US2763612A - Natural hydrocarbon production method - Google Patents

Description

tates NATURAL HYDROCARBON PRODUCTION METHOD No Drawing. Application May 18, 1953, Serial No. 355,856

Claims. (Cl. 252-855) This invention is concerned with an improved method for the production of crude petroleum products. More particularly, it relates to an improved process for the prevention of corrosion under anaerobic conditions such as occur in wells producing hydrocarbon gases or liquids in their natural state.

Hydrocarbon producing wells are roughly divided into two main classes, namely, those producing a preponderance of gas (referred to hereinafter as gas wells or gascondensate wells) and, secondly, those wells producing a preponderance of liquid products (hereinafter referred to as oil wells). In both instances a greater or less proportion of an aqueous phase is almost always present, usually in the form of a salty brine. Dissolved in this aqueous phase and forming a part of any gaseous or liquid phase are also acidic substances such as carbon dioxide, hydrogen sulfide and organic aliphatic acids such as acetic and propionic acids.

Under the conditions of temperature and pressure existing within the well, these systems, particularly in the presence of the acidic substances, cause a substantial amount of corrosion of corrodible metal parts, such as well casing, or tubing, sucker rods and the like. It has been found that the type of corrosion which occurs is largely pitting corrosion such as is encountered in metal failure generally referred to as corrosion fatigue, as well as severe localized attack whereby failure occurs by penetration of the metal wall or by tensile failure due to weakening of the metal. This type of corrosion can and does occur Within the well in the absence of air or other oxygen-containing gas. Consequently, it will be evident that the corrosion occurring under these anaerobic conditions does not result in the formation of various oxides or rust but, on the contrary, consists in the formation of relatively insignificant amounts of solid corrosion products. Damage in the form of pits in turn, under stress of the metal part, e. g., a moving sucker rod, creates cracks, leading to failure of the metal.

Many attempts have been made to correct this situation by the addition of a wide variety of materials to the oil or gas well, by coating the metallic parts with non-metallic films; by use of expensive alloy steels, such as stainless steel; or by the use of non-metallic well parts, such as plastic piping and the like. In spite of the large amount of work performed in the past, the best that can be said is that a certain amount of reduction in the corrosion rate has been accomplished without reaching a completely satisfactory solution to the problem.

In the course of this work, commercial substances known for their inhibiting value in other systems have been investigated. It shortly became apparent, however, that the particular set of conditions existing in gas and oil wells caused most of these materials to be largely ineffective. This was particularly true of those agents formerly utilized as rust inhibitors etfective for the prevention of corrosion caused by the formation of iron oxides in substantially large amounts and in oxygen-containing atmospheres at ordinary temperatures. It was found that 2,753,612 Patented Sept. 18, 1956 most rust inhibitors were effective at or about atmospheric temperatures, but rapidly decreased in corrosion protective value with increase in temperatures, such as encountered in oil and gas wells.

It is an object of the present invention to provide an improved process for the production of hydrocarbons from their natural reserves. It is another object of the present invention to provide an improved process for the reduction in corrosion occurring in the sweet and sour wells such as gas condensate wells. It is a further object of this invention to substantially depress the corrosion fatigue ordinarily found in pumping oil wells. Other objects will become apparent from the following description of the invention.

Now, in accordance with the present invention it has been found that corrosion occurring under anaerobic conditions in hydrocarbon producing wells is substantially repressed by the addition to said wells of a polymerized (especially dimerized) fatty or hydroxy fatty acid and/ or certain derivatives thereof. Still in accordance with this invention, the useful life of metal well parts being subjected to mechanical stress is substantially prolonged by combination of said polymerized acids with an oleophilic organic phosphorus compound. Moreover, the phosphorus compounds act as an aging stabilizer for the dimer acids, particularly if stored in contact with air or under hot-or humid conditions. Again in accordance with one phase of the present invention the introduction of these compositions into the hydrocarbon well is facilitated by combining therewith a water-dispersible detergent and washing the modified composition to the bottom of the well with water. One important aspect of the invention comprises the fact that the dimer acids and their equivalents increase in the corrosion protection property at elevated well temperatures and under anaerobic conditions as compared to the decreased effect with increasing temperature experienced when air is present, such as in a pipe line or storage tank.

