US2840584A - Corrosion inhibitor - Google Patents

Description

CORROSION INHIBITOR Loyd W. Jones, Tulsa, kla., assignor to Pan American Petroleum Corporation, a corporation of Delaware No Drawing. Application October 1, 1953 Serial No. 383,689

4 Claims. (Cl. 260-4045) This invention relates to inhibiting corrosion. More particularly it relates to inhibitors for most types of cor rosion occurring in oil wells and associated equipment or combination of the various types of corrosion discussed herein. The corrosion inhibitors also act as demulsifiers and parallin removing agents. They may also be employed to clear water-blocked formations.

This application is a continuation-in-part of my copending application U. S. Serial Number 288,705 filed May 19, 1952, now U. S. Patent 2,756,211. In the parent application a combination of amines and carboxylic acids as corrosion inhibitors is disclosed. Such amines are aliphatic amines containing at least 10. carbon atoms per molecule. Examples are dodecyl and octadecyl amines. Straight chain primary amines are preferred. The acid portion is carboxylic in nature and contains at least 5 or 6 carbon atoms. Preferably this portion is obtained from the liquid phase partial oxidation of normally liquid petroleum fractions. Other acids such as lauric or oleic are also satisfactory.

These salts are unique in that they inhibit corrosion by hydrogen sulfide, carbon dioxide, light organic acids, oxygen or combinations of these materials. They are also unique in that at least certain of the salts avoid the usual emulsion and gel problems encountered when salts of fatty acids are added to oil. Some of the salts also prevent paraffin deposition on metallic surfaces. These salts may be employed in the form of oil solutions for systems in which the liquid is predominantly oil. For systems in which the liquid is predominantly water the inhibitor should be used in a water dispersible form. In the case of water having a low salt content, most of the non-ionic water-soluble emulsifiers of either the ester or ether type are suitable dispersing agents. If the water contains considerable salt, then a special class of non-ionic water-soluble dispersing agent should be employed. This class of dispersing agent is more particularly described and claimed in my copending application U. S. Serial Number 335,161 filed February 4, 1953. eral, this class of dispersing agent has the formula RXW, wherein R is an aliphatic hydrocarbon radical containing at least 12 carbon atoms, X is an ether type linkage selected from the group consisting of oxygen and sulfur and W is a water-soluble portion selected from the group consisting of polyglycols and polyglycerols containing at least 4 other linkages.

If it is desired to introduce inhibitors through the tubing in a well, or to provide a slowly dispersible form in any application, they may be produced in stick form by use of oil-soluble waxes such as paraffin or of watersoluble binders ,such as gelatin, as more fully described and claimed in the copending application U. S. Serial Number 288,345 filed on May 16, 1952, by Jack P. Barrett, now abandoned.

The salts are employed in concentrations of about to 50 parts per million of corrosive liquids in mildly corrosive systems consisting predominantly of oil. much as 500 parts per million may be employed in highly In gen-- ice corrosive liquid is predominantly water the concentration may vary from 10-to 20 parts per million in moderately corrosive systems up to about 200 parts per million is highly corrosive systems. As little as 10 parts per million gives appreciable protection in both oil and water systems. The inhibitor may be applied continuously or intermittently. If applied intermittently the concentration should be calculated on the basis of the entire volume of corrosive liquids to which the metal surface will be exposed before the next treatment.

While the salts disclosed in the parent application constitute a considerable improvement over prior art inhibitors, they are still susceptible to improvement in cer-- tain respects. For example, while the use of oxidized petroleum acids to form the salt gives a product which. usually avoids emulsion formation between water and oil,

in many areas positive demulsifying action is also desired. While prevention of paraflin deposition has been noted, a more positive paraflin-removing action would be desirable in many locations. Also, while amine salts of the oxidized petroleum acids taught in the parent application have been found to possess only limited gel forming ability in oil, the concentration of the'inhibitor which can be added to oil for" purposses of storage in.

a. convenient liquid form is limited by the high pour point of the oil solutions. Some pour points are as high as around 40 F., making their use in colder areas diflicult. A salt with a decreased gel forming tendency An improved corrosion inhibiting ability closed amine salts are highly superior compared to inhibitors previously taught in the prior art.

With the above problems in mind,'an object of the' a corrosion inhibitor with decreased tendency to gelhydrocarbons so that high concentrations of inhibitors in oil can be handled without encountering excessively high pour points. A still further object is to provide a corrosion inhibitor which may also be used to remove water blocks from formations.

