US3549532A - Weighted corrosion inhibitors - Google Patents

Description

United States Patent 3,549,532 WEIGHTED CORROSION INHIBITORS James R. Stanford and Paul G. Vogelsang, Jr., Houston, Tex., assignors to Nalco Chemical Company, Chicago, Ill., a corporation of Delaware No Drawing. Filed Sept. 11, 1967, Ser. No. 666,984 Int. Cl. C09k 3/100 U.S. Cl. 2528.55 4 Claims ABSTRACT OF THE DISCLOSURE Invert sugar is used as a weighting agent for an iron corrosion inhibitor in oil and gas wells.

In the production of oil, the corrosion of steel and other metal well equipment is caused by the action of certain types of sulfur bearing waters, dissolved carbon dioxide and natural brines. Various methods have been employed to prevent corrosion of such equipment. It is common practice to introduce an inhibitor at the well head into the annular space between the casing and the tubing in a well extending into a producing formation.

Liquid inhibitors which have been used are expected to flow to a producing zone in the well to mix with the corrosive liquids flowing therefrom and then flow up through the tubing to the surface.

In many wells, however, which have fluid in the bottom of the hole, light weight corrosion inhibitors cannot penetrate this fluid to inhibit corrosion in the bottom of the well. Hence, an inhibitor with a high specific gravity is needed. One type of corrosion inhibiting composition which has been employed involves the use of zinc chloride as a weighting agent for the corrosion inhibitor. The utility of this composition is limited to sweet wells because sour wells containing hydrogen sulfide or other sulfur-bearing constituents react with the zinc chloride to produce zinc sulfide which is undesirable Even in some sweet wells, chemicals containing zinc chloride are to be avoided. Concentrated solutions of zinc chloride are corrosive and if this concentrated solution becomes trapped at the bottom of the well, a corrosive condition can exist.

One of the objects of the present invention is to provide new and improved corrosion inhibiting compositions which are especially useful in oil and gas wells and are effective in both sweet and sour systems.

A further object is to provide compositions of the type described which give effective corrosion inhibition at low concentrations.

Another object is to provide weighted corrosion inhibiting compositions which have a specific gravity above that of the corrosive liquids sufficient to enable the inhibitor compositions to fall readily through the corrosive liquid.

Another object is to produce a corrosion inhibiting composition of the type described which has satisfactory non-emulsification characteristics.

Still a further object of the invention is to provide corrosion inhibiting compositions of the type described which do not contain inorganic salts as weighting agents.

An additional object of the invention is to provide a new and improved method of inhibiting corrosion of equipment in oil and gas wells. Other objects will appear hereinafter.

In accordance with the invention it has been found that invert sugar can be employed as a weighting agent for corrosion inhibitors and that the resultant compositions are especially effective for use in inhibiting corrosion of equipment in oil and gas wells.

The term invert sugar is used herein as defined in the Merck Index, seventh edition, page 557. The quantity of invert sugar employed should be sufficient to give a corrosion inhibiting composition having a weight of at least 9.5 pounds per gallon. Usually, the composition is prepared as a liquid with the corrosion inhibitor and the invert sugar, with or without other ingredients, dissolved in a suitable solvent. In most cases, organic solvents are employed, such as, for example, methanol, normal propanol, butanol, and the like. Good results are obtained by using mixtures of these solvents. Water is also used in admixture with these solvents. The resultant composition is preferably relatively insoluble in common oil and gas well fluids. This insolubility allows the composition to fall through the fluids to reach the bottoms of the wells being treated.

The quantity of invert sugar employed is preferably at least by weight of the composition and will usually be within the range of 20% to by weight of the composition.

It is also desirable in a composition of the type described to incorporate xylene sodium sulfonate as one of the ingredients. Sodium xylene sulfonate is xylene that has been sulfonated and neutralized with sodium hydroxide. It is a low foaming hydrotrope which is used in the formulation as a coupler for the invert sugar and corrosion inhibitor. A number of materials can be substituted, including sodium toluene sulfonate. sodium benzene sulfonate and certain low molecular weight organic phosphate salts. Although the sodium xylene sulfonate has a high specific gravity in concentrated solution, it is not high enough to be used as the only weighting agent.