In general, the dimeric acids have been produced by heat polymerization of esters of the mono-carboxylic acids to esters of the dimeric acids followed by hydrolysis. The glycerides have also been heat polymerized and the product hydrolyzed to yield the free dimeric acids. Recently, Goebel in U. S. Patent No. 2,482,761 disclosed that the free fatty acids can be polymerized. Briefly, Goebels process comprises preparing unsaturated fatty acids by hydrolyzing a fat or oil for example, soya bean fatty acids, adding a small portion of water, and heating in a pressure vessel until substantially all of the diand tri-unsaturated fatty acids present polymerize. The resultant product can then be heated at reduced pressure, to distill off vaporizable constituents, which include mainly saturated acids and mono-unsaturated acids. A tem perature of at least 260 C. must be used and preferably from 330 C. to 360 C. and a heating period of 3 to 8 hours to produce substantially complete polymerization of diand tri-unsaturated material. Numerous catalysts can be employed but are not necessary. Among the catalysts which can be used are mercuric acetate, lead acetate, anthraquinone, and Rancy nickel.

Thus, for example, as described in U. S. Patent No. 2,482,761, 300 parts by weight of sardine oil having an iodine value of 188 was pressure split with 600 parts of water at 260 C. Three treatments of 1 /2, /2 and /2 hour duration were used with parts of the water employed in each treatment. Water was withdrawn and the wet acids were heated to 350 C. at a pressure of 250 pounds per square inch for 4 /2 hours. The product was then heated at reduced pressure to distill oif unpolymerized material yielding 44% by weight of a residue having an iodine value of 86.3 and a neutralization equivalent of 386.

In a similar manner, as described in the aforesaid patent linseed fatty acids, soya bean fatty acids and the fatty acids of other drying or semidrying oils can be polymerized to produce what the patentee names dimeric acids. The patentee states that by his process larger yields of dimeric acids are formed and less of the trimeric and higher polymeric acids are formed.

Another source of dimeric acids is the still residue of the dry distillation of castor oil in the presence of sodium hydroxide. An analysis of the fatty acids from castor oil has been reported in Chem. Abs. 34, 3521 as follows:

Percent 87 7 Ricinoleic acid Oleic acid Linoleic acid Saturated acids Distillation of the aforesaid still residue yields two approximately equal fractions, the distillate and a second still residue. The distillate is a mixture of undccylic, palmitic and stearic acids together with minor amounts of unsaturated monomeric fatty acids. The second still residue is a mixture of which about 50% by weight is polymerized fatty acids having a molecular Weight of 360 to about 600 and the balance a still residue having a molecular weight in excess of 600.

The material of the first still residue of the dry distillation of castor oil in the presence of sodium hydroxide has the following properties:

Lot 1 Lot 2 Neutralization N o 164 159. 9 Bromine No 26. 7 19. 4 Kinematic Viscosity at 100 F. 3, 096 1, 373 Lovibond color 750 750 A. P. I. Gravity, degrc 14. 6 l5. 2 Specific Gravity 0. 9685 0. 9646 r H a :(CHz)sC=(Z-Ofi HG C a(CH2);CH H

FORMULA I This compound after hydrolysis yields the free acid saving the structure shown in Formula II, or isomers hereof:

FORMULA II The octadecadienate esters dimerize by 1,4-diene addition to a compound having the structure shown in Formula III, or isomers of it.

FORMULA III This dimer upon hydrolysis yields the free acid having the structure given in Formula IV, or isomers of it.

FORMULA IV When one of the free octadecadienoic or octadecatrienoic acids is polymerized as described in U. S. Patent No. 2,482,761, the patentees dimeric acids have the structures shown in Formula II and IV, or isomers of them.

Castor oil contains ricinoleic acid in the form of a glyceride. The most important pyrolytic reaction of ricinoleic acid and its esters is that of dehydration to produce octadecadienoic acids. Therefore, in the dry distillation of castor oil in the presence of sodium hydroxide the higher boiling portion, i. e., the still residue is a mixture of polymerized octadecadienoic acid derived from the ricinoleic acid and the linoleic acid present in the castor oil.

From the foregoing a generic formula for the dimeric acids of the present invention can be written. Thus, as an example of an octadecadienoic acid, the polymerization of linoleic acid is illustrative. Linoleic acid or A9,10,12, 13-octadecadienoic acid is present in peanut, palm, olive, teaseecl, kapok, etc., oils in amounts of less than 25%.

