Preparation method and application of water-soluble temporary plugging agent

Abstract

The application relates to the technical field of petroleum chemical industry, and discloses a preparation method and application of a water-soluble temporary plugging agent. A dipropylene acid ester monomer is reacted with a 2-[(2-aminoethyl)amino] ethanesulfonic acid sodium salt, and then ion crosslinking is carried out with a chitosan quaternary ammonium salt to obtain the water-soluble temporary plugging agent. The temporary plugging agent contains biodegradable and hydrolyzable ester groups, hydrophilic ether bonds and sulfonate groups, and the bio-based chitosan quaternary ammonium salt is used as a crosslinking agent, so that the temporary plugging agent has excellent degradable performance and the damage to a reservoir is reduced. The quaternary ammonium salt cation of chitosan and the sulfonate anion of the temporary plugging agent precursor form electrostatic interaction, the temporary plugging agent precursor forms a three-dimensional gel network structure through ion crosslinking, realizes high-strength and plugging effects, the temporary plugging agent has high hydrophilicity and good water solubility, the plugging removal performance of the temporary plugging agent can be improved, and the temporary plugging agent is convenient for post-period flowback.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, specifically to a method for preparing and applying a water-soluble temporary plugging agent. Background Technology

[0002] Hydraulic fracturing is a core technology for enhancing production in low-permeability, tight oil and gas, and shale reservoirs. Temporary plugging and diversion techniques are crucial, enabling balanced fracture initiation across multiple fracture clusters in horizontal wells and expanding reservoir stimulation volume. Currently, mainstream temporary plugging agents are mainly classified as rigid granular types, ordinary water-soluble gels, and polyester-based biodegradable materials. However, these agents have low water solubility, making them difficult to adapt to water-based fracturing systems, and they are difficult to flow back after unplugging, potentially causing permanent damage to the reservoir.

[0003] With the upgrading of environmental protection development policies, oilfields have put forward requirements for fracturing chemical additives such as low harm and biodegradability. However, conventional non-degradable rigid plugging agents have problems such as residue pollution, difficulty in subsequent flowback, and damage to the reservoir. Therefore, the development of biodegradable plugging agents is of great significance. Patent CN120737824B discloses a water-soluble plugging agent for oil well fracturing and its preparation method. It uses sodium lignosulfonate / graphene oxide as the core, coats the core surface with polyacrylic acid-polyacrylamide copolymer, and then coats it with acrylate-modified chitosan. The resulting plugging agent has excellent sealing performance, dissolving performance, and shear resistance. However, the plugging agent of this patent is difficult to biodegrade and will damage the reservoir. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing and applying a water-soluble temporary plugging agent, solving the problems of poor water solubility and difficulty in degradation of the temporary plugging agent.

[0005] The technical solution of this invention: A method for preparing a water-soluble temporary plugging agent: (1) Add dihydroxy monomer and triethylamine to dichloromethane, add acryloyl chloride dropwise in an ice bath, stir the reaction, add water, extract with dichloromethane, collect the organic layer, concentrate under reduced pressure and dry, separate by column chromatography, and elute with a solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 to obtain the diacrylate monomer. The reaction formula is: .

[0006] (2) Add diacrylate monomer and an aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to methanol, stir the reaction under a nitrogen atmosphere, concentrate the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary plugging agent precursor. The reaction formula is: .

[0007] (3) Add the temporary plugging agent precursor and chitosan quaternary ammonium salt to the water, stir to crosslink, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain a water-soluble temporary plugging agent.

[0008] Furthermore, in (1), the reaction temperature is 15-35℃ and the reaction time is 1-2h.

[0009] Furthermore, in (1), the molar ratio of dihydroxy monomer, triethylamine, and acryloyl chloride is 1:(2.8-3):(2-2.3).

[0010] Furthermore, the structural formula of the dihydroxy monomer in (1) is: , where a is 1-4.

[0011] Furthermore, in (2), the reaction temperature is 50-65℃ and the reaction time is 24-30h.

