A bio-based anti-swelling agent for oil fields and a preparation method thereof

Abstract

The application belongs to the technical field of anti-swelling agents, and specifically provides a bio-based anti-swelling agent for oil fields and a preparation method thereof.The bio-based anti-swelling agent for oil fields comprises an organic phase, an inorganic phase and an additive according to weight parts.The additive comprises potassium dihydrogen phosphate and polyethylene glycol.The organic phase comprises cationic quaternary ammonium salt and carrageenan biological material.The inorganic phase comprises potassium chloride and ammonium chloride.The cationic quaternary ammonium salt is prepared by nucleophilic substitution reaction of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and p-phenylenediamine.The preparation method of the carrageenan biological material comprises the following steps: 1) dissolving kappa-carrageenan in distilled water, adding hydrogen peroxide, adjusting the pH of the system to alkaline, and obtaining a carrageenan base solution by heat preservation reaction; 2) adding lipoic acid and sodium bicarbonate to the carrageenan base solution, embedding by heating and stirring, precipitating with ethanol, and drying after filtration to obtain the product.The anti-swelling agent prepared by the application has the advantages of good durability, high anti-swelling rate and good water resistance.

Description

Technical Field

[0001] This application belongs to the field of anti-swelling agent technology, and in particular relates to a bio-based anti-swelling agent for oil fields and its preparation method. Background Technology

[0002] During the water injection development process in oilfields, clay minerals in reservoir rocks undergo hydration expansion, dispersion, and particle migration upon encountering injected water. This leads to the narrowing and blockage of reservoir pore throats, a significant decrease in permeability, an increase in water injection pressure, and a reduction in crude oil recovery. This phenomenon is known as reservoir water-sensitive damage, which severely restricts oilfield development.

[0003] Adding clay anti-swelling agents to the injected water is currently the most economical and commonly used technique to inhibit clay hydration and swelling. Based on their chemical composition and structure, existing anti-swelling agents are mainly divided into three categories: inorganic, organic cationic, and bio-based. Each type of product has different technical advantages and application limitations. Inorganic anti-swelling agents, represented by inorganic salts such as potassium chloride, ammonium chloride, and calcium chloride, work by utilizing the matching ionic radius of potassium and ammonium ions with the pore size of the six-membered silicon-oxygen rings in clay crystal layers. They exchange ions with exchangeable sodium and calcium ions between the crystal layers, neutralizing the negative charge on the clay surface and compressing the double layer thickness, thereby inhibiting crystal layer hydration and expansion. These products are made from readily available and inexpensive raw materials and have a fast initial anti-swelling response. However, they suffer from inherent drawbacks such as low anti-swelling efficiency and short effective period, with the anti-swelling effect gradually diminishing over time. Furthermore, high concentrations can easily form scale deposits with anions in formation fluids, causing secondary reservoir damage.

[0004] Organic cationic anti-swelling agents, represented by small-molecule quaternary ammonium salts, polyquaternary ammonium salts, and cationic surfactants, are currently the most widely used type of anti-swelling agent in oilfields. These agents have strongly positively charged groups, allowing them to firmly adsorb onto negatively charged clay surfaces through electrostatic attraction. Simultaneously, the long molecular chains coat clay particles and bridge multiple clay crystal layers, forming a dense and stable adsorption film. This results in high anti-swelling efficiency and significantly longer-lasting effects compared to inorganic anti-swelling agents. However, these products are mostly petroleum-based synthetics with poor biodegradability. Long-term, large-scale use can lead to accumulation in water bodies and soil, causing environmental pollution, which contradicts the current industry trend of green oilfields and environmentally friendly development. Furthermore, some high-molecular-weight polyquaternary ammonium salts are prone to irreversible over-adsorption on reservoir pore surfaces, leading to decreased permeability and exacerbating reservoir damage.

[0005] Bio-based anti-swelling agents: Prepared from natural biomass through physical or chemical modification, these agents possess significant advantages such as wide availability, biodegradability, and environmental friendliness, making them a research hotspot in the field of oilfield additives in recent years. However, existing technologies for directly using natural biomaterials as anti-swelling agents have obvious drawbacks: First, bio-based materials have high molecular weights and severe molecular chain entanglement, resulting in poor water solubility and difficulty in uniform adsorption on clay surfaces; second, their molecular functional groups lack sufficient activity, leading to weak bonding with clay surfaces and low anti-swelling efficiency; and third, they exhibit poor temperature and salt resistance, easily undergoing salt precipitation and molecular chain coiling and deactivation in high-salinity formation water, making them unsuitable for applications in medium- and high-temperature, high-salinity reservoirs.

