A deep purification and recycling process for tertiary oil recovery produced water

Abstract

The application discloses a tertiary oil recovery produced water deep purification and recycling treatment process, and belongs to the technical field of oil exploitation.The process comprises the following steps: step one, pretreatment and regulation of the incoming tertiary oil recovery produced water to obtain pretreated water; step two, construction of a deep adsorption and filtration system; and step three, in-situ regeneration and recycling program based on pressure difference feedback; the pretreated water is introduced into a filtration unit filled with a biomimetic amphiphilic anti-fouling modified filter material, and contact filtration operation is performed; the hydrophobic cavity of the single(methacryloyloxy)-beta-cyclodextrin ester grafted on the surface of the filter material is used to physically envelope the surfactant in the water body; this process can effectively destroy the interface film of the emulsion, induce the coalescence of micro oil droplets, and trap the micro oil droplets; and a dense hydration barrier is formed on the surface of the filter material through the hydration of the methacrylic acid sulfobetaine ester zwitterionic group.

Description

Technical Field

[0001] This invention relates to the field of oil extraction, specifically to a deep purification and recycling process for produced water from tertiary oil recovery. Background Technology

[0002] In the field of oil extraction, especially in the process of tertiary oil recovery, the widespread application of chemical flooding technology has led to the extremely complex composition of produced water. At present, the treatment of such produced water mainly relies on traditional physical sedimentation, coarsening and conventional media filtration processes.

[0003] In actual operation, existing technologies face severe challenges. Due to the high concentration of polymers such as polyacrylamide in the produced water, the water viscosity increases significantly, making the fine oil droplets extremely stable in the water. Conventional filter media are unable to effectively capture and separate them. During filtration operations, large fluctuations in the oil content and suspended solids content of the effluent are frequently observed, and the oil removal accuracy is difficult to meet the requirements of subsequent deep reinjection or high-standard discharge.

[0004] Existing filtration technologies are prone to severe irreversible fouling on filter media surfaces when treating polymer-containing wastewater. Under actual operating conditions, polymers and oil droplets often co-adsorb, forming highly viscous polymer-containing sludge that firmly coats the filter media surface. This phenomenon directly leads to a rapid increase in filtration resistance within a very short time, resulting in an abnormally shortened operating cycle. During backwashing, due to the excessively strong binding force between the filter media and contaminants, traditional washing methods often fail to completely remove the attached sludge, causing a continuous decline in the filter media's flux recovery rate. Over time, significant caking often occurs within the filter layer, even leading to deep blockage, ultimately forcing frequent shutdowns of the entire treatment unit to replace the filter media. This severely impacts production continuity and significantly increases operating and maintenance costs.

[0005] Furthermore, existing technologies lack flexible control methods when dealing with water quality fluctuations of varying emulsification levels and polymer concentrations. When the surfactant content in the influent is high, the emulsion interface film is extremely difficult to break down, leading to a large number of fine oil droplets penetrating the filter layer, making the purification effect extremely unstable. This problem of poor adaptability to complex water quality due to the single function of the filter media surface has become a bottleneck restricting the deep purification and reuse of produced water from tertiary oil recovery.

[0006] The information disclosed in the background section above is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a deep purification and recycling process for produced water from tertiary oil recovery, so as to solve the problems mentioned in the background art.

[0008] The technical solution of this invention includes the following steps: Step 1: Pre-treating and regulating the incoming tertiary oil recovery produced water to obtain pre-treated water; Step 2: Constructing a deep adsorption filtration system; Step 3: Executing an in-situ regeneration cycle based on differential pressure feedback; Introducing the pre-treated water into a filter unit filled with biomimetic amphiphilic antifouling modified filter media to perform contact filtration; The biomimetic amphiphilic antifouling modified filter media is made by grafting a ternary functional copolymer coating onto the surface of a walnut shell matrix, wherein the ternary functional copolymer is copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester.

[0009] Preferred method: The specific steps for pretreatment and regulation of the produced water entering the tertiary oil recovery process described in step one are as follows: Step A1: Introduce the produced water into a settling tank for gravity settling to remove floating oil and large suspended particles; Step A2: Use a heat exchange device to control the water temperature gradient, adjusting it to 35℃~60℃ to reduce the water viscosity and enhance Brownian motion, thereby obtaining pretreated water containing polymers and emulsified oil.

[0010] Preferably, the specific parameters for performing the contact filtration operation in step two are as follows: the filtration rate of the filtration unit is set to... The hydration effect of the zwitterionic groups of the methacrylic acid sulfobetaine ester is used to block the contact between polyacrylamide and oil droplets; the hydrophobic cavities of β-cyclodextrin grafted on the filter media surface are used to physically encapsulate the hydrophobic ends of surfactants in the water, thereby disrupting the emulsion interface film, inducing the aggregation of fine oil droplets, and retaining oil and suspended solids through the filter media layer.

