High-temperature-resistant completion fluid viscosity-shear improving agent based on covalent bond-secondary bond double bond cooperation and preparation method of high-temperature-resistant completion fluid viscosity-shear improving agent

Abstract

The invention discloses a high-temperature-resistant well completion fluid viscosity-shear improving agent based on covalent bond-secondary bond double bond cooperation and a preparation method of the high-temperature-resistant well completion fluid viscosity-shear improving agent, and belongs to the technical field of oil and gas resource exploration. On one hand, the viscosity and shear improving agent can form a new methylene bridge covalent bond crosslinking point, and on the other hand, the viscosity and shear improving agent can form a supramolecular association system through intermolecular hydrogen-bond interaction, and a structural system of an effective suspension stable high-density solid phase weighting agent can be formed without ultra-high molecular weight. The improvement of the crosslinking degree can effectively counteract the thermal degradation effect of high temperature on the polymer, and the high-pressure environment of the deep well can obviously enhance the stability of hydrogen bonds, so that the polymer body and a supramolecular association system formed by the polymer body are not easily damaged by the high-temperature effect, and the viscosity and cutting improving performance of the polymer in the completion fluid is further ensured.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas resource exploration technology, specifically relating to a high-temperature resistant well completion fluid viscosity-reducing agent based on the interaction of covalent bonds and secondary bonds, and its preparation method. Background Technology

[0002] As oil and gas resource development in the Sichuan-Chongqing region shifts towards deeper formations, the proportion of deep and ultra-deep wells is increasing year by year. Completion fluid systems face the severe challenge of prolonged high-temperature environments. Polymer viscosity-enhancing agents in these systems are highly susceptible to thermal degradation, leading to a significant decrease in their viscosity-enhancing performance and causing system instability. Among existing heat-resistant polymer treatment agents for drilling / completion fluids, sulfonated phenolic resins, due to their large number of active functional groups, can undergo a re-crosslinking reaction under high temperatures to form strong methylene bridges. By increasing the degree of crosslinking, the negative impact of high-temperature degradation can be effectively offset, thus exhibiting excellent resistance to high-temperature degradation. However, sulfonated phenolic resins have a relatively small molecular weight and weak self-adhesive-enhancing performance, making them insufficient to meet the requirements for high-density solid phase weighting agents in completion fluid suspensions when used alone. Based on this situation, the development of heat-resistant and salt-tolerant viscosity-enhancing agents that meet the needs of deep well completion operations is imperative.

[0003] Introducing polymers that can participate in the high-temperature crosslinking reaction of sulfonated phenolic resins into the completion fluid system, allowing them to co-form a three-dimensional polymer with a certain degree of crosslinking, can effectively improve the viscosity-enhancing and shearing properties of the polymer in high-temperature environments and maintain the performance of the completion fluid. However, because the free water content in deep-well high-density completion fluids is low, the degree of crosslinking and molecular weight of the three-dimensional polymer used for viscosity enhancement and shearing should not be too high to avoid affecting its solubility.

[0004] In summary, sulfonated phenolic resin should be moderately degraded to reduce its average molecular weight and expose more active sites to enhance its reactivity with polymers. Meanwhile, the polymers that crosslink with sulfonated phenolic resins should have the following characteristics: (1) The polymer should contain a phenolic ring structure with active hydrogen to react with the hydroxymethyl group in the sulfonated phenolic resin to form a methylene bridge; (2) The polymer should contain a large number of functional groups that can form secondary bonds. The resulting polymer can not only enhance the degree of crosslinking through the covalent bonding of the methylene bridge, but also form a supramolecular dynamic association system through the secondary bonding between molecules. This ensures the polymer's viscosity-enhancing properties without requiring excessively large molecular weights, and also provides additional structural strength for use as a suspending solid-phase weighting agent; (3) The secondary bonds formed should be mainly hydrogen bonds, which are the strongest secondary bonds. Furthermore, the high-pressure environment of deep wells can significantly enhance the stability of hydrogen bonds, ensuring the structural stability of the dynamic association system. Based on the above analysis, this invention utilizes readily available and inexpensive polyhydroxy natural macromolecules and two common olefin monomers in a copolymerization reaction to first obtain a ternary copolymer with a suitable molecular weight. Then, this copolymer is grafted onto a degraded and activated sulfonated phenolic resin to obtain a three-dimensional polymer with covalent and secondary double bonds. When exposed to high temperatures downhole, this polymer can form new methylene bridge covalent crosslinking points, and the densely distributed hydroxyl functional groups in its molecular structure enable the polymer to form a supramolecular association system in water. Based on the double bond interaction of covalent and secondary bonds, the polymer can maintain its structural stability in long-term high-temperature environments and provide the viscosity-reducing and shearing properties required for deep well completion operations. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-temperature resistant viscosity-reducing agent and method for completion fluids based on covalent-secondary bond double bond interaction. This viscosity-reducing agent is a three-dimensional polymer with moderate molecular weight and crosslinking degree. When subjected to prolonged high temperatures, the agent can form new methylene bridge covalent crosslinking points and, through intermolecular hydrogen bonding, form a supramolecular association system. This allows for the formation of an effectively suspended, stable, high-density solid-phase weighting agent without requiring ultra-high molecular weight polymers. The increased crosslinking degree effectively counteracts the thermal degradation of the polymer by high temperatures, while the high-pressure environment of deep wells significantly enhances the stability of hydrogen bonds. Therefore, neither the polymer matrix nor its supramolecular association system is easily destroyed by high temperatures, thus ensuring its viscosity-reducing performance in completion fluids.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] High-temperature completion fluid viscosity-reducing agent based on covalent-secondary bond double bond interaction has the following general structural formula:

[0008]

[0009] A method for preparing a high-temperature completion fluid viscosity-reducing agent based on covalent-secondary double bond interaction involves using acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and tea polyphenols as raw materials. A terpolymer is prepared through a free radical aqueous solution copolymerization reaction. Then, sulfonated phenolic resin is degraded and activated using MIL-100(Fe) as an activator. Subsequently, the activated sulfonated phenolic resin is grafted and modified using the terpolymer to obtain the final product.

[0010] Preferably, the method for preparing the terpolymer includes the following steps:

[0011] Step S11: At room temperature, in a three-necked flask, dissolve a predetermined amount of tea polyphenols in 20-60 mL of deionized water, and then pour into the flask a mixture of a predetermined amount of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid in deionized water before stirring. After complete dissolution, adjust the pH of the system to 7 with NaOH to obtain mixture A.

[0012] Step S12: Heat the mixture A to the predetermined reaction temperature, add a predetermined amount of initiator, maintain nitrogen purging to remove oxygen, and continue the reaction for the predetermined time to obtain a solution of the crude terpolymer product.

[0013] Step S13: Take out the solution of the crude terpolymer product, wash it three times with an organic solvent, dry it, and finally pulverize it to obtain the amber powder, which is the terpolymer PTAA.

[0014] Preferably, in step S11, the amount of tea polyphenols is 3.6–10.8 g, the amount of acrylamide is 0.2–0.3 mol, the amount of 2-acrylamido-2-methylpropanesulfonic acid is 0.03–0.09 mol, and the amount of deionized water is 75–200 mL; in step S12, the reaction temperature is 45–70 °C, the amount of initiator is 0.08–0.24 g, the initiator is ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the reaction time is 4–9 h; in step S13, the organic solvent is one of methanol, anhydrous ethanol, and acetone.