In general, I accomplish the objects of my inventionby using a salt of carboxylic acids produced by the liquid phase partial oxidation of normally liquid petroleum fractions and certain highly polar aliphatic polyamines having two or more amino groups located at one end of at least one long hydrocarbon chain. .A preferred example of such a compound is the salt of DuomeenT and Alox 425. Duomeen-T is a trademark of Armour and Company for the highly polar polyamines having the formula '7 In the formula R" is an aliphatic hydrocarbon radical containing from about 16 to 18 carbon atoms- Alox 425 is a trademark of the Alox Corporation for a mixture of acids derived from normally liquid hydrocarbons by 'liquid phase partial oxidation.

Patented June 24, 1958 (3 It reduces the interfaciaL tension between oil and water to nearly zero dynes per centimeter.

(4) It tends to remove water from many water-blocked formations. Y Y

(5). It does not act as an emulsifier of oil and water.

(6) It has apositive demulsifying action on emulsions of water and oil.

(-7) It, is a highly effective corrosion inhibitor even compared to other amine salts.

(8) It, prevents deposition of paraffin from oil onto' metallic surfaces, and there is evidence indicating that it exerts. a positive parafiin-removing action on paraffin already deposited;

All these properties are attributable. to the strongly polar; nature ofportions ofzboththe: amine'and the acid. Sinceboth the; amine.- and-the acidhave strongly polar porti0ns,,thesalt also is:.highly: polar. Being highly polar, these-1t is not-areaclily solvated byoil. Therefore, it has less: tendency 'to form gels in. oilsv than. less polar'materials which-aremore highlyxsolvated by.-the: oils. This decreased ;-'gel-.formingtendency in turn: presumably accountsfor'the increased oil. solubility. It also apparently accounts for the lower. pour point of: oilsolutions. That is,-it' is necessary to. cool oil' solutions of the salt tolower temperatures before gellation' of. the solution b'ecomessufiicient to prevent pouring.

Having aCmorepolar portion than'nio'st salts, particularlythose of the amines; the. salt of-iDuomeen-T and Alox.425 is more surface. active; Thisxaccounts for the ability to. decrease the interfacial tension between oil and water: -A- direct application. oflthis' property is the removaLof water frormwater-blockedi formations of oil wells; When:the salt, preferably. in' oil solution, isinjected into-such formationstheinterfacialzforces between water and oilare reducedto such'anextnt that theyare insuf- Thehighly polarzsalt is: probably adsorbed on metallic surfaces to. someextent. It'is niuch more likely, as'pointed' out in.the parentapplication referred to above, that theamine and acid portions of. the loosely-bound saltare separately adsorbed on difierent'portions of the surface. The proposed amine and acid, being more highly polar, become more strongly attached to the: metallic surfaces tobe protected than. the less polar materials; Theincreased.corrosion-inhibiting ability-is due partly to this fact and partly toi the decreased emulsion-forming tendency. The. probable reason why emulsions decrease the corrosion-inhibiting abilities of most amine salts is that these salts, being surface active, tend to become concentrated at the large interfacial surface between the liquids rather than on the metal surface. When emulsion formation is decreased, more of the inhibitor becomes available for deposition on the metal surfaces to be protected. The reduced-interfacial. tension between oil and water also probably facilitates displacement of water fromthemetalsurfaceiby a protective oil film.

T he strongly-adsorbedhighly polar amine-and'acid' have beenfound to produce an excellentlubricating film which greatly reduces wear; In one'pu'mping well, use ofthe salt has already extended by a factor of'5 or 6"the average period between pumping rod-pulling jobs. In the well, the corrosion problems were minor, but perhaps just sufiicient to roughen the rubbing surfaces slightly and accelerate wear. to the simple lubricating actions of the strongly adsorbed films on both rubbing surfaces.

