Deepwater shallow hydrate-containing stratum borehole wall stabilizer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of petrochemical engineering, and provides a deepwater superficial portion hydrate-containing stratum borehole stabilizer and a preparation method and application thereof. The deepwater superficial portion hydrate-containing stratum borehole stabilizer comprises a copolymer of a vinyl lactam monomer, acryloyl dopamine and a derivative of the acryloyl dopamine; the preparation method comprises the following steps: dissolving dopamine and a derivative thereof in a solvent, adjusting to be alkaline, adding an acrylic acid derivative with an acrylic acid or methacrylic acid group, reacting, dissolving the obtained acryloyl dopamine in a solution, mixing and dissolving with a vinyl lactam monomer and an initiator, and carrying out copolymerization reaction. After being added into a drilling fluid, the deepwater shallow hydrate-containing formation well wall stabilizer disclosed by the invention can play a multi-functional role, not only can improve the cementing property between hydrates and mineral particles and between mineral particles in a formation and improve the pressure-bearing strength of the formation, but also can inhibit the decomposition of the hydrates in the formation and the reduction of the strength of the formation, so that the drilling fluid can be well protected. And the well wall instability risk is reduced.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a wellbore stabilizer for shallow hydrate-bearing formations in deep water, its preparation method, and its application. Background Technology

[0002] Wellbore instability is one of the key challenges in deepwater oil and gas and hydrate drilling. Deepwater shallow sediments, primarily composed of silty clay and clayey silt, are characterized by looseness, undercompaction, poor lithology, and high water content, resulting in poor mechanical properties and a narrow drilling fluid safety density window, making them prone to wellbore instability. During drilling, drilling fluid filtrate intrudes into the formation, causing changes in formation pressure and temperature. If the formation contains natural gas hydrates, this can lead to hydrate decomposition. The decomposition of hydrates, which act as cementation and support elements, further affects the formation's cementation strength and effective stress, weakening formation stability. Simultaneously, the influence of drilling fluid temperature and salinity on the hydrate decomposition zone increases with density, causing the plastic zone to expand and narrowing the drilling fluid safety density window, significantly increasing the risk of wellbore instability. Therefore, to ensure the safe and efficient development of hydrates, the key lies in improving the cohesion between sediment particles from a synergistic mechanical-chemical perspective, inhibiting hydrate decomposition, and minimizing formation strength degradation.

[0003] Temperature, pressure, and hydrate decomposition inhibition are key factors affecting the formation hydrate decomposition rate. Theoretically, hydrate decomposition can be inhibited by controlling drilling fluid temperature; however, existing platform cooling equipment cannot fully meet the temperature control requirements of the drilling fluid within the wellbore. Therefore, using hydrate decomposition inhibitors is currently a feasible and effective method to inhibit hydrate decomposition and improve wellbore stability. Additives such as lecithin, polyvinylpyrrolidone (PVP), and polyvinylcaprolactam (PVCap) can delay hydrate decomposition in the formation. However, their decomposition effect is limited, and existing hydrate inhibitors cannot completely inhibit hydrate decomposition.

[0004] Furthermore, shallow deep-sea formations are predominantly composed of silty mudstone with low compaction strength and weak cementation, resulting in a significant decrease in mechanical stability as hydrate saturation decreases. Another approach is to incorporate cementing agents to enhance formation mechanical stability through adsorption and cementation of the formation rocks during drilling. However, most cementing agents fail to rapidly cement and form stable cemented structures in high-water-cut environments, especially under low-temperature conditions in shallow deep water. Therefore, during hydrate drilling, it is necessary to consider not only wellbore instability caused by low formation strength but also the reduction in formation strength due to hydrate decomposition. Currently, research on treatment agents that can simultaneously inhibit hydrate decomposition and strengthen the formation through cementation is lacking. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a wellbore stabilizer for deep-water shallow hydrate-bearing formations, its preparation method, and its application. The wellbore stabilizer for deep-water shallow hydrate-bearing formations provided by this invention can inhibit the decomposition of hydrates in the formation, delay the decline in formation strength caused by hydrate decomposition, and also cement hydrates and formation mineral particles in the near-wellbore zone, improving formation cohesion and reducing the risk of wellbore instability during drilling.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a wellbore stabilizer for shallow hydrate-bearing formations in deep water, comprising a copolymer of vinyl lactam monomers and acryloyl dopamine and its derivatives. The structure is as follows: Formula I:

