Liquid Inhibitor Composition And A Method For Its Preparation And Application As A Heavy Brine Corrosion Control

Abstract

A composition useful as corrosion inhibitor formulation for application in heavy brine systems, comprising at least one imidazoline; at least one sulfur synergist; at least one phosphate ester. In a preferred embodiment, the composition comprises additionally formulation bonding surfactant; and/or at least one solvent system.

Claims

1. A process for inhibiting corrosion in a heavy brine having a density of 1.15 to 2.65 g/cm.sup.3, comprising the step of adding a composition comprising at least one imidazoline, at least one sulfur synergist, and at least one phosphate ester, to the heavy brine having a density of 1.15 to 2.65 g/cm.sup.3.

2. The process according to claim 1, wherein the at least one imidazoline corresponds to formula III ##STR00024## wherein R is —H, —C.sub.2H.sub.4NH.sub.2, —C.sub.2H.sub.4OH, —(C.sub.2H.sub.4NH).sub.x—C.sub.2H.sub.4NH.sub.2, x is a number from 0 to 200 R1 is a C.sub.3 to C.sub.29 aliphatic hydrocarbon group.

3. The process according to claim 2, wherein R1 is a C.sub.7 to C.sub.21 hydrocarbon group.

4. The process according to claim 2, wherein R1 is alkyl or alkenyl.

5. The process according to claim 1, wherein the at least one imidazoline is formed by a reaction of the compounds in molar ratios selected from the group consisting of 1:1 (molar ratio) TOFA/DETA imidazoline, 2:1 TOFA/DETA amido imidazoline, 1:1 TOFA/TETA imidazoline, 2:1 TOFA/TETA amido-imidazoline, 2:1 TOFA/TETA bisimidazoline, 1:1 TOFA/TEPA imidazoline, 2:1 TOFA/TEPA amido imidazoline, 2:1 TOFA/TEPA bis imidazoline, 3:1 TOFA/TEPA amido bisimidazoline, 1:1 TOFA/AEEA imidazoline, 2:1 TOFA/AEEA amido imidazoline, 1:1 TOFA/polyamine imidazoline, 2:1 TOFA/polyamine imidazoline, 2:1 TOFA/polyamine amido imidazoline, 2:1 TOFA/polyamine bisimidazoline, 3:1 TOFA/TEPA polyamine amido bisimidazoline, 1:1 Soya/DETA imidazoline, 2:1 Soya/DETA amido-imidazoline, 1:1 Soya/TETA imidazoline, 2:1 Soya/TETA amido-imidazoline, 2:1 Soya/TETA bismidazoline, 1:1 Soya/TEPA imidazoline, 2:1 Soya/TEPA amido imidazoline, 2:1 Soya/TEPA bisimidazoline, 3:1 TOFA/TEPA amido bisimidazoline, 1:1 Soya/AEEA imidazoline, 2:1 Soya/AEEA amidoimidazoline, 1:1 Soya/polyamine imidazoline, 2:1 Soya/polyamine imidazoline, 2:1 Soya/polyamine amido imidazoline, 2:1 Soya/polyamine bisimidazoline, 1:1 Tallow/DETA imidazoline, 2:1 Tallow/DETA amido-midazoline, 1:1 Tallow/TETA imidazoline, 2:1 Tallow/TETA amido-imidazoline,2:1 Tallow/TETA bismidazoline, 1:1 Tallow/TEPA imidazoline, 2:1 Tallow/TEPA amido imidazoline, 2:1 Tallow/TEPA bisimidazoline, 3:1 Tallow/TEPA amido bisimidazoline, 1:1 Tallow/AEEA imidazoline, 2:1 Tallow/AEEA amidoimidazoline, 1:1 Tallow/polyamine imidazoline, 2:1 Tallow/polyamine imidazoline, 2:1 Tallow/polyamine amido imidazoline, 2:1 Tallow/polyamine bisimidazoline and 3:1 Tallow/TEPA poly amine amido bisimidazoline.

