Preparation method and application of blocking agent based on dynamic disulfide bonds

Abstract

The invention provides a preparation method of a blocking agent based on dynamic disulfide bonds, which comprises the following steps: preparation of BMPE, preparation of a pH response prepolymer, preparation of a Fe < 3 + > coordination enhanced three-dimensional network material, and in-situ nano-dispersion to obtain the blocking agent based on dynamic disulfide bonds. The invention further provides application for plugging micro-cracks such as shaft cement annular gaps and pipe column gaps. Dynamic disulfide bonds and pH response groups and carboxylic acid groups are combined to construct a multi-response dynamic network system, pressure and chemical environment double-trigger repair is achieved, pressure is utilized to trigger fracture and recombination of the disulfide bonds, chemical environment is utilized to trigger ionization state change of the carboxylic acid groups, and fine regulation and control of material performance are achieved. And the self-adaptive plugging capability of the material on micro-cracks in a complex environment is improved. Fe < 3 + > ions are introduced to coordinate with carboxylic acid groups in the polymer to form a complex and adjustable network structure, so that the mechanical property and the stability of the material are improved, and the problem of insufficient mechanical recovery in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of plugging agents, and in particular relates to a preparation method and application of a dynamic disulfide bond-based plugging agent. Background Art

[0002] In the development of unconventional oil and gas resources such as shale gas and tight oil and gas, as the downhole environment becomes increasingly complex, the formation and expansion of micro-leakage cracks such as wellbore cement annulus and tubing voids have become a major hidden danger that causes oil and gas well leakage. Compared with conventional chemical plugging agents, dynamic covalent bonds (such as disulfide bonds) can undergo reversible exchange reactions under specific conditions to automatically repair cracks, significantly improving the long-term stability and service life of plugging agents. In addition, once conventional chemical plugging agents are solidified, their performance is basically fixed, making it difficult to cope with subsequent crack expansion or environmental changes. Dynamic covalent bond plugging agents can dynamically adjust according to environmental changes, maintain the plugging effect, and have stronger adaptability to the environment. The existing crack repair has the following major defects: (1) Single trigger mechanism: The existing technology only relies on a single trigger condition of pressure or temperature, and cannot respond to chemical environmental changes such as CO2 / H2S in unconventional oil and gas wells, resulting in delayed plugging or overreaction. (2) Low mechanical recovery rate: The compressive strength recovery rate of the repaired material is low, making it difficult to withstand the repeated effects of downhole cyclic loads, and the stability of complex media is insufficient. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned existing technologies and provide a preparation method and application of a dynamic disulfide bond plugging agent. This method combines dynamic disulfide bonds with pH-responsive carboxylic acid groups to construct a multi-responsive dynamic network system, achieving dual-trigger repair by pressure and chemical environment. Pressure is used to trigger the breakage and recombination of disulfide bonds, and chemical environment is used to trigger the change in the ionization state of carboxylic acid groups, thereby achieving fine control of material properties and improving the adaptive plugging ability of the material for complex cracks. 3+ The ions coordinate with the carboxylic acid groups in the polymer to form a complex and adjustable network structure, which improves the mechanical properties and stability of the material and overcomes the problem of insufficient mechanical recovery in the existing technology.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a preparation method based on a dynamic disulfide bond blocking agent, characterized in that the method is:

[0005] S1. Preparation of BMPE:

[0006] Using triethylamine as a catalyst, 3-mercaptopropionic acid and ethylene glycol diglycidyl ether react at 60°C for 6 to 8 hours to obtain a cross-linker containing dynamic disulfide bonds, named BMPE;

[0007] S2. Preparation of pH-responsive prepolymer:

[0008] Under nitrogen protection, methacrylic acid, butyl acrylate and azobisisobutyronitrile were mixed to obtain a mixture a, which was reacted at 70°C for 12 to 14 hours to obtain a copolymer containing carboxylic acid groups in the side chains, which was named a pH-responsive prepolymer.

[0009] S3. Covalent cross-linking and coordination strengthening:

[0010] FeCl3·6H2O was dissolved in anhydrous ethanol and ultrasonically dispersed. Then, the BMPE obtained in S1 and the pH-responsive prepolymer obtained in S2 were added and mixed to obtain a mixture b. The mixture was reacted at 80°C for 2h to 3h to obtain FeCl3·6H2O. 3+ Coordination-enhanced three-dimensional network material; the mass fraction of FeCl3·6H2O in the mixture b is 1.5%;

[0011] S4, In-situ nanodispersion:

[0012] SiO2 nanopowders were mixed with anhydrous ethanol and ultrasonically dispersed to obtain SiO2 ethanol suspension, which was then mixed with Fe 3 + The coordination-enhanced three-dimensional network materials are mixed to obtain a mixed liquid; and the mixed liquid is dispersed by a high-pressure homogenization method under a pressure of 150 MPa to obtain a dynamic disulfide bond-based blocking agent.

[0013] Preferably, the molar ratio of 3-mercaptopropionic acid, ethylene glycol diglycidyl ether and triethylamine in S1 is 2:1:0.04.

