NO341782B1 - Composition for inhibiting metal corrosion in a liquid aqueous medium - Google Patents

Abstract

New compositions for inhibiting corrosion in pipes, pumps and other metallic materials which may come into contact with strong acid solutions used in stimulating oil wells and the like are described. Said compositions contain (a) cinnamaldehyde and/or substituted cinnamaldehyde, and (b) urea.

Description

COMPOSITION FOR INHIBITING METAL CORROSION IN A LIQUID AQUEOUS MEDIUM.

The subject area of the invention

The present invention belongs to the field of corrosion inhibitors and methods for inhibiting corrosion in pipes, pumps and other metallic materials which may be in contact with highly acidic solutions used in the stimulation of oil wells and the like.

Known technique

Hydrocarbons (petroleum, natural gas, etc.) are obtained from an underground geological formation (in other words, a deposit, deposit) by drilling a well that penetrates the geological formation containing said hydrocarbons. A deposit is an underground rock formation (rocky body) that is sufficiently porous and permeable to store and transfer fluids.

Extraction of hydrocarbons varies due to factors related to the heterogeneity of the deposit (type of rock forming it), type of fluid produced, drainage mechanisms, etc.

Hydrocarbon producers normally perform stimulation techniques with acid to increase the overall permeability of the formation, creating conductive pathways from the formation to the well and passing through the area surrounding the well that has been damaged during drilling and establishment.

The stimulation techniques include:

(1) injecting chemical products into the well to react with and dissolve the area surrounding the well which has been damaged;

(2) injecting chemical products through the well into the geological formation to react with and dissolve small portions of rock to create small conductive channels (conductive wormholes) through which hydrocarbons will flow (so that rather than eliminating damaged areas , the hydrocarbon is redirected through said areas);

(3) injecting chemical products through the well and creating pressure sufficient to actually fracture the rock, thus creating a large flow channel that allows the hydrocarbon to migrate rapidly from the rock to the well.

Acids or acid-based fluids are normally used for this purpose because of their ability to dissolve minerals and contaminants introduced into the well during drilling or extraction operations. The most common agents used in well stimulation with acids are mineral acids such as hydrochloric acid (HCl) and/or hydrofluoric acid (HF), generally in the form of 15% by weight acid solutions.

A problem accompanying stimulation with acids is corrosion of pumping equipment and of the pipes in the well caused by contact with the acid, although petroleum and natural gas or the water contained therein also contain corrosive components, for example, CO2 or H2S and salts, leading to severe corrosion of the metallic surfaces. Furthermore, working fluids used in this field, for example the mud for sweeping the drilling chips, will contribute to corrosion.

Therefore, so-called corrosion inhibitors are used for protection against corrosion, and are added to the liquids that come into contact with metallic surfaces.

Corrosion inhibitors either form a film on the metallic surface or reduce the corrosion process by means of physical and chemical reactions on metallic surfaces.

Additives for highly acidic solutions which, on the one hand, are not only effective as corrosion inhibitors but which also do not increase the environmental risks of the process, have been sought after for a long time.

Countless compositions containing amines, quaternary ammonium compounds, acetylene alcohols and/or ethoxylated phenol-type surfactants are described in the prior art. Said compounds are considered to be dangerous for the environment.

On the other hand, patent US-A-3589860 describes the use of cinnamaldehyde or derivatives thereof as a corrosion inhibitor for equipment used in chemical processes and for petroleum extraction equipment in contact with acidic media.

US 3,005,778 A describes compositions for removing deposits from internal combustion engines and for fuel addition. The composition may contain, among other things, cinnamaldehyde (cinnamic acid aldehyde) and benzaldehyde.

US 5,854,180 A describes a corrosion inhibitor composition for use in oil wells, which contains cinnamaldehyde or a substituted cinnamaldehyde together with the reaction product of a C3-6 ketone, formaldehyde and hydrochloric acid.

Patent US-A-4734259 describes a composition and a method for inhibiting corrosive aqueous fluid attack on metals by means of a composition including an α,β-unsaturated aldehyde and a surfactant. Cinnamaldehyde and derivatives thereof are included among the preferred α,β-unsaturated aldehydes. Alkylaryl sulfonates, quaternary ammonium compounds, and alkyl and alkylaryl polyether alcohols are among the preferred surfactants.

Patent US-A-5120471 describes a composition for inhibiting steel corrosion containing more than 9% chromium in the presence of at least one mineral acid, said composition comprising: a) an organic inhibitor selected from the group consisting of phenylacetone, phenylacetone with a quaternary ammonium salt of a heterocyclic aromatic compound, and cinnamaldehyde with a quaternary ammonium salt of a heterobicyclic aromatic compound; and b) an acid-soluble compound of the antimony or bismuth type.