" Oils such as corn, germ, cottonseed, sunfiowerseed, poppyseed, sesame, etc., contain 40% to 60% linoleic acid. The linoleic acid obtained from the great majority of plant sources is A9,10,12,13-octadecadienoic acid.

When 139,10,12,13-octadecadienoic acid is dimerized in the absence of other polyethenoid acids, either as an ester or as the free acid in the manner described in U. S. Patent No. 2,482,761, a reaction which takes place can be illustrated by the following formula:

where R is CHa(CI-I2)4 and R is {CH2)7COOH. However, for the various isomers of linoleic acid R will have a different value. Thus, artificial linoleic or octadecadienoic acids have their origin in three natural sources, (1) fatty acids more highly unsaturated than linoleic acid, which on partial hydrogenation form isomeric acids, (2) normal linoleic acid whose double bonds may be shifted by isomerization catalysts and (3) monoethenoid hydroxy acids, such as ricinoleic acid, which on dehydration form an additional double bond. For example, ricinoleic acid dehydrates to two isomeric linoleic acids, A9,l0,11,12-octadecadienoic acid and A9,10,12,13-octadecadienoic acid. When A9,10,11,12-octadecadienoic acid dimerizes in the absence of other polyethenoid acids, the resulting dimeric dicarboxylic acid has the formula:

where R is CH3(CH2)4- and R is (CH2)1COOH However, when the monocarboxylic acid is A8,9,12,13- isomer the dimeric dicarboxylic acid has the structure:

carboxylic acid has the structure where R is CH3(CH2)3 and R is -(CH2)7COOH. It follows that when the A9,l0,l2,l3-isomer is dimerized is dimerized R is when the A8,9,12,13-isomer is dimerized R is CH3(CH2)5 and R is --(CH2)6COOH; and when the A9,10,13,14-isomer is dimerized R is CH3 (CH2)4- and R is (CH2)1COOH. For these 4 isomeric linoleic acids the generic structure for the dimeric acid can be written where R is CH3(CH2) 4 for the A9,10,12,13-isomer and the A9,10,1l,12-isomer, and CHs(CH2)sfor the A8,9,- 12,13- and A9,10,l3,14-isorner, R is -(CHz)-zCOOH for the A9,10,11,12- and A9,10,13,14-isomers and (CH2)6COOH for the A8,9,12,13-isomer, it becomes obvious that in the generic formula for the dimeric acids derived from the individual diethenoid monocarboxylic acids R will have a significance of CH3(CH2)1L where n is one more than the number of CI-Izgroups between the terminal CH3 group and the nearer carbon of the nearer double bond and R will have the significance (CH2)mCOOH in which m is the number of CH2- groups between the carboxylic groups of the monocarboxylic acid and the nearer carbon of the nearer double bond. From this it follows that the generic formula for dimeric acids derived from a single di-ethenoid monocarboxylic aliphatic acids is where R is CH3(CH2)1L and R' is (CH2)mCOOH and n and m have the values given hereinbefore.

When polyethenoid acids, i. e., triand greater ethenoid acids such as n-linolenic acids are dimerized, the dimeric acids obtained are bicyclic dicarboxylic acids having the formula with a shift of the double bonds at 15 and16 the formula of the dimeric acid becomes:

H (OHzhC O OH n-oioa go-(omnooon When A9,l0,l1,12,13,14-octadecatrienoic acid is the sole acid polymerized to form the dimeric dicarboxylic acid the condensation can be pictured as occurring as follows:

which with the shift of the double bond at 11a and ll becomes H (CHQTCOOII CHaCHzCHzCHz-ll 120-11 The generic formula for the dimeric dicarboxylic acids derived from the dimerization of individual triethenoid octadecatrienoic acids is where R is CH3(CH2)3 and R is (CH2)'7COOH A well known source of these dimeric acids is the product sold by Emery Industries, Inc., and said to be dilinoleic acid. In the literature published by the Emery Industries, Inc. the properties of this product are given as follows:

Neutral equivalent 290-310.

Iodine value 80-95.

Color Gardner 12 (max). Dimer content Approx. 85%. Trimer and higher Approx. 12%. Monomer Approx. 3%.

