Multifunctional composite additive for fracturing and preparation method thereof

Abstract

The invention relates to the technical field of oilfield chemical reagents, and provides a multifunctional composite additive for fracturing and a preparation method thereof.The multifunctional composite additive for fracturing is prepared from, by weight, 10%-15% of a surfactant, 2%-10% of a demulsifier, 3%-5% of ammonium chloride, 0%-1% of nano-silica, 10%-20% of an organic solvent and the balance water; the surfactant is composed of a cationic surfactant, an anionic surfactant and a nonionic surfactant according to a mass ratio of 1: 1.5: 2-2.2, the cationic surfactant is a dimethyl benzyl quaternary ammonium salt cationic surfactant, the alkyl chain length is 14-16, the anionic surfactant is a sulfonate anionic surfactant, and the alkyl chain length is 9-12. According to the technical scheme, the problem that the surface tension reduction performance is poor in the application process of the multifunctional composite additive for fracturing in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemical reagents, in particular to a multifunctional composite additive for fracturing and a preparation method thereof. Background Art

[0002] During the fracturing process, the performance of the fracturing fluid plays a key role in the fracturing effect. As an important component of the fracturing fluid, the optimization and improvement of the performance of the multifunctional composite additives for fracturing has always been the focus of research.

[0003] In fracturing fluid systems, surface tension is one of the important factors affecting the fracturing effect. In order to further reduce surface tension and promote the penetration and flowback of fracturing fluid in the formation, composite surfactants are often added. Composite surfactants are composed of cationic surfactants, anionic surfactants, and nonionic surfactants. Through the synergistic effect of different types of surfactants, they can more effectively reduce surface tension and improve the performance of fracturing fluids. However, when cationic surfactants and anionic surfactants are combined, precipitation is easily generated due to the electrostatic interaction between them. This not only reduces the effective concentration of the surfactants and affects the surface tension reduction effect, but may also clog the formation pores, damage the formation, and cause a series of adverse problems.

[0004] Therefore, it is necessary to develop a multifunctional composite additive for fracturing that can effectively reduce surface tension. Summary of the Invention

[0005] The present invention provides a multifunctional composite additive for fracturing and a preparation method thereof, which solves the problem in the related art that the multifunctional composite additive for fracturing has poor performance in reducing surface tension during application.

[0006] The technical solution of the present invention is as follows: The present invention proposes a multifunctional composite additive for fracturing, which is composed of the following raw materials in weight percentage: 10% to 15% surfactant, 2% to 10% demulsifier, 3% to 5% ammonium chloride, 0% to 1% nano-silica, 10% to 20% organic solvent, and the balance is water; the surfactant is composed of a cationic surfactant, an anionic surfactant, and a nonionic surfactant in a mass ratio of 1:1.5:2 to 2.2, the cationic surfactant is a dimethylbenzyl quaternary ammonium salt cationic surfactant with an alkyl chain length of 14 to 16, and the anionic surfactant is a sulfonate anionic surfactant with an alkyl chain length of 9 to 12.

[0007] As a further technical solution, the dimethylbenzyl quaternary ammonium salt cationic surfactant includes one or both of tetradecyldimethylbenzylammonium chloride and hexadecyldimethylbenzylammonium chloride, preferably hexadecyldimethylbenzylammonium chloride.

[0008] In the present invention, a dimethylbenzyl quaternary ammonium salt cationic surfactant has a positively charged quaternary ammonium salt group at one end and an alkyl chain of a certain length at the other end, so that the cationic surfactant can be quickly and directionally adsorbed on the surface or interface of the solution in the fracturing fluid system, effectively reducing the surface tension. As the fracturing fluid flows and contacts the formation rock, the cationic surfactant molecules migrate to and adsorb on the surface of the fracturing fluid or the interface formed with the rock. The cationic portion combines with the negatively charged rock surface through electrostatic attraction, thereby improving the wetting performance of the fracturing fluid on the rock surface and reducing the surface tension.

[0009] As a further technical solution, the sulfonate anionic surfactant includes one or both of sodium dodecyl sulfonate and sodium n-nonane sulfonate, preferably sodium dodecyl sulfonate.