[0014] Preferably, the molar ratio of methacrylic acid to butyl acrylate in S2 is 2:1; and the mass fraction of azobisisobutyronitrile in the mixture a is 0.5%.

[0015] Preferably, the mass ratio of FeCl3·6H2O to anhydrous ethanol in S3 is 1:10; and the time of ultrasonic dispersion in S4 is 30 min to 40 min.

[0016] Preferably, the molar ratio of BMPE to pH-responsive prepolymer in S3 is 1:(1.2-1.5).

[0017] Preferably, the particle size of the SiO2 nanopowder in S4 is 5nm to 10nm; the mass ratio of SiO2 nanopowder to anhydrous ethanol in S4 is 1:10; and the time of ultrasonic dispersion in S4 is 30min to 40min.

[0018] Preferably, the SiO2 nanopowder and the Fe 3+The mass ratio of FeCl3·6H2O used in the preparation of coordination-enhanced three-dimensional network materials is 6:1.

[0019] Preferably, the conditions of the high-pressure homogenization method in S4 are: 3 cycles, 2 minutes per cycle, and 5 minutes interval.

[0020] The present invention also provides an application of a dynamic disulfide bond blocking agent prepared by the above preparation method, wherein the dynamic disulfide bond blocking agent is used for a temperature of ≤130°C and a mineralization of ≤2×10 4 Adaptive plugging of micro-cracks such as cement annulus and tubing voids in complex environments of unconventional oil and gas wells with H2S content ≤5%.

[0021] Preferably, the dynamic disulfide bond plugging agent has a pressure-pH synergistic triggering performance, the pressure triggering threshold is 2 MPa, and the repair efficiency of cement stone cracks is 92.2% to 95.5% under the conditions of 90°C, pressure 5 MPa, and pH = 4; at 130°C, a mineralization of 2×10 4 Under the conditions of high temperature, high mineralization and high corrosion, the mass loss rate of the aging product after 7 days is 3.2% to 3.8%, and the compressive strength recovery rate is 87.5% to 89.2%.

[0022] The dynamic disulfide bond blocking agent prepared by the present invention has the following properties:

[0023] (1) Multi-mode synergistic triggering: Construct a pressure-pH dual response mechanism, which automatically activates the repair function when the fracture pressure is ≥2 MPa and the CO2 concentration is ≥0.5%, adapting to the complex cementing conditions of unconventional oil and gas wells.

[0024] (2) Mechanical properties enhancement: through Fe 3+ The coordination-enhanced dynamic network makes the compressive strength recovery rate after repair ≥95%, meeting the long-term stability requirements of the wellbore.

[0025] In response to the defects of existing dynamic disulfide bond plugging agents such as dynamic attenuation, single triggering mechanism and insufficient mechanical recovery under high temperature, high salinity and corrosive environments, the present invention needs to construct an environmentally adaptive multi-response dynamic network system to achieve efficient adaptive plugging of complex cracks in unconventional oil and gas wellbores.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention can realize the self-repair function triggered by multi-mode collaboration:

[0028] Once cured, conventional chemical plugging agents maintain their properties, making them ineffective in responding to subsequent crack expansion or environmental changes. This invention utilizes dynamic disulfide bonds to create a dual-response mechanism based on pressure and pH. When the fracture pressure is ≥2 MPa and the CO2 concentration is ≥0.5%, the plugging agent automatically activates its repair function. This multi-mode triggering mechanism can adapt to the changing chemical environment in unconventional oil and gas wells, avoiding delayed or overly reactive plugging and improving the plugging agent's adaptability and response speed.

[0029] (2) The present invention can enhance the stability of chemical plugging agents in complex media:

[0030] Conventional plugging agents are prone to failure in complex environments such as highly mineralized formation water and acidic media. The dynamic disulfide bond-based plugging agent in the present invention can be dynamically adjusted according to environmental changes, maintaining stability and effectiveness in these complex media and adapting to complex working conditions.

[0031] (3) The present invention significantly improves the mechanical properties of chemical plugging agents:

[0032] The mechanical property recovery rate of conventional plugging agents after repair is low, usually only 70%-85%, which is difficult to withstand complex downhole working conditions. 3+ The coordination-enhanced dynamic network achieves a compressive strength recovery rate of >95% after repair, meeting the long-term stability requirements of the wellbore. The repaired material can withstand the repeated effects of wellbore cyclic loads, significantly improving the mechanical properties and long-term stability of the plugging agent, ensuring safe operation of the wellbore under complex working conditions.

[0033] (4) The present invention achieves high-efficiency adaptive blocking efficiency:

[0034] Conventional chemical plugging agents have relatively fixed chemical structures and properties, making them difficult to adapt to complex operating conditions through simple adjustments. This invention constructs a multi-responsive dynamic network system that can adapt to different conditions and operating conditions by adjusting the chemical structure and cross-linking network of dynamic covalent bonds. This system achieves efficient and adaptive plugging of micro-leakage cracks, such as wellbore cement annuli and tubing voids, in the complex environments of unconventional oil and gas wells characterized by high temperature, high salinity, and high corrosion.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is Fe in Example 1 of the present invention 3+ Effect of addition amount on changes in mechanical properties of samples.

