High-density medium imbibition improver for fracturing and preparation method thereof

Abstract

The present application relates to the technical field of fracturing aids, and is a high-density medium imbibition improver for fracturing and a preparation method thereof.The high-density medium imbibition improver for fracturing is mainly obtained by compounding oligomers, outer core surfactants and inner core oil, wherein the oligomers are used to improve the submicron pore entry capacity by virtue of the small size of the oligomers; the outer core surfactants are used to give the surface active component sufficient time to occupy the pore wall surface to make the residual oil and the remaining oil be stripped by the surface active component, and then the residual oil and the remaining oil are assisted to be displaced under the capillary force; and the inner core oil is used to reduce the secondary aggregation probability of crude oil, so that the stripped crude oil is kept in the form of being cut to migrate out of the throat, thereby improving the recovery degree of tight oil and remaining oil. Therefore, the high-density medium imbibition improver for fracturing has good ultra-low adsorption capacity, gradual wetting reverse capacity and crude oil disassociation capacity, and has remarkable oil increasing effect by dialysis.

Description

Technical Field

[0001] This invention relates to the field of fracturing additives, specifically a fracturing medium permeation improver and its preparation method. Background Technology

[0002] Infiltrating-modified fracturing technology involves injecting an absorbent into the oil layer during fracturing. Utilizing the chemical properties of the absorbent, it enhances the hydrophilicity of the rock, reducing the "viscosity" of bound oil and allowing it to detach and flow freely within the fracture. Simultaneously, for bound oil in micro- and nano-pore throats, the nano-absorbent is brought into full contact with the pores, utilizing capillary forces to displace the oil droplets, thereby improving oil recovery. To effectively utilize crude oil in the micro- and nano-pore throats of tight gas reservoirs, there is an urgent need to develop a high-density, multi-medium absorbent modifier for fracturing. Therefore, the research direction of infiltrating modifiers has been clarified. This involves developing nano-adjuvants that penetrate deep into the micro- and nano-pore throats, occupying the pore walls to cause crude oil to detach. Finally, the remaining crude oil or residual oil is displaced through wetting reversal dynamics and displacement driving forces.

[0003] Currently, commonly used permeation modifiers have strong adsorption capacity, and they are fully adsorbed before reaching the fracture tip. By the time they reach the fracture tip, the effective surface active ingredients are almost gone, preventing the surface active ingredients from functioning and thus preventing the timely extraction of tight oil and residual oil from the surface. Wetting reversal agents undergo a short-term hydrophilic-lipophilic conversion, preventing the active ingredients from occupying the pore walls and causing the crude oil to detach and migrate. Desorption crude oil undergoes secondary aggregation, increasing the risk of crude oil blockage and reducing the migration capacity of crude oil.

[0004] To address the above issues, there is an urgent need to develop multi-media nano-permeation modifiers with ultra-low adsorption capacity, gradual wetting reversal capability, and crude oil deassociation capability. Summary of the Invention

[0005] This invention provides a high-density medium permeation modifier for fracturing and its preparation method, which overcomes the shortcomings of the prior art and can effectively solve the problems of poor adsorption capacity, gradual wetting reversal ability and crude oil deassociation ability of existing permeation modifiers.

[0006] One of the technical solutions of the present invention is achieved by the following measures: a high-density medium permeation modifier for fracturing, wherein the raw materials comprise, by weight percentage, 30% to 45% of outer core surfactant, 10% to 15% of mutual solvent, 2% to 5% of oligomer, 2% to 6% of core oil, 1% to 3% of inorganic salt and the balance being water.

[0007] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The aforementioned outer core surfactant is composed of a nonionic surfactant, a gemini surfactant, and a cetyltrimethylammonium bromide in a mass ratio of (10 to 20): (4 to 6): 1.

[0008] The above-mentioned gemini surfactant was obtained by the following method: S1, Dissolve 0.03 mol to 0.05 mol of stearamidopropyl dimethyl tertiary amine in 10 mL to 30 mL of anhydrous ethanol to obtain mixture a; S2, Dissolve 0.05 mol to 0.07 mol of dichloroglycerol in 40 mL to 60 mL of anhydrous ethanol to obtain mixture b; S3, add mixture b to mixture a and stir and reflux to obtain Gemini surfactant, wherein the temperature during reflux is 80℃ to 82℃ and the reflux time is 7h to 9h.