[0008]

[0009] Ⅰ

[0010] Among them, the monomer containing the ortho-phenolic hydroxyl structure has the following structure, formula II:

[0011]

[0012] II

[0013] Where R1 is an acryloyloxy or methacryloxy, and its structure is as follows: Formula III:

[0014] ,

[0015] III

[0016] R2 has the same structure as R1, either –H or –CH3;

[0017] The structure of R3 is as follows: (Form IV)

[0018] , ,

[0019] IV

[0020] R4 is pyrrolidone or caprolactam, with the following formula V:

[0021] ,

[0022] V

[0023] The preparation method of the copolymer of the vinyl lactam monomer and acryloyl dopamine and its derivatives includes the following steps:

[0024] (1) Dissolve dopamine and its derivatives in a solvent and adjust the solution to alkaline to obtain a solution of dopamine and its derivatives;

[0025] (2) The dopamine and its derivative solution is mixed with triethylchlorosilane, and the resulting reaction solution is reacted. After the reaction is completed, an acrylic acid derivative with an acrylic acid or methacrylic acid group is added to obtain acryloyl dopamine and its derivative.

[0026] (3) Dissolve the acryloyldopamine and its derivatives in a solvent to obtain a solution of acryloyldopamine and its derivatives;

[0027] (4) Mix acrylamide and its derivative solution, vinyl lactam monomer and initiator, and carry out polymerization reaction in the resulting reaction solution. After the reaction is completed, add HCl solution to obtain the copolymer of the vinyl lactam monomer and acrylamide and its derivative.

[0028] Preferably, step (1) is carried out under stirring and nitrogen protection conditions. The dopamine and its derivatives are dopamine hydrochloride, levodopa, norepinephrine, or methyldopamine. The solvent is at least one of water, ethanol, N,N-dimethylformamide, and dichloromethane.

[0029] Preferably, in step (2), the molar number of triethylchlorosilane is 2 to 3 times the molar number of dopamine and its derivatives, and the reaction is maintained at 30°C. The acrylic acid derivative with acrylic acid or methacrylic acid groups is at least one of acryloyl chloride, methacryloyl chloride, acrylic anhydride, and methacrylic anhydride. The molar number of the acrylic acid derivative with acrylic acid or methacrylic acid groups is 1.2 to 2 times the molar number of dopamine and its derivatives, and the reaction is maintained at 45°C.

[0030] In step (3), the solvent is at least one of water, ethanol, and N,N-dimethylformamide.

[0031] Preferably, in step (4), the vinyl lactam monomer is at least one of N-vinylpyrrolidone and N-vinylcaprolactam. The initiator is one or more of azobisisobutyronitrile, ammonium persulfate, and hydrogen peroxide. The copolymerization reaction is carried out at a temperature of 70-90°C for 6-12 hours.

[0032] The present invention also provides the application of the wellbore stabilizer for deep-water shallow hydrate-bearing formations described in the above technical solution in drilling fluid.

[0033] Preferably, the wellbore stabilizer for shallow hydrate-bearing formations in deep water has a content of 0.5% to 2.0 wt% in the drilling fluid.

[0034] The wellbore stabilizer for shallow hydrate-bearing formations of the present invention uses a copolymer of vinyl lactam monomers and acryloyl dopamine and its derivatives as the main component. When added to drilling fluid, it can play a multi-functional role, which can inhibit the decomposition of hydrates in the formation, slow down the decline of formation strength, and bind hydrate particles and formation minerals, improve formation cohesion, and reduce the risk of formation instability. Detailed Implementation

[0035] This invention provides a wellbore stabilizer for shallow hydrate-bearing formations in deep water, comprising a copolymer of vinyl lactam monomers and acryloyl dopamine and its derivatives;

[0036] The preparation method of the copolymer of the vinyl lactam monomer and acryloyl dopamine and its derivatives includes the following steps:

[0037] Dopamine and its derivatives are dissolved in a solvent to obtain a solution of dopamine and its derivatives.

[0038] The dopamine and its derivative solution was mixed with triethylchlorosilane, and the resulting reaction solution was reacted. After the reaction was completed, an acrylic acid derivative with an acrylic acid or methacrylic acid group was added to obtain acryloyl dopamine and its derivative.