[0010] In the present invention, the molecular structure of the sulfonate anionic surfactant has a hydrophilic sulfonate ion at one end and a hydrophobic alkyl chain at the other end. In addition to effectively reducing surface tension during the fracturing process, it also has good salt resistance. In actual fracturing formations, various salt substances are often present. The sulfonate ion is relatively stable and is not easy to precipitate with metal ions. The activity of the surfactant can be maintained even in a high salt concentration environment. This allows the fracturing fluid containing the sulfonate anionic surfactant to maintain good performance under complex formation conditions, ensure the smooth progress of the fracturing operation, and improve the stability of the fracturing fluid system.

[0011] As a further technical solution, the demulsifier includes one or both of demulsifier TR2030 and demulsifier SP169.

[0012] In the present invention, the addition of the demulsifier can quickly destroy the stability of the oil-water emulsion formed after the fracturing operation. The demulsifier molecules can be quickly adsorbed on the oil-water interface, reducing the strength and elasticity of the interfacial film, destroying the integrity of the interfacial film, promoting oil-water separation, and improving the efficiency of subsequent crude oil extraction and fracturing fluid treatment.

[0013] As a further technical solution, the organic solvent includes one or more of ethanol, isopropanol, and n-butanol.

[0014] In the present invention, ethanol, isopropanol, and n-butanol all have strong solubility and can effectively dissolve various components in the fracturing additive. In addition, ethanol, isopropanol, and n-butanol have good miscibility with water and can form a stable mixed solvent system with water, which helps to maintain the uniformity and stability of the fracturing fluid system and prevent stratification or precipitation during storage and use.

[0015] As a further technical solution, the nonionic surfactant includes one or both of AEO-3 and AEO-9.

[0016] In the present invention, the nonionic surfactant can adjust the hydrophilicity and hydrophobicity balance of the cationic and anionic surfactants in the fracturing fluid. Since there are no ionic groups in the nonionic surfactant molecules, but they interact with water molecules through polar groups such as hydroxyl groups and ether bonds, the surface activity of the entire surfactant system can be optimized. In addition, the molecular structure of the nonionic surfactant is relatively stable and is not easily affected by high temperature and decomposed or ineffective. It can maintain surface activity at high temperatures and continue to play the role of reducing surface tension and stabilizing the system.

[0017] As a further technical solution, when the mass percentage of nano-silica in the raw material composition is 0.5% to 1%, the nano-silica is composite nano-silica, and the raw materials of the composite nano-silica include 5-methoxybenzimidazole-2-carboxylic acid and nano-silica in a mass ratio of 2 to 3:30; 5-methoxybenzimidazole-2-carboxylic acid can be replaced with 1H-benzimidazole-2-carboxylic acid or 1H-imidazole-4-carboxylic acid, preferably 5-methoxybenzimidazole-2-carboxylic acid.

[0018] In the present invention, nano-silica has an extremely high specific surface area and surface activity, can be adsorbed on the rock surface, change the wettability of the rock surface, reduce the retention of liquid in the pores and cracks of the rock, reduce the damage to the permeability of the formation, and is conducive to the smooth production of oil and gas; after 5-methoxybenzimidazole-2-carboxylic acid is composited with nano-silica, the surface of the composite nano-silica has more active groups, which can not only promote the dispersibility of nano-silica and effectively prevent the aggregation and precipitation of solid particles, but also can be more effectively adsorbed on the rock surface, change the charge distribution and hydrophilic and lipophilic properties of the rock surface, and thus promote the improvement of the drainage rate.

[0019] As a further technical solution, the preparation method of the composite nano-silica comprises the following steps: dispersing 5-methoxybenzimidazole-2-carboxylic acid in ethanol, adding nano-silica, mixing and drying to obtain the composite nano-silica.

[0020] As a further technical solution, the mass ratio of the ethanol to the nano-silicon dioxide is 1 to 5:1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, and preferably 3:1.

[0021] As a further technical solution, the mixing time is 2 hours.

[0022] As a further technical solution, the particle size of the nano-silicon dioxide is 20-100 nm, for example, 20 nm, 50 nm, 100 nm, preferably 50 nm.