The parafiin-removing ability of the salt may be due to several factors. One of these is an increased paraffinsolubilizing power of the polyamine salt compared to salts of monoamines. The solubilizing power of the salts has been demonstrated in connection with the Alex 425 acids. These acids are not completely soluble in oil. The oil-insoluble materials are probably hydroxy acids. Whatever the nature of the materials, however, they are apparently drawn into oil solutions by a solubilizing action of the amine salt. It has been observed that the polyamines are more effective in solubilizing these oil-insoluble constituents of Alox 425 acids. Therefore, they are undoubtedly also more effective in solubilizing materials such as parafiin. Another factor which may account for increased paraifin removing ability is the presence of alcohols, ketones,esters. and the like in Alox 425 acids. These materials are fair'paraflin 'solvents. Since twiceas much" acid is required to neutralize Duomeen-T as is required to neutralize? octadecyl amine, for example, more of the alcohols, ketones and esters which. accompany the Alex 425 acids are present when the polyamine salt is employed. These solvents probably contribute in some degree to the improved paraffin-removing ability of the polya'mine salts of Alox 425 acids.

The principal explanation of the. paraffin-removing ability probably lies in the reduced interfacial tension between oil and water,'and. the consequent demulsifying action. It has been noted many times thatthe parafiin deposited in a well is generally-associated'with:considerable quantities of water.- Where little'water: is present, parafiin deposition is. rarely aproblemi' Apparently it is. an emulsion of pjarafiin and..waterwliichneposits: The amine-acid salt, by breaking this" emulsion causes its removal from wellswhere it is deposited."

When the term sa1t'is" employedwithmeference to a process, the term means either thepreferred reaction product or. the product formed in situ by use of the amine and acid separately. While the neutral salt is generally preferred, as much as twice the stoichiometric amount of either the amine or acidmay be presentand most of the advantages will still be retained.

The acids used in forming the salts of my invention are those produced by the process described in U. S.- Patents 1,690,768 and 1,690,769 issued to'Burwell. The hydro carbon feed to the oxidation process for" producing the itcid sd should be a petroleumfraction which is normally iqui class of hydrocarbons is preferred'since it produces acids in the desired molecular weight range containing from about 5 to about 20 carbon atoms per molecule. Hydrocarbons of a' paraffinic natureare preferred as feed stock to the oxidation process since they produce aliphatic acids having straight chains which align themselves to give closely-packed protective films.

In general, it is preferred to oxidize the hydrocarbon to such an extent that two phases separate. The lower phase has a higher content of acids which are superior for purposes of my invention, probably because of the presence of hydroxyl groups which make these acids much more polar in nature. Due to their higher polarity they are less oil-soluble and less susceptible to removal by oil from surfaces on which they have been deposited. Furthermore, their salts with polyamines aremore' polar, and hence more surface activeand less strongly solvated by oils. Although the highly oxidized acids are preferred, those produced by a light oxidation of a normally liquid petroleum..fraction produce unique'non-emulsifying salts with polyarnines; Salts'of these lightly-oxidized acids also possess some of the same powers of reducing interfacial tension and removing parafi'in possessed by salts of the highly oxidized acids, 'but to a lesser degree.

The reduced, wear might also be due- Kerosene is the preferred raw material; This The preferred polyamine is Duomeen-T. Othersatisfactory polyamines from Armour and Company are Duomeen-S and Duomeen-C. In 'Duomeen-T the' long hydrocarbon chain is derived from tallow acids and, hence, most of these chains are saturated. In Duomeen- S, on the other hand, most of the hydrocarbon chains are unsaturated since they are derived from soy bean oil acids.

With Duomeen-C, the acids are derived from coconut oil and constitute a mixture of saturated and unsaturated acids. Most of the hydrocarbon chains in Duomeen-T and Duomeen-S contain from 16 to 18 carbon atoms.

Since coconut oil is made up of acids having a wide range of molecular weights, the resultingamines have a correspondingly varied range of chain lengths, for example from about 8 to 18 carbon atoms. As indicated in the parent application previously referred to, a hydrocarbon radical of at least carbon atoms should be present. Such radicals insure the formation of. a film of sufficient thickness on the metal to resist penetration even by combinations of corrosive materials such as oxygen and hydrogen sulfide. The straightchain aliphatic hydrocarbon radicals are very much preferred to insure closer packing of the molecules forming the film. However, other hy-' drocarbon radicals having at least about 10 carbon atoms are also effective to a smaller degree.

The polar portion of the amine should contain at least two amino groups separated by from 2 to 4 carbon atoms. This portion may be heterocyclic in nature but preferably should be aliphatic since the salts of the non-cyclic aliphatic polyamines have surprisingly superior corrosion inhibiting abilities compared to salts of the cyclic polyamines.

