Degradable cleanup agent for oil field and preparation method thereof

Abstract

This application belongs to the technical field of oilfield drainage aids, specifically providing a biodegradable drainage aid for oilfields and its preparation method. The biodegradable drainage aid for oilfields, by mass percentage, comprises the following components: 15%-25% surfactant; 20%-30% mineral oil; 10%-20% protein emulsion; 1%-5% nanofiller; and the balance being deionized water. The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:(0.1-0.2). The protein emulsion is prepared by ultrasonic emulsification of zein, glycerol, iron-chelated xanthan gum, and glucono-δ-lactone. The drainage aid obtained by this application has the advantages of high drainage rate, good stability, and biodegradability.

Description

Technical Field

[0001] This application belongs to the field of oilfield drainage aid technology, and in particular relates to a biodegradable drainage aid for oilfields and its preparation method. Background Technology

[0002] In oil and gas field development, acidizing, fracturing, and other production enhancement measures are important means to improve reservoir permeability and increase single-well production. These operations typically require injecting large amounts of working fluid into the formation. After the operations are completed, these residual fluids need to be promptly drained from the formation back to the surface to reduce damage to the reservoir and restore oil and gas flow channels. Drainage aids, as key additives in the working fluid system, play a crucial role in reducing the surface tension of the fluid and the oil-water interfacial tension, thereby reducing capillary resistance and significantly improving the drainage efficiency of residual fluids.

[0003] Currently, commonly used drainage aids mainly include fluorocarbon surfactants, nonionic surfactants, and various compound systems. Among them, fluorocarbon surfactants are favored due to their extremely low surface tension, but they suffer from high cost and strong environmental persistence. On the other hand, traditional macromolecular polymer or conventional surfactant drainage aids, while cost-effective, generally suffer from insufficient temperature and salt resistance, and significant adsorption loss under complex geological conditions, leading to a substantial reduction in drainage aid effectiveness. Furthermore, with increasingly stringent environmental protection requirements, the development of efficient, low-cost, and environmentally friendly biodegradable drainage aids has become an inevitable trend in the industry.

[0004] Existing technologies have attempted to incorporate natural polymer materials into drainage aid systems to improve their environmental friendliness, but these efforts often face challenges such as poor compatibility between components, system instability, and limited functionality. For example, while simple protein additions can be biodegradable, their low surface activity and susceptibility to bacterial degradation make them difficult to absorb. The introduction of nanomaterials can improve system stability, but achieving synergistic effects with organic components while maintaining the overall degradability of the system remains a technical challenge. Therefore, there is an urgent need to develop a novel drainage aid that combines high surface activity, excellent drainage efficiency, good formation adaptability, and environmental degradability. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a biodegradable drainage aid for oilfields and its preparation method.

[0006] This application first provides a biodegradable drainage aid for oilfields, which, by mass percentage, consists of the following components: Surfactant 15%-25%; Mineral oil 20%-30%; Protein emulsion 10%-20%; Nanofillers 1%-5%; The remainder is deionized water; The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:(0.1-0.2); The protein emulsion is prepared by ultrasonic emulsification of zein, glycerol, iron-chelated xanthan gum, and glucono-δ-lactone.

[0007] Furthermore, the surfactant includes water-soluble nonionic surfactants, oil-soluble nonionic surfactants, and fluorocarbon surfactants.

[0008] Furthermore, the surfactant is composed of a water-soluble nonionic surfactant, an oil-soluble nonionic surfactant, and a fluorocarbon surfactant in a mass ratio of 1:(0.8-1.2):(3.0-4.0).

[0009] Furthermore, the water-soluble nonionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyethylene glycol fatty acid ester, and sorbitan fatty acid ester polyoxyethylene ether. And / or, the oil-soluble nonionic surfactant is selected from at least one of sorbitan fatty acid esters, polyglycerol fatty acid esters, and fatty alcohol polyoxypropylene ethers; And / or, the fluorocarbon surfactant is selected from at least one of perfluoroalkyl ethanol polyoxyethylene ether, perfluoroalkyl betaine, potassium perfluorobutyl sulfonate, and perfluorohexyl sulfonamide propyl betaine.