[0023] In the present invention, the particle size of the nano-silica is 20 to 100 nm. Within this particle size range, the specific surface area of the particles is relatively large and the surface energy is high. Therefore, the particles per unit mass have more surface atoms and active sites, and can provide stronger adsorption capacity when in contact with the rock surface or other substances. This prevents the nano-silica particles from being too large and possibly causing blockage when entering the pores and cracks of the formation, thereby negatively affecting the permeability of the formation. It also prevents the particles from being too active due to being too small, easily agglomerated or carried away by the fluid, and unable to function effectively.

[0024] The present invention also provides a method for preparing a multifunctional composite additive for fracturing, which comprises the following steps: S1. Add ammonium chloride to water, dissolve it, then add cationic surfactant and nonionic surfactant, disperse them evenly, and obtain a mixed solution; S2. Add the remaining raw materials to the mixed solution and stir evenly to obtain a multifunctional composite additive.

[0025] The working principle and beneficial effects of the present invention are: In the prior art, in order to further reduce the surface tension, the form of composite surfactants is often used, but the negative effects caused by the precipitation generated by the interaction between surfactants are ignored. In the present invention, cationic surfactants, anionic surfactants and nonionic surfactants are used in combination, wherein the nonionic surfactant has an uncharged molecular structure that can form a physical barrier between the anionic and cationic surfactant molecules, weakening the electrostatic attraction between the two through the steric hindrance effect. The cationic surfactant is a dimethylbenzyl quaternary ammonium salt cationic surfactant with an alkyl chain length of 14 to 16, and the anionic surfactant is a sulfonate anionic surfactant with an alkyl chain length of 9 to 12. The dimethylbenzyl in the cationic surfactant has a certain spatial structure, which can provide a certain steric hindrance when the cationic surfactant and the anionic surfactant interact with each other through electrostatic interaction, so that the cationic surfactant and the anionic surfactant can interact with each other through electrostatic interaction. When combined, the surfactants will not aggregate too tightly, thus avoiding the formation of large aggregates and precipitation. The long alkyl chains of the cationic surfactants have strong hydrophobicity, while the short alkyl chains of the anionic surfactants have relatively weak hydrophobicity. The difference in hydrophobicity enables the surfactant molecules to combine and disperse in a more stable manner, thus reducing the possibility of precipitation. In the present invention, the dimethylbenzyl quaternary ammonium salt cationic surfactant has an alkyl chain length of 14 to 16, and the anionic surfactant is a sulfonate anionic surfactant with an alkyl chain length of 9 to 12. The combination of the two reduces the generation of precipitation, enables the composite surfactant molecules to be more freely and evenly adsorbed and arranged on the solution surface, optimizes the structure of the surface adsorption layer, and further reduces the surface tension of the multifunctional composite additive. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] In the following examples and comparative examples: Nano-silicon dioxide: particle size is 50nm.

[0028] Example 1 The multifunctional composite additive for fracturing is composed of the following raw materials in percentage by weight: 10% surfactant, 2% demulsifier TR2030, 3% ammonium chloride, 10% ethanol, 0.5% nano-silicon dioxide, and the balance water; The surfactant is composed of hexadecyldimethylbenzyl ammonium chloride, sodium lauryl sulfonate and AEO-3 in a mass ratio of 1:1.5:2; A method for preparing a multifunctional composite additive for fracturing comprises the following steps: S1. Add ammonium chloride to water, dissolve it, then add hexadecyldimethylbenzyl ammonium chloride and AEO-3, disperse them evenly, and obtain a mixed solution; S2. Add the remaining raw materials to the mixed solution and stir evenly to obtain a multifunctional composite additive.

[0029] Example 2 A multifunctional composite additive for fracturing, comprising the following raw materials in percentage by weight: 12% surfactant, 6% demulsifier TR2030, 4% ammonium chloride, 15% isopropyl alcohol, 0.8% nano-silicon dioxide, and the balance being water; The surfactant is composed of hexadecyldimethylbenzyl ammonium chloride, sodium lauryl sulfonate and AEO-3 in a mass ratio of 1:1.5:2; A method for preparing a multifunctional composite additive for fracturing comprises the following steps: S1. Add ammonium chloride to water, dissolve it, then add hexadecyldimethylbenzyl ammonium chloride and AEO-3, disperse them evenly, and obtain a mixed solution; S2. Add the remaining raw materials to the mixed solution and stir evenly to obtain a multifunctional composite additive.