6. The process according to claim 1, wherein the at least one sulfur synergist is selected from the group consisting of compounds comprising sulfur.

7. The process according to claim 1, wherein the at least one sulfur synergist is selected from the group consisting of thioglycolic acid, sodium thiosulfite, ammonium thiosulfite, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, potassium thiosulfite, thiourea, sodium thiocyanate, ammonium thiocyanate, and calcium thiocyanate, sodium thioglycolate, ammonium thioglycolate, 1,2-diethylthiourea, propylthiourea, 1,1-diphenylthiourea, thiocarbanilide, 1,2-dibutylthiourea, dithiourea thioacetamide, thionicotimide, or thiobenzamide, 2-Mercpatoethanol, 3-(Methylthio)propanal, thioacetic acid, cyste-amine, 3-Chloro-1-propanethiol, 1-mercapto-2-propanol, 2,3-Dimercapto-1-propanol, 2-Methoxyethane-thiol, 3-Mercapto-1-propanol, 2,3-Dimercapto-1-propanol, 1-Thio-glycerol, 1,3-Propane-dithiol, mercaptosuccinic acid, Cysteine, N-Carbomoyl-L-cysteine, N-Acetylcysteamine, 4-Mercapto-1-butanol, 1-Butanedithiol, 1,4-Butanedithiol, 2,2′-Thiodietanethiol, 4-Cyano-1-butanethiol, Cyclopantanethiol, 1,5-Pentanedithiol, 2-Methyl-1-butanethiol, 2,3,5,6-Tetrafluorobenzenethiophenol, 4-Chlorothiophenol, 2-Mercaptophenol, Thiophenol, Cyclohexylthiol, 4-Mercaptobenzoic acid, Thiosalicylic acid, 2-Ethylhexane thiol and compounds of the formula C.sub.nH.sub.2n+1SH (n=1 to 10).

8. The process according to claim 1, wherein the at least one phosphate ester is of the formula: ##STR00025## wherein Ra, Rb and Rc are each H or a hydrocarbon group which may contain oxygen or nitrogen atoms with a carbon atom number ranging from 1 to 49.

9. The process according to claim 8, wherein at least one of Ra, Rb and Rc are ethoxy groups.

10. The process according to claim 8, wherein the carbon atom number in the hydrocarbon group ranges from 4 to 30.

11. The process according to claim 8, wherein at least one of Ra, Rb and Rc is selected from the group consisting of alkyl or alkenyl groups.

12. The process according to claim 8, wherein Ra, Rb and Rc are terminated by a hydrogen, hydroxyl, benzyl or carboxylic acid group.

13. The process according to claim 8, wherein at least one of Ra, Rb and Rc is substituted with a non-terminal carboxyl, hydroxyl or secondary amine group.

14. The process according to claim 1, wherein the composition further comprises at least one solvent system wherein the at least one solvent system is selected from the group consisting of water, monohydrate alkyl alcohols with 1 to 8 carbon atoms, dihydric alcohols having 2 to 6 carbon atoms and C.sub.1 to C.sub.6 alkyl ethers of the alcohols.

15. The process according to claim 14, wherein the solvent system is selected from the group consisting of water, methanol, ethanol, monoethylene glycol, triethylene glycol, 2-butoxyethanol, 2-ethylhexanol, isopropanol, pentanol, butanol and mixtures thereof.

16. The process according to claim 1, wherein the composition further comprises a bonding surfactant according to the formula ##STR00026##

17. The process according to claim 1, wherein the composition further comprises bonding surfactant selected from the group consisting of nonyl phenol ethoxylates with 4 to 100 ethoxy groups.

18. The process according to claim 1, wherein the composition further comprises bonding surfactant selected from the group consisting of ethoxlated alcohols according to
R4-O-(A-O).sub.x—H wherein R4 is an aliphatic C.sub.8 to C.sub.18 hydrocarbon residue, A is an ethylene group, and x is a number from 2 to 100.

