Composite emulsifier and oil-based drilling fluid

Abstract

The invention relates to the technical field of emulsifiers, and discloses a composite emulsifier and an oil-based drilling fluid, the composite emulsifier contains a main emulsifier and an auxiliary emulsifier, and the auxiliary emulsifier is a sulfonated product and / or a carboxylated product of the main emulsifier. The composite emulsifier provided by the invention has an excellent emulsifying effect and good electrical stability and thermal stability, and can greatly reduce the difficulty of compounding on a drilling site.

Description

Composite emulsifier and oil-based drilling fluid

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202310477151.5 filed on April 27, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The invention relates to the technical field of oil-based drilling fluid emulsifiers, in particular to a composite emulsifier and oil-based drilling fluid. Background Art

[0004] Oil-based drilling fluids offer excellent properties such as strong inhibition, pollution resistance, lubrication, salt resistance, and minimal reservoir damage. They are increasingly used in water-sensitive formations, shale formations, deep wells, thick salt-gypsum layers, and salt rock formations. Emulsifiers are one of the most critical treatment agents for oil-based drilling fluids, primarily used to ensure the emulsion stability of water-in-oil drilling fluids and thereby improve their rheological properties. Currently, the emulsifier composition of oil-based drilling fluids mostly consists of a primary emulsifier and a secondary emulsifier, based on surfactants of varying structures and hydrophilicity. However, when surfactants of varying structures form an interfacial film, their dissimilarities lead to poor integration, hindering the emulsion's strength and stability. Furthermore, the presence of primary and secondary emulsifiers can increase the difficulty of field operations.

[0005] CN115785920A discloses an emulsifier for oil-in-water emulsified drilling fluid. The emulsifier is obtained by cyclizing fatty acids and organic amines as reactive monomers. The five-membered heterocyclic ring structure in the emulsifier's molecular structure ensures its stability in high-temperature environments. However, the emulsifier's demulsification voltage is below 400 V. CN105907382A discloses an emulsifier for oil-based drilling fluid. The emulsifier includes tall oil fatty acid, a polyamine, chloroacetamide, a surfactant, and an organic solvent. The emulsifier is compounded by adding a surfactant. However, only the temperature resistance of the emulsifier after aging at 150°C is disclosed.

[0006] Therefore, how to reduce the difficulty of on-site operations and improve the electrical stability and temperature resistance of the oil-water emulsion system of oil-based drilling fluid is a technical problem that needs to be solved urgently.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to overcome the problems of poor stability and high difficulty in on-site operation of the oil-water emulsion system in the prior art, and to provide a composite emulsifier and an oil-based drilling fluid. The composite emulsifier has excellent emulsifying properties, good stability, and low difficulty in preparation and operation.

[0009] In order to achieve the above object, the present invention provides a composite emulsifier in a first aspect. The composite emulsifier comprises a primary emulsifier and an auxiliary emulsifier, wherein the auxiliary emulsifier is a sulfonated and / or carboxylated product of the primary emulsifier.

[0010] A second aspect of the present invention provides an oil-based drilling fluid, which comprises a base oil and a treatment agent, wherein the treatment agent comprises the composite emulsifier described in the first aspect.

[0011] The emulsifier component of oil-based drilling fluid is mostly composed of a primary emulsifier and a secondary emulsifier, the primary emulsifier has a certain lipophilicity, and the secondary emulsifier has a certain hydrophilicity, but the conventional primary emulsifier and secondary emulsifier are provided by surfactants of different structures, and the on-site compounding difficulty is large, and the stability of the emulsification system is poor. In the composite emulsifier provided by the present invention, the secondary emulsifier is a sulfonated product and / or carboxylated product of the primary emulsifier, which can be directly used in the drilling fluid, greatly reducing the difficulty of compounding on the drilling site. In the present invention, by the synergistic effect of the primary emulsifier and the secondary emulsifier, the oil-water interfacial tension can be effectively reduced to form a stable oil-water emulsion system. The composite emulsifier is used in oil-based drilling fluid, and the demulsification voltage can reach more than 674V, while ensuring a lower high-temperature and high-pressure filtration loss, and can be applicable to the emulsification of different oil-based drilling fluids such as gas oil, white oil, and diesel. In addition, the composite emulsifier provided by the present invention can maintain an emulsion breaking voltage of 518V and 432V after aging at 180°C and 200°C, respectively, and has excellent electrical stability and thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is an infrared absorption spectrum of the primary emulsifier prepared in Example 1 of the present invention;

[0013] FIG2 is a mass spectrum of the primary emulsifier prepared in Example 1 of the present invention;

[0014] FIG3 is an infrared absorption spectrum of the composite emulsifier A1 prepared in Example 1 of the present invention;

[0015] FIG4 is a mass spectrum of the composite emulsifier A1 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0016] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0017] In a first aspect, the present invention provides a composite emulsifier comprising a primary emulsifier and an auxiliary emulsifier, wherein the auxiliary emulsifier is a sulfonated product and / or a carboxylated product of the primary emulsifier.

[0018] In the composite emulsifier provided by the present invention, the auxiliary emulsifier is a sulfonated product and / or carboxylated product of the main emulsifier, which can be directly used in drilling fluid, greatly reducing the difficulty of compounding at the drilling site. The main emulsifier and the auxiliary emulsifier in the composite emulsifier provided by the present invention have good fusion properties, can significantly enhance the emulsification effect, and the demulsification voltage can reach more than 674V. The demulsification voltage after aging at 180°C and 200°C can also be maintained at more than 518V and 432V, with excellent electrical stability and thermal stability. In the prior art, when surfactants based on different structures and hydrophilicity are used as emulsifiers, due to the different structures of different surfactants, fusion is difficult, and the stability is poor. Generally, it is necessary to assemble them during on-site operation, which increases the difficulty of on-site operation.

[0019] According to the present invention, preferably, when added at a dosage of 5 wt%, the composite emulsifier has an emulsion breaking voltage of 50-400 V, preferably 80-280 V, and more preferably 200-280 V in a standard oil-based emulsion, wherein the standard oil-based emulsion is composed of No. 5 white oil and a 25 wt% CaCl2 aqueous solution, with an oil-to-water volume ratio of 80:20. The dosage refers to the mass fraction of the emulsifier added based on the total mass of the oil and water. The inventors of the present invention have discovered that the composite emulsifier has an appropriate emulsion breaking voltage in the standard oil-based emulsion. Within the above preferred range, the emulsifier is advantageously used in actual oil-based drilling fluids and exhibits superior emulsification properties. The higher the demulsification voltage of the emulsifier in the standard oil-based emulsion, the better. Due to the complex composition of the actual drilling fluid, when the demulsification voltage of the emulsifier in the standard oil-based emulsion is too high, the emulsifier will show too high polarity in the actual oil-based drilling fluid, and the oil droplets formed will be too fine, which may lead to increased plastic viscosity and dynamic shear force, and poor electrical stability and thermal stability.