[0015] Preferably, the method for preparing MIL-100(Fe) includes the following steps:

[0016] Step S21: Under room temperature conditions, add a predetermined amount of ferric chloride hexahydrate and terephthalic acid to a certain amount of deionized water, and sonicate to obtain mixture B;

[0017] Step S22: Add a predetermined amount of nitric acid to the mixture, and sonicate to obtain mixture C;

[0018] Step S23: Transfer the mixture C into a hydrothermal synthesis reactor and react it at a predetermined temperature for a predetermined time to obtain the reactant system;

[0019] Step S24: Centrifuge the reactant system, wash the insoluble matter with deionized water, and vacuum dry to obtain MIL-100(Fe).

[0020] Preferably, in step S21, the amount of ferric chloride hexahydrate is 5-20 mmol, the amount of terephthalic acid is 3.35-13.4 mmol, and the ultrasonic oscillation time is 0.5-2 h; in step S22, the amount of nitric acid is 9-27 mmol, and the ultrasonic oscillation time is 0.5-2 h; in step S23, the predetermined temperature is 120-180℃, and the predetermined time is 12-36 h; in step S24, the centrifugation rate is 5000-10000 rpm, the centrifugation time is 10-30 min, the drying temperature is 50-80℃, and the drying time is 4-10 h.

[0021] Preferably, the activation method of the sulfonated phenolic resin includes the following steps:

[0022] Step S31: Under room temperature conditions, add the amount of activator MIL-100(Fe) powder to a certain amount of deionized water, and sonicate to obtain mixture D;

[0023] Step S32: Add a certain amount of deionized water containing a predetermined amount of sulfonated phenolic resin SMP-3 to the mixture D, and sonicate to obtain mixture E.

[0024] Step S33: Heat the mixture E to a predetermined temperature, remove the ultrasonic oscillation, and turn on the xenon lamp cold light source to irradiate the mixture E for a certain period of time to obtain the activated SMP-3 aqueous solution.

[0025] Preferably, in step S31, the amount of deionized water used is 20-50 mL, the ultrasonic oscillation time is 0.5-2 h, and the amount of MIL-100(Fe) powder used is 0.04-0.08 g; in step S32, the amount of deionized water used is 20-50 mL, the ultrasonic oscillation time is 0.5-2 h, and the amount of sulfonated phenolic resin SMP-3 used is 1.0-2.5 g; in step S33, the predetermined temperature is 40-55℃, and the light irradiation time is 1-4 h.

[0026] Preferably, the grafting modification reaction of the sulfonated phenolic resin includes the following steps:

[0027] Step S41: Under room temperature conditions, a certain amount of activated SMP-3 aqueous solution is poured into a hydrothermal reactor. Under mechanical stirring, deionized water containing a predetermined amount of terpolymer is added. The pH is adjusted to 8-11 using NaOH to obtain mixture F.

[0028] Step S42: Place the reactor in an oven, heat it to the predetermined reaction temperature, and react it for the predetermined time to obtain a crude product solution.

[0029] Step S43: Take out the crude product solution and soak it in excess organic solvent and excess NaCl saturated aqueous solution. After standing for a period of time, separate the soaked liquids using a Soxhlet extractor. Combine the insoluble substances obtained from the two separations, vacuum dry them at a certain temperature for a period of time, and then grind them into powder to obtain the adhesive cutting agent.

[0030] Preferably, in step S41, the amount of activated SMP-3 is 2.4–5.6 g, and the amount of its aqueous solution is 20–50 mL; the amount of the terpolymer is 10.6–25.4 g, and the amount of its aqueous solution is 75–250 mL; in step S42, the predetermined reaction temperature is 120–200 °C, and the predetermined reaction time is 4–10 h; in step S43, the organic solvent is anhydrous ethanol, the standing time for soaking in excess anhydrous ethanol and excess saturated NaCl is 0.5–1.5 h, the vacuum drying temperature is 50–80 °C, and the vacuum drying time is 8–16 h.

[0031] The beneficial effects of this technical solution are as follows:

[0032] I. The present invention provides a high-temperature viscosity-reducing agent for completion fluids based on covalent-secondary bond double bonding. The molecular structure of this viscosity-reducing agent contains functional groups capable of forming both covalent and secondary bonds. When fully hydrated in the completion fluid and subjected to prolonged high temperatures, the hydroxymethyl group can form a strong methylene bridge bond with the active hydrogen on the phenol ring, thereby increasing the polymer crosslinking degree. Dense hydrogen bonds can also form between the hydroxyl groups, enabling the polymer to form a supramolecular dynamic association system. Because downhole high temperatures promote the formation of methylene bridges, the polymer resists high-temperature degradation through crosslinking reactions. High pressure improves the stability of hydrogen bonds, enhancing the structural stability of the dynamic association system. This helps the polymer maintain its polymer properties in high-temperature environments and provides additional structural strength, thus exerting a viscosity-reducing effect to meet the completion operation requirements of deep and ultra-deep wells.

[0033] II. The present invention provides a high-temperature completion fluid viscosity-reducing agent based on covalent-secondary double bond interaction and its preparation method. It uses tea polyphenols and two commonly used vinyl monomers as raw materials to prepare a terpolymer. Then, a MIL-100(Fe) type MOF is prepared. The prepared MIL-100(Fe) type MOF is used to moderately degrade sulfonated phenolic resin SMP-3 to increase its reactivity. Finally, the terpolymer is used to graft the degraded SMP-3 to obtain a three-dimensional polymer viscosity-reducing agent with both covalent and secondary double bond interaction. Attached Figure Description

[0034] Figure 1 The molecular structure of the terpolymer PTAA in Example 1;

[0035] Figure 2 1H NMR spectrum of the terpolymer PTAA in Example 1;

[0036] Figure 3 Electron microscope images of MIL-100 in Example 1;

[0037] Figure 4 XRD pattern of MIL-100 in Example 1;

[0038] Figure 5 Particle size distribution of SMP-3 before and after microwave digestion in Example 1;

[0039] Figure 6 1H NMR spectrum of PSTA, the adhesive-splitting agent in Example 1. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0041] This invention provides a method for preparing a copolymer viscosity enhancer, the specific steps of which are as follows:

[0042] 1. Preparation of terpolymer PTAA

[0043] Step S11: At room temperature, weigh 3.6–10.8 g of tea polyphenols, dissolve them in 20–60 mL of deionized water, pour the solution into a three-necked flask, turn on the magnetic stirrer, and while stirring, pour 75–200 mL of deionized water pre-dissolved with 7.1–21.3 g (0.2–0.3 mol) AM and 6.21–18.63 g (0.03–0.09 mol) AMPS. Stir until completely dissolved, adjust the pH of the system to 7 with NaOH aqueous solution, and purge with nitrogen to remove oxygen.

[0044] Step S12: Heat to 45-70℃, add 0.08-0.24g of initiator (ammonium persulfate and sodium bisulfite, mass ratio 1:1), maintain nitrogen purging to remove oxygen, and continue the reaction for 4-9 hours to obtain a dark brown viscous liquid.