[0037] Figure 2 is Fe in Example 1 of the present invention 3+ Effect of addition amount on crack repair performance.

[0038] Figure 3 This is a diagram showing the effect of pressure gradient on repair performance in Example 2 of the present invention.

[0039] Figure 4 This is a diagram showing the effect of temperature on crack repair performance in Example 3 of the present invention. DETAILED DESCRIPTION

[0040] Example 1

[0041] The preparation method of the dynamic disulfide bond blocking agent in this embodiment is as follows:

[0042] S1. Preparation of BMPE:

[0043] Using triethylamine as a catalyst, 3-mercaptopropionic acid and ethylene glycol diglycidyl ether were reacted at 60°C for 6 hours to obtain a crosslinker containing dynamic disulfide bonds, named BMPE. The ratio of 3-mercaptopropionic acid, ethylene glycol diglycidyl ether, and triethylamine was 2 mol:1 mol:0.04 mol.

[0044] The bis(3-mercaptopropionic acid) ethylene glycol ester (BMPE) prepared in this step, as a dynamic disulfide bond monomer, provides reversible cross-linking sites. This structure can achieve reversible cross-linking, and the BMPE helps to improve the self-healing ability of the material.

[0045] S2. Preparation of pH-responsive prepolymer:

[0046] Under nitrogen protection, methacrylic acid (MAA), butyl acrylate (BA) and initiator azobisisobutyronitrile (AIBN) were mixed to obtain a mixture a, and the mixture was reacted at 70°C for 12 hours to obtain a copolymer containing carboxylic acid groups in the side chains, which was named a pH-responsive prepolymer; the molar ratio of methacrylic acid to butyl acrylate was 2:1; the mass fraction of azobisisobutyronitrile in the mixture a was 0.5%;

[0047] The pH-responsive prepolymer prepared in this step is used as a pH-responsive monomer, and methacrylic acid (MAA) is introduced. The carboxylic acid group of MAA is protonated in a CO2 environment (pH < 5), triggering a disulfide exchange reaction.

[0048] S3. Covalent cross-linking and coordination strengthening:

[0049] FeCl3·6H2O was dissolved in anhydrous ethanol and ultrasonically dispersed for 30 min. Then, the BMPE obtained in S1 and the pH-responsive prepolymer obtained in S2 were added and mixed to obtain a mixture b. The mixture was subjected to a thiol-ene click reaction at 80 °C for 2 h to obtain FeCl3·6H2O. 3+Coordination-enhanced three-dimensional network material; the molar ratio of BMPE to pH-responsive prepolymer is 1:1.2; the mass fraction of FeCl3·6H2O in the mixture b is 1.5wt.%; the mass ratio of FeCl3·6H2O to anhydrous ethanol is 1:10;

[0050] In this step, Fe is added 3+ Ions, as reinforcing components, strengthen the network toughness through coordination;

[0051] S4, in-situ nanodispersion:

[0052] The SiO2 nanopowder with a particle size of 5nm to 10nm and anhydrous ethanol were mixed in a mass ratio of 1:10, and ultrasonically dispersed for 30min to obtain a SiO2 ethanol suspension. 3+ The coordination-enhanced three-dimensional network material is mixed to obtain a mixed solution; under a pressure of 150 MPa, the mixed solution is dispersed by a high-pressure homogenization method, and the cycle is repeated 3 times, with a single cycle of 2 minutes and an interval of 5 minutes, to enhance the mechanical locking effect of the material at the crack and obtain a dynamic disulfide bond plugging agent; the SiO2 nanopowder and the Fe 3+ The mass ratio of FeCl3·6H2O used in the preparation of coordination-enhanced three-dimensional network materials is 6:1.

[0053] The mechanical properties of the dynamic disulfide bond plugging agent prepared in this example are enhanced by disulfide bonds and Fe 3+ The ions work together to enhance the toughness of the material while maintaining excellent mechanical properties.

[0054] This example uses disulfide bonds (chemical dynamics) and Fe 3+ The coordination bond (physical enhancement) works synergistically to solve the problem of insufficient repair strength of a single mechanism.

[0055] The dynamic disulfide bond-based blocking agent prepared in this embodiment has self-repairing ability: the design of the dynamic disulfide bond and the pH response mechanism can achieve self-repair after damage.

[0056] The dynamic disulfide bond blocking agent prepared in this example has the following properties:

[0057] (1) Through Fe 3+ The coordination enhanced dynamic network makes the disulfide bond plugging agent material added with 1.5wt.% FeCl3·6H2O (i.e., the mass fraction of FeCl3·6H2O in the mixture b in step S3 in this embodiment is 1.5wt.%) moderately balanced in strength and ductility, and the repair efficiency is better than that of FeCl3·6H2O. 3+ Adding disulfide bond blocking agent increased the compressive strength recovery rate by 50% and 42%.

