WO2013092440A1

WO2013092440A1 - Compositions comprising polyester polyamine and polyester polyquaternary ammonium corrosion inhibitors and chelating agents

Info

Publication number: WO2013092440A1
Application number: PCT/EP2012/075680
Authority: WO
Inventors: Per-Erik Hellberg; Natalija Gorochovceva; Cornelia Adriana De Wolf; Albertus Jacobus Maria Bouwman; Hisham Nasr-El-Din
Original assignee: Akzo Nobel Chemicals International B.V.
Priority date: 2011-12-19
Filing date: 2012-12-17
Publication date: 2013-06-27

Abstract

The present invention relates to a composition comprising a polyesteramine or a polyester polyquaternary ammonium compound and a chelating agent, and to various uses of such a composition, for example as corrosion inhibitor, cleaning agent or descaling agent for metal surfaces and as stimulation or treatment fluids for methods for treating subterranean formations.

Description

COMPOSITIONS COMPRISING POLYESTER POLYAMINE AND POLYESTER POLYQUATERNARY AMMONIUM CORROSION INHIBITORS AND CHELATING AGENTS

Field of Invention The present invention relates to a composition comprising a polyesteramine or a polyester polyquaternary ammonium compound and a chelating agent. The invention also relates to a kit of parts containing the composition, the use of this composition as corrosion inhibitor, cleaning agent or descaling agent for metal surfaces, to a method for cleaning or descaling a metal surface or for protecting a metal surface from corrosion by contacting the metal surface with said composition, and to a method for treatment of a subterranean formation comprising introducing a composition of the invention into the formation.

Background of the Invention

Subterranean formations from which oil and/or gas can be recovered can contain several solid materials contained in porous or fractured rock formations. The naturally occurring hydrocarbons, such as oil and/or gas, are trapped by the overlying rock formations with lower permeability. The reservoirs are found using hydrocarbon exploration methods and often one of the purposes of withdrawing the oil and/or gas there from is to improve the permeability of the formations. The rock formations can be distinguished by their major components and one category is formed by the so-called shale formations, which contain very fine particles of many different clays covered with organic materials to which gas and/or oil are adsorbed. Shale amongst others contains many clay minerals like kaolinite, illite, chlorite, smectite, and montmorillonite and as well, quartz, feldspars, carbonates, pyrite, organic matter, and cherts, another category is formed by the so-called sandstone formations, which contain siliceous materials (like quartz) as the major constituent and amounts of clays (aluminosilicates such as kaolinite or illite) or alkaline aluminosilicates such as feldspars, and zeolites, as well as carbonates (calcite, dolomite, ankerite) and iron-based minerals (hematite and pyrite), and another category is formed by the so-called carbonate formations, which contain carbonates (like calcite and dolomite) as the major constituent. Corrosion is often a serious issue in oil- and gas field processes, e.g. in transportation of crude oil, and in oil or gas wells. This could be due to dissolved gases such as carbon dioxide or hydrogen sulfide causing so-called sweet and sour corrosion, respectively, on metal surfaces. Another serious source of corrosion is the often high electrolyte concentrations in the water which is co-produced with the oil and gas. Further, severe risks of corrosion are obvious when inorganic or organic acids are used in so-called acid stimulation or fracturing operations encountered in order to increase the productivity of oil and gas wells. Also in drilling operations there often is a need to use corrosion inhibitors, e.g. in drilling fluids. Corrosion problems are also often an issue in downstream processes, such as refineries, when e.g. salts or acid components from crude oils being processed are causing corrosion of metal.

Different types of nitrogen-containing compounds, such as e.g. fatty amines, alkoxylated fatty amines, amidoamines, and quarternary ammonium compounds, are well-known bases for corrosion inhibitor formulations used in various kinds of systems. US 5 352 377 and US 5 456 731 , for example, disclose reaction products of hydrocarbyl-substituted carboxylic anhydrides, more specifically hydrocarbyl- substituted succinic anhydrides, and aminoalkanols, e.g. ethoxylated fatty alkyl monoamines or ethoxylated fatty alkyl propylenediamines, that can provide effective antiwear, antirust, and corrosion-inhibiting properties in lubricant and fuel applications. US 5 178 786 relates to corrosion-inhibiting compositions and their use in functional fluids, especially aqueous hydraulic fluids. These compositions comprise at least four components A, B, C, and D, where component D is an ester-salt formed by the reaction of an alkyl or alkenyl succinic anhydride with an alkanolamine. The preferred alkanolamines are, e.g., dimethylethanolamine, diethylethanolamine, and methylethylethanolamine, and thus the preferred products D are not polymers.

There are also a number of patent publications where oligomeric/polymeric nitrogen- containing ester-linked compounds based on dicarboxylic acids/anhydrides and ethoxylated (fatty alkyl)amines are used in other applications/systems. For example, in EP 0 572 881 a product obtained from an oxyalkylated primary fatty amine and a dicarboxylic acid is disclosed for use in a process for separation of a petroleum emulsion of the water-in-oil type. US 4 781 730 discloses reaction products of a polybasic acid and a polyhydroxyalkanolamine that are components in a fuel additive composition for reduction of valve seat recession in a vehicle. US 5 034 444 discloses a rheological additive for non-aqueous coating compositions that may be the reaction product of an alkoxylated aliphatic nitrogen-containing compound and an organic polycarboxylic anhydride or acid. EP 0 035 263 A2 discloses polyester compounds produced by reaction between a dicarboxylic acid and an alkoxylated tertiary amine and their use as textile softeners. US 5 284 495 discloses oligomers/polymers, which can be prepared by polymerising an anhydride, e.g. phthalic anhydride, and long-chain amine containing diols, e.g. ethoxylated octadecylamine. These products are used as additives that improve the low-temperature properties of distillate fuels. US 5 710 1 10 discloses a drilling fluid composition containing an oil well fluid anti-settling additive, which is a reaction product wherein the reactants are one or more alkoxylated aliphatic amino compounds and an organic polycarboxylic anhydride or acid.

Due to the problems of corrosion often encountered in oil and gas recovery operations, there is still a need to find a process and a treatment fluid that on the one hand further improve the permeability of a subterranean formation and avoid the disadvantages of working with strong acids at the elevated temperatures inherent for a large number of subterranean formations, and on the other hand provides a corrosion inhibition to metal surfaces involved in the oil and gas recovery operations and any downstreams operations. In addition, there is a need to provide a process and a treatment fluid which ensure better removal of the near-wellbore damage without depositing precipitates in the formation, as well as better prevention of well production decline due to solids movements. Preferably, the treatment fluid is biodegradable in both fresh and seawater and has a favourable eco-tox profile.

Surprisingly, it was found that in the compositions and kit of parts of the invention there is a good balance of properties. The compositions and kit of parts allow a very efficient treatment of the subterranean formations to make them more permeable and so enable the withdrawal of oil and or gas therefrom. At the same time, they give few undesired side effects such as unintended fracturing of the formation (if fracturing is intended then the pressure during the treatment will have to be adjusted accordingly) when used at the optimal injection rate, precipitation of salts and small particles leading to plugging of the formation, and corrosion. Also without the addition of any viscosifier the fluids of the invention have a favourable viscosity build-up, i.e. the viscosity of the fluids increases during the use thereof. Also, the compositions of the invention can be effective without needing a full amount of mutual solvent to transport the oil and/or gas from the formation, as it has been found that with the addition of a small amount of surfactant the compositions can already transport oil and/or gas in an acceptable amount. The compositions of the invention have a prolonged activity and lead to a decreased surface spending and as such avoid face dissolution and therefore act deeper in the formation. Besides being able to provide the improved permeability of subterranean formations the composition of the invention and the kit of parts of the invention in addition have the advantage of a high acidity without any deposit formation when used in subterranean formations. At the same time, it was found that in the compositions of the invention and the kit of parts of the invention the presence of the chelating agents, especially of MGDA, HEDTA and GLDA, and most of all of GLDA, ensures that smaller amounts of other components such as the polyesteramine or the polyester polyquaternary ammonium compound, but also the further additives like, corrosion inhibitor intensifiers, anti-sludge agents, iron control agents, scale inhibitors are needed to still achieve a similar effect to that of state of the art treatment fluids, reducing the chemicals burden of the process and creating a more sustainable way to produce oil and/or gas. Under some conditions some of the further additives are even completely redundant. It should be realized that in state of the art treatment fluids for sandstone or shale formations often an anionic surfactant is present as well as a cationic corrosion inhibitor, which means a certain extent of mutual neutralization and hence deterioration of the other's effectivity. As it has now been found that fluids on the basis of GLDA require much less of the other components, the fluids of the invention and the kit of parts of the invention are easier to formulate and the above drawbacks can be avoided more easily. In addition, in the composition and the kit of parts of the invention there is an unexpected compatibility of the ingredients, surfactants, and corrosion inhibitors, as well as a synergistic effect with bactericides and/or biocides.

