METHOD FOR ENHANCING METAL CORROSION INHIBITION IN OIL AND NATURAL GAS PRODUCTION

Abstract

The use of synthetic polymer in combination with an organic corrosion inhibiting compound having at least one unsaturated carbon-carbon bond, preferably selected from the group of acetylenic alcohols, ,-unsaturated aldehydes, and/or -alkenyl phenones, reduces or inhibits corrosion of metal equipment present during acidizing treatment in gas- or oilfield reservoirs with one or more acids. Also disclosed is a method for reducing or inhibiting corrosion of steel equipment present during an acid treatment of a gas- or oilfield reservoir with one or more acids by using a specific synthetic polymer as corrosion inhibitor in combination with an organic corrosion inhibiting compound having at least one unsaturated carbon-carbon bond, preferably selected from the group of acetylenic alcohols, ,-unsaturated aldehydes, and/or -alkenyl phenones.

Claims

1. A corrosion inhibitor is an aqueous mixture comprising (i) water and (ii) a mixture consisting of (iia) water soluble synthetic polymer comprising ethylenically unsaturated carboxylic, sulfonic or phosphonic acids, their esters, unsubstituted or N- and N,N-substituted derivatives of amides of ethylenically unsaturated carboxylic acids, N-substituted (cyclic) derivatives of ethylenically unsaturated amides and (iib) at least of one organic compound having at least one unsaturated carbon-carbon bond as organic corrosion inhibiting compound, whereby the corrosion inhibitor reduces or inhibits corrosion of metal equipment present during acidizing treatment in gas or oilfield reservoirs with one or more acids.

2. The corrosion inhibitor of claim 1 wherein the water soluble synthetic polymer comprising (I) at least structural units of formula (I) ##STR00011## wherein R1, R2 and R3 independently are hydrogen or C.sub.1-C.sub.6-alkyl, (II) from 0 to 95% by weight structural units of formula (II) ##STR00012## wherein R4 is hydrogen or C.sub.1-C.sub.6-alkyl, R5 is hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine, A is a covalent CS bond or a two-valent organic bridging group, (III) from 0 to 95% by weight structural units of formula (III) ##STR00013## wherein R6 and R7 are independently of one another hydrogen, C.sub.1-C.sub.6-alkyl, COOR.sub.9 or CH.sub.2COOR.sub.9, with R.sub.9 being hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine, R8 is hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine, or is C.sub.1-C.sub.6-alkyl, a group C.sub.nH.sub.2nOH with n being an integer between 2 and 6, or is a group C.sub.oH.sub.2oNR10R11, with o being an integer between 2 and 6, and R10 and R11 are independently of one another hydrogen or C.sub.1-C.sub.6-alkyl, (IV) from 0 to 95% by weight structural units of formula (IV) ##STR00014## wherein R12 and R13 are independently of one another hydrogen, C.sub.1-C.sub.6-alkyl, COOR.sub.16 or CH.sub.2COOR.sub.16, with R.sub.16 being hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine, R14 is hydrogen or, C.sub.1-C.sub.6-alkyl, and R15 is COH, COC.sub.1-C.sub.6-alkyl or R14 and R15 together with the nitrogen atom to which they are attached form a heterocyclic group with 4 to 6 ring atoms, (V) from 0 to 20% by weight structural units of formula (V) ##STR00015## wherein R17 is hydrogen or, C.sub.1-C.sub.6-alkyl, and R18 and R19 are independently of one another hydrogen, a cation of an alkaline metal, of an earth alkaline metal, of ammonia and/or of an organic amine, B is a covalent CP bond or a two-valent organic bridging group, with the proviso that the percentage of the structural units of formulae (I) to (V) refer to the total mass of the copolymer and the percentage of the structural units of formulae (I) to (V) amounts to 100%.

3. The corrosion inhibitor of claim 2, wherein the water soluble synthetic polymer material is selected from the group consisting of polymers containing: (I) 10 to 90% by weight of structural formula I, (II) 0 to 80% by weight of structural formula II, (III) 0 to 50% by weight of structural formula III, (IV) 0 to 50% by weight of structural formula IV, (V) 0 to 20% by weight of structural formula V, referred to the total mass of the polymer.

4. The corrosion inhibitor of claim 2 wherein the structural units of formula (I) are obtained from an ethylenically unsaturated carboxylic acid amide selected from the group of acrylamide, methacrylamide and/or their NC.sub.1-C.sub.6-alkyl derivatives or N,NC.sub.1-C.sub.6-dialkyl derivatives.