[0020] According to some preferred embodiments of the present invention, the emulsification rate of the composite emulsifier in the standard oil-based emulsion is ≥90%, preferably 95-100%.

[0021] According to the present invention, preferably, in the composite emulsifier, the molar ratio of the auxiliary emulsifier to the primary emulsifier is (0.25-1):1, and preferably, the molar ratio of the preferred auxiliary emulsifier to the primary emulsifier is (0.4-0.8):1. Within the above preferred composition range, the synergistic effect of the primary emulsifier and the auxiliary emulsifier is further exerted, thereby improving the stability of the oil-water emulsion system.

[0022] In the present invention, "the auxiliary emulsifier is a sulfonated product and / or carboxylated product of the main emulsifier" refers to the introduction of sulfonic acid groups and / or carboxylic acid groups into the main emulsifier through a sulfonation reaction or a carboxylation reaction. The specific method of the reaction is well known to those skilled in the art.

[0023] According to the present invention, preferably, in 1 mol of the composite emulsifier, the total molar amount of the sulfonic acid group and / or the carboxylic acid group is 0.1-1.2 mol, preferably 0.3-0.6 mol, for example, it can be 0.3 mol, 0.35 mol, 0.4 mol, 0.45 mol, 0.5 mol, 0.55 mol, 0.6 mol or the like typical but non-limiting molar amounts or any range therebetween. In the present invention, the molar amount of the sulfonic acid group is The molar amount of carboxylic acid groups is calculated as wherein M is an alkali metal or ammonium group introduced in the sulfonation or carboxylation reaction, which is well known to those skilled in the art, and may be, for example, Na, K or ammonium.

[0024] In the present invention, an organic element analyzer is used to test the elemental composition of the primary emulsifier and the composite emulsifier, and then the content of the sulfonic acid group and / or carboxylic acid group in the auxiliary emulsifier is calculated based on the change in the molar amount of the S / C element.

[0025] In the present invention, there is no particular limitation on the structure of the primary emulsifier, and conventional lipophilic primary emulsifiers in the art can be used. Preferably, the primary emulsifier includes an N-containing skeleton and a hydrophobic group connected to the N-containing skeleton. It is understood that the H atom connected to at least one N atom in the N-containing skeleton is replaced by a hydrophobic group, so that the hydrophobic group is connected to the N-containing skeleton through a covalent bond. The present invention has a wide range of choices for the N-containing skeleton. Preferably, the N-containing skeleton can be provided by an amine compound, which contains at least two amino groups, for example, at least one of a chain or cyclic diamine, triamine, tetramine and pentamine. More preferably, the amine compound is selected from at least one of substituted or unsubstituted piperazine, ethylenediamine, propylenediamine, butylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine. The substituents in the above compounds can be, for example, C1-C5 alkyl or alkylamino groups.

[0026] In the case of an N-containing skeleton containing at least two amino groups, the hydrophobic group is preferably connected to the N atom at the end of the N-containing skeleton. In the above preferred case, the hydrophobic groups are concentrated on the outside of the compound structure and synergistically act with the internal hydrophilic N-containing skeleton, which is conducive to further improving the emulsification effect of the composite emulsifier and improving the electrical stability and thermal stability of the emulsification system.

[0027] According to the present invention, preferably, based on the total amount of the composite emulsifier, the content of the N-containing skeleton is 5-12 wt%, preferably 7-10 wt%.

[0028] In the present invention, hydrophobic group refers to that the structural unit is hydrophobic (lipophilic) on the whole, and the present invention has no particular limitation on the specific composition of the hydrophobic group. Preferably, the hydrophobic group contains at least one hydrophobic functional group. The present invention has a wider range of selection for the hydrophobic functional group. Preferably, the hydrophobic functional group is selected from at least one of an alkyl, an alkenyl, an alkynyl, an aryl and an ester group. For example, the hydrophobic group can be a straight or branched alkyl group of C3-C18, preferably any one of propyl, butyl, amyl, hexyl, heptyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl and its isomers, and any one of the carbon atom or hydrogen atom in the above-mentioned alkyl group can also be replaced by a substituent, and the substituent can be any one of an ester group, a hydroxyl and a phenyl group. For example, the carbon atom at the end of the n-decyl group can be replaced by a methyl ester group. The hydrophobic group can also contain hydrophilic groups such as hydroxyl groups, which are not limited to meet the requirement that the structural unit is hydrophobic on the whole.

[0029] According to some preferred embodiments of the present invention, the hydrophobic group is Wherein, R4 is selected from H or a C5-C16 alkyl group; R5 is selected from a substituted or unsubstituted C5-C16 alkyl group, alkoxy group, aryl group, or phenoxy group. The C5-C16 alkyl group is preferably any one of propyl, butyl, pentyl, hexyl, heptyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, and isomers thereof. Any carbon atom or hydrogen atom in the above alkyl group may be substituted by a substituent, such as any one of an ester group, a hydroxyl group, and a phenyl group.

[0030] According to some preferred embodiments of the present invention, the primary emulsifier is a compound represented by formula (i) and / or formula (ii);

[0031] In formula (i), each R is independently selected from H or C1-C3 alkyl, for example, methyl, ethyl, n-propyl or isopropyl; each R1 is independently selected from Or not present, wherein m is selected from a positive integer of 1-3; each R2 is selected from H or the hydrophobic group, and in the compound represented by formula (i), the molar ratio of the hydrophobic group to the N atom is (0.3-0.75):1, preferably (0.5-0.7):1.

[0032] In formula (ii), each R2 is independently selected from H or the hydrophobic group, and the molar ratio of the hydrophobic group to the nitrogen atom is (0.2-1.2):1, preferably (0.4-1):1. Each R3 is independently selected from a substituted or unsubstituted C1-C3 alkylene group, for example, a methylene group, an ethylene group, or a propylene group; n is a positive integer between 0 and 3, for example, 0, 1, 2, or 3. When n=0, R3 is directly connected to the nitrogen atoms at both ends.

[0033] According to the present invention, in formula (ii), R2 in the n repeating structural units may be the same or different and are independently selected from H or the hydrophobic group, so long as the molar ratio of the hydrophobic group to the N atom satisfies the above-mentioned requirements. Under the above-mentioned molar ratio, the primary emulsifier contains at least one primary and / or secondary amine structure, which has relatively high sulfonation and / or carboxylation activity. This facilitates the sulfonation and / or carboxylation of the primary emulsifier, resulting in an ideal structure for the secondary emulsifier formed, further improving the emulsification effect and stability of the resulting composite emulsifier.