It xylene sodium sulfonate or other substance having similar properties is employed as a component of the composition. the amount used is preferably within the range of 10% to 20% by weight of the composition.

It is also desirable to include in the corrosion inhibiting composition a demulsifying chemical which is eflective to prevent the formation of water-in-oil emulsions. The amount of this chemical can be rather small, usually within the range of .l% to 3% by weight of the composition.

The proportion of active corrosion inhibiting components in the composition is subject to variation but is usually within the range of 15% to by weight of the total composition.

In general. corrosion inhibitors which are useful for the purpose of the invention are organic iron corrosion inhibitors. These usually consist of high molecular weight organic carboxylic acids or sulfonic acids or amides or amine salts of such acids with ethylene diamine, diethylene triamine. triethylene tetramine, tetraethylene pentamine, dipropylene triamine. as well as ring compounds including imidazolines. Various examples of such corrosion inhibitors are given in US. Pat. 2,822,330 and US, Pat. 3,134,759.

A preferred type of corrosion inhibitor for the purpose of this invention comprises salts of (a) alkyl benzene sulfonic acids having 8 to 16 carbon alkyl groups and (b) partial amides of acyclic carboxylic acids having 1 to 54 carbons and organic amines having a plurality of basic nitrogens, said amines selected from the group consisting of polyalkylene polyamines having 3 to 10 amino groups and 2 to 6 carbon alkylene groups and N-aminoalkyl substituted heterocycles wherein the aminoalkyl group has the formula H(HNR---) wherein R is an alkylene group of 2 to 6 carbons and x is a small whole number, substantially all of which are in the form of amine salt groups with said alkyl benzene sulfonic acids, and 10 to by weight, based on said salts, of free acylic carboxylic acids having 1 to 54 carbon atoms.

Corrosion inhibitors of this type are disclosed and claimed in a copending application, Ser. No. 358.119, filed Apr. 7, 1964, now Pat. No. 3,410,024 the specification of which is incorporated herein by reference in its entirety.

A particular type of corrosion inhibitor which has been found to be Well suited for the practice of this invention is a tall oil amide of diethylene triamine which has been neutralized with dodecylbenzene sulfonate and admixed with a mixture of polymeric polycarboxylic acids containing 2 to 3 mer units per molecule, an acid value of 150- 690, a saponification value of 190-450 and an iodine value of -50.

Organic water-in-oil demulsifying agents which can be incorporated into the compositions of the invention are disclosed in numerous patents, including among others, US. 3,042,625, US. 3,098,827, U.S. 3,210,291, U.S. 3,206, 412, U.S. 3,202,615, US. 3,166,516 and US. 3,278,637.

These demulsifying agents which are usually referred to as emulsion breakers are commonly employed for breaking water-in-oil emulsions. One type of water-in-oil demulsifying agent which is particularly useful in compositions of the present invention is a mixed ester of a polycarboxy acid containing 554 carbon atoms and (a) an oxyalkylatcd rosin acid containing 2-4 carbon atoms in the oxyalkyl groups, and (b) an oxyethylated nonylphenol-formaldehyde resin.

The invention will be further illustrated but is not limited by the following examples in which the quantities are given by weight unless otherwise indicated.

EXAMPLE I A tall oil amide was prepared and reacted with dodecyl benzene sulfonate and Emery 336313 acid.

This product constituted the active iron corrosion inhibitor and was weighted by mixing it with an invert sugar and xylene sodium sulfonate. Solvents were also added to form a liquid concentrate adapted to be added directly to oil and gas wells. In addition, a small amount of a water-in-oil demulsifier was incorporated into the final composition.