[0030] Example 3 A multifunctional composite additive for fracturing, comprising the following raw materials in percentage by weight: 15% surfactant, 10% demulsifier SP169, 5% ammonium chloride, 20% n-butanol, 1.0% nano-silicon dioxide, and the balance being water; The surfactant is composed of hexadecyldimethylbenzyl ammonium chloride, sodium lauryl sulfate and AEO-9 in a mass ratio of 1:1.5:2; A method for preparing a multifunctional composite additive for fracturing comprises the following steps: S1. Add ammonium chloride to water, dissolve it, then add hexadecyldimethylbenzyl ammonium chloride and AEO-3, disperse them evenly, and obtain a mixed solution; S2. Add the remaining raw materials to the mixed solution and stir evenly to obtain a multifunctional composite additive.

[0031] Example 4 Compared with Example 3, the difference of Example 4 is that the surfactant consists of hexadecyldimethylbenzyl ammonium chloride, sodium lauryl sulfate and AEO-9 in a mass ratio of 1:1.5:2.2.

[0032] Example 5 The preparation method of composite nano-silica comprises the following steps: dispersing 2 parts of 5-methoxybenzimidazole-2-carboxylic acid in 90 parts of ethanol, adding 30 parts of nano-silica, mixing for 2 hours and then drying to obtain composite nano-silica; Compared with Example 4, Example 5 is different in that the nano-silica is replaced by an equal amount of composite nano-silica obtained by the above preparation method.

[0033] Example 6 Compared with Example 5, the difference in Example 6 is that the amount of 5-methoxybenzimidazole-2-carboxylic acid added is 3 parts.

[0034] Example 7 Compared with Example 6, Example 7 is different in that 5-methoxybenzimidazole-2-carboxylic acid is replaced by an equal amount of 1H-benzimidazole-2-carboxylic acid.

[0035] Example 8 Compared with Example 6, Example 8 is different in that 5-methoxybenzimidazole-2-carboxylic acid is replaced by an equal amount of 1H-imidazole-4-carboxylic acid.

[0036] Comparative Example 1 Compared with Example 3, the difference in Comparative Example 1 is that the surfactant consists of hexadecyldimethylbenzyl ammonium chloride and AEO-9 in a mass ratio of 1:2.

[0037] Comparative Example 2 Compared with Example 3, the difference in Comparative Example 2 is that the surfactant consists of sodium lauryl sulfate and AEO-9 in a mass ratio of 1.5:2.

[0038] Comparative Example 3 Compared with Example 3, the difference of Comparative Example 3 is that the surfactant consists of hexadecyldimethylbenzyl ammonium chloride and sodium dodecylsulfonate in a mass ratio of 1:1.5.

[0039] Comparative Example 4 Compared with Example 3, the difference of Comparative Example 4 is that hexadecyldimethylbenzylammonium chloride is replaced by an equal amount of hexadecyltrimethylammonium chloride.

[0040] Comparative Example 5 Compared with Example 3, the difference in Comparative Example 5 is that hexadecyldimethylbenzylammonium chloride is replaced by an equal amount of octadecyldimethylbenzylammonium chloride.

[0041] Comparative Example 6 Compared with Example 3, the difference in Comparative Example 6 is that hexadecyldimethylbenzylammonium chloride is replaced by an equal amount of dodecyldimethylbenzylammonium chloride.

[0042] Comparative Example 7 Compared with Example 3, the difference in Comparative Example 7 is that sodium dodecylsulfonate is replaced by an equal amount of sodium dodecylbenzenesulfonate.

[0043] Comparative Example 8 Compared with Example 3, the difference in Comparative Example 8 is that sodium dodecyl sulfonate is replaced by an equal amount of sodium 1-octane sulfonate.

[0044] Comparative Example 9 Compared with Example 3, the difference in Comparative Example 9 is that sodium lauryl sulfate is replaced by an equal amount of sodium hexadecyl sulfate.