[0034] According to a specific embodiment of the present invention, when the N-containing skeleton is provided by triethylenetetramine, such as formula (ii), the structure of the primary emulsifier can be expressed as Each R2 is independently selected from H or the hydrophobic group, and the molar ratio of the hydrophobic group to the N atom is (0.2-1.2):1, that is, it can be understood that R2 can contain 1, 2, 3 or 4 hydrophobic groups, and the rest are H.

[0035] Another aspect of the present invention provides a method for preparing the composite emulsifier, comprising: contacting a primary emulsifier with a sulfonating agent and / or a carboxylating agent to introduce sulfonic acid groups and / or carboxylic acid groups into a portion of the primary emulsifier.

[0036] In the present invention, the structure of the primary emulsifier has been described in detail above and will not be repeated here. The present invention also does not specify the source of the primary emulsifier, and it can be prepared using any chemical reaction method known in the art. Preferably, the primary emulsifier comprises an N-containing backbone and a hydrophobic group attached to the N-containing backbone. In this case, the primary emulsifier can be prepared, for example, by ring-opening an amine compound with an epoxy compound; the amine compound has the same definition as above.

[0037] Wherein, the epoxy compound has a structure shown in formula (a),

[0038] Wherein, R4 and R5 have the same definition as in the first aspect.

[0039] According to the present invention, in step (1), the hydrophobic group is introduced into the amine compound by a ring-opening reaction between the amine compound and the epoxy compound.

[0040] According to some preferred embodiments of the present invention, the epoxy compound is preferably at least one of methyl 9,10-epoxyoctadecanoate (CAS: 6084-76-0), 1,2-epoxyoctadecane (CAS: 7390-81-0), and C10-16-alkyl glycidyl ether (CAS: 68081-84-5). The above epoxy compounds can be commercially available or prepared using known methods, and the present invention is not particularly limited thereto.

[0041] According to the present invention, preferably, the molar ratio of the amine compound to the epoxy compound is 1:(1-5), for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or other typical but non-limiting molar ratios or ranges therebetween. Preferably, the molar ratio of the amine compound to the epoxy compound is 1:(1.5-3.5).

[0042] In the present invention, an amine compound and an epoxy compound can be added to a reactor to undergo a ring-opening reaction. The present invention has no particular requirements for the conditions of the ring-opening reaction, as long as they are conducive to the ring-opening reaction of the epoxy compound. Those skilled in the art can select the conditions according to actual needs. Preferably, the conditions of the ring-opening reaction include: a reaction temperature of 60-140°C, preferably 80-120°C, and a reaction time of 5-15 hours, preferably 6-12 hours.

[0043] Preferably, the ring-opening reaction is carried out under stirring conditions. The present invention has no particular limitation on the stirring conditions, as long as they are conducive to the reaction.

[0044] In the present invention, the ring-opening reaction can also be carried out in the presence of a catalyst. The present invention does not particularly limit the catalyst, and any catalyst known in the art that can promote the ring-opening reaction of epoxy compounds can be used in the present invention. For example, the catalyst can be an organic acid and / or an inorganic acid. Preferably, it is at least one of sulfuric acid, phosphoric acid, acetic acid, oxalic acid, trifluoroacetic acid, p-toluenesulfonic acid, and aminosulfonic acid, and more preferably at least one of sulfuric acid, phosphoric acid, acetic acid, and oxalic acid.

[0045] Preferably, the molar ratio of the catalyst to the epoxy compound is (0.001-0.02):1, preferably (0.003-0.015):1.

[0046] In the present invention, the product of the ring-opening reaction can be directly used as the primary emulsifier for the next reaction. Alternatively, the product mixture obtained from the ring-opening reaction can be purified first to remove any unreacted raw materials by various means before proceeding to the next reaction. The present invention has no particular requirements for this, as long as the product contains a compound of the target structure. Those skilled in the art can make the selection based on actual needs.

[0047] The present invention has no particular requirements for the specific type of the sulfonating agent, as long as it can introduce sulfonic acid groups into a portion of the primary emulsifier. Those skilled in the art can select the agent based on actual conditions. The present invention also has no particular restrictions on the source of the sulfonating agent, which can be purchased commercially or prepared by chemical reaction methods known in the art.

[0048] According to some preferred embodiments of the present invention, the sulfonating agent is a sulfonate and / or an alkyl sultone.

[0049] Preferably, the sulfonate has a structure shown in formula (b),

[0050] Wherein, X is a halogen atom, preferably Cl or Br, R6 is selected from a substituted or unsubstituted C1-C8 alkylene group, preferably a C2-C4 alkylene group, for example, it can be any one of methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene or their isomers; y is 0 or 1; M is selected from Na, K or ammonium group.

[0051] According to some preferred embodiments of the present invention, the sulfonating agent is at least one of sodium 3-chloro-2-hydroxypropane sulfonate (CAS: 126-83-0), 1,3-propane sultone (CAS: 1120-71-4) and / or 1,4-butane sultone (CAS: 1633-83-6), more preferably 1,3-propane sultone and / or 1,4-butane sultone.

[0052] The present invention does not particularly require the specific type of the carboxylating agent, and those skilled in the art may select a carboxylating agent based on actual conditions, provided that the carboxylating agent can be introduced into a portion of the primary emulsifier. The present invention also does not particularly limit the source of the carboxylating agent, and the carboxylating agent may be commercially available or prepared by chemical reaction methods known in the art. According to some preferred embodiments of the present invention, the carboxylating agent is maleic anhydride.

[0053] According to the present invention, in order to promote the sulfonation reaction and / or carboxylation reaction and prevent the formation of inorganic acid, preferably, the contacting is carried out in the presence of an acid binding agent. The present invention is not particularly limited to the specific type of the acid binding agent, and conventional acid binding agents in the art can be used, for example, organic bases or inorganic bases, preferably inorganic bases, for example, at least one of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.

[0054] According to the present invention, preferably, the molar ratio of the acid binding agent to the sulfonating agent and / or carboxylating agent is (0.5-2.5):1, preferably (0.5-2):1. In this preferred embodiment, the acid binding agent effectively binds the acidic byproducts produced during the reaction, promoting the forward reaction. At the same time, the acid binding agent is an alkaline salt. Adding an appropriate amount of the acid binding agent can effectively reduce the formation of salt content without affecting the reaction, thereby preventing the reaction product from being too viscous and difficult to pour or use on site.

[0055] According to the present invention, preferably, the molar ratio of the total molar amount of the sulfonating agent and / or carboxylating agent to the primary emulsifier calculated as containing the N skeleton is (0.1-0.5):1, preferably (0.2-0.4):1. By adopting the above preferred embodiment, the relative contents of the primary emulsifier and the auxiliary emulsifier in the prepared composite emulsifier can be controlled, which is conducive to exerting the synergistic effect of the primary emulsifier and the auxiliary emulsifier, thereby further improving the emulsification effect of the emulsifier and improving the electrical stability and thermal stability of the emulsified system.

