Well flushing fluid for improving flow conductivity of sandstone geothermal well and preparation method and application of well flushing fluid

Abstract

The invention relates to the field of development and utilization of geothermal resources, and discloses a flushing fluid for improving the flow conductivity of a sandstone geothermal well as well as a preparation method and application of the flushing fluid for improving the flow conductivity of the sandstone geothermal well, and the flushing fluid for improving the flow conductivity of the sandstone geothermal well comprises the following components in percentage by weight: 10-30% of glucose; 2%-5% of nano silicon dioxide; 1%-4% of lignin; 0.1%-2% of a quaternary ammonium salt surfactant; 1%-4% of cellulose acetate; 1%-2% of potassium chloride; 0.2% to 0.4% of acrylamide dimethyl diethylene propyl ammonium chloride; 0.1%-0.2% of a chelating agent; and the balance of water. The flushing fluid provided by the invention is mainly applied to geothermal wells, the problem of residual chemical agents is solved, and all the materials selected by the system can be naturally decomposed. And the system mainly aims at only a water phase, and does not relate to an oil phase and a gas phase. As the working medium is single, materials can be optimized, and the system cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of geothermal resource development and utilization, specifically to a well-washing fluid for improving the conductivity of sandstone geothermal wells, its preparation method, and its application. Background Technology

[0002] While geothermal resources are a renewable energy source, they are also finite, and the heat replenishment process is slow. Therefore, increasing the fluid flow rate in sandstone geothermal wells is crucial for the utilization of geothermal resources. Clay minerals are an important component of sandstone reservoirs. During seepage, clay minerals expand, disperse, and migrate, clogging porous media and increasing seepage resistance. As the reservoir temperature changes, scale ions such as calcium and magnesium silicates gradually precipitate, causing blockage of the formation.

[0003] The operation of geothermal systems can be divided into heating season and non-heating season. During this period, the seepage capacity of reinjection wells in geothermal systems tends to decline due to scaling, sand production, and mechanical impurities, severely restricting reinjection capacity. To address this issue, during the non-heating season, an environmentally friendly additive can be added to maintain the formation and wellbore, according to the production schedule.

[0004] During the non-heating season of geothermal well production, the present invention uses an environmentally friendly well-washing fluid to clean the aforementioned blockages, thus ensuring normal operation in the next heating season.

[0005] Currently, well-washing fluids are mainly developed for oil and gas extraction, where the fluid medium is complex. Therefore, most of the chemical agents used are non-degradable, resulting in complex composition and high cost. Furthermore, the bottom residue is treated during or before oil and gas extraction, so the existing system does not take into account the issue of formation residue. Summary of the Invention

[0006] Based on this, the present invention proposes a well-washing fluid that can be applied to improve the conductivity of sandstone geothermal wells, as well as its preparation method and application.

[0007] According to a first aspect of the present invention, a well-washing fluid for improving the conductivity of sandstone geothermal wells is provided, comprising, by weight percentage, the following components:

[0008] Glucose: 10%-30%;

[0009] Nano silica: 2%-5%;

[0010] Lignin or sodium lignin sulfonate: 1%-4%;

[0011] Quaternary ammonium salt surfactants: 0.1%-2%;

[0012] Cellulose acetate: 1%-4%;

[0013] Potassium chloride: 1%-2%;

[0014] Acrylamide dimethyl diethylenepropyl ammonium chloride: 0.2%-0.4%;

[0015] Chelating agent: 0.1%-0.2%; balance: water.

[0016] According to an embodiment of the present invention, the nano-silica particles have a particle size of 1 to 100 nm.

[0017] According to an embodiment of the present invention, the quaternary ammonium salt surfactant is bis(dimethyl) quaternary ammonium chloride and / or octadecyltrimethylammonium chloride.

[0018] According to an embodiment of the present invention, the chelating agent is one or more of BAPTA tetrasodium salt, polyaspartic acid, and sodium polyaspartate.

[0019] According to a second aspect of the present invention, a method for preparing a well-washing fluid to improve the conductivity of sandstone geothermal wells is provided, comprising the following steps:

[0020] Dissolve cellulose acetate in methanol according to the component requirements and stir until a homogeneous cellulose acetate solution without insoluble matter is formed;

[0021] Dissolve glucose, potassium chloride, nano-silica, lignin or sodium lignin sulfonate until completely dissolved to form a mixed solution;

[0022] Add quaternary ammonium salt surfactant, acrylamide dimethyl diethylenepropyl ammonium chloride, and chelating agent to the mixed solution until completely dissolved to obtain a semi-finished solution.