[0039] Acrylamide and its derivatives are dissolved in a solvent to obtain a solution of acrylamide and its derivatives. The solution of acrylamide and its derivatives, vinyl lactam monomers and initiators are mixed, and the resulting reaction solution is subjected to a polymerization reaction. After the reaction is completed, HCl solution is added to obtain a copolymer of the vinyl lactam monomers and acrylamide and its derivatives.

[0040] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0041] The wellbore stabilizer for shallow hydrate-bearing formations provided by this invention comprises copolymers of vinyl lactam monomers and acryloyl dopamine and its derivatives;

[0042] The preparation method of the copolymer of the vinyl lactam monomer and acryloyl dopamine and its derivatives includes the following steps:

[0043] Dopamine and its derivatives are dissolved in a solvent to obtain a solution of dopamine and its derivatives.

[0044] The dopamine and its derivative solution was mixed with triethylchlorosilane, and the resulting reaction solution was reacted. After the reaction was completed, an acrylic acid derivative with an acrylic acid or methacrylic acid group was added to obtain acryloyl dopamine and its derivative.

[0045] Acrylamide and its derivatives are dissolved in a solvent to obtain a solution of acrylamide and its derivatives. The solution of acrylamide and its derivatives, vinyl lactam monomers and initiators are mixed, and the resulting reaction solution is subjected to a polymerization reaction. After the reaction is completed, HCl solution is added to obtain a copolymer of the vinyl lactam monomers and acrylamide and its derivatives.

[0046] This invention dissolves dopamine and its derivatives in a solvent to obtain a solution of dopamine and its derivatives. The solvent is preferably at least one selected from water, ethanol, N,N-dimethylformamide, and dichloromethane.

[0047] After obtaining a solution of dopamine and its derivatives, the present invention mixes the solution of dopamine and its derivatives with triethylchlorosilane, and reacts the resulting reaction solution. After the reaction is completed, an acrylic acid derivative with an acrylic acid or methacrylic acid group is added to obtain acryloyl dopamine and its derivatives. The acrylic acid derivative with an acrylic acid or methacrylic acid group includes at least one of acryloyl chloride, methacryloyl chloride, acrylic anhydride, and methacrylic anhydride. In the reaction solution, the concentration of dopamine and its derivatives is preferably 0.03 mol / L to 0.15 mol / L, more preferably 0.05 mol / L to 0.12 mol / L, and more preferably 0.06 mol / L to 0.12 mol / L; the concentration of the acrylic acid derivative with an acrylic acid or methacrylic acid group is preferably 0.08 mol / L to 0.40 mol / L; more preferably 0.15 mol / L to 0.28 mol / L; and more preferably 0.14 mol / L to 0.26 mol / L.

[0048] After obtaining acrylamide and its derivatives, the acrylamide and its derivatives are dissolved in a solvent to obtain an acrylamide and its derivative solution. The acrylamide and its derivative solution, vinyl lactam monomers, and initiators are mixed, and the resulting reaction solution is subjected to a polymerization reaction. In the reaction solution, the concentration of vinyl lactam monomers is preferably 0.02~0.12 mol / L, more preferably 0.06~0.10 mol / L; the concentration of initiators is preferably 0.004 mol / L~0.05 mol / L, more preferably 0.006 mol / L~0.02 mol / L. The copolymerization reaction temperature is preferably 70~90℃, more preferably 70~80℃; the time is preferably 6~12 h. After the copolymerization reaction, the present invention preferably further includes: adding HCl solution to the product, and adding the obtained product to an organic solvent for precipitation, followed by filtration and drying to obtain a copolymer of the vinyl lactam monomers and acrylamide and its derivatives. The organic solvent is one or more organic solvents such as diethyl ether, cyclohexane, and ethyl acetate.

[0049] This invention also provides the application of the above-mentioned deep-water shallow hydrate-bearing formation wellbore stabilizer in drilling fluid.

[0050] The preferred content of the wellbore stabilizer in the drilling fluid is 0.5~2.0 wt%.

[0051] The present invention does not impose specific limitations on the formulation and composition of the drilling fluid; those skilled in the art can set it according to actual needs.

[0052] In a specific embodiment of the present invention, when performing performance tests on the wellbore stabilizer for the shallow hydrate-bearing formation in deep water, the solution used is 0.5 wt% treatment agent, with the remainder being water.