Tests of several batches of material supplied by this producer indicate that the properties of this product are Within the limits set forth hereinafter:

Specific gravity, A. P. I l5--l5.l Specific gravity, D60/60 0.9665 Dolor, Lovibond Kinematic viscosity at 100 F., centistokes 2462-2666 a. S. T. M. bromine No 2.. 39.3 leutrality No 186.8 l90.4 dine value 67-86 It will be noted that the dimeric acids available from the Emery Industries, Inc., contain approximately 85% dimeric acids and about 12% trimeric and higher polymeric acids and the second still residue of the dry distillation of castor oil in the presence of sodium hydroxide contains about -50% of the dimeric acids and about of the trimeric and higher polymeric acids. Since neither of these industrially available products is 100% dimeric acids it is manifest that materials containing more highly polymerized acids than the dimeric acids can be used. However, it is to be noted that these ma terials contain only small amounts, say less than 10% of the monocarboxylic or unpolymerized fatty acids and saturated acids.

Accordingly, preferred materials are those containing not more than about 15% of unpolymerized unsaturated fatty acids and saturated fatty acids. In general, the content of dimeric acids and trimeric and higher acids should be of the order of at least about 85% with the dimeric acids representing at least about 50% of the dimeric and higher polymeric acids. Thus, the Emery Industries dimeric acids contain about 85% dimeric acids while the second still residue of the dry distillation of castor oil in the presence of sodium hydroxide contains about 46.8% dimeric acids. Those skilled in the art will recognize that the lower the concentration of dimeric and higher polymeric acids the greater the amount of the mixture required to provide the protection against the formation of corrosion.

While it is preferred to employ the dimerized acids described above, it is possible to utilize certain derivatives thereof, particularly the amine salts, amides or esters. 'Ihe amine salts are particularly useful in oil or gas wells containing hydrogen sulfide, e. g., sour gas wells. It has been found that the amine salts are more satisfactory for corrosion inhibition under such conditions than are the free acids.

Wells containing hydrogen sulfide (normally referred to as sour wells) are usually particularly dimcult to inhibit with respect to pitting corrosion and metal fatigue. It has been found that the subject classes of dimerized acids, particularly when they are in the form of their amine salts, substantially completely inhibit the corrosion which occurs in such systems. The amines may be primary, secondary or tertiary amines, preferably alkyl or hydroxy alkylamines. Suitable lower molecular weight alkanolamines include monoethanolamine, diethanolamine, diaminoisopropanol, dipropanolaminc, triisopropanolamine, and butanolamines. These may be added in the form of their salts with the dimerized acids or the amines and acids may be added separately, the salt formation then taking place in situ. When more hydrophobic salts are desired, the higher aliphatic amines having aliphatic radicals of 12-24 carbon atoms each may be employed in the form of dimer acid salts, including such amines as dodecyl amine, tetradccyl amine and octadecyl amine, as well as their mixtures with analogues such as derived from natural sources.

In utilizing the subject dimerized acids in gas condensate wells, it is preferred that a sutlicient amount be employed, so that the concentration is at least about 0.005% by weight based on the hydrocarbon phase. When utilized in oil wells, it is preferred than an amount effective to reduce corrosion fatigue, in the order of at least about 0.005% by weight, based on a hydrocarbon is present, although an amount of at least 0.01% is preferred. Amounts above about 0.10% fail to produce any additional corrosion protection beyond that obtained with the smaller amount noted above.

In accordance with a preferred variation of this invention, the dimerized fatty acids are combined with a phosphorus-containing hydrophobic organic wear reducing compound. This material is preferably present in an amount suflicient to provide between about 0.1% and about 1% of phosphorus, based on the weight of the dimerized acids. The phosphorus additives which have been found to be most effective comprise especially the following classes:

(1) Reaction products of phosphorus sulfides with unsaturated organic compounds, particularly with non-benzenoid unsaturated alicyclic hydrocarbons such as terpenes. One suitable material satisfactory for this purpose and belonging to the subject class bears the trade name Santolene 394-C. This is a reaction product of a phosphorus sulfide with a terpene, apparently pinene. These reaction products may be obtained by reaction of a phosphorus sulfide at temperatures above about 100 C. with a bicyclic terpene. Phosphorus sulfides which may be utilized in this and other reactions noted below are: P386, P486, P285, P487, P4510, etc. Suitable terpenes in addition to pinene include camphene and fenchene. Naturally occurring materials such as turpentine or pine oil may be employed. It is preferred that a ratio of about 1 mole of a phosphorus sulfide to between 3 and 5 moles of bicyclic terpene be employed, although the most suitable ratio is 1 mol of P285 to about 4 moles of terpene.

