US 2756211 A
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July 24, 1956 w. JONES CORRCSION INHIBITING Filed May 19, 1952 FIG. 2
LQYD W. JONES -6685 A T TORNE Y 2,756,211 CORROSION INHIBITING Loyd W. Jones, Tulsa, Okla, assignor to Stanolind Oil and Gas fiompany, Tulsa, Okla., a corporation of Delaware Application May 19, 1952, Serial No. 288,705 12 Claims. (Cl. 252-855) This invention relates to inhibiting corrosion caused by hydrogen sulfide, carbon dioxide, low-molecularweight organic acids, combinations of these materials, or combinations of each with oxygen or with each other and oxygen. More particularly, it relates to treating wells to mitigate metal corrosion and associated difiiculties.
Several inhibitors for hydrogen sulfide corrosion have been developed in recent years. For example, formaldehyde is such an inhibitor which may be employed in the absence of oxygen. In the presence of both oxygen and hydrogen sulfide, however, formaldehyde is no longer an effective corrosion inhibitor. The same is true for the imidazoline derivatives which have enjoyed considerable commercial success as hydrogen sulfide corrosion inhibitors.
When inhibitors for oxygen corrosion are investigated, it is found that in the presence of a combination of oxygen and hydrogen sulfide even the fatty acids and amines, which form protective films on the metal surfaces to be protected, are ineffective due to pitting. That is, although most of the surface is protected and weight measurements after exposure to the corrosive conditions indicate only moderate loss of weight, a very rapid and severe corrosion takes place in small areas to form deep pits which quickly penetrate the entire metal thickness. Even the cyclohexylamine salts of acids from hydrocarbon oxidation, as suggested in U. S. Patent 2,330,524 to Shields has been found to be ineffective to prevent combined oxygen and hydrogen sulfide corrosion, although the combined inhibiting abilities of an amine and a fatty acid are available.
The effects of the combined corrosive action of oxygen and hydrogen sulfide are particularly noticeable in wells producing sour crude oil accompanied by brine. In some wells of this type, it is possible to exclude air from the well and thus avoid the effects of oxygen. In many applications, however, air has access to the well. For example, the well may be pumped with open casing, permitting air to enter the annular space between the tubing and casing. In gas drive operations, in which air is employed as the driving gas, a large amount of oxygen may enter a producing well from the formation, resulting in a very aggravated type of corrosive condition. Even if natural gas were employed as the driving gas, leakages in the system usually result in a small percentage of air being present in the gas. In wells being produced by hydraulically-actuated bottom-hole pumps, the power oil carries oxygen to the bottom of the well where it may enter crude oil containing hydrogen sulfide. The problem becomes particularly serious in air-lift operation of wells producing sour crude and brine.
Many wells suffer corrosion due to low-molecularweight organic acids, especially those acids containing 2 to 4 carbon atoms per molecule. Inhibitors are known for such a type of corrosion, but many of them such as ammonia and sodium chromate are ineffective in the presence of either hydrogen sulfide or oxygen or both of these gases. On the other hand, inhibitors such as formaldehyde, efiective for hydrogen sulfide alone, are ineffective in the presence of low-molecular-Weight organic acids.
A particularly severe problem exists when all three corrosive agents, that is, hydrogen sulfide, oxygen and lowmolecular-weight organic acids, are present simultanited States Patent neously with water, as, for example, in tertiary recovery by underground combustion.
In many cases, the effects of corrosion and wear enhance each other. For example, in a pumping well, the rubbing of the rods on the tubing tends to wear through the tubing. This effect is greatly accelerated if a corrosive liquid is present. Some inhibitors, such as the higher fatty acids, form a type of film which prevents both wear and certain types of corrosion. But the higher fatty acids are ineffective in the presence of hydrogen sulfide and, accordingly, wear and corrosion proceed in a most aggravated form in the presence of this corrosive material even in areas in which corrosion in the absence of wear is only a minor problem.
There is considerable evidence that the same local electrolytic cells which are responsible for much of the corrosion of metals, are also responsible for other effects such as the deposition of paraifin in well tubing. An effective neutralization of such cells would be desirable as a means for mitigating not only corrosion, but other effects such as parafiin deposition.
Although the problems are particularly serious in oil wells, the same troubles are also present in other systems such as in surface injection equipment for water-flooding operations in which the injected water contains hydrogen sulfide, carbon dioxide, low-molecular-weight acids, or combinations of each with oxygen or with each other and oxygen. It will be apparent, also, that corrosion due to these materials or various combinations thereof often occurs outside the petroleum industry and requires a solution there.
Accordingly, it is aprincipal object of this invention to provide an inhibitor for the corrosive action in the presence of water, of hydrogen sulfide, carbon dioxide, low-molecular-weight organic acids, combinations of these materials, or combinations of each with oxygen or with each other and oxygen.