Summary of the Invention

It is an object of the present invention to at least partially meet the above-mentioned need in the art and to provide a composition, preferably an aqueous fluid composition which can be used as a process and stimulation fluid with corrosion inhibiting properties.

The present inventors have found that these objects can be met by a composition comprising certain polyester polyamine or polyester polyquaternary ammonium compounds, obtainable by the condensation of a fatty acid, a dicarboxylic acid or a derivative thereof, and an alkanolamine, where the condensation product optionally has been quaternised by a suitable alkylating agent, and a chelating agent

Thus, in a first aspect, the present invention relates to a composition as defined in the claims comprising (a) at least one polyester polyamine or polyester polyquaternary ammonium compound and (b) at least one chelating agent.

In a second aspect, the present invention relates to the use of a composition of the invention as a corrosion inhibitor, cleaning agent or descaling agent for metal surfaces, preferably for metal surfaces that are part of pipelines, pumps, tanks and other equipment used in oil- and gas fields or oil refineries. Consequently, the invention also relates to a method for protecting a metal surface from corrosion, for cleaning a metal surface or for descaling a metal surface by contacting the metal surface with an effective amount of a composition according to the invention.

In a third aspect, the present invention relates to a method for treating a subterranean formation, preferably a carbonate formation, a sandstone formation or a shale formation, comprising introducing into the formation a composition of the invention.

In a fourth aspect the invention relates to a kit of parts wherein one part contains the composition of the invention and the other part contains a fluid containing a mutual solvent and, optionally a surfactant, and relates to a kit of part wherein one part contains the composition of the invention and in addition a surfactant, and the other part contains a fluid containing a mutual solvent.

These and other aspects of the present invention will be apparent from the following detailed description of the invention.

Detailed Description of the Invention

The present invention relates to a composition comprising: (a) a condensation product obtainable by the condensation of a fatty acid, or mixture of acids, having the formula R¹COOH (I), wherein R¹CO is an acyl group having 8 to 24, preferably 12 to 24, more preferably 14 to 24, and most preferably 16 to 24, carbon atoms, that may be saturated or unsaturated, linear or branched; and a dicarboxylic acid or a derivative thereof having the formula (I la) or (lib)

wherein D is -OH, -CI, or -OR³, wherein R³ is a C1-C4 alkyl group; R2 is selected from the group consisting of a direct bond, an alkylene radical of the formula -(CH₂)_Z- , wherein z is an integer from 1 to 10, preferably from 2 to 4, and most preferably 4, a substituted alkylene radical wherein said alkylene radical is substituted by 1 or 2 -OH groups, the group -CH=CH-, a cycloalkylene, a cycloalkenylene and an arylene group; with an alkanolamine having the formula (III)

wherein each x independently is a number from 1 to 5, preferably 1 or 2, and the sum of all x (∑x) on molar average is a number between 2 and 10, preferably 2 to 4, most preferably 2, AO is an alkyleneoxy group having 2-4, preferably 2, carbon atoms, R⁴ is a C1-C3 alkyl group or a group [AO]_x wherein AO and x have the same meaning as above, or a partial or wholly quaternised derivative thereof; optionally said reaction between the fatty acid, the dicarboxylic acid, and the alkanolamine is followed by a further reaction step wherein part or all of the nitrogen atoms are quaternised by reaction with an alkylating agent R⁵X, wherein R⁵ is a hydrocarbyl group, preferably a C1-C4 alkyl group or the benzyl group, and X^" is an anion derived from the alkylating agent R⁵X; and

(b) a chelating agent, preferably selected from the group consisting of glutamic acid Ν,Ν-diacetic acid or a salt thereof (GLDA), methylglycine Ν,Ν-diacetic acid or a salt thereof (MGDA), N-hydroxyethyl ethylenediamine Ν,Ν',Ν'-triacetic acid or a salt thereof (HEDTA), more preferably glutamic acid Ν,Ν-diacetic acid or a salt thereof (GLDA)

The condensation products (a) described above may be represented by the general formula

(IV)

wherein R¹, AO, x, R2, and R⁴ have the same meaning as above; R⁵ is a hydrocarbyl group, preferably a C1 -C4 alkyl group, more preferably methyl, or the benzyl group, and X^" is an anion derived from the alkylating agent R⁵X; t is a number 0 or 1 , preferably 1 , and p is typically a number within the range 1 -15, and is on average from 1 , preferably from 2, most preferably from 3, to 15, preferably to 10, most preferably to 7 . The average value of p will depend on the molar ratios of the compounds (I), (lla) or (lib) and (III) in the reaction mixture, as well as on the reaction conditions.

It is to be understood that there may be molecules present in the product mixture that are not completely esterified with fatty acids, but the products of formula IV are the key compounds.

Suitable examples of fatty acids of formula (I) are 2-ethylhexanoic acid, n-octanoic acid, n-decanoic acid, n-dodecanoic acid, n-tetradecanoic acid, n-hexadecanoic acid, palmitoleic acid, n-octadecanoic acid, oleic acid, linoleic acid, linolenic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, coco fatty acid, rape seed fatty acid, soya fatty acid, tallow fatty acid, tall oil fatty acid, gadoleic acid and erucic acid.

The dicarboxylic acid derivative of general formula (lla) or (lib) may be a dicarboxylic acid as such, a dicarboxylic acid chloride, a diester of a dicarboxylic acid, or a cyclic anhydride of a dicarboxylic acid. The most suitable derivatives are the dicarboxylic acids and their corresponding cyclic anhydrides. Illustrative examples of dicarboxylic acid derivatives include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, phthalic acid, tetrahydrophthalic acid, maleic acid, malic acid, tartaric acid, their corresponding acid chlorides, their corresponding methyl or ethyl esters, and their corresponding cyclic anhydrides. Suitable alkanolamines are N-methyl diethanolamine and N-methyl diisopropanolamine, optionally alkoxylated with ethylene oxide, propylene oxide, butylene oxide or mixtures thereof. If more than one alkylene oxide is reacted with the alkanolamine, the different alkylene oxides may be added in blocks in any order, or may be added randomly. The alkoxylation may be performed by any suitable method known in the art by using e.g. an alkaline catalyst, such as KOH, or an acid catalyst.

In preferred embodiments, (I) is an unsaturated fatty acid or a mixture of fatty acids which contains at least 30 wt% of unsaturated fatty acid(s), (I la) is adipic acid and (III) is N-methyl diethanolamine.

A suitable method for the preparation of the products which are the subject of the present invention comprises the steps of mixing a compound of formula (I) as defined above with a compound of formula (I la) or (lib) as defined above and a compound of formula (III) as defined above, effecting an esterification condensation reaction between the compounds in the mixture, adding an alkylating agent to the condensation reaction product, and effecting a quaternisation reaction of the condensation product.

The esterification condensation reactions taking place between the compounds (I), (I I a) or (lib), and (III) are well-known per se in the art. The reactions are preferably performed in the presence of an esterification catalyst, such as a Bronstedt or Lewis acid, for example methanesulfonic acid, p-toluenesulfonic acid, citric acid or BF₃. When a dicarboxylic acid derivative of formula (I I a) is used, wherein D is O-R⁴, the reaction is a transesterification, which alternatively could be performed in the presence of an alkaline catalyst. Also the carboxylic acid (I) may be added as e.g. its methyl ester. Alternatively, other conventional techniques known by the person skilled in the art could be used starting from other derivatives of the dicarboxylic acids, such as their anhydrides or their acid chlorides.

As would also be clear to a person skilled in the art, alternatively the different esterification reactions could be performed in more than one step, e.g. by first condensing the dicarboxylic acid derivative (I la) or (lib) with the alkanolamine (III), and then adding the carboxylic acid (I) in a next step. The reactions can take place with or without solvents added. If solvents are present during the reaction, the solvents should be inert to esterification, e.g. toluene or xylene.