19. The process according to claim 18, wherein R4 is alkyl or alkenyl and may either be straight chain or branched.

20. The process according to claim 18, wherein R4 comprises from 12 to 16 carbon atoms.

21. The process according claim 18, wherein x is a number from 7 to 40.

22. The process according to claim 1, wherein the composition further comprises bonding surfactant selected from the group consisting of ethoxylated amines having 6 to 18 carbon atoms and 2 to 100 ethoxy groups.

23. The process according to claim 1, wherein the concentration of the at least one imidazoline is from 1 to 20 wt.-%.

24. The process according to claim 1, wherein the concentration of the at least one sulfur synergist is from 1 to 10 wt.-%.

25. The process according to claim 1, wherein the concentration of the at least one phosphate ester is 1 to 30 wt.-%.

26. The process according to claim 16, wherein the concentration of the at least one bonding surfactant is from 1 to 20 wt.-%.

27. The process according to claim 14, wherein the concentration of the at least one solvent system is from 20 to 80 wt.-%.

28. The process according to claim 1, wherein the heavy brine is an aqueous solution comprising at least one salt selected from the group consisting of NaCl, CaCl.sub.2, Ca(NO.sub.3).sub.2, KCl, CaBr.sub.2, ZnBr, ZnI.sub.2, and mixtures thereof.

29. The process according to claim 1, wherein the density of the heavy brine is from 1.4 to 2.65 g/cm.sup.3.

30. (canceled)

31. The Use or process according to claim 1, wherein from 100 to 10,000 mg/L of the composition is added to the heavy brine having a density of 1.15 to 2.65 q/cm.sup.3.

Description

EXAMPLES

[0148] If not stated otherwise, references to % or ppm mean volume—% or volume—ppm throughout this specification.

[0149] In order to clearly and demonstrably illustrate the current invention, several examples have been presented below, these are however, non-limiting and have been specifically chosen to show those skilled in the art, the logic taken to arrive at the final formulations.

[0150] In order to evaluate the corrosion inhibition efficacy of the formulations, two different test methods were employed: rotating cylinder electrode (RCE) tests and high pressure, high temperature (HPHT) autoclave weight loss tests. For all testing displayed the following brine compositions were used:

Fully saturated Ca(NO.sub.3).sub.2 brine (Brine 1), salt concentration Ca(NO.sub.3).sub.2.4H.sub.2O 2,126 g/L (approximately 10.8 pounds per gallon—hereafter referred to as PPG or 1.29 g/cm.sup.3);
super saturated Ca(NO.sub.3).sub.2 brine (Brine 2), salt concentration Ca(NO.sub.3).sub.2.4H.sub.2O 2,785 g/L (approximately 12.5 PPG or 1.49 g/cm.sup.3);
fully saturated CaCl.sub.2 brine (Brine 3), salt concentration CaCl.sub.2.2H.sub.2O 667 g/L (approximately 11.6 PPG or 1.38 g/cm.sup.3);
super saturated CaCl.sub.2/Ca(NO.sub.3).sub.2 brine (Brine 4), salt concentration CaCl.sub.2.2H.sub.2O 667 g/L and Ca(NO.sub.3).sub.2.4H.sub.2O 2,050 g/L (approximately 13.5 PPG or 1.61 g/cm.sup.3).

[0151] The only gas used during testing was oxygen free nitrogen. RCE testing was conducted open to air to simulate high O.sub.2 presence (which would be the case in the real life, field application). Static autoclave testing utilized a N.sub.2 blanket that was purged into the head space four times before final pressurization but the brine was not purged of oxygen and saturation can be assumed.

[0152] The metallurgy of the coupons tested was C1018 carbon steel for RCE testing and coupons manufactured from P110 carbon steel were used in HPHT autoclave testing. Coupons were polished mechanically using 320 grit silicon-carbide (SiC) paper, 400 grit SiC paper, then 600 grit SiC paper and rinsed with water then acetone prior to testing.