[0011] Preferred: The specific steps of the in-situ regeneration cycle program based on differential pressure feedback in step three are as follows: Step B1: Real-time monitoring of differential pressure data at the inlet and outlet of the filter unit. Step B2: When When the filter media layer reaches the dirt-holding threshold, the system automatically blocks the water inlet and initiates a backwashing command; Step B3: Introduce an air-to-water ratio of... The air-water mixture is used for backwashing, and the superoleophobic properties of the filter media surface are used to remove the attached polymer-containing sludge. After backwashing, the water intake is restored and the process begins the next treatment cycle.

[0012] Preferably, the preparation method of the amphiphilic antifouling modified filter material includes the following steps:

[0013] Step C1: Perform substrate activation treatment on natural walnut shell particles to remove surface impurities and expose active sites to obtain activated walnut shells;

[0014] Step C2: Synthesize the ternary functional copolymer;

[0015] Step C3: Construct a biomimetic coating by immersing activated walnut shells in a buffer solution containing ternary functional copolymers for oxidative self-polymerization assembly and surface grafting, followed by post-treatment to obtain the biomimetic amphiphilic antifouling modified filter material.

[0016] Preferably, the specific operation of the substrate activation treatment in step C1 is as follows: select walnut shell particles with a particle size of 0.5mm~1.2mm, immerse them in a NaOH aqueous solution with a mass fraction of 4%~6%; mechanically stir and clean them at room temperature to remove surface pectin and grease; after cleaning, rinse with deionized water until neutral, and place them in a drying oven for constant temperature drying.

[0017] Preferably, the specific operation for synthesizing the ternary functional copolymer in step C2 is as follows: Step D1: Prepare the reaction monomers; Step D2: Set the monomer molar ratio to...

[0018] Step D3: Dissolve the above monomers in a mixed solvent of ethanol and water, and add 0.8%~1.2% of azobisisobutyramidine hydrochloride as an initiator; Step D4: Purge with nitrogen to remove oxygen, and carry out a constant temperature stirring reaction at 55℃~65℃ for 5~7 hours. After the reaction is completed, dialysis purification and freeze drying are performed to obtain ternary functional copolymer powder.

[0019] Preferably, the specific operation for constructing the biomimetic coating in step C3 is as follows: Step E1: Prepare a ternary functional copolymer solution with a concentration of 1.5 mg / mL to 2.5 mg / mL, using a Tris-HCl buffer solution with a pH of 8.0 to 9.0 as the solvent; Step E2: Add the activated walnut shell obtained in step C1 to the above solution, and mechanically stir under continuous air circulation for 12 to 24 hours to grow a functionalized hydrogel coating in situ on the surface of the walnut shell.

[0020] This invention provides an improved deep purification and recycling process for produced water from tertiary oil recovery, which has the following improvements and advantages compared to existing technologies:

[0021] 1. This solution utilizes the hydrophobic cavities of mono(methacryloyloxy)-β-cyclodextrin ester grafted onto the filter media surface to physically encapsulate surfactants in the water. This process effectively disrupts the interfacial film of the emulsion, inducing the aggregation and retention of fine oil droplets. Through the hydration of the zwitterionic groups of methacrylate sulfobetaine ester, a dense hydration barrier is formed on the filter media surface. This barrier effectively prevents the non-specific adsorption of polyacrylamide and oil droplets on the filter media surface. Combined with its underwater superoleophobic properties, the polyacrylamide-containing sludge can be rapidly removed during the backwashing stage using only an air-water mixture. Experimental data shows that this solution solves the problem of difficult removal of fine oil droplets under existing technologies.

[0022] 2. The dopamine methacrylamide monomer used in this solution grows a functionalized hydrogel coating in situ on the matrix surface through oxidative self-polymerization and chemical bonding with the walnut shell surface. The high proportion of dopamine component ensures the anchoring stability of the coating under long-term high flow rate scouring and extends the chemical stability period of the filter material.

