GB2027686A - Corrosion Inhibitor for Aqueous Brines - Google Patents

Abstract

Corrosion of ferrous metals, particularly metal goods in a wellbore, by aqueous brines is inhibited by including in the brine, an effective amount of a dispersible sulfur compound wherein the sulfur has an oxidation state of zero or less. Preferably, a quaternary pyridinium, quinolinium or isoquinolinium salt is also employed. Inclusion of a cobalt salt is also sometimes desirable. The sulfur compound is preferably ammonium thiocyanate or thiourea.

Description

SPECIFICATION Corrosion Inhibitor for Aqueous Brines The invention relates to inhibiting corrosion of ferrous metais by aqueous brines. In a specific application for the petroleum industry, it relates to reducing corrosion of iron and steel casing, tubing, and other ferrous subterranean well structural parts exposed to aqueous brines used as completion, work over, or packer fluids.

In well treating operations, brines are utilized for various purposes, especially where a relatively dense aqueous fluid is desired. Alkali metal salt brines may be employed, but more typically, calcium chloride brines, calcium bromide brines, or a mixture thereof are employed because solutions of greater specific gravity may be obtained. Such brines are corrosive to the metal goods in the wellbore, even in the absence of substantially any oxygen. Such corrosion is relatively insignificant at temperatures of about 2000F, but becomes fairly significant at temperatures of at least 2500F, especially above about 3000F.

Although some corrosion inhibitor well suited for inhibiting HCI may find some utility in inhibiting brines, it cannot be said that a hydrochloric acid inhibitor will necessarily be effective in inhibiting brines, at least not to a practical degree.

Canadian Patent No. 983,041 teaches a water soluble corrosion inhibitor for brines comprising the reaction product of certain aliphatic saturated carboxylic acids with substituted imidazolines.

U.S. Patent No. 3,21 5,637 teaches that a mixture of sodium silicate and zinc chloride inhibits corrosion by sodium chloride and calcium chloride brines. The patent also discusses shortcomings of other known brine inhibitors such as sodium nitrate, hydrazine, pyrogallol, or sulphite.

U.S. Patent No. 4,010,111 discloses a corrosion inhibiting composition for aqueous brines wherein the inhibitor contains a reaction product of a carboxylic acid and a polyamine, an alcohol, and an alkylbenzene sulfonic acid.

At the time of this invention, it is believed that among the most widely used commercial inhibitors for heavy brines-at least in the United States petroleum industry-were BaroidB Coat B1400 inhibitor and CorexitO 7720 inhibitor.Analysis of a sample of the Baroid product indicates it contains about 14 percent by weight of a volatile amine, about 1 9 percent by weight of isopropyl alcohol, about 45 percent by weight of water, and the balance predominantly ethoxylated amide with a small amount of carboxylic acid salt The present invention is based on the discovery that ferrous metals can be at least partially protected from corrosion by aqueous brines by including in the brine, an effective amount of a sulfur compound wherein the oxidation state of the sulfur is zero or less, which is uniformly dispersible in, and preferably soluble in, said brine and which is capable of making sulfur available for reaction with the ferrous metal to be protected to form a protective iron sulfide film on the surface of the metal exposed to the inhibited brine.Preferably, at least one quaternary pyridinium, quinolinium, or isoquinolinium salt which is soluble in the brine is also employed as an inhibitor aid.

Aqueous solutions of alkali metal halides may be inhibited using the composition of the present invention, although its greatest benefit is realized where the brine contains at least one polyvalent metal halide salt, such as calcium chloride, bromide, or iodide, zinc chioride, bromide, or iodide, or a mixture of such salts. Such brines are commonly used in oil field applications, as well as in other industries. For example, such brines may be used in separation processes wherein solids of different densities are separated by flotation. In addition to the corrosion inhibitor, such brines may contain various functional additives, if desired, such as fluid loss additives, gelling agents, friction reducers, or surfactants.Brine solutions which may be inhibited according to the present invention include aqueous organic acid solutions weighted with a suitable metal halide salt to increase the specific gravity thereof, although in most instances, solutions treated according to the present invention will normally have a slightly basic pH and will consist substantially of aqueous solutions of calcium or zinc halides or mixtures thereof.