[0006] In summary, existing anti-swelling agents cannot simultaneously achieve a combination of high efficiency in preventing swelling, long-term stability, temperature and salt resistance, and environmental friendliness. Developing high-performance bio-based anti-swelling agents is of great practical significance and application value for promoting oilfield development and improving reservoir protection. Summary of the Invention

[0007] To address the above-mentioned problems, this application provides a bio-based anti-swelling agent for oil fields and its preparation method.

[0008] This application first provides a bio-based anti-swelling agent for oilfields, comprising, by weight, 90-120 parts of organic phase, 25-35 parts of inorganic phase, and 1.5-3 parts of additives; the additives include potassium dihydrogen phosphate and polyethylene glycol; The organic phase comprises cationic quaternary ammonium salt and carrageenan biomass; The inorganic phase includes potassium chloride and ammonium chloride; The cationic quaternary ammonium salt was prepared by a nucleophilic substitution reaction of 3-chloro-2-hydroxypropyltrimethylammonium chloride and p-phenylenediamine. The preparation method of the carrageenan biomaterial includes the following steps: 1) Dissolve κ-carrageenan in distilled water, add hydrogen peroxide, adjust the pH of the system to alkaline, and keep the reaction at a warm temperature to obtain a carrageenan-based solution; 2) Add thioctic acid and sodium bicarbonate to the carrageenan base solution, heat to 55-65℃ and stir to embed, precipitate with ethanol, filter and dry to obtain the final product.

[0009] Preferably, the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to p-phenylenediamine is (4-6):1. The main chain of this cationic quaternary ammonium salt contains a rigid benzene ring structure, and the side chains have multiple positively charged quaternary ammonium groups, resulting in a high positive charge density and strong electrostatic adsorption force with the clay surface. At the same time, the benzene ring structure can provide hydrophobic association sites, improving the stability of the adsorption membrane.

[0010] Furthermore, in step 1), the concentration of hydrogen peroxide in the system is 10-20%.

[0011] Furthermore, in step 1), the heat preservation reaction is carried out at 80-95℃ for 1.5-3 hours.

[0012] Furthermore, in step 2), the ratio of carrageenan base solution, thioctic acid, and sodium bicarbonate is 1L:(10-30g):(30-60g).

[0013] Furthermore, the mass ratio of the cationic quaternary ammonium salt to the carrageenan biomass is 1:(0.3-0.5).

[0014] Furthermore, the mass ratio of potassium chloride to ammonium chloride is 1:(0.15-0.25).

[0015] Furthermore, the inorganic phase is a complex system of potassium chloride and ammonium chloride, K + With NH4 + Synergistic effect of ion exchange to prevent swelling, K + The ionic radius and clay crystal pore size have a high degree of matching, resulting in strong adsorption and good long-term effectiveness; NH4 + With a small hydration radius and fast diffusion rate, the initial anti-swelling response is rapid, and the combination of the two takes into account both speed and stability.

[0016] Furthermore, in the additives, potassium dihydrogen phosphate acts as a pH buffer to ensure the stability of the positive charge of the quaternary ammonium salt, while also moderately suppressing the negative charge on the clay surface, thus helping to improve the anti-swelling effect; polyethylene glycol is preferably polyethylene glycol 400, which acts as a dispersant and wetting agent, reducing the surface tension of the system, improving the wetting and dispersibility of the anti-swelling agent on the surface of rock pores, promoting the uniform adsorption of anti-swelling agent molecules, and improving the flow properties of the injected fluid, thereby reducing the risk of reservoir blockage.

[0017] This application also provides a method for preparing a bio-based anti-swelling agent for oilfield use, comprising the following steps: S1: Preparation of cationic quaternary ammonium salts; S2: Modified carrageenan biomass; S3: The organic phase is obtained by mixing cationic quaternary ammonium salt with carrageenan biomass, and then the inorganic phase and additives are mixed evenly to obtain the bio-based anti-swelling agent for oil fields.