[0023] 3. This scheme establishes a dynamic correlation model between the surface energy of the filter media and the contact angle of the emulsified oil droplets. By adjusting the molar ratio of each monomer in the ternary functional copolymer and optimizing the filtration rate and backwash pressure difference threshold, the process can flexibly adapt to various complex scenarios such as low energy consumption requirements in marginal oil fields or high-flow fine filtration. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0025] Example 1:

[0026] This invention provides a deep purification and recycling process for produced water from tertiary oil recovery, comprising the following steps: Step 1: Pre-treating and regulating the incoming produced water from tertiary oil recovery to obtain pre-treated water; Step 2: Constructing a deep adsorption filtration system; Step 3: Executing an in-situ regeneration cycle based on differential pressure feedback; The pre-treated water is introduced into a filter unit filled with biomimetic amphiphilic antifouling modified filter media for contact filtration; The biomimetic amphiphilic antifouling modified filter media is based on a terpolymer coating grafted onto the surface of a walnut shell matrix, wherein the terpolymer is copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester;

[0027] Before formal preparation, this invention pre-established a dynamic correlation model between the surface energy of the filter material and the contact angle of the emulsified oil droplets in order to determine the optimal molar ratio range of each monomer in the terpolymer.

[0028] Regression analysis shows that when the thickness of the hydration layer provided by the zwitterionic groups of sulfobetaine and the number of cavity trapping sites of β-cyclodextrin reach a specific equilibrium, the desorption kinetic constant of the filter media for polymer-containing oil droplets reaches its maximum value. Based on this model, this embodiment aims to provide a process scheme suitable for working conditions with light influent load but extremely high effluent water quality requirements. In this embodiment, the deep purification and circulation treatment process of tertiary oil recovery water first performs step one, pre-treating and regulating the incoming tertiary oil recovery water; the process then proceeds to step two, constructing a deep adsorption filtration system, introducing the pre-treated water into a filter unit filled with biomimetic amphiphilic antifouling modified filter media, and performing contact filtration. During the execution of step two, the process monitors the operating status of the filter unit in real time according to step three.

[0029] The specific steps for pretreatment and regulation of the produced water entering the tertiary oil recovery process in Step 1 are as follows: Step A1: Introduce the produced water into a settling tank for gravity settling to remove floating oil and large suspended particles; Step A2: Use a heat exchange device to control the water temperature gradient, adjusting it to 35°C to reduce water viscosity and enhance Brownian motion, resulting in pretreated water containing polymers and emulsified oil; At this temperature setting, the aim is to initially reduce water viscosity and improve rheology, obtaining pretreated water containing polymers and emulsified oil. Although 35°C is at the lower limit of the temperature range, combined with subsequent low filtration rate operation, it is sufficient to maintain fluid stability while minimizing heat energy consumption, making it suitable for marginal oilfield processing stations that are sensitive to energy efficiency ratios;

[0030] The specific parameters for the contact filtration operation in step two are as follows: the filtration rate of the filtration unit is set to 10 m / h; at this lower flow rate, the residence time of the fluid in the filter bed is extended, and a dense hydration barrier is formed by the hydration effect of the zwitterionic groups of sulfobetaine grafted on the surface of the filter media, effectively blocking the contact between polyacrylamide and oil droplets; at the same time, the hydrophobic cavity of β-cyclodextrin is used to fully physically encapsulate the hydrophobic end of the surfactant in the water, destroying the emulsion interface film, inducing the aggregation of fine oil droplets, and intercepting oil and suspended solids through the filter media layer. This low flow rate strategy strengthens the interaction of the micro-interface and ensures extremely high oil removal accuracy.

[0031] The specific steps of executing the in-situ regeneration cycle procedure based on differential pressure feedback in step three are as follows: Step B1: Real-time monitoring of differential pressure data at the inlet and outlet of the filter unit. Step B2: When the pressure difference data at the inlet and outlet of the filter unit is monitored... When the pressure reaches 0.05 MPa, the filter media is determined to have reached the dirt-holding threshold, the water inlet is automatically blocked, and a backwashing command is initiated; Step B3: The air-to-water ratio is... The air-water mixture is used for backwashing, and the underwater superoleophobic properties of the filter media surface are used to remove the attached polymer-containing sludge. After backwashing, the water intake is restored and the next treatment cycle begins. A low differential pressure threshold of 0.05 MPa is set to keep the filter media surface in a highly porosity active state, prevent deep irreversible clogging, and thus extend the overall service life of the filter media.

[0032] The preparation method of biomimetic amphiphilic antifouling modified filter media includes the following steps: Step C1: Activating natural walnut shell particles to remove surface impurities and expose active sites, thereby obtaining activated walnut shells; Step C2: Synthesizing ternary functional copolymers. Specifically, this includes monomer ratio, solvent dissolution and free radical polymerization reaction; Step C3: Construct a biomimetic coating by immersing activated walnut shells in a buffer solution containing ternary functional copolymers, performing oxidative self-polymerization assembly and surface grafting, and obtaining biomimetic amphiphilic antifouling modified filter material after post-treatment.