The corrosion inhibitor system of the present invention has good inhibitive properties, especially at the higher temperatures where the corrosion caused by brines would otherwise become relatively serious. It is also compatible with a wide range of functional additives. Moreover, particularly the most preferred embodiments act as a defoaming agent, thereby simpiifying field mixing procedures.

The sulfur compound is preferably a water-soluble thio compound, e.g. a thiocyanate such as an alkali metal thiocyanate or, most preferably, ammonium thiocyanate. It can also be an organic thioamide and essentially any such compound is operable. This class of compounds includes thiourea-, a polythiourea, a hydrocarbon substituted derivative thereof, or a thioamide having the formula:

wherein A is a hydrocarbon radical of 1-12 carbon atoms or a pyridyl radical and each R" is a hydrogen atom or an alkyl radical of 1-8 carbon atoms. Thioamides such as thiourea, 1,2- diethylthiourea, propylthiourea, 1,1 -diphenylthiourea, thiocarbanilide, 1 ,2dibutylthiourea, dithiobiurea, thioacetamide, thionicotinamide, or thiobenzamide are representative of this class.Water soluble sulfides such as ammonium sulfide, an alkali metal sulfide, or corresponding hydrosulfide including H2S are other operable thio compounds. Elemental sulfur which is dispersible in the brines is also operable, although the above mentioned soluble thio compounds are preferred.

Preferably, a quaternary prydinium, quinolinium, or isoquinolinium salt which is stable in the aqueous brine solution is also employed as the inhibitor acid. Preferably, this salt has the formula:

where R is an alkyl radical of 1-20 carbon atoms, a benzyl radical, or an alkylated benzyl radical wherein the aromatic ring has one or more alkyl substituents totalling 1-20 carbon atoms, each R' is a hydrogen atoms or an alkyl or alkoxy radical of 1-6 carbon atoms, and Xis any convenient anionic radical such as halide, sulfate, acetate, or nitrate. Obviously, those skilled in the art will realize that the various parameters should not be selected to provide a compound having such a high carbon content that the compound is not soluble in the brine at at least an effective concentration.In the above general formulae, X is preferably a bromine or chlorine atom, and most preferably bromine. Preferably, R is a higher alkyl radical of about 6-1 6 carbon atoms. Also, R' is preferably hydrogen. Pyridinium salts are generally preferred. The most preferred embodiment considering both performance and solubility is noctylpryidinium bromide. Mixtures of such salts may be employed if desired.

While any significant quantity of the sulfur compound will provide some degree of inhibition of corrosion, at least about 0.3 grams of the sulfur compound per liter of brine solution is usually required to provide practical protection. Concentrations as high as 20 grams of the inhibitor per liter are, for the most part, not detrimental. More than about 3 grams of the inhibitor per liter of brine, however, usually provides little or no additional protection, and in some cases may actually provide less protection than smaller amounts.The preferred upper limit of 3 grams per liter applies whether the sulfur compound is employed alone or in combination with the heterocyclic quaternary compound, i.e. when the quaternary compound is employed, the total concentration of the quaternary and sulfur compounds preferably does not exceed 3 liter. Most preferably, the total concentration of sulfur compound and quaternary salt is from about 0.5-2 grams per liter of brine.

If employed, the quaternary salt is employed in an amount which is effective to improve the overall inhibition of the system. The optimum ratio of the quaternary salt to the sulfur compound will vary somewhat from system to system, but generally, benefit is realized when the two components are employed in a weight ratio of from 0.1:1 to 10:1, although a ratio of from 0.125:1 to 4:1 is more preferred. A ratio of 0.2:1 to 1:1 is most preferred, especially where the concentration of the components approaches the upper or lower limits recommended in the preceding paragraph. For any given brine system and combination of inhibitor components, those skilled in the art will be able to arrive at an optimum concentration and ratio.