[0010] Furthermore, the mineral oil is selected from at least one of white oil, light kerosene, and hydrotreated diesel.

[0011] Furthermore, the method for preparing the protein emulsion includes the following steps: 1) Dissolve zein in an ethanol-water solution, add glycerol and stir to obtain the protein stock solution; 2) Add ferrous chloride to the xanthan gum solution, stir to complex, and dry to obtain iron-complexed xanthan gum; 3) Add the obtained iron-chelated xanthan gum and gluconate-δ-lactone to the protein stock solution, heat to 45-55℃ and disperse by ultrasonication to obtain the final product.

[0012] Furthermore, in step 2), the xanthan gum solution has a mass concentration of 2-4 g / L, and the ferrous chloride added has a final mass concentration of 1.0%-2.0%.

[0013] Furthermore, in step 3), the amount of iron-chelated xanthan gum added is 0.5-1.5g and the amount of glucono-δ-lactone added is 0.025-0.1g per 100mL of protein stock solution.

[0014] This application also provides a method for preparing a biodegradable drainage aid for oil fields, comprising the following steps: mixing surfactant, mineral oil and protein emulsion in the prescribed amounts to obtain an oil phase premix; adding deionized water and nanofiller to the oil phase premix, heating and stirring, and cooling to room temperature to obtain the final product.

[0015] Compared with the prior art, this application has the following beneficial effects: This application utilizes the combined action of a compounded surfactant, protein emulsion, and nanofiller to construct a composite interfacial film at the oil-water interface, significantly reducing interfacial tension and capillary resistance. Simultaneously, the protein emulsion and nanoparticles improve rock surface wettability, further reducing flowback resistance and increasing the flowback rate, which is significantly superior to conventional flowback aids. This makes it suitable for fracturing and acidizing flowback operations in medium-to-low permeability, tight reservoirs. Furthermore, the protein emulsion in this application uses biomass materials such as zein, xanthan gum, and glycerol as components, combined with biodegradable nonionic surfactants. The main components of the system can be gradually decomposed into small molecules by environmental microorganisms, leaving almost no long-term residue in the formation, effectively preventing reservoir damage and groundwater pollution.

[0016] Furthermore, the iron-chelated xanthan gum exhibits enhanced molecular chain rigidity, making it less prone to curling at high temperatures. In high-salt environments, the carboxyl groups are coordinated and shielded by metal ions, reducing the likelihood of salting-out. The gluconic acid generated from the hydrolysis of gluconic acid-δ-lactone can form a weak coordination complex with iron ions, providing a slow-release effect and preventing rapid sedimentation or deactivation of free iron ions. This allows the cross-linked network to maintain long-term stability. Consequently, the resulting three-dimensional cross-linked network can stably increase the viscosity of the continuous phase, inhibit droplet aggregation, and the protein / particle composite film at the interface forms strong steric hindrance, preventing droplet coalescence and significantly improving the system's temperature and salt resistance and stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the surface tension and drainage performance data of the drainage aids in Examples 1-2 and Control Groups 1-3 of this application.

[0018] Figure 2 This is a schematic diagram showing the thermal stability data of the excretion aid in Examples 1-2 and Control Groups 1-3 of this application. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] Example 1 The biodegradable drainage aid for oilfields in this embodiment includes the following raw materials by mass percentage: 20% surfactant, 25% mineral oil, 15% protein emulsion, 2.5% nanofiller, and the balance being deionized water.