[0018] Compared with the prior art, this application has the following beneficial effects: The cationic quaternary ammonium salt of this application generates strong electrostatic adsorption with the clay surface through high-density positive charge, and undergoes ion exchange with low-valence cations between crystal layers. At the same time, the coating and bridging effect of the molecular chain binds the clay particles into a stable whole, thereby effectively inhibiting clay hydration and dispersion. The quaternary ammonium structure is less affected by pH and can function stably in a wide range of acidic and alkaline environments. Meanwhile, the carrageenan biomaterial of this application, on the one hand, forms multiple hydrogen bonds with the silanol and aluminol groups on the clay surface through a large number of hydroxyl and sulfate ester groups on the molecular chain, providing additional adsorption driving force in addition to electrostatic adsorption and improving the bonding strength of the adsorption layer. On the other hand, the hydrophobic thioctic acid segments embedded in the carrageenan system can undergo hydrophobic association with the benzene ring and alkyl structure of the cationic quaternary ammonium salt to form a composite adsorption film on the clay surface, effectively blocking water molecules from diffusing into the clay crystal layers, and significantly reducing the probability of the adsorption layer being washed away by water flow, thus significantly improving the anti-swelling and long-term effects. In addition, the degraded carrageenan oligosaccharide molecules have a moderate length, which can partially adsorb and insert into the interstitial spaces of clay crystal layers. Through the steric hindrance effect, the hydration expansion of the crystal layers is restricted. Furthermore, the carrageenan biomaterial can chelate with calcium ions, enhance ion exchange, and further strengthen the anti-swelling effect. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the core flow test data of the anti-swelling agent in Examples 1-2 and Control Groups 1-3 of this application. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0022] Example 1 The oilfield bio-based anti-swelling agent of this embodiment includes 1 kg of organic phase, 300 g of inorganic phase and 20 g of additives.

[0023] The organic phase includes cationic quaternary ammonium salt and carrageenan biomass, with a mass ratio of cationic quaternary ammonium salt to carrageenan biomass of 1:0.35.

[0024] The cationic quaternary ammonium salt was synthesized from 3-chloro-2-hydroxypropyltrimethylammonium chloride and p-phenylenediamine. The specific method was as follows: 500 mL of anhydrous ethanol and 0.1 mol of p-phenylenediamine were added to a four-necked flask, the temperature was raised to 80 °C, and 0.5 mol of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise while stirring continuously. After the addition was completed, the reaction was continued for 7 h to obtain the final product.

[0025] The preparation method of carrageenan biomass includes the following steps: 1) Dissolve 150g of κ-carrageenan in distilled water at 90℃, quickly add hydrogen peroxide to control the concentration of hydrogen peroxide in the system to 15%, adjust the pH of the system to 8 with NaOH solution, and keep it at 90℃ for 2h to obtain carrageenan base solution; 2) Add 15g of thioctic acid and 30g of sodium bicarbonate to 1L of carrageenan-based solution, stir at 60℃ for 3h, precipitate with ethanol, filter and dry to obtain the final product.

[0026] The inorganic phase includes potassium chloride and ammonium chloride, with a mass ratio of potassium chloride to ammonium chloride of 1:0.2.

[0027] The additive is composed of potassium dihydrogen phosphate and polyethylene glycol 400 in a mass ratio of 1:0.5.

[0028] The preparation method of the oilfield bio-based anti-swelling agent in this embodiment includes the following steps: S1: Preparation of cationic quaternary ammonium salts; S2: Preparation of carrageenan biomass; S3: The organic phase is obtained by mixing cationic quaternary ammonium salt with carrageenan biomass, and then the inorganic phase and additives are mixed evenly in proportion to obtain the bio-based anti-swelling agent for oil fields.

[0029] Example 2 The oilfield bio-based anti-swelling agent of this embodiment includes 1 kg of organic phase, 300 g of inorganic phase and 20 g of additives.

[0030] The organic phase includes cationic quaternary ammonium salt and carrageenan biomass, with a mass ratio of cationic quaternary ammonium salt to carrageenan biomass of 1:0.45.

[0031] The cationic quaternary ammonium salt was synthesized from 3-chloro-2-hydroxypropyltrimethylammonium chloride and p-phenylenediamine. The specific method was as follows: 500 mL of anhydrous ethanol and 0.1 mol of p-phenylenediamine were added to a four-necked flask, the temperature was raised to 80 °C, and 0.5 mol of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise while stirring continuously. After the addition was completed, the reaction was continued for 7 h to obtain the final product.