A more particular object of my invention is to provide a method of inhibiting the corrosion of ferrous metal parts in wells by the corrosive action of the above-mentioned materials or combinations thereof.
An additional object of the invention is to provide a well-treating method to mitigate the effects, such as paraffin deposition, often associated, like corrosion, with localized electrolytic cells in metal surfaces in wells.
Another object is to provide a remedy to the combined action of wear and corrosion which often occurs even in areas which corrosion alone is only a minor problem.
In general, I accomplish these objects by use of a combination of an amine and an organic acid falling within certain molecular weight ranges. For example, the octadecyl amine salts of acids produced by the liquid phase partial oxidation of kerosene in a process such as the Burwell process (as described in U. S. Patent 1,690,769) have been found to be satisfactory for my purposes. Test panels exposed to brines containing hydrogen sulfide and air, where an amine-acid complex of these materials was employed as an inhibitor, remained substantially free from corrosion both of the general and pitting type. This was true even when the ratio of air to hydrogen sulfide was in the highly-corrosive range of about to l to be expected in air-lift operations.
Representative test panels are illustrated in the accompanying photographs. All figures show test panels subjected to the conditions outlined in Example I below employing various inhibitors. I
Figure 1 illustrates the effectiveness of the octadecyl amine salts of Alox 425 acids produced by the liquid phase oxidation of petroleum hydrocarbons.
Figure 2 shows the effects of using the octadecyl amine alone.
Figure 3 exhibits the efifects of employing the Alox 425 acids alone.
Figure 4 demonstrates the corrosion-inhibiting ability of an acid-amine complex in which Alox 425 acids were employed, but the amine was decyl amine.
Figure shows the results of substituting octyl amine for the decyl amine employed in obtaining the panel shown in Figure 4.
Figure 6 illustrates a panel obtained by substituting acetic acid for Alex 425 acids, octadecyl amine being employed as the amine portion of the inhibitor.
Comparison of Figures 1, 2 and 3 shows clearly that the inhibiting ability of the amine-acid complex is a combination effect not obtained with either the acid or amine alone. Both Figures 2 and 3 show the good protection of a part of the metal surface, while other parts are badly corroded.
The panel shown in Figure 4 demonstrates the ability of the decyl amine complex to give uniform protection of the entire surface so that any corrosion which does occur is spread out over the entire area and does not quickly penetrate at any one point. A comparison of Figures 4 and 5 shows the rather surprisingly sharp division between operable and inoperable amines at about carbon atoms per molecule.
In Figure 6 can be observed the scattered pitting type corrosion which occurs when the amine salts of watersoluble organic acids are employed as inhibitors. The pits will of course, quickly penentrate the metal thickness, so the very eflective protection of most of the surface is of little value.
The amine-acid complexes are efiective not only in the mitigation of corrosion due to hydrogen sulfide, oxygen, or combinations of these materials, but also are effective in inhibiting corrosion due to low-molecular-weight organic acids such as those found in high-pressure condensate wells. Thus, the materials are applicable not only to secondary recovery projects in which air is in jected into hydrogen-sulfide-containing formation intentionally or inadvertently, but are particularly applicable to underground combustion projects in which low-molecular-weight acids are produced in the combustion zone and later appear at the output wells together with oxygen and hydrogen sulfide.
I believe the theory of my invention to be as follows, although it will be understood that my invention is not limited thereto. The theory is based on the well-known occurrence of localized electrolytic cells on surfaces of metals. Either the amines or the acids appear to become rather strongly adsorbed on the entire surface of the metals, and this adsorbed film is suificiently tight over both positive and negative areas of localized electrolytic cells to inhibit a high percentage of the corrosion in the presence of oxygen and water alone. Dr. Zismans work at the Naval Research Laboratory fully supports this observation. (NRL Report 3680, obtainable as PB 101874 from U. S. Department of Commerce.) In the presence of a combination of oxygen, water, and hydrogen sulfide, however, neither the acids nor the amines are held with sufficient force over the entire metal surface to prevent corrosion. It is believed probable that the acids are not only adsorbed, but may be chemisorbed on positive areas of localized electrolytic cells. That is, they may be bound by forces approaching those involved in chemical reactions. On negative areas of the cells, however, simple adsorption forces are probably involved between the surface and the acids. It is believed to be probable that the amines are chemisorbed on negative areas and simply adsorbed on positive areas.
.If the above theory is correct, a simple adsorbed layer is apparently suflicient to protect a surface from oxygen corrosion, but is insufiicient to prevent penetration by a combination of hydrogen sulfide and oxygen. Thus, an acid layer may fail to prevent corrosion of negative areas, while an amine layer may fail to protect the positive areas when both hydrogen sulfide and oxygen are present. By the use of both an amine and an acid, a chemisorbed layer is perhaps formed over all areas, the electrolytic cells being effectively neutralized, thus preventing substantially all corrosion whether by the independent corrosive actions of hydrogen sulfide, low-molecular-weight acids, or carbon dioxide alone, or by combinations of these corrosive agents with each other or with oxygen. A much longer film life would be expected if this theory is correct.