Patent US-A-5854180 describes a composition for inhibiting corrosion caused by hydrochloric acid solutions used for acid treatment of petroleum wells, in which said composition comprises a) 10-30% by weight cinnamaldehyde or substituted cinnamaldehyde; b) 20 – 50% by weight ethylene glycol; c) 5-20% by weight C8-C12 ethoxylated alcohols; d) 1-15% by weight of composition containing 10-40% by weight isopropanol and of a reaction product of a ketone with 3-9 carbon atoms, urea, thiourea or alkyl-substituted thiourea, benzaldehyde or formaldehyde and hydrochloric acid.

Finally, patents US-A-6068056 and US-B-6399547 describe compositions used for stimulation of petroleum wells comprising: an acid, such as hydrochloric acid, water, an aliphatic aldehyde with 1-10 carbon atoms and an aromatic aldehyde with 7-20 carbon atoms. Preferred aliphatic aldehydes are glyoxal acid and glyoxal. A preferred aromatic aldehyde is cinnamaldehyde.

Although some compositions from the known technique have reached a certain degree of effectiveness against corrosion, from an environmental point of view in some cases it can be questioned. On the other hand, given that cinnamaldehyde and/or substituted cinnamaldehyde is quite expensive, it is necessary to develop corrosion inhibitors for acids that provide an effective technical performance that overcomes the environmental and economic disadvantages indicated.

Purpose of the invention

Combination of cinnamaldehyde and/or substituted cinnamaldehyde with urea surprisingly provides a corrosion-inhibiting composition which reduces the attack of several aqueous fluids, such as aqueous acids, on ferrous metals, such as iron and steel, as well as on non-ferrous metals, such as such as aluminium, zinc and copper.

The inventors have observed a synergistic effect when the components of the composition from the invention are combined, providing corrosion inhibition thereof in the order of magnitude or higher than that from compositions containing only cinnamaldehyde and/or substituted cinnamaldehyde and much higher than compositions containing only urea.

It is therefore an aim of the present invention to provide a composition for inhibiting corrosion of metals in a liquid aqueous medium which comprises:

(a) cinnamaldehyde and/or substituted cinnamaldehyde, and

(b) urea.

Furthermore, part of the purpose of the invention constitutes an acid-type aqueous solution which includes:

(a) an acid selected from hydrochloric acid (HCl), hydrofluoric acid (HF), formic acid (HCOOH), acetic acid (CH3CH2CHOOH), sulfuric acid (H2SO4), and mixtures thereof

(b) an effective amount of composition according to the present invention for inhibiting corrosion caused by said acid.

A method for stimulating an underground rock formation consisting of placing an acid-type aqueous solution from the invention in contact with an underground rock formation forms part of the purpose of the invention.

Further advantageous embodiments of the present invention are indicated in the independent patent claims.

Description of the invention

Cinnamaldehyde or substituted cinnamaldehyde

Cinnamaldehyde or 3-phenyl-2-propen-1-al is obtained naturally from cinnamon oil.

A conjugated double bond (C6H5CH=CHCHO) ensures that the geometry of the compound is in a plane, and therefore a mixture of isomers (cis and trans) can be found.

According to the present invention, cinnamaldehyde can be substituted or unsubstituted. Examples of cinnamaldehydes that can be used in the present invention are: dicinnamaldehyde; p-hydroxycinnamaldehyde; pmethylcinnamaldehyde; p-ethylcinnamaldehyde; p-methoxycinnamaldehyde; pdimethylaminocinnamaldehyde; p-diethylaminocinnamaldehyde; pnitrocinnamaldehyde; o-nitrocinnamaldehyde; 4-(3-propenal)cinnamaldehyde; sodium p-sulfocinnamaldehyde; p-trimethylammonium cinnamaldehyde sulfate; ptrimethylammonium cinnamaldehyde o-methylsulfate; p-thiocyanocinnamaldehyde; p-(S-acetyl)thiocinnamaldehyde; p-(S-N,N-dimethylcarbamoylthio)cinnamaldehyde; pchlorocinnamaldehyde; α-methylcinnamaldehyde; β-methylcinnamaldehyde; αchlorocinnamaldehyde; α-bromocinnamaldehyde; α-butylcinnamaldehyde; αamylcinnamaldehyde; α-hexylcinnamaldehyde; α-bromo-p-cyanocinnamaldehyde; α-ethyl-p-methylcinnamaldehyde and p-methyl-α-pentylcinnamaldehyde.