[0022] The surfactant is composed of a water-soluble nonionic surfactant, an oil-soluble nonionic surfactant, and a fluorocarbon surfactant in a mass ratio of 1:1:3.5. The water-soluble nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-7. The oil-soluble nonionic surfactant is sorbitan monooleate Span-80. The fluorocarbon surfactant is perfluorohexyl ethanol polyoxyethylene ether. The mineral oil is No. 5 white oil.

[0023] The preparation method of protein emulsion includes the following steps: 1) Weigh 2.5g of zein and slowly add it to 200mL of 80% (v / v) ethanol aqueous solution. Stir at 350rpm for 30min, then add 10g of glycerol and continue stirring for 1h to obtain the protein stock solution. 2) Prepare a 3 g / L xanthan gum solution, then add ferrous chloride, controlling the mass concentration of ferrous chloride added to 1.5%, stir for 20 min, filter and dry to obtain iron-complexed xanthan gum; 3) Disperse 2g of iron-chelated xanthan gum and 0.1g of gluconate-δ-lactone in 500mL of deionized water to prepare a solution, then slowly add it to the protein stock solution, heat to 50℃ and sonicate for 20min, and then remove 1 / 2 of the ethanol from the system by rotary evaporation to obtain the final product.

[0024] The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:0.15.

[0025] The preparation method of the biodegradable drainage aid for oilfields in this embodiment includes the following steps: a surfactant is mixed evenly with mineral oil and protein emulsion to obtain an oil phase premix; then deionized water and nanofiller are added to the oil phase premix, the temperature is raised to 60°C, and the mixture is stirred at 1000 rpm for 3 hours, and then cooled to room temperature to obtain the final product.

[0026] Example 2 The biodegradable drainage aid for oilfields in this embodiment includes the following raw materials by mass percentage: 20% surfactant, 30% mineral oil, 10% protein emulsion, 2.5% nanofiller, and the balance being deionized water.

[0027] The surfactant is composed of a water-soluble nonionic surfactant, an oil-soluble nonionic surfactant, and a fluorocarbon surfactant in a mass ratio of 1:1:3.5. The water-soluble nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-7. The oil-soluble nonionic surfactant is sorbitan monooleate Span-80. The fluorocarbon surfactant is perfluorohexyl ethanol polyoxyethylene ether. The mineral oil is No. 5 white oil.

[0028] The preparation method of protein emulsion includes the following steps: 1) Weigh 2.5g of zein and slowly add it to 200mL of 80% (v / v) ethanol aqueous solution. Stir at 350rpm for 30min, then add 10g of glycerol and continue stirring for 1h to obtain the protein stock solution. 2) Prepare a 3 g / L xanthan gum solution, then add ferrous chloride, controlling the mass concentration of ferrous chloride added to 1.5%, stir for 20 min, filter and dry to obtain iron-complexed xanthan gum; 3) Disperse 2g of iron-chelated xanthan gum and 0.1g of gluconate-δ-lactone in 500mL of deionized water to prepare a solution, then slowly add it to the protein stock solution, heat to 50℃ and sonicate for 20min, and then remove 1 / 2 of the ethanol from the system by rotary evaporation to obtain the final product.

[0029] The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:0.15.

[0030] The preparation method of the biodegradable drainage aid for oilfields in this embodiment includes the following steps: a surfactant is mixed evenly with mineral oil and protein emulsion to obtain an oil phase premix; then deionized water and nanofiller are added to the oil phase premix, the temperature is raised to 60°C, and the mixture is stirred at 1000 rpm for 3 hours, and then cooled to room temperature to obtain the final product.

[0031] Control group 1 The drainage aid in this control group consisted of the following raw materials by mass percentage: 20% surfactant, 40% mineral oil, 2.5% nanofiller, and the remainder being deionized water.

[0032] The surfactant is composed of a water-soluble nonionic surfactant, an oil-soluble nonionic surfactant, and a fluorocarbon surfactant in a mass ratio of 1:1:3.5. The water-soluble nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-7. The oil-soluble nonionic surfactant is sorbitan monooleate Span-80. The fluorocarbon surfactant is perfluorohexyl ethanol polyoxyethylene ether. The mineral oil is No. 5 white oil.