[0045] Step S13: After the liquid cools to room temperature, remove it, wash it three times with anhydrous ethanol, dry it, and finally pulverize it to obtain an amber-colored powder, which is the terpolymer PTAA.

[0046] See Figure 1 and Figure 2 , Figure 1 It is the molecular structural formula of the terpolymer PTAA, composed of... Figure 1It is evident that the molecular structure of PTAA contains numerous hydroxyl groups that can form hydrogen bonds, and its phenolic ring also has numerous active hydrogens that can participate in the formation of methylene bridges. Figure 4 These are 1H NMR images of PTAA, by Figure 4 Therefore, PTAA is known.

[0047] 2. Preparation of MIL-100(Fe) type MOF activator

[0048] Step S21: At room temperature, weigh 1.35–5.4 g (5–20 mmol) of ferric chloride hexahydrate and 0.704–2.816 g (3.35–13.4 mmol) of terephthalic acid, dissolve them in 30–80 mL of deionized water, turn on ultrasonic oscillation, and oscillate for 0.5–2 h to obtain mixture B;

[0049] Step S22: Add 0.567–1.701 g (9–27 mmol) of nitric acid dropwise, and continue ultrasonic oscillation for 0.5–2 h to obtain mixture C;

[0050] Step S23: Transfer the mixture C to a hydrothermal synthesis reactor lined with tetrafluoroethylene, and react at 120-180°C for 12-36 h to obtain the reactant system;

[0051] Step S24: After the reactant system is naturally cooled to room temperature, it is centrifuged at 5000-1000 rpm for 10-30 min to separate the insoluble matter. The insoluble matter is washed three times with deionized water and then placed in a vacuum drying oven and dried at 50-80℃ for 4-10 h. The brick-red powder obtained is MIL-100(Fe) type MOF.

[0052] See Figure 3 and Figure 4 , Figure 3 These are SEM images of MIL-100(Fe), produced by... Figure 3 It can be seen that the average particle size of MIL-100(Fe) particles is only about 150 to 200 nm, which is a typical nanoscale particle, and it exhibits a significant multi-faceted configuration. Figure 4 These are XRD images of MIL-100(Fe), produced by... Figure 4 It can be seen that the sharp peaks in the XRD pattern of MIL-100(Fe) indicate that it has good crystallinity and exhibits a typical crystal structure.

[0053] 3. Degradation and activation of sulfonated phenolic resin SMP-3

[0054] Step S31: At room temperature, pour 0.04-0.08 g of MIL-100(Fe) powder (the amount of activator) into a beaker containing 20-50 mL of deionized water, sonicate until it is completely dispersed, and then pour it into a three-necked flask.

[0055] Step S32: Pour 20-50 mL of deionized water containing 1.0-2.5 g of sulfonated phenolic resin with a value of SMP-3 into a three-necked flask, maintain ultrasonic oscillation and slowly raise the temperature to 40-55°C;

[0056] Step S33: Remove the ultrasonic oscillation and turn on the xenon lamp cold light source to irradiate the three-necked beaker. Maintain the illumination for 1-4 hours. After the solution color changes from black to dark brown, remove the light source to obtain the activated SMP-3 aqueous solution. See the laser particle size distribution diagrams before and after activation. Figure 5 ,Depend on Figure 5 It is known that the particle size of sulfonated phenolic resin SMP-3 before activation is 200-500 μm, while after activation with MIL-100 (Fe), the particle size of SMP-3 is reduced to 150-300 nm, and its average particle size is greatly reduced, which is conducive to its participation in the polymerization reaction.

[0057] 4. Graft modification of sulfonated phenolic resin

[0058] Step S41: At room temperature, pour 2.4–5.6 g of activated SMP-3 into a hydrothermal synthesis reactor containing 20–50 mL of deionized water, turn on magnetic stirring, and pour 75–250 mL of deionized water containing 10.6–25.4 g of PTAA into the flask under stirring. After it is completely dissolved, use NaOH to adjust the pH of the system to 8–11.

[0059] Step S42: Place the reactor in an oven and heat it to 120-200°C for 4-10 hours.

[0060] Step S43: Remove the reaction solution and soak it in an excess of saturated NaCl solution. After standing for 0.5–1.5 hours, separate the insoluble matter from the solution using a Soxhlet extractor. Place the insoluble matter in a vacuum drying oven and dry it at 50–80°C for 6–16 hours. Grind it into powder. The resulting amber powder is the purified copolymer adhesive PSTA. Its 1H NMR spectrum is as follows: Figure 6 As shown.

[0061] Example 1

[0062] This embodiment provides a method for preparing a high-temperature resistant well completion fluid viscosity-lifting agent based on the interaction of covalent and secondary bonds, including the following steps:

[0063] 1.1 Preparation of terpolymer PTAA

[0064] At room temperature, 30 mL of a deionized water solution containing 5.4 g of tea polyphenols was poured into a three-necked flask, and a magnetic stirrer was turned on. While stirring, 100 mL of deionized water containing 14.2 g (0.2 mol) AM and 12.42 g (0.06 mol) AMPS was added. After complete dissolution, the pH of the system was adjusted to 7 with NaOH aqueous solution, and nitrogen was purged to remove oxygen. The mixture was heated in a water bath to 60°C, and 0.16 g of initiator (ammonium persulfate and sodium bisulfite, mass ratio 1:1) was added. The reaction continued for 6 hours under deoxygenation conditions, resulting in a dark brown viscous liquid. The liquid was removed, washed three times with anhydrous ethanol, dried, and finally pulverized to obtain an amber-colored powder, which is the terpolymer PTAA. Its molecular structure is as follows: Figure 1 As shown.

[0065] 1.2. Terpolymer PTAA 1 H NMR spectrum

[0066] See Figure 2 . Figure 2 It is PTAA 1 H NMR spectrum, from Figure 2 It can be seen that the proton peak at δ1.49 is the proton peak of —CH3; at δ1.53 is the proton peak of the primary amine —NH2; at δ1.98 is the proton peak of —OH in lignin; at δ2.82 is the proton peak of CH in the benzene ring of lignin; at δ3.19 is the proton peak of —CH2—; and at δ3.49 is the proton peak of O—CH3 in lignin. The analytical results show that the structure of the tested product is consistent with that of the target product, indicating that the desired final product was successfully prepared.

[0067] 2.1 Preparation of MIL-100(Fe) type MOF

[0068] At room temperature, 2.7 g (10 mmol) of ferric chloride hexahydrate was weighed and dissolved in 50 mL of deionized water. The solution was sonicated until completely dispersed. Under oscillation, 1.408 g (6.7 mmol) of terephthalic acid was added dropwise. After it was fully dissolved, 1.164 g (18 mmol) of nitric acid was added dropwise. The mixture was sonicated for another 30 min and then transferred to a hydrothermal synthesis reactor lined with tetrafluoroethylene. The reaction was carried out at 160 °C for 24 h. The resulting suspension was centrifuged at 8000 rpm for 15 min. The separated insoluble matter was washed three times with deionized water and placed in a vacuum drying oven. The mixture was then vacuum dried at 60 °C for 8 h. The resulting brick-red powder was the MIL-100(Fe) type MOF.