[0032] The preparation method of carrageenan biomass includes the following steps: 1) Dissolve 150g of κ-carrageenan in distilled water at 90℃, quickly add hydrogen peroxide to control the concentration of hydrogen peroxide in the system to 15%, adjust the pH of the system to 8 with NaOH solution, and keep it at 90℃ for 2h to obtain carrageenan base solution; 2) Add 15g of thioctic acid and 50g of sodium bicarbonate to 1L of carrageenan-based solution, stir at 60℃ for 3h, precipitate with ethanol, filter and dry to obtain the final product.

[0033] The inorganic phase includes potassium chloride and ammonium chloride, with a mass ratio of potassium chloride to ammonium chloride of 1:0.2.

[0034] The additive is composed of potassium dihydrogen phosphate and polyethylene glycol 400 in a mass ratio of 1:0.5.

[0035] The preparation method of the oilfield bio-based anti-swelling agent in this embodiment is the same as that in Example 1.

[0036] Control group 1 The anti-swelling agent in this control group consisted of 1 kg of organic phase, 300 g of inorganic phase, and 20 g of additives.

[0037] The organic phase is a cationic quaternary ammonium salt.

[0038] The cationic quaternary ammonium salt was synthesized from 3-chloro-2-hydroxypropyltrimethylammonium chloride and p-phenylenediamine. The specific method was as follows: 500 mL of anhydrous ethanol and 0.1 mol of p-phenylenediamine were added to a four-necked flask, the temperature was raised to 80 °C, and 0.5 mol of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise while stirring continuously. After the addition was completed, the reaction was continued for 7 h to obtain the final product.

[0039] The inorganic phase includes potassium chloride and ammonium chloride, with a mass ratio of potassium chloride to ammonium chloride of 1:0.2.

[0040] The additive is composed of potassium dihydrogen phosphate and polyethylene glycol 400 in a mass ratio of 1:0.5.

[0041] The preparation method of the oilfield bio-based anti-swelling agent in this control group is the same as that in Example 1.

[0042] Control group 2 The anti-swelling agent in this control group consisted of 1 kg of organic phase, 300 g of inorganic phase, and 20 g of additives.

[0043] The organic phase is carrageenan biomass.

[0044] The preparation method of carrageenan biomass includes the following steps: 1) Dissolve 150g of κ-carrageenan in distilled water at 90℃, quickly add hydrogen peroxide to control the concentration of hydrogen peroxide in the system to 15%, adjust the pH of the system to 8 with NaOH solution, and keep it at 90℃ for 2h to obtain carrageenan base solution; 2) Add 15g of thioctic acid and 50g of sodium bicarbonate to 1L of carrageenan-based solution, stir at 60℃ for 3h, precipitate with ethanol, filter and dry to obtain the final product.

[0045] The inorganic phase includes potassium chloride and ammonium chloride, with a mass ratio of potassium chloride to ammonium chloride of 1:0.2.

[0046] The additive is composed of potassium dihydrogen phosphate and polyethylene glycol 400 in a mass ratio of 1:0.5.

[0047] The preparation method of the oilfield bio-based anti-swelling agent in this control group is the same as that in Example 1.

[0048] Control group 3 The anti-swelling agent in this control group consisted of 1 kg of organic phase, 300 g of inorganic phase, and 20 g of additives.

[0049] The organic phase includes a cationic quaternary ammonium salt and κ-carrageenan, with a mass ratio of cationic quaternary ammonium salt to κ-carrageenan of 1:0.35.

[0050] The cationic quaternary ammonium salt was synthesized from 3-chloro-2-hydroxypropyltrimethylammonium chloride and p-phenylenediamine. The specific method was as follows: 500 mL of anhydrous ethanol and 0.1 mol of p-phenylenediamine were added to a four-necked flask, the temperature was raised to 80 °C, and 0.5 mol of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise while stirring continuously. After the addition was completed, the reaction was continued for 7 h to obtain the final product.

[0051] The inorganic phase includes potassium chloride and ammonium chloride, with a mass ratio of potassium chloride to ammonium chloride of 1:0.2.

[0052] The additive is composed of potassium dihydrogen phosphate and polyethylene glycol 400 in a mass ratio of 1:0.5.

[0053] The preparation method of the oilfield bio-based anti-swelling agent in this control group is the same as that in Example 1.