The esterification condensation reaction between the components (I), (I la) or (lib), and (III) is suitably effected by heating the mixture at a temperature suitably between 120 and 220°C for a period of from 2 to 20 hours, optionally at a reduced pressure of from 5 to 200 mbar. When t in formula (IV) is 0, the product is a tertiary polyesteramine compound, and when t is 1 , the product is a polyester polyquaternary ammonium compound. Preferably, t is 1 . Quaternisation is a reaction type that is well-known in the art. For the quaternisation step, the alkylating agent R⁵X is suitably selected from the group consisting of methylchloride, methylbromide, dimethylsulfate, diethylsulfate, dimethylcarbonate, and benzylchloride, the most preferred alkylating agents being methylchloride, dimethylsulfate, dimethylcarbonate or benzyl chloride. As stated above, the quaternisation may suitably be performed on the condensation product between the fatty acid, alkanolamine, and diacid. Principally, following an alternative synthesis route, the quaternisation of the alkanolamine (III) may be performed as a first step, which would then be followed by an esterification reaction between (I), (lla) or (lib), and quaternised (III). Either a part of, or all of, the nitrogen atoms may be quaternised. As a further alternative, if a quaternised derivative is desired, a reaction product between the tertiary alkanolamine (III) and a dicarboxylic acid derivative (lla) or (lib) may be reacted with an alkylating agent, e.g. methylchloride or dimethylsulfate, to yield a product that is partly or totally quaternised, before reaction with the carboxylic acid (I). Also, the two processes can be combined such that first a partially quaternised compound is esterified and the resulting polyester is further quaternised.

Quaternisation reactions are normally performed in water or a solvent, such as isopropanol (I PA) or ethanol, or in mixtures thereof. Other alternative solvents could be ethylene glycol monobutyl ether, di(ethylene glycol) monobutyl ether (BDG), and other ethylene and propylene glycols, such as monoethylene glycol (MEG) and diethylene glycol (DEG). The reaction temperature of the quaternising reaction is suitably in the range of from 20 to 100°C, preferably at least 40, more preferably at least 50, and most preferably at least 55°C, and preferably at most 90°C. The heating is preferably stopped when the amount of basic nitrogen is < 0.1 mmol/g, as measured by titration with 0.1 M perchloric acid in glacial acetic acid.

Condensation products (a) where all nitrogen atoms of the product are quaternary are preferred. The molar ratio between the fatty acid, or mixture of acids, having the formula R¹COOH (I) and the alkanolamine (III) in the reaction mixture is suitably 1 :1 .2 to 1 :10, more preferably 1 :1.5 to 1 :5, still more preferably 1 :2 to 1 :4, and most preferably 1 :2 to 1 :3, and the ratio between the fatty acid (I) and the dicarboxylic acid or derivative (lla) or (lib) is suitably 2:1 to 1 :8, preferably 1 :1 to 1 :8, more preferably 1 :1 .2 to 1 :6, still more preferably 1 :1 .5 to 1 :5, even more preferably 1 :1 .5 to 1 :4, yet more preferably 1 :1 .5 to 1 :3, and most preferably 1 :1.5 to 1 :2.5.

An example of a condensation product (a) has the structure of formula (IVa) shown below

wherein RC=0 is an acyl group having 8-24 carbon atoms, preferably 12 to 24 carbon atoms, and p is a number of at least 1 , preferably at least 2, and most preferably at least 3.

To produce a condensation product according to the example above wherein p is 3, 4 moles of methyldiethanolamine are reacted with 2 moles of a C8-C24 carboxylic acid and 3 moles of adipic acid, after which the product is quaternised by, e.g., methylchloride. The condensation products disclosed in the examples in the experimental section, according to the GPC/SEC analysis described below, possess a polymeric nature and a product obtainable by the above-mentioned condensation and quaternisation may be referred to as a "polymeric esteramine product" or a "polymeric quaternary ammonium ester product". In the examples condensation products (a) of the present invention have been shown by GPC/SEC analysis to consist for > 86% w/w of polymer molecules with two fatty acid units, two or more alkanolamine units, and one or more diacid/acid anhydride units.

Thus, the condensation products (a) should preferably consist for > 65% w/w, more preferably for > 75% w/w, and most preferably for > 85% w/w of molecules with two fatty acid units, two or more alkanolamine units, and one or more diacid/acid anhydride units. Further, the GPC/SEC analysis in combination with fraction analysis using mass spectroscopy reveals that almost all in the condensation product product (>85% w/w) have a molecular weight > 700 Dalton. Details on the analysis procedure are given below in the experimental section. All molecular weights as presented herein are determined by this procedure.

In different international regulations products with Mw > 700 are considered too large to penetrate biological membranes and thereby not to bioaccumulate in the feed chain, see e.g. Manuela Pavan, Andrew P. Worth and Tatiana I. Netzeva "Review of QSAR Models for Bioconcentration", EUR 22327 EN, European Commission, Directorate - General Joint Research Centre, Institute for Health and Consumer Protection, European Communities, 2006. This is thus an advantage of the products of the present invention from an environmental point of view.

The condensation products (a) have been shown to have corrosion inhibiting properties, especially for protecting metal surfaces from corrosion. The chelating agent is preferably selected from the group consisting of glutamic acid Ν,Ν-diacetic acid or a salt thereof (GLDA), methylglycine Ν,Ν-diacetic acid or a salt thereof (MGDA), N-hydroxyethyl ethylenediamine Ν,Ν',Ν'-triacetic acid or a salt thereof (HEDTA), preferably GLDA.

Salts of the chelating agents, preferably of GLDA, MGDA and/or HEDTA, that can be used are their alkali metal, alkaline earth metal, or ammonium full and partial salts. Also mixed salts containing different cations can be used. Preferably, the sodium, potassium, and ammonium full or partial salts of GLDA are used.

The compositions of the invention are preferably aqueous compositions, usually aqueous fluids, i.e. they preferably contain water as a solvent, wherein water can be e.g. fresh water, produced water or seawater, though other solvents may be added as well, as further explained below.

Composition, especially aqueous fluid compositions, of the invention have been found to be useful as process and/or treatment fluids for use in oil and/or gas production processes, for instance in well treatment and stimulation processes, wherein the fluids come in contact with metal surfaces, such as pipes, for example drilling pipes and transportation pipes, and storage tanks. A composition of the present invention preferably contains from 5, more preferably from 10, to 30, preferably to 20 wt% of the chelating agent (b), based on the total weight of the composition.

A composition of the present invention preferably contains from 0.0005, more preferably from 0.005, still more preferably from 0.01 , even more preferably from 0.05, most preferably from 0.1 , to 5, more preferably to 2, most preferably to 1 wt% of the condensation product (a), based on the total weight of the composition.

In a composition of the present invention, the weight ratio of condensation product (a) to chelating agent (b) is from 1 :60,000, preferably from 1 :6,000, more preferably from 1 :4,000, even more preferably from 1 :600, most preferably from 1 :400, to 1 :5, preferably 1 :10, more preferably to 1 :60.

All the wt% and vol% ranges and numbers are based on the total composition unless otherwise explicitly stated.

The composition of the present invention may be used for corrosion inhibition of metal surfaces, preferably ferrous metals or alloys, such as iron and steel, chromium-based metals, like chromium alloys, chromium-nickel alloys or chromium-containing stainless steels, of various flow lines, pipelines, pumps, tanks and other equipment preferably used in oil- and gas fields or refineries in all of the above-mentioned situations. The corrosion inhibiting properties of the composition of the present invention is probably utilized at temperatures of from 32, preferably from 77, to 300, preferably to 280, more preferably to 250 °F.

With regard to the use of the composition as corrosion inhibitors in various flow lines, the fluid content can vary over wide ranges, e.g. oil cuts may vary from 1 % in field situations to 100% in e.g. refineries, and the composition of the possibly co-transported water can vary a lot as well when it comes to e.g. dissolved solids and salts contents. For example, the vast majority of seawater has a salinity of 3.1 - 3.8% by weight, being on the average about 3.5% in the world's oceans, but the water in the flow lines, when present, could even have a salt content of up to 7% by weight, e.g. up to 6%, such as up to 4%. On the other hand, the water may also be fresh or brackish water with lower salt contents, for example as low as 0.3%, even as low as 0.05% and down to < 0.01 %; brackish water may exhibit a large variation from time to time having a salt content of about 0.05% up to about 3%. Typically, the metal surfaces to be protected will be in contact with water of differing salt content, as exemplified above.

In a procedure of this invention, a composition of the invention is added to a flowing liquid which may contain both oil and water, at any point in a flow line upstream of the point or line that is intended to be protected. The dosage of corrosion inhibitor needed to obtain sufficient protection varies with the application, but dosing is suitably in such an amount that the concentration of the condensation product (a) at the point of protection is between 1 and 2,000 ppm (by weight), preferably between 1 and 500 ppm, and most preferably between 1 and 150 ppm. Even though continuous dosage is the preferred use of the compounds of this invention, another possible mode is batch treatment, where the preferred dosage of condensation product (a) is between 1 and 5,000 ppm.