Since the negative and positive areas of the electrolytic cells would be substantially neutralized, according to this theory, prevention of paraflin deposition due to the effects of these areas would also be explained.
In the above discussion, rather general reference has been made to amines and acids. As earlier pointed out, however, some of the amine-acid salts or complexes are inoperable as corrosion inhibitors in the presence of a combination of hydrogen sulfide and oxygen. Both the amine and the acid must be carefully selected. For example, tests indicate clearly that an amine must be selected which contains at least 10 carbon atoms per molecule. The exact reason for this limitation is not well understood. It is perhaps due to the higher solubility of the lower-molecular-weight amines in both water and oil. It might also be due to the inability of a short hydrocarbon portion of the amine to form a film of sufiicient thickness to prevent penetration by corrosive materials. Reduced lateral cohesive forces between the shorter molecules might also be responsible. Probably all the factors contribute to the failure of inhibitors prepared from amines having less than 10 carbon atoms per molecule. Although the IO-carbon amines have proved effective, the higher solubility usually results in a film lost relatively quickly to the oil and water. For this reason, an amine having at least 12 or 14 carbon atoms is generally preferred.
An upper limit of about 20 carbon atoms should also be observed in the case of amines simply because of the difliculty of dissolving the amines, or even amine-acid complexes in an oil to permit application to the surfaces to be protected. By use of special solvents such as benzene, carbon tetrachloride, ethanol, or the like, highermolecular-weight amines and their complexes with organic acids can be employed. Increased solubility of high-molecular-weight amines can also be achieved by use of lower-molecular-weight acids or mixtures of acids.
I have found that many types of amines can be employed within the limitations set forth above. Thus, the amines may be cyclic, aromatic, branched, or unsaturated, and may contain linkages such as ether or ester groups in the molecule. They may be primary, secondary or tertiary. Straight chain, saturated, primary amines are preferred, however, since a closer spacing of molecules can be obtained with this type of amine, resulting in a film more impervious to corrosive materials. Accordingly, I generally prefer to employ the straight-chain primary octadecyl amine as the amine portion of my inhibitor.
The acid should be an organic acid since inorganic acid salts of the amines give only the inadequate protection of the amine itself. I found that either carboxylic or sulfonic acids are operable, although the carboxylic acids are considerably superior to the sulfonic acids. In either case, the acid should contain at least 5 and preferably at least 6 carbon atoms per molecule. The amine complexes of acids containing only 5 or 6 carbon atoms give some protection but for best results the acid should contain about 10 or more carbon atoms per molecule. Acids containing less than 5 or 6 carbon atoms apparently fail due to high water solubilities. As in the case of the amines, solubility considerations set an upper limit of about 20 on the number of carbon atoms in the acid molecule. Again, however, this limitation can be avoided by the use of special solvents such as benzene, carbon tetrachloride, ethanol or the like.
The acid may contain aromatic, cylic, ether, ester or hydroxyl groups, and may be branched or unsaturated. I prefer to use, however, straight chain, saturated, unsubstituted acids to insure close spacing of the molecules in the chemisorbed film.
The acids may be derived from several sources. In the case of the sulfonic acids, a convenient source is the petroleum sulfonic acids produced in acid treating of oils. Carboxylic acids may be stearic, palmitic, oleic, lauric and the like obtained from vegetable and animal oils and fats, or may be mixtures of these acids, or other mixtures of acids such as those produced in the formation of hydrocarbons by the reduction of carbon monoxide by hydrogen over a suitable catalyst. Any individual member of these acid mixtures may, of course,
be isolated and used alone if desired, but some of the mix-.
tures are often preferable to avoid emulsion and gel formation difficulties encountered when some of the purer forms of individual acids or acid mixtures are employed.