[0053] In a specific embodiment of the present invention, when performing performance tests on the wellbore stabilizer for the deep-water shallow hydrate-bearing formation, the preferred drilling fluid formulation is: 2wt% sodium bentonite slurry + 0.1wt% xanthan gum thickener XC + 0.2wt% coating agent + 0.8wt% cellulose filtration reducer + 0.8wt% starch filtration reducer + 5wt% sodium chloride, with the balance being water.

[0054] The following detailed description, in conjunction with embodiments, illustrates the wellbore stabilizer for shallow hydrate-bearing formations provided by this invention and its applications. However, these descriptions should not be construed as limiting the scope of protection of this invention.

[0055] Example 1

[0056] Dopamine hydrochloride was added to dichloromethane to obtain a 0.06 mol / L dopamine hydrochloride solution. The dopamine hydrochloride solution was added to a three-necked flask, and triethylchlorosilane was added at room temperature to react. After the reaction was completed, methacryloyl chloride was added to obtain a reaction solution (the concentration of dopamine hydrochloride in the reaction solution was 0.06 mol / L, the concentration of methacryloyl chloride was 0.14 mol / L, and the concentration of triethylchlorosilane was 0.06 mol / L) and reacted for 4 h to obtain methacryloyldopamine. After the reaction was completed, N-vinylpyrrolidone and azobisisobutyronitrile (the concentration of N-vinylpyrrolidone in the reaction solution was 0.06 mol / L, and the concentration of azobisisobutyronitrile was 0.006 mol / L) were added at 70 °C and reacted for 6 h. HCl solution was added and reacted for 1 h. The resulting reaction product was added to acetone for precipitation, and then filtered and dried to obtain poly(N-vinylpyrrolidone-co-methacryloyldopamine). Poly(N-vinylpyrrolidone-co-methacrylamide) was prepared into a 0.5 wt% aqueous solution using deionized water.

[0057] Example 2

[0058] Dopamine hydrochloride was added to N,N-dimethylformamide to obtain a 0.08 mol / L dopamine hydrochloride solution. This solution was then added to a three-necked flask, and triethylchlorosilane was added at room temperature to initiate the reaction. After the reaction was complete, methacryl chloride was added to obtain a reaction solution (with a dopamine hydrochloride concentration of 0.08 mol / L, a methacryl chloride concentration of 0.18 mol / L, and a triethylchlorosilane concentration of 0.08 mol / L). After 5 hours, methacryloyldopamine was obtained. Following the reaction, N-vinylpyrrolidone and azobisisobutyronitrile (N-vinylpyrrolidone concentration was 0.08 mol / L, and azobisisobutyronitrile concentration was 0.009 mol / L) were added at 72°C and the reaction proceeded for 8 hours. HCl solution was then added, and the reaction continued for 1 hour. The resulting product was precipitated in acetone, filtered, and dried to obtain poly(N-vinylpyrrolidone-co-methacryloyldopamine). A 0.3 wt% aqueous solution of poly(N-vinylpyrrolidone-co-methacryloyldopamine) was prepared using deionized water.

[0059] Example 3

[0060] Dopamine hydrochloride was added to ethanol to obtain a 0.10 mol / L dopamine hydrochloride solution. The dopamine hydrochloride solution was added to a three-necked flask, and triethylchlorosilane was added at room temperature to react. After the reaction was completed, methacrylic anhydride was added to obtain a reaction solution (the concentration of dopamine hydrochloride in the reaction solution was 0.10 mol / L, the concentration of methacrylic anhydride was 0.22 mol / L, and the concentration of triethylchlorosilane was 0.10 mol / L). The reaction was carried out for 5 hours to obtain methacrylamide. After the reaction was complete, N-vinylpyrrolidone, ammonium persulfate, and hydrogen peroxide were added at 75°C (the concentration of N-vinylpyrrolidone in the reaction solution was 0.10 mol / L, and the concentrations of ammonium persulfate and hydrogen peroxide were 0.012 mol / L and 0.012 mol / L, respectively). The reaction was carried out for 10 h, followed by the addition of HCl solution and another 1 h of reaction. The resulting reaction product was then added to acetone for precipitation, followed by filtration and drying to obtain poly(N-vinylpyrrolidone-co-methacryloyldopamine). A 0.8 wt% aqueous solution of poly(N-vinylpyrrolidone-co-methacryloyldopamine) was prepared using deionized water.