Cinnamaldehyde is preferred according to the present invention. It is preferred that cinnamaldehyde should be predominantly trans-cinnamaldehyde. In this context, "mainly" means that if cinnamaldehyde contains a mixture of isomers, trans-cinnamaldehyde is present in a proportion greater than 50% by weight of said mixture.

Urea

Urea or carbonyl diamide is a colorless crystalline chemical compound, with the formula CO(NH2)2. It is found abundantly in the urine of humans and mammals.

Urea is also present in molds as well as in the leaves and seeds of a number of vegetables and cereals. It is soluble in water and in alcohol and slightly soluble in ether.

According to the present invention, it is preferred that the weight ratio between cinnamaldehyde and/or substituted cinnamaldehyde (a) and urea (b) is between 50:1 and 1:6, preferably between 35:1 and 1:4, more preferably between 15: 1 and 1:3, and most preferably between 8:1 and 1:2.

A surfactant (c) can further be incorporated into the composition for inhibiting metal corrosion from the present invention.

Cationic, non-ionic and amphoteric surfactants can be used together with cinnamaldehyde and/or substituted cinnamaldehyde (a) and urea (b) in the compositions for inhibiting metal corrosion in the present invention. Said surfactants can be dissolved in liquids, normally water. According to the present invention, the surfactants are considered to have 100% of active substance (active ingredient).

Suitable cationic surfactants (surfactants) according to the present invention are:

- C6-C22 alkyl amines (R-NH2), di C6-C22 alkyl amines (R2-NH) or tri C6-C22 alkyl amines (R3-N) (such as fat coconut, tallow or olein monoalkyl amines and dialkyl amines) , in the form of an addition salt from neutralization with organic (vinegar, citric, olein, etc.) or inorganic (hydrochloric acid, etc.) acids.

- C6-C22 alkyl dimethyl amines (R-N(CH3)2) and di C6-C22 alkyl methyl amines (R2-NCH3) from coconut, tallow or olein fat, in the form of an addition salt from the neutralization of organics (vinegar, lemon, olein , etc.) or inorganic (hydrochloric acid, etc.) acids.

- Alkoxylated C6-C22 alkyl amines (R-NH2), di C6-C22 alkyl amines (R2-NH) or tri C6-C22 alkyl amines (R3-N), generally ethoxylated and/or propoxylated (such as coconut fat, tallow or olein monoalkyl amines and dialkyl amines with 2-30 mol ethylene and/or propylene oxide), optionally quaternized with suitable alkylating agents such as dimethyl sulfate, methyl chloride or benzyl chloride, or in the form of an addition salt from neutralization with organic (vinegar, citric, olein, etc.) or inorganic (hydrochloric acid, etc.) acids

- Alkylene polyamines, such as C6-C22 alkyl propylene diamines (R-NH-(CH2)3-NH2), C6-C22 alkyl propylene triamines (R-NH-(CH2)3-NH-(CH2)3-NH2) , C6-C22 alkyl propylene tetraamines (linear and branched), in the form of an addition salt from the neutralization of organic (acetic, citric, oleic, etc.) or inorganic (hydrochloric acid, etc.) acids

- Alkoxylated alkylene polyamines, generally ethoxylated and/or propoxylated, such as fatty coconut, tallow or olein C6-C22 alkyl propylene diamines (R-NH-(CH2)3-NH2), fatty coconut, tallow or olein C6-C22 alkyl propylene triamines (R-NH-(CH2)3-NH-(CH2)3-NH2), fat coconut, tallow or olein C6-C22 alkyl propylene tetraamines (linear and branched), with 2 to 30 moles of ethylene and/or propylene oxide , optionally quaternized with suitable alkylating agents such as dimethyl sulfate, methyl chloride or benzyl chloride, or in the form of an addition salt from neutralization with organic (vinegar, citric, olein, etc.) or inorganic (hydrochloric acid, etc.) acids

- C6-C22 alkyl ether amines

- C6-C22 alkyl imidazolines

- C6-C22 alkyl amidoamines

- Amines of rosin acids (mainly monovalent carboxylic acids containing a phenanthrene skeleton with 20 carbon atoms in the molecule) or of tall oil