A mixture of acids is preferred because the amine complexes do not tend to form emulsions or gels, is the mixture produced from normally liquid fractions of petroleum, such as kerosene, by liquid phase partial oxidation in a process such as that described in U. S. Patent 1,690,769 to Burwell. The acids should preferably be distilled, at atmospheric pressure or under a vacuum with or without steam, to remove acids lighter than valeric and heavy impurities. The acids may also be purified by forming an aqueous solution of their salts with alkali metals, separating the water-insoluble impurities, and then regenerating the organic acids by the addition of a mineral acid. I have found, however, that the impurities such as alcohols, ketones, esters, and the like appear to exert a desirable" demulsifying and degelling action and for that reason should be retained. Since only traces of light acids and heavy impurities are normally present in the oxidation products, the raw undistilled material, containing acids with an average molec ular weight of about to 12 or more, may be employed as the acid source without purification. V v
In case serious emulsion or gel problems are encountered, demulsifiers may be added. This is important not only to avoid the troublesome emulsions and gels themselves, but also to improve corrosion inhibition. The explanation of less effective corrosion inhibition in the presence of emulsions apparently is that the inhibitor is somewhat surface-active. That is, it is concentrated at interfacial surfaces. Since this surface is great in an emulsion, most of the inhibitor will be concentrated in these interfaces and little will remain in the body of the oil for deposition on the metal surfaces. In many wells, oil-in-water type emulsions often occur naturally. In such wells, the proposed amine-acid complexes, tending to form water-in-oil type emulsions, often decrease the emulsion problems naturally present. The amines, such as decyl amine, are convenient demulsifiers in the usual case where an excess of amine over that required to neutralize the acids is not objectionable.
The acid and amine may be added separately, but preferably should be added as a salt of the acid and amine, which some authorities insist is merely a complex and not a true salt. Two principal advantages are obtained by using a neutral salt or complex of the amine and acid. First, only one inhibitor material need be handled rather than two. Second, the oil-solubility of the complex is generally much higher than that of the amine or acid alone which permits handling of more concentrated solutions in oil. This is particularly true of the higher molecular weight materials. In addition, corrosion by either the acid or amine is eliminated if each is neutralized by the other. Since these corrosive effects of the unneutralized acid or amine usually are not serious, particularly in the presence of the complex, it may be desirable in many cases to employ more of one component than the other. For example, in underground combustion work some high-molecular-weight carboxylic acids are produced and will be present in the output wells. In this case, it may be desirable to add much more of the amine than of the acid, since some acid is already present in the Well. Another example is when an excess of amine is employed as a demuls'ifier. In any case, an exact neutralization of the amine and acid is not necessary, one of these components often being present in an amount as much as twice as great as the other.
When the term inhibitor is used hereinafter in both the specification and claims, it should be understood that the term is not limited to the neutral complex of acid and amine, but may refer to an amine and an acid introduced together or separately and in stoichiometricor other concentrations.
It is convenient to refer to the inhibitor as consisting of an amine and an acid, each being present in a given concentration. For example, reference may be made to adding 5 parts by weight each of the amine and the acid per million parts of a fluid. This means the amine and acid may be introduced simultaneously or one after the other in unreacted form or reacted to form salts with each other or with other materials. They may be added in equal or different amounts so long as each component of the inhibitor, the amine and the acid, is present in a concentration of at least 5 parts per million.
The amine-acid complex is usually prepared simply by mixing the acid and amine at a temperature above their melting points. The two components may also be mixed with or dissolved in kerosene or other solvents before being mixed together to form the reaction product. The complex is sometimes prepared by forming watersoluble salts of the amine and acid, and mixing Water solutions of these salts.
In selecting the proper concentration of inhibitor to be employed, due regard must be had for the type of fluids which are to come in contact with the surfaces to be protected. If the fluids are principally Water, the concentration of inhibitor can be considerably lower than when the fluids are principally oil. This is probably because of the higher solubility of the inhibitor in oil than in water, resulting in a greater tendency of the oil to dissolve away the protective layer.
The quantity of inhibitor employed will also depend upon the method of treating. In laboratory testing, it is convenient to maintain a reasonably constant concentration of inhibitor continuously in fluids in contact with the test panel. The same general technique is reflected in some field practices in which an inhibitor in liquid form is allowed to flow, or is pumped at a slow continuous rate into the casing. If a solid pellet form of inhibitor is employed, a dispenser may inject a small pellet every few minutes into the corrosive fluids where is dissolves to maintain a fairly constant concentration of inhibitor continuously in the fluids. Or larger pellets may be employed in which the inhibitor is dispersed in a slowlysoluble binder which gradually releases the inhibitor to maintain the latter continuously in the-corrosive fluids. Many other schemes will occur to those skilled in the art, such as the use of a container of inhibitor from which the inhibitor escapes slowly and continuously into the corrosive fluids through a small orifice.
A more common method of treatment and the one which I greatly prefer, since a smaller amount of inhibitor is required, is the intermittent treatment of the well with a high concentration of inhibitor, followed by a period in which no treatment is provided. A typical treatment, for example, consists of adding an inhibitor once a day. The entire quantity of inhibitor is introduced into a well casing inone batch and is followed by a quantity of oil or water to wash the inhibitor to the bottom of the Well- A common practice is to return at least a portion of the well production into the casing for '7 a period of to minutes, or long enough to introduce about '20 to 50 gallons of liquids into the casing. The result of this so-called batch treatment is to maintain for a short time an extremely high concentration of inhibitor in contact with the metal surfaces. The concenclaims are all based .on total fluids produced between treatments if the intermittent-type is selected, and do not reflect the actual concentrations during the short period tration often reaches a value of as much as 50 to 100 or more times as great as would be present if the same quantity of inhibitor had been introduced continuously over a period of from 24 to 36 hours.
