US3749554A - Method for reducing erosion and corrosion of metal surfaces - Google Patents

Abstract

EROSION AND CORROSION OF METAL SURFACES EXPOSED TO A FLOWING STREAM OF HOT GASES CONTAINING DISPERSED PARTICLES OF SOLID MATERIAL ARE REDUCED BY INTRODUCING INTO THE FLOWING STREAM AN ADDITIVE THAT DECOMPOSES AT THE TEMPERATURE AND PRESSURE OF THE GAS TO RELEASE AMMONIA OR A VAPOROUS AMINE AND FORM A RESINOUS RESIDUE. THE ADDITIVE IS PREFERABLY INTRODUCED INTO THE GAS IN AN INERT CARRIER LIQUID.

Description

United States Patent US. Cl. 212.5 R 13 Claims ABSTRACT OF THE DISCLOSURE Erosion and corrosion of metal surfaces exposed to a flowing stream of hot gases containing dispersed particles of solid material are reduced by introducing into the flowing stream an additive that decomposes at the temperature and pressure of the gas to release ammonia or a vaporous amine and form a resinous residue. The additive is preferably introduced into the gas in an inert carrier liquid.

This is a division of application Ser. No. 44,661 filed June 8, 1970, now issued as Pat. No. 3,653,452.

This invention relates to inhibiting erosion and corrosion of metal surfaces, and more particularly to inhibiting erosion and corrosion of metal surfaces exposed to a hot flowing gas containing dispersed particles of solid material. This invention further relates to reducing erosion and corrosion of drill pipe employed in gas drilling wells into high-temperature subterranean formations, and especially in the gas drilling of wells into steam-bearing formations.

Substantial erosion and corrosion of metal drill pipe is often experienced when gas drilling into high-temperature subterranean formations. In gas drilling, air, nitrogen, natural gas, or other gaseous fluids are utilized as the drilling fluid. The gas is passed from the surface downwardly through the drill pipe, outwardly through a rotary bit attached to the lower end of the drill pipe, and then upwardly through the annulus on the exterior of the drill pipe at a pressure and volumetric flow rate sufficient to cool the bit and lift the particulate drill bit cuttings to the surface, but which are not sufliciently high as to cause fracturing of the formation.

Gas and entrained solid cuttings pass upwardly through the well annulus at velocities which are typically between and 100 feet per second, or higher. The particles of solid material transported at these gas velocities are highly abrasive. Also, high temperatures are often encountered. Bottomhole temperatures above about 300 F. are not unusual, and are sometimes in excess of 500 F. These conditions, combined with the corrosive brines, sulfurous compounds and oxygen which are often present in the bore hole, are conducive to excessive erosion and corrosion of the drill pipe, casing and other metal parts. The life expectancy of drill pipe employed under these conditions is relatively short, requiring frequent inspection and replacement. Furthermore, an even more serious problem is the failure of the drill pipe in service wherein the drill pipe breaks leaving a lower section of the drill pipe in the well. Drill pipe failures interrupt the drilling operation, often requiring expensive fishing operations to recover the pipe remaining in the well, and on occasion, if the fishing operation is not successful, necessitate abandonment of the well.

The problems associated with gas drilling are further accentuated when drilling into steam-bearing strata, such as are encountered in developing geothermal reservoirs. Not only are the temperatures of these strata generally above about 500 F., but also steam enters the well from the surrounding strata increasing the velocity of the gas passing upwardly in the well annulus to as high as sonic velocities, which further increases the erosion of the metal surfaces exposed to the solids-containing gas. The intrusion of steam into the well seriously promotes drill pipe erosion and corrosion, and in many instances the presence of steam is so detrimental that gas drilling becomes impractical requiring the use of slower and more costly techniques employing liquid or mud-type drilling fluids.