[0056] The present invention does not particularly limit the specific conditions for contacting the primary emulsifier with the sulfonating agent and / or carboxylating agent, as long as they are conducive to the reaction. Those skilled in the art can select the conditions based on actual needs. Preferably, the contact conditions include: a reaction temperature of 80-120°C and a reaction time of 3-5 hours.

[0057] In the present invention, the contacting can be carried out in the presence of a solvent. The present invention has a wide range of choices for the solvent, and can select any organic solvent commonly used in the art, such as at least one of methanol, ethanol, n-octanol, isooctyl alcohol, dimethylformamide, dimethyl sulfoxide, and ethylene glycol. The present invention has no particular requirements for the amount of the solvent used, as long as it can fully disperse the reactants. Those skilled in the art can select the solvent based on actual needs.

[0058] According to some preferred embodiments of the present invention, the preparation method further comprises the step of removing the solvent from the mixture obtained by the reaction. In the present invention, various methods can be used to remove the solvent from the product mixture, preferably by vacuum distillation. For example, the mixture obtained by the reaction is cooled and then subjected to vacuum distillation. Preferably, the pressure of the vacuum distillation is 1-5kPa, preferably 1.2-2kPa, and the temperature is 40-80°C, preferably 45-60°C. In the present invention, unless otherwise stated, the pressure refers to absolute pressure.

[0059] According to a particularly preferred embodiment of the present invention, the preparation method of the composite emulsifier comprises:

[0060] (1) performing a ring-opening reaction between an amine compound and an epoxy compound;

[0061] Wherein, the epoxy compound has a structure shown in formula (a),

[0062] Wherein, R4 and R5 have the same definitions as in the first aspect;

[0063] (2) contacting the product of the ring-opening reaction with a sulfonating agent and / or a carboxylating agent;

[0064] The total molar ratio of the amine compound, the epoxy compound and the sulfonating agent and / or the carboxylating agent is 1:(1-5):(0.2-0.5).

[0065] According to the present invention, an amine compound and an epoxy compound are subjected to a ring-opening reaction to obtain a primary emulsifier having an N-containing skeleton and a hydrophobic group connected to the skeleton, and then a sulfonic acid group and / or a carboxylic acid group are introduced into part of the primary emulsifier by a sulfonation reaction and / or a carboxylation reaction to obtain a sulfonated product and / or a carboxylated product of the primary emulsifier, i.e., a composite emulsifier containing a primary emulsifier and a secondary emulsifier is obtained. The composite emulsifier formed by the primary emulsifier and the secondary emulsifier based on the same skeleton structure can be more closely integrated, and the interaction between the two can effectively reduce the oil-water interfacial tension, form a stable interfacial film, prevent the coalescence of water droplets, and make the oil-water emulsion system stable. The composite emulsifier has excellent emulsifying effect, good electrical stability and thermal stability as an oil-based drilling fluid emulsifier, can be effectively applied to oil-based drilling fluids with different oil-water ratios and different types of base oils, and is suitable for the emulsification of oil-based drilling fluids such as gas oil, white oil, and diesel.

[0066] Another aspect of the present invention provides a composite emulsifier, the raw materials for preparing the composite emulsifier include polyamine material, epoxy fatty acid methyl ester, catalyst, 3-chloro-2-hydroxypropane sulfonic acid sodium salt, and acid binding agent;

[0067] Wherein, the polyamine material is selected from one or two of diethylenetriamine and triethylenetetramine.

[0068] Preferably, the molar ratio of the polyamine material, epoxy fatty acid methyl ester, catalyst, 3-chloro-2-hydroxypropane sulfonic acid sodium salt, and acid binding agent is 1: (1.5-3.5): (0.005-0.02): (0.2-0.5): (0.2-0.5).

[0069] A second aspect of the present invention provides an oil-based drilling fluid, which comprises a base oil and a treatment agent, wherein the treatment agent comprises the above-mentioned composite emulsifier.

[0070] In the present invention, the base oil in the oil-based drilling fluid can be selected from a wide range of types and can be provided by any oil phase commonly used in the art. Those skilled in the art can select the base oil based on actual needs. Preferably, the base oil is selected from at least one of gas oil, white oil, and diesel, preferably white oil.

[0071] According to some preferred embodiments of the present invention, based on 100 parts by weight of the base oil, the content of the composite emulsifier is 2-10 parts by weight, preferably 3-5 parts by weight.

[0072] According to the present invention, the treatment agent may further include at least one of, for example, organic soil, a plugging agent, a weighting agent, a wetting agent, an alkaline regulator, and a fluid loss reducer. Those skilled in the art may select the agent based on actual needs, and the present invention is not particularly limited thereto.

[0073] According to some preferred embodiments of the present invention, the organic soil may be at least one of organically modified bentonite, organically modified sepiolite, and organically modified palygorskite. The present invention has no particular limitation on the source of the organic soil, which may be commercially available.

[0074] The present invention has no particular limitation on the source of the fluid loss agent, and commercially available products known to those skilled in the art can be used. Preferably, the fluid loss agent is selected from at least one of natural asphalt, oxidized asphalt, and styrene-butadiene rubber.

[0075] According to some preferred embodiments of the present invention, the weighting agent may be at least one of barite, micro-manganese ore powder, and iron ore powder.

[0076] According to some preferred embodiments of the present invention, the alkaline regulator may be calcium oxide and / or sodium carbonate, preferably calcium oxide.

[0077] In the present invention, the amounts of the fluid loss control agent, alkalinity control agent, and organic soil can be selected based on actual needs and are not particularly limited. According to some preferred embodiments of the present invention, based on 100 parts by weight of the base oil, the amount of the fluid loss control agent is 2-6 parts by weight, the amount of the alkalinity control agent is 0.5-2 parts by weight, and the amount of the organic soil is 0.5-3 parts by weight.

[0078] The present invention will be described in detail below through examples.

[0079] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available.

[0080] In the present invention, the method for testing the demulsification voltage and emulsification rate of a composite emulsifier in a standard oil-based emulsion comprises: stirring the composite emulsifier and No. 5 white oil at 10,000 rpm for 30 minutes to dissolve the emulsifier in the oil; then, adding a 25 wt% aqueous solution of CaCl2 at an oil-to-water ratio of 80:20 by volume; and stirring at 10,000 rpm for 2 hours to obtain an emulsion to be tested. The composite emulsifier is added at a dosage of 5 wt% based on the total mass of the oil and water.

[0081] Electrical stability test: Place the probe of the electrical stability tester in the emulsion to be tested, record and calculate the average value of the emulsion breaking voltage of the two measurement results, and the difference between the two readings shall not exceed 5%.