[0058] (2) The preparation method of this embodiment introduces Fe 3+ The ions coordinate with the carboxylic acid groups in the polymer to form a stable and adjustable network structure. 4 In the extreme environment of 5% ppm and 5% H2S, the compressive strength recovery rate of the disulfide bond plugging agent added with 1.5wt.% FeCl3·6H2O reached 87.5%, showing good environmental adaptability.

[0059] Fe-free 3+ The prepared disulfide bond blocking agent was added as a control group. According to the different amounts of FeCl3·6H2O added in step S3 of the preparation method of this embodiment, the performance test of the dynamic disulfide bond blocking agent prepared by the mixture b in step S3 with a mass fraction of FeCl3·6H2O of 0.5wt.%, 1.0wt.%, 1.5wt.%, and 2.0wt.% was conducted.

[0060] (1) Effect of different mass fractions of FeCl3·6H2O on mechanical properties during preparation

[0061] The obtained samples were placed in a constant temperature and humidity chamber (25°C ± 1°C, RH 50% ± 5%) for 24 hours. The tensile strength and elongation at break of the material were obtained using a universal testing machine (ASTM D695) at a tensile rate of 50 mm / min. 3+ It can form coordination bonds with the carbonyl groups in the prepolymer, and within a certain range, as Fe 3+ As the concentration increases, the coordination effect strengthens the interaction force between the molecular chains, improves the rigidity of the material, and also inhibits the chain slippage, resulting in an increase in tensile strength but a decrease in ductility. When the FeCl3·6H2O addition amount is ≥1.5wt.%, the agglomeration of nanoparticles inside the material can cause the mechanical properties to decay, resulting in a decrease in strength. When the FeCl3·6H2O addition amount is 1.5wt.%, the tensile strength can reach 4.39MPa, which is 40.7% higher than the control group, while the elongation at break continues to decrease with FeCl3·6H2O. At 2.0wt.%, the elongation at break is only 42.2% of the initial value. It can be concluded that when the FeCl3·6H2O addition amount is 1.5wt.%, the material strength and ductility are moderately balanced, and the overall performance is the best ( Figure 1 ).

[0062] (2) Effect of different mass fractions of FeCl3·6H2O in the preparation method on crack repair performance

[0063] Fe-free 3+The disulfide bond plugging agent prepared by adding the prepared disulfide bond plugging agent was used as the control group, and the disulfide bond plugging agent prepared in this example with 0.5wt.%, 1.0wt.%, 1.5wt.%, and 2.0wt.% FeCl3·6H2O added was used as the experimental group. The pH of the polymer solution was pre-adjusted to 4, and injected into a simulated cement stone crack device (crack width 100μm, depth 5mm) and placed in a high-temperature and high-pressure reactor. It was cured at 90℃ and 5MPa pressure for 2 hours. The crack repair rate of the control group was only 46.2%, and the compressive strength recovery rate was 55.4%. When the FeCl3·6H2O addition amount was 1.5wt.%, the dynamic reversibility of the disulfide bond and the FeCl3·6H2O addition amount were 1.5wt.%, 1.5wt.%, and 2.0wt.% respectively. 3+ The introduction of coordinated cross-linking network stability reached the optimal state, with a repair efficiency of 92.2% and a compressive strength recovery rate of 95.6%. Further increasing the amount to 2.0wt.%, the repair efficiency dropped to 74.3% and the compressive strength recovery rate dropped to 82.2%. It was concluded that the material repair performance was optimal when the FeCl3·6H2O addition amount was 1.5wt.%. Figure 2 )

[0064] (III) Environmental adaptability: The disulfide bond blocking agent prepared in this example was tested at 130°C and a salinity of 2×10 4 ppm and 5% H2S mixed solution for 7 days (0.5% sodium citrate was added to inhibit the Fe 3+ coordination failure), the mass loss rate is 3.6%, and the compressive strength recovery rate is 87.5%, which meets the long-term plugging requirements under extreme working conditions.

[0065] Example 2

[0066] The preparation method of the dynamic disulfide bond blocking agent in this embodiment is as follows:

[0067] S1. Preparation of BMPE:

[0068] Using triethylamine as a catalyst, 3-mercaptopropionic acid and ethylene glycol diglycidyl ether were reacted at 60°C for 6 hours to obtain a crosslinker containing dynamic disulfide bonds, named BMPE. The ratio of 3-mercaptopropionic acid, ethylene glycol diglycidyl ether, and triethylamine was 2 mol:1 mol:0.04 mol.

[0069] The bis(3-mercaptopropionic acid) ethylene glycol ester (BMPE) prepared in this step, as a dynamic disulfide bond monomer, provides reversible cross-linking sites. This structure can achieve reversible cross-linking, and the BMPE helps to improve the self-healing ability of the material.

[0070] S2. Preparation of pH-responsive prepolymer:

[0071] Under nitrogen protection, methacrylic acid (MAA), butyl acrylate (BA) and initiator azobisisobutyronitrile (AIBN) were mixed to obtain a mixture a, and the mixture was reacted at 70°C for 12 hours to obtain a copolymer containing carboxylic acid groups in the side chains, which was named a pH-responsive prepolymer; the molar ratio of methacrylic acid to butyl acrylate was 2:1; the mass fraction of azobisisobutyronitrile in the mixture a was 0.5%;

[0072] The pH-responsive prepolymer prepared in this step is used as a pH-responsive monomer, and methacrylic acid (MAA) is introduced. The carboxylic acid group of MAA is protonated in a CO2 environment (pH < 5), triggering a disulfide exchange reaction.