Various techniques for ameliorating the problems associated with high velocity, solids carrying gas streams have been attempted. Most of this effort, however, has been restricted to changing the performance characteristics of the metal parts exposed to the flowing stream. For example, it has been proposed to make the metal parts thicker, thereby prolonging the life of the part, or alternatively to harden the metal surface by heat treating, or with special alloys, and. to introduce corrosion inhibitors into the flowing stream to at least reduce corrosion. In gas drilling, it has been proposed to reduce the circulating gas velocity by incorporating foaming agents into the drilling gas. However, these techniques are costly and at best are only marginally effective. Thus, need exists for an inexpensive method for reducing erosion and corrosion of metal surfaces contacted by a relatively hightemperature, high-velocity, solids-carrying gas stream.

Accordingly, it is a principal object of this invention to provide a method for reducing erosion and corrosion of metal surfaces exposed to a flowing gas stream containing dispersed solid particles. It is another object of the invention to provide a method for reducing erosion and corrosion of metal surfaces exposed to a flowing stream of relatively high-temperature gas and dispersed solid abrasive particles. Other objects and advantages of the invention will be apparent to those skilled in the art from the description thereof which follows.

The aforementioned objects and their attendant advantages can be realized by introducing into the flowing gasparticle stream an additive that decomposes at the temperature and pressure of the gas: to release ammonia or a vaporous amine and form a resinous residue. The additive is preferably introduced into the gas in an inert carrier liquid. While the method of this invention has broad general application in reducing corrosion and erosion of metal surfaces that are exposed to particle-containing gas streams, it is especially useful in reducing erosion and corrosion of metal drill pipe used in gas drilling wells into high-temperature earth formations, such as are encountered in gas drilling wells into subterranean steambearing formations.

While the exact mechanism by which the method of this invention ameliorates erosion and corrosion is not completely understood, it is believed that the ammonia or vaporous amine released when the additive is heated to a temperature above its decomposition temperature contacts the metal surfaces exposed to the gas and functions as a corrosion inhibitor protecting these metal surfaces from attack by corrosive and oxidative agents in the gas, and that the non-volatilized portion of the additive reacts or polymerizes to form a resinous residue that is deposited in part on the exposed metal surfaces and on the solid particles suspended in the gas, thereby reducing erosion of the metal parts. However, while the exact mechanism by which the invention functions to reduce erosion and corrosion may not be completely understood, it has nevertheless been demonstrated that erosion and corrosion of metal parts exposed to a solids-carrying gas stream can be effectively reduced by the practice of the invention.

Ma'ny'organic compounds exhibit the properties required of the additive used in the practice of this invention, and additives suitable for use under specific application conditions can be determined by a simple screening test, which is hereinafter more fully described. Generally, the organic compounds useful as erosion and corrosion inhibitors are tertiary amines having molecular weights above about 260, and usually above about 300. Organic compounds that have been found particularly useful in the practice of the invention are ammonia or amine salts of a complex tertiary amine containing at least one functional carboxylic acid group.

More preferably, the erosion and corrosion inhibitor used in the practice of the invention is an ammonium or an amine salt of a complex tertiary amine having at least one univalent radical containing a functional carboxylic acid group with an ester, amine or amide linkage, and the tertiary amine can also contain one or more univalent organic radicals, or a bivalent organic radical which forms a ring structure with the tertiary nitrogen. These compounds can be conveniently represented by the following generalized formula:

wherein:

R is a univalent organic radical selected from Column 1 of Table 1;

R is a univalent organic radical selected from Column 2 of Table 1;

R is a bivalent organic radical selected from Column 3 of Table 1;

n is 1, 2 or 3;

m is 0, 1 or 2;

p is or 1; and

the sum of n +m+2p equals 3.

Thus, in one preferred embodiment of the invention, the tertiary amine is comprised of a tertiary nitrogen having attached thereto at least one univalent organic radical containing a carboxylic acid functional group selected from Column 1 of Table 1, and the tertiary nitrogen can also have attached thereto one or tWo univalent radicals selected from Column 2 of Table 1, or a bivalent radical selected from Column 3 of Table 1, which forms a ring structure with the tertiary nitrogen.