A second preferred class of phosphorus anti-wear agents comprises the reaction products of phosphorus sulfide or phosphorus oxides and sulfur with cylic ketones. These substances are described in U. S. Patents 2,482,762 and U. S. 2,502,408. The cyclic ketones which may be employed may be saturated or unsaturated and containing at least 12 and preferably at least 18 carbon atoms per molecule. Typical cyclic ketones comprise the isophorone bottoms obtained in the condensation of acetone.

A further class of phosphorus compounds comprises organic polyphosphates, preferably the alkyl or aryl derivatives of tripolyphosphoric acid or the analogous tetraphosphoric acid. The cations may be alkali metals, alkaline earth metals and amphoteric metals, such as sodium, calcium, barium, aluminum, or chromium. Suitable phosphates include potassium pentamethyl diphosphate, lithium pentaethyl triphosphate, calcium pentabutyl triphosphate, pentaisoamyl sodium triphosphate, sodium hexamethyl tetraphosphate and the like. Further species of substances useful for the process comprise the alkaline earth or amphoteric metal di-triphosphates such as described in U. S. Patent 2,358,305: reaction products of phosphorus sulfides with mixtures of non-benzoid cyclic alcohols and fatty alcohols, as well as the reaction products of phosphorus sulfides with high molecular weight ester waxes.

In addition to the above-identified classes of phosphorus-containing compounds, other materials may be employed such as the esters of phosphorus acids including triaryl phosphates, such as tricresyl phosphate, trialkyl phosphates, including trioctyl phosphate, and analogous aralkyl and alkaryl phosphates, thiophosphates, phosphites and thiophosphites.

The subject protective agents have been found to be effective under a wide variety of operating conditions. This is evident from the fact that they are highly efiective both in gas-condensate wells as well as in ordinary oil wells. Moreover, they are effective not only for the protection of stationary well parts from pitting and similar types of anaerobic corrosion, but as stated hereinbefore, they are additionally effective for the prevention of wear in moving well parts such as sucker rods and the like.

The conditions which exist in gas-condensate wells will vary over well-known broad areas. The liquefied hydrocarbon phase in gas-condensate wells normally comprises mixtures of methane, ethane, propane, butane, and higher hydrocarbon condensates up to and including light gasolines having up to about 8 carbon atoms. Normally gaseous hydrocarbons are partly liquefied in the well because of the pressures ordinarily existing therein. A

typical gas-condensate well produces between 20 and 30 barrels of a liquefied hydrocarbon phase per million cubic feet of gas (mmcf.), at a typical well head temperature and pressure. The temperatures at the bottom of the well usually range from about C. to about C., average temperatures at the well head being usually in the range of from about 45 C. to about 80 C. Pressures in a condensate well usually range from about 1000 to about 7000 lbs. per sq. inch absolute. A typical well may have a bottom hole pressure of about 2700 p. s. i. a. and a flowing tubing pressure of about 2000 p. s. i. a. The pressure increases the ratio of gaseous carbon dioxide (present in condensate wells) which will dissolve in the aqueous phase also present therein. At well head conditions there is usually a range of from about 7 to about 20 gallons or higher of liquid water per million cubic feet of gas produced. This liquid phase contains carbon dioxide, thus providing the aqueous carbonic acid phase. The latter usually has a pH value ranging from about 3.3 to a pH of 5.5. This aqueous phase may also contain sodium chloride and other electrolytes, the usual amounts of which are well-known to the art. Aqueous carbonic acid phase mixed with agitated liquefied hydrocarbon phase and gases is usually distributed throughout the flowing system of the well.

The conditions present in oil wells are well-known in the art. Ordinarily, the temperatures will be between about 60 F. and about 250 F. and pressures between atmospheric and about 5000 pounds per square inch are encountered. They will vary according to the age of the well in addition to the variations caused by the geologic formation from which the petroleum products are being obtained. The proportion of brine or aqueous phase will vary largely with the age of the well, but is always present to a greater or lesser degree, depending upon the particular well. The requirement for pumping will depend upon the pressures present in the well, which may be varied by water-flooding or gas repressuring techniques as known in the art.