The addition of a small but effective amount-e.g., from 0.05 to 0.5 gram Co+2 per liter of brineof a water soluble cobalt salt to the system also improves its effectiveness, but is not necessary for an operable or even commercially acceptable performance. Consequently, though somewhat better performance is obtained with the cobalt, it is not normally a preferred embodiment for routine applications because of somewhat increased toxicity and environmental concerns. If employed, the cobalt may be provided by essentially any cobaltous compound which is sufficiently soluble in the aqueous brine solution to provide the desired concentration of cobaltous ions. Salts such as CoCI2, CoBr2, CoSO4, Co(NO3)2, colbaltous acetate, or cobaltous benzoate are all suitable sources of cobaltous ions.Salts such as the acetate, benzoate, or bromide are particularly preferred.

The present invention is further illustrated by the following examples and comparison runs.

Test Procedure: In preparation for the corrosion tests hereinafter described, coupons were cut from 2-3/8" O.D.

N80 steel tubing. The coupons were cleaned by tumbling in aluminum oxide grit after which they were exposed to an ultrasonic trichloroethylene bath, rinsed in acetone, dried, and stored in a desiccator. In carrying out the tests, the coupon was placed in the test solution in an autoclave and the test temperature and pressure were established as rapidly as was practical. Stated test times are the times for which the coupon was exposed to the solution of the specified temperature and pressure. All tests were carried out under static conditions, i.e. without agitation, at 1000 psi. After permitting the test bath to cool to about 1500 F, the coupon was removed from the bath, rinsed in acetone, and washed in inhibited 15% aqueous HCI for about 3-4 minutes with agitation to dissolve the iron sulfide film which forms during the test.The coupon was then washed in water, scrubbed with a brass brush and pumice soap, heated in hot water to accelerate acetone evaporation, rinsed in acetone, dried, cooled, and weighed.

In all corrosion tests, the various additives in the quantities stated were added to 100 ml of the brine. In all tables, "Corrosion Rate" is expressed as pounds per square foot per the stated test time.

"Percent Inhibition" is the following quantity: Corrosion rate with no inhibitor-Corrosion rate of test solution x100.

Corrosion rate with no inhibitor Various quaternary salt solutions were prepared and used as follows: Prep. A: Decylquinolinium bromide (DQBr) Prep. B: Dodecylquinolinium bromide (DodQBr) Prep. C: Tetradecylpyridinium bromide (TdPBr) Prep. D: Hexadecylpyridinium bromide (HDPBr) Prep. E: Decylpyridinium bromide (DPBr) Prep. F: Dodecylpyridinium bromide (DodPBr) Prep. G: Alkyl substituted tetradecylpyridinium bromide (AlkTdPB) Prep. H: Hexylpyridinium bromide (HPBr) Prep. I: Octylpyridinium bromide (OPBr) Prep. J: 0.4:1 OPBr:Ammonium thiocyanate Prep. K: 0.26:1 OPBr:Ammonium thiocyanate Several series of corrosion tests summarized in the following tables were carried out.