The composition of the invention may be used as a treatment fluid for the treatment of subterranean formations, with the additional benefit of having corrosion inhibiting properties.

Hence the present invention covers a process for treating a subterranean formation comprising introducing the composition of the invention containing the composition of the invention into the formation, preferably the composition wherein the chelating agent is glutamic acid Ν,Ν-diacetic acid or a salt thereof (GLDA), methylglycine N,N-diacetic acid or a salt thereof (MGDA), N-hydroxyethyl ethylenediamine Ν,Ν',Ν'-triacetic acid or a salt thereof (HEDTA).

In an embodiment the process of the invention involves a fracturing step. Accordingly, the invention also relates to a process for treating a formation comprising a step of fracturing the formation and a step of introducing the composition of the invention into the formation, preferably the composition wherein the chelating agent is glutamic acid Ν,Ν-diacetic acid or a salt thereof (GLDA), methylglycine Ν,Ν-diacetic acid or a salt thereof (MGDA), or N-hydroxyethyl ethylenediamine Ν,Ν',Ν'-triacetic acid or a salt thereof (HEDTA), wherein the fracturing step can take place before introducing the fluid into the formation, while introducing the fluid into the formation or subsequent to introducing the fluid into the formation.

The term treating in this application is intended to cover any treatment of the formation with the fluid. It specifically covers treating the formation with the fluid to achieve at least one of (i) an increased permeability, (ii) the removal of small particles, and (iii) the removal of inorganic scale, and so enhance the well performance and enable an increased production of oil and/or gas from the formation. At the same time it may cover cleaning of the wellbore and descaling of the oil/gas production well and production equipment, like pipelines, pumps, tanks, casing, containers, tubular, and other equipment used in oil- and gas fields or oil refineries.

A subterranean formation, preferably a carbonate, a sand stone formation or a shale formation, may be treated by a method which includes introducing a composition of the invention into the formation. The method for treatment of a subterranean formation can also be performed using the kit of parts of the present invention This kit of parts is suitable for a treatment process consisting of several stages, such as the pre-flush, main treatment and postflush stage, wherein one part of the kit of parts for one stage of the treatment process, contains the composition of the invention, and a surfactant, and the other part of the kit of parts for the other stage of the treatment process, contains a mutual solvent, or wherein one part contains the composition of the invention, and the other part contains a mutual solvent and a surfactant. A pre- or post-flush is a fluid stage pumped into the formation prior to or after the main treatment. The purposes of the pre- or post-flush include but are not limited to adjusting the wettability of the formation, displacing formation brines, adjusting the salinity of the formation, dissolving calcareous material and dissolving iron scales. Such a kit of parts can be conveniently used in the process of the invention, wherein the part containing a fluid containing mutual solvent and, in one embodiment, a surfactant is used as a preflush and/or postflush fluid and the other part containing the composition of the invention, and, in one embodiment, a surfactant is used as the main treatment fluid.

For several reasons when treating a subterranean formation a surfactant is added to main treatment fluids or in a separate fluid during the treatment, such surfactant helps to make the formation water-wet, thereby making the main treatment more efficient and allowing a better and deeper contact of the main treatment fluid with the subterranean formation. In addition, adding a surfactant makes the treatment fluids that are commonly aqueous better capable of transporting non-aqueous materials like crude oil.

The method for treatment of a subterranean formation can be performed at basically any temperature that is encountered when treating a subterranean formation. The process of the invention is preferably performed at a temperature of between 35 (about 2°C) and 400°F (about 204°C). More preferably, the fluids are used at a temperature where they best achieve the desired effects, which means a temperature of between 77 (about 25°C) and 300°F (about 149°C).

It is to be understood that improved permeability is often achieved by matrix acidizing of the formation, but that increased permeability can also be achieved by hydraulic fracturing or acidic fracturing.

In one embodiment, the method for treating a subterranean formation can be performed at an increased pressure, which means a pressure higher than atmospheric pressure. In many instances it is preferred to pump the fluids into the formation under pressure. If fracturing the formation is not intended, the pressure used is below fracture pressure, i.e. the pressure at which a specific formation is susceptible to fracture. Fracture pressure can vary a lot depending on the formation treated, but is well known by the person skilled in the art. If fracturing of the formation is intended, then in a preferred embodiment the pressure is above fracture pressure.

The pH of the composition of the invention can range from 1 to 14, preferably 1 .7 to 14. More preferably, however, it is between 3.5 and 13, as in the very acidic ranges of 1.7 to 3.5 and the very alkaline range of 13 to 14, some undesired side effects may be caused by the composition in a subterranean formation, such as too fast dissolution of carbonate giving excessive C0₂ formation or an increased risk of reprecipitation. For a better carbonate dissolving capacity it is preferably acidic. On the other hand, it must be realized that highly acidic solutions are more expensive to prepare. Consequently, the solution even more preferably has a pH of 3.5 to 8. In the context of the present invention, the pH value is reported as measured at 20°C.

The composition of the invention may contain other additives that improve the functionality of the composition, as is known to anyone skilled in the art, such as one or more of the group of mutual solvents, anti-sludge agents, surfactants, corrosion inhibitor intensifiers, foaming agents, viscosifiers, wetting agents, diverting agents, oxygen scavengers, carrier fluids, fluid loss additives, friction reducers, stabilizers, rheology modifiers, gelling agents, scale inhibitors, breakers, salts, brines, pH control additives such as further acids and/or bases, bactericides/biocides, particulates, crosslinkers, salt substitutes (such as tetramethyl ammonium chloride), relative permeability modifiers, sulfide scavengers, fibres, nanoparticles, consolidating agents (such as resins and/or tackifiers), combinations thereof, or the like. When the composition is used for treating sandstone or shale formations, the composition of the invention may contain a nonionic or anionic surfactant. Even more preferably, the surfactant is anionic. The concentration of surfactant may usually be in the range of from 0 to 5, such as to 2 wt%.

When the composition is used for treating carbonate formations, the composition of the invention may contain a nonionic or cationic surfactant. Even more preferably, the surfactant is then cationic. The concentration of surfactant may usually be in the range of from 0 to 5, such as to 2 wt%.

The nonionic surfactant in the composition is preferably selected from the group consisting of alkanolamides, alkoxylated alcohols, alkoxylated amines, amine oxides, alkoxylated amides, alkoxylated fatty acids, alkoxylated fatty amines, alkoxylated alkyl amines (e.g., cocoalkyl amine ethoxylate), alkyl phenyl polyethoxylates, lecithin, hydroxylated lecithin, fatty acid esters, glycerol esters and their ethoxylates, glycol esters and their ethoxylates, esters of propylene glycol, sorbitan, ethoxylated sorbitan, polyglycosides and the like, and mixtures thereof. Alkoxylated alcohols, preferably ethoxylated alcohols, optionally in combination with (alkyl) polyglycosides, are the most preferred nonionic surfactants.

The anionic (sometimes zwitterionic, as two charges are combined into one compound) surfactant is preferably selected from the group of sulfonates, hydrolyzed keratin, sulfosuccinates, taurates, betaines, modified betaines, alkylamidobetaines (e.g., cocoamidopropyl betaine).

The cationic surfactant may comprise quaternary ammonium compounds (e.g., trimethyl tallow ammonium chloride, trimethyl coco ammonium chloride), derivatives thereof, and combinations thereof.

High-temperature applications may benefit from the presence of an oxygen scavenger in an amount of less than about 2 volume percent of the solution.

The mutual solvent is a chemical additive that is soluble in oil, water, acids (often HCI based), and other well treatment fluids. Mutual solvents are routinely used in a range of applications, controlling the wettability of contact surfaces before, during and/or after a treatment, and preventing or breaking emulsions. Mutual solvents are used, as insoluble formation fines pick up organic film from crude oil. These particles are partially oil-wet and partially water-wet. This causes them to collect material at any oil- water interface, which can stabilize various oil-water emulsions. Mutual solvents remove organic films leaving them water-wet, thus emulsions and particle plugging are eliminated. If a mutual solvent is employed, it is preferably selected from the group which includes, but is not limited to, lower alcohols such as methanol, ethanol, 1 - propanol, 2-propanol, and the like, glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol-polyethylene glycol block copolymers, and the like, and glycol ethers such as 2-methoxyethanol, diethylene glycol monomethyl ether, and the like, substantially water/oil-soluble esters, such as one or more C2-esters through C10- esters, and substantially water/oil-soluble ketones, such as one or more C2-C10 ketones, wherein substantially soluble means soluble in more than 1 gram per liter, preferably more than 10 grams per liter, even more preferably more than 100 grams per liter, most preferably more than 200 grams per liter. The mutual solvent is preferably present in an amount of 1 to 50 wt% on total fluid. A preferred water/oil- soluble ketone is methyl ethyl ketone. A preferred substantially water/oil-soluble alcohol is methanol. A preferred substantially water/oil-soluble ester is methyl acetate. A more preferred mutual solvent is ethylene glycol monobutyl ether, generally known as EGMBE

The amount of glycol solvent in the solution is preferably about 1 wt% to about 10 wt%, more preferably between 3 and 5 wt%. More preferably, the ketone solvent may be present in an amount from 40 wt% to about 50 wt%; the substantially water-soluble alcohol may be present in an amount within the range of about 20 wt% to about 30 wt%; and the substantially water/oil-soluble ester may be present in an amount within the range of about 20 wt% to about 30 wt%, each amount being based upon the total weight of the solvent in the fluid.