The proportions of the various reactants and components of the final product were as follows:

Components: Percent of final product by wt. Crude tall oil 7.09 Polyamine H solid 3.55 Methanol 1.42 Emery 3363B acid 11.04 Dodecyl benzene sulfonic acid 4.96 Diethylene triamine 2.20 n-Propanol 2.75 Butanol bottoms 5.52

Water 15.44 Xylene sodium sulfonate 15.44 Invert 50 (invert sugar) 30.30 Water-in-oil demulsifier .29

The water-in-oil emulsion demulsifier used in the foregoing example was an oxyalkylated (containing 2 to 3 carbon atoms in the oxyalkylene groups) tall oil (Acintol FA-l) ester of tripentaerythritol, blended with polymerized vegetable fatty acids (Century D-75 acid).

In the foregoing example other acids can be used in place of the Emery 3363D acid, for example, Century D-1475 acid, Century D-75 acid, Emery 3362D acid, TX-3650 acid, and Emfac 1202 acid. Likewise, other amines can be employed instead of Polyamine H Solid and diethylene triamine, e.g., Amine AL-l, triethylene tetramine, tetraethylene pentamine, and dipropylene triamine.

The compounds which are described by trade name have the following compositions:

(1) Century D-1475 acid is a mixture of vegetable oil fatty acids (essentially C -C fatty acids) having an acid value of 188-203, a saponification value of 190- 210 and an iodine value of 40-50.

(2) Century D-75 acid is a mixture of polymerized vegetable fatty acids containing a major proportion of dimerized and trimerized linoleic and linolenic acids and (ill having an acid value of 155-169, a saponification value of 186-192, and an iodine value of 40-48. Century D- acid is a similar mixture of polymerized vegetable fatty acids containing a high percentage of timer. It has a. saponification value in a range from 125-148 and an iodine range of 42-50.

(3) Emery 3363D Acid is a mixture of polybasic acids derived from natural fats and oils. The acid mixture has an average of about two carboxyl groups per molecule, an acid value of. 208, a saponification value of 252, and an iodine value of 11.

(4) Emery 3362B Acid is a blend of low molecular weight acids of the fatty acid series from formic acid through heptanoic acid with formic acid in preponderance. The blend has an acid value of 690.

(5) TX-3650 is a mixture of organic acids obtained as a wax oxidate and having a saponification number of 440-450 and a neutralization number of 225-250.

(6) Amine AL-I is a mixture of N-aminoethyl-piperazine, N-hydroxyethylpiperazine, N-aminoethylethanolamine and higher homologues of these compounds. The mixture has a total nitrogen content of 29.730.8% and a titratable amine content of 16.4 meq./gm.

(7) Emfac 1202 is a pelargonic acid which is the normal C fatty acid, having an acid value of 345-360 and an iodine value of 1 maximum.

(8) Polyamine H Solid is a mixture of polyethylene polyamincs of the series H N(RNH) H wherein the polyethylene polyamines are higher h0II10lOg -lES than tetraethylene pentamine.

The compositions of the invention were evaluated by semidynamic corrosivity tests, also known as corrosion inhibitor wheel tests.

This test evaluates the corrosivity of produced fluids by determining weight loss of metal specimens exposed in sealed vessels containing the fluids. The sealed vessels are mounted on a wheel or mounting-board and maintained under constant rotation and temperature throughout the exposure period.

The effectiveness of inhibitors is rated by comparing weight losses of similar specimens in inhibited and uninhibited samples of fluid. The procedure is as follows:

Test cells are filled with fresh fluids at the same oil/water ratio as exists in the field samples. (If a sizeable vapor space exists in the sample bottles as received, the fluids in the bottles are purged with inert gas to remove oxygen. The purged samples then are saturated with carbon dioxide, if they are from sweet gas condensate wells, or are saturated with hydrogen sulfide, if they are from sour wells.)

Inhibitors for evaluation are introduced into the test: cells at various dosages. Control test cells containing no chemical also are used, to establish a base corrosion rate from which relative percent protection provided by the chemicals can be computed. All tests normally are run in duplicate.

Weighed metal specimens are inserted and the test cells mounted on a rotating wheel." The sealed test vessels are maintained under constant temperature and rotation rate throughout the exposure.