[0033] The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:0.15.

[0034] The preparation method of the drainage aid in this control group includes the following steps: the surfactant and mineral oil are mixed evenly to obtain an oil phase premix; then deionized water and nanofiller are added to the oil phase premix, the temperature is raised to 60℃, stirred at 1000rpm for 3h, and cooled to room temperature to obtain the product.

[0035] Control group 2 The drainage aid in this control group consisted of the following raw materials by mass percentage: 20% surfactant, 25% mineral oil, 15% protein emulsion, 2.5% nanofiller, and the remainder being deionized water.

[0036] The surfactant is composed of a water-soluble nonionic surfactant, an oil-soluble nonionic surfactant, and a fluorocarbon surfactant in a mass ratio of 1:1:3.5. The water-soluble nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-7. The oil-soluble nonionic surfactant is sorbitan monooleate Span-80. The fluorocarbon surfactant is perfluorohexyl ethanol polyoxyethylene ether. The mineral oil is No. 5 white oil.

[0037] The preparation method of protein emulsion includes the following steps: Weigh 2.5g of zein and slowly add it to 200mL of 80% (v / v) ethanol aqueous solution. Stir at 350rpm for 30min, then add 10g of glycerol and continue stirring for 1h. Then add 300mL of deionized water, heat to 50℃ and sonicate for 20min. Finally, remove 1 / 2 of the ethanol from the system by rotary evaporation to obtain the emulsion.

[0038] The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:0.15.

[0039] The preparation method of the drainage aid in this control group includes the following steps: the surfactant is mixed evenly with mineral oil and protein emulsion to obtain an oil phase premix; then deionized water and nanofiller are added to the oil phase premix, the temperature is raised to 60℃, stirred at 1000rpm for 3h, and cooled to room temperature to obtain the product.

[0040] Control group 3 The drainage aid in this control group consisted of the following raw materials by mass percentage: 20% surfactant, 25% mineral oil, 15% protein emulsion, 2.5% nanofiller, and the remainder being deionized water.

[0041] The surfactant is composed of a water-soluble nonionic surfactant, an oil-soluble nonionic surfactant, and a fluorocarbon surfactant in a mass ratio of 1:1:3.5. The water-soluble nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-7. The oil-soluble nonionic surfactant is sorbitan monooleate Span-80. The fluorocarbon surfactant is perfluorohexyl ethanol polyoxyethylene ether. The mineral oil is No. 5 white oil.

[0042] The preparation method of protein emulsion includes the following steps: 1) Weigh 2.5g of zein and slowly add it to 200mL of 80% (v / v) ethanol aqueous solution. Stir at 350rpm for 30min, then add 10g of glycerol and continue stirring for 1h to obtain the protein stock solution. 2) Prepare a 3 g / L xanthan gum solution, then add ferrous chloride, controlling the mass concentration of ferrous chloride added to 1.5%, stir for 20 min, filter and dry to obtain iron-complexed xanthan gum; 3) Disperse 2g of iron-chelated xanthan gum in 500mL of deionized water to prepare a solution, then slowly add it to the protein stock solution, heat to 50℃ and sonicate for 20min, and then remove 1 / 2 of the ethanol from the system by rotary evaporation to obtain the final product.

[0043] The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:0.15.

[0044] The preparation method of the drainage aid in this control group includes the following steps: the surfactant is mixed evenly with mineral oil and protein emulsion to obtain an oil phase premix; then deionized water and nanofiller are added to the oil phase premix, the temperature is raised to 60℃, stirred at 1000rpm for 3h, and cooled to room temperature to obtain the product.