[0082] Emulsification rate test: After aging the emulsion to be tested at 150°C for 16 hours, cool to room temperature, and stir at 10,000 rpm for 20 minutes. Pour the emulsion into a 500mL graduated cylinder and let it stand for 24 hours. The volume of the separated oil phase is then read. The emulsification rate (W) is calculated as follows: W = (V0 - V0) / V0 × 100%;

[0083] In the above formula, V0 is the volume of the emulsion, unit is mL; W is the emulsification rate, unit is %; V is the volume of the separated oil layer, unit is mL.

[0084] In the present invention, the content of C, H, O, N, and S in the product was measured using an organic element analyzer (Elementar Unicube). The molar ratio of sulfur and nitrogen in the emulsifier was further calculated.

[0085] In the present invention, the infrared absorption spectrum is tested using a Fourier transform infrared spectrometer, and the test mode is the ATR mode.

[0086] In the present invention, mass spectrometry is performed in a matrix-assisted laser desorption time-of-flight mass spectrometer (MALDI-TOF / TOF), and the test conditions include: methanol dissolution, CHCA matrix.

[0087] Example 1

[0088] (1) In a double-necked round-bottom flask equipped with a reflux condenser, 20 mol of diethylenetriamine and 38 mol of 9,10-epoxyoctadecanoic acid methyl ester (CAS: 6084-76-0, commercially available, purity 75%) were added and stirred uniformly. 0.2 mol of p-toluenesulfonic acid was added, and the mixture was heated to 90°C and stirred for 7.5 h to obtain a primary emulsifier.

[0089] A portion of the main emulsifier was separated by silica gel column chromatography (petroleum ether: ethyl acetate 2:1-1:5), and the solvent was distilled out by rotary evaporator to obtain the purified product, which was then analyzed by infrared absorption spectrum. The results are shown in Figure 1. From the infrared absorption spectrum, it can be seen that the product has a strong affinity to the product at 1080-1160 cm -1 The absorption peak belonging to the epoxy bond disappears and is located at 3200-3500cm -1 The characteristic peaks belonging to the hydroxyl group are very obvious, indicating that a ring-opening reaction has occurred between diethylenetriamine and epoxy fatty acid methyl ester. The main emulsifier was subjected to mass spectrometry analysis, and the results are shown in Figure 2. It can be seen that the structures corresponding to the characteristic peaks with mass-to-charge ratios of 724.301, 726.307, and 728.298 are diethylenetriamine substituted with dihydroxy fatty acid methyl esters. The multi-peak signals are derived from the presence of linoleic acid methyl ester and oleic acid methyl ester in the 9,10-epoxyoctadecanoic acid methyl ester component, which will produce epoxy oleic acid methyl ester and epoxy linoleic acid methyl ester after epoxidation. The above results prove that the main emulsifier was successfully synthesized. Combining the results of mass spectrometry and infrared absorption spectroscopy, it is proved that the main emulsifier has the structure shown in formula (i), wherein the two R2 are R4 is an n-octyl methyl ester group, R5 is an n-octyl group, and the molar ratio of the hydrophobic group to the nitrogen atom in the diethylenetriamine backbone is 2:3.

[0090] (2) The product obtained in step (1), 6 mol of sodium 3-chloro-2-hydroxypropane sulfonate and 150 mL of ethanol were mixed evenly, 6 mol of potassium carbonate was added, the mixture was heated to 80° C. and stirred for 3 h to obtain a second intermediate;

[0091] (3) After cooling the second intermediate obtained in step (2) to room temperature, the solvent ethanol was distilled off under reduced pressure at 50° C. and 1.5 kPa to obtain composite emulsifier A1.

[0092] The composite emulsifier A1 was separated by silica gel column chromatography (dichloromethane: methanol 1:1-1:8), and the solvent was distilled out by rotary evaporator to obtain a purified product, which was then subjected to infrared absorption spectrum test. The infrared absorption spectrum is shown in FIG3 . It can be seen from the infrared absorption spectrum that the product has a peak at 3200-3500 cm -1 The characteristic absorption peak of hydroxyl group becomes larger, indicating that the content of hydroxyl group increases.-1 The presence of characteristic peaks attributable to sulfonate groups indicates their presence in the structure. The mass spectrometry analysis results are shown in Figure 4. The characteristic peak at a mass-to-charge ratio of 864.574 corresponds to a structure substituted with diethylenetriamine (dihydroxy fatty acid methyl ester) with sulfonic acid groups introduced. Combined with the results in Figures 3 and 4, this suggests that sulfonic acid groups have been incorporated into the diethylenetriamine backbone of some primary emulsifiers. Elemental composition analysis using an organic element analyzer revealed 4.92% N, 65.4% C, 10% H, 1.15% S, and 16.95% O. The calculated molar ratio of the secondary emulsifier to the primary emulsifier is 0.44:1.

[0093] Based on the total weight of the composite emulsifier, the content of the diethylenetriamine skeleton is 12 wt %. In 1 mol of the composite emulsifier A1, the molar weight of the sulfonic acid group is 0.31 mol.

[0094] The emulsification rate and demulsification voltage of composite emulsifier A1 in standard oil-based emulsion are shown in Table 1.

[0095] Example 2

[0096] (1) In a double-necked round-bottom flask equipped with a reflux condenser, 20 mol of diethylenetriamine and 38 mol of methyl 9,10-epoxyoctadecanoate (CAS: 6084-76-0) were added and mixed uniformly. 0.25 mol of sulfuric acid was added, and the mixture was heated to 100°C and stirred for 8 h to obtain a primary emulsifier. The molar ratio of the hydrophobic group to the nitrogen atom in the diethylenetriamine backbone was 2:3.

[0097] (2) The primary emulsifier, 6 mol of sodium 3-chloro-2-hydroxypropane sulfonate and 200 mL of isooctyl alcohol were mixed evenly, 6 mol of sodium hydroxide was added, the mixture was heated to 90° C. and stirred for 4 h;

[0098] (3) After cooling the product obtained in step (2) to room temperature, the solvent isooctyl alcohol is distilled off under reduced pressure at 50° C. and 1.2 kPa to obtain composite emulsifier A2.

[0099] Emulsifier A2 was separated by silica gel column chromatography (dichloromethane:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. The elemental composition was then analyzed using an organic element analyzer, revealing that the N content was 5.1wt%, the C content was 64.2wt%, the H content was 11.2wt%, the S content was 1.2wt%, and the O content was 16.7wt%. The calculated molar ratio of the auxiliary emulsifier to the primary emulsifier was 0.45:1. The molar ratio of sulfur to nitrogen in the emulsifier was 0.1:1. Based on the total amount of the composite emulsifier, the content of the diethylenetriamine skeleton was 12.5wt%. The molar amount of the sulfonic acid group in 1 mol of composite emulsifier A2 was 0.31 mol.

