Reducible tetrahydroxy quaternary ammonium salt, preparation method thereof and low-temperature reservoir fracturing fluid auxiliary agent

Abstract

The invention relates to the technical field of oilfield chemistry, in particular to a reductive tetrahydroxy quaternary ammonium salt, a preparation method thereof and a low-temperature reservoir fracturing fluid assistant.The reductive tetrahydroxy quaternary ammonium salt is prepared according to the following steps that firstly, a needed amount of 2, 3-epoxypropyl trimethyl ammonium chloride is dissolved in water, and a reaction solution is obtained; and 2, introducing nitrogen into the reaction solution to remove oxygen, adding a required amount of hydroxylamine hydrochloride to obtain a reaction mixed solution, and reacting to obtain an aqueous solution of the reductive tetrahydroxy quaternary ammonium salt. The reductive tetrahydroxy quaternary ammonium salt provided by the invention has high reducibility, simultaneously contains four cations and four hydroxyls, and has the characteristics of strong polarity, small molecular weight and high charge density. The low-temperature reservoir fracturing fluid additive prepared by taking the reductive tetrahydroxy quaternary ammonium salt as a raw material has dual functions of a low-temperature activator and a clay stabilizer, and can be used for low-temperature reservoir fracturing transformation.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a reducing tetrahydroxyquaternary ammonium salt, its preparation method and application, and a low-temperature reservoir fracturing fluid additive. Background Technology

[0002] Currently, the cost of low-temperature (≤50℃) reservoir fracturing is relatively high, mainly due to the limited use of polymer emulsions. Under low-temperature conditions, polymer emulsions suffer from problems such as long gel breaking time, incomplete gel breaking, low flowback efficiency, and low flowback rate, which may cause secondary damage to the reservoir. Simultaneously, during water injection and acid fracturing in oilfields, if the formation contains a certain amount of clay minerals, these clay minerals will undergo irreversible expansion and migration upon contact with water-based fracturing fluids, causing pore throat blockage and decreased reservoir permeability, severely damaging low-permeability reservoirs and significantly impacting crude oil recovery efficiency. To protect the permeability of oil and gas formations, chemical treatment agents must be used to stabilize the clay minerals in the formation. Therefore, clay stabilizers are usually added to the well fluid to prevent clay hydration expansion and dispersion migration. Typically, clay particles carry a negative charge, while the cations in the clay stabilizer carry a positive charge. The two generate a strong adsorption effect through electrostatic attraction, delaying water molecule penetration and preventing the hydration expansion of clay particles, thus inhibiting its expansion.

[0003] Chinese patent document CN 110437818 A discloses a cleaving activator suitable for reservoir fracturing at 20-50℃, which is a soluble Ag ion complex. The preparation method of this low-temperature cleaving activator is as follows: ligand A or B is dissolved in a methanol-water solution containing 60-75% methanol by mass, heated to 50-70℃, the pH is adjusted to 4-5, AgNO3 is added, stirred evenly, and the pH is adjusted to 7-8 with ammonia water to obtain the activator. The mass percentage of ligand A or B in the methanol-water solution is 20-35%, and the mass percentage of AgNO3 in the methanol-water solution is 3-5%. This invention provides a low-temperature cleaving activator that can activate the cleaving reaction of (NH4)2S2O8 in low-temperature reservoirs at 20-50℃; however, it uses toxic and hazardous materials such as methanol and ammonia water, and AgNO3 is expensive.

[0004] Chinese patent document CN 114106795 A discloses a clay stabilizer, its preparation method, and its application. This clay stabilizer, by weight, comprises: 2-8 parts of a bisindolemethane compound, 2-8 parts of a quinazolinone compound, 5-15 parts of methanol, and 80-85 parts of water. The clay stabilizer has a small molecular weight, which facilitates dispersion on the clay surface, resulting in high anti-swelling efficiency. Furthermore, the clay stabilizer is easily discharged, reducing residue and damage to the formation after fracturing or mining operations. Although the clay stabilizer in this patent contains nitrogen, its molecular structure lacks cations, limiting its adsorption effect on negatively charged clay and thus affecting its anti-swelling effect.