In injecting the inhibitors into gas or oil wells, they may be packaged in the form of a cartridge, the casing of which (e. g. gelatin) is selected to melt at temperatures existing in the well. Amounts of detergents up to about 2.5% based on the dimer acids may be added to the latter when they are not packaged and if they are to be washed down the well with water, since the unmodified acids are oleophilic and are not easily moved in a water stream in the absence of the detergent. The latter may be a carboxylic acid soap, e. g. sodium stearate, or alkali metal sulfate or sulfonate, or a nonionic detergent such as polyalkylene oxide or glycol condensation products with polyhydroxy compounds such as sorbitan. The preferred method of treating a well comprises a special soaking procedure, wherein production is halted for a period of /2-3 days, during which the well is filled with oil containing Water (or brine) and dimer acids For an obscure reason, the presence of 1%100% water, based on the oil, during this soaking treatment causes an increase of 50100% in the effectiveness of the dimer acids.

In a laboratory test, similating conditions encountered in sweet gas-condensate wells, the following comparative data were obtained. These tests were carried out in fourounce oil sample bottles, containing a /8 x 5 inch sandblasted specimen of cold-rolled carbon steel. The bottles contained 50 ml. kerosene, 10 ml. distilled water which contained 3% sodium chloride, 0.1% calcium chloride, 0.03% magnesium chloride, and 0.1% acetic acid. The bottles were rotated end over end at 60 R. P. M. for 24 hours at 180 F. The specimens were then cleaned by immersing with gentle agitation for 1 minute in concentrated hydrochloric acid containing 5% SnClz and 2% SbzOa. The specimen was then neutralized immediately in sodium bicarbonate solution, rinsed with water and dried. Controlled cleaning loss was 3 milligrams and the corrosion rate was calculated from net weight loss. In the tabulation which follows the inhibitor concentration was based on the hydrocarbon phase. The inhibitor employed comprised a mixture of dimerized fatty acids ob- 1.1 tained by known dimerizing procedures with vegetable oil acids.

Corrosion Rate l\[l1s Percent by weight of Additive per Year When using proportions of additives in the order of 0.001% the following substances were found to have substantially the same corrosion protection property as experienced with the above dimer acids: dimers of castor oil acids; a mixture of amine salts and amides of dimerized linoleic acid and dialkanol amine; and dimerized soy bean oil.

The additives may be injected into the well either continuously or intermittently. In many cases it is advantageous to be able to make this injection at stated intervals. Consequently, the persistence of corrosion inhibition is an important factor when judging the efiicacy of an inhibitor. It was found that the subject dimerized fatty acids effectively inhibited corrosion over periods up to at least 2 days after they had been washed out of the system.

This was determined by subjecting specimens to the action of the inhibtors under the conditions described above, then draining the specimens and replacing them in bottles containing uninhibited kerosene and brine. When the original concentration of dimerized acids was between about 0.01% and about 0.05% the rate of corrosion did not increase even after two days of treatment in the uninhibited kerosene and brine.

in determining the effect of the present additives upon the life of moving well parts, tests in the Krause constant deflection fatigue machine were conducted. The machine was adapted for /s" by 4- /2 long specimens of sucker rod alloy. The test section was encased in a neoprene cell through which the oil and brine mixture (800 ml. total volume) was circulated at 300 ml. per minute. The tests were conducted at 150 F., the specimens being stressed to a maximum of 50,000 p. s. i. outer fiber stress at 825 cycles per minute. Crude oil and brine were used in 20/80 ratio quantities. Under these conditions the sucker rod failed after one million one hundred thousand cycles. However, when the oil and brine were modified by the presence of 0.01% dimerized acids containing a phosphorus anti-wear agent, the sucker rod lasted for five million three hundred fifty thousand cycles before failure. The phosphorus additive employed in these tests was the reaction product obtained by treatment of pinene oil with P235 at about 100 C., known as Santolene 394C. It was present in an amount sufiicient to provide the modified dimerized acid with a phosphorus content of about 0.4% by weight. The combination of dimer acids and phosphorus compound was a commercial product bearing the trade-name Santolene C.

Analysis of the dimer acid product employed in these tests indicated that it was a mixture of dimers together with a small amount of monomeric acids and a substantial proportion of trimers and higher polymers. The average molecular weight of the entire mixture was about 600.