The antisludge agent can be chosen from the group of mineral and/or organic acids used to stimulate sandstone hydrocarbon-bearing formations. The function of the acid is to dissolve acid-soluble materials so as to clean or enlarge the flow channels of the formation leading to the wellbore, allowing more oil and/or gas to flow to the wellbore.

Methods for preventing or controlling sludge formation with its attendant flow problems during the acidization of crude-containing formations include adding "anti-sludge" agents to prevent or reduce the rate of formation of crude oil sludge, which anti-sludge agents stabilize the acid-oil emulsion and include alkyl phenols, fatty acids, and anionic surfactants. Frequently used as the surfactant is a blend of a sulfonic acid derivative and a dispersing surfactant in a solvent. Such a blend generally has dodecyl benzene sulfonic acid (DDBSA) or a salt thereof as the major dispersant, i.e. anti-sludge, component.

Additional corrosion inhibitors may be selected from the group of amine and quaternary ammonium compounds and sulfur compounds. Examples are diethyl thiourea (DETU), which is suitable up to 185°F (about 85°C), alkyl pyridinium or quinolinium salt, such as dodecyl pyridinium bromide (DDPB), and sulfur compounds, such as thiourea or ammonium thiocyanate, which are suitable for the range 203-302°F (about 95-150°C), benzotriazole (BZT), benzimidazole (BZI), dibutyl thiourea, a proprietary inhibitor called TIA, and alkyl pyridines.

One or more corrosion inhibitor intensifiers may be added, such as for example formic acid, potassium iodide, antimony chloride, copper iodide, sodium thiosulfate, and 2- mercaptoethanol, preferably sodium thiosulfate.

A composition of the invention may comprise from 0.01 , preferably from 0.05, more preferably from 0.1 , to 1 , preferably to 0.5, more preferably to 0.3 wt% of such corrosion inhibitor intensifier, for example sodium thiosulfate, based on the total weight the composition.

One or more salts may be used as rheology modifiers to modify the rheological properties (e.g., viscosity and elastic properties) of the composition. These salts may be organic or inorganic. Examples of suitable organic salts include, but are not limited to, aromatic sulfonates and carboxylates (such as p-toluene sulfonate and naphthalene sulfonate), hydroxynaphthalene carboxylates, salicylate, phthalate, chlorobenzoic acid, phthalic acid, 5-hydroxy-1 -naphthoic acid, 6-hydroxy-1 -naphthoic acid, 7-hydroxy-1 - naphthoic acid, 1 -hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 5-hydroxy-2- naphthoic acid, 7-hydroxy-2-naphthoic acid, 1 ,3-dihydroxy-2-naphthoic acid, 3,4- dichlorobenzoate, trimethyl ammonium hydrochloride, and tetramethyl ammonium chloride. Examples of suitable inorganic salts include water-soluble potassium, sodium, and ammonium halide salts (such as potassium chloride and ammonium chloride), calcium chloride, calcium bromide, magnesium chloride, sodium formate, potassium formate, cesium formate, and zinc halide salts. A mixture of salts may also be used, but it should be noted that preferably chloride salts are mixed with chloride salts, bromide salts with bromide salts, and formate salts with formate salts.

Wetting agents that may be suitable for use in this invention include crude tall oil, oxidized crude tall oil, surfactants, organic phosphate esters, modified imidazolines and amidoamines, alkyl aromatic sulfates and sulfonates, and the like, and combinations or derivatives of these and similar such compounds that should be well known to one of skill in the art.

The foaming gas may be air, nitrogen or carbon dioxide. Nitrogen is preferred.

Gelling agents in a preferred embodiment are polymeric gelling agents. Examples of commonly used polymeric gelling agents include, but are not limited to, biopolymers, polysaccharides such as guar gums and derivatives thereof, cellulose derivatives, synthetic polymers like polyacrylamides and viscoelastic surfactants, and the like. These gelling agents, when hydrated and at a sufficient concentration, are capable of forming a viscous solution.

Viscosifiers may include natural polymers and derivatives such as xantham gum and hydroxyethyl cellulose (HEC) or synthetic polymers and oligomers such as poly(ethylene glycol) [PEG], poly(diallyl amine), poly(acrylamide), poly(aminomethyl propyl sulfonate) [AMPS polymer], poly(acrylonitrile), polyvinyl acetate), polyvinyl alcohol), polyvinyl amine), polyvinyl sulfonate), poly(styryl sulfonate), poly(acrylate), poly(methyl acrylate), poly(methacrylate), poly(methyl methacrylate), polyvinyl pyrrolidone), polyvinyl lactam), and co-, ter-, and quater-polymers of the following (co- )monomers: ethylene, butadiene, isoprene, styrene, divinyl benzene, divinyl amine, 1 ,4- pentadiene-3-one (divinyl ketone), 1 ,6-heptadiene-4-one (diallyl ketone), diallyl amine, ethylene glycol, acrylamide, AMPS, acrylonitrile, vinyl acetate, vinyl alcohol, vinyl amine, vinyl sulfonate, styryl sulfonate, acrylate, methyl acrylate, methacrylate, methyl methacrylate, vinyl pyrrolidone, and vinyl lactam. Yet other viscosifiers include clay- based viscosifiers, especially laponite and other small fibrous clays such as the polygorskites (attapulgite and sepiolite). When using polymer-containing viscosifiers, the viscosifiers may be used in an amount of up to 5% by weight of the composition.

Examples of suitable brines include calcium bromide brines, zinc bromide brines, calcium chloride brines, sodium chloride brines, sodium bromide brines, potassium bromide brines, potassium chloride brines, sodium nitrate brines, sodium formate brines, potassium formate brines, cesium formate brines, magnesium chloride brines, sodium sulfate, potassium nitrate, and the like. A mixture of salts may also be used in the brines, but it should be noted that preferably chloride salts are mixed with chloride salts, bromide salts with bromide salts, and formate salts with formate salts. The brine chosen should be compatible with the formation and should have a sufficient density to provide the appropriate degree of well control. Additional salts may be added to a water source, e.g., to provide a brine, and a resulting treatment fluid, in order to have a desired density. The amount of salt to be added should be the amount necessary for formation compatibility, such as the amount necessary for the stability of clay minerals, taking into consideration the crystallization temperature of the brine, e.g., the temperature at which the salt precipitates from the brine as the temperature drops. Preferred suitable brines may include seawater and/or formation brines.

Examples of suitable pH control additives which may optionally be included in the treatment fluids of the present invention are acid compositions and/or bases. A pH control additive may be necessary to maintain the pH of the treatment fluid at a desired level, e.g., to improve the effectiveness of certain breakers and to reduce corrosion on any metal present in the wellbore or formation, etc. One of ordinary skill in the art will, with the benefit of this disclosure, be able to recognize a suitable pH for a particular application.

In one embodiment, the pH control additive may be an acid composition. Examples of suitable acid compositions may comprise an acid, an acid-generating compound, and combinations thereof. Any known acid may be suitable for use with the treatment fluids of the present invention. Examples of acids that may be suitable for use in the present invention include, but are not limited to, organic acids (e.g., formic acids, acetic acids, carbonic acids, citric acids, glycolic acids, lactic acids, and the like), inorganic acids (e.g., hydrochloric acid, hydrofluoric acid, phosphonic acid, p-toluene sulfonic acid, and the like), and combinations thereof. Preferred acids are HCI and organic acids.