[0153] The rotating cylinder electrode (RCE) tests were conducted in Pyrex™ glass reaction kettles that were heated to 185° F. The testing solution was comprised of 900 mL of heavy brine. The electrode rotation rate was set at 2000 RPM, which generated a wall shear stress of 7.0 Pa. Linear polarization resistance (LPR) measurements were made with a Gamry electrochemical measurement system. The working electrode was made of a 1018 carbon steel (CS) cylinder with a surface area of 3.16 cm.sup.2. A Hastelloy C276 electrode was used as a pseudo-reference, and a graphite rod was used as the counter electrode. The corrosion inhibitors were added based on the brine volume after the baseline corrosion rate was monitored for approximately 1.5 hours. Upon completion of the tests, the electrodes were cleaned in an inhibited acid bath according to ASTM G1 C.3.5, and weighed to 0.1 mg.

[0154] HPHT static autoclave tests were used to simulate the zero shear conditions for the purpose of evaluating system corrosivity as well as inhibitor performance. The test solution consisted of 800 mL of heavy brine. The head space was cleared of oxygen using 100% nitrogen gas four times before final pressurization into the autoclaves. Two weight loss corrosion coupons fixed on a PTFE cage were used in each autoclave. General corrosion rates were calculated by weight loss measurement according to ASTM G170 (and associated standards referenced therein). Test conditions were constant in all examples with a temperature of 300° F. and 350° F. at a constant pressure of 500 psi; the inhibitors were dosed in at a variety of dose rates ranging from 100 to 300 ppm (based on each inhibitor component) and the tests were run for 7 days.

[0155] The surfaces of the electrodes and coupons were analyzed after each test for pitting potential by using a high powered metallurgical microscope. The reflected light microscope was capable of analyzing samples up to 1,000-times magnification. The microscope was mounted with a camera and included brightfield, darkfield, and Differential Interface Controls (DIC) modes.

Example 1: Reference Examples

[0156] Uninhibited tests were performed first of all in order to understand the baseline corrosion rate; the following readings, displayed in Table 1, were obtained in the static HPHT autoclave tests at 300 and 350° F.:

TABLE-US-00002 TABLE 1 Uninhibited corrosion rate results on heavy brines Heavy Brine 300° F. (mpy) 350° F. (mpy) No. Brine 1 - 10.8 PPG Ca(NO.sub.3).sub.2 8.4 14.8 1.1 Brine 2 - 12.5 PPG Ca(NO.sub.3).sub.2 11.5 20.6 1.2 Brine 3 - 11.6 PPG CaCl.sub.2 12.6 26.8 1.3 Brine 4 - 13.5 Ca(NO.sub.3).sub.2/CaCl.sub.2 25.4 48.2 1.4

[0157] Individual components were then tested to determine further baseline effects. Components were selected from groups 1, 2, 3, and 4 above; namely 1:1 tallow/DETA imidazoline (component Group 1), thioglycolic acid (component Group 2), poly(oxy-1,2-ethanediyl), alpha-isotridecyl-omega-hydroxy-, phosphate (component Group 3), and alkyl (C.sub.6) morpholine (component Group 4).

[0158] The results of the harshest brine 4 (13.5 Ca(NO.sub.3).sub.2/CaCl.sub.2) at 350° F. are shown below in Table 2. It can be seen that only small decreases in corrosion rate were obtained for the single components and significant corrosion still occurred. Microscopic inspection of the coupons yielded a wholly unacceptable amount of pitting corrosion with frequent pits being >10 μm deep.

