from reference sample-removal from sample corrosion-inhibit = 100(%) ing effect removal from reference sample

The ideal value would be 100% if there were no measurable metal removal from the sample.

Table 3 below shows the results of the tests.

Table 3

Results of the corrosion inhibitor test ("Wheel test")

Example no. Corrosive agent Corrosion-inhibiting effect

1 C0₂ 50% C0₂/H₂S 74%

2 C0₂ 57% C0₂/H₂S 78%

C0₂ 60% C0₂/H₂S 83%

4 C0₂ 51 % C0₂/H₂S 78%

5 CO₂ 10% C0₂/H₂S 53%

6 C0₂ 58% C0₂/H₂S 69%

7 C0₂ 75% C0₂/H₂S 64%

8 C0₂ 56% C0₂/H₂S 44%

9 C0₂ 47%

C0₂/H₂S 61%

12 co₂ 59%

C0₂/H₂S 72% The use of polyaspartic acids modified in a hydrophobic manner with amines sion inhibitors in petroleum and natural gas production

Claims

1. The use of polyaspartic acids which are modified in a hydrophobic manner with amines having at least 4 carbon atoms as corrosion inliibitors in petroleum and natural gas production.

2. The use of polyaspartic acids according to Claim 1 which are modified by incoφorating 30 to 80 mole-% of the amine.

3. The use of polyaspartic acids according to Claim 1 or 2 which are modified with an amine having 4 to 50 carbon atoms and 1 to 12 nitrogen atoms.

4. The use of polyaspartic acids according to Claim 3 which are modified in a hydrophobic manner with C₄- to C₃₀-alkyl- or alkenylamines, di-C₄- to C₃₀-alkyl- or alkenylamines or aliphatic C₄- to C₅₀-polyamines with 2 to 4 basic nitrogen atoms.

5. A process for preventing corrosion in plant parts of petroleum and natural gas production installations, wherein polyaspartic acids which are modified in a hydrophobic manner with amines having at least 4 carbon atoms are added to the well fluid as corrosion inhibitors.

6. The process according to Claim 5 wherein the polyaspartic acid is modified by incoφorating 30 to 80 mole-% of the amine.

7. The process according to Claim 5 or 6 wherein the polyaspartic acid is modified with an amine having 4 to 50 carbon atoms and 1 to 12 nitrogen atoms.

8. The process according to Claim 7 wherein the polyaspartic acid is modified with a C₄- to C₃₀-alkyl- or alkenylamine, di-C₄- to C₃₍₎-alkyl- or alkenylamine or aliphatic C₄- to C₅₀-polyamine with 2 to 4 basic nitrogen atoms.