So far as I have been able to determine, the aliphatic polyamines preferred in my invention may best be repre; sented by the formula:

In this formula R is a hydrocarbon radical, preferably aliphatic, containing from about 10 to '20 carbon atoms, N is a nitrogen atom, X is a radical selected from the group consisting of R, H and-RNHY, R is a hydrocarbon radical containing from 2 to 4 carbon atoms, H is a hydrogen atom and Y is a radical selected from the group consisting of H and R. The Duomeens are members of this class, having the simplified formula:

RNHR'NH The preferred amine is Duomeen-T havingthe formula:

R"NH(CH2)3NH2 As previously noted, R" in this formula is an aliphatic hydrocarbon radical containing from about 16 to .l8.carbon atoms.

The principal application of the disclosed salts is as inhibitors for corrosion by oxygen, hydrogen sulfide, carbon dioxide, carboxylic acids containing from 2 to 4 carbon atoms per molecule, or combinations of these individual corrosive materials. One or more of these materials, or combinations thereof, occur in various types of oil Wells. In treating such wells it is recommended that at least about 5 parts of the corrosion inhibitor be added per million parts of well liquids, including both water and oil. This concentration should be used whether the inhibitor is added in slugs, for example once a day or so, or is added continuously. Preferably, a preliminary period of treatment at higher concentrations up to 50 times the suggested steady rate should be employed for a week or so at the beginning of the treatment. If the oil well produces predominantly oil, an oil solution of the inhibitor should be added. If the well produces more than about 50 percent water, then a water-dispersible form of the inhibitor may be added. Such a form is described more fully and claimed in my copending application U. S.

Serial Number 335,161, previously noted. Although a treatment .of 5 parts per million produces appreciable protection which is, in many cases, quite adequate, for.

more severe corrosive conditions higher concentrations in the range of 10 to 50 or more parts per million may be used. In general, higher concentrations are required for systems consisting predominantly of oil than for systems which are substantiallyoil-free. The concentrations for preventing wear should be the same as those for inhibiting corrosion since the problem in both cases is to establish a protective film.

If wells have been treated, auxiliary field equipment such as flow lines, separators and the liquid space of tanks vapors such as theinside of casing and outside of tubing near the tops of wells, the vapor space of tanks or gas itor and an oil such as kerosene, be sprayed into the vapor space in an amount equal to about 1 gallon of solution per thousand square feet of metal surface to be protected.

The film which is formed in this manner can then be 7 maintained by injecting smaller amounts of from /2 to ,5 the volume of the original treatment at intervals of from about one week to one month, depending upon the severity of corrosion and erosion by flowing gases.

Another field application of the inhibitor is in drilling fluids to inhibit oxygen corrosion of drilling equipment, particularly the drill pipe. Concentrations of inhibitors should be approximately the same as for oil well treatments. Since the drilling fluid is recycled continuously, addition of inhibitor is necessary only to make up for the amount lost into the formations or on bit cuttings sepa-v rated from the drilling fluid. A similar application tested with considerable success was concerned with prevention of corrosion of the ballast tanks on submersible drilling barges. This also suggests the application to any marine vessel into which air-containing water is occasionally.

introduced.

Excellent slushing compounds can be prepared by adde ing the inhibitor to the greases or gels normally employed for this purpose. H The inhibitor may also be employed in refinery operaof exchangers, condensers or'the like, it is simply injected into the inlet to the equipmentpreferably in oil solution if the system is predominantly oil, and in a water-disper- Siblefortn if the system isipredominantly aqueous. If the inlet material is a vapor, spraying of the inhibitor into The inhibitor, being non-volatile, will then runthe stream as a fog is the preferred nretlffodof'injecti' Asfin other applications, introductionof'ithe inhibitor 8. geniq al, however;..I prefer toem'plbyapetroleum fraction such asfkero nc since; cost; is'fmuch less and the eftec tiv'en'essf is substantially the same;