Series One Aqueous Brine: 52 weight percent CaBr2 Temperature: 3500F Time: 68 hours Inhibitor Oxygen Corrosion Run Qua ternary Compound Thio Compound Other Scavenger Rate 1 -- -- -- .0163; .01 2 0.5 mlPrepE(DPBr) - - 0.0187 3 0.5 ml Prep E (DPBr) 0.3 9 thiourea - - 0.0040 4 0.5 ml Prep E (DodPBr) - - 0.0181 5 0.5 ml Prep F (DodPBr) 0.3 9 thiourea - - 0.0052 6 0.5 9 Prep C (TdPBr) - - 0.0152 7 0.5 g Prep C (TdPBr) 0.3 g thiourea - - 0.0062 8 0.5 9 Prep D (HdPBr) - - 0.0167 9 0.5 g Prep D (HdPBr) 0.3 g thiourea - - 0.0099 10 0.5 ml Prep A (DQBr) 0.3 9 thiourea - - 0.0098 11 0.5 ml Prep B (DodQBr) 0.3 9 thiourea - - 0.0082 12 Note 1 0.3 g thiourea Note 1 - 0.0067 13 Note 2 0.3gthiourea Note 2 - 0.0101 14 0.5 ml Prep G (AlkTdPB) 0.3 g thiourea - - 0.0053 15 - 0.3 g NH4SCN 0.5 ml - 0.0056 Corexit 7720 16 - 0.3 g NH4SCN 1.0 ml - 0.0045 Corexit 7720 17 0.25 ml Prep E (DPBr) 0.3 9 NH4SCN - - 0.0039 18 0.5 ml Prep E (DPBr) 0.3 9 NH4SCN - - 0.0039 19 0.25 ml Prep H (HPBr) 0.3 9 NH4SCN - - 0.0061 20 0.5 ml Prep H (HPBr) 0.3 g NH4SCN - - 0.0062 21 025 ml Prep I (OPBr) 0.3 9 NH4SCN - - 0.0049 22 0.5 ml Prep I (OP Br) 0.3 g NH4SCN - - 0.0045 23 0.5 ml Prep G (AlkTdPB) 0.3 g NH4SCN - - 0.0048 24 0.5 ml Prep E (DPBr) 0.3 g NH4SCN - 0.3 9 0.0098 Na2S204 25 0.3 9 NH4SCN - - 0.0069 26 - - - 0.3 g 0.0091 Na2S204 27 - - - 0.6 9 0.0161 Na2S204 Notes: (1) 0.5 ml of 1 part isopropanol, 4 parts the reaction product of 1 -dodecyl bromide and triethyl amine.

(2) 0.5 ml of 1 part isopropanol, 4 parts the reaction product of 1 -dodecyl bromide and triethanol amine.

(3) The corrosion rates for Runs 2-14 are best compared with the 0.0163 rate for Run 1, and the rates for Runs 1 5-27 with the 0.0137 rate for the rerun of Run 1 since those groups of runs were made on the same days, respectively.

Series Two Aqueous Brine: 52 weight percent CaBr2 Temperature: 3500F Time: 16 hours lnhibitor Oxygen Corrosion Run Quaternary Compound Thio Compound Other Scavenger Rate 28 0.1 ml diluted Prep E(1) 0.3 g thiourea - - 0.0040 29 0.25 ml diluted Prep E(1) 0.3 g thiourea - - 0.0037 30 0.5 ml diluted Prep E(1) 0.3 9 thiourea - - 0.0025 31 1.0 ml diluted Prep E(1) 0.3 9 thiourea - - 0.0025 32 0.25 ml Prep E (DPBr) 0.3 9 thiourea - - 0.0026 33 0.25 ml Prep E (DPBr) 0.05 9 thiourea - - 0.0034 34 0.25 ml Prep E (DPBr) 0.1 g thiourea - - 0.0025 35 0.25 ml Prep E (DPBr) 0.2 9 thiourea - - 0.0028 36 0.5 ml Prep H (HPBr) 0.3 g thiourea - - 0.0033 37 0.5 ml Prep I (OPBr) 0.3 g thiourea - - 0.0028 38 0.5 ml Prep F (DodPBr) 0.3 9 thiourea - - 0.0026 39 0.5 ml Prep C (TdPBr) 0.3 g thiourea - - 0.0028 40 See Note 1, Series one 0.3 g thiourea See Note 1, - 0.0033 Series One 41 - - - - 0.0054 Note: (1) 1 ml Prep E (DPBr) diluted with 9 ml water.

