NO20200842A1 - Biodegradable demulsifiers - Google Patents

Description

BIODEGRADABLE DEMULSIFIERS

BACKGROUND

[0001] This application claims the benefit of U.S. Provisional Application having Serial No.

62/620321 filed on January 22, 2018, the entire content being incorporated herein by reference in its entirety.

[0002] In the hydrocarbon drilling and production industry, crude oil refers to the desirable (and undesirable) hydrocarbon products extracted from the ground together with the associated aqueous phase and minor amounts of solids. Crude oils differ in their composition from deposit to deposit. In addition to water, the crude oil generally also comprises from 0.1 to 25% by weight of salts and solids. Water, salts and solids have to be removed before the crude oil can be transported and can be processed as crude oil in the refinery. The proportion of hydrocarbons in crude oils varies from 5% to almost 100%, and includes thousands of different molecules that may be grouped into four families of compounds: saturates, aromatics, resins and asphaltenes. Saturates generally constitute the lightest fraction of the crude oil while within the saturates family, C18+ long-chain linear paraffins represent the heavy fraction of the saturates and are responsible for wax deposit formation.

[0003] During its recovery, crude oil is produced as an emulsion with water. Most naturally occurring emulsions of crude oil and water take the form of water-in-oil emulsions in which the oil is a continuous phase and tiny drops of water are dispersed in the oil. Occasionally, however, oil-in-water emulsions are encountered either in the production, handling or refining of crude oil or fractions thereof. Unfortunately, in both types of emulsions, the emulsions are often extremely stable and will not resolve after standing for long periods. This is due to the fact that water which is comprised in the crude oil is emulsified in particular by natural emulsifiers, such as naphthenic acids, which reduce the interfacial tension between water phase and oil phase, stabilizing the emulsion. While such emulsions often occur naturally, such emulsions may also occur artificially resulting from one or more of numerous operations encountered in various industries. For example, such emulsions may be obtained from producing wells (as a result of enhanced oil recovery methods but much more generally than this) or from the bottom of crude oil storage tanks.

[0004] Before the crude oil is further processed, these crude oil emulsions may be broken into the oil fraction and the water fraction. The breaking of crude oil emulsion is carried out for economic and technical reasons, in order firstly to avoid the uneconomical transport of water, to prevent or to at least minimize corrosion problems, and in order to reduce the use of energy for the transport pumps. The breaking of the crude oil emulsion is thus a substantial process stage in crude oil production.

[0005] By adding emulsion breakers (demulsifiers), i.e. interface-active substances, which enter the oil-water interface and displace the natural emulsifiers there, coalescence of the emulsified water droplets can be achieved, which finally leads to phase separation. For this purpose, use is generally made of petroleum demulsifiers. Petroleum demulsifiers may be surface-active polymeric compounds which are able to affect the desired separation of the emulsion constituents within a short time. In addition, demulsifiers are increasingly desired which have good biodegradability and low bioaccumulation in order to replace the controversial products based on alkylphenol.

SUMMARY

[0006] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0007] In one aspect, embodiments disclosed herein relate to a method of breaking an emulsion, the method including contacting an emulsion with a demulsifier, where the demulsifier is a dendrimer functionalized with a carboxylic acid derivative and separating the emulsion into two distinct phases.

[0008] In another aspect, embodiments of the present disclosure relate to a method of producing crude oil, the method including extracting a hydrocarbon fluid from a subterranean formation; adding a demulsifier to the hydrocarbon fluid, where the demulsifier is a dendrimer functionalized with a carboxylic acid derivative and separating the crude oil emulsion into two distinct phases.

[0009] In yet another aspect, embodiments of the present disclosure relate to a composition that includes a demulsifier, where the demulsifier is a dendrimer functionalized with a polyoxyalkylene alkyl ether carboxylic acid having at least one oxyalkylene unit.

[0010] Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 is a representation of Boltorn H20.

[0012] FIG. 2 is a representation of Boltorn H30.

[0013] FIG. 3 is a representation of Boltorn H40.

[0014] FIG. 4 depicts OECD 306 biodegradation screening test results, according to the present embodiments.

[0015] FIG. 5 depicts the water drop (volume versus time) according to the present embodiments.

DETAILED DESCRIPTION

[0016] Generally, embodiments disclosed herein are directed to compositions and methods of using the same for treating hydrocarbon fluids. More specifically, embodiments disclosed herein are directed to compositions and methods of using the same for breaking crude oil emulsions. The inventors of the present disclosure have found that compositions that include dendrimers functionalized with a surfactant, such as a carboxylic acid derivative, may be used as demulsifiers in demulsifier packages. In addition, the functionalized dendrimers of the present disclosure may be used as demulsifiers in environmentally sensitive areas such as the North Sea, as they are environmentally acceptable, exhibiting low toxicity and high biodegradability compared to conventional demulsifiers which are poorly biodegradable.