Following exposure, the specimens are removed, degreased in acetone or benzene and then scrubbed with soap and water. If corrosion products adhere to the surface, they are removed by dipping the coupons in inhibited technical grade hydrochloric acid. After cleaning, the coupons are immersed in alcohol, then in acetone or benzene, dried and reweighed.

(wt. loss uniuhibitedwt loss with inhibitor) Wt. loss uninhibited X percent protection (2) Surface area of specimen per unit volume-11.41 sq.

ft./bbl.(l cmF/IS ml.) maximum (3) Temperature range-Room temperature to 200 F.

(4) Type specimen-Mild steel plate or carbon steel rod (5) Surface of specimenSandblasted (plate) or polished (rod) (6) Exposure period24 hours (7) Rotation rate24 r.p.m.

Corrosion rates determined in this test typically are in excess of rates encountered in the field. This acceleration and magnification of corrosive attack shows up differences between chemicals and thus is an effective screening procedure.

Experience indicates that the following rough correlation exists between corrosivity ratings on this test and actual corrosivity of fluids in the field:

TABLE I-a Weight loss in this test: Typical corrosiveness in field Less than 10 milligrams Mild 10-20 Moderate More than 20 Severe The following rough correlations also appear to exist between percent protection as furnished by inhibitors in this laboratory test, and the performance of the inhibitors in the field:

TABLE Ib Protection by inhibitor in lab tests: Inhibitor performance in field 90% or more Excellent 75% to 89% Good 50% to 74% Fair Less than 50% Poor The tests in the following examples were conducted at about 160 F. with mild steel plate for various time periods and in various corrosive mixtures.

EXAMPLE II The product of Example I was tested as a corrosion inhibitor by the wheel test previously described in a corrosive fluid consisting of equal volumes of kerosine and sweet brine (5% sodium chloride) saturated with carbon dioxide for a total of 24 hours at 160 F. At a concentration of inhibiting composition of 100 p.p.m., the weight loss was 2.9 milligrams and the percent protection was 96%. The weight loss of a blank steel specimen was 69 milligrams. Protection was also afforded at a concentration of 10 parts per million (p.p.m.) under the same conditions.

EXAMPLE III The procedure was the same as in Example II except that the corrosive fluid consisted of equal parts by volume of kerosine and sour brine (5% sodium chloride) saturated with hydrogen sulfide. At a concentration of 10 p.p.m., 72% protection was afforded, at 50-100 p.p.m. of the corrosion inhibiting composition 85-87% protection was obtained.

EXAMPLE IV The corrosion inhibiting composition of Example I was tested in the manner previously described on an oil well fluid having an oil-water volume ratio of 102190 saturated with hydrogen sulfide gas. The overall exposure time was 24 hours. At a concentration of inhibiting composition of 200 p.p.m. 94% protection was afforded. The weight loss at this concentration was 1.1 milligrams. The weight loss of the blank was 17.1 milligrams.

EXAMPLE V The procedure was the same as in Example IV except that the oil well fluid was not saturated with hydrogen sulfide gas but was tested in the form that it was obtained from the field. In this case, concentrations of 10- 200 p.p.m. of the corrosion inhibiting composition of Example I afforded 96% protection. At a concentration of p.p.m. the weight loss of the steel specimen used was 0.8 milligram whereas the weight loss of the blank Without any corrosion inhibiting composition was 22.1 milligrams.

EXAMPLE VI An oil well fluid containing equal parts by volume of oil and water as obtained from an oil well was saturated with hydrogen sulfide and tested for 72 hours at F. with various concentrations of the corrosion inhibiting composition of Example I in the manner previously described. At a concentration of 200 p.p.m. the weight loss of the steel specimen was 4.1 milligrams as compared with 32.8 milligrams for a control specimen where no corrosion inhibiting composition was added.

The compositions of the invention were also tested for emulsification tendencies in various types of hydrocarbon and water or brine mixtures and found to be substantially non-emulsifying.

