A sodium alginate / quaternary ammonium salt composite material and its preparation and application

Abstract

This invention discloses a sodium alginate / quaternary ammonium salt composite material, wherein the sodium alginate / quaternary ammonium salt is attached to a sodium alginate sponge, wherein the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1 to 10:1, the pore size of the sodium alginate sponge is 80-83%, and the quaternary ammonium salt comprises quaternary ammonium salt monomers and quaternary ammonium salt polymers. This invention also discloses its preparation and application. This invention addresses the content and properties of metal ions during oil and gas field development, using a tiered treatment approach to solve the impact of metal ions on the recycling system, simultaneously achieving the resource recovery goal of metal ions, and supporting the green and sustainable development of oil and gas fields.

Description

Technical Field

[0001] This invention relates to a sodium alginate / quaternary ammonium salt composite material, its preparation and application. Background Technology

[0002] Large-scale hydraulic fracturing technology is used in some oil and gas development processes, resulting in significant freshwater consumption and the generation of large quantities of fracturing flowback fluid. Due to the high mineralization and heavy metal content of this flowback fluid, it presents several challenges. First, the flowback fluid needs to be reused to replenish freshwater resources, necessitating the removal of metal ions, such as hardness ions like calcium and magnesium, which increases processing costs. Second, the flowback fluid contains metal ions from the formation, which can act as catalysts for certain reactions, such as transition metals like iron and manganese, and can also serve as important raw materials, such as rare metals like lithium. Therefore, it is necessary to coordinate the reuse of water resources and the resource recovery of metal materials from the flowback fluid, exploring the optimal pathways and practices for resource recovery and cost control.

[0003] Flowback fluids have a complex composition, with interactions between particulate matter, organic matter, and metal ions, requiring tiered treatment based on pollution characteristics and effective recovery of material resources. However, existing treatment systems do not fully consider the differences in the properties of substances, and improvements are needed in pollutant removal and material recovery. Hardness ions have a significant impact on the quality of recycled flowback fluid, making hardness removal technology the most commonly used treatment unit. Patent CN111423011B discloses a method for treating and reusing shale gas fracturing flowback fluid, targeting shale gas flowback fluid, adjusting the pH to 7-8 (slightly alkaline), and using ethylenediaminetetraacetic acid, sodium pyrophosphate, and glycolic acid as metal ion complexing agents to treat hardness ions. However, under certain conditions, the complexes can dissociate and release hardness ions. Patent CN113526730A uses inorganic salt sodium sulfate for hardness removal treatment of fracturing flowback fluid. Because calcium sulfate is only slightly soluble, the removal effect of calcium ions is poor, and it has no precipitation effect on magnesium ions. Furthermore, existing technologies and processes for treating metal ions are relatively singular, either focusing solely on treatment and ultimately converting the metal ions back into waste, or only emphasizing the treatment and recovery of rare metals such as lithium. For example, patent CN 112723395 A discloses a lithium resource recovery process for shale gas fracturing flowback fluid, placing lithium recovery as the first step. This not only results in relatively high processing costs, but the ion sieve-type adsorbent used is also susceptible to interference from other metal ions, while neglecting the resource recovery of other substances that can serve as catalysts. Summary of the Invention

[0004] This invention is made to further improve the reuse efficiency of oil and gas development flowback fluids and to better realize the comprehensive utilization of recovered metal ions from oil and gas development flowback fluids.

[0005] As one aspect of the present invention, a sodium alginate / quaternary ammonium salt composite material is provided, wherein the sodium alginate / quaternary ammonium salt is attached to a sodium alginate sponge, wherein the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1 to 10:1, the pore size of the sodium alginate sponge is 80 to 83%, and the quaternary ammonium salt comprises quaternary ammonium salt monomers and quaternary ammonium salt polymers.

[0006] In a specific embodiment, the mass ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is 1:3 to 1:5, wherein the quaternary ammonium salt monomer is selected from methacryloyloxyethyltrimethylammonium chloride or dimethyldiallylammonium chloride; and the quaternary ammonium salt polymer is selected from polyepichlorohydrin or polydimethyldiallylammonium chloride.

[0007] As another aspect of the present invention, a method for preparing the above-mentioned sodium alginate / quaternary ammonium salt composite material is provided, comprising:

[0008] (1) Sodium bicarbonate was added to sodium alginate solution and freeze-dried to obtain sodium alginate sponge.

[0009] (2) Sodium alginate sponge is soaked in quaternary ammonium salt solution, and quaternary ammonium salt is dispersed to the surface and pores of the sponge by ultrasound. Then, the sodium alginate sponge with quaternary ammonium salt is dried to obtain sodium alginate / quaternary ammonium salt composite material.