TABLE 1 Column 1 Column 2 Column 3 Carboxylic acid Univalent Bivalent radicals radicals radicals R4O0CR;COOH R OOH I|i4 --R4 R0 R C O 0 R11 --R4 I R CONH2 -R4N RaCOOH 0 O -R; R4

R4NHCR3COOH N hexane, and the like; and bivalent aromatic radicals such as 2 phenolethylene, 2,3 diphenoloctylene, paramethylphenol-Z-octylene, 1,4 diphenyltetracosylene, bivalent paradiamylbenzene, and the like;

R represents an alkylene containing from 1 to 4 carbon atoms, exemplary of which are methylene, ethylene, propylene, methylethylene, butylene, and the like;

R represents a bivalent hydrocarbyl radical containing from 1 to 50 carbon atoms, and can include bivalent aliphatic, alicyclic and aromatic radicals, specific examples of which are listed in the above definition of R R represents a univalent hydrocarbyl radical containing from 1 to 50 carbon atoms, and can include univalent aliphatic, alicyclic and aromatic radicals; and

R represents a trivalent aliphatic hydrocarbyl radical containing from 1 to 4 carbon atoms having a univalent terminal carbon and a bivalent terminal carbon.

Preferred univalent organic radicals containing a functional carboxylic acid group are obtained from the hydrocarbon residue of dimerized conjugated hydrocarbons containing between about 8 and 44 carbon atoms. Also preferred are univalent organic radicals obtained from conjugated fatty acids such as linoleic acid, isolinoleic acid, and the like. 7

The carboxylic acid functional groups in the abovedescribed tertiary amine are neutralized by reaction with ammonia or a water-soluble amine containing from 1 to 15 carbon atoms to form ammonium or amine salts of the tertiary amine. Exemplary of the amines which can be employed are morpholine, substituted morpholines having from 5 to 10 carbon atoms, pyrrolidine, pyridine, and simple primary, secondary and tertiary amines having the following formula:

wherein R R R are the same or different substituents selected from hydogen; an alkyl containing about 1 to 4 carbon atoms, exemplary of which are methyl, ethyl, propyl, isopropyl and butyl; an aminoalkyl containing about 2 to 4 carbon atoms, exemplary of which are aminoethyl, aminopropyl, aminoisopropyl and aminobutyl; and an hydroxyalkyl containing about 2 to 4 carbon atoms, exemplary of which are hydroxyethyl, hydroxypropyl, hydroxyisopropyl, and hydroxybutyl.

A preferred class of compounds for use in the practice of the invention are the polyamine salts of an acidic triester of a trialkanol amine, which are generally represented by the following formula:

R400 CRaC 0 OELA N-R4O O CRaGO OH.A.

R40 OCRaCO OH.A

wherein R and R are defined above and A is ammonia or a water-soluble amine containing from 1 to 15 carbon atoms, exemplary of which are the above-described. amines. In a particularly preferred embodiment R in obtained by esterifying triethanolamine with a long-chain dibasic acid obtained by dimerizing linoleic or isolinoleic acid.

The preparation of polyamine salts of a complex tertiary amine having the above generalized formula, as well as other exemplary polyamine salts which can be used in the practice of this invention, are disclosed in US. Pat. No. 3,151,138, which is herein incorporated by reference.

Organic compounds which possess the requisite properties of decomposing to release ammonia or a vaporous amine and form a resinous residue under specific application conditions can be identified by a relatively simple screening test. In accordance with this test, grams of the selected organic agent is dispersed in 100 milliliters of water and placed in a 250 milliliter reaction vessel. This material is then heated to a temperature corresponding to the application temperature under a pressure corresponding to the application pressure. The vapors evolved are collected and analyzed for the presence of ammonia or amine, and the nature of the residue remaining in the reaction flask is visually observed. Those compounds which release ammonia or a vaporous amine and form a tenacious resinous material under the test conditions can be employed to reduce erosion and corrosion in a flowing stream of gas containing dispersed particles of solid material under conditions of temperature and pressure corresponding to the test conditions.

In the practice of the invention, the organic agent can be injected directly into the flowing gas-particle stream, or alternatively, the agent can be mixed with a carrier liquid and this admixture injected into the gas stream. While some or the organic agents useful in reducing erosion and corrosion decompose to release ammonia or a vaporous amine and form a resinous residue at temperatures less than about 200 F., the method of this invention is most applicable to reducing erosion and corrosion of metals contacted by a solids-containing gas at a temperature in excess of 250 F., and more preferably in excess of 300 F.