iilventic'in'will be beitte'r' understood from consideration of e'followingfexamplesz ning of treatment of refinery equipment shoulcll beafron; a about 50 to 200 parts per million by weight'of" iqui an vapors treated. After a preliminary treatment at these E B concentrations; to establish inhibiting films, the concen? To jdetejrminef the effectivenessas a corrosion inhibitor nation can usually be reduced over a periodof tinieft'o a of the roposed salt of D'uomeen'e-T and Alex 42 5"acid's, value as low as about 5 parts per million, or even lbwer ll! comparedtosaltsdffother amines andacids, the followin exceptional cases. It will be understood that when ing tests were conducted. Into l-liter glass bottles reference is made to refineries, the term is employed 800ml. ofanaqueousjpercent'sodium chloride brine' broadly to include all petroleum processing equipment wereintroduc'ed;together: with. about 16-rnl'. of kerosene such as natural gasoline plants; sulfur'removin'g installa} containing various amounts, of the individual salts in-; tions or dehydrating apparatus; l3 dicated ingTable I. Polishedgandtar'ed mild steel test If the amine-acid salt is employed as a demulsifier, it panels, 1 inch by 1 inch" by figinch, were suspended in should preferably be introduced into the w'ell'producing thebrine by metal' rods'f fromwhich" the panels were inthe emulsion. In this way it can act on the water'and' oil" sula't'edby plastic washers." The'ro'ds were suppo'rted', in. atthe'bottom' of the well, thus preventing'ifirmation of turn; by-ins tigifiintb tlri rubber stoppers employed to the emulsion. At the same time, theamineacid'salt'acts; close the bottles. A stream" of corrosive gases" was. to prevent corrosion and parafiih depositioni It is'ip'osbubbled co'ntin ii'ouslythrough theliquids in the bottles sible, however, to add the salt'to' the emulsionafter it is at a latent about cubic foot per hour, while thc'tern; formed by injecting it into flow line's, separators; tajnks perature 'wasmaintained art-100 F. The corrosive gases. or the like. The amount' of salt. used as" ahemulsifier consisted of '2 percenthydrogen sulfide and 98 percentair. depends on the severity of emulsion in each case; In 35 The bottles were shaltn vigorously forv 15 consecutive general, however, it'is suggested'tha't concentrationsin the minutes every two hours. the end of 7 days, the range of 2 to 4 or 5 times those suggested forinhibiting panels were dipped 1n dllute inh bited hydrochloric" acid corrosion should be employed. solution' rubbed lightly to remove adhering scaleg. rinsed The amine-acid salt may be used to remove paraffin. in distilled waterifdried and; weighed. The results are from two locations in a well. One' location isthe inside 39 presented in Table I;

Table I e sh L a 1 Coneoi Grams Percent V Amine" Add salt, Inhlbi- Remarks p. p. m. tion, Av.

Control Inhibited ArmeenHT Alox'425: s00 ggggg} 98.0 emulslmi q l. ew: n do' 100 8%? 81822 94.8 if f pitting-8nd. etch Duomeen-T "do.-." 300 991d N0 emulsion, uniform-protcction.

Do 100' 31%}, 8:88;? 99.0 Do.

Do Oleic 0 g 92,1 Thick emulsion, panels etched,

wall of the tubing through which. the oil flows to thesur- A m HT is a trademark of Armour and Company face. The other is the pore spaceof formations through for a mixture of about 70 percent octadecyl amine and which oil flows to the well. Forreinovingparaffin from ab 30 pe hexadecylamine DuomeeneT and" inside tubing, the salt may be added' in ,thgsameways as Alox 425 have been previously identified chemically. suggested' for inhibiting corrosion. It h s Bri f ii d The greatly decreased emulsifying tendency of the A10): that the concentrations of salt suggested for inhibiting 425 acid salts is to be noted. The salt of Alex 425 acids corrosion a'r'e suitable for removin paraffin wherepar h e is particularly outstanding n a aflin problems are not too serious. Higher concentra' caused no emulsion at all, even at higher concentrations. tions, in the range of 2' to 4 or 5' times as great, are sug- This particular salt is also outstanding in that s h i gested for more serious cases of parafiiri deposition in il'lg D 1 P- is p il 300 P: P- 0f bi the salt of monoamines suchas Armeen-HT.