- Quaternary ammonium compounds, such as C6-C22 alkyl dimethyl amines (R-N(CH3)2) and C6-C22 dialkyl methyl amines (R2-NCH3) quaternized with suitable alkylating agents such as dimethyl sulfate, methyl chloride or benzyl chloride, as well as heterobicyclic ammonium salts. Examples of quaternary ammonium compounds are C6-C22 alkyl trimethyl ammonium (R-N(+)(CH3)3) chloride or methosulfate, preferably C10-C18 alkyl trimethyl ammonium, C6-C22 dialkyl dimethyl ammonium (R2-N(+)(CH3) 2) chloride or methosulfate, preferably C10-C18 dialkyl dimethyl ammonium, C6-C22 alkyl benzyl dimethyl ammonium chloride, quaternized alkylene polyamines (such as quaternized C6-C22 alkyl propylene diamines, quaternized C6-C22 alkyl propylene triamines or quaternized C6-C22 alkyl propylene tetraamines), N-C6-C22 alkyl pyridinium bromide or chloride (such as N-octyl pyridine bromide, N-nonyl pyridine bromide, N-decyl pyridine bromide, N-dodecyl pyridine bromide, N-tetradecyl pyridine bromide, N-dodecyl pyridine chloride), N cyclohexyl pyridine bromide, naphthyl methyl quinoline chloride, C6-C22 alkyl methyl quinoline chloride, naphthyl methyl pyridine chloride or C6-C22 alkyl methyl quinoline chloride. Suitable amphoteric surfactants according to the invention are betaine-type compounds such as:

- C6-C22 alkyl dimethyl betaine (R-N(CH3)2(<+>)-CH2COO-), obtained from a C6-C22 alkyl dimethyl amine which is reacted with sodium monochloroacetate, such as C12-C14 dimethyl betaine (carboxylate methyl C12 -C14 alkyl dimethylammonium),

- C6-C22 alkyl amido betaine (R-CO-NH-CH2CH2CH2-N(CH3)2(<+>)-CH2COO-), obtained by reaction of sodium monochloroacetate with the reaction product of dimethyl amino propylamine with C6-C22 fatty acids or its methyl esters, such as C10-C18 amidopropyl dimethylamino betaine,

- C6-C22 alkyl and C6-C22 alkyl amido sulfobetaines (R-CO-NH-CH2CH2CH2-N(CH3)2(<+>)-CH2CHOH-CH2SO3-), similar products to those previously described where the carboxyl group has been substituted with a sulfone group, such as C10-C18 dimethyl sulfohydroxybetaine, C10-C18 amido propyl dimethylamino sulfohydroxybetaine,

- betaine-type imidazoline derivatives, these are products obtained by reaction of a fatty-type alkyl imidazoline with sodium monochloroacetate. In the case of adding 1 mole of sodium monochloroacetate, monocarboxylated derivatives are obtained, while if 2 moles of sodium monochloroacetate are added, dicarboxylated derivatives are obtained

- C6-C22 alkyl amino monopropionates and C6-C22 alkyl amino dipropionates

- C6-C22 alkyl amino amphoacetates and C6-C22 alkyl amino diaphmoacetates, such as sodium coco amino amphoacetate or disodium coco amino diaphmoacetate

- soybean lecithin.

Suitable non-ionic surfactants according to the invention are:

- alcohols

- alkanolamides

- amides derived from alkanolamides (coconut fatty acid monoethanolamide, coconut fatty acid diethanolamide, oleic acid diethanolamide, vegetable oil fatty acid diethanolamide)

- alkoxylated fatty amides, generally ethoxylated and/or propoxylated (such as coconut fatty acid monoethanolamide with 4 moles of ethylene oxide),

- amine oxides such as N-cocosamidopropyl dimethyl amine oxide, dimethyl C6-C22 amine oxide, such as dimethyl coco amine oxide,

- esters such as ethoxylated and/or propoxylated fatty acids (castor oil with 2 to 40 mol ethylene oxide), ethoxylated and/or propoxylated glycerides (PEG-24 glyceryl monostearate), glycol esters and derivatives, monoglycerides, polyglyceryl esters, esters and ethers of polyalcohols, sorbitan/sorbitol esters and phosphoric acid trimesters

- ethers such as ethoxylated and/or propoxylated fatty alcohols (cetyl stearyl alcohol with 2 to 40 mol ethylene oxide, lauric alcohol with 2 to 40 mol ethylene oxide, oleic alcohol with 2 to 40 mol ethylene oxide, ethoxylated lanolin derivatives, ethoxylated polysiloxanes, PEG propoxylated ethers (PPG-1-PEG-9-lauryl glycol ether), ethoxylated and/or propoxylated alkylphenols.

Surfactant (c) is preferably selected from alkylene polyamines, optionally alkylated, quaternary ammonium compounds, betaine-type amphoteric surfactants and mixtures thereof.