5. The corrosion inhibitor of claim 2 wherein the polymer contain structural units of formula (II) to (V) which are obtained from an ethylenically unsaturated sulfonic acid and/or its alkaline metal salts and/or their ammonium salts, from ethylenically unsaturated carboxylic acid and/or its alkaline metal salts and/or their ammonium salts, from N-vinylamides, and/or an ethylenically unsaturated phosphonic acid and/or its alkaline metal salts and/or their ammonium salts, optionally together with further copolymerisable monomers.

6. The corrosion inhibitor of claim 2 wherein the polymer is a copolymer with structural units of the formula (II) obtained from vinylsulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid and/or their alkaline metal salts and/or their ammonium salts.

7. The corrosion inhibitor of claim 2 wherein the polymer is a copolymer with structural units of the formula (III) obtained from ethylenically unsaturated carboxylic acid and/or their derivatives.

8. The corrosion inhibitor of claim 2 wherein the polymer is a copolymer with structural units of the formula (IV) obtained from N-vinylamide.

9. The corrosion inhibitor of claim 2 wherein the polymer is a copolymer with structural units of the formula (V) being vinylphosphonic acid and/or its alkaline metal salts and/or its ammonium salts, and/or allylphosphonic acid and/or its alkaline metal salts and/or its ammonium salts.

10. The corrosion inhibitor of claim 1 wherein the acid consists of one or more Brnsted acids.

11. The corrosion inhibitor of claim 1 wherein the total concentration of the synthetic polymer is from 0.01 to 10% by weight referred to the mass of treatment fluid.

12. The corrosion inhibitor of claim 1 wherein the viscosity of the treatment fluid is increased by ionically crosslinking the polymer by multivalent metal ions or metal complexes selected from group IIIA, IVB, VB, VIB, IIVB and/or VIIIB of the periodic table of elements.

13. The corrosion inhibitor of claim 1 wherein the viscosity of the treatment fluid is from 3 mPas to 5000 mPas.

14. The corrosion inhibitor of claim 1 wherein the total concentration of the organic corrosion inhibiting compound having at least one unsaturated carbon-carbon bond is from 0.001 to 5% by weight referred to the mass of treatment fluid.

15. The corrosion inhibitor of claim 14, wherein the acetylenic alcohol is propargyl alcohol, 1-octyn-3-ol, 1 hexyn-3-ol, or 2-methyl-3-butynol, the ,-unsaturated aldehyde is cinnamaldehyde, p-methyl-cinnamaldehyde, p-hydroxy-cinnamaldehyde, p-methoxy-cinnamaldehyde, crotonaldehyde, or 2-hexenal, the -alkenyl phenon is phenyl vinyl ketone, 2-benzoyl-3-hydroxy-1-propene, or 2-benzoly-3-methoxy-1-propene.

16. The corrosion inhibitor of claim wherein the treatment fluid further contains natural based polymers, polysaccharides or modified polysaccharides.

17. A method for reducing or inhibiting corrosion of steel equipment being present during an acid treatment of a gas- or oilfield reservoir with one or more acids comprising the measures: (i) providing an aqueous viscosified treatment fluid containing at least an acid, a water soluble synthetic polymer, and at least one corrosion inhibiting compound (ii) pumping the treatment fluid into the formation using steel equipment, characterised in that (iii) the synthetic polymer is a polymer comprising ethylenically unsaturated carboxylic, sulfonic or phosphonic acids, their esters, unsubstituted or N- and N,N-substituted derivatives of amides of ethylenically unsaturated carboxylic acids, N-substituted (cyclic) derivatives of ethylenically unsaturated amides and (iv) the corrosion inhibiting compound is an organic compound has at least one unsaturated carbon-carbon bond, preferably selected from the group of acetylenic alcohols, ,-unsaturated aldehydes, and/or -alkenyl phenones.

18. The method of claim 17, wherein the water soluble synthetic polymer material is defined in claim 2.

19. The method of claim 17 wherein the corrosion inhibiting compound is defined in claim 14.

20. The corrosion inhibitor of claim 1 wherein at least one unsaturated carbon-carbon bond is selected from the group of acetylenic alcohols, ,-unsaturated aldehydes, and/or -alkenyl phenones.