[0005] In summary, existing fracturing fluid additives have a single function and cannot simultaneously function as both low-temperature activators and clay stabilizers. Therefore, developing a fracturing fluid additive that combines the functions of a low-temperature activator and a clay stabilizer is of significant practical importance for the widespread application of polymer emulsion fracturing fluids in low-temperature reservoir fracturing and for cost reduction and efficiency improvement in oilfield development. Summary of the Invention

[0006] This invention provides a reduced tetrahydroxyquaternary ammonium salt and its preparation method, which overcomes the shortcomings of the prior art. It can effectively solve the problem that existing fracturing fluid additives have a single function and cannot simultaneously achieve the functions of low-temperature activator and clay stabilizer.

[0007] One of the technical solutions of the present invention is achieved through the following measures: a reducing tetrahydroxyquaternary ammonium salt is prepared by the following steps:

[0008] The first step is to dissolve the required amount of 2,3-epoxypropyltrimethylammonium chloride in water to obtain a reaction solution;

[0009] The second step involves purging the reaction solution with nitrogen to remove oxygen, then adding the required amount of hydroxylamine hydrochloride to obtain a reaction mixture. After the reaction, an aqueous solution of reduced tetrahydroxyquaternary ammonium salt is obtained.

[0010] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0011] The chemical structural formula of the above-mentioned reducing tetrahydroxyquaternary ammonium salt is:

[0012]

[0013] In the second step above, the total mass fraction of the reactants 2,3-epoxypropyltrimethylammonium chloride and hydroxylamine hydrochloride in the reaction mixture is 40% to 60%.

[0014] The molar ratio of 2,3-epoxypropyltrimethylammonium chloride to hydroxylamine hydrochloride is (3.0 to 3.3):1.

[0015] In the second step above, the reaction temperature is between 15°C and 35°C.

[0016] In the second step mentioned above, the reaction time is 4 to 12 hours.

[0017] The second technical solution of the present invention is achieved through the following measures: a method for preparing a reducing tetrahydroxyquaternary ammonium salt, comprising the following steps:

[0018] The first step is to dissolve the required amount of 2,3-epoxypropyltrimethylammonium chloride in water to obtain a reaction solution;

[0019] The second step involves purging the reaction solution with nitrogen to remove oxygen, then adding the required amount of hydroxylamine hydrochloride to obtain a reaction mixture. After the reaction, an aqueous solution of reduced tetrahydroxyquaternary ammonium salt is obtained.

[0020] The third technical solution of the present invention is achieved through the following measures: the application of a reducing tetrahydroxyquaternary ammonium salt in fracturing fluid additives.

[0021] The fourth technical solution of the present invention is achieved through the following measures: a low-temperature reservoir fracturing fluid additive, wherein the raw materials, by mass parts per hundred parts, consist of: 60 to 90 parts of an aqueous solution of reduced tetrahydroxyquaternary ammonium salt, 0 to 5 parts of diethylhydroxylamine hydrochloride, and 0 to 10 parts of salts, with the remainder being water, wherein the salts are potassium salts or ammonium salts.

[0022] The following are further optimizations and / or improvements to the fourth technical solution of the invention described above:

[0023] The potassium salts mentioned above are one or both of potassium chloride and potassium formate.

[0024] The above-mentioned ammonium salts are one or more of ammonium chloride, ammonium sulfate, ammonium formate, and ammonium oxalate.

[0025] This invention provides a reduced tetrahydroxy-4-quaternary ammonium salt, its preparation method, and a low-temperature reservoir fracturing fluid additive. The reduced tetrahydroxy-4-quaternary ammonium salt of this invention exhibits high reducing power and contains four cations and four hydroxyl groups, resulting in strong polarity. It also features a small molecular weight and high charge density. The low-temperature reservoir fracturing fluid additive prepared using the reduced tetrahydroxy-4-quaternary ammonium salt of this invention functions as both a low-temperature activator and a clay stabilizer, and can be used for low-temperature reservoir fracturing stimulation. Detailed Implementation

[0026] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solution of this invention and the actual situation. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; room temperature in this invention generally refers to a temperature between 15°C and 25°C, and is generally defined as 25°C.