Examples of acid-generating compounds that may be suitable for use in the present invention include, but are not limited to, esters, aliphatic polyesters, ortho esters, which may also be known as ortho ethers, poly(ortho esters), which may also be known as poly(ortho ethers), poly(lactides), poly(glycolides), poly(epsilon-caprolactones), poly(hydroxybutyrates), poly(anhydrides), or copolymers thereof. Other suitable acid- generating compounds include: esters including, but not limited to, ethylene glycol monoformate, ethylene glycol diformate, diethylene glycol diformate, glyceryl monoformate, glyceryl diformate, glyceryl triformate, methylene glycol diformate, and formate esters of pentaerythritol. The pH control additive also may comprise a base to elevate the pH of the fluid. Generally, a base may be used to elevate the pH of the mixture to greater than or equal to about 7. Having the pH level at or above 7 may have a positive effect on a chosen breaker being used and may also inhibit the corrosion of any metals present in the wellbore or formation, such as tubing, screens, etc. In addition, having a pH greater than 7 may also impart greater stability to the viscosity of the treatment fluid, thereby enhancing the length of time that viscosity can be maintained. This could be beneficial in certain uses, such as in longer-term well control and in diverting. Any known base that is compatible with the gelling agents of the present invention can be used in the fluids of the present invention. Examples of suitable bases include, but are not limited to, sodium hydroxide, potassium carbonate, potassium hydroxide, sodium carbonate, and sodium bicarbonate. One of ordinary skill in the art will, with the benefit of this disclosure, recognize the suitable bases that may be used to achieve a desired pH elevation.

In some embodiments, the fluids of the present invention and the fluids in the kit of parts of the invention may contain bactericides or biocides, inter alia, to protect the subterranean formation as well as the fluid from attack by bacteria. Such attacks can be problematic because they may lower the viscosity of the fluid, resulting in poorer performance, such as poorer sand suspension properties, for example. Any bactericides known in the art are suitable. Biocides and bactericides protecting against bacteria that may attack GLDA or sulfates are preferred. An artisan of ordinary skill will, with the benefit of this disclosure, be able to identify a suitable bactericide and the proper concentration of such bactericide for a given application.

Examples of suitable bactericides and/or biocides include, but are not limited to, phenoxyethanol, ethylhexyl glycerine, benzyl alcohol, methyl chloroisothiazolinone, methyl isothiazolinone, methyl paraben, ethyl paraben, propylene glycol, bronopol, benzoic acid, imidazolinidyl urea, a 2,2-dibromo-3-nitrilopropionamide, and a 2- bromo- 2-nitro-1 ,3-propane diol. In one embodiment, the bactericides are present in the fluid in an amount in the range of from about 0.001 to about 1.0wt% by.

Fluids of the present invention also may comprise breakers capable of reducing the viscosity of the fluid at a desired time. Examples of such suitable breakers for fluids of the present invention include, but are not limited to, oxidizing agents such as sodium chlorites, sodium bromate, hypochlorites, perborate, persulfates, and peroxides, including organic peroxides. Other suitable breakers include, but are not limited to, suitable acids and peroxide breakers, triethanol amine, as well as enzymes that may be effective in breaking. The breakers can be used as is or encapsulated.

The fluids of the present invention also may comprise suitable fluid loss additives. Such fluid loss additives may be particularly useful when a fluid of the present invention is used in a fracturing application or in a fluid used to seal a formation against invasion of fluid from the wellbore. Any fluid loss agent that is compatible with the fluids of the present invention is suitable for use in the present invention. Examples include, but are not limited to, starches, silica flour, gas bubbles (energized fluid or foam), benzoic acid, soaps, resin particulates, relative permeability modifiers, degradable gel particulates, diesel or other hydrocarbons dispersed in fluid, and other immiscible fluids.

Another example of a suitable fluid loss additive is one that comprises a degradable material. Suitable examples of degradable materials include polysaccharides such as dextran or cellulose; chitins; chitosans; proteins; aliphatic polyesters; poly(lactides); poly(glycolides); poly(glycolide-co-lactides); poly(epsilon-caprolactones); poly(3- hydroxybutyrates); poly(3-hydroxybutyrate-co-hydroxyvalerates); poly(anhydrides); aliphatic poly(carbonates); poly(ortho esters); poly(amino acids); poly(ethylene oxides); poly(phosphazenes); derivatives thereof; or combinations thereof.

In some embodiments, a fluid loss additive may be included in an amount of about 5 to about 2,000 Ibs/Mgal (about 600 to about 240,000 g/Mliter) of the fluid. In some embodiments, the fluid loss additive may be included in an amount from about 10 to about 50 Ibs/Mgal (about 1 ,200 to about 6,000 g/Mliter) of the fluid.

In certain embodiments, a stabilizer may optionally be included in the fluids of the present invention. It may be particularly advantageous to include a stabilizer if a chosen fluid is experiencing viscosity degradation. One example of a situation where a stabilizer might be beneficial is where the BHT (bottom hole temperature) of the wellbore is sufficient to break the fluid by itself without the use of a breaker. Suitable stabilizers include, but are not limited to, sodium thiosulfate, methanol, and salts such as formate salts and potassium or sodium chloride. Such stabilizers may be useful when the fluids of the present invention are utilized in a subterranean formation having a temperature above about 200°F (about 93°C). If included, a stabilizer may be added in an amount of from about 1 to about 50 Ibs/Mgal (about 120 to about 6,000 g/Mliter) of fluid. Scale inhibitors may be added to the fluids of the present invention, for example, when such fluids are not particularly compatible with the formation waters in the formation in which they are used. These scale inhibitors may include water-soluble organic molecules with carboxylic acid, aspartic acid, maleic acids, sulfonic acids, phosphonic acid, and phosphate ester groups including copolymers, ter-polymers, grafted copolymers, and derivatives thereof. Examples of such compounds include aliphatic phosphonic acids such as diethylene triamine penta (methylene phosphonate) and polymeric species such as polyvinyl sulfonate.

The scale inhibitor may be in the form of the free acid but is preferably in the form of mono- and polyvalent cation salts such as Na, K, Al, Fe, Ca, Mg, NH₄. Any scale inhibitor that is compatible with the fluid in which it will be used is suitable for use in the present invention.

Suitable amounts of scale inhibitors that may be included in the fluids of the present invention may range from about 0.05 to 100 gallons per about 1 ,000 gallons (i.e. 0.05 to 100 liters per 1 ,000 liters) of the fluid.

Any particulates such as proppant, gravel that are commonly used in subterranean operations in sandstone formations may be used in the present invention (e.g., sand, gravel, bauxite, ceramic materials, glass materials, wood, plant and vegetable matter, nut hulls, walnut hulls, cotton seed hulls, cement, fly ash, fibrous materials, composite particulates, hollow spheres and/or porous proppant). It should be understood that the term "particulate" as used in this disclosure includes all known shapes of materials including substantially spherical materials, oblong, fibre-like, ellipsoid, rod-like, polygonal materials (such as cubic materials), mixtures thereof, derivatives thereof, and the like.

Oxygen scavengers may be needed to enhance the thermal stability of the GLDA. Examples thereof are sulfites and ethorbates.

Friction reducers can be added in an amount of up to 0.2 vol%. Suitable examples are viscoelastic surfactants and enlarged molecular weight polymers.

Crosslinkers can be chosen from the group of multivalent cations that can crosslink polymers such as Al, Fe, B, Ti, Cr, and Zr, or organic crosslinkers such as polyethylene amides, formaldehyde.

Sulfide scavengers can suitably be an aldehyde or ketone. Viscoelastic surfactants can be chosen from the group of amine oxides or carboxyl butane based surfactants.

In the process of the invention the fluid can be flooded back from the formation. Even more preferably, (part of) the solution is recycled.

It must be realized, however, that GLDA, being biodegradable chelating agents, will not completely flow back and therefore is not recyclable to the full extent.

EXAMPLES

General Experimental

Molecular Weight Determination The molecular weights and/or molecular weight ranges given in the examples in the experimental section were determined by the following method:

For separation, a SEC (Size Exclusion Chromatography) column was used. This means that porous particles are used to separate molecules of different sizes, and the molecules with the largest space-filling volume (more strictly, hydrodynamic radius) have the shortest retention times. Thus, in essence, in a SEC system the largest molecules elute first and the smallest molecules elute last.