[0017] While most of the terms used herein will be recognizable to those of skill in the art, the following definitions are nevertheless put forth to aid in the understanding of the present disclosure. It should be understood, however, that when not explicitly defined, terms should be interpreted as adopting a meaning presently accepted by those of skill in the art.

[0018] As used herein, the term “environmentally acceptable” is defined as chemicals or formulations that can pass the most stringent environmental testing criteria as described below. Furthermore, as used herein, the term “environmentally unacceptable” is defined as chemicals or formulations that do not pass the most stringent environmental testing criteria. Specifically, one measure of sample biodegradation is marine biodegradation data as outlined in Organization for Economic Cooperation and Development, Procedure OECD 306 or BODIS. Under OECD 306, the rules governing offshore chemical use set forth three tests: bioaccumulation, biodegradation and toxicity. In order for a chemical to be used without restriction offshore in the North Sea it must satisfy two of the following three criteria: (1) biodegradation is greater than 60%, if less than 20% it is automatically marked for substitution; (2) bioaccumulation as measured by octanol/water partitioning coefficient (log Po/w) is below 3 (or have a molecular weight >700); and (3) toxicity to the most sensitive marine species (often Skeletonema) is greater than LC50 or EC50 of 10 ppm. In order to comply with these constraints, components of the production chemical treatment fluid in some embodiments may be selected such that they meet the requirements for biodegradation and aquatic toxicity. At present (and for the last 30 years), the geographic location with the most stringent environmental and discharge testing criteria for well treatment operation is the North Sea, but the definition of either of these terms should in no way be limited to any past, present or future North Sea environmental testing criteria. Further, the test criteria also in no way limit the geographical region of use of the fluid, but provides an indication of the environmental friendliness of a product (or fluid containing a product).

[0019] As solutions are found useful to provide certain functions in treatment fluids, when used in the North Sea offshore, or other highly regulated offshore environments, stringent requirements for particular offshore environments are met. Any oilfield chemical that is used in the North Sea is compliant with the respective country’s environmental regulations which assign a rating or color classification to each chemical depending on its environmental and toxicological characteristics. Based on the chemical rating or color classification, the chemical will either be regarded as more or less environmentally acceptable. In the North Sea, the classification techniques vary. For example, Norway and Denmark follow color classification for chemical products, United Kingdom (UK) follows color and letter ratings for organic and inorganic chemical products, respectively, and Netherlands follows letter categories. Thus, countries within a small geographic region have customized their classification system based upon a desire to differentiate environmentally acceptable and unacceptable chemical products. Regardless of the classification system, each of the North Sea countries (Norway, Denmark, Netherlands and United Kingdom) employs the same three ecotoxicology test criteria, as described above, to differentiate chemical products.

[0020] When each component in a chemical product passes the above-mentioned criteria, then the whole product is rated as “Green” or PLONOR (Pose Little Or NO Risk) in Norway and Denmark. When one of the components meets two of the criteria, then the product can receive “Yellow” classification in Norway and Denmark, but it is still environmentally acceptable. If the biodegradation in seawater is <20% after 28 days for any of the components, then the chemical products receive “Red” classification or substitution warning ( i. e environmentally unacceptable classification in the North Sea). Table 1, below, summarizes the North Sea regulations. As a rule of thumb, two or more “Good” results means that the chemical compounds are acceptable, while two or more “Bad” results means that the chemical compound is unacceptable. However, a chemical compound having less than 20% biodegradation alone is unacceptable. Depending on the service performed, a well service operation may involve a large amount of chemicals, which means that the introduction of environmentally acceptable chemicals may be mandatory.

Table 1. North Sea Regulations Interpretation.

[0021] According to the present embodiments, the compositions as described herein may include a demulsifier, where the demulsifier may be a hyperbranched polymer having functional groups, such as a functionalized dendrimer. Particular dendrimers that may be used in embodiments of the present disclosure may be selected from the group of polyester polyols. According to the present embodiments, the molecular weight of such polyester polyols may be at least 1700. In one or more embodiments, the molecular weight of the polyester polyol may be at least 3500. It is also envisioned that polyester polyols with higher molecular weights may be used.

[0022] According to the present embodiments, the dendrimers as described herein may be functionalized with at least a surfactant. In one or more embodiments, the dendrimer may have at least one terminal hydroxyl group esterified by the surfactant. In such embodiments, the functionalized dendrimer may have a degree of functionalization of at least 50%. For example, in one or more embodiments, the degree of functionalization may be 70% or 90%. As described later in greater detail, the dendrimers of the present disclosure may include a branched dendritic core including a first quaternary carbon center bonded to four second carbon atoms, wherein each of the four second carbon atoms is bonded to a plurality of branched ligands to produce the branched dendritic core, wherein the branched dendritic core has greater than or equal to about 16 terminal hydroxyl groups, wherein at least one of the terminal hydroxyl groups is esterified with at least one carboxylic acid moiety comprising from 6 to 30 carbon atoms. It is also envisioned that a carboxylic acid moiety having a higher number of carbon atoms (such as 40 carbon atoms) may be used.