Preferred cationic surfactants according to the invention are C10-C18 alkyl trimethyl ammonium chloride or methosulfate, C10-C18 dialkyl dimethyl ammonium chloride or methosulfate, C6-C22 alkyl benzyl dimethyl ammonium chloride, quaternized C6-C22 alkyl propylene diamine chloride or methosulfate, N-C6 -C22 alkyl pyridinium bromide or chloride, optionally alkylated C6-C22 alkyl propylene diamines, optionally alkylated C6-C22 alkyl propylene triamines, optionally alkylated C6-C22 alkyl propylene tetraamines (linear and branched), and mixtures thereof.

Preferred amphoteric surfactants according to the invention are C12-C12 alkyl dimethyl betaine, C10-C18 alkyl amidopropyl dimethylamino betaine, C10-C18 dimethyl sulfohydroxybetaine, C10-C18 amido propyl dimethylamine sulfohydroxybetaine, sodium C10-C18 alkyl amino amphoacetate, disodium C10-C18 alkyl amine diamphoacetate and mixtures thereof.

According to the present invention, the weight ratio between cinnamaldehyde and/or substituted cinnamaldehyde (a) and surfactant (c) is between 50:1 and 1:6, preferably between 35:1 and 1:3, even more preferably between 30:1 and 1 : 2.

On the other hand, the weight ratio between urea (b) and surfactant (c) is between 30:1 and 1:20, preferably between 20:1 and 1:10.

A solvent (d) can be incorporated into the composition for inhibiting metal corrosion in the present invention for the purpose of dissolving cinnamaldehyde and/or substituted cinnamaldehyde (a), urea (b) or surfactant (c).

Said solvent (d) is selected from water, aprotic polar solvents, aromatic solvents, terpinols, alcohols with 1 to 18 carbon atoms and polyols (polyhydroxylated alcohols) with 2 to 18 carbon atoms and mixtures thereof.

The preferred solvents according to the invention are water, aprotic polar solvents such as formamide, dimethyl formamide (DMF), dimethyl acetamide (DMA) and mixtures thereof, linear or branched alcohols (monoalcohols, ether alcohols, etc.) with 1 to 18 carbon atoms, optionally alkoxylated, preferably with ethylene oxide and/or propylene oxide, and polyols (polyhydroxylated alcohols) with 2 to 18 carbon atoms, both aromatic, such as pyrocatechol (1,2-benzenediol), resorcinol (1,3-benzenediol), hydroquinone (1, 4-benzenediol), or bisphenol A (4,4'-isopropylidenediphenol) and aliphatic.

Preferably, the alcohols with 1 to 18 carbon atoms are used, alcohols and ether alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, n-pentanol, methylglycol, ethylglycol, propylglycol, butylglycol and n-pentylglycol, as well as as natural fatty alcohols such as lauric, palmitic, cetyl, stearic and oleic alcohols, etc.

Preferably, the polyols used are polyhydroxylated alcohols with a linear or branched chain containing 2 to 18 carbon atoms. Suitable polyols are:

- diols, such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylene glycol, 1,4-butanediol, 1,6-hexanediol

- triols, such as glycerol,

- tetrols, such as pentaerythritol, diglycerol

- hexols, such as mannitol, sorbitol and similar polyols.

Preferably, solvent (d) is selected from water, formamide, dimethylformamide, dimethylacetamide, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, n-pentanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butanediol, 1,6-hexanediol, methylglycol, ethylglycol, propylglycol, butylglycol, glycerol and mixtures thereof.

A composition for inhibiting metal corrosion in a fluid aqueous medium is preferred, comprises with regard to the total weight of said

composition:

(a) between 5 - 45%, preferably between 10 - 30% by weight of cinnamaldehyde and/or substituted cinnamaldehyde

(b) between 0.1 - 30%, preferably between 2 - 20% by weight urea

(c) between 0 - 25%, preferably between 1 - 20% by weight of 100% surfactant or mixtures thereof

(d) between 20-90%, preferably between 55-80% by weight of a solvent or mixtures thereof.

According to the invention, it is advantageous that the active substance thereof is comprised, with respect to the total weight thereof, of between 10% and 80% by weight, preferably between 15% and 50%, more preferably between 20% and 45%. The active substance from the composition for inhibiting metal corrosion from the invention is mainly provided by the components (a) cinnamaldehyde and/or substituted cinnamaldehyde, (b) urea, and possibly (c) surface-active agent/agents.

pH regulating agents, viscosity modifying agents, ion chelating or scavenging agents such as EDTA (ethylene diamino tetraacetic acid), DPTA (diethylene triamino pentaacetic acid), HEDTA (hydroxyethylene diamino triacetic acid), EDDHA (ethylene diamino di-ortho-hydroxy-phenyl acetic acid), EDDHMA (ethylene diamino di-ortho-hydroxy-para-methyl phenyl acetic acid), EDDCHA (ethylene diamino di-ortho-hydroxy-para-carboxy-phenyl acetic acid), stabilizers, corrosion inhibition intensifiers or enhancers, corrosion inhibitors, dispersants or mixtures thereof may be incorporated into the composition for inhibiting metal corrosion in the present invention.