less inhibitor, can be employed in this method than in continuous treatment is not'well understood, but may be because a more concentrated and imprevious filmv is de- The reason why 1 spreading the addition of the same amount of inhibitor out over a period of a day or so. In many wells, a large volume of oil is normally present in the annular space between the tubing and casing. In these wells, even though the inhibitor is added in a batch it tends to mix with this large volume of oil and is pumped from the well over a period of a day or longer. If high concentration inhibitor treating of such wells is desired, they must bepumped down as far as possible before adding the inhibitor. On the other hand, continuous treatment of metal parts in a well can be obtained while employing batch addition of inhibitor to the well by building up and maintaining a large volume of oil in the annulus at all times. I
Another indication of the advantages of a high-concentration treatment is the benefit derived from the socalled pretreating or slugging technique in which at the beginning of use of an inhibitor, the concentration is maintained at a much higher value in the first few treatments than the concentration which is eventually used in normal treatment. Use of a given amount of inhibitor in either continuous or intermittent treatment is more efiective for a considerable time after such a pretreatment than without it. The explanation may be that the pretreatment provides a concentration of inhibitor on the metal surface which asymptotically approaches from the high side equilibrium with the normal treatment, whereas without the conditioning step, the concentration on the metal surface asymptotically approaches equilibrium from the low side. Another possible explanation is that the high concentration causes a continuous protective film to plate out on the metal surface. Such a film may then be easily kept in repair by the subsequent lower-concentration treatment, whereas the lower'concentration treatment might not be capable of forming a good protective film in the beginning.
As a result of the above observation, the preferred method of treatment is to pretreat the metal surface with a high concentration of inhibitor in an intermittent operation, and then employ an intermittent-type of normal treatment at a lower concentration.
In instances where no oil is present, as in surface injection systems for water-flooding operations, a concentration of only parts by weight of inhibitor per million parts of water has been found to be effective when the inhibitor was introduced intermittently. The corrosive conditions were somewhat severe in that case, so for less severe conditions, or if not quite such a high degree of protection is required, concentrations of the order of 5 to 10 parts per million may be employed for intermittent treatment of relatively oil-free systems. If oil is the principal ingredient of the fluids, the normal intermittent treating concentration, based on total well fluids, should be at least about 10 to 20 parts per million. The above concentrations as well as those employed in the of the treatment unless explicitly so specified. The period between treatmentsis generally 24 hours, but two or more treatments may be made in one day, or they may be spread out as far as a week apart.
If a continuous treatment is to be employed, the quantity of inhibitor should be atleast about 10 to 20 parts per million in mildly corrosive oil-free systems or about 20 to 50 parts per million in systems containing mostly oil. For oil-free systems, to 200 parts per million is considered a high inhibitor concentration range. For oil-containing systems, the range may be as high as 200 to 400 parts per million in highly corrosive areas.
In pretreating operations, concentrations as high as 50 times thenormaltreatment which will follow are sometimes employed. The'more usual pretreating concentrations are 10 to 20 times normal. Pretreatments normally last from 3 to 7 days or slightly more and may be fol lowed by an intermediate'stageof treatment at concen' trations about twice normal for a period approximately equal to that of the pretreatment.
introduced in thesame manner, but in order to insure a large portion of the inhibitor reaching the bottom of the well in a shorttime a solution containing not more than about 50 per cent of the inhibitor is usually employed.
A 10 per cent solution is generally used. Although petroleum oil solutions are most economical, solutions of the inhibitor in solvents which are themselves soluble, in oil may also be employed. A few examples of such solvents I include benzene, alcohols, ethers, esters, ether alcohols available under the trademark Cellosolves and chlorinated hydrocarbons. Use of such solvents is particuv larly desirable in the case of high-molecular weight inhibitors of limited solubility in petroleum hydrocarbons.
For many applications, a stick, ball, briquette, capsule, or other pellet form of inhibitor is preferable or necessary. For example, a long column of oil may be present in the annulus, preventing rapid diffusion of the inhibitor to the well pump intake. Or a packer may be set between the tubing and easing requiring the inhibitor to be introduced through the tubing. If a pellet form is desired, it may be prepared by compressing the powdered inhibitor, if a solid, or by use of an oil-soluble or water-soluble binder if the inhibitor is either a liquid or a solid. Some examples of oil-soluble binders are petroleum paraffin, and natural waxes such as ozokerite. Suitable water-soluble binders include gelatin, the solid polyhydric alcohols, sugars, water-soluble gums and ethylene oxide polymers as disclosed in copending application, S. N. 288,345, filed May 16, 1952, by Jack Barrett.