[0012] Furthermore, in (2), the molar ratio of diacrylate monomer and sodium 2-[(2-aminoethyl)amino]ethanesulfonate is (1.4-1.6):1.

[0013] Furthermore, (3) the mass ratio of the temporary plugging agent precursor to chitosan quaternary ammonium salt is 100:(2-5).

[0014] Furthermore, in (3), the crosslinking temperature is 10-40℃ and the crosslinking time is 1-6h.

[0015] Furthermore, water-soluble temporary plugging agents are applied in oilfield fracturing technology.

[0016] The beneficial technical effects of this invention are as follows: A diacrylate monomer containing an ether bond is polymerized with sodium 2-[(2-aminoethyl)amino]ethanesulfonate containing a sulfonate group via a Michael addition reaction to obtain a temporary plugging agent precursor. Then, the sulfonate group is ionically crosslinked with chitosan quaternary ammonium salt to obtain a water-soluble temporary plugging agent. This temporary plugging agent has a main chain containing biodegradable and hydrolyzable ester groups, as well as hydrophilic ether bonds in the main chain and hydrophilic sulfonate groups in the side chains, further improving its hydrolytic performance. Furthermore, the use of bio-based chitosan quaternary ammonium salt as a crosslinking agent endows the temporary plugging agent with excellent degradability, reducing damage to the reservoir.

[0017] In this invention, the quaternary ammonium salt cation of chitosan interacts electrostatically with the sulfonate anion of the temporary plugging agent precursor, enabling the temporary plugging agent precursor to form a three-dimensional gel network structure through ionic cross-linking. This achieves a high-strength, plugging effect. At the same time, the temporary plugging agent has high hydrophilicity and good water solubility, which can improve the unblocking performance of the temporary plugging agent and facilitate subsequent backflow. Detailed Implementation

[0018] The following embodiments are further illustrations of the present invention, but should not be construed as limiting the scope of protection of the present invention. Any non-essential modifications made to the present invention based on the above description shall still fall within the scope of protection of the present invention.

[0019] Example 1: (1) Add 40 mmol of triethylene glycol and 120 mmol of triethylamine to 90 mL of dichloromethane. Add 92 mmol of acryloyl chloride dropwise in an ice bath. Stir the reaction at 20 °C for 1 h. Add water, extract with dichloromethane, collect the organic layer, concentrate under reduced pressure, dry, and separate by column chromatography. Elute with a solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 to obtain the diacrylate monomer, with the structural formula as follows: .

[0020] (2) Add 30 mmol of diacrylate monomer and 25 mL of aqueous solution containing 20 mmol of sodium 2-[(2-aminoethyl)amino]ethanesulfonate (CAS No. 34730-59-1) to 120 mL of methanol. Heat to 65 °C under nitrogen atmosphere and stir for 24 h. During the reaction, reflux the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary blockage agent precursor.

[0021] (3) Add 10g of temporary plugging agent precursor and 0.2g of chitosan quaternary ammonium salt to 60mL of water, stir and crosslink at 20℃ for 1h, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain water-soluble temporary plugging agent.

[0022] Example 2: (1) Add 40 mmol triethylene glycol and 120 mmol triethylamine to 90 mL dichloromethane, add 80 mmol acryloyl chloride dropwise in an ice bath, stir the reaction at 20 °C for 2 h, add water, extract with dichloromethane, collect the organic layer, concentrate under reduced pressure and dry, separate by column chromatography, and elute with a solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 to obtain the diacrylate monomer.

[0023] (2) Add 32 mmol of diacrylate monomer and 25 mL of aqueous solution containing 20 mmol of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to 120 mL of methanol. Heat to 50 °C under a nitrogen atmosphere and stir for 30 h. During the reaction, reflux the solution under reduced pressure, concentrate the solution, wash the product with acetone, and dry to obtain the temporary blockage agent precursor.

[0024] (3) Add 10g of temporary plugging agent precursor and 0.3g of chitosan quaternary ammonium salt to 60mL of water, stir and crosslink at 25℃ for 1h, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain water-soluble temporary plugging agent.