[0069] 2.2 Structural Characterization of MIL-100(Fe) Type MOFs

[0070] See Figure 2 and Figure 3. Figure 2 These are SEM images of MIL-100(Fe), produced by... Figure 1 It can be seen that the average particle size of MIL-100(Fe) particles is only about 100nm, which is a typical nanoscale particle, and it exhibits a significant multi-faceted configuration. Figure 2 These are XRD images of MIL-100(Fe), produced by... Figure 3 It can be seen that the sharp peaks in the XRD pattern of MIL-100(Fe) indicate its good crystallinity and typical crystal structure. Combined with... Figure 2 and Figure 3 The relevant analysis shows that the prepared MIL-100(Fe) is a highly crystalline nano-sized microcrystalline particle, which should have extremely strong catalytic activity.

[0071] 3.1 Degradation and activation of sulfonated phenolic resin SMP-3

[0072] At room temperature, 0.06 g of MIL-100(Fe) powder was poured into a beaker containing 30 mL of deionized water. After ultrasonic oscillation until it was completely dispersed, the powder was poured into a three-necked flask. Then, 30 mL of deionized water containing 2.0 g of sulfonated phenolic resin SMP-3 was poured in. The ultrasonic oscillation was maintained for 1 hour and the temperature was slowly raised to 50 °C. The ultrasonic oscillation was then stopped and the three-necked beaker was irradiated with a xenon lamp cold light source for 2 hours. After the color of the reaction solution changed from black to brown, the light was removed, and the degraded and activated SMP-3 aqueous solution was obtained.

[0073] 3.2 Comparison of particle size of sulfonated phenolic resin SMP-3 before and after degradation and activation

[0074] See 5. Figure 5 This is a comparison of the laser particle size of SMP-3 before and after activation. Figure 5 It is known that the particle size of sulfonated phenolic resin SMP-3 before activation is 200–500 μm, while after activation with MIL-100(Fe), the particle size of SMP-3 decreases to 150–300 nm, and its average particle size is significantly reduced. The reduction in the average molecular weight of SMP-3 not only helps to reduce the steric hindrance effect of the SMP-3 macromolecule, but also exposes more hydroxymethyl functional groups, thus significantly enhancing the activity of SMP-3 in the polymerization reaction.

[0075] 4.1 Preparation of the copolymer viscosity enhancer PSTA

[0076] At room temperature, 30 mL of an aqueous solution containing 3.8 g of activated SMP-3 was poured into a hydrothermal synthesis reactor. Mechanical stirring was started, and 100 mL of deionized water containing 21.2 g of SMP-3 was poured into the reactor under stirring. After complete dissolution, the pH of the solution was adjusted to 10 with NaOH. The reactor was placed in an oven and heated to 160°C for 6 hours. The reaction system was then removed and soaked in excess anhydrous ethanol. The insoluble matter and solution were separated using a Soxhlet extractor. The resulting solution was soaked in an excess of saturated NaCl solution for 1 hour each. The insoluble matter and solution were separated again using a Soxhlet extractor. The two insoluble matter samples were combined and placed in a vacuum drying oven. The samples were vacuum dried at 70°C for 12 hours and then ground into powder. The resulting amber powder is the copolymer adhesive PSTA.

[0077] 4.2 Molecular structure characterization of PSTA.

[0078] See Figure 6 . Figure 6 It's PSTA. 1 H NMR spectrum, from Figure 6 It can be seen that the proton peak at δ1.49 is the proton peak of —CH3; at δ1.53 is the proton peak of the primary amine —NH2; at δ1.98 is the proton peak of —OH in lignin; at δ2.82 is the proton peak of CH in the benzene ring of lignin; at δ3.19 is the proton peak of —CH2—; and at δ3.49 is the proton peak of O—CH3 in lignin. The analytical results show that the structure of the tested product is consistent with that of the target product, indicating that the desired final product was successfully prepared.

[0079] 5. Rheological and filtration loss reduction performance evaluation of self-made viscosity-enhancing and cutting agents in completion fluid systems

[0080] Based on two self-made viscosity-enhancing agents, other treatment agents were selected to form three evaluation high-density completion fluid systems, the specific compositions of which are: (1) 300mL water + 2% mud-forming soil + 0.3% Na2CO3 + 3% PSTA + 4% Redu200 + 1% DSP-2 + 1% NFA-25 + 1% PGCS-1 + 120% WNZY organic salt + 80% ultrafine barite + 160% fine first-grade barite; (2) 300mL water + 2% mud-forming soil + 0.3% Na2CO3 + 3% PSTA + 0.5% VIS-B viscosifier + 4% Redu200 + 1% NFA-25 + 1% polyol C + 1 20% WNZY organic salt + 80% ultrafine grade barite + 160% fine grade one barite; (3) 300mL water + 2% slurry-making soil + 0.3% Na2CO3 + 4% self-made adhesive-enhancing cutting agent PSTA + 2.5% Redu200 + 1% NFA-25 + 1% polyol C + 120% WNZY organic salt + 120% ultrafine grade barite + 120% fine grade one barite, all with a density of 2.2g / cm³. 3 After the slurry was prepared and cured in a sealed environment at room temperature for 24 hours, the rheological and filtration performance of three high-density completion fluid systems were tested and evaluated according to the evaluation methods in the national standard GB / T 16783.1-2014 Petroleum and Natural Gas Industry Drilling Fluid Field Testing Part 1: Water-based Drilling Fluids. The aging conditions for the evaluation were 180℃ × 16h. The experimental results are shown in Table 1.

[0081] Table 1. Effects of self-made viscosity-enhancing agent (Example 1) on the rheology and filtration properties of completion fluid.

[0082]

[0083] Table 1 shows that, based on PSTA, the three completion fluid systems exhibited good rheological properties before and after aging, with API filtration loss of only 3.2–3.4 mL before aging. After aging at 180℃ for 16 h, the apparent and plastic viscosities of the three systems only decreased slightly, while maintaining a certain dynamic shear strength. Meanwhile, the API filtration loss of the aged systems was only 5.4–5.6 mL. The data in Table 1 indicate that the three completion fluid systems maintained good rheological and filtration properties before and after aging, and were resistant to temperatures up to 180℃.

[0084] 6. Evaluation of the rolling recovery and hydration expansion performance of the viscosity-enhancing agent PSTA in the completion fluid system

[0085] Based on the evaluation methods in the oil and gas industry standard "SY / T 5613-2016 Test Methods for Physical and Chemical Properties of Shale and Shale in Drilling Fluids", the shale rolling recovery rate and hydration expansion of three completion fluid systems were tested and evaluated. The experimental results are shown in Table 2.

[0086] Table 2. Results of Shale Rolling Recovery and Hydration Swelling Tests in the Completion Fluid System of Example 1

[0087]

[0088] As shown in Table 2, the expansion rate of the three completion fluid systems based on PSTA after soaking the standard core was less than 1.0%, while the shale rolling recovery rate was >95%, indicating that the three completion fluid systems constructed can effectively inhibit the hydration expansion and dispersion of shale.