For removing paraffin from pore spaces, a solution, EXAMPLE H preferably 111 a petroleum fractlonsuch as kerosene, con: mining from about 0-001 0 Percent 111016" (i0 To compare the effectiveness of Alex 425 salts of alicf the filming-acid Salt Should be P p to the formflphatic polyamines to salts of cyclic polyamines, static tion and then be allowed to flow back out. A volume b ttl tests-were" nd ed as f ll 015 501115011 suficlcifint t0 fill the P 5 to a One-liter fior'ence flasks" were flushed free of air by fian Of a ast about 4 r 5 t uld b i j streams of nitrogen; Into-each flask approximately 1 liter The treating cyclfi y be i m r times of air-free 5 percent sodium chloride brine containing with either fresh or previously-used solution. Paraflin known amounts of hydrogen sulfide was introduced; The solvents such as carbon tetrachloride, carbon disulfi'dm corrosion inhibitor to be tested was then introduced, dis benzene the like y be P Y as a Solvent fOr the solved inSOml. of kerosene. A tared polished mild steel= salt, but since petroleum fractions are so eifective, use of p test panel, 1 inch by 1 inch. by inch, was then lowered the more expensive solvents is rarely justified'. 0 into each flask, supported by a glass hook which was in When a water block is to be removed from a formaturn held by the rubber. stopper used to seal the flask. tion, the procedure, concentrations and volumes should Eachpanel washeld in the oil layer 5 seconds at the-start be substantially the same as when parafiin is removed of the test andthen exposed to the brine phase for the from the pore space. The solvent for the salt maybe. 75 remainder of the- 7-day test: Results are reported in? a water solvent such as ethanol, acetone orthe like.

Table II.

Table ll I Weight Loss, Salt IDS Grams Percent Amine Cone, Conc., Inhlbi- Remarks p. p. m. p. p. m. tion, Av.

Control Inhibited 0.0267 0. 0007 Uniform protection. Dumeen T 0. 0343 0.0007 No emulsion. 0.0263 0018 Slight local attack Z-Heptadecyl Imldazoline 200 600 0.0266 0'0016 93.7 and pitting. Some 2H td 11H d n11 I emulsion' -epaecy-yroxyey .2

Imidazoline. 200 600 0.0266 8-8813 94.1 Do.

Although the concentration of the Duomeen-T salt of Alex 425 acids was only one-half those of the corresponding salts of the cyclic imidazoline derivatives, the degree of protection was superior. It will also be noted that the protection was uniform, whereas the salts of the cyclic amines permitted some local attack. The tendency of the cyclic amine salts to form slight emulsions at 200 p. p. m. concentration should be compared to the absence of emulsifying tendency of 300 p. p. 111. of the Duomeen-T salt noted in Example I. It is apparent that while the cyclic polyamine salts of Alox 425 acids are very good inhibitors, the aliphatic polyamine salts of the same acids are even better in several respects.

EXAMPLE III To determine the effectiveness of the Duomeen-T salt of Alox 425 acids as an inhibitor for corrosion due to low molecular weight carboxylic acids and carbon dioxide, the following test was made:

About 1100 ml. of an aqueous percent sodium chloride brine solution was placed in each of several 2-liter round-bottomed flasks together with about 900 ml. of kerosene. A reflux condenser was placed over each flask and the systems were freed of air by boiling the water while bubbling a stream of oxygen-free carbon dioxide through the liquids for a period of 2 hours. The rate of carbon dioxide introduction was about 1 cubic foot per hour. To the air-free liquids, 500 milligrams of glacial acetic acid were added (about 500 p. p. m. by weight based on the water phase). Then 100 milligrams of the salt of Duomeen-T and Alox 425 acids we're added to each of two of the flasks. None of the amine-acid salt was added to another flask used as a control. A polished, tared, mild steel panel was then suspended in thewater phase in each flask on a glass rod passing through a seal in the flask. A reflux condenser was placed on the flask and the flask heater adjusted to hold the temperature just at the boiling point of water. For 15 consecutive seconds out of each minute the panel was'raised into the oil phase. After 24 hours, the panels were cleaned, dried and weighed as described in Example I. The control panel lost 0.1500 grams. One of the panels in the flasks containing inhibitor lost 0.0082 grams; the other. lost 0.0020 grams. Thus, the average inhibition was 96.6 percent complete.

EXAMPLE IV The effectiveness of the Duomeen-T salt of Alex 425 acids was tested as an inhibitor of corrosion of surface equipment of a brine-disposal system in the East Texas field. Corrosion products indicated the corrosive agents to be hydrogen sulfide and air. The tests were conducted on a surface pipeline from a pump to a'disposal well. One test nipple was inserted a few feet downstream from the pump. Another was inserted a few feet upstream from the injection well, situated about /2 mile away. After 31 days exposure to the brine, these nipples were removed, cleaned and weighed. A second set of test nipples was substituted for the first set and injection of 15 the amine-acid inhibitor was started. The inhibitor was added as a kerosene solution containingA pounds of salt per gallon of solution. It was injected continuously into the pump suction through a small control valve. At-

tempted rates of injection were as follows:

First 3 days-1 quart of solution per 120 barrels brine. Next 2 weeksl quart of solution per 240 barrels brine.