[0073] S3. Covalent cross-linking and coordination strengthening:

[0074] FeCl3·6H2O was dissolved in anhydrous ethanol and ultrasonically dispersed for 30 min. Then, the BMPE obtained in S1 and the pH-responsive prepolymer obtained in S2 were added and mixed to obtain a mixture b. The mixture was subjected to a thiol-ene click reaction at 80 °C for 2 h to obtain FeCl3·6H2O. 3+ Coordination-enhanced three-dimensional network material; the molar ratio of BMPE to pH-responsive prepolymer is 1:1.3; the mass fraction of FeCl3·6H2O in the mixture b is 1.5%; the mass ratio of FeCl3·6H2O to anhydrous ethanol is 1:10;

[0075] In this step, Fe is added 3+ Ions, as reinforcing components, strengthen the network toughness through coordination;

[0076] S4, In-situ nanodispersion:

[0077] The SiO2 nanopowder with a particle size of 5nm to 10nm and anhydrous ethanol were mixed in a mass ratio of 1:10, and ultrasonically dispersed for 30min to obtain a SiO2 ethanol suspension. 3+ The coordination-enhanced three-dimensional network material is mixed to obtain a mixed solution; under a pressure of 150 MPa, the mixed solution is dispersed by a high-pressure homogenization method, and the cycle is repeated 3 times, with a single cycle of 2 minutes and an interval of 5 minutes, to enhance the mechanical locking effect of the material at the crack and obtain a dynamic disulfide bond plugging agent; the SiO2 nanopowder and the Fe 3+ The mass ratio of FeCl3·6H2O used in the preparation of coordination-enhanced three-dimensional network materials is 6:1.

[0078] The dynamic disulfide bond-based plugging agent prepared in this embodiment adopts a disulfide bond / pH dual-responsive molecular structure design: the dynamic disulfide bond is combined with the pH-responsive group (carboxylic acid group) to construct a multi-responsive dynamic network system to achieve pressure + chemical environment dual-triggered repair. The pressure is used to trigger the breakage and recombination of the disulfide bond, and the chemical environment is used to trigger the change in the ionization state of the carboxylic acid group, thereby achieving fine regulation of the material properties and improving the material's adaptive plugging ability for complex cracks.

[0079] The triggering mechanism of the dynamic disulfide bond plugging agent prepared in this embodiment for plugging micro-cracks in cement annulus is dual-mode triggering. The principle of the dual-mode triggering is as follows:

[0080] ① Pressure triggering: When cracks are generated, dynamic disulfide bonds (SS bond energy ≈ 268 kJ / mol) are preferentially broken, releasing thiol groups (-SH) to initiate exchange reactions;

[0081] ② Chemical triggering: In a CO2-rich environment (pH 4-5), the carboxylic acid group of MAA is protonated, lowering the pH of the system and activating the dynamic equilibrium of thiol-disulfide bonds (pKa≈4.5), accelerating network reconstruction.

[0082] The dynamic disulfide bond blocking agent prepared in this example has the following properties:

[0083] (1) Construct a pressure-pH dual response mechanism, which automatically activates the repair function when the crack pressure is ≥2 MPa and the CO2 concentration is ≥0.5%.

[0084] (2) Based on the pressure-pH synergistic triggering mechanism, the disulfide bond plugging agent added with 1.5% wt.% FeCl3·6H2O achieved a crack repair rate of 95.5% and a compressive strength recovery rate of 96.4% under the experimental conditions of 90°C, 5 MPa pressure, and pH = 4, which can achieve dynamic regulation of crack repair.

[0085] (3) Environmental adaptability: The preparation method of this embodiment introduces Fe 3+ The ions coordinate with the carboxylic acid groups in the polymer to form a stable and adjustable network structure. 4 After aging for 7 days in an extreme environment of 5% H2S and 1.5wt.% FeCl3·6H2O, the compressive strength recovery rate of the disulfide bond plugging agent reached 89.2%, meeting the environmental adaptability under extreme working conditions.

[0086] In this example, the performance of the prepared dynamic disulfide bond blocking agent was tested.

[0087] (1) Pressure-triggered disulfide bond reorganization

[0088] (1) A disulfide bond plugging agent material with 1.5% wt.% FeCl3·6H2O added was injected into a simulated cement stone crack device and placed in a high-temperature and high-pressure reactor. The pressure was adjusted to 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, and 5.0 MPa, respectively, and maintained at 90°C for 2 hours. It was found that when the pressure increased from 1.5 MPa to 2.0 MPa, the plugging agent repair efficiency jumped from 48.3% to 75.6%, and the compressive strength recovery rate reached 89.7%, indicating that 2.0 MPa is the minimum effective pressure for dynamic disulfide bond triggering recombination. When the pressure is between 2.0 and 3.0 MPa, the repair performance is significantly improved, and the compressive strength recovery rate is positively correlated with the repair efficiency. When the pressure is greater than 3.0 MPa, the performance tends to be stable, indicating that the disulfide bond network recombination is close to saturation ( Figure 3 ).