[0023] As noted above, the dendrimers as described herein may be functionalized with at least one surfactant. Suitable surfactants may include nonionic surfactants, cationic surfactants, and anionic surfactants. In the case of using anionic surfactants, such surfactants may contain anionic functional groups at their head, such as sulfate, sulfonate, phosphate and carboxylates. In one or more embodiments, the surfactants may be selected from the group of carboxylic acids and their derivatives. For example, particular surfactants that may be used are selected from the group of polyoxyalkylene alkyl ether carboxylic acids.

[0024] According to the present embodiments, the alkyl may be selected from the group of linear and branched alkyl groups. In one or more embodiments, the alkyl may be selected from the group of saturated alkyl groups or unsaturated alkyl groups, such as alkenyls. In such embodiments, the number of carbon atoms in the alkyl group may be at least 1. It is also envisioned that the alkyl group may have more than one carbon atom. For example, in one or more embodiments, the alkyl group may have at least 8 carbon atoms. In one or more embodiments, the number of carbon atoms present in the alkyl group may range from about 8 to about 18. It is also envisioned that the alkyl group may have up to 24 carbon atoms. In yet another embodiment, the number of carbon atoms present in the alkyl group may be higher than 24.

[0025] As previously discussed, the carboxylic acid derivative may contain polyoxyalkylene units. According to the present embodiments, the oxyalkylene units present on the carboxylic acid derivative may range from 1 to 10, or from 1 to 15. It is also envisioned that the number of oxyalkylene units present on the carboxylic acid derivative may be even higher than 15. In one or more embodiments, the oxyalkylene units are selected from the group of oxyethylene, oxypropylene, oxybutylene and combinations of thereof. For example, the carboxylic acid derivative may include oxyethylene units. It is also envisioned that the carboxylic acid derivative may include combinations of oxyalkylene units, such as for example, oxyethylene and oxypropylene units, or oxyethylene and oxybutylene units. However, other combinations are envisioned as well.

[0026] In embodiments where the alkylene group in the oxyalkylene unit is ethylene, the polyoxyethylene alkyl ether carboxylic acids have the following general formula:

where R is an alkyl group and n is the number of oxyethylene units, or the degree of polymerization. As previously discussed, R may be selected from the group of linear, branched, saturated or unsaturated alkyl groups. In such embodiments, R may have at least one carbon atom. It is also envisioned that R may have a higher number of carbon atoms. For example, in one or more embodiments, R may have at least 8 carbon atoms. In yet another embodiment, R may have up to 24 carbon atoms. It is also envisioned that R may contain even more than 24 carbon atoms. Examples of polyoxyethylene alkyl ether carboxylic acids will be presented later in greater detail.

[0027] Dendrimers

[0028] Dendrimers are three-dimensional highly-ordered oligomers or polymers. They are obtainable by reiterative reaction sequences starting from an initiator core having one or more reactive sites. To each reactive site is attached one functional group of a polyfunctional reactant. The reactant is then caused to react through its remaining functional group or groups with additional molecules either the same as the original core if it is polyfunctional or a different, polyfunctional, molecule or molecules, and so on, in each case under reaction conditions such that unwanted side reactions, for example, crosslinking, are avoided. In this way, a dendritic body is built up around the central core, each reiterative reaction sequence adding further reactants (or ‘units’) to the ends of the dendrites. For example, polyamidoamine (PAMAM) dendrimers may be made based on ammonia as a core, which is caused to react by Michael addition with methyl acrylate (Stage A). The carboxyl group of the acrylate molecule is caused to react with one amino group of ethylene diamine (Stage B). The resulting triamine core cell is referred to as Generation 0; a further repetition of stages A and B provides a hexamine, referred to as Generation 1. Further repetitions of stages A and B produce higher generations which after Generation 4 result in concentric spheres of cells, the outermost sphere carrying external reactive groups. Other dendrimers may include, but are not limited to, polyethylenimine, hydrocarbon, polyether, polythioether, polyamide, polyamido-alcohol and polyarylamine dendrimers.

[0029] In an embodiment, branched, hyperbran ched, and/or dendritic macromolecules (i.e., dendrimers) suitable for use herein may generally be described as three dimensional highly branched (i.e., hyperbranched) molecules having a tree-like structure. Suitable branched dendrimers may be highly symmetric, while similar macromolecules designated as branched, may, to a certain degree, hold an asymmetry, yet maintaining a highly branched tree-like structure. Dendrimers can be said to be monodispersed variations of branched macromolecules.