Suitable corrosion-inhibiting intensifying or strengthening agents are formic acid (HCOOH), methyl formate (HCOOCH3), ethyl formate (HCOOCH2CH3), benzyl formate (HCOOCH2C6H5), formamide (CH3NO), dimethyl formamide (HCON(CH3)2), 1,1'- azobisformamide (NH2CON=NCONH2), and metal halides such as sodium fluoride (NaF) or potassium fluoride (KF), sodium chloride (NaCl) or potassium chloride (KCl), sodium bromide (NaBr) or potassium bromide (KBr), sodium iodide (NaI) or potassium iodide (KI) ), copper (I) chloride (I) (CuCl or Cu2Cl2), copper (I) iodide (CuI or Cu2I2), copper (II) chloride (CuCl2), copper (II) iodide (CuI2), antimony chloride (SbCl3) or mixtures thereof. Preferred corrosion-inhibiting intensifying or reinforcing agents according to the invention are KI, CuI or Cu2I2, or mixtures thereof.

Suitable corrosion inhibitors are propargyl alcohol (CHCCH2OH), Pent-4-in-1-ol (CHC(CH2)3OH), hexinol, ethyl octinol, octinol, 3-phenyl-2-propyn-1-ol, crotonaldehyde, furfural, p-anisaldehyde, phenyl vinyl ketone, β-hydroxypropiophenone, piperazine, hexamethylene tetramine or mixtures thereof.

The previously described acids are often in aqueous solution form at 3%, 7.5%, 15%, 28% and 37% by weight for hydrochloric acid and for mixtures of hydrochloric acid and hydrofluoric acid. According to the present invention, hydrochloric acid and the mixture of hydrochloric acid and hydrofluoric acid are preferred, said mixture preferably contains from 6% to 15% by weight of hydrochloric acid and from 1% to 6% by weight of hydrofluoric acid.

Composition for inhibition of metal corrosion from the present invention is added to the acid (or to an aqueous solution thereof) to obtain an acid-type aqueous solution, so that the composition for inhibition of metal corrosion is present between 0.01 - 10% (active substance ), preferably between 0.1 - 5% with respect to the total weight of the acid-type aqueous solution.

The composition for inhibiting metal corrosion from the present invention can be used, in the intervals specified earlier, at temperatures in the range between 20 ºC and 200 ºC.

The present invention also provides a method for stimulating an underground rock formation consisting of bringing said underground rock formation into contact with an acid-type aqueous solution according to

the invention.

Preferably, an acid-type aqueous solution according to the invention is pumped through a well.

The following examples are presented with the intention of providing a sufficiently clear and complete explanation of the present invention for a person skilled in the art, but they must not be considered as limiting the essential features of the purpose of the invention as they have been presented in the preceding paragraphs in this description.

Examples

Example 1

A test was carried out to determine the corrosion-inhibiting properties, as described below:

1.

Cold-rolled, low-carbon steel test pieces, of F111 type according to UNE (a Spanish standard) classification, with dimensions of 40 x 20 x 2 mm (height x width x thickness) are taken and the surface thereof is polished with sandpaper. They are then degreased by placing them in a container with isopropyl alcohol and they are held in an ultrasonic bath for 3 minutes. They are air-dried and weighed on a balance with an accuracy of ± 0.001 g.

2.

70 ml of concentrated 15% HCl (obtained by diluting commercial concentrated 37% HCl) is added to Pyrex glass bottles with screw-on closures. Then 1.0% (700 microlitres) of the corrosion inhibitor is added, the compositions of which are shown in Table 1.

3.

The preceding mixture is shaken manually and then becomes a degreased and weighed (according to 1) steel test piece is introduced into each glass bottle in a vertical position so that it is completely covered by the acid solution.

Once the test piece has been introduced into the glass bottle containing the acid solution, the bottle is closed by screwing on the lid and introduced into an autoclave containing water. It is held for 2 hours at a pressure of 1.2 bar and 120 ºC. It is then cooled for a further 2 hours inside the autoclave. When the bottle is removed, it is at approx. 60-70 ºC.