The carrier liquids with which the organic agents are admixed preferably are relatively inert to the organic agents, are relatively stable at the application conditions, and are sufliciently polar to facilitate dispersion of the organic agent in the liquid. Exemplary of the carrier liquids that can be employed in the practice of the invention are water; ammonia; monohydroxy aliphatic alcohols having from 1 to 10 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, octanol, and the like; aliphatic amines having from 1 to 10 carbon atoms, such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, hexylamine, octylamine, and the like; aliphatic carboxylic acids having from 1 to 10 carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid, caproic acid, and the like; aliphatic aldehydes having between 1 and 10 carbon atoms, such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and the like; ketones having from 1 to 10 carbon atoms, such as acetone and methyl ethyl ketone, and the like; and mixtures thereof, and especially aqueous mixtures thereof. Where the gas into which the additive is injected contains appreciable amounts of oxygen, such as the case in air drilling, it is preferred that the carrier liquid be non-flammable to avoid the formation of explosive mixtures.

In general, the organic agent is admixed with the carrier liquid in the proportion of about 0.001 to 25 weight percent of organic agent based upon the weight of the mixture, and more preferably between about 0.005 and about 10 weight percent. Since many of the organic agents and carrier liquids are slightly acidic, it is preferred that the pH of the liquid dispersions be maintained between about 7 and 12, and more preferably between about 8 and 11; however, it is recognized that in some instances it may be advantageous to maintain the pH of the dispersion below 7.

The erosion and corrosion inhibiting additive can be prepared at the location of use, or alternatively, a concentrated mixture of the organic agent in carrier liquid can be shipped to the site and then diluted with an additional quantity of carrier liquid. Although the additive mixture can be introduced into the flowing gas stream in any convenient manner that provides distribution of the additive in the gas, preferably the additive is injected into the gas in aerosol form, e.g., the additive is sprayed into the gas stream by means of a spray nozzle, or is dispersed into a separate quantity of gas and this aerosol mixture introduced into the flowing stream of gas. Erosion and corrosion of the metal parts exposed to a flowing stream of gas containing dispersed particles of solid material can be substantially reduced by introducing into the gas from about 0.001 to 1 gallon of the above described additive mixture per 1,000 standard cubic feet of gas. The exact amount of additive necessary in any particular application can be determined by laboratory tests simulating the application conditions, or by determining the required treatment by tests conducted under the actual application conditions. However, in either case, it is desired that the quantity of additive employed be sufficient to effect a substantial reduction in the erosion and corrosion of the metal parts contacted by the solids-containing gas.

The erosion and corrosion inhibiting method of this invention is particularly useful in reducing erosion and corrosion of metal parts employed. in gas drilling wells into high temperature subterranean formations, such as geothermal reservoirs. .In this application, the additive is injected into the circulating gas at the surface and passed downwardly through the drill pipe with the gas. Preferably, the additive is introduced into the gas in an amount equivalent to about 0.001 to 1 gallon additive, i.e., organic agent in the carrier liquid, for each 1,000 standard cubic feet of gaseous drilling fluid. The erosion-corrosion inhibitor can be injected into the circulating medium at the beginning of the drilling process, however, it is preferred to defer inhibitor injection until the bottomhole temperature of the well exceeds about 250 F., and more preferably until the bottomhole temperature exceeds 300 F., or even 400 F.

Other agents can be introduced into the drilling gas without adversely affecting the performance of the erosion-corrosion inhibitor. For example, small amounts of particulate matter can be injected into the circulating medium to impart desired caking properties to the gas.

Also, a minor amount of an inorganic friction reducing,

agent, such as graphite, molybdenum disulfide, andthe like, can be injected into the circulating medium. Also, foaming agents can be added to the circulating gas to improve its capacity for carrying solids from the drilling zone to the surface.

The invention is further described by the following examples which are illustrative of specific aspects of the invention and are not intended as limiting the scope of the invention defined by the appended claims.