[0089] (2) The disulfide bond blocking agent material with 1.5% wt.% FeCl3·6H2O was placed in a high-temperature and high-pressure reactor, and a pressure of 5 MPa was applied and maintained at 90°C for 2 hours. The original SS bond vibration peak (510 cm -1 ) intensity decreased significantly, indicating that pressure induced the cleavage of disulfide bonds to generate sulfhydryl radicals (·SS·), and pressure triggering caused the proportion of ggg configuration to decrease. After unloading, the SS bond vibration peak intensity partially recovered, but the peak position shifted from 510 cm -1 Offset to 515cm -1 The reorganized disulfide bond network shifted from GGG to GGT, forming a new topological configuration, indicating stress-adaptive reorganization (Table 1).

[0090] Table 1 Disulfide bond configuration ratio before and after pressurization

[0091]

[0092]

[0093] (II) pH-triggered carboxylic acid protonation

[0094] The disulfide bond plugging agent material added with 1.5%wt.%FeCl3·6H2O was injected into a simulated cement stone crack device and placed in a high-temperature and high-pressure reactor (crack width 100μm, depth 5mm), and CO2 gas was introduced to control the partial pressure at 0.5-5MPa. After curing for 2 hours, it was concluded that the pH response time was shortened from 120 minutes to 30 minutes when the CO2 partial pressure increased from 0.5MPa to 5MPa; when the CO2 partial pressure was 2.0MPa (pH≈4.0), the protonation of -COOH accelerated the thiol-disulfide bond exchange, the repair efficiency reached the maximum (92.0%), and the compressive strength recovery rate could reach 94.6%. When the CO2 partial pressure was 5.0MPa (pH≈3.0), FeCl3·6H2O was added to the disulfide bond plugging agent material, and the repair efficiency reached the maximum (92.0%). The compressive strength recovery rate could reach 94.6%. 3+The coordination bonds were partially hydrolyzed, and the repair efficiency decreased to 88.3%, and the compressive strength recovery rate was 87.2% (Table 2).

[0095] Table 2 pH-responsive repair efficiency

[0096] Group pH range Repair efficiency (%) Compressive strength recovery rate (%) <![CDATA[Experimental group 1 (CO2 partial pressure 0.5 Mpa)]]> 4.8-5.2 78.4 85.5 <![CDATA[Experimental group 2 (partial pressure of CO2: 2.0 Mpa)]]> 3.5-4.0 92.0 94.6 <![CDATA[Experimental group 3 (CO2 partial pressure 5.0 Mpa)]]> 2.8-3.2 88.3 87.2

[0097] (III) Pressure-pH synergistic triggering repair performance test

[0098] A disulfide plugging agent material containing 1.5 wt.% FeCl₃·6H₂O was injected into a simulated cement stone crack device. Flow experiments demonstrated that pH triggering enhanced interfacial adhesion, while pressure triggering promoted crack repair. The synergistic effect of the two increased repair efficiency by 25%, enabling dynamic regulation of crack repair (Table 3).

[0099] Table 3 Pressure-pH triggered crack repair performance test

[0100]

[0101] (IV) Environmental stability of the dynamic disulfide bond blocking agent prepared in this example

[0102] The disulfide bond blocking agent prepared in this example was heated at 130°C and a salinity of 2×10 4 ppm and 5% H2S mixed solution for 7 days (0.5% sodium citrate was added to inhibit the Fe 3+ coordination failure), the mass loss rate is 3.2%, and the compressive strength recovery rate is 89.2%, which meets the long-term plugging requirements under extreme working conditions.

[0103] Example 3

[0104] The preparation method of the dynamic disulfide bond blocking agent in this embodiment is as follows:

[0105] S1. Preparation of BMPE:

[0106] 3-Mercaptopropionic acid and ethylene glycol diglycidyl ether were reacted with triethylamine as a catalyst at 60°C for 8 hours to obtain a crosslinker containing dynamic disulfide bonds, named BMPE. The ratio of 3-mercaptopropionic acid, ethylene glycol diglycidyl ether, and triethylamine was 2 mol:1 mol:0.04 mol.