[0010] In a specific embodiment, the mass ratio of sodium alginate to sodium bicarbonate is 4:1 to 6:1.

[0011] In a specific embodiment, the mass concentration of the sodium alginate solution is 30-50%, preferably 40-50%.

[0012] In a specific embodiment, the mass concentration of the quaternary ammonium salt solution is 4-7%.

[0013] As another aspect of the present invention, a method for recycling oil and gas development backflow fluid is provided, using the aforementioned sodium alginate / quaternary ammonium salt composite material.

[0014] The backflow fluid contains a variety of metal ions, and existing processes do not fully consider the added value of these metal ions. Besides conducting research on the recovery of some rare metal ions, it is necessary to consider resource recovery during the metal ion treatment process, achieving comprehensive control over the entire process of waste harmlessness, volume reduction, and resource utilization. Therefore, this invention addresses the content and properties of metal ions during oil and gas field development, using a tiered treatment approach to solve the impact of metal ions on the reuse treatment system, simultaneously achieving the goal of metal ion resource utilization, and supporting the green and sustainable development of oil and gas fields.

[0015] The present invention provides a method for treating backflow liquid that solves the problems of long process flow, large area coverage, and high dosage of traditional treatment processes. It achieves rapid reuse and reinjection of backflow liquid through a combination of effects such as debinding, separation, and hardening removal. Detailed Implementation

[0016] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0017] Oil and gas development flowback fluids are diverse, including drilling waste fluids, fracturing flowback fluids, and well cleaning / workover waste fluids, with varying contaminant concentrations. Viscosities range from approximately 2 to 30 mp·s, and hardness from approximately 300 to 3000 mg / L. To more efficiently treat these waste fluids, they are categorized into four systems: low-hardness high-viscosity, low-hardness low-viscosity, high-hardness low-viscosity, and high-hardness high-viscosity. Low viscosity systems have a viscosity of 2–10 mp·s, high viscosity systems have a viscosity of 10–30 mp·s, low hardness systems have a viscosity of 300–1000 mg / L, and high hardness systems have a viscosity of 1000–3000 mg / L.

[0018] In this embodiment of the invention, the basic steps for preparing the sodium alginate / quaternary ammonium salt composite material are as follows:

[0019] (1) Sodium bicarbonate was added to sodium alginate solution and freeze-dried to obtain sodium alginate sponge.

[0020] (2) Sodium alginate sponge was soaked in quaternary ammonium salt solution, and the quaternary ammonium salt was dispersed to the surface and pores of the sponge by ultrasound (40 kHz, 10 min). The sodium alginate sponge with quaternary ammonium salt was then dried to obtain sodium alginate / quaternary ammonium salt composite material.

[0021] In this embodiment of the invention, the basic steps for verifying the effect of sodium alginate / quaternary ammonium salt composite material on the treatment of backflow liquid are as follows:

[0022] The sodium alginate / quaternary ammonium salt composite material of the present invention is packed into a column (with an inner diameter of 2-4 cm) and the column height is (5-15 cm);

[0023] After the return liquid is treated with oxygen-releasing agents (calcium peroxide and magnesium peroxide) and the scum is removed, it is pumped at a flow rate of 10-30 mL / min and flows from bottom to top through the sodium alginate / quaternary ammonium salt composite material of the present invention.

[0024] For flowback liquids with different hardness and viscosity, different sodium alginate / quaternary ammonium salt composite materials can be selected. The following describes the treatment of flowback liquids with sodium alginate / quaternary ammonium salt composite materials prepared under different conditions, calculating the hardness reduction rate and viscosity reduction rate. The effects of factors such as the mass concentration of sodium alginate, the mass concentration of sodium bicarbonate, the type and mass concentration of the quaternary ammonium salt, and the volume ratio of the sodium alginate sponge to the quaternary ammonium salt solution on the final results are investigated. The quaternary ammonium salts used in the embodiments of this invention are: quaternary ammonium salt monomers: methacryloyloxyethyltrimethylammonium chloride (denoted as A), dimethyldiallylammonium chloride (denoted as B); quaternary ammonium salt polymers: polyepoxychloropropaneamine (denoted as C), polydimethyldiallylammonium chloride (denoted as D).

[0025] The treatment results of low-hardness, high-viscosity backflow fluid are shown in Table 1.

[0026] Table 1 Examples of low-hardness, high-viscosity (hardness 520 mg / L, viscosity 20 mp·s) systems

[0027]

[0028]

[0029] Summarize:

[0030] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 1-2 is a sodium alginate sponge with quaternary ammonium salts attached, wherein the quaternary ammonium salts are A and B, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 3:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 2:1, and the porosity of the sodium alginate sponge is 70%.