Series Three Aqueous Brine: 852 9 CaCI2 dissolved in 2500 ml of 52% CaBr2 Temperature: 3500F Time: 16 hours Inhibitor Oxygen Corrosion Run Quaternary Compound Thio Compound Other Scavenger Rate 42 - - - - 0.0079 43 - 2 ml Baroid - 0.0072 1400 44 - 1 ml Corexit - 0.0066 7720 45 0.5 ml Prep E (DPBr) 0.3 9 NH4SCN - 0 0.0030 46 0.5 ml Prep E (DPBr) 0.6gNH4SCN - - 0.0031 47 Note 1 0.3 g NH4SCN Note 1 - 0.0040 48 Note 1 0.6 9 NH4SCN Note 1, - 0.0043 49 See Note 2, Series One 0.3 g NH4SCN See Note 2, - 0.0026 Series One 50 See Note 2, Series One 0.6 9 NH4SCN See Note 2, - 0.0026 Series One 51 0.5 ml Prep F (HdPBr) 0.3 9 NH4SCN - - 0.0028 52 0.5 ml Prep F (HdPBr) 0.6 g NH4SCN - - 0.0029 53 - 0.6 9 NH4SCN - - 0.0038 Note: (1) 0.5 9 of 1 part isopropanol, 4 parts the reaction product of 1-dodecyl bromide and triethyl amine.

Series Four Aqueous Brine: 852 g CaCI2 dissolved in 250 ml of 52% CaBr2 Temperature: 3500F Time: 118 hours Corrosion Percent Run Inhibitor Rate Inhibition 54 - 0.0202 Control 55 0.1 ml Prepj (0.4:1 OPBr:NH4SCN) 0.0176 13 56 0.2 ml Prep J (0.4:1 OPBr:NH4SCN) 0.0150 26 57 0.4 ml Prep J (0.4:1 OPBr:NH4SCN) 0.0101 50 58 0.6 ml Prep J (0.4:1 OPBr:NH4SCN) 0.0086 57 59 0.1 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0180 11 60 0.2 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0128 37 61 0.4 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0095 53 62 0.6 ml Prep K (0.26:1 OPBr::NH4SCN) 0.0078 61 63 0.2 ml Baroid 1400 0.0167 17 64 0.4 ml Baroid 1400 0.0155 23 65 0.6 ml Baroid 1400 0.0186 8 66 0;2 ml Corexit 7720 0.0168 17 67 0.4 ml Corexit 7720 0.0180 11 Series Five Aqueous Brine: 852 g CaCI2 dissolved in 250 ml of 52% CaBr2 Temperature: 3000F Time: 72 hours Corrosion Percent Run Inhibitor Rate Inhibition 68 - 0.0101 Control 69 0.1 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0072 29 70 0.2 ml Prep K (0.26:1 OP8r:NH4SCN) 0.0049 51 71 0.4 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0027 73 72 0.6 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0026 73 73 0.1 ml Baroid 1400 0.0100 1 74 0.2 ml Baroid 1400 0.0085 16 75 0.4 ml Baroid 1400 0.0081 20 76 0.1 ml Corexit 7720 0.0091 10 77 0.2 ml Corexit 7720 0.0067 34 78 0.4 ml Corexit 7720 0.0050 50 79 0.1 mlDowelIA1631 0.0106 -5 80 0.2 ml Dowell A163() 0.0096 5 81 0.4 ml Dowell Al 63(1? 0.0078 23 Note: (1) Dowell A 163 is an inhibitor of the imidazoline type.