[0025] Example 3: (1) Add 40 mmol of triethylene glycol and 112 mmol of triethylamine to 90 mL of dichloromethane, add 92 mmol of acryloyl chloride dropwise in an ice bath, stir the reaction at 25 °C for 1 h, add water, extract with dichloromethane, collect the organic layer, concentrate under reduced pressure and dry, separate by column chromatography, and elute with a solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 to obtain the diacrylate monomer.

[0026] (2) Add 32 mmol of diacrylate monomer and 25 mL of aqueous solution containing 20 mmol of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to 120 mL of methanol. Heat to 60 °C under nitrogen atmosphere and stir for 24 h. During the reaction, reflux the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary blockage agent precursor.

[0027] (3) Add 10g of temporary plugging agent precursor and 0.4g of chitosan quaternary ammonium salt to 70mL of water, stir and crosslink at 20℃ for 2h, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain water-soluble temporary plugging agent.

[0028] Example 4: (1) Add 40 mmol triethylene glycol and 120 mmol triethylamine to 90 mL dichloromethane, add 80 mmol acryloyl chloride dropwise in an ice bath, stir the reaction at 25 °C for 1 h, add water, extract with dichloromethane, collect the organic layer, concentrate under reduced pressure and dry, separate by column chromatography, and elute with a solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 to obtain the diacrylate monomer.

[0029] (2) Add 30 mmol of diacrylate monomer and 25 mL of aqueous solution containing 20 mmol of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to 120 mL of methanol. Heat to 50 °C under a nitrogen atmosphere and stir for 30 h. During the reaction, reflux the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary blockage agent precursor.

[0030] (3) Add 10g of temporary plugging agent precursor and 0.5g of chitosan quaternary ammonium salt to 70mL of water, stir and crosslink at 20℃ for 2h, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain water-soluble temporary plugging agent.

[0031] Comparative Example 1 uses the temporary plugging agent precursor prepared in Example 1 as the temporary plugging agent.

[0032] Comparative Example 2: (2) Add 30 mmol of ethylene glycol dimethacrylate and 25 mL of an aqueous solution containing 20 mmol of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to 120 mL of methanol. Heat to 65 °C under a nitrogen atmosphere and stir for 24 h. During the reaction, reflux the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary blockage agent precursor.

[0033] (3) Add 10g of temporary plugging agent precursor and 0.2g of chitosan quaternary ammonium salt to 60mL of water, stir and crosslink at 20℃ for 1h, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain the temporary plugging agent.

[0034] Comparative Example 3: (1) Add 30 mmol of diacrylate monomer and 25 mL of aqueous solution containing 20 mmol of N-methylethylenediamine to 120 mL of methanol. Heat to 65 °C under nitrogen atmosphere and stir for 24 h. During the reaction, reflux the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary blockage agent precursor.

[0035] (2) Add 10g of temporary plugging agent precursor and 0.2g of chitosan quaternary ammonium salt to 60mL of water, stir and crosslink at 20℃ for 1h, heat the solution to evaporate until the precipitate is precipitated, then cool in an ice bath, filter and dry the precipitate to obtain the temporary plugging agent.

[0036] Degradation performance was tested according to GB / T 19277.1-2025.

[0037] A temporary plugging agent was added to formation water (mineralization 12755.8 mg / L) to prepare a 15 g / L solution. Temporary plugging and unplugging tests were then performed on a dry core sample: the core was saturated with formation water, and the permeability K0 was measured; then 2 PV of the temporary plugging agent solution was injected, and the permeability K1 was measured; finally, the core was flushed with formation water, and the permeability K2 was measured. The temporary plugging rate W and the unplugging rate Q were calculated. W = (K0 - K1) / K0 × 100%. Q = K2 / K1 × 100%.