[0100] The emulsification rate and demulsification voltage of composite emulsifier A2 in standard oil-based emulsion are shown in Table 1.

[0101] Example 3

[0102] (1) In a double-necked round-bottom flask with a reflux condenser, 20 mol of triethylenetetramine and 45 mol of 9,10-epoxyoctadecanoic acid methyl ester (CAS: 6084-76-0) were added and stirred evenly. 0.3 mol of phosphoric acid was added and the mixture was heated to 80°C and stirred for 6 h to obtain a primary emulsifier. The molar ratio of the hydrophobic group to the nitrogen atom in the triethylenetetramine skeleton was 0.56:1.

[0103] (2) The primary emulsifier, 8 mol of 3-chloro-2-hydroxypropanesulfonic acid sodium salt and 150 mL of isopropanol were mixed evenly, 4 mol of potassium carbonate was added, the mixture was heated to 80° C. and stirred for 3 h to obtain a second intermediate;

[0104] (3) After the second intermediate was cooled to room temperature, the solvent isopropanol was distilled off under reduced pressure at 50° C. and 1.2 kPa to obtain composite emulsifier A3.

[0105] Composite emulsifier A3 was separated by silica gel column chromatography (methylene chloride:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. The elemental composition was analyzed using an organic element analyzer, revealing a N content of 4.3 wt%, a C content of 64.4 wt%, a H content of 10.7 wt%, a S content of 1.1 wt%, and an O content of 15.9 wt%. The molar ratio of the auxiliary emulsifier to the primary emulsifier was calculated to be 0.75:1.

[0106] Based on the total weight of the composite emulsifier, the content of the triethylenetetramine skeleton is 11.2 wt %. In 1 mol of the composite emulsifier A3, the molar weight of the sulfonic acid group is 0.45 mol.

[0107] The emulsification rate and demulsification voltage of composite emulsifier A3 in standard oil-based emulsion are shown in Table 1.

[0108] Example 4

[0109] (1) In a double-necked round-bottom flask equipped with a reflux condenser, 20 mol of triethylenetetramine and 52 mol of 9,10-epoxyoctadecanoic acid methyl ester (CAS: 6084-76-0) were added and mixed and stirred evenly. 0.2 mol of p-toluenesulfonic acid was added and the mixture was heated to 110°C and stirred for 12 h to obtain a first intermediate, wherein the molar ratio of the hydrophobic group to the nitrogen atom in the triethylenetetramine skeleton was 0.65:1.

[0110] (2) The first intermediate, 8 mol of sodium 3-chloro-2-hydroxypropane sulfonate and 300 mL of n-octanol were mixed evenly, 8 mol of potassium carbonate was added, the mixture was heated to 120° C. and stirred for 5 h to obtain the second intermediate;

[0111] (3) After the second intermediate was cooled to room temperature, the solvent n-octanol was distilled off under reduced pressure at 50° C. and 1.2 kPa to obtain composite emulsifier A4.

[0112] Composite emulsifier A4 was separated by silica gel column chromatography (dichloromethane:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. The elemental composition was analyzed using an organic element analyzer, revealing an N content of 4.0 wt%, a C content of 65.4 wt%, an H content of 11.4 wt%, an S content of 0.9 wt%, and an O content of 16.8 wt%. The molar ratio of the auxiliary emulsifier to the primary emulsifier was calculated to be 0.65:1.

[0113] Based on the total amount of the emulsifier, the content of the triethylenetetramine skeleton is 10 wt %. In 1 mol of the composite emulsifier, the molar amount of the sulfonic acid group is 0.39 mol.

[0114] The emulsification rate and demulsification voltage of composite emulsifier A4 in standard oil-based emulsion are shown in Table 1.

[0115] Example 5

[0116] The method of Example 1 was followed, except that 1,2-epoxydodecane was used in an equal molar amount to replace 9,10-epoxyoctadecanoic acid methyl ester (cas: 6084-76-0), to obtain composite emulsifier A5.

[0117] Emulsifier A5 was separated by silica gel column chromatography (dichloromethane: methanol 1:1-1:8), and the solvent was distilled off by a rotary evaporator to obtain a purified product. The elemental composition was analyzed by an organic element analyzer, wherein the N element content was 5.9wt%, the C element content was 67.3wt%, the H element content was 11.9wt%, the S element content was 1.3wt%, and the O element content was 8.9wt%. The molar ratio of the auxiliary emulsifier to the main emulsifier was calculated to be 0.41:1.

[0118] Based on the total weight of the composite emulsifier, the content of the diethylenetriamine skeleton is 14.5 wt %. In 1 mol of the composite emulsifier, the molar weight of the sulfonic acid group is 0.29 mol.

[0119] The emulsification rate and demulsification voltage of composite emulsifier A5 in standard oil-based emulsion are shown in Table 1.

[0120] Example 6

[0121] The method of Example 1 was followed, except that an equimolar amount of 1,3-propane sultone was used to replace sodium 3-chloro-2-hydroxypropane sulfonate, to obtain composite emulsifier A6.

[0122] Composite emulsifier A6 was separated by silica gel column chromatography (methylene chloride:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. The elemental composition was analyzed using an organic element analyzer, revealing a nitrogen content of 5.4 wt%, a carbon content of 66.1 wt%, a hydrogen content of 10.8 wt%, a sulfur content of 1.3 wt%, and an oxygen content of 15.1 wt%. The molar ratio of the auxiliary emulsifier to the primary emulsifier was calculated to be 0.47:1.

[0123] Based on the total weight of the composite emulsifier, the diethylenetriamine skeleton content was 13.2 wt %. The molar weight of the sulfonic acid group in 1 mol of the composite emulsifier was 0.32 mol. The emulsification rate and demulsification voltage of composite emulsifier A6 in a standard oil-based emulsion are shown in Table 1.

[0124] Example 7

[0125] The method of Example 1 was followed, except that the amount of sodium 3-chloro-2-hydroxypropane sulfonate used was 14 mol, to obtain composite emulsifier A7.

[0126] Composite emulsifier A7 was separated by silica gel column chromatography (methylene chloride:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. Elemental composition analysis using an organic element analyzer revealed a nitrogen content of 5.0 wt % and a sulfur content of 2.73 wt %. The molar ratio of the auxiliary emulsifier to the primary emulsifier was calculated to be 2.5:1.

[0127] Based on the total weight of the composite emulsifier, the content of the diethylenetriamine skeleton is 11.9 wt %. In 1 mol of the composite emulsifier, the molar weight of the sulfonic acid group is 0.71 mol.

[0128] The emulsification rate and demulsification voltage of emulsifier A7 in standard oil-based emulsion are shown in Table 1.

[0129] Example 8

[0130] The method of Example 1 was followed, except that the amount of sodium 3-chloro-2-hydroxypropane sulfonate used was 4.2 mol, to obtain composite emulsifier A8.