Description

EXAMPLES

Example 1: Preparation of a Polymer Via Inverse Emulsion Polymerization

[0161] 37 g sorbitan monooleate were dissolved in 160 g isoparaffin. 100 g water in a beaker were cooled to 5 C., then 50 g 2-acrylamido-2-methylpropane sulfonic acid and 10 g vinylphosphonic acid were added. The pH was adjusted to 7.1 with aqueous ammonia solution. Subsequently 223 g acryl amide solution (60 weight % in water) were added.

[0162] Under vigorous stirring the aqueous monomer solution was added to the isoparaffin mixture. The emulsion was then purged for 45 min with nitrogen. The polymerization was started by addition of 0.5 g azoisobutyronitrile in 12 g isoparaffin and heated to 50 C. To complete the reaction the temperature was increased to 80 C. and maintained at this temperature for 2 h. The polymer emulsion was cooled to room temperature. As product, a viscous fluid was obtained.

[0163] The K-value of the copolymer of ex. was 390.

Example 2: Preparation of a Polymer Via Inverse Emulsion Polymerization

[0164] A polymer emulsion was prepared according to example 1 but using 80 g 2-acrylamido-2-methylpropane sulfonic acid, no vinylphosphonic acid and 187.5 g acryl amide solution (60 weight % in water).

[0165] The K-value of the copolymer of ex. 2 was 441.

Example 3: Preparation of a Polymer Via Gel Polymerization

[0166] 400 ml deionized water and 9.2 ml 25 weight-% aqueous ammonia solution were placed in a reaction vessel. 70 g acryl amide and 30 g acrylic acid were added under stirring. The solution was purged with nitrogen and heated to 50 C. The polymerization was started by addition of 5 ml of a 20% by weight aqueous solution of ammonium persulfate. To complete the reaction the temperature was increased to 80 C. and maintained at this temperature for 2 h. After cooling to room temperature a highly viscous gel was obtained. The gel was dried at 90 C. in a vacuum drying oven and carefully chopped from time to time. The dried polymer was crushed to obtain small particles.

[0167] The K-value of the copolymer of ex. 3 was 418.

Examples 4 to 12

[0168] To prepare the acidic solution from inverse polymer emulsion, 1.5 g isotridecan ethoxylate (6 EO) surfactant were added to 150 g of hydrochloric acid in a Waring blender. Then, polymer emulsion and/or organic corrosion inhibiting compound were added and mixed for 4 min.

[0169] To prepare the acidic solution from solid polymer, the polymer powder and/or the organic corrosion inhibiting compound were added to 150 g hydrochloric acid in a Waring blender and mixed for 10 min. Then solution was poured into a beaker and stirred overnight slightly using a magnetic bar stirrer.

[0170] Tests were conducted at 90 C. for 3 h. The concentrations of hydrochloric acid, synthetic polymer and the organic corrosion inhibiting compound as well as the results are given in table 2.

TABLE-US-00001 TABLE 2 Polymer or Conc. Of polymer Conc. Conc. inhibitor Example Steel HCl, % emulsion polymer, % emulsion, % Compound compound, % Weight loss, % 4 ref 1.4301 15 30.4 5 1.4301 15 Ex. 1 2.2 9.6 6 1.4301 15 Ex. 1 0.6 Propargyl 0.05 2.5 alcohol 7 1.4301 15 Propargyl 0.05 7.2 alcohol 8 1.4301 15 Cinnamaldehyde 0.3 8.9 9 1.4301 15 Ex. 1 0.6 Cinnamaldehyde 0.3 1.0 10 1.4301 15 Ex. 2 2.2 Propargyl 0.05 0.8 alcohol 11 1.4301 15 Ex. 2 2.2 Propargyl 0.3 0.08 alcohol 12 1.4301 15 Ex. 3 0.6 Propargyl 0.3 2.3 alcohol

[0171] Concentrations of HCl, polymer powder and polymer emulsion are given in % by weight relative to the total mass of the acidic test solution.

[0172] The weight loss of steel specimen is given in % by weight relative to the initial weight of the specimen before testing.

[0173] The examples clearly show that steel is significantly less attacked by hydrochloric acid in various concentrations when polymers according to the invention are present compared to reference tests where hydrochloric acid without polymers were used. Organic corrosion inhibiting compound according to the invention also clearly reduces acid corrosion even at low concentration. The combination of synthetic polymer and corrosion inhibiting compounds significantly enhances the corrosion inhibiting efficiency against acidic attack.

[0174] The corrosion inhibition effect is obvious even at very low concentration of polymer.