TABLE-US-00003 TABLE 2 Corrosion rates for heavy brines inhibited with single components at 350° F. Com- Corrosion Component Component Component ponent Rate Group 1 Group 2 Group 3 Group 4 (mpy) (ppm) (ppm) (ppm) (ppm) No. 48.2 0 0 0 0 1.5 46.1 250 0 0 0 1.6 42.3 500 0 0 0 1.7 38.9 0 250 0 0 1.8 32.6 0 500 0 0 1.9 24.2 0 0 250 0 1.10 19.8 0 0 500 0 1.11 43.5 0 0 0 250 1.12 42.1 0 0 0 500 1.13

Example 2: Three Component System

[0159] Work continued on three component systems with the aim of identifying the most synergistic relationship between the components. Again work was performed on the harshest brine 4 (13.5 Ca(NO.sub.3).sub.2/CaCl.sub.2) at 350° F. are shown below in Table 3. Based on these results one can surprisingly see the phosphate ester component leads to high corrosion inhibitor performance, the phosphate ester itself is not a great corrosion inhibitor and it is surprisingly synergistic with the other components within the three component blend. This is not however a linear relationship and various synergistic and antagonistic relationships can be discerned in the data; [0160] 1. When a phosphate ester was absent the corrosion rates were in general much higher; [0161] 2. When an imidazoline was absent the corrosion rates were high; [0162] 3. The uniqueness and high performance of corrosion inhibiting composition is related to the understanding of the relationships between components and identifying the most synergistic ratios.

TABLE-US-00004 TABLE 3 Corrosion rates for heavy brine 4 inhibited with three component systems at 350° F. Com- Corrosion Component Component Component ponent Rate Group 1 Group 2 Group 3 Group 4 (mpy) (ppm) (ppm) (ppm) (ppm) No. 48.2 0 0 0 0 2.1 12.1 100 100 100 0 2.2 34.2 100 100 0 100 2.3 28.9 100 0 100 100 2.4 9.8 200 200 200 0 2.5 32.0 200 200 0 200 2.6 24.9 200 0 200 200 2.7 14.6 200 200 100 0 2.8 9.9 200 100 200 0 2.9 9.4 100 200 200 0 2.10 31.2 200 200 0 100 2.11 34.2 200 100 0 200 2.12 33.7 100 200 0 100 2.13 23.4 200 0 200 100 2.14 29.6 200 0 100 200 2.15 24.8 100 0 200 200 2.16 18.9 0 200 200 100 2.17 26.1 0 200 100 200 2.18 22.8 0 100 200 200 2.19

Example 3: Use of Phosphate Ester in a Four Component System

[0163] The use of phosphate ester in Example 2 led to high corrosion inhibition performance in the three component system. More specific work was performed on phosphate ester chemistries in order to fully understand and leverage this performance. Testing was performed on a great many different phosphate ester chemistries in order to identify the most important types for higher performance corrosion inhibition of heavy brines. Again work was performed on the harshest brine 4 (13.5 Ca(NO.sub.3).sub.2/CaCl.sub.2) at 350° F. are shown below in Table 4. The results display the data from three different phosphate ester chemistries, namely Phos. Ester 1, which is phosphoric acid 2-ethylhexylester; Phos. Ester 2, which is poly(oxy-1,2-ethanediyl), alpha-isotridecyl-omega-hydroxy-, phosphate; Phos. Ester 3, which is 2-Ethyl hexyl mono/di phosphoric acid ester, acid.

[0164] Testing was performed in a four component system consisting of a 1:1 tallow/DETA imidazoline (component group 1), thioglycolic acid (component group 2), phosphate ester (see above for the 3 different types tested) (component group 3), and alkyl (C.sub.6) morpholine (component group 4). The following conclusions can be drawn: [0165] 1. It can be seen that moving to the four component system resulted in a step change in corrosion inhibition performance with results being consistently below 10 mpy; [0166] 2. The presence of the phosphate ester enhances the formulation disproportionately with respect to the other components; however the correct level of phosphate ester is required because in some instances increasing the amount of phosphate ester decreases performance as one begins to move out of the synergistic zone with other components in the formation.