Series Six Temperature: 350 F Time: 72 hours Corrosion Percent Run Brine Inhibitor Rate Inhibition 82 19%ZnBr2, 46%CaBr2 0.0245 Control 83 19% ZnBr2, 46% CaBr2 0.4 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0035 86 84 29% ZnBr2, 41% % Cabr2 CaBr2 0.0207 Control 85 29%ZnBr2,41%CaBr2 0.4 ml Prep K (0.26:1 OPBr:NH4SCN) 0.0043 79 86 57% ZnBr2, 20% CaBr2 0.1494 Control 87 57% ZnBr2, 20% CaBr2 0.4 ml Prep K (0.26:1 OPBr: NH4SCN) 0.0521 65

Claims (21)

Claims

1 A method of reducing the corrosive effect of aqueous brine on ferrous metal surfaces which are contacted by the brine, comprising adding to the brine a corrosion inhibiting quantity of a sulfur compound wherein the oxidation state of the sulfur is zero or less, said sulfur compound being uniformly dispersible in the brine.

2. A method as claimed in claim 1, wherein the sulfur compound is employed in an amount of at least 0.3 grams per liter of brine.

3. A method as claimed in claim 1 or claim 2, wherein the sulfur compound is a water soluble thiocyanate or thioamide.

4. A method as claimed in claim 3, wherein the sulfur compound is ammonium thiocyanate or thiourea.

5. A method as claimed in any one of the preceding claims, wherein the brine contains at least one of calcium chloride, calcium bromide, calcium iodide, zinc chloride, zinc bromide, and zinc iodide.

6. A method as claimed in any one of the preceding claims wherein an effective amount of at least one quaternary pyridinium, quinolinium, and isoquinolinium salt is added to the brine to further reduce the corrosive effect of the-brine, said quaternary salt being selected so as to be sufficiently soluble in the brine so that an effective amount can be dissolved in the brine.

7. A method as claimed in claim 6, wherein the combined weight of said sulfur compound plus any quaternary salt present does not exceed 3 grams per liter.

8. A method as claimed in claim 6 or claim 7, wherein the quaternary salt is employed in an amount of from 0.1 to 10 parts per part by weight of the sulfur compound.

9. A method as claimed in claim 7 or claim 8, wherein the total concentration of the sulfur compound and the quaternary salt is from 0.5 to 2 grams per liter of brine, and the weight ratio of said quaternary compound to sulfur is from 0.125:1 to 4:1.

10. A method as claimed in any one of claims 6 to 9, wherein the quaternary salt has the formula

where R is an alkyl radical of 1-20 carbon atoms, a benzyl radical, or an alkylated benzyl radical wherein the aromatic ring has one or more alkyl substituents totalling 1-20 carbon atoms, each R' is independently a hydrogen atom or an alkyl or alkoxy radical of 1-6 carbon atoms, and X is an anionic radical.

11. A method as claimed in claim 10, wherein R is an alkyl radical of 6-16 carbon atoms.

12. A method as claimed in claim 10 or claim 11, wherein X is bromine.

13. A method as claimed in any one of claims 10 to 12, wherein each R' is hydrogen.

14. A method as claimed in claim 10, wherein the quaternary compound is a N-octyl pyridinium bromide.

1 5. A method as claimed in any one of the preceding claims, wherein an effective amount of a water soluble cobalt salt is added to the brine to still further reduce the corrosive effect of the brine.

1 6. A method as claimed in claim 1 substantially as hereinbefore described with reference to any one of Runs 3, 5, 7, 9 to 25, to 40, 45 to 53, 55 to 62, 69 to 72, 83, 85 and 87.

1 7. Brine to which has been added a corrosion inhibiting quantity of a sulfur compound wherein the oxidation state of the sulfur is zero or less, said sulfur compound being uniformly dispersible in the brine.

18. A well treating operation involving the use of brine as claimed in claim 17.

1 9. A separation process, wherein solids of different densities are separated by flotation, involving the use of brine as claimed in claim 1 7.

20. Petroleum, or a petroleum derivative, which has been recovered as a result of a well treating operation as claimed in claim 1 8.

21. Ferrous metal having a protective iron sulfide film thereon, which fill has been provided by contacting a ferrous metal surface with brine as claimed in claim 1 7.