[0030] In an embodiment, branched dendrimers suitable for use herein comprise an initiator or nucleus having one or more reactive sites and a number of surrounding branching layers and optionally a layer of chain terminating molecules. As is known in the art, the layers are called generations, a designation hereinafter used. Branched dendritic or near dendritic macromolecules, also referred herein as a branched dendritic core, may have three or more generations. Embodiments of the branched dendritic core may be illustrated by Formulae (II) and (ΙII),

where X is a first quaternary carbon center bonded to four second carbon atoms Y, where each of the four second carbon atoms Y is each bonded through one or more chain extender ligands, which may be linear or branched, to produce the branched dendritic core.

[0031] In an embodiment, A and B are chain extender ligands having two or four reactive sites each. Suitable examples may include poly functional ligands comprising hydroxyl groups, epoxides, carboxylic acids, and the like.

[0032] In an embodiment, each of the chain extender forms one generation in the branched dendritic core. As shown above, A and/or B may include a plurality of chain extenders, linked together, each providing a branching point which is eventually terminated by a T functional group. Each of the A and B chain extenders may be the same or different.

[0033] In an embodiment, the branched dendrimer core, including the branches and terminating chains, does not include nitrogen atoms. In an embodiment, the branched dendrimer core, including the branches and terminating chains, may include carbon, hydrogen and oxygen. In yet another embodiment, A and B may be carbon, hydrogen and/or oxygen. As disclosed above, T is a terminating chain stopper forming the last generation. T may either be monofunctional or give a suitable terminal functionality. In an embodiment, T may be selected from at least one of a hydroxyl, carboxyl or epoxide group. Each T may be a terminal hydroxyl group or a terminal hydroxyl group esterified with at least one carboxylic acid moiety having from 6 to 30 carbon atoms. As noted above, it is also envisioned that a carboxylic acid moiety having a higher number of carbon atoms (such as for example 40 carbon atoms) may be used. The branched dendritic core may have greater than or equal to about 16 terminal hydroxyl groups, wherein at least one of the terminal hydroxyl groups is esterified with at least one carboxylic acid moiety comprising from 6 to 30 carbon atoms, or even a higher number of carbon atoms, such as for example 40 carbon atoms

[0034] In one or more embodiments, the branched dendritic core may be represented by Formula IV below.

[0035] In an embodiment, the Formula IV branched dendritic core may not include nitrogen functionality, and more specifically may not include amine or amide functionality. Each R may be a hydrogen ( i. e a hydroxyl terminal group) or an esterified hydroxyl group which has been esterified with at least one carboxylic acid moiety selected from the group including: greater than or equal to about 6 carbon atoms, greater than or equal to about 10 carbon atoms, and from 6 to 40 carbon atoms, with from 6 to 30 carbon atoms. Embodiments of R may include — COO — (CH2)X — (CH)y — CHZ, wherein x+y=8-28, wherein y is from 0 to 5, and wherein z is 1, 2, or 3.

[0036] In one or more embodiments, prior to being esterified with the carboxylic acid, the branched dendritic core has a hydroxyl number of greater than or equal to about 490 mg KOH/g, wherein the hydroxyl number represents the hydroxyl content of a dendritic core, and is derived by acetylating the hydroxyl and titrating the resultant acid against KOH, as is known in the art. The hydroxyl number is thus the weight of KOH in milligrams that will neutralize the acid from 1 gram of the dendritic core prior to being esterified with a carboxylic acid.

[0037] In one or more embodiments, the branched dendritic core may include at least one carboxylic acid derivative moiety having from 6 to 30 carbon atoms, or from 8 to 24 carbon atoms, or from 6 to 40 carbon atoms, where the terminal hydroxyl groups of the branched dendritic core are each esterified with at least one carboxylic acid derivative moiety having from at least 8 carbon atoms. In yet another embodiment, the terminal hydroxyl groups on the branched dendritic core may be esterified with a corresponding number of the same carboxylic acid derivative moiety. The carboxylic derivative moiety may be individually selected from a polyoxyalkylene alkyl ether carboxylic acid moiety having six to 30 carbon atoms or more. In one or more embodiments, the polyoxyalkylene alkyl ether carboxylic acid moiety may have from 8 to 30 carbon atoms, or from 8 to 24 carbon atoms. As previously discussed, the oxyalkylene unit may be selected from the group of oxyethylene, oxypropylene, oxybutylene and combinations thereof. In such embodiments, the alkyl group may be selected from the group of linear, branched, saturated and unsaturated alkyl groups, where the unsaturated alkyl is an alkenyl group.