We claim as our invention:

1. The method of treating a liquid hydrocarbon-containing system in its natural state in a pumping well for the purpose of inhibiting corrosion and reducing wear of well parts under anaerobic condition, said system comprlsing a liquefied normally liquid hydrocarbon phase and a minor amount of an aqueous acid, said system in a state of mechanically actuated flow at a temperature between about 60 F. and about 250 F. and at pressures between about atmospheric pressure and about 5,000 pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system from about 0.005% to about 0.1% of dimerized higher fatty acids, said acids having at least two olefinic linkages per molecule based on the hydrocarbon phase and an oleophilic organic phosphorus compound in an amount sufficient to provide between about 0.1% and about 1% phosphorus based on the weight of the dimerized acids.

2. A process according to claim 1 wherein the dimerized fatty acids are modified by the presence of an oleophilic organic heat reaction product of phosphorus pentasulfide and pine oil.

3. A process according to claim 1 wherein the dimer acids are modified by the presence of a reaction product obtained by heating a phosphorus sulfide with a bicyclic terpene.

4. The method of treating a liquid hydrocarbon-containing system in its natural state in a pumping well for the purpose of inhibiting corrosion and reducing wear of well parts under anaerobic conditions, said system comprising liquefied normally gaseous hydrocarbon phase and a minor amount of an aqueous acid, said system in a state of mechanically actuated flow at a temperature between about 60 F. and about 250 F. and at pressures between about atmospheric pressure and about 5,000 pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system from about 0.005% to about 0.1% of dimerized fatty acids, said acids having at least two olefinic linkages per molecule, based on the hydrocarbon phase and an oleophilic organic phosphorus compound in an amount sufiicient to provide between about 0.1% and about 1% phosphorus based on the weight of the dimerized acids.

5. The method of treating a liquid hydrocarbon-containing system in its natural state in a pumping well for the purpose of inhibiting corrosion and reducing wear of well parts under anaerobic conditions, said system comprising liquefied hydrocarhon phase and a minor amount of an aqueous acid, said system in a state of mechanically actuated fiow at a temperature between about 60 F. and about 250 F. and at pressures between about atmospheric pressure and about 5,000 pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system from about 0.005% to about 0.1% of dimerized fatty acids, said acids having at least two olefinic linkages per molecule, based on the hydrocarbon phase and an olephilic organic phosphorus compound in an amount sulficient to provide between about 0.1% and about 1% phosphorus based on the weight of the dimerized acids.

References Cited in the file of this patent UNITED STATES PATENTS 2,324,577 Haffner July 20, 1943 2,614,983 Caldwell et a1 Oct. 21, 1952 2,632,695 Landis Mar. 24, 1953

Claims (1)

1. THE METHOD OF TREATING A LIQUID HYDROCARBON-CONTAINING SYSTEM IN ITS NATURAL STATE IN A PUMPING WELL FOR THE PURPOSE OF INHIBITING CORROSION AND REDUCING WEAR OF WELL PARTS UNDER ANAEROBIC CONDITION, SAID SYSTEM COMPRISING A LIQUEFIED NORMALLY HYDROCARBON PHASE AND A MINOR AMOUNT OF AN AQUEOUS ACID, SAID SYSTEM IN A STATE OF MECHANICALLY ACTUATED FLOW AT A TEMPERATURE BETWEEN ABOUT 60* F. AND ABOUT 250* F. AND AT PRESSURES BETWEEN ABOUT ATMOSPHERIC PRESSURE AND ABOUT 5,000 POUNDS PER SQUARE INCH ABSOLUTE, COMES IN CONTACT WITH CORRODIBLE WELL PARTS, WHICH METHOD INCLUDES TH E STEP OF MIXING WITH SAID SYSTEM FROM ABOUT 0.005% TO ABOUT 0.1% OF DIMERIZED HIGHER FATTY ACIDS, SAID ACIDS HAVING AT LEAST TWO OLEFINIC LINKAGES PER MOLECULE BASED ON THE HYDROCARBON PHASE AND AN OLEOPHILIC ORGANIC PHOSPHORUS COMPOUND IN AN AMOUNT SUFFICIENT TO PROVIDE BETWEEN ABOUT 0.1% AND ABOUT 1% PHOSPHOROUS BASED ON THE WEIGHT OF THE DIMERIZED ACIDS.