Remainder of 32-day test-l quart of solution per 300 barrels brine.

These concentrations should have varied from about 22 p. p. m. by weight down to about 9 p. p. m. However, to treat the 81,000 barrels of brine according to this schedule should have required about '85 gallons of the solution.

Actually, only 68 gallons were injected because of difli-' Table III Weight Loss 40 7 Percent Nipple PosltioninLine Treated Inhibition V Grams Percent Total Nipples 1 and 2 contained sulfide scale and were pitted.

5U Nipples 10 and 20 were clean of sulfide scale and were not pitted. It will be apparent'that the air-sulfide corrosion, which cannot be prevented by most inhibitors now on the market,was effectively inhibited by the proposed amine-acid salt. Examination of the nipples indicated most of the inhibitor was deposited near the pump, only traces of the oily material being carried through the line to the nipple near the well. Much more effective inhibition near the well would undoubtedly have been'ootained by use of' the water-dispersible form described and claimed in my copending application U. S. Serial Nurnher 335,161. v p

' EXAMPLE v Pour points of oil solutions of amine-acid salts were depour points melting point of the Duomeen-T undoubtedly accounts in part for some of the decrease in pour point of solutions or" its salts. However, a decrease of about 30 r. in the melting point of one constituent of the salt in the solution could hardly be expected to produce a drop in pour point of 60 F. in straight oil solutions and 25 F. in the complex water-dispersible composition. The pour point reduction is particularly important in northern areas where the temperature frequently remains at or below about F. for considerable lengths of time. in such areas more dilute solutions of the water-dispersibie form should be employed. The pour point of this form can also be reduced further by increasing the alcohol content of'the preparation.

EXAMPLE VI The ability of the salt to break emulsions and prevent their formation was recently demonstrated in connection with a well in the Chocolate Bayou field of Texas. operator was using the salt of Armeen HT and Alex 425 acids as an inhibitor. The salt was added as a kerosene solution containing about 4 pounds of salt per gallon of solution. This inhibitor solution was added at a rateof about 2 quarts per day. The well production averaged about 6 to million cubic feet of gas per day, together with about 50 to 100 barrels of condensate and about 1 to 2 barrels of water. indicated by a low iron content of the water. the amount of inhibitor employed caused the formation of a slight emulsion. When this emulsion was treated in the laboratory with about 200 to 400 parts per million of the Duo mee n-T salt of Alex 425 acids, the emulsion broke immediately, thus demonstrating the ability of this particular salt to break even those emulsions causedby other amine salts. On the basis of this observation, the Duomeen-T salt of Alox 425 was employed in subsequent treatment of the well. No further emulsion troubles have been noted, thus demonstrating the emulsion-preventing ability of this salt.

EXAMPLE VII The water-block removing ability of an oil solution of: the salt of Duomeen-T and Alex 425 acids was determined in the laboratory by use of a core of Springer sand obtained from a well in the Velma field of Oklahoma. The core was drilled with oil, shipped in oil and stored in oil until used in the test. The core tested was drilled from the large core received, using oil as a lubricant during the drilling. The resulting test core was a cylinder. having a circular cross-section of 2.78 square centimeters and a length of 2.71 centimeters. This core was mounted in a rubber stopper through which a hole had been bored slightly smaller than the core. The stopper was, in turn, mounted in a tapered Lucite holder to which inlet and outlet connections were made. Various liquids were forced through the core under a diiferential pressure of approximately one atmosphere and at a room temperature of about 75 to 80 F. Permeability values were obtained by measuring the volume of liquid flowing out of the core over a short period of time, such as a minute or The- Corrosion control was good, as However,

12 two, and calculating the permeability which would account for this rate of flow. was forced through the core, the brine was one prepared by dissolving in fresh water 96,000 p. p. m. by weight of sodium chloride, 9,000 p. p. in. calcium chloride and 3,000 p. p. m. magnesium chloride. The hydrocarbon employed for flushing and as a solvent for interfacial-tem" sion-reducing agents was a narrow-boiling petroleum fraction containing hydrocarbons predominantly in the range having from 10 to 12 carbon atoms per molecule. The procedure and results were as follows:

(l) The permeability of the core to flow of the petroleum fraction was first determined to be millidarcies.