[0031] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 3-4 is a sodium alginate sponge with quaternary ammonium salt attached, wherein the quaternary ammonium salt is C or D, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 5:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 2:1, and the porosity of the sodium alginate sponge is 70%.

[0032] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 5-6 is a sodium alginate sponge with quaternary ammonium salt attached, wherein the quaternary ammonium salt is A or B, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 5:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 4:1, and the porosity of the sodium alginate sponge is 77%.

[0033] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 7-8 is a sodium alginate sponge with attached quaternary ammonium salts, wherein the quaternary ammonium salts are C and D, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 4:1, and the porosity of the sodium alginate sponge is 77%.

[0034] The sodium alginate / quaternary ammonium salt composite materials prepared in Examples 9-12 are sodium alginate sponges with attached quaternary ammonium salts. The quaternary ammonium salts are AC, AD, BC, and BD composite quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 77%.

[0035] The sodium alginate / quaternary ammonium salt composite material prepared in Example 13 is a sodium alginate sponge with attached quaternary ammonium salt, wherein the quaternary ammonium salt is AC, and the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate, and the mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0036] The sodium alginate / quaternary ammonium salt composite material prepared in Example 14 is a sodium alginate sponge with quaternary ammonium salt attached, wherein the quaternary ammonium salt is AD, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 4:1, and the porosity of the sodium alginate sponge is 80%.

[0037] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 15-16 is a sodium alginate sponge with attached quaternary ammonium salt, wherein the quaternary ammonium salt is BC, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 4:1, and the porosity of the sodium alginate sponge is 80%.

[0038] The sodium alginate / quaternary ammonium salt composite material prepared in Example 17 is a sodium alginate sponge with attached quaternary ammonium salts, wherein the quaternary ammonium salts are BC and BD, and the mass ratio of the sodium alginate sponge to the quaternary ammonium salts is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate, and the mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0039] The sodium alginate / quaternary ammonium salt composite material prepared in Example 18 is a sodium alginate sponge with quaternary ammonium salt attached, wherein the quaternary ammonium salt is BC or BD, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1, wherein the sodium alginate sponge contains sodium alginate and sodium bicarbonate, the mass ratio of sodium alginate to sodium bicarbonate is 6:1, and the porosity of the sodium alginate sponge is 83%.

[0040] Based on the above, we can conclude that:

[0041] The sodium alginate / quaternary ammonium salt composite material of the present invention has a good treatment effect on low-hardness, high-viscosity backflow liquid when the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 5:1 to 10:1, the mass ratio of the sodium alginate to the sodium bicarbonate is 2:1 to 5:1, and the pore size of the sodium alginate sponge is 77 to 83%.

[0042] Similarly, when the ratio of sodium alginate to sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has a significant impact on the final result. When the mass concentration of the sodium alginate solution is 20-50% (preferably 40-50%), the pore size of the formed sodium alginate sponge is more suitable, which is beneficial to improving the treatment effect of low-hardness, high-viscosity backflow liquid.

[0043] Sodium alginate / quaternary ammonium salt composite material prepared by mixing quaternary ammonium salt monomers and quaternary ammonium salt polymers has a better treatment effect on low-hardness, high-viscosity backflow liquid. The preferred ratio of quaternary ammonium salt monomers to quaternary ammonium salt polymers is 1:3 to 1:5. When the mass concentration of quaternary ammonium salt solution is 5 to 7%, the adhesion state of quaternary ammonium salt on sodium alginate sponge is more conducive to the treatment of low-hardness, high-viscosity backflow liquid.

[0044] Under the established optimal conditions for treating low-hardness, high-viscosity systems, good treatment results cannot be achieved for low-hardness, low-viscosity systems, high-hardness, high-viscosity systems, and high-hardness, low-viscosity systems. Therefore, further optimization of the treatment conditions is required. Table 2 shows examples for low-hardness, low-viscosity systems.

[0045] Table 2 Examples of low-hardness, low-viscosity (hardness 610 mg / L, viscosity 8 mp·s) systems

[0046]

[0047] Summarize:

[0048] The sodium alginate / quaternary ammonium salt composite materials prepared in Examples 19-22 are sodium alginate sponges with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 77%.