The samples were dissolved in tetrahydrofuran and injected on a GPC/S EC-system (Gel Permeation Chromatography/Size Exclusion Chromatography), and then the fractions collected were analysed by mass spectrometry. Analytical description for molecular weight determination of polymer

The sample was dissolved in tetrahydrofuran and injected on a SEC-system equipped with three columns to separate the different homologues from each other. Each peak was collected as one fraction and the solvent was evaporated. The residue of each fraction was dissolved in acetonitrile/water 95/5 containing 0.5% acetic acid and injected via direct infusion into the ion trap MS detector. The molecular weights were determined for the different fractions. With molecules of very similar structure analysed by refractive index detector, area% can be approximated to weight%. Analytical conditions SEC

Precolumn: Phenogel 5μ linear 50x7.8mm (Phenomenex)

Columns: Phenogel 5μ 300x7.8 mm, three columns in series with pore sizes 500A, 100A, 50A (Phenomenex) Mobile phase: Tetrahydrofuran

Flow: 0.8 ml/min

Injection volume: 100 μΙ

Detector: Refractive Index

Analytical conditions Mass Spectrometer Direct infusion via syringe pump into LCQDuo (ThermoFinnigan) Ion Trap with ESI positive mode

Full Scan Mass Range: 150-2000 m/z Example 1 Step 1 Tallow fatty acid (Tefacid; 230.1 g, 0.82 mole), methyl diethanolamine (195.3 g, 1.64 mole) from Fluka, and adipic acid (179.7 g, 1.23 mole) from Fluka were added to a round-bottomed flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a mechanical stirrer. The reaction mixture was slowly heated to 174°C. Commencing at 150°C, the water produced during the reaction started to distil off. After 3.5h, vacuum was applied gradually in order to more completely remove the water. In 4h, the endpoint vacuum of 16 mbar was reached. The progress of the reaction was monitored by titration for acid value as well as by ¹H-NMR spectroscopy. After 7h at 174°C and 16 mbar the desired product was obtained. The acid value of the product was then 0.183 meq/g. 541 g of product were obtained. By using the SEC/MS method described above the product was shown consist for > 86 SEC area-% of molecules with two fatty acid units, two or more alkanolamine units, and one or more diacid/acid anhydride units. Further, the GPC/SEC analysis in combination with fraction analysis using mass spectroscopy reveals that almost all molecule components in the product (> 85% w/w) have a molecular weight > 700.

Step 2

In the second step, 240.2 g polyester from the first step and 43.5 g butyl diglycol as solvent were added to a stirred autoclave and heated to 57°C. Methylchloride (36.6 g) was added in 90 minutes. Post-reaction was then carried out for 10h at 93±3°C. ¹H- NMR spectroscopy showed that no unquaternised amine was left. 252 g of the final product were obtained as a paste containing 13.6% w/w of BDG.

The chain length of the individual molecules and the distribution of the different molecules in the product are not expected to change during step 2 of the synthesis. However, the Mw of each molecule containing one or more methyl diethanol amine fragments is higher after quaternisation, and consequently the Mw of the product as a whole will increase slightly as compared to the product of Example 1. Example 2

A polyester polyquaternary amine was synthesised as follows:

Step 1

Distilled oleic acid (Radacid 0213, 187,0 g, 0.66 mole), adipic acid (Fluka, 179.2 g, 1.23 mole) and methyldiethanolamine (Fluka, 194.4 g, 1 .63 mole) were added to a round- bottomed flask, fitted with a condenser, a thermometer, a heating mantel, a nitrogen inlet and a mechanical stirrer. The reaction mixture was heated up (set temp at 165 °C) and the produced during the reaction water was distilled off. The distillation started at 156 °C. The vacuum was applied in 2 h after distillation started. The process of going down in pressure took 1 .5 h (from atm till 8 mBar). The progress of the reaction was evaluated by the determination of acid value and by ¹H-NMR spectroscopy. After 9 h at 165 °C and 8 mBar, the acid value had decreased to 0.155 meq/g and the reaction was stopped. 495 g of intermediate product was collected.

Step 2

482.7 g of the above intermediate product and 249.7 g of butyl diglycol was added to the a stirred autoclave and heated to 58°C. Methylchloride (77.2 g, 1.529 mole) was added in portions for a period of three hours. Post-reaction was then carried out for 12 h at 76±3°C in order to ensure complete reaction. During this time the pressure in the autoclave dropped to 0.34 bar and then stayed constant.

Followingly, an additional 205 g of butyl diglycol was added to the autoclave, the reaction mixture was mixed during 10 min and the final product (containing 45 wt% butyl diglycol) was discharged from the autoclave. The amine value of the product was 0.02 meg/g.

Example 3

A polyester polyquaternary amine was synthesised as follows: Step 1 Oleic acid (479.3 g, 1 .69 mole), methyl diethanolamine (498.5 g, 4.18 mole) from Fluka, and adipic acid (458.6 g, 3.14 mole) from Fluka were added to a round- bottomed flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a mechanical stirrer. The reaction mixture was slowly heated to 174°C. Commencing at 156°C, the water produced during the reaction started to distil off. After 3h, vacuum was applied gradually in order to more completely remove the water. In 3h, the endpoint vacuum of 37 mbar was reached. The progress of the reaction was monitored by titration for acid value as well as by ¹ H-NMR spectroscopy. After 9h at 174°C and 37 mbar the desired product was obtained. The acid value of the product was then 0.248 meq/g. 1280 g intermediate product were obtained. Step 2

302.6 g of the polyester obtained from the first step and 54 g of water as solvent were added to a stirred autoclave and heated to 59°C. Methylchloride (50 g) was added in one hour. Post-reaction was then carried out for 1 1 h at 72±2°C.

¹ H-NMR spectroscopy showed that no unquaternised amine was left. 378 g of the final product were obtained as a dark brown viscous liquid containing 13% w/w of water.

Example 4

A polyester polyquaternary amine was synthesized as follows:

Step 1

N-Methyl Diethanol Amine (MDEA; 197.9 g, 1.66 mol) was charged to a 1 I autoclave. The system was closed, heated to 60°C and three N₂/vacuum cycles were performed. Then KOH solution (0.58g KOH in ca 20 ml MeOH) was added at 0.50 bar. Next, temperature was increased to 80°C (1 °C/min ramp) while pulling vacuum to remove the methanol.

The vacuum valve was closed and the temperature was increased to 160 °C. Addition of EO (293 g, 6.64 mol) was then initiated and an exothermic reaction was observed. The addition and post reaction were complete within one hour. The reaction product was then cooled to 80°C and 484 g of the product was collected as a dark brown oil. 0.57 g acetic acid was added to neutralize the KOH.

Step 2

Adipic acid (89.16 g, 0,61 mol) and oleic acid (Radacid 0213; 89.27 g, 0.328 mol) were added to 228.51 g ethoxilated MDEA from Step 1 at 60 °C in a 700 ml flank flask (equipped with over head stirring (U-bar), thermometer inside reaction connected to heating mantle, distillation set-up and N₂/vacuum connection) to give a uniform brown solution. The temperature was slowly increased to 165°C when distillation started. The reaction was kept at this temperature for 13.5 h and then at 175°C for 1 .5 h. Next, the reaction was cooled to room temperature and 356.4 g of the product was collected as a brown oil. The acid number was 0.356 mmol/g (indicating 89 % conversion).

Step 3

Polyester polyamine from Step 2 and Butyl Diglycol (BDG, 146,2 g) was added to an autoclave. Three N₂/vacuum cycles to remove oxygen and a pressure check to 3.6 bar of N₂ were performed. Stirring was set at 1500 rpm, the temperature was increased to 80°C and the system evacuated to 0.05 bar. Addition of CH₃CI was then initiated and 33.7 g of CH₃CI was added over 2 h while keeping the pressure below 2.5 bar. The temperature varied between 80-84°C.

A sample was then taken from the reaction and N_tot was measured to 0.239 mmol/g (89% conversion). Another 6.8 g CH₃CI was then added over 1 hour while keeping the pressure below 2.7 bar and temperature at 77°C. The reaction was left over night at this temperature. The reaction was then stopped and 504.1 g of the liquid brown product was collected.

Acid number was 0.26 mmol/g; N_tot = 0.043 mmol/g (97 % conversion); Active contents = 72 % (28 % BDG). Example 5 - Biodegradability

It is nowadays a well-established fact that a reasonable biodegradability often is required by society and authorities for man-made organic compounds that are used in applications where they could end up reaching the environment. For certain geographical and/or application areas certain minimum levels of biodegradability are in addition stated by regulatory bodies.

Compounds of the present invention were tested for biodegradability in seawater, following GLP standards, according to OECD Guideline for testing of chemicals, section 3; Degradation and accumulation, No. 306: biodegradability in seawater, Closed Bottle test. The biodegradation after 28 days for the products synthesised in Example 1 and Example 3 was > 60%. These examples demonstrate the generally good biodegradability of the condensation products according to the invention.

Example 6 - Corrosion Test

Simulation of corrosion in downhole conditions was performed in a 1 liter Buchi autoclave equipped with a glass liner to prevent any other metal/acid contact except for the test coupon itself. The thermocouple used for temperature measurements was also equipped with a glass liner.