5.

The steel test piece is then removed with tweezers, placed in a 10% sodium bicarbonate bath to neutralize the remaining acid and then cleaned by rubbing the surface of the plate with a brush and soapy water. It is then cleaned first with limonene (dipentene) and then with isopropyl alcohol. It is air dried and then weighed with an accuracy of ± 0.001 g.

Corrosion (corrosion rate) is presented as loss of mass in grams per square meter and hour (g/m<2>.h).

The smaller the difference in mass between before and after the treatment with acid in the autoclave, the greater the inhibition strength of the evaluated composition.

Table 2 shows average values obtained for the compositions detailed in Table 1 when tests are carried out in duplicate.

Table 1

<5>Alkyl (fatty chain with 12 and 14 carbon atoms), ((carboxylate methyl) alkyldimethylammonium) betaine. Active substance: 32%

Table 2

It can be seen in Table 2 that by combining cinnamaldehyde (transcinnamaldehyde) and urea, values of protection against corrosion are obtained, which are higher than those obtained with only cinnamaldehyde or urea.

On the other hand, the addition of a surfactant (of the alkyl betaine type) to the cinnamaldehyde-urea mixture will enable increased protection against corrosion.

Example 2

A new series of experiments was carried out under the same experimental conditions as those described in Example 1. The differences are the composition of the corrosion inhibitors detailed in Table 3 and the dose of said inhibitors used, in this case, 0.75% (525 microliters) to 70 ml of the 15% hydrochloric acid solution.

Furthermore, 3% (2.1 g) KI has been used as an intensifying agent in the new series of experiments.

Table 4 shows the values obtained for the compositions detailed in Table 3 when the tests are carried out in duplicate.

Table 3

Table 4

It can be observed in Table 4 that the intensifier allows the achievement of corrosion protection values higher than those obtained in its absence.

On the other hand, sample 14 has corrosion protection values in the same order of magnitude as those obtained with only cinnamaldehyde (sample C3), which implies the achievement of equally effective and more economical formulations.

Finally, samples 11, 12 and 13 achieve a significant decrease in corrosion rate, which involves the achievement of more efficient and economical formulations.

Example 3

A new series of experiments was carried out under the same experimental conditions as those described in Example 2. The only difference is the composition of corrosion inhibitors detailed in Table 3. In these new series of corrosion inhibitor samples, cinnamaldehyde and urea from sample 13 have been proportionally replaced with other components, by maintaining the total sum of active components in the formulation. Table 6 shows the values obtained for the compositions detailed in Table 5 when the tests were carried out in duplicate.

Table 5

<1>Polypropylene polyamine from tallow ethoxylated with 3 mol of ethylene oxide. Active substance: 100%<2>Monoamine with coconut fat chain ethoxylated with 5 mol of ethylene oxide. Active substance: 100%<3>Quaternary alkyl (coconut fat chain) benzyl dimethyl ammonium chloride. Active substance: 80%<4>Mixture of fatty alcohols with 12 to 14 carbon atoms ethoxylated with 7 moles of ethylene oxide. Active substance: 100%

<5>Alkyl (fatty chain with 12 and 14 carbon atoms), ((carboxylate methyl) alkyldimethylammonium) betaine. Active substance: 32%

<6>Alkyl propylene diamine from tallow quaternized with methyl chloride. Active substance: 50% Table 6

In Table 6 it can be observed how fatty polyamine-type surfactants, quaternary ammonium compounds and betaines combined with cinnamaldehyde urea mixture are preferred.

Claims (20)