[0038] According to the present embodiments, the branched dendritic core may include terminal carboxylic acid derivative moieties selected from the group of polyoxyalkylene alkyl ether carboxylic acids having six to 30 carbon atoms, or six to 40 carbon atoms, or 8 to 24 carbon atoms, or having 12, 14, 16, 18, 20, 22 and 24 carbon atoms, and combinations thereof. Accordingly, the term “branched dendritic core” as used herein refers to a branched dendritic core wherein at least one of the terminal hydroxyl groups is esterified with at least one polyoxyalkylene alkyl ether carboxylic acid moiety including from 6 to 30 carbon atoms, or from 6 to 40 carbon atoms, or from 8 to 24 carbon atoms.

[0039] In one or more embodiments, the carboxylic acid moiety is a substituted carboxylic acid moiety which is substituted with at least one functional group including elements from one or more of Groups 13-17 of the periodic table of the elements. In yet another embodiment, the carboxylic acid moiety is a substituted carboxylic acid moiety which is substituted with at least one functional group including elements from one or more of Group 13, 14, 16, or 17 of the periodic table of the elements. In an embodiment, the at least one functional group may include carbon, hydrogen, oxygen, sulfur and/or a halogen. In one or more embodiments, the substituted carboxylic acid moiety may include a hydroxyl functional group, a halogen functional group, or a combination thereof. For example, in one or more embodiments, the substituted carboxylic acid moiety may be a hydroxy substituted carboxylic acid. In such an embodiment, the substituted carboxylic acid moiety is 12 hydroxy stearic acid.

[0040] Commercially available branched dendritic cores prior to esterification, which are suitable for use herein may include polyols sold by Perstorp AB Corporation Sweden under the name Boltorn®, (Perstorp, Sweden), including Boltorn® H20 (See FIG. 1), Boltorn® H30 (see FIG. 2), Boltorn® H40 (see FIG. 3), and the like.

[0041] Surfactants

[0042] As previously discussed, the dendrimers of the present disclosure are functionalized with carboxylic acid derivatives. Tables 2 and 3 presented below show examples of polyoxyethylene alkyl ether carboxylic acids. However, the embodiments of the present disclosure should not be limited to such examples.

Table 2. Physical appearance of polyoxyethylene alkyl ether carboxylic acids.

Table 3. Examples of polyoxyethylene alkyl ether carboxylic acids.

[0043] It is also envisioned that the carboxylic acid derivatives used for the functionalization of the dendrimers as disclosed herein may be selected from the group of alkyl-(aryl) alkoxylated carboxylic acids. Table 4 below presents examples of such acids. However, the embodiments of the present disclosure should not be limited to such examples.

Table 4. Examples of alkyl-(aryl-) alkoxylated carboxylic acids.

[0044] Upon mixing, the compositions of the present embodiments may be used as demulsifiers in breaking emulsions. Such operations are known to persons skilled in the art and involve adding a functionalized dendrimer to a water-in oil or an oil-in-water emulsion. In the breaking of emulsions, the polymer solutions may be added to crude oils, i.e. in the oil field during oil production and processing. In such embodiments, the crude oil emulsion may comprise oil and water or oil and salt water. The breaking takes place at a temperature as low as that of the freshly conveyed crude oil emulsion at a speed such that the emulsion can be broken on the way to the processing plant. This broken emulsion is then separated into pure oil and water or salt water in an optionally heated separator and possibly with the aid of an electric field.

[0045] According to embodiments of the present disclosure, the demulsifiers are added as a formulation. Commonly used solvents for demulsifiers are mutual solvents/glycols such as for example ethylene glycol monobutyl ether. The temperature at which the formulation is dosed may vary. Demulsifier testing may be designed to follow the temperature in the oil production process. The dosage rate of demulsifier formulations may vary, depending on the system, the temperatures and the crude oil/water emulsion. For example, in one or more embodiments, the dosage rate of demulsifier formulations for a normal light crude oil may range from 2 to 20 ppm.

In one or more embodiments, the dosage rate of the demulsifier formulation for a medium crude oil may range from 10 to 100 ppm. In the case of heavy crude oils, the dosage rate of the demulsifier formulation may range from 80 to 200 ppm. It yet another embodiment, the dosage rate of the demulsifier formulation used for extra heavy crude oils may be up to 500 ppm. It is also envisioned that in all the above-mentioned embodiments, the dosage rate of the demulsifier formulation may be higher, such as three times higher. According to one or more embodiments, the active concentration of the demulsifier in the formulation may range from 30% to 50%, where the lower limit can be any of 30%, 32%, or 35% and the upper limit can be any of 45%, 48% or 50% where any lower limit can be used with any upper limit. However, it is envisioned that other concentrations may be used.