[0107] S2. Preparation of pH-responsive prepolymer:

[0108] Under nitrogen protection, methacrylic acid (MAA), butyl acrylate (BA) and initiator azobisisobutyronitrile (AIBN) were mixed to obtain a mixture a, and the mixture was reacted at 70°C for 14 hours to obtain a copolymer containing carboxylic acid groups in the side chains, which was named a pH-responsive prepolymer; the molar ratio of methacrylic acid to butyl acrylate was 2:1; the mass fraction of azobisisobutyronitrile in the mixture a was 0.5%;

[0109] S3. Covalent cross-linking and coordination strengthening:

[0110] FeCl3·6H2O was dissolved in anhydrous ethanol and ultrasonically dispersed for 40 min. Then, the BMPE obtained in S1 and the pH-responsive prepolymer obtained in S2 were added and mixed to obtain a mixture b. The mixture was subjected to a thiol-ene click reaction at 80 °C for 3 h to obtain FeCl3·6H2O. 3+ Coordination-enhanced three-dimensional network material; the molar ratio of BMPE to pH-responsive prepolymer is 1:1.5; the mass fraction of FeCl3·6H2O in the mixture b is 1.5%; the mass ratio of FeCl3·6H2O to anhydrous ethanol is 1:10;

[0111] S4, In-situ nanodispersion:

[0112] SiO2 nanopowder with a particle size of 5nm to 10nm and anhydrous ethanol were mixed at a mass ratio of 1:10, and ultrasonically dispersed for 40 minutes. 3+ The coordination-enhanced three-dimensional network material is mixed to obtain a mixed solution; under a pressure of 150 MPa, the mixed solution is dispersed by a high-pressure homogenization method, and the cycle is repeated 3 times, with a single cycle of 2 minutes and an interval of 5 minutes to obtain a dynamic disulfide bond blocking agent; the SiO2 nanopowder and the Fe 3+ The mass ratio of FeCl3·6H2O used in the preparation of coordination-enhanced three-dimensional network materials is 6:1.

[0113] The dynamic disulfide bond-based plugging agent prepared in this embodiment can be used to plug micro-cracks in cement sheaths of well cementing.

[0114] (1) Test of the repair performance triggered by pressure-pH synergistically in this embodiment

[0115] The pH of the plugging agent polymer solution with an addition amount of 1.5% wt.% FeCl3·6H2O was pre-adjusted to 4 and injected into a simulated cement stone crack device (crack width 100 μm, depth 5 mm). After curing at 90°C and 5 MPa pressure for 2 hours, the crack repair efficiency of this example was 93.7%, and the compressive strength recovery rate was 96.6%.

[0116] (II) Cyclic loading of the dynamic disulfide bond blocking agent prepared in this example

[0117] Fe-free 3+ The prepared disulfide bond blocking agent was added as a control group, and the 1.5 wt.% Fe 3+ The disulfide bond blocking agent was added as the experimental group, and the mixture was cured at 90℃ and 5MPa pressure for 2 hours. After applying static 5MPa pressure for 10 minutes, a 5MPa sinusoidal cyclic load (frequency 0.5Hz) was continuously applied for 10 seconds. 4 The strength attenuation rate of the control group was 28%, the interface peeling length was 1.2 mm, and the fracture toughness (KIC) was 3.1 MPa·m 1 / 2 The strength attenuation rate of the experimental group was 5%, the interface peeling length was 0.2 mm, and the fracture toughness (KIC) was 5.4 MPa·m 1 / 2 . It is concluded that Fe 3+ The coordination bond protects the main disulfide bond network, reducing the intensity decay rate after cycling to 5%, and Fe 3+ The coordination effect with the thiol group enhances the adhesion between the plugging agent and the crack wall, reducing the interface peeling length by 83%; the KIC value of the experimental group reaches 5.4 MPa·m 1 / 2 The fracture toughness of the experimental group was significantly improved, providing an innovative solution for the long-term sealing of micro-cracks in the cement annulus (Table 4).

[0118] Table 4 Comparison of cyclic load tolerance

[0119] parameter <![CDATA[Control group (without Fe 3+ )]]> <![CDATA[Experimental group (containing Fe 3+ )]]> Strength decay rate 28％ 5％ Interface peeling length 1.2mm 0.2mm Fracture toughness (KIC) <![CDATA[3.1MPa·m 1 / 2 ]]> <![CDATA[5.4MPa·m 1 / 2 ]]>

[0120] (III) Environmental stability of the dynamic disulfide bond blocking agent prepared in this example

[0121] (1) Stability in high temperature environment

[0122] The pH value of the plugging agent polymer solution with a 1.5% wt.% FeCl3·6H2O addition was pre-adjusted to 4, and a cement stone crack device (crack width 100 μm, depth 5 mm) was simulated. The temperature was adjusted to 30℃, 60℃, 90℃, 110℃, 130℃, and 150℃ for 2 hours. The plugging agent showed no attenuation within 130℃. The crack plugging efficiency at 130℃ was 94.9%, and the compressive strength recovery rate was 97.8% ( Figure 4 After aging the cured sample in a 130°C oven for 7 days, the compressive strength recovery rate was 85.5%, showing the potential for application in deep well high-temperature environments.

[0123] (2) High mineralization environmental stability

[0124] The 1.5% wt.% disulfide bond blocking agent prepared in this example was used as the experimental group, without Fe3+ The prepared disulfide bond blocking agent was added as the control group, and the samples were immersed in 90℃ and 2×10 4 ppm simulated formation water for 7 days. The mass loss rate of the experimental group was 2.1% and the compressive strength recovery rate was 92.3% after 7 days. Compared with the control group, the adaptability to the high mineralization environment was significantly improved (Table 5).

