Sodium alginate / quaternary ammonium salt composite material and preparation and application thereof

Abstract

The invention discloses a sodium alginate / quaternary ammonium salt composite material, the sodium alginate / quaternary ammonium salt composite material is characterized in that a quaternary ammonium salt is attached to a sodium alginate sponge, the mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3: 1-10: 1, the pore diameter of the sodium alginate sponge is 80-83%, and the quaternary ammonium salt comprises a quaternary ammonium salt monomer and a quaternary ammonium salt polymer. The invention also discloses a preparation method and application thereof. Aiming at the content and property of the metal ions in the oil-gas field development process, the influence of the metal ions on a recycling treatment system is solved in a gradient treatment mode, the recycling target of the metal ions is synchronously achieved, and green and sustainable development of the oil-gas field is supported.

Description

Technical Field

[0001] The present invention relates to a sodium alginate / quaternary ammonium salt composite material and its preparation and application. Background Art

[0002] In some oil and gas development processes, large-scale hydraulic fracturing technology is adopted, resulting in a large consumption of fresh water resources and a large amount of fracturing flowback fluid being generated. Due to the high salinity and high heavy metal content of the flowback fluid, on the one hand, the flowback fluid needs to be recycled to supplement the consumption of fresh water resources, and the influence of metal ions must be removed, such as hardness ions like calcium and magnesium, which increases the treatment cost; on the other hand, the metal ions in the flowback fluid from the formation can be used as catalysts for certain reactions, such as transition metals iron and manganese, and can also become important raw materials, such as rare metal lithium. Therefore, it is necessary to coordinate the reuse of water resources in the flowback fluid and the resource utilization of metal substances, and explore the best paths and practices for resource recovery and treatment cost control.

[0003] The composition of the flowback fluid is complex, with interactions among particulate matter, organic matter, metal ions, etc. It is necessary to carry out cascade treatment based on the pollution characteristics and effectively recover material resources. However, the existing treatment systems do not fully consider the property differences of substances, and there is still room for improvement in the removal of pollutants and the recovery of substances. Hardness ions have a great impact on the quality of the recycled water of the flowback fluid, and the hardness removal technology has also become the most commonly used treatment unit. Patent CN111423011B discloses a method for treating and recycling shale gas fracturing flowback fluid, targeting shale gas flowback fluid, with the pH value adjusted to 7 - 8, being in the slightly alkaline range, and using ethylenediaminetetraacetic acid, sodium pyrophosphate, and glycolic acid as metal ion complexing agents to treat hardness ions, but under certain conditions, the complexes will dissociate into hardness ions again; Patent CN113526730A uses inorganic salt sodium sulfate to remove hardness from fracturing flowback fluid. Since calcium sulfate is slightly soluble, the removal effect of calcium ions is not good, and there is no precipitation effect on magnesium ions. In addition, the existing technologies and processes for treating metal ions are relatively single, either treating them as waste with the treatment as the goal, or only focusing on the treatment and recovery of rare metals such as lithium. For example, Patent CN 112723395 A discloses a process for the resource utilization of lithium in shale gas fracturing flowback fluid, placing lithium recovery in the first step, not only having a relatively high treatment cost, but also the ion sieve-type adsorbent used being affected by other metal ions, and at the same time ignoring the resource utilization of other substances that can be used as catalysts. Summary of the Invention

[0004] The present invention is made to further improve the reuse treatment efficiency of oil and gas development flowback fluid and better realize the comprehensive utilization of recovering metal ions from oil and gas development flowback fluid.

[0005] As an aspect of the present invention, it relates to a sodium alginate / quaternary ammonium salt composite material, wherein the sodium alginate / quaternary ammonium salt composite material is a quaternary ammonium salt attached to a sodium alginate sponge. Among them, 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 includes a quaternary ammonium salt monomer and a quaternary ammonium salt polymer.

[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. The quaternary ammonium salt monomer is selected from methacryloyloxyethyl trimethyl ammonium chloride or dimethyldiallyl ammonium chloride; the quaternary ammonium salt polymer is selected from polyepichlorohydrin amine or poly dimethyldiallyl ammonium chloride.

[0007] As another aspect of the present invention, it relates to a method for preparing the above-mentioned sodium alginate / quaternary ammonium salt composite material, including:

[0008] (1) Adding sodium bicarbonate to the sodium alginate solution and freeze-drying to obtain a sodium alginate sponge;

[0009] (2) Soaking the sodium alginate sponge in the quaternary ammonium salt solution, dispersing the quaternary ammonium salt on the surface and pores of the sponge by ultrasonic waves, and then drying the sodium alginate sponge with the quaternary ammonium salt to obtain the sodium alginate / quaternary ammonium salt composite material.