[0046] The demulsifiers as described herein may be used for water-in-oil or oil-in-water emulsions comprising in general from 0.1 to 99% by weight of water or salt water. Suitable oils which can be dewatered in this manner are crude oil emulsions of any origin.

[0047] One embodiment of the present disclosure includes a method of breaking an emulsion, such as for example a crude oil emulsion. In such an illustrative embodiment, the method involves contacting an emulsion with a demulsifier and separating the emulsion into two distinct phases. As previously discussed, the demulsifier is a dendrimer functionalized with a carboxylic acid derivative, where the degree of functionalization of the functionalized dendrimer may be at least 50%. It is also envisioned that a functionalized dendrimer having a degree of functionalization higher than 50% may be used as well. For example, in one or more embodiments, the degree of functionalization may be at least 70%. In yet another embodiment, the degree of functionalization may be 90%. In such embodiments, the dendrimer is a polyester polyol that has at least one terminal hydroxyl group esterified by the carboxylic acid derivative. According to the present embodiments, the dendrimer may be functionalized with a polyoxyalkylene alkyl ether carboxylic acid. For example, in one or more embodiments, the dendrimer may be functionalized with a polyoxyalkylene alkyl ether carboxylic acid, where the oxyalkylene units are selected from the group of oxyethylene, oxypropylene, oxybutylene and combinations thereof. In such embodiments, the alkyl group may have at least one carbon atoms. It is also envisioned that the alkyl group may have more than one carbon atom. For example, in one or more embodiments, the alkyl group may have at least 8 carbon atoms and up to 24 carbon atoms. It is also envisioned that the dendrimer may be functionalized with an alkyl-(aryl) alkoxylated carboxylic acid.

[0048] One or more embodiments of the present disclosure involve a method of producing crude oil. In one such an illustrative embodiment, the method involves extracting a hydrocarbon fluid from a subterranean formation by means of a well, adding a demulsifier according to any one or combination of embodiments disclosed herein to the hydrocarbon fluid and separating the crude oil emulsion into two distinct phases. In such embodiments, the dendrimer functionalized with a carboxylic acid derivative is added to the hydrocarbon fluid after the hydrocarbon fluid is extracted from the well. According to the present embodiments, the hydrocarbon fluid is a hydrocarbon fluid produced during extraction of hydrocarbons from a well, crude oil, a crude oil condensate, a middle distillate, a fuel oil, diesel, or a combination thereof. Also included are refined streams including various fuel oils, diesel fuel, kerosene, gasoline, and the like.

[0049] In one or more embodiments, the well is located underwater. In yet another embodiment, the demulsifier may be added to a hydrocarbon fluid produced from a well at the well head or at the surface. Generally, demulsifiers are used topside, but they may also be added at the wellhead or subsea. They are generally added prior to the separators to ensure that water separates from the hydrocarbon fluids in a good location. It is also envisioned that the demulsifier may be added to a hydrocarbon fluid prior to transporting the hydrocarbon fluid in a pipeline or a tank.

[0050] As noted above, the dendrimers as described herein may be functionalized with a polyoxyalkylene alkyl ether carboxylic acid. In yet another embodiment, the dendrimer may be functionalized with an alkyl-(aryl) alkoxylated carboxylic acid.

[0051] RSN test

[0052] The superior performance of the formulations of this disclosure was determined by conducting the Relative Solubility Number (RSN) test as described below. The RSN number of a demulsifier is a measure of its solubility properties (such as the solubility hydrophilelyophile balance of surfactants). The RSN is a factor in the demulsifier selection since solubility properties dictate whether the chemical will be capable of working effectively as a surface-active agent at the water/oil interface. The RSN is an industrially accepted measurement used to describe the hydrophile-lyophile balance of oilfield demulsifiers. It is a simple measure of water solubility and relates to a water/oil partition coefficient. As such, it is ordinal and gives a relative measure of one product against another. The test was conducted using a solution of dimethylisosorbide (75%), butyl diglycol (20%) and xylene (5%). The RSN method as described herein may be applicable to all common types of demulsifier surfactant molecules.

[0053] According to the RSN number test, a solvent-stripped demulsifier sample is dissolved in the above mixture of solvents. The resultant solution is titrated against demineralised water until a persistent turbidity is produced. The volume of water (in millilitres) used to reach this end point is recorded as the RSN.