[0033] The specific operation of the substrate activation treatment in step C1 is as follows: Select walnut shell particles with a particle size of 0.5 mm and immerse them in a 4% NaOH aqueous solution; mechanically stir and wash them at room temperature to remove surface pectin and oil; after washing, rinse them with deionized water until neutral and place them in a drying oven for constant temperature drying to obtain activated walnut shells. The smaller particle size of 0.5 mm is selected to provide a larger specific surface area to meet the fine filtration requirements at low flow rates.

[0034] The specific steps for synthesizing the ternary functional copolymer in step C2 are as follows: Step D1: Prepare the reaction monomers, including sulfobetaine methacrylate (SBMA), dopamine methacrylamide (DMA), and mono(methacryloyloxy)-β-cyclodextrin ester (MAH-β-CD). In this example, sulfobetaine methacrylate (SBMA), dopamine methacrylamide (DMA), and mono(methacryloyloxy)-β-cyclodextrin ester (MAH-β-CD) were all purchased commercially as analytical grade reagents and were not synthesized in-house. Step D2: Set the monomer molar ratio to sulfobetaine methacrylate : dopamine methacrylamide : mono(methacryloyloxy)-β-cyclodextrin ester = (65-75):(10-20):(10-20); Step D3: Dissolve the above monomers in a mixed solvent of ethanol and water, and add 0.8% of azobisisobutyramidine hydrochloride as an initiator; Step D4: Purge with nitrogen to remove oxygen, and carry out a constant temperature stirring reaction at 55°C for 5 hours. After the reaction is completed, the mixture is purified by dialysis and freeze-dried to obtain ternary functional copolymer powder; In this formulation, a higher proportion of dopamine monomers, 20% of which form a strong adhesion layer through oxidative self-polymerization, enhances the anchoring stability of the coating on the walnut shell matrix and prevents it from falling off under long-term water flow erosion;

[0035] The specific steps for constructing the biomimetic coating in step C3 are as follows: Step E1: Prepare a ternary functional copolymer solution with a concentration of 1.5 mg / mL, using a Tris-HCl buffer solution with a pH of 8.0 as the solvent; Step E2: Add the activated walnut shell obtained in step C1 to the above solution and mechanically stir for 12 hours under continuous air circulation. Utilize the oxidative self-polymerization of dopamine groups and their chemical bonding with the walnut shell surface to grow a functionalized hydrogel coating in situ on the walnut shell surface; Step E3: After the reaction is complete, filter out the particles, use deionized water for ultrasonic dispersion and cleaning to remove unbound polymers, and then dry at 55°C to obtain the finished product. This embodiment, through a lower filtration rate and a lower pressure threshold, combined with a high proportion of dopamine monomers to enhance coating stability, is suitable for working conditions with extremely high requirements for effluent quality and a relatively light influent load, effectively extending the chemical stability period of the filter media.

[0036] Example 2:

[0037] A deep purification and recycling process for produced water from tertiary oil recovery includes the following steps, as described in Step 1: Pre-treating and regulating the incoming produced water to obtain pre-treated water; Step 2: Constructing a deep adsorption filtration system, introducing the pre-treated water into a filter unit filled with biomimetic amphiphilic antifouling modified filter media, and performing contact filtration; the biomimetic amphiphilic antifouling modified filter media is based on a terpolymer coating grafted onto the surface of a walnut shell matrix, the terpolymer being copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester;

[0038] This embodiment provides a deep purification and recycling process for produced water from tertiary oil recovery. This process fully includes all the above-mentioned technical features. In this embodiment, in the first step, the produced water is introduced into a settling tank for treatment, and then the water temperature is adjusted to 45°C through a heat exchange device. This temperature is at a moderate level, which can effectively reduce polymer viscosity and enhance Brownian motion, while avoiding excessive energy consumption, thus obtaining suitable pretreated water. In the second step, the pretreated water is introduced into a filter unit filled with biomimetic amphiphilic antifouling modified filter media, and the filtration rate is set to 12 m / h. This filtration rate balances the treatment efficiency and contact time, ensuring that the β-cyclodextrin on the surface of the filter media has enough time to capture surfactant molecules, disrupt the emulsion balance, and induce oil droplet aggregation. In the third step, the pressure difference ΔP is monitored in real time. When ΔP reaches 0.08 MPa, it is determined that the fouling threshold has been reached, and backwashing is initiated.