EXAMPLE 1 The effectiveness of the method of this invention in reducing erosion and corrosion of drill pipe used in air drilling wells is demonstrated by a series of well drilling tests. In each test a well is drilled through a subterranean formation to a depth of between about 4,000 and 6,000 feet with a rotary bit mounted on 4 /2 inch drill pipe. Each well traverses several steam-bearing zones. Air is supplied to the drill pipe from a bank of five primary and two booster compressors at a rate of approximately 3,000 standard cubic feet per minute and at a pressure of about to 1,250 p.s.i.g. Approximately 21 gallons per hour of erosion-corrosion inhibitor and 2 pounds per hour of finely divided graphite are injected into the air employed in drilling wells number 3 through 10, the additive injection being commenced when the bottomhole temperature reaches 500 F. No additive is employed in drilling wells number 1 and 2.

TABLE 2 Pipe sections Inhibitor Found un- Replacerate, Observed, satisfactory, ment, factor Well number gallons/hr. number number percent The addition of the erosion-corrosion inhibitor to the circulating drilling gas reduced the erosion, pitting and corrosion of the drill pipe resulting in a substantial reduction in the number of drill pipe sections requiring replacement.

EXAMPLE 2 The ability of various complex tertiary amine salts to release ammonia or a vaporous amine and to form resinous residues at selected temperatures is demonstrated by a series of laboratory tests. In each test grams of the selected compound is dispersed in 100 ml. of water and placed in a 250 ml. reaction vessel. The dispersion is heated to a preselected test temperature at atmospheric pressure, and the vapor evolved is collected and analyzed by gas-chromatograph for the presence of amine. The inhibitor is maintained at the test temperature for one hour, and the nature of the residue in the reaction vessel visually observed. The results of these tests are reported in Table 3.

TABLE 3 Test Amine Test temperapresent Nature of No. Tertiary amine salt ture, F. in vapors residue 1 Ethylene diamine salt of 260 Yes Resinous.

TDT 2 N%]%t%lamin0ethanol salt of 390 Yes Do. 3 Morpho line salt of TDT. 270 Yes Do. 4... Pyridine salt of TDT 250 Yes Do. 5 Di le igi rl lene triamine salt of 400 Yes Do. Ammonium salt ofTDT 220 No Do. 7 Diethylamino ethanol salt 330 Yes D0.

of TDT. 8 Ntg1 lbuty1amine salt of 230 Yes D0. Dimeylthaminopropyl- 330 Yes Do.

amine salts of TDT.

300 Yes Do.

10. N-propylaminoethanol salt of TDT.

1 TDT designates the dimerized linoleic acid triester of triethanolamine. 3 Ammonia detected in vapors.

EXAMPLE 3 An erosion-corrosion inhibitor is prepared by dissolving equal molar quantities of 4-morpholine ethanol and suberic acid in an equal volume of kerosene extract (aromatic extract boiling in the range of 400-600" F.), and the solution charged to a jacketed kettle and heated under nitrogen blanket to a temperature of 320 F. for six hours, with stirring, by hot oil circulated through the jacket. Completion of the reaction is indicated by an approximate theoretical reduction in the acid value of the reaction mixture. The kerosene is then removed by vacuum distillation and an equal molar quantity of N- butylamine ethanol in aqueous solution added to the residue to produce a tertiary amine having the following formula:

CH -CH A portion of the reaction product is heated in a reaction vessel to a temperature of 500 F. at atmospheric pressure. The vapor emitted from the reaction vessel is analyzed and found to contain an amine. After heating for one hour, a resinous residue is observed in the bottom of the reaction vessel.

The remainder of the reaction product is dispersed in 5 parts by Weight of ethanol and added to a flowing stream of gas containing abrasive solid particles, the additive being added to the gas in an amount equivalent to 0.01 gallon per 1,000 standard cubic feet of gas.