[0054] OECD 306: Biodegradability in Seawater

[0055] This Test Guideline describes two methods for biodegradability in seawater. The shake flask method involves dissolution of a pre-determined amount of the test substance in the test medium to yield a specific concentration of dissolved organic carbon (DOC). The solution of the test substance in the test medium is incubated, under agitation in the dark or in diffuse light under aerobic conditions, at a fixed temperature (such as 15-20°C). The recommended maximum test duration is about 60 days. Degradation is followed by DOC measurements (ultimate degradation) and, in some cases, by specific analysis (primary degradation). The closed bottle method involves dissolution of a pre-determined amount of the test substance in the test medium in a specific concentration. The solution is kept in a filled closed bottle in the dark in a constant temperature bath or enclosure controlled within a range of 15-20°C. The degradation is followed by oxygen analyses over a 28-day period or longer if the blank biological oxygen demand value remains within the 30% limit. Determinations of dissolved oxygen are performed using a chemical or electrochemical method.

[0056] EXAMPLES

[0057] The following examples are presented to further illustrate the properties of the demulsifiers in accordance with the present disclosure, and should not be construed to limit the scope of the disclosure, unless otherwise expressly indicated in the appended claims.

[0058] Two hyperbranched dendrimers were functionalized by an esterification reaction with the formation of functionalized dendrimers, namely sample 1 and sample 2. The synthesis was completed using the reaction carousel in the presence of xylene as a solvent. The desired dendrimer and the corresponding polyoxyalkylene alkyl ether carboxylic acid were mixed with 100 mL of solvent. A dodecylbenzenesulphonic acid (DDBSA) was used as a catalyst to promote the esterification. It is also envisioned that other acid catalysts may be used.

[0059] Afterwards, the mixture was heated up to 180°C with mechanical stirring. A Dean Stark apparatus was used to collect water produced during the esterification reaction. The reaction was monitored by the amount of water produced. All reactions were stopped after 7 hours and 30 minutes under reflux. The solvent was afterwards removed using a rotary evaporator. Table 5 below shows the yield of the esterification reactions, as well as the amount of water produced.

[0060] However, it is also envisioned that the synthesis may be carried in the absence of a solvent. For example, in one embodiment, the desired dendrimer, polyoxyalkylene alkyl ether carboxylic acid and catalyst (such as DDBSA, a sulphonic acid catalyst) were mixed. Afterwards, the mixture was heated to 150°C under vacuum. Water was removed by distillation during the esterification reaction. The reaction was monitored by the amount of water produced and acid number.

Table 5. Formulations of functionalized dendrimers and yield of the functionalization reactions.

[0061] To fully assess the properties of the two functionalized dendrimers, their physical properties, such as appearance, odor, density, flashpoint and solubility were determined. Table 6 below shows the results of the physical characterization of the two formulations.

Table 6. Physical properties of functionalized dendrimers.

where EGMBE is ethylene glycol mono butyl ether.

[0062] HSE

[0063] The environmental authorities regulate discharge of production chemicals with a yellow or green category to sea. The classification scheme is based on aquatic biodegradation, toxicity and bioaccumulation tests. Red category products, as for instance several products in production chemicals, are not allowed to discharge and will need to be shipped onshore for cuttings waste treatment.

[0064] Screening tests performed on the two functionalized dendrimers have demonstrated a biodegradation over 40% in the OECD 306 test, as shown in Table 7 and FIG. 4. Screening of the toxicity to the Skeletonema has also been performed. The screening test shows that sample 1 has a toxicity between 33 and 103 mg/L, while sample 2 has a toxicity between 3.2 and 10 mg/L. A preliminary classification indicates that sample 1 falls in the yellow category (Y2), while sample 2 falls in the red category.

Table 7. Ecotox results testing of functionalized dendrimers.

[0065] The demulsifier testing was performed using the bottle test procedure. Table 8 below presents the experimental results. This procedure was performed as following:

1. A sample of crude oil was heated to 70 C overnight prior to testing.

2. The water cut (the ratio of water produced compared to the volume of the total liquids produced) and emulsions was determined by using Hot Spin centrifuge. The crude oil sample contained zero water and emulsion according to the test.

3. The synthetic water used was 3% sodium chloride brine which was preheated to 70 C.

4. The emulsion was prepared by adding 20 vol% synthetic water and crude oil. The mixture was kept at 40°C in a water bath. Ultra turrax mixing at 24,000 rpm for 7 minutes gave a stable emulsion (>1 hour).

5. The bottles were heated to 40°C, and the demulsifier was injected to each bottle, except for the blank.

6. The bottles were placed in a water bath at 40°C, and then they were shaken for 1 minute.

7. The tubes were observed and the total amounts of water separated after set time periods were recorded. The color and brightness of the top oil, volume and quality of interface emulsion and water quality were recorded. Photos were taken after certain period of time (not shown). Table 9 presents a summary of the visualization observation.

8. Water drop, middle cut (level 50%) were performed on the test bottles. As defined herein, water drop is the amount of water/brine separated from the crude oil and/or emulsion, while the middle cut represents the level that a sample is taken above the interface to see how much residual water/emulsion is left in the crude oil. In other words, middle cut indicates how dry is the crude oil. A hotspin centrifuge was used to identify the residual emulsion.