[0089] 7. The effect of viscosity-enhancing agent PSTA on the settling properties of completion fluid systems

[0090] Based on the evaluation methods in the oil and gas industry standard "SY / T 5613-2016 Test Method for Physical and Chemical Properties of Drilling Fluids and Shale", three completion fluid systems were subjected to a static aging test at 180℃ for 10 days, and the settling stability of the aging completion fluid systems was tested. The experimental results are shown in Table 3.

[0091] Table 3. Settlement stability test results of the completion fluid system in Example 1.

[0092]

[0093] As shown in Table 3, after the three completion fluid systems were left to stand at 180℃ for 10 days, no water seepage was observed upon opening the tank. Furthermore, when tested with a glass rod, all three systems could freely reach the bottom and make a sound upon contact. Subsequently, the glass rod would naturally adhere to the wall, and there was no sediment at the bottom. The density after aging also did not show significant changes. This indicates that the three completion fluid systems constructed based on PSTA and PDAL will not thicken or separate due to prolonged high-temperature exposure. Moreover, the density of the upper and lower layers remained highly consistent, proving that the system has excellent long-term high-temperature resistance.

[0094] 8. The impact of two copolymer viscosity-enhancing agents on the reservoir protection performance of the completion fluid system

[0095] Based on the evaluation methods in the oil and gas industry standard "SY / T 6540-2021 Indoor Evaluation Method for Damage to Oil Reservoirs by Drilling Fluid and Completion Fluid", reservoir damage assessment tests were conducted on three completion fluid systems. The experimental results are shown in Table 4.

[0096] Table 4 Results of well completion fluid reservoir damage tests

[0097]

[0098] As shown in Table 4, the recovery rate of the core samples from the three high-density completion fluid systems constructed based on PSTA is all above 90%, indicating that the three completion fluid systems caused low damage to the reservoir and have good reservoir protection performance.

[0099] In summary, the viscosity-enhancing and shearing agent of this invention first uses tea polyphenols, acrylamide (AM), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as raw materials to prepare a terpolymer. Then, using a self-made MIL-100(Fe) type MOF as an activator and visible light as a light source, sulfonated phenolic resin SMP-3 is degraded and activated, significantly enhancing its reactivity. The activated SMP-3 is then grafted onto the terpolymer to finally obtain a viscosity-enhancing and shearing agent with both covalent and secondary bond double bonding effects. The preparation method is simple, mild, and yields a high rate of change, while also being low in toxicity and environmentally friendly. When the viscosity-enhancing and shearing agent is dissolved in the completion fluid and subjected to prolonged high temperatures, the hydroxymethyl groups in its molecular structure can form strong methylene bridges with the active hydrogen on the phenolic ring. The abundant hydroxyl functional groups facilitate the formation of supramolecular associative polymers based on hydrogen bond synergy. Due to the combined effects of the aforementioned covalent and secondary bonds, the viscosity-enhancing and shearing agent can maintain polymer properties in long-term high-temperature environments. Three high-density completion fluid systems were developed based on a self-made viscosity-enhancing agent, all with a density of 2.2 g / cm³. 3 It can withstand temperatures up to 180℃ and maintain the stability of the system even after long-term static aging. It also has good shale inhibition and reservoir protection performance.

[0100] Example 2

[0101] This embodiment provides a method for preparing a high-temperature resistant well completion fluid viscosity-lifting agent based on the interaction of covalent and secondary bonds, including the following steps:

[0102] 1. Preparation of terpolymer PTAA

[0103] At room temperature, 60 mL of a deionized water solution containing 10.8 g of tea polyphenols was poured into a three-necked flask, and a magnetic stirrer was turned on. Under stirring, 200 mL of deionized water containing 21.3 g (0.3 mol) AM and 18.63 g (0.09 mol) AMPS was poured into the flask. After complete dissolution, the pH of the system was adjusted to 7 with NaOH aqueous solution, nitrogen was purged to remove oxygen, and the mixture was heated to 70°C in a water bath. Then, 0.24 g of initiator (ammonium persulfate and sodium bisulfite in a mass ratio of 1:1) was added. The reaction was continued for 9 hours under deoxygenation conditions to obtain a dark brown viscous liquid. After removing the liquid, it was washed three times with methanol and dried. The amber powder obtained by pulverizing the powder was the terpolymer PTAA.

[0104] 2. Preparation of MIL-100(Fe) type MOF

[0105] At room temperature, 5.4 g (20 mmol) of ferric chloride hexahydrate was weighed and dissolved in 100 mL of deionized water. The solution was sonicated until completely dispersed. Under oscillation, 2.816 g (13.4 mmol) of terephthalic acid was added dropwise. After it was fully dissolved, 1.746 g (27 mmol) of nitric acid was added dropwise. The mixture was sonicated for another 120 min and then transferred to a hydrothermal synthesis reactor lined with tetrafluoroethylene. The reaction was carried out at 180 °C for 12 h. The resulting suspension was centrifuged at 10,000 rpm for 15 min. The separated insoluble matter was washed three times with deionized water and placed in a vacuum drying oven. The mixture was then vacuum dried at 80 °C for 4 h. The resulting brick-red powder was the MIL-100(Fe) type MOF.

[0106] 3. Degradation and activation of sulfonated phenolic resin SMP-3

[0107] At room temperature, 0.08 g of MIL-100(Fe) powder was poured into a beaker containing 50 mL of deionized water. After ultrasonic oscillation until it was completely dispersed, the powder was poured into a three-necked flask. Then, 50 mL of deionized water containing 2.5 g of sulfonated phenolic resin SMP-3 was poured in. The ultrasonic oscillation was maintained for 2 h and the temperature was slowly raised to 55 °C. The ultrasonic oscillation was then stopped and the three-necked beaker was irradiated with a xenon lamp cold light source. The irradiation was maintained for 4 h. After the color of the reaction solution changed from black to brown, the irradiation was removed, and the degraded and activated SMP-3 aqueous solution was obtained.

[0108] 4. Preparation of copolymer viscosity enhancer PSTA

[0109] At room temperature, 50 mL of an aqueous solution containing 5.6 g of activated SMP-3 was poured into a hydrothermal synthesis reactor. Mechanical stirring was started, and 250 mL of deionized water containing 25.4 g of SMP-3 was poured into the reactor under stirring. After complete dissolution, the pH of the solution was adjusted to 11 with NaOH. The reactor was placed in an oven and heated to 200°C for 4 hours. The reaction system was then removed and soaked in excess anhydrous ethanol. The insoluble matter was separated from the solution using a Soxhlet extractor. The resulting solution was then soaked in an excess of saturated NaCl solution for 1.5 hours each. The insoluble matter was separated from the solution again using a Soxhlet extractor. The two insoluble matter samples were combined and placed in a vacuum drying oven. The samples were vacuum dried at 80°C for 8 hours and then ground into powder. The resulting amber powder is the copolymer adhesive PSTA.