[0009] The aforementioned nonionic surfactant is an alkylphenol polyoxyethylene ether.

[0010] The aforementioned mutual solvents are one or more of ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, and propylene glycol monobutyl ether.

[0011] The aforementioned oligomers are water-soluble polymers, and the water-soluble polymer is polyacrylamide.

[0012] The aforementioned core oil is composed of 5-bromovanillin, chloroform, and petroleum ether in a mass ratio of (9 to 11):3:2.

[0013] The aforementioned inorganic salts are one or more of sodium chloride, potassium chloride, and ammonium chloride.

[0014] The above-mentioned high-density medium permeation modifier for fracturing is obtained by the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 200 rpm to 500 rpm and the stirring time is 240 min to 360 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 200 rpm to 500 rpm, and the stirring time is 60 min to 120 min.

[0015] The second technical solution of the present invention is achieved through the following measures: a method for preparing a high-density medium permeation modifier for fracturing, which is carried out according to the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 200 rpm to 500 rpm and the stirring time is 240 min to 360 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 200 rpm to 500 rpm, and the stirring time is 60 min to 120 min.

[0016] The high-density media permeation modifier for fracturing of this invention is mainly obtained by compounding oligomers, an outer core surfactant, and a core oil fraction. The small size of the oligomers enhances the ability to enter submicron-level pores. The outer core surfactant provides sufficient time for the surface-active components to occupy the pore walls, allowing residual oil to be stripped away. This residual oil is then expelled under capillary action. The core oil fraction reduces the probability of secondary crude oil aggregation, ensuring the stripped crude oil is transported out of the throat in a "cut" form, thereby improving the recovery rate of tight oil and residual oil. Therefore, the high-density media permeation modifier for fracturing of this invention has good ultra-low adsorption capacity, gradual wetting reversal ability, and crude oil deassociation ability, resulting in a significant permeation and oil recovery effect. Detailed Implementation

[0017] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0018] The present invention will be further described below with reference to embodiments: Example 1: The high-density medium permeation modifier for fracturing comprises, by weight percentage, 30% to 45% outer core surfactant, 10% to 15% mutual solvent, 2% to 5% oligomer, 2% to 6% core oil, 1% to 3% inorganic salt and the balance water.

[0019] Example 2: As an optimization of the above example, the outer core surfactant is a mixture of a nonionic surfactant, a gemini surfactant and hexadecyltrimethylammonium bromide in a mass ratio of (10 to 20): (4 to 6): 1.

[0020] Example 3: As an optimization of the above examples, the Gemini surfactant was obtained by the following method: S1, Dissolve 0.03 mol to 0.05 mol of stearamidopropyl dimethyl tertiary amine in 10 mL to 30 mL of anhydrous ethanol to obtain mixture a; S2, Dissolve 0.05 mol to 0.07 mol of dichloroglycerol in 40 mL to 60 mL of anhydrous ethanol to obtain mixture b; S3, add mixture b to mixture a and stir and reflux to obtain Gemini surfactant, wherein the temperature during reflux is 80℃ to 82℃ and the reflux time is 7h to 9h.

[0021] In this invention, the synthetic equation for the gemini surfactant is as follows: Example 4: As an optimization of the above examples, the nonionic surfactant is alkylphenol polyoxyethylene ether.

[0022] Example 5: As an optimization of the above examples, the mutual solvent is one or more of ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, and propylene glycol monobutyl ether.

[0023] Example 6: As an optimization of the above examples, the oligomer is a water-soluble polymer, and the water-soluble polymer is polyacrylamide.

[0024] Example 7: As an optimization of the above example, the kernel oil is composed of 5-bromovanillin, chloroform and petroleum ether in a mass ratio of (9 to 11):3:2.

[0025] Example 8: As an optimization of the above examples, the inorganic salt is one or more of sodium chloride, potassium chloride and ammonium chloride.