The weight and size of the test coupon was accurately measured before the test (coupon dimensions ¾" x ½" x 1/16" inch with a 1/5" hole in the center). Before the test the coupon was cleaned with isopropyl alcohol.

Test coupons of the following materials were tested:

API-L80: Low carbon Steel API-L80

SS-410: Stainless steel Cr-13 (UNS 41000)

D2205: Stainless steel Duplex 2205 (UNS31803)

SAN28: Stainless steel SAN28 (SA2832)

The Buchi autoclave was filled with 0.4 liter of an aqueous solution having the composition as described below. The test coupon was submersed in the aqueous solution with a glass rod. After assembly and closure of the autoclave the headspace was purged 3 times with a small amount of nitrogen gas. For the experiments the headspace was filled as indicated with 10 mole% H₂S, 5mole% C0₂ and N₂ as balance or N₂, up to a pressure of approximately 800 PSI. Subsequently the autoclave content was heated to the desired temperature with an oil-heating bath and the final pressure rose up to 1000-1200 psi. As soon as the desired temperature was reached a timer was started. The pressure of >1000 psi was maintained during the whole test. After 6 hours, the autoclave was cooled with tap water to < 150°F.

As soon the temperature was below 210°F the pressure was relieved slowly through a sodium hydroxide scrubber (neutralization of H₂S) and the unit was purged again with nitrogen. The unit was opened and the test coupon retrieved. After the test the metal coupon was cleaned with a bristle brush and water (the seal materials were cleaned with isopropyl alcohol), allowed to dry, and the weight loss was determined.

Table 1

Aqueous Solution: 20 wt% GLDA-NaH₃ + indicated concentration of polymeric ester quat according to example 2 in water; Head space gas: 10 mole% H₂S, 5mole% C0₂ and N₂ as balance; Temperature: 250 °F

^* added as 55 wt% active in butyl diglycol Table 2

Aqueous Solution: 20 wt% GLDA-NaH₃ + indicated concentration of polymeric ester quat according to example 2 in water; Head space gas: N₂; Coupon Material: API L-80

^* added as 55 wt% active in butyl diglycol

Table 3

Aqueous Solution: 20 wt% GLDA-NaH₃ + 0.2 wt% (active) of polymeric ester quat according to example 2 + 0.2 wt% butyl diglycol + indicated concentration of sodium thiosulfate in water; Head space gas: 10 mole% H₂S, 5mole% C0₂ and N₂ as balance; Temperature: 300 °F; Coupon Material: API-L80¹

As is shown in the experiments, the polymeric ester quat of the invention can be used to reduce the weight loss (also referred to as the 6 hour metal loss) of the tested metal qualities to well below 0.05 Ibs/sq.ft in a 20 wt% GLDA solution, and that the metal loss further can be reduced by addition of a corrosion inhibitor intensifier.

Coupon was submersed by means of a PTFE cord

Claims

1 . Composition comprising at least

(a) a product obtainable by the reaction of a fatty acid, or mixture of acids, having the formula R¹COOH (I), wherein R¹CO is an acyl group having 8 to 24 carbon atoms, that may be saturated or unsaturated, linear or branched; and

a dicarboxylic acid or a derivative thereof having the formula (I la) or (lib)

wherein D is -OH, -CI, or -OR³, wherein R³ is a C1 -C4 alkyl group; R2 is selected from the group consisting of a direct bond, an alkylene radical of the formula - (CH₂)_z- , wherein z is an integer from 1 to 10, a substituted alkylene radical wherein said alkylene radical is substituted by 1 or 2 -OH groups, the group - CH=CH-, a cycloalkylene, a cycloalkenylene, and an arylene group;

with an alkanolamine having the formula (III)

wherein each x independently is a number between 1 and 5, and ∑x on molar average is a number between 2 and 10, AO is an alkyleneoxy group having 2-4 carbon atoms, R⁴ is a C1 -C3 alkyl group or a group [AO]_x wherein AO and x have the same meaning as above, or a partial or wholly quaternised derivative thereof; optionally said reaction between the fatty acid, the dicarboxylic acid, and the alkanolamine is followed by a further reaction step wherein part or all of the nitrogen atoms are quaternised by reaction with an alkylating agent R⁵X, wherin R⁵ is a hydrocarbyl group, and X^" is an anion derived from the alkylating agent R⁵X; and

(b) a chelating agent.

2. A composition according to claim 1 , wherein said chelating agent is selected from the list consisting of glutamic acid Ν,Ν-diacetic acid or a salt thereof (GLDA), methylglycine Ν,Ν-diacetic acid or a salt thereof (MGDA), N-hydroxyethyl ethylenediamine Ν,Ν',Ν'-triacetic acid or a salt thereof (HEDTA). A composition according to claim 1 or 2, comprising glutamic acid N,N-diacetic acid or a salt thereof (GLDA) as chelating agent.

Aqueous composition according to any one of the preceding claims wherein (a) and (b) are present in weight ratio of from 1 :60,000 to 1 :5, preferably from 1 :400 to 1 :10.

Aqueous composition according to any one of the preceding claims, comprising from 0.0005 to 5 wt%, preferably from 0.05 to 2 wt%, more preferably from 0.1 to 1 wt% of component (a), based on the total weight of the composition.

Aqueous composition according to any one of the preceding claims, comprising from 5 to 30 wt%, preferably from 10 to 20 wt% of component (b), based on the total weight of the composition.

Composition according to any one of the preceding claims, wherein the component (a) consists for > 65% w/w, more preferably for > 75% w/w, and most preferably for > 85% w/w of molecules with two fatty acid units, two or more alkanolamine unit, and one or more diacid/acid anhydride units.

Composition according to any one of the preceding claims, wherein the product (a) has the formula

(IV)

wherein R¹, AO, x, R2, and R⁴ have the same meaning as in claim 1 ; R⁵ is a hydrocarbyl group, and X^" is an anion derived from the alkylating agent R⁵X; t is a number 0 or 1 ; and p is a number within the range 1 -15, and is on average at least 1.

9. Composition according to any one of the preceding claims, wherein:

R¹CO is an acyl group having 16 to 24 carbon atoms; and/or

R2 is an alkylene radical of formula -(CH₂)_Z- , wherein z is 4; and/or

x=1 ; and/or t=1 ; and/or

R⁵ is a C1 -C4 alkyl group or the benzyl group.

10. Composition according to any one of the preceding claims, wherein the product (a) is obtained by the process described in claim 1 , wherein the molar ratio between the fatty acid, or mixture of acids, of structure (I) and the alkanolamine

(III) in the reaction mixture is 1 :1.2 to 1 :10, and the molar ratio between the fatty acid, or mixture of acids, of structure (I) and the dicarboxylic acid or derivative (Ma) or (lib) is 2:1 to 1 :8.

1 1 . Composition according to any one of the claims 3 to 10 wherein p has a value of ≥ 3 in more than 50% by weight of the products (a).

12. Composition according to any one of the preceding claims, having a pH of from 3.5 to 13.

13. Composition according to any one of the preceding claims, further comprising a component (d) selected from the group of formic acid, potassium iodide, antimony chloride, copper iodide, sodium thiosulfate and 2-mercapto ethanol, preferably sodium thiosulfate.

14. Composition according to claim 13, comprising from 0.01 to 1 , preferably from 0.05 to 0.5, more preferably from 0.1 to 0.3 wt% of said component (d), preferably of sodium thiosulfate, based on the total weight of the composition. 15. Use of a composition according to any one of the claims 1 to 14, as a corrosion inhibitor, cleaning agent or descaling agent for metal surfaces, preferably for metal surfaces that are part of pipelines, pumps, tanks and other equipment used in oil- and gas fields or oil refineries

16. A method for protecting a metal surface from corrosion, for cleaning a metal surface or for descaling a metal surface by contacting the metal surface with a composition according to any one of the claims 1 -14.

17. A method according to claim 16, wherein said metal surface is a steel surface.

18. A method according to claim 16 or 17, wherein the temperature of said composition is at most 350, preferably at most 300, more preferably at most 250°F.

19. Method for treating a subterranean formation, preferably a carbonate formation, a sandstone formation or a shale formation, comprising introducing a composition according to any one of the claims 1 -14 into the formation.

20. Kit of parts wherein one part contains the composition of any one of claims 1 to 14 and the other part contains a fluid containing a mutual solvent and, optionally a surfactant, or wherein one part contains the composition of any one of claims 1 to 14 and in addition a surfactant, and the other part contains a fluid containing a mutual solvent.