[0039] Utilizing the underwater superoleophobic properties of the air-water mixture and the filter media surface, polymer-containing sludge is rapidly detached. The biomimetic amphiphilic antifouling modified filter media used in this embodiment is prepared as follows: In step C1, walnut shell particles with a particle size of 0.8 mm are selected, and the substrate is activated using a 5% NaOH aqueous solution. In step C2, when synthesizing the ternary functional copolymer, the key raw materials such as SBMA, DMA, and MAH-β-CD used are all commercially available products. The monomer molar ratio is set as methyl methacrylate sulfobetaine ester: dopamine methacrylamide: mono(methacryloyloxy)-β-cyclodextrin ester = 70:15:15.

[0040] This formulation balances the functions of antifouling SBMA, adhesive DMA, and demulsifying CD. After dissolving the monomers, an initiator accounting for 1.0% of the total monomer mass is added, and the reaction is carried out at 60°C for 6 hours. In step C3, a ternary functional copolymer solution with a concentration of 2.0 mg / mL is prepared in a Tris-HCl buffer solution with a solvent pH of 8.5. Activated walnut shells are added to the solution, and the reaction is carried out with aerobic stirring for 18 hours. The solution is then dried at 60°C. This example represents typical optimized parameters of the process. By balancing the proportions of each monomer and operating parameters, a long operating cycle and a low backwashing frequency are achieved while ensuring a high oil removal rate, demonstrating the stable adaptability of this process in conventional tertiary oil recovery wastewater treatment scenarios.

[0041] Example 3:

[0042] A deep purification and recycling process for produced water from tertiary oil recovery includes the following steps: Step 1: Pre-treating and regulating the incoming produced water from tertiary oil recovery to obtain pre-treated water; Step 2: Constructing a deep adsorption filtration system, introducing the pre-treated water into a filter unit filled with biomimetic amphiphilic antifouling modified filter media, and performing contact filtration; The biomimetic amphiphilic antifouling modified filter media is based on a terpolymer coating grafted onto the surface of a walnut shell matrix, and the terpolymer is copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester;

[0043] This embodiment provides a deep purification and circulation treatment process for produced water from tertiary oil recovery. This process fully incorporates all the aforementioned technical features. In this embodiment, in step one, the produced water is treated in a settling tank, and then the water temperature is adjusted to 60°C. The high temperature significantly reduces the viscosity of water containing high concentrations of polyacrylamide, greatly enhancing the Brownian motion of fine particles, which is beneficial for subsequent filtration. In step two, the pretreated water is introduced into the filtration unit, and a relatively high filtration rate of 14 m / h is set to meet the large flow rate requirements. Although the flow rate is high, effective contact filtration is still maintained thanks to the reduced fluid resistance from the high temperature and the high efficiency of the filter media. In step three, the backwash trigger pressure differential is set. The pressure is 0.1 MPa, which allows the filter media to retain more pollutants and fully utilize the filter media's dirt-holding capacity. The biomimetic amphiphilic antifouling modified filter media used in this embodiment is prepared as follows:

[0044] In step C1, large walnut shell particles with a diameter of 1.2 mm are selected and immersed in a 6% NaOH aqueous solution for activation to adapt to the hydraulic load under high flow rate conditions. In step C2, when synthesizing the ternary functional copolymer, commercially available monomer raw materials are used, and the monomer molar ratio is set as methyl methacrylate sulfobetaine ester: dopamine methacrylamide: mono(methacryloyloxy)-β-cyclodextrin ester = 75:10:15. The high proportion of SBMA (75%) gives the filter media strong hydrophilicity and antifouling ability to cope with the risk of pollution accumulation under high throughput. An initiator accounting for 1.2% of the total monomer mass is added, and the reaction is carried out at 65°C for 7 hours to ensure high conversion rate. In step C3, a high concentration of 2.5 mg / mL ternary functional copolymer solution is prepared with a solvent pH of 9.0. Activated walnut shells are added and reacted for 24 hours to form a thicker polymer coating.

[0045] Finally, it is dried at 65°C. This embodiment is suitable for oilfield sites with large processing capacity, high influent temperature or waste heat utilization conditions. By strengthening the hydrophilic antifouling component SBMA of the filter media, it still maintains good regeneration performance under high filtration rate and high dirt holding capacity.