[0023] The cellulose acetate solution is added to the semi-finished product solution and stirred thoroughly to obtain the well-washing fluid that improves the conductivity of sandstone geothermal wells.

[0024] According to a third aspect of the present invention, an application of a well-washing fluid in reinjection wells of a geothermal system is provided.

[0025] According to embodiments of the present invention, the application of well-washing fluid in the plugging process of sandstone geothermal wells is included.

[0026] According to embodiments of the present invention, the application of a well-washing fluid is included after the acid washing process of a sandstone geothermal well.

[0027] As can be seen from the above technical solutions, the well-washing fluid for improving the conductivity of sandstone geothermal wells, its preparation method, and its application provided by the present invention have the following beneficial effects:

[0028] During the non-heating season of geothermal well production, the present invention uses an environmentally friendly well-washing fluid to clean the aforementioned blockages, thus ensuring normal operation in the next heating season.

[0029] The main function of the well-washing fluid provided by this invention is to reduce the electric double-layer repulsion of clay flaky scale, thereby inhibiting clay swelling. The system can dissociate into polynuclear hydroxy-bridged ions in water. These ions have a high positive charge and can tightly adsorb onto the negatively charged surface of the clay, thus inhibiting clay swelling.

[0030] The scale inhibition effect of this system is achieved through natural polymers, which inhibit scale formation by exchanging and complexing with metal ions. The abundant carboxyl groups in the system adsorb onto scale crystals, causing lattice dislocation and weakening intermolecular interactions, thus preventing precipitation.

[0031] The well-washing fluid provided by this invention is primarily applied to geothermal wells, solving the problem of chemical residue. All materials used in this system are naturally decomposable. Furthermore, this system mainly targets the aqueous phase, excluding oil and gas phases. Because the working medium is singular, materials can be optimized, reducing system costs. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0033] According to a first aspect of the present invention, a well-washing fluid for improving the conductivity of sandstone geothermal wells is provided, comprising, by weight percentage, the following components:

[0034] Glucose: 10%-30%;

[0035] Nano silica: 2%-5%;

[0036] Lignin or sodium lignin sulfonate: 1%-4%;

[0037] Quaternary ammonium salt surfactants: 0.1%-2%;

[0038] Cellulose acetate: 1%-4%;

[0039] Potassium chloride: 1%-2%;

[0040] Acrylamide dimethyl diethylenepropyl ammonium chloride: 0.2%-0.4%;

[0041] Chelating agent: 0.1%-0.2%; balance: water.

[0042] The raw materials added in this invention, such as glucose, lignin, and cellulose, are all natural and biodegradable materials. On the one hand, they act as clay stabilizers; on the other hand, their high solubility allows them to be flushed back to the surface with fluids, ensuring zero residue in the formation. The quaternary ammonium salt surfactants used in this system are common surfactants; only the solubility effect on clay and formation water needs to be considered, which can reduce the system cost. The potassium chloride and acrylamide dimethyl diethylenepropyl ammonium chloride added to this system can expel water from the already swollen bentonite lattice, achieving a shrinkage-swelling effect. Chelating agents improve the solubility of clay and formation scale, ensuring no residue in the formation. The compatibility and stability of the system were determined through compounding experiments.

[0043] During the non-heating season of geothermal well production, the present invention uses an environmentally friendly well-washing fluid to clean the aforementioned blockages, thus ensuring normal operation in the next heating season.

[0044] The main function of the well-washing fluid provided by this invention is to reduce the electric double-layer repulsion of clay flaky scale, thereby inhibiting clay swelling. The system can dissociate into polynuclear hydroxy-bridged ions in water. These ions have a high positive charge and can tightly adsorb onto the negatively charged surface of the clay, thus inhibiting clay swelling.

[0045] The scale inhibition effect of this system is achieved through natural polymers, which inhibit scale formation by exchanging and complexing with metal ions. The abundant carboxyl groups in the system adsorb onto scale crystals, causing lattice dislocation and weakening intermolecular interactions, thus preventing precipitation.