For application to systems in which the fluid is predominantly water, for example, injection systems for water-flooding projects, a water-dispersible form of inhibitor is preferred. This can be obtained by forming pellets with a water-soluble hinder, or by emulsifying the 0ilsoluble inhibitor, whether the complex, or the amines and acids separately, in water by use of a suitable emulsifying agent. The emulsifying agent should be non-ionic to avoid difiiculties with the ionic inhibitor and with brines. The emulsifier should be water-soluble to insure the formation of an oil-in-water emulsion. An example of such an emulsifier is a polyoxyethylene anhydrosorbitol monooleate containing approximately 20 oxyethylene groups This solution may be poured down per molecule. This emulsifier is available from the Atlas Powder Company under the trademark Tween 80.
It is to be noted that many of these emulsifiers are water-soluble or water-dispersible waxy solids which can act as water-soluble binders for the inhibitor. Thus, the materials may act to carry oily inhibitors, in stick or other pellet form, through the oil phase and into the Water phase where the inhibitor is dispersed into the aqueous phase by the emulsifying properties of these binder-emulsifiers. I
My invention will be further illustrated by the following specific examples:
EXAMPLE I One series of tests was carried out as follows: Into 1 liter glass bottles, 800 milliliters of an aqueous 5 per cent sodium chloride brine were introduced together with about 16 milliliters of kerosene containing an amount of inhibitor equal to 400 parts by Weight per million parts of combined brine and kerosene. Polished and tared mild steel test panels, 1 inch by 1 inch by inch were suspended in the brine by metal rods from which the panels were insulated by plastic washers. The rods were supported, in turn, by insertion into the rubber stoppers employed to close the bottles. A stream of corrosive gases was bubbled continuously through the liquids in the bottles while the temperature was maintained at 100 F. The corrosive gases consisted of 1 per centhydrogen sulfide and 99 per cent air. The bottles were shaken violently for 15 consecutive minutes every two hours. At the end of three days, the panels were dipped in dilute inhibited hydrochloric acid solution, rubbed lightly to remove adhering scale, rinsed in distilled water, dried and weighed. Per cent inhibition was determined by the following formula.
Where W2 is weight lost by the test panel and We is weight lost by a control panel exposed to the same conditions without an inhibitor.
The results of the tests are summarized in Table I.
Percent inhibition== X 100 The Armeen materials were all obtained from Armour and Company. Armeen 18D is about 92 per cent octadecyl amine and about 6 per cent hexadecyl amine. Armeen residue is an' impure mixture of amines containing from 8 to 12 carbon atoms per molecule. Armeen HT is a mixture of about 70 per cent octadecyl and about 30 per cent hexadecyl. Alkyl Amine JM was obtained from Rohm and Haas Company and is a branched chain octadecyl amine. As previously explained, Alox 425 acids are obtained by the partial oxidation of normally liquid hydrocarbons and contains acids having an average number of carbon atoms per molecule within the range of about to 12. The material is obtainable from the Alox Corporation.
The relatively low inhibition when Armeen residue was used as the amine source is probably due to the large amount of amines of low moleculer weight, leaving only a low concentration of those having at least 10 carbon atoms per molecule.
The relatively high per cent inhibition using Armeen 18D alone is misleading, since the panel was pitted. This type of corrosion would lead to penetration of the metal in a short time in spite of the apparently good per 10 cent inhibition. Figure 2 of the drawing illustrates this pitting.
EXAMPLE II The conditions and procedure were the same as in Example I except the duration of the test was 2 days and the temperature was maintained at 80 F. The amine was 8(N-diethyl amine) ethyl stearate, a tertiary amine in which one of the attached chains contains an ester linkage. The acid employed for preparing the amine salt was lauric acid. The salt concentration employed was 400 p. p. in. Weight lost by the control panels averaged 0.2157 gram. Weight lost by the test panelsaveraged 0.0323 gram. Thus, inhibition was 85.0 per cent. The entire area was protected to approximately the same degree. This example demonstrates the effectiveness of salts of tertiary amines, and also of amines containing an ester linkage.
EXAMPLE III Another series of tests was conducted in the same manner as Example I except instead of bubbling air and hydrogen sulfide continuously through the brine, about 700 parts of hydrogen sulfide were dissolved in the brine at the start of the test, and the oxygen was provided by the 200 ml. of air above the oil and water in the bottles. The duration of the tests was 7 days. The results are presented in Table II. The weight lost by the control panels averaged 0.0700 gram.
Table II Percent Amine Acid Inhibi- Remarks tion octadecyl 83 Uniform Protection.
Do. 90 Do.
Do 79 Do.
Do- 63 Widespread Fitting.
Do Hydrocarbon 78 Uniform Protection.
Synthesis, 7 carbon and Heavier. Sec. Octadecyl Alox 425 83 Do.
and Heptadecyl. Dodecyl 87 Do.