[0131] Composite emulsifier A8 was separated by silica gel column chromatography (methylene chloride:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. Elemental composition analysis using an organic element analyzer revealed a nitrogen content of 5.6 wt % and a sulfur content of 0.8 wt %. The molar ratio of the auxiliary emulsifier to the primary emulsifier was calculated to be 0.23:1.

[0132] Based on the total weight of the composite emulsifier, the content of the diethylenetriamine skeleton is 13.3 wt %. In 1 mol of the composite emulsifier, the molar weight of the sulfonic acid group is 0.19 mol.

[0133] The emulsification rate and demulsification voltage of composite emulsifier A8 in standard oil-based emulsion are shown in Table 1.

[0134] Example 9

[0135] (1) In a two-necked round-bottom flask equipped with a reflux condenser, 20 mol of aminoethylpiperazine and 38 mol of methyl 9,10-epoxyoctadecanoate (CAS: 6084-76-0) were added and stirred uniformly. 0.25 mol of p-toluenesulfonic acid was added, and the mixture was heated to 100°C and stirred for 8 hours to obtain a primary emulsifier. The molar ratio of the hydrophobic group to the nitrogen atom in the aminoethylpiperazine skeleton was 2:3.

[0136] (2) The primary emulsifier, 6 mol of sodium 3-chloro-2-hydroxypropane sulfonate and 200 mL of isooctyl alcohol were mixed evenly, 6 mol of sodium hydroxide was added, the mixture was heated to 90° C. and stirred for 4 h;

[0137] (3) After cooling the product obtained in step (2) to room temperature, the solvent isooctyl alcohol is distilled off under reduced pressure at 50° C. and 1.2 kPa to obtain composite emulsifier A2.

[0138] Emulsifier A2 was separated using silica gel column chromatography (dichloromethane:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. The elemental composition was then analyzed using an organic element analyzer, revealing a nitrogen content of 5.1 wt%, a carbon content of 63.2 wt%, a hydrogen content of 10.4 wt%, a sulfur content of 1.1 wt%, and an oxygen content of 15.2 wt%. The calculated molar ratio of the auxiliary emulsifier to the primary emulsifier was 0.38:1. The molar ratio of sulfur to nitrogen in the emulsifier was 0.09:1. Based on the total amount of the composite emulsifier, the aminoethylpiperazine skeleton content was 12.51 wt%. The molar weight of sulfonic acid groups in 1 mol of composite emulsifier A2 was 0.28 mol.

[0139] The emulsification rate and demulsification voltage of composite emulsifier A9 in standard oil-based emulsion are shown in Table 1.

[0140] Example 10

[0141] (1) In a double-necked round-bottom flask equipped with a reflux condenser, 20 mol of ethylenediamine and 38 mol of methyl 9,10-epoxyoctadecanoate (CAS: 6084-76-0) were added and stirred uniformly. 0.25 mol of p-toluenesulfonic acid was added, and the mixture was heated to 100°C and stirred for 8 hours to obtain a primary emulsifier. The molar ratio of the hydrophobic group to the nitrogen atom in the ethylenediamine backbone was 1:1.

[0142] (2) The primary emulsifier, 6 mol of sodium 3-chloro-2-hydroxypropane sulfonate and 200 mL of isooctyl alcohol were mixed evenly, 6 mol of sodium hydroxide was added, the mixture was heated to 90° C. and stirred for 4 h;

[0143] (3) After cooling the product obtained in step (2) to room temperature, the solvent isooctyl alcohol is distilled off under reduced pressure at 50° C. and 1.2 kPa to obtain composite emulsifier A2.

[0144] Emulsifier A2 was separated using silica gel column chromatography (methylene chloride:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. The elemental composition was then analyzed using an organic element analyzer. The nitrogen content was 3.7 wt%, the sulfur content was 1.3 wt%, and the calculated molar ratio of the auxiliary emulsifier to the primary emulsifier was 0.43:1. The molar ratio of sulfur to nitrogen in the emulsifier was 0.154:1. Based on the total amount of the composite emulsifier, the ethylenediamine backbone content was 7.9 wt%. The molar amount of sulfonic acid groups in 1 mol of composite emulsifier A2 was 0.3 mol.

[0145] The emulsification rate and demulsification voltage of composite emulsifier A10 in standard oil-based emulsion are shown in Table 1.

[0146] Comparative Example 1

[0147] The method of Example 1 was followed, except that steps (2) and (3) were not performed, and the primary emulsifier obtained in step (1) was used as emulsifier DA1.

[0148] The emulsification rate and demulsification voltage of emulsifier DA1 in standard oil-based emulsion are shown in Table 1.

[0149] Comparative Example 2

[0150] (1) In a double-necked round-bottom flask equipped with a reflux condenser, 20 mol of diethylenetriamine and 38 mol of methyl 9,10-epoxyoctadecanoate (CAS: 6084-76-0) were added and mixed evenly. 0.2 mol of p-toluenesulfonic acid was added, and the mixture was heated to 90°C and stirred for 7.5 hours to obtain the first intermediate.

[0151] (2) The first intermediate, 22 mol of 3-chloro-2-hydroxypropanesulfonic acid sodium salt and 1000 mL of n-octanol were mixed evenly, 22 mol of potassium carbonate was added, the mixture was heated to 100° C. and stirred for 4 h to obtain the second intermediate;

[0152] (3) After the second intermediate was cooled to room temperature, the solvent ethanol was distilled off under reduced pressure at 50°C and 1.2 kPa to obtain the composite emulsifier DA2.

[0153] Composite emulsifier DA2 was separated using silica gel column chromatography (dichloromethane:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. Analysis of the elemental composition using an organic element analyzer revealed that the nitrogen content was 4.1 wt %, and the sulfur content was 3.4 wt %. This emulsifier contained only the auxiliary emulsifier, and the diethylenetriamine backbone content was 10 wt %, based on the total weight of the composite emulsifier. The molar weight of sulfonic acid groups in 1 mol of the composite emulsifier was 1.09 mol.

[0154] The emulsification rate and demulsification voltage of composite emulsifier DA2 in standard oil-based emulsion are shown in Table 1.

[0155] Comparative Example 3

[0156] (1) In a double-necked round-bottom flask equipped with a reflux condenser, 20 mol of triethylenetetramine and 40 mol of methyl 9,10-epoxyoctadecanoate (CAS: 6084-76-0) were added and mixed evenly, 0.2 mol of p-toluenesulfonic acid was added, and the mixture was heated to 80°C and stirred for 6 h to obtain the first intermediate;

[0157] (2) The first intermediate, 40 mol of 3-chloro-2-hydroxypropanesulfonic acid sodium salt and 2000 mL of n-octanol were mixed evenly, 40 mol of potassium carbonate was added, the mixture was heated to 120° C. and stirred for 8 h to obtain the second intermediate;

[0158] (3) After the second intermediate was cooled to room temperature, the solvent n-octanol was distilled off under reduced pressure at 50°C and 1.2 kPa to obtain emulsifier DA3.