[0049] The sodium alginate / quaternary ammonium salt composite materials prepared in Examples 23-26 are sodium alginate sponges with attached quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 9:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate, and the mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0050] The sodium alginate / quaternary ammonium salt composite material prepared in Example 27 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0051] The sodium alginate / quaternary ammonium salt composite material prepared in Example 28 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0052] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 29-30 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0053] The sodium alginate / quaternary ammonium salt composite material prepared in Example 31 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0054] The sodium alginate / quaternary ammonium salt composite material prepared in Example 32 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0055] Based on the above, we can conclude that:

[0056] The sodium alginate / quaternary ammonium salt composite material of the present invention has a good treatment effect on low-hardness and low-viscosity backflow liquid when the mass ratio of sodium alginate sponge to quaternary ammonium salt is 8.3:1 to 10:1, the mass ratio of sodium alginate to sodium bicarbonate is 4:1 to 6:1, and the pore size of sodium alginate sponge is 80 to 83%.

[0057] Similarly, when the ratio of sodium alginate to sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has a significant impact on the final result. When the mass concentration of the sodium alginate solution is 30-60% (preferably 30-50%), the pore size of the formed sodium alginate sponge is more suitable, which is beneficial to improving the treatment effect of low-hardness and low-viscosity backflow liquid.

[0058] Sodium alginate / quaternary ammonium salt composite material prepared by mixing quaternary ammonium salt monomers and quaternary ammonium salt polymers has a better treatment effect on low-hardness and low-viscosity backflow liquid. The preferred ratio of quaternary ammonium salt monomers to quaternary ammonium salt polymers is 1:3 to 1:5. When the mass concentration of quaternary ammonium salt solution is 4 to 7%, the adhesion state of quaternary ammonium salt on sodium alginate sponge is more conducive to the treatment of low-hardness and low-viscosity backflow liquid.

[0059] Similarly, the process conditions were optimized for the high-hardness, high-viscosity system and the high-hardness, low-viscosity system. Table 3 shows an example of the high-hardness, high-viscosity system.

[0060] Table 3 Examples of High-Hardness, High-Viscosity (Hardness 2500 mg / L, Viscosity 32 mp·s) Systems

[0061]

[0062]

[0063] Summarize:

[0064] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 33-34 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 77%.

[0065] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 35-36 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 9:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0066] The sodium alginate / quaternary ammonium salt composite material prepared in Example 37 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0067] The sodium alginate / quaternary ammonium salt composite material prepared in Example 38 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0068] The sodium alginate / quaternary ammonium salt composite material prepared in Example 39 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0069] The sodium alginate / quaternary ammonium salt composite material prepared in Example 40 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0070] Based on the above, we can conclude that:

[0071] The sodium alginate / quaternary ammonium salt composite material of the present invention has a better treatment effect on high-hardness and high-viscosity backflow liquid when the mass ratio of sodium alginate sponge to quaternary ammonium salt is 8.3:1 to 10:1, the mass ratio of sodium alginate to sodium bicarbonate is 4:1 to 6:1, and the pore size of sodium alginate sponge is 80 to 83%.

[0072] Similarly, when the ratio of sodium alginate to sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has a significant impact on the final result. When the mass concentration of the sodium alginate solution is 30-60% (preferably 40-50%), the pore size of the formed sodium alginate sponge is more suitable, which is beneficial to improving the treatment effect of high-hardness and high-viscosity backflow liquid.

[0073] Sodium alginate / quaternary ammonium salt composite material prepared by mixing quaternary ammonium salt monomers and quaternary ammonium salt polymers has a better treatment effect on high-hardness and high-viscosity backflow liquid. The preferred ratio of quaternary ammonium salt monomers to quaternary ammonium salt polymers is 1:3 to 1:5. When the mass concentration of quaternary ammonium salt solution is 4 to 7%, the adhesion state of quaternary ammonium salt on sodium alginate sponge is more conducive to the treatment of high-hardness and high-viscosity backflow liquid.

[0074] Table 4 shows examples of high-hardness, low-viscosity systems.

[0075] Table 4 Examples of High-Hardness, Low-Viscosity (Hardness 2200 mg / L, Viscosity 7 MPa·s) Systems

[0076]

[0077] Summarize:

[0078] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 41-42 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 77%.

[0079] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 43-44 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 9:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0080] The sodium alginate / quaternary ammonium salt composite material prepared in Example 45 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0081] The sodium alginate / quaternary ammonium salt composite material prepared in Example 46 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0082] The sodium alginate / quaternary ammonium salt composite material prepared in Example 47 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 5:1. The porosity of the sodium alginate sponge is 82%.