[0027] The present invention will be further described below with reference to embodiments:

[0028] Example 1: The reduced tetrahydroxyquaternary ammonium salt was prepared according to the following steps:

[0029] The first step is to dissolve the required amount of 2,3-epoxypropyltrimethylammonium chloride in water to obtain a reaction solution;

[0030] The second step involves purging the reaction solution with nitrogen to remove oxygen, then adding the required amount of hydroxylamine hydrochloride to obtain a reaction mixture. After the reaction, an aqueous solution of reduced tetrahydroxyquaternary ammonium salt is obtained.

[0031] Example 2: The chemical structural formula of this reducing tetrahydroxyquaternary ammonium salt is as follows:

[0032]

[0033] Example 3: As an optimization of the above example, in the second step, the total mass fraction of the reactants 2,3-epoxypropyltrimethylammonium chloride and hydroxylamine hydrochloride in the reaction mixture is 40% to 60%.

[0034] Example 4: As an optimization of the above example, the molar ratio of 2,3-epoxypropyltrimethylammonium chloride to hydroxylamine hydrochloride is (3.0 to 3.3):1.

[0035] Example 5: As an optimization of the above example, in the second step, the reaction temperature is 15°C to 35°C.

[0036] Example 6: As an optimization of the above example, in the second step, the reaction time is 4h to 12h.

[0037] The chemical reaction process for preparing the reduced tetrahydroxyquaternary ammonium salt is as follows:

[0038]

[0039] Example 7: Application of the reduced tetrahydroxyquaternary ammonium salt in cryogenic reservoir fracturing fluid additives.

[0040] Example 8: The raw materials of this low-temperature reservoir fracturing fluid additive are composed of the following components per 100 parts by mass: 60 to 90 parts of an aqueous solution of reduced tetrahydroxyquaternary ammonium salt, 0 to 5 parts of diethylhydroxylamine hydrochloride, and 0 to 10 parts of salts, with the remainder being water, wherein the salts are potassium salts or ammonium salts.

[0041] Example 9: As an optimization of the above examples, the potassium salt is one or both of potassium chloride and potassium formate.

[0042] Example 10: As an optimization of the above examples, the ammonium salt is one or more of ammonium chloride, ammonium sulfate, ammonium formate, and ammonium oxalate.

[0043] The water used in the preparation or formulation of the reducing dihydroxy bis-quaternary ammonium salt and the low-temperature reservoir fracturing fluid additive of the present invention can be tap water.

[0044] Example 11:

[0045] Preparation of aqueous solution of reduced tetrahydroxyquaternary ammonium salt:

[0046] 3 mol of 2,3-epoxypropyltrimethylammonium chloride was dissolved in an appropriate amount of tap water to obtain a reaction solution; nitrogen gas was bubbled through the reaction solution to remove oxygen for 15 min, and 1 mol of hydroxylamine hydrochloride was added to obtain a reaction mixture; the reaction was carried out at room temperature for 12 h to obtain an aqueous solution of reduced tetrahydroxyquaternary ammonium salt, and the total mass fraction of reactants in the reaction mixture was 60%.

[0047] Preparation of low-temperature reservoir fracturing fluid additives:

[0048] A mixture of 90 parts of a reduced tetrahydroxyquaternary ammonium salt aqueous solution, 5 parts of diethylhydroxyamine hydrochloride, and 5 parts of ammonium formate was homogeneous to obtain a low-temperature reservoir fracturing fluid additive.

[0049] Example 12:

[0050] Preparation of aqueous solution of reduced tetrahydroxyquaternary ammonium salt:

[0051] Dissolve 3 mol of 2,3-epoxypropyltrimethylammonium chloride in an appropriate amount of tap water to obtain a reaction solution; purge the reaction solution with nitrogen gas for 15 min to remove oxygen, then add 1 mol of hydroxylamine hydrochloride to obtain a reaction mixture; react at room temperature for 8 h to obtain a solution of reduced tetrahydroxyquaternary ammonium salt, with a total mass fraction of 50% reactants in the reaction mixture.

[0052] Preparation of low-temperature reservoir fracturing fluid additives:

[0053] A low-temperature reservoir fracturing fluid additive was obtained by mixing 80 parts of a reduced tetrahydroxyquaternary ammonium salt aqueous solution, 5 parts of diethylhydroxylamine hydrochloride, 2.5 parts of ammonium formate, 2.5 parts of potassium formate, and 10 parts of tap water evenly.