[0046] Example 4:

[0047] A deep purification and recycling process for produced water from tertiary oil recovery includes the following steps: Step 1: Pre-treating and regulating the incoming produced water from tertiary oil recovery to obtain pre-treated water; Step 2: Constructing a deep adsorption filtration system, introducing the pre-treated water into a filter unit filled with biomimetic amphiphilic antifouling modified filter media, and performing contact filtration; The biomimetic amphiphilic antifouling modified filter media is based on a terpolymer coating grafted onto the surface of a walnut shell matrix, and the terpolymer is copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester;

[0048] This embodiment provides a deep purification and recycling process for produced water from tertiary oil recovery, which fully encompasses all the aforementioned technical features. In this embodiment, in step one, the water temperature is adjusted to 40°C. In step two, pretreated water is introduced into a filtration unit, and the filtration rate is set to 11 m / h, a parameter setting biased towards refined treatment. In step three, when the pressure difference is monitored... Backwashing is initiated when the pressure reaches 0.06 MPa. Early backwashing helps maintain the filter media surface in a highly active state, preventing deep clogging. The biomimetic amphiphilic antifouling modified filter media used in this embodiment is prepared as follows:

[0049] In step C1, walnut shell particles with a diameter of 0.6 mm were selected and activated using a 4.5% (w / w) NaOH aqueous solution. In step C2, when synthesizing the ternary functional copolymer, the monomer molar ratio was set as methacrylic acid sulfobetaine ester: dopamine methacrylamide: mono(methacryloyloxy)-β-cyclodextrin ester = 68:12:20. In this ratio, the proportion of β-cyclodextrin was appropriately increased by 20%, which enhanced the filter media's ability to recognize surfactants and demulsify, especially for severely emulsified oil droplets with extremely small particle sizes. In a small produced water system, an initiator accounting for 0.9% of the total monomer mass was added, and the reaction was carried out at 58°C for 5.5 hours. In step C3, a ternary functional copolymer solution with a concentration of 1.8 mg / mL and a solvent pH of 8.2 was prepared, and the reaction was carried out for 16 hours, followed by drying at 58°C. This embodiment, by increasing the content of demulsifying components in the functional monomer and combining it with a low-pressure differential backwashing strategy, is particularly suitable for ASP-driven produced water treatment with high surfactant concentration and extremely stable emulsion, demonstrating the advantages of formulation control for specific water quality characteristics.

[0050] Example 5:

[0051] A deep purification and recycling process for produced water from tertiary oil recovery includes the following steps: Step 1: Pre-treating and regulating the incoming produced water from tertiary oil recovery to obtain pre-treated water; Step 2: Constructing a deep adsorption filtration system, introducing the pre-treated water into a filter unit filled with biomimetic amphiphilic antifouling modified filter media, and performing contact filtration; The biomimetic amphiphilic antifouling modified filter media is based on a terpolymer coating grafted onto the surface of a walnut shell matrix, and the terpolymer is copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester;

[0052] This embodiment provides a deep purification and recycling process for produced water from tertiary oil recovery. This process fully incorporates all the aforementioned technical features. In this embodiment, the deep purification and recycling process for produced water involves adjusting the water temperature to 55°C in step one; introducing pretreated water into the filtration unit at a filtration rate of 13 m / h in step two; and initiating backwashing when the pressure difference ΔP reaches 0.09 MPa in step three. This combination of process parameters aims to achieve a balance between high treatment efficiency and stable effluent quality. The biomimetic amphiphilic antifouling modified filter media used in this embodiment is prepared as follows:

[0053] In step C1, walnut shell particles with a diameter of 1.0 mm are selected and activated using a 5.5% (w / w) NaOH aqueous solution. In step C2, when synthesizing the ternary functional copolymer, the monomer molar ratio is set as methyl methacrylate sulfobetaine ester: dopamine methacrylamide: mono(methacryloyloxy)-β-cyclodextrin ester = 72:18:10. In this ratio, the DMA content of 18% is relatively high, aiming to enhance the adhesion between the coating and the substrate. At the same time, SBMA of 72% maintains high stain resistance, while the CD content is appropriately reduced to suit the needs of the substrate. For water with moderate emulsification but high risk of polymer adhesion, an initiator of 1.1% of the total monomer mass is added, and the reaction is carried out at 62°C for 6.5 hours. In step C3, a terfunctional copolymer solution with a concentration of 2.2 mg / mL and a solvent pH of 8.8 is prepared, and the reaction is carried out for 20 hours, followed by drying at 62°C. This embodiment demonstrates a solution for the process in the case of high polymer concentration, which can easily lead to wear and peeling of the filter media coating. By strengthening the coating anchoring force and anti-adhesion force, the mechanical stability of long-term operation is ensured.

[0054] Comparative Example 1:

[0055] The filter media was natural walnut shells without any chemical modification, with a particle size of 0.8 mm. The processing parameters were the same as in Example 2, namely, water temperature 45℃, filtration rate 12 m / h, and backwash trigger pressure difference 0.08 MPa. Due to the lack of surface functional coating, the surface of natural walnut shells is oleophilic and easily adsorbs oil-containing sludge. This comparative example aims to verify the necessity of biomimetic coatings.