(2) One liter of the brine was forced through the core. The permeability of the core to the flow ofibrine at the end of this operation was 164 millidarcies.

(3) The petroleum fraction was again introduced and after 616 ml. had been forced through the core, the. permeability to the flow of the hydrocarbon was only 52 millidarcies, showing the core to be water-blocked.

(4) A solution of a polyoxyethylene sorbitol tetraoleate obtained from the Atlas Powder Company under the trademark G-2854 was then forced through the core to remove the Water block. This material is known to A reduce the interfacial tension between Water and oil. solution of 0.05 percent by weight in the petroleum fraction was employed; After 173 ml. of the solution had been forced through the core, the permeability to flow of the solution was found to be 179 millidarcies.

(5) The pure petroleum fraction was next pumped through the. core to determine if the improved permeabil ity was permanent.

the eifiuent hydrocarbon returned to its normal value. The permeability to fiow of the petroleum fraction at this time was 153 millidarcies.

(6) The blocking and cleaning steps were repeated, using a second- Atlas interfacial tension reducer with.

approximately the same results.

(7) The core was again water-blocked by introducing the brine. Permeability to the flow of the petroleum fraction after the blocking operation was 52.4 millidarcies.

(8) A solution containing 0.001 percent of the 1110- meen-T salt of A102: 425 acids in the petroleum fraction was then forced through the core. After 96 ml. had' been introduced, the permeability to flow of the solution was 53.7 millidarcies.

(9) The concentration of the salt was increased to Permeability,

Volume Through, ml.

Millidarcies (12) Upon flushing the core with the pure petroleum fraction, the permeability increased to 189.5 millidarcies instead of decreasing,.as had been characteristic of flushing after treatment with the Atlas compounds.-

(13) The interfacial tensions between the brine and the petroleum fraction containing various concentrations of the amine-acid salt were determined. The results are presented in Table V.

In every case where brine This flushing operation was con-- tinued until the interfacial tension between water and After introduction of 167 ml. of this solution,

It will be apparent that the amine-acid salt is somewhat more efiective than the non-ionic material for removing water block from formations. The reason for the greater effect is probably a stronger tendency to be absorbed on the sand grains, resulting in a greater ability to displace the water. Obviously, the concentration of the amine/acid salt in oil used for removing water blocks should be about 0.05 percent or more since a sharp increase in permeability occurred when the concentration was increased to this value from'the 0.01 percent previously used.

From consideration of the above description and examples, it will be apparent that I have accomplished the objects of my invention. A considerably superior corrosion inhibitor has been provided in that lower concentrations produce the same or greater uniformity and degree of inhibition produced by higher concentrations of other inhibitors. In addition, the inhibitor exerts a positive demulsifying action, as well as avoiding the emulsion problems often caused by other inhibitors. The gel-forming tendency of the inhibitor is so low that high concentrations in oil can be handled without danger of solidifying in cold weather. The material also acts to prevent paraflin deposition and to remove paraifin which has already been deposited. The ability of the salt to remove water blocks has also been demonstrated.

I claim:

1. The salt of a polyamine and a carboxylic acid, said acid being derived by liquid phase partial oxidation of a normally liquid petroleum fraction and said polyamine having the formula RNH(CH NH wherein R is a hydrocarbon radical containing at least about 10 carbon atoms, and x is an integer from 2 to 4 inclusive.

2. The salt of claim 1 in which said polyamine has the formula R"NH(CH NH wherein R" is an aliphatic hydrocarbon radical containing from 16 to 18 carbon atoms.

3. The salt of claim 2 in which said acid is derived by liquid phase partial oxidation of kerosene.

4. The salt of a polyamine and a carboxylic acid, said acid being derived by liquid phase partial oxidation of a normally liquid petroleum fraction and said polyamine having the formula RNH(CH NH wherein R is an aliphatic hydrocarbon radical containing at least about 10 carbon atoms and x is an integer from 2 to 4 inclusive.

References Cited in the file of this patent UNITED STATES PATENTS 2,290,412 De Groote et a1 July 21, 1942 2,303,366 Katzman Dec. 1, 1942, 2,583,399 Wachter et al. Jan. 22, 1952 2,587,546 Matuszak Feb. 26, 1952 2,614,980 Lytle Oct. 21, 1952 2,736,658 Pfohl et a1. Feb. 28, 1956