[0046] The well-washing fluid provided by this invention is primarily applied to geothermal wells, solving the problem of chemical residue. All materials used in this system are naturally decomposable. Furthermore, this system mainly targets the aqueous phase, excluding oil and gas phases. Because the working medium is singular, materials can be optimized, reducing system costs.

[0047] According to an embodiment of the present invention, the nano-silica particles have a particle size of 1 to 100 nm.

[0048] According to an embodiment of the present invention, the nano-silica does not require hydrophobic modification.

[0049] According to an embodiment of the present invention, the quaternary ammonium salt surfactant is bis(dimethyl) quaternary ammonium chloride and / or octadecyltrimethylammonium chloride. The quaternary ammonium salt is stable in alkaline water and no amine is released.

[0050] According to an embodiment of the present invention, the role of cellulose acetate is to block large pores during the injection process of the system, so that the system is distributed as evenly as possible.

[0051] According to an embodiment of the present invention, the chelating agent is one or more of BAPTA tetrasodium salt, polyaspartic acid, and sodium polyaspartate.

[0052] According to a second aspect of the present invention, a method for preparing a well-washing fluid to improve the conductivity of sandstone geothermal wells is provided, comprising the following steps:

[0053] Dissolve cellulose acetate in methanol according to the component requirements and stir until a homogeneous cellulose acetate solution without insoluble matter is formed;

[0054] Dissolve glucose, potassium chloride, nano-silica, lignin or sodium lignin sulfonate until completely dissolved to form a mixed solution;

[0055] Add quaternary ammonium salt surfactant, acrylamide dimethyl diethylenepropyl ammonium chloride, and chelating agent to the mixed solution until completely dissolved to obtain a semi-finished solution.

[0056] The cellulose acetate solution is added to the semi-finished product solution and stirred thoroughly to obtain the well-washing fluid that improves the conductivity of sandstone geothermal wells.

[0057] According to a third aspect of the present invention, an application of a well-washing fluid in reinjection wells of a geothermal system is provided.

[0058] Regarding the process: This system is used alone and is not compatible with other systems. Theoretically, it can be used in combination with other systems in a slug form, for example, after acid pickling, this system can be used for cleaning.

[0059] In terms of chemical composition: This system is not sensitive to acid-base systems and they do not affect each other.

[0060] According to embodiments of the present invention, the application of well-washing fluid in the plugging process of sandstone geothermal wells is included.

[0061] According to embodiments of the present invention, the application of a well-washing fluid is included after the acid washing process of a sandstone geothermal well.

[0062] The raw materials added in this invention, such as glucose, lignin, and cellulose, are all natural and biodegradable materials. On the one hand, they act as clay stabilizers; on the other hand, their high solubility allows them to be flushed back to the surface with fluids, ensuring zero residue in the formation. The quaternary ammonium salt surfactants used in this system are common surfactants; only the solubility effect on clay and formation water needs to be considered, which can reduce the system cost. The potassium chloride and acrylamide dimethyl diethylenepropyl ammonium chloride added to this system can expel water from the already swollen bentonite lattice, achieving a shrinkage-swelling effect. Chelating agents improve the solubility of clay and formation scale, ensuring no residue in the formation. The compatibility and stability of the system were determined through compounding experiments.

[0063] During the non-heating season of geothermal well production, the present invention uses an environmentally friendly well-washing fluid to clean the aforementioned blockages, thus ensuring normal operation in the next heating season.

[0064] The main function of the well-washing fluid provided by this invention is to reduce the electric double-layer repulsion of clay flaky scale, thereby inhibiting clay swelling. The system can dissociate into polynuclear hydroxy-bridged ions in water. These ions have a high positive charge and can tightly adsorb onto the negatively charged surface of the clay, thus inhibiting clay swelling.

[0065] The scale inhibition effect of this system is achieved through natural polymers, which inhibit scale formation by exchanging and complexing with metal ions. The abundant carboxyl groups in the system adsorb onto scale crystals, causing lattice dislocation and weakening intermolecular interactions, thus preventing precipitation.

[0066] The well-washing fluid provided by this invention is primarily applied to geothermal wells, solving the problem of chemical residue. All materials used in this system are naturally decomposable. Furthermore, this system mainly targets the aqueous phase, excluding oil and gas phases. Because the working medium is singular, materials can be optimized, reducing system costs.