[0054] Example 13:

[0055] Preparation of aqueous solution of reduced tetrahydroxyquaternary ammonium salt:

[0056] 3.1 mol of 2,3-epoxypropyltrimethylammonium chloride was dissolved in an appropriate amount of tap water to obtain a reaction solution; nitrogen gas was bubbled through the reaction solution to remove oxygen for 15 min, and 1 mol of hydroxylamine hydrochloride was added to obtain a reaction mixture; the reaction was carried out at room temperature for 6 h to obtain an aqueous solution of reduced tetrahydroxyquaternary ammonium salt, and the total mass fraction of reactants in the reaction mixture was 50%.

[0057] Preparation of low-temperature reservoir fracturing fluid additives:

[0058] A mixture of 70 parts of a reduced tetrahydroxyquaternary ammonium salt aqueous solution, 2 parts of diethylhydroxylamine hydrochloride, 10 parts of ammonium formate, and 18 parts of tap water was prepared to obtain a low-temperature reservoir fracturing fluid additive.

[0059] Example 14:

[0060] Preparation of reducing tetrahydroxyquaternary ammonium aqueous solution salt:

[0061] 3.3 mol of 2,3-epoxypropyltrimethylammonium chloride was dissolved in an appropriate amount of tap water to obtain a reaction solution; nitrogen gas was bubbled through the reaction solution to remove oxygen for 15 min, and 1 mol of hydroxylamine hydrochloride was added to obtain a reaction mixture; the reaction was carried out at room temperature for 6 h to obtain an aqueous solution of reduced tetrahydroxyquaternary ammonium salt, and the total mass fraction of reactants in the reaction mixture was 40%.

[0062] Preparation of low-temperature reservoir fracturing fluid additives:

[0063] A mixture of 60 parts of a reduced tetrahydroxyquaternary ammonium salt aqueous solution, 1 part of diethylhydroxylamine hydrochloride, and 39 parts of tap water was prepared to obtain a low-temperature reservoir fracturing fluid additive.

[0064] In Examples 11 to 14 of this invention, all the parts of raw materials are parts by mass.

[0065] Performance testing:

[0066] The low-temperature reservoir fracturing fluid additives prepared in Examples 11 to 14 were combined with industrial-grade ammonium persulfate in a certain proportion to form a breaker. The breaker time, breaker fluid viscosity, and breaker fluid anti-swelling rate were tested. The specific operation was as follows:

[0067] 500 mL of a 0.6% (w / w) polymer emulsion fracturing fluid (provided by Xinjiang Zhongxing Technology) was prepared and placed in a constant-temperature water bath at the test temperature for 30 min. The initial viscosity was tested (see Table 1). A certain amount of ammonium persulfate was added and stirred until homogeneous. Then, the low-temperature reservoir fracturing fluid additives prepared in Examples 11 to 14 were added and stirred again until homogeneous, yielding the test fracturing fluid. The test fracturing fluid was then placed back into the corresponding constant-temperature water bath. Fracturing was considered complete when the viscosity of the test fracturing fluid was less than or equal to 5 mPa·s. The anti-swelling rate of the test fracturing fluid was tested, and the results are shown in Table 1. As shown in Table 1, when the dosages of ammonium persulfate (0.1%) and fracturing fluid additive (0.4%) are relatively high, the breaking temperature of the 0.6% polymer emulsion can be as low as 5°C; at 25°C, the dosage of ammonium persulfate is only 0.03%, which is significantly lower than that of existing breaking systems; at 50°C, the dosage of ammonium persulfate is only 0.02%, and the dosage of fracturing fluid additive is only 0.05%; at the same time, the breaking fluid has a good anti-swelling effect. Therefore, the low-temperature reservoir fracturing fluid additive described in this invention has excellent effects and is suitable for low-temperature reservoir fracturing fluid stimulation.

[0068] The present invention has the following beneficial effects:

[0069] (1) The reducing tetrahydroxyquaternary ammonium salt and low-temperature reservoir fracturing fluid additive of the present invention are simple to prepare, the reaction process is safe and controllable, and they are suitable for large-scale production.

[0070] (2) The low-temperature reservoir fracturing fluid additive of the present invention can meet the timely gel breaking requirements and ensure the sand carrying performance of the fracturing fluid. It can be used for low-temperature and low-to-ultra-low-permeability reservoir fracturing construction.