D 85 Do.
61 Slight Fitting and Localized etching. 71 Very Slight Shallow Fitting. 95 Uniform Protection. 70 Deep Pitting and Widespread Etchmg. Oyclohexyl do 15 Deep Fitting and Localized Etching. l None --do 9 Slight Pitting and Severe Localized Attack.
Do Stearic 147 Deep Fitting and (Accel- Widespread Etcherated) ing.
Do Ricinoleic 78 Few Deep Pits and Some Localized Etching. Do Laurie 69 Many deep Pits.
Dodecyl None 36 Widespread Etching and Some Pits.
Sec. Octadecyl -do 96 Few Medium Pits.
EXAMPLE IV The method of Example III was employed to test the inhibiting abilities of some metallicsalts' of the acids. The results are presented in Table III.
In order to test the efiiciency of my inhibitor against hydrogen sulfide corrosion in the absence of air, a test was set up as follows: A liter of aqueous per cent sodium chloride solution was placed in a flask and prepurifled nitrogen was bubbled through it for several hours to eliminate dissolved air. Hydrogen sulfide was then introduced until its concentration in the brine was approximately 500 parts per million. At the same time, a one liter Florence flask was flushed out with oxygen free nitrogen by inserting a tube to the bottom of the flask and allowing nitrogen to flow through the tube for several minutes. About 30 ml. of kerosene, containing 200 mg. of the octadecyl amine salts of Alox 425 acids were introduced into the one liter flask before this nitrogen flushing operation. The brine, containing hydrogen sulfide, was then siphoned into the one liter flask until the liquid reached the neck thereof. A polished and tared mild steel panel was then suspended in the brine in the flask by means of a glass hook held by the rubber stopper used to seal the flask. After swirling the flask to mix the kerosene and brine, the kerosene was permitted to rise to the top and the flask was allowed to sit at room temperature of about 75 F. without shaking for five days. The panel was then removed, cleaned and weighed as described in Example I. The loss in weight by the control panels averaged 0.0158 gram. Loss in weight by the test panels was only 0.0008 gram. Thus, in spite of the low solubility of the inhibitor in the aqueous phase, the inhibition was 95 per cent complete and the protection was uniform over the entire area.
EXAMPLE VI In order to test the ability of my inhibitor to mitigate corrosion by low-molecular-weight organic acids and carbon dioxide, tests were made as follows: About 1 liter of an aqueous 5 per cent brine solution was placed in a 2 liter round-bottomed flask together with about 1 liter of kerosene. A reflux condenser was placed over the flask and the system was freed of air by boiling the water while bubbling a stream of oxygen-free carbon dioxide through the liquids for a period of two hours. The rate of bubbling was 1 cubic foot of carbon dioxide per hour..
To the air-free liquids 500 mg. of acetic acid were added (500 p. p. m. by weight based on the water phase). Then 200 mg. of a salt of octadecyl amine and Alox 425 acids were added. A polished, tared, mild steel panel was then suspended in the water phase in the flask on a glass rod passing through a seal in the flask. A reflux condenser was placed on the flask and the flask heater was adjusted to hold the temperature just at the boiling point of water. For consecutive seconds out of each minute, the panel was raised into the oil phase. A control test was run in the same manner at the same time without inhibitor. After 24 hours, the panels were cleaned, dried and weighed as described in Example 1. Control panels lost an average of 0.1250 gram while the test panels lost an average of only 0.0084 gram. Thus, 93.3 per cent of the corrosion was inhibited. The protection was uniform over the entire area.
EXAMPLE VII Weight lost by the control panel was 0.0115 gram.
Table IV Concentration of In- Percent Remarks hibitor. p. p. m. Inhibition 96. 5 Uniform Protection.
Do. General Corrosion; no localized pitting.
1 2 EXAMPLE VIII In a water-flooding project, water was obtained from a water well. The water contained a large amount of solids, 195,000 parts per million, and 50 parts per million of hydrogen sulfide. The casing annulus was not normally open, but some air was occasionally permitted to enter the annular space between the tubing and casing. This air found its way to the bottom of the well and as a result some oxygen was present in the produced water. The well was treated by introducing into the annulus on each of two successive days, 26 gallons of a waterdispersible form of inhibitor. On each of 12 succeeding days, 13 gallons of the inhibitor were introduced in the same manner. The water-dispersible form of inhibitor consisted of 5 pounds per gallon of octadecyl amine salts of Alox 425 acids, about 10 per cent of a water-soluble, non-ionic emulsifier, about 2 per cent water, and the remainder of the gallon kerosene. The well produced about 10,000 barrels (42 gallons per barrel) per day of water having a density of about 1.1 grams per milliliter. Thus, the treatment amounted to about 20 parts of inhibitor per million parts of total brine produced. Since the inhibitor was all added at one time in 5 gallon slugs, each slug being washed down by about 10 barrels of water, the actual concentration in the water at the bottom of the well was about 2000 to 5000 parts per million for a few minutes. Before treatment with my inhibitor, corrosion was removing metal at the rate of about 0.040 inch of metal thickness per year. During the treatment, metal was corroded away at the rate of about 0.007 inch per year. Thus, about per cent of the corrosion was inhibited. The protection was uniform over the entire area.