[0056] Comparative Example 2:

[0057] Modified walnut shell filter media was used, but mono(methacryloyloxy)-β-cyclodextrin ester was not added during copolymer synthesis. The monomer ratio was SBMA:DMA=85:15. The remaining preparation and process parameters were the same as in Example 2. This comparative example aims to verify the role of β-cyclodextrin in demulsification and polymerization.

[0058] Comparative Example 3:

[0059] Modified walnut shell filter media was used, but sulfobetaine methacrylate was not added during copolymer synthesis. The monomer ratio was DMA:MAH-β-CD=50:50. The remaining preparation and process parameters were the same as in Example 2. This comparative example aims to verify the role of zwitterionic sulfobetaine in antifouling and backwashing regeneration.

[0060] Verification test

[0061] The processing technology and filter media prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to continuous operation tests, and the test results are shown below;

[0062] Testing standards:

[0063] 1. Determination of oil content in the treated water: The oil content was determined using infrared spectrophotometry, referring to standard SY / T5329-2012 "Water Quality Indicators and Analytical Methods for Injection Water in Clastic Rock Reservoirs". An OIL-460 infrared oil analyzer was used, and three measurements were taken, with the average value taken.

[0064] 2. Determination of suspended solids in effluent: Gravimetric method was used, with filtration through a 0.45μm filter membrane and drying at 105℃ to constant weight.

[0065] 3. Flux recovery rate determination: Record the pure water flux before and after backwashing. The calculation formula is: ,in This is the flux after backwashing. This represents the initial flux.

[0066] 4. Operating cycle: Record the time required from the start of filtration until the differential pressure reaches the set threshold, or the effluent water quality exceeds the standard.

[0067] Under the same influent water quality conditions, continuous operation tests were conducted with oil content of 350 mg / L, polymer content of 400 mg / L, and suspended solids content of 120 mg / L. The experimental apparatus used an organic glass column with an inner diameter of 100 mm and a filling height of 800 mm. The test was conducted according to the parameters set in each embodiment. The effluent water quality was sampled and tested every 2 hours. When the pressure difference reached the set value, air-water backwashing was performed. The flux recovery after backwashing was recorded, and the average operating cycle was calculated.

[0068] Table 1

[0069] Group Oil content in effluent (mg / L) Effluent suspended solids (mg / L) Flux recovery rate (%) Operation cycle (h) Example 1 3.8 1.8 99.2 25.5 Example 2 4.5 2.0 98.8 24.0 Example 3 5.2 2.5 98.5 22.5 Example 4 4.1 1.9 99.0 23.5 Example 5 4.8 2.2 98.6 24.5 Comparative Example 1 28.5 15.6 45.0 6.5 Comparative Example 2 12.4 5.8 92.0 18.0 Comparative Example 3 8.5 8.2 65.0 10.5

[0070] As shown in Table 1, the deep purification and recycling process for produced water from tertiary oil recovery proposed in this invention achieves significantly better treatment results than existing technologies, as shown in Comparative Example 1, through temperature-controlled pretreatment in step one, adsorption filtration of specific biomimetic amphiphilic antifouling modified filter media in step two, and differential pressure feedback regeneration in step three.

[0071] Synergistic effect analysis of functional monomers: Comparing Example 2 and Comparative Example 2, it can be seen that when β-cyclodextrin MAH-β-CD is missing in the copolymer, the oil content in the effluent increases sharply from 4.5 mg / L to 12.4 mg / L. This confirms that the hydrophobic cavity of β-cyclodextrin has a specific host-guest recognition and encapsulation effect on surfactants in water. By destroying the emulsion interface film, it induces the aggregation of fine oil droplets, which are then effectively intercepted by the filter media. The absence of this group leads to the penetration of fine emulsion oil through the filter layer, resulting in a significant decrease in oil removal efficiency.

[0072] Verification of the antifouling mechanism: Comparing Example 2 and Comparative Example 3, when sulfobetaine was missing, although the oil content in the effluent was acceptable at 8.5 mg / L, the flux recovery rate was only 65.0%, and the operating cycle was shortened to 10.5 hours; this indicates that the hydration barrier constructed by zwitterionic groups is crucial for resisting the non-specific adsorption of polymers and oil sludge; in Comparative Example 3, pollutants gradually accumulated on the surface of the filter media and agglomerated, resulting in backwashing being unable to effectively remove pollutants and severely deteriorating regeneration performance;