[0071] (3) The low-temperature reservoir fracturing fluid additive of the present invention has good anti-swelling properties and significantly prevents clay swelling.

[0072] (4) The low-temperature reservoir fracturing fluid additive of the present invention has a small molecular weight of each component, which will not cause secondary damage to the reservoir.

[0073] In summary, this invention provides a reduced tetrahydroxy-4-quaternary ammonium salt and its preparation method. This reduced tetrahydroxy-4-quaternary ammonium salt is a strongly polar molecule containing four cations and four hydroxyl groups. It has a small molecular weight, high charge density, strong water-washing resistance, and significant anti-clay swelling effect, meeting the requirements for timely gel breaking. Furthermore, it exhibits good compatibility with slickwater and emulsion fracturing fluids, ensuring the proppant-carrying capacity of the fracturing fluid. The low-temperature reservoir fracturing fluid additive using this reduced tetrahydroxy-4-quaternary ammonium salt as a raw material simultaneously functions as a low-temperature gel breaking activator and a clay stabilizer. This ensures effective gel breaking of the polymer emulsion under low-temperature conditions, reduces the viscosity and residue content of the gel breaking fluid, and ensures efficient flowback after fracturing stimulation. Simultaneously, it effectively prevents clay hydration swelling and dispersion migration during the stimulation process, and can be used in low-permeability and ultra-low-permeability reservoir fracturing operations.

[0074] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0075] Table 1

[0076]

Claims

1. A reducing tetrahydroxyquaternary ammonium salt, characterized in that... Prepared according to the following steps: The first step is to dissolve the required amount of 2,3-epoxypropyltrimethylammonium chloride in water to obtain a reaction solution; The second step involves purging the reaction solution with nitrogen to remove oxygen, then adding the required amount of hydroxylamine hydrochloride to obtain a reaction mixture. After the reaction, an aqueous solution of reduced tetrahydroxyquaternary ammonium salt is obtained.

2. The reducing tetrahydroxyquaternary ammonium salt according to claim 1, characterized in that... The chemical structural formula is:

3. The reducing tetrahydroxyquaternary ammonium salt according to claim 1 or 2, characterized in that... In the second step, the total mass fraction of the reactants 2,3-epoxypropyltrimethylammonium chloride and hydroxylamine hydrochloride in the reaction mixture is 40% to 60%.

4. The reducing tetrahydroxyquaternary ammonium salt according to any one of claims 1 to 3, characterized in that... The molar ratio of 2,3-epoxypropyltrimethylammonium chloride to hydroxylamine hydrochloride is 3.0 to 3.3:

1.

5. The reducing tetrahydroxyquaternary ammonium salt according to any one of claims 1 to 4, characterized in that... In the second step, the reaction temperature is between 15°C and 35°C.

6. The reducing tetrahydroxyquaternary ammonium salt according to any one of claims 2 to 5, characterized in that... In the second step, the reaction time is 4 to 12 hours.

7. A method for preparing a reducing tetrahydroxyquaternary ammonium salt according to any one of claims 1 to 6, characterized in that... Follow these steps: The first step is to dissolve the required amount of 2,3-epoxypropyltrimethylammonium chloride in water to obtain a reaction solution; The second step involves purging the reaction solution with nitrogen to remove oxygen, then adding the required amount of hydroxylamine hydrochloride to obtain a reaction mixture. After the reaction, an aqueous solution of reduced tetrahydroxyquaternary ammonium salt is obtained.

8. The application of the reduced tetrahydroxyquaternary ammonium salt according to any one of claims 1 to 6 in fracturing fluid additives.

9. A low-temperature reservoir fracturing fluid additive using the reduced tetrahydroxyquaternary ammonium salt as a raw material according to any one of claims 1 to 6, characterized in that... The raw materials, by mass, consist of 60 to 90 parts of an aqueous solution of reduced tetrahydroxyquaternary ammonium salt, 0 to 5 parts of diethylhydroxylamine hydrochloride, and 0 to 10 parts of salts, with the remainder being water; wherein the salts are potassium salts or ammonium salts.

10. The cryogenic reservoir fracturing fluid additive according to claim 9, characterized in that... The potassium salt is one or both of potassium chloride and potassium formate; or / and the ammonium salt is one or more of ammonium chloride, ammonium sulfate, ammonium formate, and ammonium oxalate.

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