It will be seen that the invention provides a weighted corrosion inhibiting composiiton that does not contain inorganic salts and can be used for the purpose of inhibiting corrosion in both sweet and sour hydrocarbon-water systems. The corrosion inhibiting compositions of the invention have good film persistency and are effective at low concentrations. They can be used at concentrations within the range of 10 to 100,000 p.p.m. Corrosion inhibition may be achieved by either a continuous low concentration of inhibitor being in contact with the metal to be protected or by using a high concentration of inhibitor in a batch or squeeze type system. When the chemical is applied continuously, the concentration of inhibitor in the fluid is preferably within the range of l0500 p.p.m. When the chemical is used in a squeeze or batch type treatment the preferred range falls within the range of 10,000 to 100,000 p.p.m.

The high specific gravity of the corrosion inhibiting composition, together with its good non-emulsification characteristics makes it effective in penetrating the well fluids in order to provide corrosion inhibition at the bottom of the well.

The invention is hereby claimed as follows:

1. A corrosion inhibiting composition consisting essentially of 15% to 45% by Weight of an organic iron corrosion inhibitor, 20% to 45% by weight invert sugar, 10% to 20% by weight of a compound from the group consisting of xylene sodium sulfonate, sodium toluene sulfonate, and sodium benzene sulfonate, 0.1% to 3% by weight of an organic chemical demulsifying agent which is effective to prevent the formation of water-in-oil emulsions, and a mutual solvent consisting essentially of water and a lower alkyl monohydric alcohol, said organic iron corrosion inhibitor forming persistent films on metals and being soluble in the proportions used in said solvent but only slightly soluble in fluids found in petroleum and gas wells, and said composition weighing at least 9.5 pounds per gallon.

2. A corrosion inhibiting composition consisting essentially of 15% to 45% by weight of an organic from corrosion inhibitor comprising a tall oil amide of diethylenetriamine which has been neutralized with dodecylbenzene sulfonate and admixed with a compound from the group consisting of fatty acids and a mixture of polymeric fatty acids containing 2 to 3 mer units per molecule, an acid value of 150 to 690, a saponification value of to 450 and an iodine value of 0 to 50, 20% to 40% by weight of invert sugar, 10% to 20% by weight of xylene sodium sulfonate, 0% to 3% by weight of a demulsifying chemical which is effective to prevent the formation of waterin-oil emulsions, and a mutual solvent consisting essential- 1y of water and a lower alkyl monohydric alcohol from the group consisting of methano, normal propanol, and

butanol, said composition weighing at least 9.5 pounds per gallon.

3. A process of inhibiting corrosion of equipment in oil and gas wells which comprises introducing into such wells an effective amount sufiicient to inhibit corrosion of a weighted corrosion inhibiting composition as claimed in claim 1.

4. A process of inhibiting corrosion of equipment in oil and gas wells which comprises introducing into such wells on effective amount sufiicient to inhibit corrosion of a weighted corrosion inhibiting composition as claimed in claim 2.

References Cited 3/1957 Shock et a] 2s2 s.55 15 2,839,465 6/1958 Jone? 252-855 2,877,185 3/1959 Krumrei et a1 252137 3,098,827 7/1963 Kirkpatrick et al. 252341 3,378,488 4/1968 Nimerick 2528.55

3,412,024 11/1968 Stanford 252--8.55

OTHER REFERENCES The Merck Index, 7th edition, published by Merck and 1 Co., Inc., Rathway, N.J., 1960, p. 557.

LEON D. ROSDOL, Primary Examiner P. E. WILLIS, Assistant Examiner 2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 549, 532 Dated December 22 1970 Inventor) James R. Stanford 80 Paul G. Vogelsang, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3,

Column 6, line 75, f'methano" should read methanol line 21, "5-54 should read 4-54 Signed and sealed this 23rd day of March 1971 (SEAL) Attest:

WILLIAM E. SCHU'YLER, J

' EDWARD M.F1'.|E'I'CHER,JR.

Commissioner of Patent Atteating Officer