[0010] In a specific embodiment, the mass ratio of the sodium alginate to the 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 yet another aspect of the present invention, it relates to a method for reusing and treating the produced fluid in oil and gas development, using the above-mentioned sodium alginate / quaternary ammonium salt composite material.

[0014] There are many types of metal ions in the produced fluid. The existing processes do not fully consider the added value of metal ions. In addition to carrying out research on the recovery of some rare metal ions, it is also necessary to take into account resource utilization during the metal ion treatment process to jointly achieve the whole-process control of waste harmlessness, reduction, and resource utilization. Therefore, in view of the content and properties of metal ions during the oil and gas field development process, the present invention solves the impact of metal ions on the reuse treatment system in a step-by-step treatment manner, synchronously realizing the resource utilization goal of metal ions and supporting the green and sustainable development of oil and gas fields.

[0015] The method for treating flowback fluid in the present invention solves the problems of long process flow, large occupied area, high dosage of chemicals, etc. in the traditional treatment process, and realizes the reuse and reinjection treatment of flowback fluid quickly through comprehensive effects such as gel breaking, separation, and hardness removal. Specific Embodiments

[0016] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solution of the present invention will be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0017] There are many types of flowback fluids in oil and gas development, including drilling waste fluids, fracturing flowback fluids, workover waste fluids, etc. The pollutant concentrations also vary greatly, with viscosities of about 2 - 30 mp·s and hardnesses of about 300 - 3000 mg / L. To treat the waste fluids more efficiently, they are divided into 4 types of systems: low hardness and high viscosity, low hardness and low viscosity, high hardness and low viscosity, and high hardness and high viscosity. Among them, low viscosity is 2 - 10 mp·s, high viscosity is 10 - 30 mp·s, low hardness is 300 - 1000 mg / L, and high hardness is 1000 - 3000 mg / L.

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

[0019] (1) Sodium bicarbonate is added to the sodium alginate solution and freeze-dried to obtain sodium alginate sponge;

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

[0021] In the embodiments of the present invention, the basic steps for verifying the treatment effect of the sodium alginate / quaternary ammonium salt composite material on flowback fluid are as follows:

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

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

[0024] For produced fluids with different hardness and viscosity, different sodium alginate / quaternary ammonium salt composites can be selected. The following uses sodium alginate / quaternary ammonium salt composites prepared under different conditions to treat the produced fluids, calculates the hardness reduction rate and viscosity reduction rate, and examines the effects of factors such as the mass concentration of sodium alginate, the mass concentration of sodium bicarbonate, the type and mass concentration of quaternary ammonium salt, and the volume ratio of sodium alginate sponge to quaternary ammonium salt solution used to prepare the sodium alginate sponge on the final results. The quaternary ammonium salts used in the examples of the present invention are: quaternary ammonium salt monomers: methacryloyloxyethyltrimethylammonium chloride (denoted as A), dimethyldiallylammonium chloride (denoted as B); quaternary ammonium salt polymers: polyepichlorohydrin amine (denoted as C), polydimethyldiallylammonium chloride (denoted as D).

[0025] The treatment results of produced fluids with low hardness and high viscosity are shown in Table 1.

[0026] Table 1 Examples of the system with low hardness and high viscosity (hardness 520 mg / L, viscosity 20 mPa·s)

[0027]

[0028]

[0029] Summary:

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

[0031] The sodium alginate / quaternary ammonium salt composites prepared in Examples 3-4 are sodium alginate sponges attached with quaternary ammonium salts. The quaternary ammonium salts are C and D. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 5:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate. The mass ratio of the sodium alginate to the sodium bicarbonate is 2:1. The porosity of the sodium alginate sponge is 70%.

[0032] The sodium alginate / quaternary ammonium salt composites prepared in Examples 5-6 are sodium alginate sponges attached with quaternary ammonium salts. The quaternary ammonium salts are A and B. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 5:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate. The mass ratio of the sodium alginate to the sodium bicarbonate is 4:1. 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 attached with quaternary ammonium salts. The quaternary ammonium salts are C and D. The mass ratio of the sodium alginate sponge to the quaternary ammonium salts is 8.3:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 77%.