[0067] The technical solution of the present invention will be described in detail below through preferred embodiments. It should be noted that the specific embodiments in the following text are for illustrative purposes only and are not intended to limit the present invention.

[0068] Example 1

[0069] Well-washing fluid formulation: Composed of the following components by mass percentage: glucose: 10%; nano silica: 2%; lignin: 1%; quaternary ammonium salt surfactant: 0.1%; cellulose acetate: 1%; potassium chloride: 1%; acrylamide dimethyl diethylenepropyl ammonium chloride: 0.2%; chelating agent: 0.1%; balance is wastewater purified by the 20-60℃ combined station.

[0070] Example 2

[0071] Well-washing fluid formulation: Composed of the following components by mass percentage: glucose: 30%; nano silica: 5%; lignin: 4%; quaternary ammonium salt surfactant: 2%; cellulose acetate: 4%; potassium chloride: 1%; acrylamide dimethyl diethylenepropyl ammonium chloride: 0.4%; chelating agent: 0.2%; balance is wastewater purified by the 20-60℃ joint station.

[0072] Example 3

[0073] Well-washing fluid formulation: Composed of the following components by mass percentage: glucose: 20%; nano silica: 3%; lignin: 3%; quaternary ammonium salt surfactant: 1%; cellulose acetate: 2%; potassium chloride: 1.2%; acrylamide dimethyl diethylenepropyl ammonium chloride: 0.3%; chelating agent: 0.1%; balance is wastewater purified by the 20-60℃ joint station.

[0074] Comparative Example 1

[0075] Same as Example 1, except that it does not contain cellulose acetate.

[0076] Comparative Example 2

[0077] Same as Example 1, except that it does not contain glucose.

[0078] Comparative Example 3

[0079] Same as Example 1, except that it does not contain lignin.

[0080] Comparative Example 4

[0081] Similar to the examples, except that it does not contain acrylamide dimethyl diethylenepropyl ammonium chloride.

[0082] Experiment Example 1: Anti-swelling and anti-swelling effect

[0083] Weigh 0.5g of bentonite into a 10mL centrifuge tube, add 10mL of the well-washing fluid provided in Examples 1-3 and Comparative Examples 1-4 respectively, let stand for 2 hours at a certain temperature, then place in a centrifuge and centrifuge at 1500r / min for 15min. Measure the volume V1 of the expanded bentonite after centrifugation. Following the same method, replace the clay stabilizer solution with 10mL of distilled water and kerosene respectively, and measure the expansion volumes V2 and V0 of the bentonite. Record the V2 data, then extract a certain amount of the supernatant from the centrifuge tube corresponding to the distilled water, add an equal amount of injection-enhancing and unblocking fluid, and prepare an injection-enhancing and unblocking fluid of a certain concentration. Similarly, shake well, let stand, centrifuge, and measure the volume V3 of the expanded bentonite after centrifugation.

[0084] The formulas for calculating the expansion rate and shrinkage rate are as follows:

[0085]

[0086]

[0087] In the formula, B1 is the anti-swelling rate (%); B2 is the shrinkage rate (%); V0 is the expansion volume of bentonite in kerosene (mL); V1 is the expansion volume of bentonite in the anti-swelling and shrinkage agent solution (mL); V2 is the expansion volume of bentonite in distilled water (mL); and V3 is the volume of bentonite after it has fully expanded in distilled water and then shrunk by the addition of the anti-swelling and shrinkage agent (mL).

[0088] Table 1. Effects of different temperatures on the anti-swelling and swelling rates of the well-washing fluid in Examples 1-3 and Comparative Examples 1-4.

[0089]

[0090]

[0091] As shown in Table 1, the well-washing fluids provided in Examples 1-3 of the present invention have certain effects on preventing swelling and reducing swelling at different temperatures.

[0092] By comparing Example 1 and Comparative Example 1, it can be seen that the anti-swelling rate and shrinkage rate of the well-washing fluid in Comparative Example 1 are roughly the same as those in Example 1 at different temperatures. This is because cellulose acetate plays a role in expanding the swept volume, and does not participate in the anti-swelling or shrinkage-swelling effects.