[0073] Robustness of process parameters: Examples 1-5 showed stable performance under different temperatures, flow rates and formulations, with effluent oil content <6mg / L and flux recovery rate >98%, further verifying the technical reliability of the process under different operating conditions; in particular, Example 4, by increasing the CD content, performed excellently in treating highly emulsified water, indicating that specific water quality problems can be addressed by adjusting the monomer ratio.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A deep purification and recycling process for produced water from tertiary oil recovery, characterized in that, Includes the following steps: Step 1: Pre-treat and regulate the incoming produced water from the tertiary oil recovery process to obtain pre-treated water; Step 2: Construct a deep adsorption filtration system; Step 3: Execute an in-situ regeneration cycle based on differential pressure feedback; The pretreated water is introduced into a filter unit filled with biomimetic amphiphilic antifouling modified filter media to perform contact filtration; The biomimetic amphiphilic antifouling modified filter media is made by grafting a ternary functional copolymer coating onto the surface of a walnut shell matrix, and the ternary functional copolymer is copolymerized from methyl methacrylate sulfobetaine ester, dopamine methacrylamide, and mono(methacryloyloxy)-β-cyclodextrin ester; The preparation method of the biomimetic amphiphilic antifouling modified filter material includes the following steps: Step C1: Perform substrate activation treatment on natural walnut shell particles to remove surface impurities and expose active sites to obtain activated walnut shells; Step C2: Synthesize the ternary functional copolymer; Step C3: Construct a biomimetic coating by immersing activated walnut shells in a buffer solution containing ternary functional copolymers for oxidative self-polymerization assembly and surface grafting, followed by post-treatment to obtain the biomimetic amphiphilic antifouling modified filter material. The specific operation of the substrate activation treatment in step C1 is as follows: Select walnut shell particles with a particle size of 0.5mm~1.2mm, immerse them in a NaOH aqueous solution with a mass fraction of 4%~6%; mechanically stir and clean them at room temperature to remove surface pectin and grease; after cleaning, rinse with deionized water until neutral, and place them in a drying oven for constant temperature drying; The specific operations for synthesizing the ternary functional copolymer in step C2 are as follows: Step D1: Prepare the reaction monomers; Step D2: Set the monomer molar ratio to... Step D3: Dissolve the above monomers in a mixed solvent of ethanol and water, and add 0.8%~1.2% of azobisisobutyramidine hydrochloride as an initiator; Step D4: Purge with nitrogen to remove oxygen, and carry out a constant temperature stirring reaction at 55℃~65℃ for 5~7 hours. After the reaction is completed, dialysis purification and freeze drying are performed to obtain ternary functional copolymer powder; The specific operation for constructing the biomimetic coating in step C3 is as follows: Step E1: Prepare a ternary functional copolymer solution with a concentration of 1.5 mg / mL to 2.5 mg / mL, using a Tris-HCl buffer solution with a pH of 8.0 to 9.0 as the solvent; Step E2: Add the activated walnut shell obtained in step C1 to the above solution, and mechanically stir under continuous air circulation for 12 to 24 hours to grow a functionalized hydrogel coating in situ on the surface of the walnut shell.

2. The deep purification and recycling process for produced water from tertiary oil recovery according to claim 1, characterized in that: The specific steps for pretreatment and regulation of the produced water entering the tertiary oil recovery process described in Step 1 are as follows: Step A1: Introduce the produced water into a settling tank for gravity settling to remove floating oil and large suspended particles; Step A2: Use a heat exchange device to control the gradient temperature of the water to adjust it to 35℃~60℃ to reduce the viscosity of the water and enhance Brownian motion; thus obtaining pretreated water containing polymers and emulsified oil.

3. The deep purification and recycling process for produced water from tertiary oil recovery according to claim 1, characterized in that: The specific parameters for performing the contact filtration operation in step two are as follows: The filtration rate of the filtration unit is set to... The hydration effect of the zwitterionic groups of the methacrylic acid sulfobetaine ester is used to block the contact between polyacrylamide and oil droplets; the hydrophobic cavity of β-cyclodextrin in the mono(methacryloyloxy)-β-cyclodextrin ester grafted on the filter media surface is used to physically encapsulate the hydrophobic ends of surfactants in the water, thereby destroying the emulsion interface film, inducing the aggregation of fine oil droplets, and retaining oil and suspended solids through the filter media layer.

4. The deep purification and recycling process for produced water from tertiary oil recovery according to claim 1, characterized in that: The specific steps of executing the in-situ regeneration cycle program based on differential pressure feedback in step three are as follows: Step B1: Real-time monitoring of differential pressure data at the inlet and outlet of the filter unit. Step B2: When When the filter media layer reaches the dirt-holding threshold, the system automatically blocks the water inlet and initiates a backwashing command; Step B3: Introduce an air-to-water ratio of... The air-water mixture is used for backwashing, and the superoleophobic properties of the filter media surface are used to remove the attached polymer-containing sludge. After backwashing, the water intake is restored and the process begins the next treatment cycle.