[0034] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 9-12 is a sodium alginate sponge attached with 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 salts is 8.3:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The quaternary ammonium salt is AC. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The quaternary ammonium salt is AD. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the sodium bicarbonate is 4:1. 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 attached with quaternary ammonium salts. The quaternary ammonium salt is BC. The mass ratio of the sodium alginate sponge to the quaternary ammonium salts is 8.3:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the sodium bicarbonate is 4:1. 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 attached with quaternary ammonium salts. The quaternary ammonium salts are BC and BD. The mass ratio of the sodium alginate sponge to the quaternary ammonium salts is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. The quaternary ammonium salts are BC and BD. 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, and the mass ratio of the sodium alginate to the sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0040] Based on the above, it can be known that:

[0041] For the sodium alginate / quaternary ammonium salt composite material of the present invention, 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%, the treatment effect on the low-hardness and high-viscosity flowback fluid is better.

[0042] Similarly, when the addition ratio of sodium alginate and sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has an obvious influence on the final result. When the mass concentration of the sodium alginate solution is 20% to 50% (preferably 40% to 50%), the pore size of the formed sodium alginate sponge is more appropriate, which is beneficial to improving the treatment effect on the low-hardness and high-viscosity flowback fluid.

[0043] The sodium alginate / quaternary ammonium salt composite material prepared by mixing the quaternary ammonium salt monomer and the quaternary ammonium salt polymer has a better treatment effect on the low-hardness and high-viscosity flowback fluid. Among them, the ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is preferably 1:3 to 1:5. When the mass concentration of the quaternary ammonium salt solution is 5% to 7%, the attachment state of the quaternary ammonium salt on the sodium alginate sponge is more conducive to the treatment of the low-hardness and high-viscosity flowback fluid.

[0044] Under the optimal treatment conditions for the determined low-hardness and high-viscosity system, good treatment effects for the low-hardness and low-viscosity system, high-hardness and high-viscosity system, and high-hardness and low-viscosity system cannot be achieved. Therefore, it is necessary to further optimize the treatment conditions. Table 2 shows the examples for the low-hardness and low-viscosity system.

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

[0046]

[0047] Summary:

[0048] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 19 - 22 is a sodium alginate sponge attached with a quaternary ammonium salt. 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, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 9:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the sodium bicarbonate is 4:1. The porosity of the sodium alginate sponge is 80%.

[0052] The sodium alginate / quaternary ammonium salt composite materials prepared in Examples 29 - 30 are sodium alginate sponges attached with quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with quaternary ammonium salts. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0055] Based on the above, it can be known that:

[0056] For the sodium alginate / quaternary ammonium salt composite material of the present invention, 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 4:1 to 6:1, and the pore size of the sodium alginate sponge is 80 - 83%, the treatment effect on the low-hardness and low-viscosity flowback fluid is better.

[0057] Similarly, when the addition ratio of sodium alginate to sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has an obvious influence 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 on the low-hardness and low-viscosity flowback fluid.

[0058] The sodium alginate / quaternary ammonium salt composite material prepared by mixing the quaternary ammonium salt monomer and the quaternary ammonium salt polymer has a better treatment effect on the low-hardness and low-viscosity flowback fluid. Among them, the ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is preferably 1:3 to 1:5. When the mass concentration of the quaternary ammonium salt solution is 4 - 7%, the attachment state of the quaternary ammonium salt on the sodium alginate sponge is more conducive to the treatment of the low-hardness and low-viscosity flowback fluid.

[0059] Similarly, the process conditions of the high-hardness and high-viscosity system and the high-hardness and low-viscosity system are optimized. Table 3 shows the examples of the high-hardness and high-viscosity system.

[0060] Table 3 Examples of the high-hardness and high-viscosity (hardness 2500mg / L, viscosity 32mp·s) system

[0061]

[0062]

[0063] Summary:

[0064] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 33 - 34 is a sodium alginate sponge attached with a quaternary ammonium salt. 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, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. 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 the sodium alginate to the 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 attached with a quaternary ammonium salt. 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 the sodium alginate to the 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 attached with a quaternary ammonium salt. 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, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. 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, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. 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, and the mass ratio of the sodium alginate to the sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0070] Based on the above, it can be known that:

[0071] For the sodium alginate / quaternary ammonium salt composite material of the present invention, 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 4:1 to 6:1, and the pore size of the sodium alginate sponge is 80 to 83%, the treatment effect on the high-hard and high-viscosity flowback fluid is better.