[0093] By comparing Example 1 and Comparative Example 2, it can be seen that the anti-swelling rate and shrinkage-swelling rate of the well-washing fluid in Comparative Example 2 are significantly worse than those in Example 1 at different temperatures. This is because glucose has an adsorption effect on clay, and the absence of glucose in this system leads to a poorer effect.

[0094] Comparing Example 1 and Comparative Example 3, it can be seen that in Comparative Example 3, the anti-swelling rate and shrinkage rate of the well-washing fluid at different temperatures decreased compared to Example 1, while the shrinkage rate showed no significant change. This is because lignin (mainly referring to lignin sulfonate) is an anionic surfactant with a certain spatial structure that can adsorb clay. The absence of lignin in this system leads to a poorer anti-swelling effect.

[0095] Comparing Example 1 and Comparative Example 4, it can be seen that the anti-swelling rate and shrinkage rate of the well-washing fluid in Comparative Example 4 are significantly lower than those in Example 1 at different temperatures. This is because acrylamide dimethyl diethylenepropyl ammonium chloride primarily adsorbs clay, causing the already swollen clay to shrink and swell. Since this system does not contain acrylamide dimethyl diethylenepropyl ammonium chloride, the anti-swelling rate and shrinkage effect are worse.

[0096] Experiment Example 2: Effect of Increased Injection on Unblocking

[0097] This experimental example analyzes the permeability of the well-washing fluids provided in Examples 1-3 and Comparative Examples 1-4 before and after injection.

[0098] The formula for penetration rate is:

[0099]

[0100] Where K is permeability, Q is displacement, A is the cross-sectional area of ​​the rock, L is the length of the rock, μ is the viscosity of water (taken as 1), and Δp is the pressure difference between the left and right ends of the core holder, read from a pressure gauge.

[0101] Example 1: In this experimental example, the original permeability K0 of the artificial core was 500 (10). -3 μm 2 ), 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 150 (10). -3 μm 2 The permeability decreased significantly. Then, 20 Pv of the washing fluid from Example 1 of this invention was injected in reverse, and it was found that the permeability of the core increased by 17%. Further injection of 100 Pv of the washing fluid of this invention for cleaning showed that the permeability of the core increased by 23.5% compared with the original permeability. Therefore, the washing fluid of this invention plays a role in improving the conductivity of sandstone geothermal wells.

[0102] Example 2: In this experimental example, the original permeability K0 of the artificial core was 516 (10). -3 μm 2 ), 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 198 (10). -3 μm 2 The permeability decreased significantly. Then, 20 Pv of the washing fluid of the present invention was injected in reverse, and it was found that the permeability of the core increased by 23%. Further injection of 100 Pv of the washing fluid of Example 2 was performed for cleaning, and it was found that the permeability of the core increased by 33% compared with the original permeability. Therefore, the washing fluid of the present invention plays a role in improving the conductivity of sandstone geothermal wells.

[0103] Example 3: In this experimental example, the original permeability K0 of the artificial core was 482 (10⁻³ μm). 2 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 121 (10⁻³ μm). 2 The permeability decreased significantly. Then, 20 Pv of the washing fluid of the present invention was injected in reverse, and it was found that the permeability of the core increased by 20%. Further injection of 100 Pv of the washing fluid of Example 3 was performed for cleaning, and it was found that the permeability of the core increased by 27% compared with the original permeability. Therefore, the washing fluid of the present invention plays a role in improving the conductivity of sandstone geothermal wells.

[0104] Comparative Example 1: In this experimental example, the original permeability K0 of the artificial core used was 490 (10) -3 μm 2 ), 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 130 (10). -3 μm 2The permeability decreased significantly. Then, 20 Pv of the washing fluid of this invention was injected in reverse, and the permeability of the core was found to increase by 16%. Further injection of 100 Pv of the washing fluid from Comparative Example 1 resulted in a 22% increase in permeability compared to the original permeability. Cellulose acetate is used to expand the swept volume. The core used in the core experiment was a standard core with a diameter of 2.5 cm. The effect of cellulose acetate on increasing permeability was not significant in the core experiment.