[0026] Example 9: As an optimization of the above examples, a high-density medium permeation modifier for fracturing was obtained by the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 200 rpm to 500 rpm and the stirring time is 240 min to 360 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 200 rpm to 500 rpm, and the stirring time is 60 min to 120 min.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: First, in this invention, the outer core surfactant is composed of a nonionic surfactant, a gemini surfactant, and hexadecyltrimethylammonium bromide (CTAB) in a mass ratio of (10 to 20):(4 to 6):1. This ratio results in a uniform rearrangement of the outer core surfactant. The nonionic surfactant is uncharged and therefore has minimal interaction with the sandstone surface. The gemini surfactant has excellent emulsifying ability, and its inherent charge interacts with both CTAB and the nonionic surfactant, resulting in good gradual wetting and oil solubilization capabilities. This allows the outer core surfactant to achieve low adsorption, facilitating long-distance transport and reducing the contact probability between CTAB and the pore walls. This achieves gradual wetting reversal on the reservoir surface, with the wetting angle between the working fluid and sandstone varying from 20° to 160° within 7 days. Therefore, the fracturing high-density medium permeation modifier obtained by adding the outer core surfactant exhibits good gradual wetting reversal capability, low adsorption long-distance transport capability, and emulsifying ability. Secondly, in this invention, a water-soluble polymer, polyacrylamide, is added as a raw material oligomer. Its advantage lies in the fact that the added oligomer enables the fracturing high-density medium permeation modifier to spontaneously expand and form irregular coils, dispersing droplets and resulting in smaller droplet size and increased specific surface area. This stabilizes the emulsion particles and prevents the fracturing high-density medium permeation modifier from rupturing or agglomerating at low concentrations. Therefore, the fracturing high-density medium permeation modifier obtained by adding the oligomer exhibits better emulsion self-healing and emulsion stabilization capabilities, achieving a 500s emulsion stability. -1 No delamination was observed after shearing for 24 hours under the specified conditions; Third, in this invention, the core oil fraction is used as an oil-soluble crude oil deassociation agent. Among them, 5-bromovanillin has strong oil solubility but poor water solubility, which greatly changes its non-polar state and has a strong destructive effect on the aggregation of crude oil structure. Therefore, compared with existing oil solvents, the core oil fraction selected in this invention, which is a compound of 5-bromovanillin, chloroform and petroleum ether, makes the high-density medium permeation modifier for fracturing in this invention have a strong crude oil deassociation ability.

[0028] Example 10: The outer core surfactant is composed of a nonionic surfactant (alkylphenol polyoxyethylene ether), a gemini surfactant, and hexadecyltrimethylammonium bromide in a mass ratio of 20:6:1, wherein the gemini surfactant is obtained by the following method: S1, Dissolve 0.05 mol of stearamide propyl dimethyl tertiary amine in 20 mL of anhydrous ethanol to obtain mixture a; S2, Dissolve 0.07 mol of dichloroglycerol in 50 mL of anhydrous ethanol to obtain mixture b; S3, add mixture b to mixture a and stir and reflux to obtain Gemini surfactant, wherein the temperature during reflux is 80℃ and the reflux time is 8h.

[0029] This fracturing high-density medium permeation modifier comprises, by weight percentage, 45% outer core surfactant, 15% mutual solvent (ethylene glycol monobutyl ether), 5% oligomer (polyacrylamide), 6% core oil (a mixture of 5-bromovanillin, chloroform, and petroleum ether in a mass ratio of 10:3:2), 3% inorganic salt (sodium chloride), and the balance water, obtained by the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 300 rpm and the stirring time is 300 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 300 rpm and the stirring time is 90 min.

[0030] Example 11: The outer core surfactant is composed of a nonionic surfactant (alkylphenol polyoxyethylene ether), a gemini surfactant, and hexadecyltrimethylammonium bromide in a mass ratio of 15:5:1, wherein the gemini surfactant is obtained by the following method: S1, Dissolve 0.04 mol of stearamide propyl dimethyl tertiary amine in 20 mL of anhydrous ethanol to obtain mixture a; S2, Dissolve 0.06 mol of dichloroglycerol in 50 mL of anhydrous ethanol to obtain mixture b; S3, add mixture b to mixture a and stir and reflux to obtain Gemini surfactant, wherein the temperature during reflux is 80℃ and the reflux time is 8h.

[0031] This fracturing high-density medium permeation modifier comprises, by weight percentage, 40% outer core surfactant, 12% mutual solvent (ethylene glycol dibutyl ether), 3% oligomer (polyacrylamide), 4% core oil (a mixture of 5-bromovanillin, chloroform, and petroleum ether in a mass ratio of 10:3:2), 2% inorganic salt (potassium chloride), and the balance water, obtained by the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 300 rpm and the stirring time is 300 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 300 rpm and the stirring time is 90 min.