[0072] Similarly, when the addition ratio of sodium alginate and sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has an obvious influence on the final result. When the mass concentration of the sodium alginate solution is 30 to 60% (preferably 40 to 50%), the pore size of the formed sodium alginate sponge is more appropriate, which is beneficial to improving the treatment effect of the high-hard and high-viscosity flowback fluid.

[0073] The sodium alginate / quaternary ammonium salt composite material prepared by mixing a quaternary ammonium salt monomer and a quaternary ammonium salt polymer has a better treatment effect on high-hardness and high-viscosity flowback fluid. Among them, the ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is preferably 1:3 to 1:5. When the mass concentration of the quaternary ammonium salt solution is 4-7%, the attachment state of the quaternary ammonium salt on the sodium alginate sponge is more conducive to the treatment of high-hardness and high-viscosity flowback fluid.

[0074] Table 4 shows the examples of the high-hardness and low-viscosity system.

[0075] Examples of the high-hardness and low-viscosity (hardness 2200 mg / L, viscosity 7 mp·s) system in Table 4

[0076]

[0077] Summary:

[0078] The sodium alginate / quaternary ammonium salt composite material prepared in Examples 41-42 is a sodium alginate sponge attached with a quaternary ammonium salt. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 9:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 12.5:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 8.3:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the 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 attached with a quaternary ammonium salt. The mass ratio of the sodium alginate sponge to the quaternary ammonium salt is 10:1. The sodium alginate sponge therein contains sodium alginate and sodium bicarbonate, and the mass ratio of the sodium alginate to the sodium bicarbonate is 6:1. The porosity of the sodium alginate sponge is 83%.

[0084] Based on the above, it can be known that:

[0085] For the sodium alginate / quaternary ammonium salt composite material of the present invention, 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 4:1 to 6:1, and the pore size of the sodium alginate sponge is 80 - 83%, the treatment effect on high-hardness and low-viscosity flowback fluid is better.

[0086] Similarly, when the addition ratio of sodium alginate and sodium bicarbonate is 4:1, the concentration of the sodium alginate solution has an obvious influence 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 on high-hardness and low-viscosity flowback fluid.

[0087] The sodium alginate / quaternary ammonium salt composite material prepared by mixing a quaternary ammonium salt monomer and a quaternary ammonium salt polymer has a better treatment effect on high-hardness and low-viscosity flowback fluid. Among them, the ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is preferably 1:3 to 1:5. When the mass concentration of the quaternary ammonium salt solution is 4 - 7%, the attachment state of the quaternary ammonium salt on the sodium alginate sponge is more conducive to the treatment of high-hardness and low-viscosity flowback fluid.

[0088] Based on the above, it can be known that 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 - 83%, the mass concentration of the sodium alginate solution is preferably 30 - 50% (preferably 40 - 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 - 7%, it can be simultaneously applicable to the treatment of low-hardness and high-viscosity, low-hardness and low-viscosity, high-hardness and low-viscosity, and high-hardness and high-viscosity flowback fluids.

Claims

1. A sodium alginate / quaternary ammonium salt composite material, characterized in that, The sodium alginate / quaternary ammonium salt composite material is a quaternary ammonium salt 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 includes a quaternary ammonium salt monomer and a quaternary ammonium salt polymer.

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 methacryloyloxyethyl trimethyl ammonium chloride or dimethyldiallyl ammonium chloride; the quaternary ammonium salt polymer is selected from polyepichlorohydrin amine or poly dimethyldiallyl ammonium 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, Comprising: (1) Sodium bicarbonate is added to the sodium alginate solution and freeze-dried to obtain a sodium alginate sponge; (2) The sodium alginate sponge is immersed in a quaternary ammonium salt solution, and the quaternary ammonium salt is dispersed on the surface and pores of the sponge by ultrasound, and then the sodium alginate sponge with the quaternary ammonium salt is dried to obtain a sodium alginate / quaternary ammonium salt composite material.

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

1.

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

7. The method according to claim 6, characterized in that, The mass concentration of the sodium alginate solution is 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 a quaternary ammonium salt monomer and a quaternary ammonium salt polymer. The mass ratio of the quaternary ammonium salt monomer to the quaternary ammonium salt polymer is 1:3 to 1:

5.

10. The method according to claim 9, characterized in that, The quaternary ammonium salt monomer is selected from methacryloyloxyethyl trimethyl ammonium chloride or dimethyldiallyl ammonium chloride; the quaternary ammonium salt polymer is selected from polyepichlorohydrin amine or poly dimethyldiallyl ammonium chloride.

11. A method for recycling and treating the produced fluid in 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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