[0045] Experimental Example 1 The multifunctional composite additives prepared in Examples 1 to 4 and Comparative Examples 1 to 9 were tested for surface tension according to the test method specified in SY / T 5755-2016 "Performance Evaluation Method of Discharge Aids for Fracturing and Acidizing", using the ring method.

[0046] The test results are shown in Table 1: Table 1 Performance test results of the multifunctional composite additives prepared in Examples 1 to 4 and Comparative Examples 1 to 9

[0047] It can be seen from Table 1 that when the surfactant is composed of a cationic surfactant, an anionic surfactant and a nonionic surfactant in a mass ratio of 1:1.5:2~2.2, and the cationic surfactant is a dimethylbenzyl quaternary ammonium salt cationic surfactant with an alkyl chain length of 14~16, and the anionic surfactant is a sulfonate anionic surfactant with an alkyl chain length of 9~12, the surface tension of the multifunctional composite additive during the application process can be further reduced.

[0048] Experimental Example 2 The multifunctional composite additives prepared in Examples 4 to 8 were tested for drainage rates according to the test method specified in SY / T 5755-2016 "Performance Evaluation Method of Drainage Agents for Fracturing and Acidizing", and the test method was Method 2.

[0049] The test results are shown in Table 2: Table 2 Performance test results of the multifunctional composite additives prepared in Examples 4 to 8

[0050] It can be seen from Table 2 that when composite nano-silica is added, the drainage rate of the multifunctional composite additive during the application process can be further improved.

[0051] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multifunctional composite additive for fracturing, characterized in that: The invention is composed of the following raw materials in percentage by weight: 10% to 15% of a surfactant, 2% to 10% of an emulsifier, 3% to 5% of ammonium chloride, 0% to 1% of nano-silicon dioxide, 10% to 20% of an organic solvent, and the balance being water; the surfactant comprises a cationic surfactant, an anionic surfactant, and a nonionic surfactant in a mass ratio of 1:1.5:2-2.2, the cationic surfactant is a dimethylbenzyl quaternary ammonium salt cationic surfactant with an alkyl chain length of 14-16, and the anionic surfactant is a sulfonate anionic surfactant with an alkyl chain length of 9-12.

2. The multifunctional composite additive for fracturing according to claim 1, characterized in that: The dimethylbenzyl quaternary ammonium salt cationic surfactant includes one or both of tetradecyldimethylbenzylammonium chloride and hexadecyldimethylbenzylammonium chloride.

3. The multifunctional composite additive for fracturing according to claim 1, characterized in that: The sulfonate anionic surfactant includes one or both of sodium dodecylsulfonate and sodium n-nonanesulfonate.

4. The multifunctional composite additive for fracturing according to claim 1, characterized in that: The demulsifier includes one or both of demulsifier TR2030 and demulsifier SP169.

5. The multifunctional composite additive for fracturing according to claim 1, characterized in that: The organic solvent includes one or more of ethanol, isopropanol, and n-butanol.

6. The multifunctional composite additive for fracturing according to claim 1, characterized in that: The nonionic surfactant includes one or both of AEO-3 and AEO-9.

7. The multifunctional composite additive for fracturing according to claim 1, characterized in that: When the mass percentage of nano-silicon dioxide in the raw material composition is 0.5% to 1%, the nano-silicon dioxide is composite nano-silicon dioxide, and the raw materials of the composite nano-silicon dioxide include 5-methoxybenzimidazole-2-carboxylic acid and nano-silicon dioxide in a mass ratio of 2 to 3:

30.

8. The multifunctional composite additive for fracturing according to claim 7, characterized in that: The preparation method of the composite nano-silica comprises the following steps: dispersing 5-methoxybenzimidazole-2-carboxylic acid in ethanol, adding nano-silica, mixing and drying to obtain the composite nano-silica.

9. The multifunctional composite additive for fracturing according to claim 7, characterized in that: The particle size of the nano-silicon dioxide is 20-100 nm.

10. A method for preparing a multifunctional composite additive for fracturing, for preparing the multifunctional composite additive for fracturing according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Add ammonium chloride to water, dissolve it, then add cationic surfactant and nonionic surfactant, disperse them evenly, and obtain a mixed solution; S2. Add the remaining raw materials to the mixed solution and stir evenly to obtain a multifunctional composite additive.

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