[0061] Example 4

[0062] Levodopa was added to water to obtain a 0.12 mol / L levodopa solution. The levodopa solution was added to a three-necked flask, and triethylchlorosilane was added at room temperature to react. After the reaction was completed, acryloyl chloride was added to obtain a reaction solution (the concentration of levodopa in the reaction solution was 0.12 mol / L, the concentration of acryloyl chloride was 0.26 mol / L, and the concentration of triethylchlorosilane was 0.10 mol / L). The reaction was carried out for 6 h to obtain acryloyldopamine. After the reaction was completed, N-vinylcaprolactam, ammonium persulfate, and hydrogen peroxide were added at 80 °C (the concentration of N-vinylcaprolactam in the reaction solution was 0.10 mol / L, and the concentrations of ammonium persulfate and hydrogen peroxide were 0.016 mol / L and 0.016 mol / L, respectively). The reaction was carried out for 10 h, HCl solution was added, and the reaction was carried out for 1 h. The resulting reaction product was added to acetone for precipitation, and then filtered and dried to obtain poly(N-vinylcaprolactam-co-acryloyldopamine). Poly(N-vinylcaprolactam-co-acryloyldopamine) was prepared into a 1.0 wt% aqueous solution using deionized water.

[0063] Example 5

[0064] The preparation method of poly(N-vinylpyrrolidone-co-methacrylamide) is the same as in Example 1. Poly(N-vinylpyrrolidone-co-methacrylamide) is directly added to the drilling fluid at a concentration of 0.5 wt.

[0065] Comparative Example 1

[0066] The existing polyvinylpyrrolidone (PVP) with the function of inhibiting hydrate decomposition was added to the typical deepwater drilling fluid base formulation in Example 5, with a concentration of 0.5 wt%.

[0067] Comparative Example 2

[0068] The existing polyvinyl caprolactam (PVCap), which has the effect of inhibiting hydrate decomposition, is added to the typical deepwater drilling fluid base formulation in Example 5, with a polyvinyl caprolactam concentration of 0.5 wt%.

[0069] Comparative Example 3

[0070] Existing polymeric alcohols with cementing properties are added to deionized water at a concentration of 0.5 wt%.

[0071] Comparative Example 4

[0072] Existing emulsified asphalt with a binding effect is added to deionized water, and the concentration of emulsified asphalt is 0.5 wt%.

[0073] Comparative Example 5

[0074] The existing aluminum humate salt with cementing effect is added to deionized water at a concentration of 0.5 wt%.

[0075] Comparative Example 6

[0076] The existing sodium silicate with a cementing effect is added to deionized water at a concentration of 0.5 wt%.

[0077] Performance Test 1

[0078] The performance of different embodiments in inhibiting hydrate decomposition was evaluated using a drilling fluid hydrate formation and decomposition simulation experimental device independently developed by China University of Petroleum (East China).

[0079] (1) Hydrate formation: Add 250 mg / L sodium dodecyl sulfate solution to the reactor. Turn on the constant temperature water bath and adjust the temperature to 2℃ to cool the liquid to be tested in the reactor. After the temperature stabilizes, inject methane evenly and slowly into the reactor to 12 MPa. Set the stirring speed to 400 r / min and record the changes in temperature and pressure in the reactor in real time during the hydrate formation process until the pressure no longer changes, that is, the hydrate is completely formed.

[0080] (2) Hydrate Decomposition Experiment: After the hydrate is completely formed, adjust the temperature of the constant temperature water bath to the specified temperature. Then, raise the temperature of 180 mL of the test solution to 6°C and inject it into the reaction vessel using a horizontal flow pump. This effectively avoids the pressure rise inside the reaction vessel caused by the injection of external liquid, which could lead to the regeneration of hydrate from the decomposed methane. Record the temperature and pressure changes during the hydrate decomposition process. When the pressure inside the reaction vessel remains constant, it indicates that the hydrate has completely decomposed, and the experiment ends.

[0081] The experimental results are shown in Table 1.

[0082] Table 1. Experimental results evaluating the performance of inhibiting hydrate decomposition.