[0110] 5. Rheological and filtration loss reduction performance evaluation of self-made viscosity-enhancing and cutting agents in completion fluid systems

[0111] Based on two self-made viscosity-enhancing agents, other treatment agents were selected to form three evaluation high-density completion fluid systems, the specific compositions of which are: (1) 300mL water + 2% mud-forming soil + 0.3% Na2CO3 + 3% PSTA + 4% Redu200 + 1% DSP-2 + 1% NFA-25 + 1% PGCS-1 + 120% WNZY organic salt + 80% ultrafine barite + 160% fine first-grade barite; (2) 300mL water + 2% mud-forming soil + 0.3% Na2CO3 + 3% PSTA + 0.5% VIS-B viscosifier + 4% Redu200 + 1% NFA-25 + 1% polyol C + 1 20% WNZY organic salt + 80% ultrafine grade barite + 160% fine grade one barite; (3) 300mL water + 2% slurry-making soil + 0.3% Na2CO3 + 4% self-made adhesive-enhancing cutting agent PSTA + 2.5% Redu200 + 1% NFA-25 + 1% polyol C + 120% WNZY organic salt + 120% ultrafine grade barite + 120% fine grade one barite, all with a density of 2.2g / cm³. 3 After the slurry was prepared and cured in a sealed environment at room temperature for 24 hours, the rheological and filtration properties of the three high-density completion fluid systems were tested and evaluated according to the evaluation methods in the national standard GB / T 16783.1-2014 Petroleum and Natural Gas Industry Drilling Fluid Field Testing Part 1: Water-based Drilling Fluids. The aging conditions in the evaluation were 180℃ × 16h. The experimental results are shown in Table 5.

[0112] Table 5. Effects of self-made viscosity-enhancing agent (Example 2) on the rheology and filtration properties of completion fluid.

[0113]

[0114] Table 5 shows that, based on PSTA, the three completion fluid systems exhibited good rheological properties before and after aging, with API filtration loss of only 3.8–3.2 mL before aging. After aging at 180℃ for 16 h, the apparent and plastic viscosities of the three systems only decreased slightly, while maintaining a certain dynamic shear strength. Meanwhile, the API filtration loss of the aged systems was only 4.4–4.8 mL. In summary, the data in Table 1 indicate that the three completion fluid systems maintained good rheological and filtration properties before and after aging, and were resistant to temperatures up to 180℃.

[0115] 6. Evaluation of the rolling recovery and hydration expansion performance of the viscosity-enhancing agent PSTA in the completion fluid system

[0116] Based on the evaluation methods in the oil and gas industry standard "SY / T 5613-2016 Test Methods for Physical and Chemical Properties of Shale in Drilling Fluids", the shale rolling recovery rate and hydration expansion of three completion fluid systems were tested and evaluated. The experimental results are shown in Table 6.

[0117] Table 6. Results of Shale Rolling Recovery and Hydration Swelling Tests in the Completion Fluid System in Example 2.

[0118]

[0119] As shown in Table 6, the expansion rate of the three completion fluid systems based on PSTA after soaking the standard core was less than 1.0%, while the shale rolling recovery rate was >96%, indicating that the three completion fluid systems constructed can effectively inhibit the hydration expansion and dispersion of shale.

[0120] 7. The effect of viscosity-enhancing agent PSTA on the settling properties of completion fluid systems

[0121] Based on the evaluation methods in the oil and gas industry standard "SY / T 5613-2016 Test Method for Physical and Chemical Properties of Drilling Fluids and Shale", three completion fluid systems were subjected to a static aging test at 180℃ for 10 days, and the settling stability of the aging completion fluid systems was tested. The experimental results are shown in Table 7.

[0122] Table 7. Settlement stability test results of the completion fluid system in Example 2.

[0123]

[0124] As shown in Table 7, after the three completion fluid systems were left to stand at 180℃ for 10 days, no water seepage was observed upon opening the tank. Furthermore, when tested with a glass rod, all three systems could freely reach the bottom and make a sound upon contact. Subsequently, the glass rod would naturally adhere to the wall, and there was no sediment at the bottom. The density after aging also did not show significant changes. This indicates that the three completion fluid systems constructed based on PSTA and PDAL will not thicken or separate due to prolonged high-temperature exposure. Moreover, the density of the upper and lower layers remained highly consistent, proving that the system has excellent long-term high-temperature resistance.

[0125] 8. The impact of two copolymer viscosity-enhancing agents on the reservoir protection performance of the completion fluid system

[0126] Based on the evaluation methods in the oil and gas industry standard "SY / T 6540-2021 Indoor Evaluation Method for Damage to Oil Reservoirs by Drilling Fluid and Completion Fluid", reservoir damage assessment tests were conducted on three completion fluid systems. The experimental results are shown in Table 8.

[0127] Table 8 Results of reservoir damage tests using completion fluid in Example 2

[0128]

[0129] As shown in Table 8, the recovery rate of the core samples from the three high-density completion fluid systems constructed based on PSTA is all above 90%, indicating that the three completion fluid systems caused low damage to the reservoir and have good reservoir protection performance.

[0130] In summary, the viscosity-enhancing and shearing agent of this invention first uses tea polyphenols, acrylamide (AM), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as raw materials to prepare a terpolymer. Then, using a self-made MIL-100(Fe) type MOF as an activator and visible light as a light source, sulfonated phenolic resin SMP-3 is degraded and activated, significantly enhancing its reactivity. The activated SMP-3 is then grafted onto the terpolymer to finally obtain a viscosity-enhancing and shearing agent with both covalent and secondary bond double bonding effects. The preparation method is simple, mild, and yields a high rate of change, while also being low in toxicity and environmentally friendly. When the viscosity-enhancing and shearing agent is dissolved in the completion fluid and subjected to prolonged high temperatures, the hydroxymethyl groups in its molecular structure can form strong methylene bridges with the active hydrogen on the phenolic ring. The abundant hydroxyl functional groups facilitate the formation of supramolecular associative polymers based on hydrogen bond synergy. Due to the combined effects of the aforementioned covalent and secondary bonds, the viscosity-enhancing and shearing agent can maintain polymer properties in long-term high-temperature environments. Three high-density completion fluid systems were developed based on a self-made viscosity-enhancing agent, all with a density of 2.2 g / cm³. 3 It can withstand temperatures up to 180℃ and maintain the stability of the system even after long-term static aging. It also has good shale inhibition and reservoir protection performance.

[0131] Example 3

[0132] This embodiment provides a method for preparing a high-temperature resistant well completion fluid viscosity-lifting agent based on the interaction of covalent and secondary bonds, including the following steps:

[0133] 1. Preparation of terpolymer PTAA

[0134] At room temperature, 20 mL of a deionized water solution containing 3.6 g of tea polyphenols was poured into a three-necked flask, and a magnetic stirrer was turned on. Under stirring, 75 mL of deionized water containing 17.7 g (0.25 mol) AM and 4.14 g (0.03 mol) AMPS was poured into the flask. After complete dissolution, the pH of the system was adjusted to 7 with NaOH aqueous solution, nitrogen was purged to remove oxygen, and the mixture was heated to 45°C in a water bath. Then, 0.08 g of initiator (ammonium persulfate and sodium bisulfite in a mass ratio of 1:1) was added. The reaction was continued for 4 hours under deoxygenation conditions to obtain a dark brown viscous liquid. After removing the liquid, it was washed three times with acetone and dried. The amber powder obtained by pulverizing the powder was the terpolymer PTAA.