EXAMPLE 4 The method of Example 3 is repeated except that the initial reactants are equal molar quantities of Z-diethylamino ethanol and 8-carboxy octaneamide. The compound resulting from reaction with N-butylamine ethanol is a tertiary amine having the following formula:

CHZCHZ HO C H (C H )NH-HOO C (CHz)oC ONHCH CH N CHgCH;

The method of Example 3 is repeated except that the initial reactants are equal molar quantities of 2-heptyl- 2-phenylamino ethanol and S-carboxy-N-meth'yl octylamine. The compound resulting from reaction with pyridine is a tertiary amine having the following formula:

This reaction product releases a vaporous amine and forms a resinous residue upon heating to a temperature of 500 F. at atmospheric pressure.

A portion of the reaction product is dispersed in isopropyl alcohol and added to a flowing stream of gas containing abrasive solid particles, the agent being added to the gas in the proportion of 1 gallon per 1,000 standard cubic feet of gas.

While particular embodiments of the invention have been described, it will be understood that the invention is not limited thereto since many modifications can be made and it is intended to include within the invention any such embodiments as Well within the scope of the claims.

The invention having been thus described, we claim:

1. A method for reducing erosion and corrosion of a metal surface contacted at an elevated temperature above about 300 F. by a flowing stream of gas containing dispersed particles of solid material, which comprises introducing into said gas an organic agent that releases ammonia or a vaporous amine and forms a resinous residue at the elevated temperature and pressure of said gas.

2. The method defined in claim 1 wherein said organic agent is admixed with an inert carrier liquid.

3. The method defined in claim 2 wherein said admixture contains between 0.001 and 25 weight percent of said organic agent.

4. The method defined in claim 1 wherein said organic agent is a tertiary amine having a molecular weight above about 260.

5. The method defined in claim 4 wherein said organic agent is a tertiary amine having the generalized formula:

R is a univalent organic radical selected from Column 1 of Table 1;

R is a univalent organic radical selected from Column 2 of Table 1;

R is a bivalent organic radical selected from Column 3 of Table 1;

n is 1, 2 or 3;

m is 0, 1 or 2;

p is or 1; and

the sum of n+m+2p equals 3.

6. A method for reducing erosion and corrosion of metal surfaces contacted by a high velocity stream of gas having a temperature in excess of 400 F. and containing dispersed particles of a solid abrasive material, which comprises introducing into said gas between about 0.001 and 1 gallon of liquid additive per 1,000 standard cubic feet of gas, said additive comprising an inert polar carrier liquid and about 0.001 to 25 weight percent of a polyamine salt of an acidic triester of a C to C trialkanol amine, said salt decomposing to ammonia or a vaporous amine and a resinous residue at the temperature and pressure of said gas.

7. The method defined in claim 6 wherein said polar carrier liquid is selected from the group consisting of water and aliphatic alcohols, amines, carboxylic acids and aldehydes containing between about 1 and 10 carbon atoms.

8. The method defined in claim 6 wherein said additive is introduced into said gas as an aerosol.

9. The method defined in claim 6 wherein said inert polar carrier liquid is water and wherein said polyamine salt is a triethylene triamine salt of dimerizcd linoleic triester of triethanolamine.

10. The method defined in claim 6 wherein said polyamine salt has the formula:

CR4O O ORaCOOH.A.

N-C R40 0 CRaCO OI'LA CRiOO CRzCO'OHA wherein R is a bivalent hydrocarbyl radical containing between about 8 and 44 carbon atoms, R; is an alkylene having from 1 to 4 carbon atoms, and A is a water-soluble amine or ammonia.

11. The method defined in claim 10 wherein R is ethylene.

12. The method defined in claim 11 wherein said watersoluble amine is selected from the group consisting of morpholine, pyrrolidine, pyridine and amines having the formula:

wherein R R and R are the same or different substituents selected from the group consisting of hydrogen, alkyl radicals containing between about 1 and 4 carbon atoms, aminoalkyl radicals containing between about 2 and 4 carbon atoms, or hydroxyalkyl radicals containing between about 2 and 4 carbon atoms, and wherein no more than two of said substituents are hydrogen.

13. The method defined in claim 11 wherein said hivalent hydrocarbyl radical is the esterified hydrocarbon residue of a dimerizcd conjugated fatty acid.

References Cited