[0125] Table 5 Comparison of environmental stability in high mineralization

[0126] parameter <![CDATA[Control group (without Fe 3+ )]]> <![CDATA[Experimental group (containing Fe 3+ )]]> Mass loss rate 12.4％ 2.1％ Compressive strength recovery rate 55.4％ 92.3％

[0127] (2) Stability in high temperature, high mineralization and corrosive environments

[0128] Fe-free 3+ The control group was treated with the prepared disulfide bond blocking agent. The experimental group was treated with 1.5 wt.% disulfide bond blocking agent prepared in this example. The samples were immersed in a 130°C, 2×10 4 ppm and 5% H2S mixed solution for 7 days (0.5% sodium citrate was added to inhibit the Fe 3+ The mass loss rate of the experimental group was 3.8%, and the compressive strength recovery rate was 88.4%, which met the long-term plugging requirements under extreme working conditions (Table 6).

[0129] Table 6 Comparison of stability in high temperature, high mineralization and corrosive environment

[0130] parameter <![CDATA[Control group (without Fe 3+ )]]> <![CDATA[Experimental group (containing Fe 3+ )]]> Mass loss rate 14.4％ 3.8％ Compressive strength recovery rate 52.0％ 88.4％

[0131] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method based on a dynamic disulfide bond blocking agent, characterized in that: The method is: S1. Preparation of BMPE: Using triethylamine as a catalyst, 3-mercaptopropionic acid and ethylene glycol diglycidyl ether react at 60°C for 6 to 8 hours to obtain a cross-linker containing dynamic disulfide bonds, named BMPE; S2. Preparation of pH-responsive prepolymer: Under nitrogen protection, methacrylic acid, butyl acrylate and azobisisobutyronitrile were mixed to obtain a mixture a, which was reacted at 70°C for 12 to 14 hours to obtain a copolymer containing carboxylic acid groups in the side chains, which was named a pH-responsive prepolymer. S3. Covalent cross-linking and coordination strengthening: FeCl3·6H2O was dissolved in anhydrous ethanol and ultrasonically dispersed. Then, the BMPE obtained in S1 and the pH-responsive prepolymer obtained in S2 were added and mixed to obtain a mixture b. The mixture was reacted at 80°C for 2h to 3h to obtain FeCl3·6H2O. 3+ Coordination-enhanced three-dimensional network material; the mass fraction of FeCl3·6H2O in the mixture b is 1.5%; S4, In-situ nanodispersion: SiO2 nanopowders were mixed with anhydrous ethanol and ultrasonically dispersed to obtain SiO2 ethanol suspension. 3+ The coordination-enhanced three-dimensional network materials are mixed to obtain a mixed liquid; and the mixed liquid is dispersed by a high-pressure homogenization method under a pressure of 150 MPa to obtain a dynamic disulfide bond-based blocking agent.

2. The preparation method of a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The molar ratio of 3-mercaptopropionic acid, ethylene glycol diglycidyl ether and triethylamine in S1 is 2:1:0.

04.

3. The preparation method of a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The molar ratio of methacrylic acid to butyl acrylate in S2 is 2:1; the mass fraction of azobisisobutyronitrile in the mixture a is 0.5%.

4. The preparation method of a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The mass ratio of FeCl 3 ·6H 2 O and anhydrous ethanol in S3 is 1:10; the time of ultrasonic dispersion in S4 is 30 min to 40 min.

5. The method for preparing a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The molar ratio of BMPE and pH-responsive prepolymer in S3 is 1:(1.2-1.5).

6. The method for preparing a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The particle size of the SiO2 nanopowder in S4 is 5nm to 10nm; the mass ratio of the SiO2 nanopowder to anhydrous ethanol in S4 is 1:10; and the ultrasonic dispersion time in S4 is 30min to 40min.

7. The method for preparing a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The SiO2 nanopowder and the Fe 3+ The mass ratio of FeCl3·6H2O used in the preparation of coordination-enhanced three-dimensional network materials is 6:

1.

8. The method for preparing a dynamic disulfide bond blocking agent according to claim 1, characterized in that: The conditions of the high-pressure homogenization method in S4 were: 3 cycles, 2 min each, and 5 min intervals.

9. An application of a dynamic disulfide bond blocking agent prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The dynamic disulfide bond blocking agent is used for temperatures ≤ 130°C and mineralization ≤ 2×10 4 Adaptive plugging of micro-cracks such as cement annulus and tubing voids in complex environments of unconventional oil and gas wells with H2S content ≤5%.

10. The use according to claim 9, characterized in that The dynamic disulfide bond plugging agent has a pressure-pH synergistic triggering performance, the pressure triggering threshold is 2 MPa, and the repair efficiency of cement stone cracks is 92.2% to 95.5% under the conditions of 90°C, pressure 5 MPa, and pH = 4; at 130°C, a mineralization of 2×10 4 Under the conditions of high temperature, high mineralization and high corrosion, the mass loss rate of the aging product after 7 days is 3.2% to 3.8%, and the compressive strength recovery rate is 87.5% to 89.2%.

Images