[0135] 2. Preparation of MIL-100(Fe) type MOF

[0136] At room temperature, 1.25 g (5 mmol) of ferric chloride hexahydrate was weighed and dissolved in 25 mL of deionized water. The solution was sonicated until completely dispersed. Under oscillation, 0.704 g (3.35 mmol) of terephthalic acid was added dropwise. After it was fully dissolved, 0.582 g (9 mmol) of nitric acid was added dropwise. The mixture was sonicated for another 60 min and then transferred to a hydrothermal synthesis reactor lined with tetrafluoroethylene. The reaction was carried out at 120 °C for 36 h. The resulting suspension was centrifuged at 5000 rpm for 15 min. The separated insoluble matter was washed three times with deionized water and placed in a vacuum drying oven. The mixture was then vacuum dried at 50 °C for 10 h. The resulting brick-red powder was the MIL-100(Fe) type MOF.

[0137] 3. Degradation and activation of sulfonated phenolic resin SMP-3

[0138] At room temperature, 0.04 g of MIL-100(Fe) powder was poured into a beaker containing 20 mL of deionized water. After ultrasonic oscillation until it was completely dispersed, the powder was poured into a three-necked flask. Then, 20 mL of deionized water containing 1.0 g of sulfonated phenolic resin SMP-3 was poured in. The ultrasonic oscillation was maintained for 0.5 h and the temperature was slowly raised to 40 °C. The ultrasonic oscillation was then stopped and the three-necked beaker was irradiated with a xenon lamp cold light source. The irradiation was maintained for 1 h. After the color of the reaction solution changed from black to brown, the irradiation was removed, and the degraded and activated SMP-3 aqueous solution was obtained.

[0139] 4. Preparation of copolymer viscosity enhancer PSTA

[0140] At room temperature, 20 mL of an aqueous solution containing 2.4 g of activated SMP-3 was poured into a hydrothermal synthesis reactor. Mechanical stirring was started, and 75 mL of deionized water containing 10.6 g of SMP-3 was poured into the reactor under stirring. After complete dissolution, the pH of the solution was adjusted to 8 with NaOH. The reactor was placed in an oven and heated to 120 °C for 10 h. The reaction system was then removed and soaked in excess anhydrous ethanol. The insoluble matter and solution were separated using a Soxhlet extractor. The resulting solution was soaked in an excess of saturated NaCl solution for 0.5 h each. The insoluble matter and solution were separated again using a Soxhlet extractor. The two insoluble matter samples were combined and placed in a vacuum drying oven. The samples were vacuum dried at 50 °C for 16 h and then ground into powder. The resulting amber powder is the copolymer adhesive PSTA.

[0141] 5. Rheological and filtration loss reduction performance evaluation of self-made viscosity-enhancing and cutting agents in completion fluid systems

[0142] Based on two self-made viscosity-enhancing agents, other treatment agents were selected to form three evaluation high-density completion fluid systems, the specific compositions of which are: (1) 300mL water + 2% mud-forming soil + 0.3% Na2CO3 + 3% PSTA + 4% Redu200 + 1% DSP-2 + 1% NFA-25 + 1% PGCS-1 + 120% WNZY organic salt + 80% ultrafine barite + 160% fine first-grade barite; (2) 300mL water + 2% mud-forming soil + 0.3% Na2CO3 + 3% PSTA + 0.5% VIS-B viscosifier + 4% Redu200 + 1% NFA-25 + 1% polyol C + 1 20% WNZY organic salt + 80% ultrafine grade barite + 160% fine grade one barite; (3) 300mL water + 2% slurry-making soil + 0.3% Na2CO3 + 4% self-made adhesive-enhancing cutting agent PSTA + 2.5% Redu200 + 1% NFA-25 + 1% polyol C + 120% WNZY organic salt + 120% ultrafine grade barite + 120% fine grade one barite, all with a density of 2.2g / cm³. 3 After the slurry was prepared and cured in a sealed environment at room temperature for 24 hours, the rheological and filtration properties of the three high-density completion fluid systems were tested and evaluated according to the evaluation methods in the national standard GB / T 16783.1-2014 Petroleum and Natural Gas Industry Drilling Fluid Field Testing Part 1: Water-based Drilling Fluids. The aging conditions for the evaluation were 180℃ × 16h. The experimental results are shown in Table 9.

[0143] Table 9. Effects of self-made viscosity-enhancing agent (Example 3) on the rheology and filtration properties of completion fluid.

[0144]

[0145]

[0146] As shown in Table 9, the three completion fluid systems based on PSTA exhibited good rheological properties before and after aging, with API filtration loss of only 3.6–4.0 mL before aging. After aging at 180℃ for 16 h, the apparent and plastic viscosities of the three systems only decreased slightly, while maintaining a certain dynamic shear strength. Meanwhile, the API filtration loss of the aged systems was only 5.2–5.8 mL. The data in Table 9 indicate that the three completion fluid systems maintained good rheological and filtration properties before and after aging, and were resistant to temperatures up to 180℃.

[0147] 6. Evaluation of the rolling recovery and hydration expansion performance of the viscosity-enhancing agent PSTA in the completion fluid system

[0148] Based on the evaluation methods in the oil and gas industry standard "SY / T 5613-2016 Test Methods for Physical and Chemical Properties of Shale in Drilling Fluids", the shale rolling recovery rate and hydration expansion of three completion fluid systems were tested and evaluated. The experimental results are shown in Table 10.

[0149] Table 10 Results of Shale Rolling Recovery and Hydration Swelling Tests in Completement Fluid System in Example 3

[0150]

[0151] As shown in Table 2, the expansion rate of the three completion fluid systems based on PSTA after soaking the standard core was less than 1.0%, while the shale rolling recovery rate was >97%, indicating that the three completion fluid systems constructed can effectively inhibit the hydration expansion and dispersion of shale.

[0152] 7. The effect of viscosity-enhancing agent PSTA on the settling properties of completion fluid systems

[0153] Based on the evaluation methods in the oil and gas industry standard "SY / T 5613-2016 Test Method for Physical and Chemical Properties of Drilling Fluids and Shale", three completion fluid systems were subjected to a static aging test at 180℃ for 10 days, and the settling stability of the aging completion fluid systems was tested. The experimental results are shown in Table 11.

[0154] Table 11 Results of Settlement Stability Test of Completion Fluid System in Example 3

[0155]

[0156]

[0157] As shown in Table 11, after the three completion fluid systems were left to stand at 180℃ for 10 days, no water seepage was observed upon opening the tank. Furthermore, when tested with a glass rod, all three systems could freely reach the bottom and make a sound upon contact. Subsequently, the glass rod would automatically adhere to the wall, and there was no sediment at the bottom. The density after aging also did not show significant changes. This indicates that the three completion fluid systems constructed based on PSTA and PDAL will not thicken or separate due to prolonged high-temperature exposure. Moreover, the density of the upper and lower layers remained highly consistent, proving that the system has excellent long-term high-temperature resistance.

[0158] 8. The impact of two copolymer viscosity-enhancing agents on the reservoir protection performance of the completion fluid system

[0159] Based on the evaluation methods in the oil and gas industry standard "SY / T 6540-2021 Indoor Evaluation Method for Damage to Oil Reservoirs by Drilling Fluid and Completion Fluid", reservoir damage assessment tests were conducted on three completion fluid systems. The experimental results are shown in Table 12.