[0083] The sodium alginate / quaternary ammonium salt composite material prepared in Example 48 is a sodium alginate sponge with quaternary ammonium salt attached. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge contains sodium alginate and sodium bicarbonate. The mass ratio of sodium alginate to sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0084] Based on the above, we can conclude that:

[0085] The sodium alginate / quaternary ammonium salt composite material of the present invention has a good treatment effect on high-hardness, low-viscosity backflow liquid when the mass ratio of sodium alginate sponge to quaternary ammonium salt is 8.3:1 to 10:1, the mass ratio of sodium alginate to sodium bicarbonate is 4:1 to 6:1, and the pore size of sodium alginate sponge is 80 to 83%.

[0086] Similarly, when the ratio of sodium alginate to sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has a significant impact on the final result. When the mass concentration of the sodium alginate solution is 30-60% (preferably 40-50%), the pore size of the formed sodium alginate sponge is more suitable, which is beneficial to improving the treatment effect of high-hardness, low-viscosity backflow liquid.

[0087] Sodium alginate / quaternary ammonium salt composite material prepared by using a mixture of quaternary ammonium salt monomers and quaternary ammonium salt polymers has a better treatment effect on high-hardness, low-viscosity backflow liquid. The preferred ratio of quaternary ammonium salt monomers to quaternary ammonium salt polymers is 1:3 to 1:5. When the mass concentration of quaternary ammonium salt solution is 4 to 7%, the adhesion state of quaternary ammonium salt on sodium alginate sponge is more conducive to the treatment of high-hardness, low-viscosity backflow liquid.

[0088] Based on the above, when the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1 to 10:1, the mass ratio of the sodium alginate to the sodium bicarbonate is 5:1 to 6:1, the pore size of the sodium alginate sponge is 80 to 83%, the mass concentration of the sodium alginate solution is preferably 30 to 50% (preferably 40 to 50%), the ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is preferably 1:3 to 1:5, and the mass concentration of the quaternary ammonium salt solution is 5 to 7%, it can be simultaneously applied to the treatment of low-hardness high-viscosity, low-hardness low-viscosity, high-hardness low-viscosity, and high-hardness high-viscosity backflow solutions.

Claims

1. A sodium alginate / quaternary ammonium salt composite material, characterized in that, The sodium alginate / quaternary ammonium salt composite material consists of quaternary ammonium salt attached to sodium alginate sponge, wherein the mass ratio of sodium alginate sponge to quaternary ammonium salt is 8.3:1 to 10:1, the pore size of sodium alginate sponge is 80 to 83%, and the quaternary ammonium salt includes quaternary ammonium salt monomers and quaternary ammonium salt polymers.

2. The sodium alginate / quaternary ammonium salt composite material according to claim 1, characterized in that, The mass ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is 1:3 to 1:

5.

3. The sodium alginate / quaternary ammonium salt composite material according to claim 2, characterized in that, The quaternary ammonium salt monomer is selected from methacryloyloxyethyltrimethylammonium chloride or dimethyldiallylammonium chloride; the quaternary ammonium salt polymer is selected from polyepoxychloropropaneamine or polydimethyldiallylammonium chloride.

4. A method for preparing the sodium alginate / quaternary ammonium salt composite material according to any one of claims 1-3, characterized in that, include: (1) Sodium bicarbonate was added to sodium alginate solution and freeze-dried to obtain sodium alginate sponge. (2) Sodium alginate sponge is soaked in quaternary ammonium salt solution, and quaternary ammonium salt is dispersed to the surface and pores of the sponge by ultrasound. Then, the sodium alginate sponge with quaternary ammonium salt is dried to obtain sodium alginate / quaternary ammonium salt composite material.

5. The method according to claim 4, characterized in that, The mass ratio of sodium alginate to sodium bicarbonate is 4:1 to 6:

1.

6. The method according to claim 4, characterized in that, The sodium alginate solution has a mass concentration of 30-50%.

7. The method according to claim 6, characterized in that, The sodium alginate solution has a mass concentration of 40-50%.

8. The method according to claim 4, characterized in that, The mass concentration of the quaternary ammonium salt solution is 4-7%.

9. The method according to claim 8, characterized in that, The quaternary ammonium salt includes quaternary ammonium salt monomers and quaternary ammonium salt polymers, wherein the mass ratio of the quaternary ammonium salt monomers to the quaternary ammonium salt polymers is 1:3 to 1:

5.

10. The method of claim 9, characterized in that, The quaternary ammonium salt monomer is selected from methacryloyloxyethyltrimethylammonium chloride or dimethyldiallylammonium chloride; the quaternary ammonium salt polymer is selected from polyepoxychloropropaneamine or polydimethyldiallylammonium chloride.

11. A method for treating and reusing backflow fluid from oil and gas development, characterized in that, Use the sodium alginate / quaternary ammonium salt composite material according to any one of claims 1-3.

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