[0032] Example 12: The outer core surfactant is composed of a nonionic surfactant (alkylphenol polyoxyethylene ether), a gemini surfactant, and hexadecyltrimethylammonium bromide in a mass ratio of 10:4:1, wherein the gemini surfactant is obtained by the following method: S1, Dissolve 0.03 mol of stearamide propyl dimethyl tertiary amine in 20 mL of anhydrous ethanol to obtain mixture a; S2, Dissolve 0.05 mol of dichloroglycerol in 50 mL of anhydrous ethanol to obtain mixture b; S3, add mixture b to mixture a and stir and reflux to obtain Gemini surfactant, wherein the temperature during reflux is 80℃ and the reflux time is 8h.

[0033] This fracturing high-density medium permeation modifier comprises, by weight percentage, 30% outer core surfactant, 10% mutual solvent (propylene glycol monobutyl ether), 2% oligomer (polyacrylamide), 2% core oil (a mixture of 5-bromovanillin, chloroform, and petroleum ether in a mass ratio of 10:3:2), 1% inorganic salt (ammonium chloride), and the balance water, obtained by the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 300 rpm and the stirring time is 300 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 300 rpm and the stirring time is 90 min.

[0034] Comparative Example 1: The difference between this high-density medium permeation improver for fracturing and Example 10 of the present invention is that the outer core surfactant is replaced with the conventional surfactant hexadecyltrimethylammonium bromide (CTAB), while the other steps are the same.

[0035] Comparative Example 2: The difference between this high-density medium permeation modifier for fracturing and Example 10 of the present invention is that no oligomers are added to the raw materials, while the other steps are the same.

[0036] Comparative Example 3: The difference between this high-density medium permeation improver for fracturing and Example 10 of the present invention is that the core oil of the feedstock uses a conventional crude oil deassociation agent (No. 15 white oil), while the other steps are the same.

[0037] Experimental Example 1: The comprehensive performance of the high-density medium permeation modifier for fracturing according to the present invention was investigated.

[0038] Experimental Methods: The comprehensive performance of the high-density medium permeation modifiers for fracturing prepared in Examples 10 to 12 of this invention was investigated. The investigated properties included average particle size, wetting angle, surface tension, interfacial tension, and temperature and shear viscosity. The wetting angle was measured using a contact angle meter. The fracturing fluid formulation was: 0.4% guar gum fracturing fluid + 0.3% high-density medium permeation modifier for fracturing. The fracturing fluid formulation for temperature and shear viscosity was: 0.4% guar gum fracturing fluid + 0.3% high-density medium permeation modifier for fracturing + 0.3% organoboron crosslinking agent. Comparative Examples 1 to 3 were used as controls.

[0039] Experimental Results: The experimental results are shown in Table 1. Compared with Comparative Examples 1 to 3, the high-density medium permeation modifiers for fracturing prepared in Examples 10 to 12 of this invention have a smaller average particle size, ranging from 20 nm to 60 nm. Compared with Comparative Example 1, the wetting angle between the fracturing fluids of Examples 10 to 12 of this invention and sandstone gradually changes from 20° to 160° after 7 days, indicating a strong ability to reverse the wetting angle. Compared with Comparative Example 1, the surface tension and interfacial tension of the fracturing fluids of Examples 10 to 12 of this invention are both lower, with a surface tension of 20 mN / m and an interfacial tension of 0.1 mN / m, indicating that the high-density medium permeation modifier for fracturing also improves the surface and interfacial tension of the fracturing fluid base fluid. Compared with Comparative Examples 1 to 3, the interaction distance between the fracturing fluids of Examples 10 to 12 of this invention and the 0.1 md core is larger, indicating that the high-density medium permeation modifier for fracturing has better wetting and displacement functions and the ability to displace deep layers with low adsorption.

[0040] Experimental Example 2: Application of the high-density medium permeation modifier for fracturing according to the present invention.