Patent requirements 1. Composition for inhibiting metal corrosion in a liquid aqueous medium, characterized in that it includes: (a) cinnamaldehyde and/or substituted cinnamaldehyde, and (b) urea. 2. Composition according to claim 1, c a r a c t e r i s e r t v e d a t the weight ratio between cinnamaldehyde and/or substituted cinnamaldehyde (a) and urea (b) is between 50 : 1 and 1 : 6. 3. Composition according to any one of claims 1 to 2, c a r a c t e r i s e r t v e d a t the weight ratio between cinnamaldehyde and/or substituted cinnamaldehyde (a) and urea (b) is between 35:1 and 1:4, preferably between 15:1 and 1:3. 4. A composition according to any one of the preceding claims, characterized by it further comprises a surfactant (c). 5. Composition according to claim 4, c a r a c t e r i s e r t v e d a t the weight ratio between cinnamaldehyde and/or substituted cinnamaldehyde (a) and the surfactant (c) is between 50:1 and 1:6, preferably between 35:1 and 1:3. 6. Composition according to claim 4, c a r a c t e r i s e r t v e d a t the weight ratio between urea (b) and the surfactant (c) is between 30:1 and 1:20, preferably between 20:1 and 1:10. 7. Composition according to any one of claims 4 to 6, c a r a c t e r i s e r t v e d a t the surface-active agent (c) is selected from alkylene polyamines, optionally alkylated, quaternary ammonium compounds, betaine-type amphoteric surface-active agents and mixtures thereof. 8. Composition according to requirement 7, c a r a c t e r i s e r t v e d a t the surfactant (c) is selected from C10-C18 alkyl trimethyl ammonium chloride or methosulfate, C10-C18 dialkyl dimethyl ammonium chloride or methosulfate, C6-C22 alkyl benzyl dimethyl ammonium chloride, quaternized C6-C22 alkyl propylene diamine chloride or methosulfate, N -C6-C22 alkyl pyridine bromide or chloride, optionally alkylated C6-C22 alkyl propylene diamines, optionally alkylated C6-C22 alkyl propylene triamines, optionally alkylated C6-C22 alkyl propylene tetraamines (linear and branched) and mixtures thereof. 9. Composition according to claim 7, c a r a c t e r i s e r t v e d a t the surfactant (c) is selected from C10-C18 alkyl dimethyl betaine, C10-C18 alkyl amidopropyl dimethylamino betaine, C10-C18 dimethyl sulfohydroxybetaine, C10-C18 amido propyl dimethylamino sulfohydroxybetaine, sodium C10-C18 alkyl amino amphoacetate, disodium C10-C18 alkyl amino diamphoacetate, and mixtures thereof. 10. Composition according to any one of the preceding claims, c a r a c t e r i s e r t v e d a t it further comprises a solvent (d). 11. Composition according to claim 10, c a r a c t e r i s e r t v e d a t solvent (d) is selected from water, aprotic polar solvents, aromatic solvents, terpinols, alcohols with 1 to 18 carbon atoms and polyols with 2 to 18 carbon atoms and mixtures thereof. 12. Composition according to any one of claims 10 to 11, c a r a c t e r i s e r t v e d a t solvent (d) is selected from water, formamide, dimethyl formamide, dimethyl acetamide, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, npentanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butanediol , 1,6-hexanediol, methylglycol, ethylglycol, propylglycol, butylglycol, glycerol and mixtures thereof. 13. Composition according to any one of claims 1 to 12, c a r a c t e r i s e r t v e d a t it includes, with regard to the total weight of the composition: (a) between 5 - 45%, preferably between 10 - 30% by weight of cinnamaldehyde and/or substituted cinnamaldehyde; (b) between 0.1 - 30%, preferably between 2 - 20% by weight urea; (c) between 0-25%, preferably between 1-20% by weight of a 100% surfactant or mixtures thereof; and (d) between 20 - 90%, preferably between 55 - 80% by weight of solvent. 14. Composition according to any one of the preceding claims, c a r a c t e r i s e r t v e d a t cinnamaldehyde and/or substituted cinnamaldehyde (a) is trans-cinnamaldehyde. 15. A composition according to any one of the preceding claims, characterized by den videre includes corrosion-inhibiting intensifying or strengthening agents, pH-regulating agents, viscosity-modifying agents, ion-chelating or absorbing agents, stabilizing agents, corrosion inhibitors, dispersing agents or mixtures thereof. 16. Oxygen-type aqueous solution, c a r a c t e r i s e r t v e d a t it includes: (a) an acid selected from hydrochloric acid (HCl), hydrofluoric acid (HF), formic acid (HCOOH), acetic acid (CH3CH2CHOOH), sulfuric acid (H2SO4), and mixtures thereof, and (b) an effective amount of a composition according to any of claims 1 to 15 for inhibition of corrosion caused by said oxygen. 17. Oxygen-type aqueous solution according to claim 16, c a r a c t e r i s e r t v e d a t said composition according to any one of claims 1 to 15 is present between 0.01 - 10%, preferably between 0.1 - 5% with respect to the total weight of the oxygen-type aqueous solution. 18. Oxygen-type aqueous solution according to any one of claims 16 to 17, characterized by The oxygen is hydrochloric acid or a mixture of hydrochloric acid and hydrofluoric acid. 19. Method for stimulating an underground rock formation, characterized by it consists of contacting said bedrock formation with an oxygen-type aqueous solution according to any one of claims 16 to 18. 20. Method according to claim 19, c a r a c t e r i s e r t v e d a t an oxygen-type aqueous solution according to any one of claims 16 to 18 is pumped through a well.