TABLE-US-00005 TABLE 4 Corrosion rates for heavy brine 4 inhibited with four component systems focusing on the phosphate ester chemistry at 350° F. Corrosion Component Component Phos Phos Phos Component Rate Group 1 Group 2 Ester 1 Ester 2 Ester 3 Group 4 (mpy) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) No. 48.2 0 0 0 0 0 0 3.1 8.5 100 100 100 0 0 100 3.2 3.6 100 100 0 100 0 100 3.3 12.8 100 100 0 0 100 100 3.4 6.4 100 100 200 0 0 100 3.5 2.9 100 100 0 200 0 100 3.6 11.2 100 100 0 0 200 100 3.7 7.8 100 100 300 0 0 100 3.8 3.4 100 100 0 300 0 100 3.9 10.8 100 100 0 0 300 100 3.10 8.9 200 200 100 0 0 200 3.11 2.8 200 200 0 100 0 200 3.12 11.4 200 200 0 0 100 200 3.13 4.6 200 200 200 0 0 200 3.14 2.1 200 200 0 200 0 200 3.15 8.7 200 200 0 0 200 200 3.16 4.5 200 200 300 0 0 200 3.17 2.0 200 200 0 300 0 200 3.18 8.4 200 200 0 0 300 200 3.19

Example 4: Five Component System

[0167] The following components have been tested to show the synergism that is present in the blends once a fifth component is introduced: [0168] 1. Imidazoline: this is a primary component of the corrosion inhibitor formulations (component 1), as described above there are many commercially available imidazoline chemistries; in these formulations specified, a 1:1 tallow/DETA imidazoline was used throughout; [0169] 2. Morpholine: this is used as a formulation bonding compound (component 4a) and can comprise different species of morpholine and its derivatives; in these formulations specified, an alkyl (C.sub.6) morpholine was used throughout; [0170] 3. Phosphate ester: this is another primary component of the corrosion inhibitor formulations (component 3) and can comprise different species of phosphate ester; in these formulations specified, poly(oxy-1,2-ethanediyl), alpha-isotridecyl-omega-hydroxy-, phosphate was used throughout; [0171] 4. Thioglycolic acid: this is a sulfur synergist and is another preferred embodiment of the corrosion inhibitor (component 2); [0172] 5. Ethoxylated amine: these class of molecules are used as bonding surfactants (component 4) and while there can be a very wide range of molecules used in the invention (as described above); in these formulations specified, a coconut fatty acid ethoxylate with 10 moles of EO was used throughout;

[0173] The description of the blends tested and the results of the testing can be seen in Table 5. Once again all testing displayed was performed on the harshest brine 4 (13.5 Ca(NO.sub.3).sub.2/CaCl.sub.2) at 350° F. It can be seen by one skilled in the art that a design of experiments (DOE) approach was taken to derive the optimum ratios of the five components in this example. This is necessary because of the complex, multi-order relationship that exists between the components of the corrosion inhibitor system and in order to resolve the most optimum synergies DOE should be used to minimize the time to realize the results.

[0174] Corrosion rates were all generally around 1.0 mpy but in some extra-ordinary cases were as low as 0.1 mpy when further adjusting the components to optimum and synergistic concentrations.

TABLE-US-00006 TABLE 5 Corrosion rates for heavy brine 4 inhibited with five component systems at 350° F. Corrosion Imida- Thioglycolic Phos Mor- Ethox. Rate zoline Acid Ester pholine Amine (mpy) (ppm) (ppm) (ppm) (ppm) (ppm) No. 48.2 0 0 0 0 4.1 1.1 500 500 300 200 0 4.2 1.0 500 500 300 0 200 4.3 0.2 500 500 300 0 200 4.4 0.9 400 500 400 200 0 4.5 0.8 400 500 400 0 300 4.6 0.2 400 500 400 0 300 4.7 1.1 300 600 300 0 500 4.8 1.2 300 600 300 500 0 4.9 0.9 300 600 300 0 500 4.10 0.1 300 600 300 500 0 4.11 0.5 200 500 500 300 0 4.12 0.6 200 500 500 0 300 4.13 0.6 200 500 500 300 0 4.14 0.5 200 500 500 0 300 4.15

Example 5: Speed of Inhibition

[0175] Yet another unique feature of the disclosed corrosion inhibitors is the speed to achieve inhibition. When reviewing the prior art, and testing formulations constructed from the prior art, it is clear that these prior art inventions take several days to achieve equilibrium and reduce the corrosion rate to the final claimed level. It is clearly more desirable to achieve a low corrosion rate as quickly as possible, thus enabling better protection of equipment that comes into contact with heavy brine during oilfield operations.