[0160] Table 12 Results of reservoir damage tests using completion fluid in Example 3

[0161]

[0162] As shown in Table 12, the recovery rate of the core samples from the three high-density completion fluid systems constructed based on PSTA is all above 90%, indicating that the three completion fluid systems have low damage to the reservoir and have good reservoir protection performance.

[0163] In summary, the viscosity-enhancing and shearing agent of this invention first uses tea polyphenols, acrylamide (AM), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as raw materials to prepare a terpolymer. Then, using a self-made MIL-100(Fe) type MOF as an activator and visible light as a light source, sulfonated phenolic resin SMP-3 is degraded and activated, significantly enhancing its reactivity. The activated SMP-3 is then grafted onto the terpolymer to finally obtain a viscosity-enhancing and shearing agent with both covalent and secondary bond double bonding effects. The preparation method is simple, mild, and yields a high rate of change, while also being low in toxicity and environmentally friendly. When the viscosity-enhancing and shearing agent is dissolved in the completion fluid and subjected to prolonged high temperatures, the hydroxymethyl groups in its molecular structure can form strong methylene bridges with the active hydrogen on the phenolic ring. The abundant hydroxyl functional groups facilitate the formation of supramolecular associative polymers based on hydrogen bond synergy. Due to the combined effects of the aforementioned covalent and secondary bonds, the viscosity-enhancing and shearing agent can maintain polymer properties in long-term high-temperature environments. Three high-density completion fluid systems were developed based on a self-made viscosity-enhancing agent, all with a density of 2.2 g / cm³. 3 It can withstand temperatures up to 180℃ and can withstand prolonged static aging.

[0164] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction, characterized in that: Its general structural formula is: 。 2. A method for preparing a high-temperature resistant well completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction, characterized in that: A terpolymer was prepared by copolymerizing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and tea polyphenols in an aqueous free radical solution. Then, sulfonated phenolic resin was degraded and activated by MIL-100(Fe) as an activator. Subsequently, the activated sulfonated phenolic resin was grafted with the terpolymer to obtain the final product.

3. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 2, characterized in that: The method for preparing the terpolymer includes the following steps: Step S11: At room temperature, in a three-necked flask, dissolve a predetermined amount of tea polyphenols in 20-60 mL of deionized water, and then pour into the flask a mixture of a predetermined amount of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid in deionized water before stirring. After complete dissolution, adjust the pH of the system to 7 with NaOH to obtain mixture A. Step S12: Heat the mixture A to the predetermined reaction temperature, add a predetermined amount of initiator, maintain nitrogen purging to remove oxygen, and continue the reaction for the predetermined time to obtain a solution of the crude terpolymer product. Step S13: Take out the solution of the crude terpolymer product, wash it three times with an organic solvent, dry it, and finally pulverize it to obtain the amber powder, which is the terpolymer PTAA.

4. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 3, characterized in that: In step S11, the amount of tea polyphenols used is 3.6~10.8 g, the amount of acrylamide used is 0.2~0.3 mol, the amount of 2-acrylamido-2-methylpropanesulfonic acid used is 0.03~0.09 mol, and the amount of deionized water used is 75~200 mL; in step S12, the reaction temperature is 45~70 ℃, the amount of initiator used is 0.08~0.24 g, the initiator is ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the reaction time is 4~9 h; in step S13, the organic solvent is one of methanol, anhydrous ethanol and acetone.

5. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 4, characterized in that: The preparation method of the MIL-100(Fe) includes the following steps: Step S21: Under room temperature conditions, add a predetermined amount of ferric chloride hexahydrate and terephthalic acid to a certain amount of deionized water, and sonicate to obtain mixture B; Step S22: Add a predetermined amount of nitric acid to the mixture, and sonicate to obtain mixture C; Step S23: Transfer the mixture C into a hydrothermal synthesis reactor and react it at a predetermined temperature for a predetermined time to obtain the reactant system; Step S24: Centrifuge the reactant system, wash the insoluble matter with deionized water, and vacuum dry to obtain MIL-100(Fe).

6. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 5, characterized in that: In step S21, the amount of ferric chloride hexahydrate is 5-20 mmol, the amount of terephthalic acid is 3.35-13.4 mmol, and the ultrasonic oscillation time is 0.5-2 h; in step S22, the amount of nitric acid is 9-27 mmol, and the ultrasonic oscillation time is 0.5-2 h; in step S23, the predetermined temperature is 120-180 ℃, and the predetermined time is 12-36 h; in step S24, the centrifugation rate is 5000-10000 rpm, the centrifugation time is 10-30 min, the drying temperature is 50-80 ℃, and the drying time is 4-10 h.

7. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 6, characterized in that: The activation method for the sulfonated phenolic resin includes the following steps: Step S31: Under room temperature conditions, add the amount of activator MIL-100(Fe) powder to a certain amount of deionized water, and sonicate to obtain mixture D; Step S32: Add a certain amount of deionized water containing a predetermined amount of sulfonated phenolic resin SMP-3 to the mixture D, and sonicate to obtain mixture E. Step S33: Heat the mixture E to a predetermined temperature, remove the ultrasonic oscillation, and turn on the xenon lamp cold light source to irradiate the mixture E for a certain period of time to obtain the activated SMP-3 aqueous solution.

8. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 7, characterized in that: In step S31, the amount of deionized water used is 20-50 mL, the ultrasonic oscillation time is 0.5-2 h, and the amount of MIL-100(Fe) powder used is 0.04-0.08 g; in step S32, the amount of deionized water used is 20-50 mL, the ultrasonic oscillation time is 0.5-2 h, and the amount of sulfonated phenolic resin SMP-3 used is 1.0-2.5 g; in step S33, the predetermined temperature is 40-55 ℃, and the light irradiation time is 1-4 h.

9. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 8, characterized in that: The grafting modification reaction of the sulfonated phenolic resin includes the following steps: Step S41: Under room temperature conditions, a certain amount of activated SMP-3 aqueous solution is poured into a hydrothermal reactor. Under mechanical stirring, deionized water containing a predetermined amount of terpolymer is added. The pH is adjusted to 8-11 using NaOH to obtain mixture F. Step S42: Place the reactor in an oven, heat it to the predetermined reaction temperature, and react it for the predetermined time to obtain a crude product solution. Step S43: Take out the crude product solution and soak it in excess organic solvent and excess NaCl saturated aqueous solution. After standing for a period of time, separate the soaked liquids using a Soxhlet extractor. Combine the insoluble substances obtained from the two separations, vacuum dry them at a certain temperature for a period of time, and then grind them into powder to obtain the adhesive cutting agent.

10. The preparation method of the high-temperature completion fluid viscosity-lifting agent based on covalent-secondary bond double bond interaction according to claim 9, characterized in that: In step S41, the amount of activated SMP-3 is 2.4~5.6 g, and the amount of its aqueous solution is 20~50 mL; the amount of the terpolymer is 10.6~25.4 g, and the amount of its aqueous solution is 75~250 mL; in step S42, the predetermined reaction temperature is 120~200 ℃, and the predetermined reaction time is 4~10 h; in step S43, the organic solvent is anhydrous ethanol, and the standing time for soaking in excess anhydrous ethanol and excess saturated NaCl is 0.5~1.5 h; the vacuum drying temperature is 50~80 ℃, and the vacuum drying time is 8~16 h.

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