[0045] Performance testing 1. Take the drainage aids from Examples 1-2 and Control Groups 1-3, and measure their surface tension according to the requirements of the standard "Method for Determination of Surface and Interfacial Tension" (SY / T 5370—2018); measure their drainage performance according to the requirements of the standard "Performance Evaluation Method for Drainage Aids for Fracturing and Acidizing" (SY / T 5755—2016). The test results are as follows: Figure 1 As shown.

[0046] 2. Take the drainage aids from Examples 1-2 and Control Groups 1-3, and measure the surface tension changes of each sample after aging at 90℃ for different times. Figure 2 As shown.

[0047] analyze Figure 1 and Figure 2 As can be seen, the drainage aid of this application has low surface tension and can exert a good drainage aid effect. Furthermore, it maintains good drainage aid performance even after thermal aging, exhibiting excellent thermal stability, making it suitable for use in medium-low permeability and high-temperature tight reservoirs.

[0048] 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 biodegradable drainage aid for oilfield use, characterized in that, By mass percentage, it consists of the following components composition: Surfactant 15%-25%; Mineral oil 20%-30%; Protein emulsion 10%-20%; Nanofillers 1%-5%; The remainder is deionized water; The nanofiller is composed of nano-silica and nano-calcium carbonate in a mass ratio of 1:(0.1-0.2); The protein emulsion is prepared by ultrasonic emulsification of zein, glycerol, iron-chelated xanthan gum, and glucono-δ-lactone.

2. The biodegradable drainage aid for oilfields according to claim 1, characterized in that, The surfactants include water-soluble nonionic surfactants, oil-soluble nonionic surfactants, and fluorocarbon surfactants.

3. The biodegradable drainage aid for oilfields according to claim 2, characterized in that, The surfactant is composed of water-soluble nonionic surfactant, oil-soluble nonionic surfactant and fluorocarbon surfactant in a mass ratio of 1:(0.8-1.2):(3.0-4.0).

4. The biodegradable drainage aid for oilfields according to claim 3, characterized in that, The water-soluble nonionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyethylene glycol fatty acid ester, and sorbitan fatty acid ester polyoxyethylene ether. And / or, the oil-soluble nonionic surfactant is selected from at least one of sorbitan fatty acid esters, polyglycerol fatty acid esters, and fatty alcohol polyoxypropylene ethers; And / or, the fluorocarbon surfactant is selected from at least one of perfluoroalkyl ethanol polyoxyethylene ether, perfluoroalkyl betaine, potassium perfluorobutyl sulfonate, and perfluorohexyl sulfonamide propyl betaine.

5. The biodegradable drainage aid for oilfields according to claim 1, characterized in that, The mineral oil is selected from at least one of white oil, light kerosene, and hydrotreated diesel.

6. The biodegradable drainage aid for oilfields according to claim 1, characterized in that, The method for preparing the protein emulsion includes the following steps: 1) Dissolve zein in an ethanol-water solution, add glycerol and stir to obtain the protein stock solution; 2) Add ferrous chloride to the xanthan gum solution, stir to complex, and dry to obtain iron-complexed xanthan gum; 3) Add the obtained iron-chelated xanthan gum and gluconate-δ-lactone to the protein stock solution, heat to 45-55℃ and disperse by ultrasonication to obtain the final product.

7. The biodegradable drainage aid for oilfields according to claim 6, characterized in that, In step 2), the xanthan gum solution has a mass concentration of 2-4 g / L, and the ferrous chloride added has a final mass concentration of 1.0%-2.0%.

8. The biodegradable drainage aid for oilfields according to claim 6, characterized in that, In step 3), the amount of iron-chelated xanthan gum added is 0.5-1.5g and the amount of glucono-δ-lactone added is 0.025-0.1g per 100mL of protein stock solution.

9. A method for preparing a biodegradable drainage aid for oilfields as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing the formulated amounts of surfactant, mineral oil, and protein emulsion evenly to obtain an oil phase premix; adding deionized water and nanofiller to the oil phase premix, heating and stirring, and cooling to room temperature to obtain the final product.

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