[0176] The currently disclosed corrosion inhibitors have been designed with this in mind and the previously described RCE methodology was able to test and determine the speed to achieve inhibition.

[0177] Several corrosion inhibitors were screened in RCE tests in order to determine the speed of inhibition. The LPR results for the RCE tests are shown in Table 6.

TABLE-US-00007 TABLE 6 RCE Corrosion Rate and % Inhibition Corrosion Rate (mpy) Protection (%) Base- 2 hr after Final 2 hr after Final line CI Dosage 3 hr CI Dosage 3 hr Product- (mpy) (mpy) (mpy) (mpy) (mpy) No. Chemical A 90.9 33.1 4.3 63.54 95.31 5.1 Chemical B 238.5 49.9 20.4 79.06 91.44 5.2 Chemical C 129.8 20.5 9.6 84.18 92.59 5.3 Chemical D 60.6 36.5 27.0 39.78 55.41 5.4 Chemical E 58.4 34.2 26.9 41.55 54.02 5.5 Chemical A corresponds to # 3 from Table 7. Chemical B corresponds to # 7 from Table 7. Chemical C corresponds to # 1 from Table 7. Chemical D corresponds to # 8 from Table 7. Chemical E corresponds to # 2 from Table 7.

[0178] After the addition of 150 ppm of corrosion inhibitor, corrosion rates dropped to below 10 mpy for Chemical A after just a few hours of testing. Ultimately, Chemical A was able to yield over 95% inhibition. While Chemicals A, B, and C all showed strong final inhibition rates of over 90%, Chemical A performed the strongest as it brought the corrosion rate to 4.3 mpy and a final inhibition rate of 95.31%. All chemicals, even the worse performing from the 5 displayed in this example reduced the corrosion rate dramatically after just 3 hours of testing showing the very fast effect and differentiating corrosion film formation of this invention.

[0179] Examples of the heavy brine corrosion inhibitor formulations illustrating different compositional aspects of this invention are listed in Table 7 in their final solvent system.

TABLE-US-00008 TABLE 7 Final invention formulation examples Formulation #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14 Imidazoline 5 5 5 4 4 4 3 3 3 3 2 2 2 2 from Example 4 [wt.-%] Morpholine 2 0 0 2 0 0 0 5 0 5 3 0 3 0 [wt.-%] Phosphate Ester 3 3 3 4 4 4 3 3 3 3 5 5 5 5 from Example 4 [wt.-%] NP9 0 5 5 0 4 4 0 3 0 3 5 0 0 5 [wt.-%] Alcohol ethoxylate 5 0 0 5 0 0 3 0 3 0 0 5 5 0 [wt.-%] Thiourea 5 0 5 5 0 5 6 0 6 0 5 0 5 0 [wt.-%] Thioglycolic acid 0 5 0 0 5 0 0 6 0 6 0 5 0 5 [wt.-%] Ethoxylated amine 0 2 2 0 3 3 5 0 5 0 0 3 0 3 from Example 4 [wt.-%] Alcohol 55 55 55 55 55 55 55 55 55 55 55 55 55 55 [wt.-%] Water 25 25 25 25 25 25 25 25 25 25 25 25 25 25 [wt.-%]

[0180] NP9 was a nonyl phenol with 9 moles ethylene oxide. The alcohol ethoxylate was a C.sub.10/C.sub.12 alcohol with 4-8 moles of ethylene oxide. The alcohol is methanol.