From the above description, theories and examples, it will be apparent that I have accomplished the objects of my invention. Specific materials and examples are offered for the purpose of illustration only and are not to be construed as limiting my invention; the limits of which should be determined rather, by the claims.
1. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, carbon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, combinations of these materials with each other, combinations of each of said corrosive materials, with oxygen and combinations of said materials with each other and oxygen, comprising adding to said fluids, per million parts of said fluids, at least 5 parts by weight each of an aliphatic amine and of a carboxylic acid, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule.
2. A method for inhibiting corrosion of ferrous metals by fluids containing water and hydrogen sulfide comprising adding to said fluids, per million parts of said fluids, at least 5 parts by weight each of an aliphatic amine and of a carboxylic acid, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule,
3. A method for inhibiting corrosion of ferrous metals by fluids containing water and an organic acid containing from 2 to 4 carbon atoms per molecule comprising adding to said fluids at least 5 parts by weight each of an aliphatic amine and a carboxylic acid per million parts of said fluids, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule.
4. A method for inhibiting corrosion of ferrous metals by fluids containing water and a combination of hydrogen sulfide and oxygen comprising adding to said fluids at least 5 parts by weight each of an aliphatic amine and a carboxylic acid per million parts of said fluids, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule.
5. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, carbon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, combinations of these materials with each other, combinations of each With oxygen, and combinations with each other and oxygen, comprising adding to said fluids at least 5 parts by weight each of an aliphatic amine and a carboxylic acid per million parts of said fluids, said amine containing a hydrocarbon radical having at least 12 carbon atoms per molecule, and said acid containing at least carbon atoms per molecule.
6. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, carbon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, combinations of these materials with each other, combinations of each with oxygen, and combinations with each other and oxygen, comprising adding to said fluids at least 5 parts by weight each of octadecyl amine and acids produced from a normally liquid fraction of petroleum by liquid phase partial oxidation of the latter, per million parts of said fluids.
7. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, carbon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, combinations of these materials with each other, combinations of each with oxygen, and combinations with each other and oxygen, comprising adding to said fluids at least 10 parts by Weight of a salt of an aliphatic amine and a carboxylic acid per million parts of said fluid, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule.
8. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, car bon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, combinations of these materials with each other, combinations of each with oxygen, and combinations with each other and oxygen, comprising adding to said fluids at least 5 parts by weight each of an aliphatic amine and a carboxylic acid per million parts of said fluids, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule, said amine and said acid being added as an emulsion in water stabilized by a non-ionic, water-soluble emulsifier, whereby the oil-soluble inhibitor is dispersed in the aqueous phase of said fluids.
9. A method for inhibiting corrosion of ferrous metal parts of surface injection equipment of water-flooding operations by the combined action of hydrogen sulfide and oxygen comprising adding to the water a mixture comprising a non-ionic, Water-soluble emulsifying agent and at least 5 parts by weight each of an aliphatic amine and a carboxylic acid per million parts of said Water, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid containing at least 6 carbon atoms per molecule, whereby the oil-soluble corrosion-inhibiting amine and acid are dispersed in the water.
10. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, carbon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, combinations of these materials With each other, combinations of each of said corrosive material with oxygen and combinations of said materials with each other and oxygen, comprising adding to said fluids, per million parts of said fluids, at least 5 parts by Weight each of an aliphatic amine and of a carboxylic acid, said amine containing a hydrocarbon radical having at least 10 carbon atoms per molecule, and said acid being derived from a normally liquid fraction of petroleum by liquid phase partial oxidation of the latter.
11. A well-treating and corrosion-inhibiting composition comprising the salt of an aliphatic primary amine containing a hydrocarbon radical having at least about 10 carbon atoms per molecule and a mixture of acids derived from a normally liquid fraction of petroleum by liquid phase partial oxidation of the latter.
12. A method for inhibiting corrosion of ferrous metals by fluids containing water and a member of the group of corrosive materials consisting of hydrogen sulfide, carbon dioxide, organic acids containing from 2 to 4 carbon atoms per molecule, oxygen, and combinations of the individual materials, comprising adding to said fluids at least about 5 parts by weight each of an aliphatic primary amine and a carboxylic acid per million parts of said fluids, said amine containing a hydrocarbon radical having at least about 10 carbon atoms per molecule, and said acid being derived from a normally liquid fraction of petroleum by liquid phase partial oxidation of the latter.
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