[0041] The Xinjiang Mahu Oilfield has low permeability. Well No. 1 in the Xinjiang Mahu Oilfield was used as a field permeation test. 0.3% of the high-density medium permeation improver prepared in Example 10 of this invention was added to the pre-fracturing fluid during the fracturing process of Well No. 1. The average sand ratio was 23.52%, with a maximum sand ratio of 35%. After fracturing, the well was shut in, and the fracturing fluid self-permeated. The permeation process was considered complete when the wellhead pressure stabilized and no longer changed, i.e., the well shut-in was finished. Subsequently, the well was opened for flowback and trial production. The 90-day oil production efficiency was four times that of the adjacent well, demonstrating a significant permeation-induced oil production effect, with a 100% success rate.

[0042] In summary, the high-density media permeation modifier for fracturing of this invention is mainly obtained by compounding oligomers, an outer core surfactant, and a core oil fraction. Specifically, the small size of the oligomers enhances the ability to enter submicron-level pores; the outer core surfactant provides sufficient time for the surface-active components to occupy the pore walls, allowing residual oil to be stripped away, and then assisted in displacement under capillary action; the core oil fraction reduces the probability of secondary aggregation of crude oil, maintaining the stripped crude oil in a "cut" form as it is transported out of the throat, thereby improving the recovery rate of tight oil and residual oil. Therefore, the high-density media permeation modifier for fracturing of this invention has good ultra-low adsorption capacity, gradual wetting reversal ability, and crude oil deassociation ability, resulting in a significant permeation and oil enhancement effect.

[0043] 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.

Claims

1. A high-density medium permeation modifier for fracturing, characterized in that... The raw materials, by weight percentage, comprise 30% to 45% outer core surfactant, 10% to 15% miscible solvent, 2% to 5% oligomer, 2% to 6% core oil, 1% to 3% inorganic salt, and the balance being water.

2. The high-density medium permeation modifier for fracturing according to claim 1, characterized in that... The outer core surfactant is a mixture of a nonionic surfactant, a gemini surfactant, and a cetyltrimethylammonium bromide in a mass ratio of 10 to 20:4 to 6:

1.

3. The high-density medium permeation modifier for fracturing according to claim 2, characterized in that... Gemini surfactants are obtained by the following method: S1, Dissolve 0.03 mol to 0.05 mol of stearamidopropyl dimethyl tertiary amine in 10 mL to 30 mL of anhydrous ethanol to obtain mixture a; S2, Dissolve 0.05 mol to 0.07 mol of dichloroglycerol in 40 mL to 60 mL of anhydrous ethanol to obtain mixture b; S3, add mixture b to mixture a and stir and reflux to obtain Gemini surfactant, wherein the temperature during reflux is 80℃ to 82℃ and the reflux time is 7h to 9h.

4. The high-density medium permeation modifier for fracturing according to claim 2 or 3, characterized in that... The nonionic surfactant is alkylphenol polyoxyethylene ether.

5. The high-density medium permeation modifier for fracturing according to claim 1, 2, 3, or 4, characterized in that... The mutual solvents are one or more of ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, and propylene glycol monobutyl ether.

6. The fracturing medium permeation modifier according to any one of claims 1 to 5, characterized in that... The oligomer is a water-soluble polymer, and the water-soluble polymer is polyacrylamide.

7. The fracturing medium permeation modifier according to any one of claims 1 to 6, characterized in that... The core oil is composed of a mixture of 5-bromovanillin, chloroform, and petroleum ether in a mass ratio of 9 to 11:3:

2.

8. The high-density medium permeation modifier for fracturing according to any one of claims 1 to 7, characterized in that... The inorganic salt is one or more of sodium chloride, potassium chloride, and ammonium chloride.

9. The fracturing medium permeation modifier according to any one of claims 1 to 8, characterized in that... Obtained using the following method: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 200 rpm to 500 rpm and the stirring time is 240 min to 360 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 200 rpm to 500 rpm, and the stirring time is 60 min to 120 min.

10. A method for preparing a high-density medium permeation modifier for fracturing according to any one of claims 1 to 8, characterized in that... Perform the following steps: The first step is to add the required amount of inorganic salt, outer core surfactant, mutual solvent, and core oil to the remaining water in sequence, stir and mix evenly to obtain a mixture. The stirring speed is 200 rpm to 500 rpm and the stirring time is 240 min to 360 min. The second step involves adding the required amount of oligomer to the mixture and stirring until it is homogeneous, thereby obtaining a high-density medium permeation modifier for fracturing. The stirring speed is 200 rpm to 500 rpm, and the stirring time is 60 min to 120 min.

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