[0105] Comparative Example 2: In this experimental example, the original permeability K0 of the artificial core used was 495 (10). -3 μm 2 ), 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 140 (10). -3 μm 2 The permeability decreased significantly. Then, 20 Pv of the washing fluid of this invention was injected in reverse, and the permeability of the core was found to increase by 6%. Further injection of 100 Pv of the washing fluid from Comparative Example 2 resulted in a 2% increase in the permeability of the core compared to the original permeability. Glucose can effectively adsorb clay; however, this system does not contain glucose, leading to poorer adsorption and the system's inability to carry away bentonite.

[0106] Comparative Example 3: In this experimental example, the original permeability K0 of the artificial core used was 518 (10) -3 μm 2 ), 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 149 (10). -3 μm 2 The permeability decreased significantly. Then, 20 Pv of the washing fluid of this invention was injected in reverse, and the permeability of the core was found to increase by 15%. Further injection of 100 Pv of the washing fluid from Comparative Example 3 resulted in a 20% increase in the permeability of the core compared to the original permeability. Lignin can effectively adsorb clay; however, this system does not contain lignin, leading to poorer adsorption and the system's inability to carry away bentonite.

[0107] Comparative Example 4: In this experimental example, the original permeability K0 of the artificial core used was 532 (10). -3 μm 2 ), 0.5 PV of clay was injected forward into the core sample using alcohol. After displacing 10 PV with formation water and injecting 50 PV of water, the permeability K1 decreased to 159 (10). -3 μm 2The permeability decreased significantly. Then, 20 Pv of the washing fluid of this invention was injected in reverse, and the permeability of the core was found to increase by 1%. Further injection of 100 Pv of the washing fluid from Comparative Example 4 resulted in a 2% increase in permeability compared to the original permeability. This system does not contain acrylamide dimethyldiethylenepropylammonium chloride, and therefore cannot shrink or expand the already swollen clay. In core experiments, shrinkage and swelling are the first step, and adsorption and transport are the second. Without shrinkage and swelling, the system cannot carry away the bentonite, leading to poor core experiment results.

[0108] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A well-washing fluid for improving the conductivity of sandstone geothermal wells, characterized in that, By weight percentage, it includes the following components: Glucose: 10%-30%; Nano silica: 2%-5%; Lignin or sodium lignin sulfonate: 1%-4%; Quaternary ammonium salt surfactants: 0.1%-2%; Cellulose acetate: 1%-4%; Potassium chloride: 1%-2%; Acrylamide dimethyl diethylenepropyl ammonium chloride: 0.2%-0.4%; Chelating agent: 0.1%-0.2%; balance: water.

2. The well-washing fluid for improving the conductivity of sandstone geothermal wells according to claim 1, characterized in that, The nano-silica particles have a diameter of 1–100 nm.

3. The well-washing fluid for improving the conductivity of sandstone geothermal wells according to claim 1, characterized in that, The quaternary ammonium salt surfactant is bis(dimethyl) quaternary ammonium chloride and / or octadecyltrimethylammonium chloride.

4. The well-washing fluid for improving the conductivity of sandstone geothermal wells according to claim 1, characterized in that, The chelating agent is one or more of BAPTA tetrasodium salt, polyaspartic acid, and sodium polyaspartate.

5. A method for preparing a well-washing fluid for improving the conductivity of sandstone geothermal wells as described in any one of claims 1-4, characterized in that, Includes the following steps: Dissolve cellulose acetate in methanol according to the component requirements and stir until a homogeneous cellulose acetate solution without insoluble matter is formed; Dissolve glucose, potassium chloride, nano-silica, lignin or sodium lignin sulfonate until completely dissolved to form a mixed solution; Add quaternary ammonium salt surfactant, acrylamide dimethyl diethylenepropyl ammonium chloride, and chelating agent to the mixed solution until completely dissolved to obtain a semi-finished solution. The cellulose acetate solution is added to the semi-finished product solution and stirred thoroughly to obtain the well-washing fluid that improves the conductivity of sandstone geothermal wells.

6. The application of the well-washing fluid according to any one of claims 1-4 in the reinjection well of a geothermal system.

7. The well-washing fluid for improving the conductivity of sandstone geothermal wells according to claim 6, characterized in that, This includes the application of the well-washing fluid in the plugging process of sandstone geothermal well sections.

8. The well-washing fluid for improving the conductivity of sandstone geothermal wells according to claim 6, characterized in that, This includes the application of the well-washing fluid after the acid washing process in sandstone geothermal wells.

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