[0038] Table 1

[0039] The water-soluble temporary plugging agents of each embodiment exhibit higher biodegradability, excellent degradability, and are environmentally friendly. They also demonstrate good temporary plugging and unblocking rates, primarily because the main chain of the temporary plugging agent contains biodegradable and hydrolyzable ester groups, along with hydrophilic ether bonds and hydrophilic sulfonate groups in the side chains. This further enhances the hydrolytic performance of the temporary plugging agent. Furthermore, the use of bio-based chitosan quaternary ammonium salt as a crosslinking agent endows the temporary plugging agent with excellent degradability. Simultaneously, the quaternary ammonium salt cations of chitosan interact electrostatically with the sulfonate anions of the temporary plugging agent precursor, enabling the precursor to form a three-dimensional gel network structure through ionic crosslinking, achieving a high-strength, plugging-resistant effect. Additionally, the high hydrophilicity and good water solubility of the temporary plugging agent improve its unblocking performance.

[0040] The temporary plugging agent precursor in Comparative Example 1 did not contain chitosan quaternary ammonium salt crosslinking agent, and therefore did not form a three-dimensional gel network structure, resulting in a very low temporary plugging rate.

[0041] The ethylene glycol dimethacrylate and the prepared temporary plugging agent in Comparative Example 2 do not contain ether bonds, which affects the water solubility of the temporary plugging agent and results in a lower biodegradation rate and unblocking rate.

[0042] The N-methylethylenediamine in Comparative Example 3 and the prepared temporary plugging agent do not contain sulfonate groups, which affects the hydrolysis performance of the temporary plugging agent, resulting in a low biodegradation rate. Furthermore, they cannot crosslink with chitosan quaternary ammonium salt ions to form a three-dimensional gel network structure, leading to a very low temporary plugging rate.

[0043] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a water-soluble temporary plugging agent, characterized in that, The preparation method includes: S1. Add diacrylate monomer and an aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to methanol, stir the reaction under nitrogen atmosphere, concentrate the solution under reduced pressure, wash the product with acetone, and dry to obtain the temporary plugging agent precursor. S2. Add the temporary plugging agent precursor and chitosan quaternary ammonium salt to water, stir to crosslink, heat the solution to evaporate until the precipitate is formed, then cool in an ice bath, filter and dry the precipitate to obtain a water-soluble temporary plugging agent.

2. The method for preparing the water-soluble temporary plugging agent according to claim 1, characterized in that, The reaction temperature in S1 is 50-65℃, and the reaction time is 24-30h.

3. The method for preparing the water-soluble temporary plugging agent according to claim 1, characterized in that, The molar ratio of diacrylate monomer and sodium 2-[(2-aminoethyl)amino]ethanesulfonate in S1 is (1.4-1.6):

1.

4. The method for preparing the water-soluble temporary plugging agent according to claim 3, characterized in that, The method for preparing the diacrylate monomer includes: adding dihydroxy monomer and triethylamine to dichloromethane, adding acryloyl chloride dropwise in an ice bath, stirring the reaction at 15-35℃ for 1-2 hours, adding water, extracting with dichloromethane, collecting the organic layer, concentrating under reduced pressure and drying, and separating by column chromatography to obtain the diacrylate monomer.

5. The method for preparing the water-soluble temporary plugging agent according to claim 4, characterized in that, The molar ratio of the dihydroxy monomer, triethylamine, and acryloyl chloride is 1:(2.8-3):(2-2.3).

6. The method for preparing the water-soluble temporary plugging agent according to claim 4, characterized in that, The structural formula of the dihydroxy monomer is as follows: , where a is 1-4.

7. The method for preparing the water-soluble temporary plugging agent according to claim 1, characterized in that, The mass ratio of the temporary plugging agent precursor to chitosan quaternary ammonium salt in S1 is 100:(2-5).

8. The method for preparing the water-soluble temporary plugging agent according to claim 1, characterized in that, The cross-linking temperature in S2 is 10-40℃, and the cross-linking time is 1-6h.

9. The application of a water-soluble temporary plugging agent prepared by any one of claims 1-8 in oilfield fracturing technology.

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