[0159] Emulsifier DA3 was separated using silica gel column chromatography (dichloromethane:methanol 1:1-1:8), and the solvent was distilled off using a rotary evaporator to obtain a purified product. Analysis of the elemental composition using an organic element analyzer revealed that the nitrogen content was 5.1 wt % and the sulfur content was 5.9 wt %. The molar ratio of sulfur to nitrogen in the emulsifier was 1.5:1. The triethylenetetramine backbone content was 13.3 wt % based on the total weight of the composite emulsifier. This emulsifier contained only a co-emulsifier, and the molar weight of sulfonic acid groups per 1 mol of the composite emulsifier was 2.02 mol.

[0160] The emulsification rate and demulsification voltage of emulsifier DA3 in standard oil-based emulsion are shown in Table 1.

[0161] Comparative Example 4

[0162] The main emulsifier Span 80 and the auxiliary emulsifier Tween 80 were mixed in a molar ratio of 3:1 to serve as emulsifier DA4.

[0163] The emulsification rate and demulsification voltage of emulsifier DA4 in standard oil-based emulsion are shown in Table 1.

[0164] Table 1

[0165] Test Case

[0166] Drilling fluid configuration:

[0167] Based on 100 parts by weight of 5# white oil, 4 parts by weight of the emulsifiers in the above examples and comparative examples were added, stirred at 10,000 rpm for 30 minutes, and then 25 wt% calcium chloride solution was added at a volume ratio of 80:20. Then, based on 100 parts by weight of 5# white oil, 4 parts by weight of natural asphalt, 2 parts by weight of calcium oxide, and 2 parts by weight of organic bentonite were added, and then barite was added to increase the density to 1.8-2.2 g / cm 3 Continuing high stirring for 2 hours, the density was 2g / cm 3 Oil-based drilling fluid.

[0168] (1) Electrical stability test: Place the probe of the electrical stability tester in the oil-based drilling fluid obtained by the above configuration, record and calculate the average demulsification voltage value of the two measurement results, and the difference between the two readings shall not exceed 5%.

[0169] The drilling fluid's plastic viscosity (PV), dynamic shear stress (YP), and fluid loss at high temperature and high pressure (FLHTHP) were tested in accordance with the national standard GB / T16783.2-2012, "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry—Part 2: Oil-Based Drilling Fluids." The results are shown in Table 2.

[0170] Table 2

[0171] (2) Thermal stability test

[0172] The drilling fluids obtained by the above configurations were aged at 180°C for 24 h, and then the drilling fluid performance tests were performed using the same method. The results are shown in Table 3.

[0173] The drilling fluids obtained by the above configurations were aged at 200°C for 96 h, and then the drilling fluid performance tests were performed using the same method. The results are shown in Table 4.

[0174] Table 3

[0175] Table 4

[0176] It can be seen from the results in Tables 2-4 that, compared with the comparative example, the composite emulsifier product prepared in the embodiment of the present invention has more excellent electrical stability and thermal stability, while ensuring a lower high-temperature and high-pressure filtration loss, with obvious advantages.

[0177] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite emulsifier, comprising a primary emulsifier and an auxiliary emulsifier, It is characterized in that The auxiliary emulsifier is a sulfonated product and / or a carboxylated product of the main emulsifier.

2. The composite emulsifier according to claim 1, in, Under the condition of 5wt% addition, the demulsification voltage of the composite emulsifier in the standard oil-based emulsion is 50-400V, preferably 200-280V, wherein the standard oil-based emulsion is composed of No. 5 white oil and 25wt% CaCl 2 The aqueous solution composition has an oil-water volume ratio of 80:20; Preferably, the emulsification rate of the composite emulsifier in the standard oil-based emulsion is ≥ 90%, preferably 95-100%.

3. The composite emulsifier according to claim 1 or 2, in, In the composite emulsifier, the molar ratio of the auxiliary emulsifier to the primary emulsifier is (0.25-1):1, preferably (0.4-0.8):

1.

4. The composite emulsifier according to any one of claims 1 to 3, in, The auxiliary emulsifier contains sulfonic acid groups and / or carboxylic acid groups. In 1 mol of the composite emulsifier, the molar amount of the sulfonic acid groups and / or carboxylic acid groups is 0.1-1.2 mol, preferably 0.3-0.6 mol.

5. The composite emulsifier according to any one of claims 1 to 4, in, The primary emulsifier includes a N-containing skeleton and a hydrophobic group connected to the N-containing skeleton.

6. The composite emulsifier according to claim 5, in, Based on the total amount of the composite emulsifier, the content of the N-containing skeleton is 5-20wt%, preferably 10-15wt%.

7. The composite emulsifier according to claim 5 or 6, in, The N-containing skeleton is provided by an amine compound, which contains at least two amine groups, preferably at least one of a chain or cyclic diamine, triamine, tetramine and pentamine; preferably, the amine compound is selected from at least one of substituted or unsubstituted piperazine, ethylenediamine, propylenediamine, butylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

8. The composite emulsifier according to any one of claims 5 to 7, in, The hydrophobic group contains at least one hydrophobic functional group, preferably at least one of a C5-C16 alkyl group, an alkenyl group, an alkynyl group, an aryl group and an ester group; Preferably, the hydrophobic group is Among them, R 4 R is selected from H or C5-C16 alkyl, preferably any one of n-hexyl, n-octyl, n-decyl, and n-dodecyl; 5 Selected from substituted or unsubstituted C5-C16 alkyl, alkoxy, aryl or phenoxy.

9. The composite emulsifier according to any one of claims 5 to 8, in, The primary emulsifier is a compound represented by formula (i) and / or formula (ii); Wherein, in formula (i), each R is independently selected from H or C1-C3 alkyl; each R 1 Each independently selected from or not present, wherein m is selected from a positive integer of 1-3; each R 2 is selected from H or the hydrophobic group, and in the compound represented by formula (i), the molar ratio of the hydrophobic group to the N atom is (0.3-0.75):1; In formula (ii), each R 2 Each independently selected from H or the hydrophobic group, and the molar ratio of the hydrophobic group to the N atom is (0.2-1.5):1, each R 3 Each is independently selected from substituted or unsubstituted C1-C3 alkylene; n is a positive integer between 0 and 3.

10. An oil-based drilling fluid, It is characterized in that The oil-based drilling fluid comprises a base oil and a treating agent, wherein the treating agent comprises the composite emulsifier according to any one of claims 1 to 9; Preferably, based on 100 parts by weight of the base oil, the content of the composite emulsifier is 2-10 parts by weight.

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