[0054] Performance testing 1. In accordance with the petroleum and natural gas industry standard SY / T 5971-2016 "Performance Evaluation Method for Clay Stabilizers for Water Injection" and related reservoir protection evaluation standards, the anti-swelling performance and water wash resistance of the anti-swelling agents in Examples 1-2 and Control Groups 1-3 were tested. The results are shown in Table 1. The test conditions are as follows: Room temperature swelling resistance test: Calcium-based bentonite was dried at 105℃ for 4 hours and then cooled for later use; a 1.0% (w / w) anti-swelling agent aqueous solution was prepared, and the swelling resistance was determined by centrifugation. The calculation formula is as follows: Anti-swelling rate (%) = [(V2-V1) / (V2-V0)]×100% In the formula: V0 is the expansion volume of bentonite in kerosene, mL; V1 is the expansion volume of bentonite in anti-swelling agent solution, mL; V2 is the expansion volume of bentonite in distilled water, mL.

[0055] Each sample was tested in parallel three times, and the average value was taken.

[0056] Water wash resistance test: The bentonite saturated with anti-swelling agent was centrifuged, the supernatant was discarded, an equal volume of distilled water was added and stirred evenly, soaked for 2 hours, and then centrifuged again. The washing was repeated 3 times. The anti-swelling rate of the bentonite after washing was measured, and the anti-swelling rate retention rate was calculated. Anti-swelling retention rate (%) = (anti-swelling rate after washing / initial anti-swelling) × 100%.

[0057] Table 1. Test data on the anti-swelling performance of the anti-swelling agents in Examples 1-2 and Control Groups 1-3.

[0058] 2. Core flow experiments were conducted according to SY / T 5358-2024 "Evaluation of Reservoir Sensitivity Flow Tests" to determine the long-term effectiveness of the anti-swelling agents in Examples 1-2 and Control Groups 1-3. The test results are as follows: Figure 1 As shown.

[0059] Analysis Table 1 and Figure 1 It can be seen that the anti-swelling agent of this application has good anti-swelling performance and long-term anti-swelling effect. After 50PV of water injection, the water-sensitive damage rate is low, making it suitable for oilfield fracturing operations in various environments.

[0060] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A bio-based anti-swelling agent for oilfield use, characterized in that, By weight, it comprises 90-120 parts of organic phase, 25-35 parts of inorganic phase, and 1.5-3 parts of additives; the additives include potassium dihydrogen phosphate and polyethylene glycol; The organic phase comprises cationic quaternary ammonium salt and carrageenan biomass; The inorganic phase includes potassium chloride and ammonium chloride; The cationic quaternary ammonium salt is prepared by nucleophilic substitution reaction of 3-chloro-2-hydroxypropyltrimethylammonium chloride and p-phenylenediamine; the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to p-phenylenediamine is (4-6):1; The preparation method of the carrageenan biomaterial includes the following steps: 1) Dissolve κ-carrageenan in distilled water, add hydrogen peroxide, adjust the pH of the system to alkaline, and keep the reaction at a warm temperature to obtain a carrageenan-based solution; 2) Add thioctic acid and sodium bicarbonate to the carrageenan base solution, heat to 55-65℃ and stir to embed, precipitate with ethanol, filter and dry to obtain the final product.

2. The bio-based anti-swelling agent for oilfield use according to claim 1, characterized in that, In step 1), the concentration of hydrogen peroxide in the system is 10-20%.

3. The bio-based anti-swelling agent for oilfield use according to claim 1, characterized in that, In step 1), the heat preservation reaction is carried out at 80-95℃ for 1.5-3 hours.

4. The bio-based anti-swelling agent for oilfield use according to claim 1, characterized in that, In step 2), the ratio of carrageenan base solution, thioctic acid and sodium bicarbonate is 1L:(10-30g):(30-60g).

5. The bio-based anti-swelling agent for oilfield use according to claim 1, characterized in that, The mass ratio of the cationic quaternary ammonium salt to the carrageenan biomass is 1:(0.3-0.5).

6. The bio-based anti-swelling agent for oilfield use according to claim 1, characterized in that, The mass ratio of potassium chloride to ammonium chloride is 1:(0.15-0.25).

7. A method for preparing a bio-based anti-swelling agent for oilfield use as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Preparation of cationic quaternary ammonium salts; S2: Preparation of carrageenan biomass; S3: The organic phase is obtained by mixing cationic quaternary ammonium salt with carrageenan biomass, and then the inorganic phase and additives are mixed evenly to obtain the bio-based anti-swelling agent for oil fields.

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