9. Chemicals used during bottle tests: commercial demulsifier; Dosage rate: 50, 100, 200 ppm (5, 10, 20 μΐ); Sample 1/2; Formulated 20% in EGMBE; Dosage rate: 100 ppm (10 μΐ). Grind out, which looks at the residual water and or solids left in the oil, happens at end of monitored water drop. In this example after 30 minutes.

Table 8. Bottle test results performed at 40°C and 20% water cut (WC).

Where BS=basic sediments, W=water, Tot w%=BS+W, WQ=Water quality: Cl = clear, H= hazy, O = oily, /- = better or worse; IF = Inter phase: S = Sharp, F = Fair, B = baggy, R = raggy, V = very Table 9. Summary of the visualization observation.

[0066] The results as depicted in FIG. 5 show the comparison of a commercial dendrimer (“dendrimer”) and new demulsifier samples, namely sample 1 and sample 2 at the same dosage of 100 ppm. The commercial dendrimer is a finished product with at least 3 different active components developed for North Sea market to meet the environmental requirements. It is normal for demulsifier formulations to have multiple components, as different chemistries work to separate the oil and water, clean the interface, and give both dry oil and clean water. Both sample 1 and sample 2 are single components and match the performance of commercial products, i.e. fast water drop, good interface and good water quality and dry crude.

[0067] Advantageously, embodiments of the present disclosure may provide biodegradable demulsifier compositions and methods for using the same. The use of dendrimers functionalized with a carboxylic acid derivative may allow for breaking emulsions, in particular in the production of crude oil. As described above, dendrimers functionalized with a carboxylic acid derivative are environmentally acceptable, exhibiting low toxicity and high biodegradability for potential applications in the North Sea.

[0068] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

Claims (21)

CLAIMS What is claimed:

1. A method of breaking an emulsion, the method comprising:

contacting an emulsion with a demulsifier, wherein the demulsifier is a dendrimer functionalized with a carboxylic acid derivative; and

separating the emulsion into two distinct phases.

2. The method of claim 1, wherein the dendrimer is selected from the group of polyester polyols.

3. The method of claim 1, wherein the functionalized dendrimer has a degree of functionalization of at least 50%.

4. The method of claim 1, wherein the functionalized dendrimer has at least one terminal hydroxyl group esterified by the carboxylic acid derivative.

5. The method of claim 1, wherein the carboxylic acid derivative is selected from the group of polyoxyalkylene alkyl ether carboxylic acids.

6. The method of claim 5, wherein the alkyl has up to 24 carbon atoms.

7. The method of claim 6, wherein the alkyl is selected from the group of linear, branched, saturated and unsaturated alkyl groups.

8. The method of claim 5, wherein the polyoxyalkylene alkyl ether carboxylic acids have at least one oxyalkylene unit.

9. The method of claim 8, wherein the oxyalkylene units are selected from the group of oxyethylene, oxypropylene, oxybutylene and combinations of thereof.

10. A method of producing crude oil, the method comprising:

extracting a hydrocarbon fluid from a subterranean formation;

adding a demulsifier to the hydrocarbon fluid, wherein the demulsifier is a dendrimer functionalized with a carboxylic acid derivative; and

separating the crude oil emulsion into two distinct phases.

11. The method of claim 10, wherein the demulsifier is added to the hydrocarbon fluid after the hydrocarbon fluid is extracted from the well.

12. The method of claim 10, wherein the hydrocarbon fluid is a hydrocarbon fluid produced during extraction of hydrocarbons from a well, crude oil, a crude oil condensate or a combination thereof.

13. The method of claim 10, wherein the dendrimer is selected from the group of polyester polyols.

14. The method of claim 10, wherein the functionalized dendrimer has a degree of functionalization of at least 50%.

15. The method of claim 10, wherein the functionalized dendrimer has at least one terminal hydroxyl group esterified by the carboxylic acid derivative.

16. The method of claim 10, wherein the carboxylic acid derivative is selected from the group of polyoxyalkylene alkyl ether carboxylic acids.

17. The method of claim 16, wherein the alkyl has up to 24 carbon atoms.

18. The method of claim 17, wherein the alkyl is selected from the group of linear, branched, saturated and unsaturated alkyl groups.

19. The method of claim 16, wherein the polyoxyalkylene alkyl ether carboxylic acids have at least one oxyalkylene unit.

20. The method of claim 19, wherein the oxyalkylene units are selected from the group of oxyethylene, oxypropylene, oxybutylene and combinations of thereof.

21. A composition comprising:

a demulsifier, wherein the demulsifier is a dendrimer functionalized with a polyoxyalkylene alkyl ether carboxylic acid having at least one oxyalkylene unit.