[0083]

[0084] Table 1 shows that after injecting deionized water, the time for complete hydrate decomposition was 2.20 h. Adding different concentrations of wellbore stabilizers for deep-water shallow hydrate-bearing formations significantly increased the time for complete hydrate decomposition. Compared to deionized water, in Example 1, 0.5 wt% poly(N-vinylpyrrolidone-co-methacryloyldopamine) extended the complete hydrate decomposition time by 31%; in Example 3, 0.8 wt% poly(N-vinylpyrrolidone-co-methacryloyldopamine) extended the complete hydrate decomposition time by 43%; and in Example 4, 1.0 wt% poly(N-vinylcaprolactam-co-methacryloyldopamine) extended the complete hydrate decomposition time by 47%. At the same concentration, the 0.5 wt% poly(N-vinylpyrrolidone-co-methacryloyldopamine) in Example 1 was compared with 0.5 wt% PVP (Comparative Example 1) and 0.5 wt% PVCap (Comparative Example 2), which are currently known to inhibit hydrate formation and decomposition. The results showed that under the action of (N-vinylpyrrolidone-co-methacrylamide) in Example 1, the time for complete hydrate decomposition was similar to that of Comparative Example 1, and 94% of that of Comparative Example 2, indicating that it had good consistency in hydrate decomposition and performance similar to commonly used hydrate decomposition inhibitors. Example 5 involved adding poly(N-vinylpyrrolidone-co-methacrylamide) to drilling fluid used in deep-water oil and gas and natural gas hydrate drilling, which significantly inhibited hydrate decomposition. Furthermore, because the drilling fluid formulation contained xanthan gum thickener, it could increase the viscosity of the drilling fluid to slow down heat and mass transfer; therefore, the effect of inhibiting hydrate decomposition was even more significant after adding wellbore stabilizers to shallow hydrate-bearing formations in deep water.

[0085] Performance Test 2

[0086] The effect of different embodiments on the adhesion force between hydrate particles and the wall surface was evaluated using an experimental apparatus for measuring the interaction force of hydrate particles, which was independently developed by China University of Petroleum (East China).

[0087] (1) Preparation of cyclopentane hydrate: Cyclopentane was added to the hydrate particle preparation experimental platform, and deionized water was solidified into ice particles by liquid nitrogen at the end of the glass fiber; then it was transferred into cyclopentane to convert it into hydrate, and then the cyclopentane was heated to the temperature to be measured.

[0088] (2) Adhesion force test: The electric arm was controlled to bring the hydrate particles into contact with the wall surface, and the initial coordinate Y1 was recorded. After applying pressure to the particles on the fixed arm and holding it for several seconds, the electric arm was moved in the opposite direction until the particles separated when the adhesive force and the elastic force of the glass fiber were balanced. The coordinate Y2 at this point was recorded, and the displacement ΔY was calculated. Based on Hooke's law, combined with ΔY and the elastic coefficient of the glass fiber in the fixed arm, the adhesive force was calculated. Each experiment was repeated 40 times with the "contact-pressure-movement-separation" operation to avoid errors and ensure data accuracy.

[0089] The experimental results are shown in Table 2.

[0090] Table 2. Experimental results of adhesion test between hydrate particles and wall surface

[0091]

[0092] Table 2 shows that, when different wall surfaces are wetted with deionized water, the adhesion forces between hydrate particles and quartz, mica, and formation simulation samples under the action of liquid bridging are 24.83 mN·m. -1 27.61 mN·m -1 and 26.73 mN·m -1 Compared to deionized water, in Example 1, 0.5 wt% poly(N-vinylpyrrolidone-co-methacryloyldopamine) increased the adhesion of hydrate particles to different wall surfaces to 34.85 mN·m. -1 46.27 mN·m -1 and 47.45 mN·m -1 Compared to deionized water, the concentrations were increased by 40.4%, 67.6%, and 77.5%. At the same concentration, 0.5 wt% of poly(N-vinylpyrrolidone-co-methacryloyldopamine) from Example 1 was compared with 0.5 wt% of polyol (Comparative Example 3), 0.5 wt% emulsified bitumen (Comparative Example 4), 0.5 wt% aluminum humate (Comparative Example 5), and 0.5 wt% sodium silicate (Comparative Example 6), which are known to have cementing and wall-strengthening effects. The results showed that, under the action of poly(N-vinylpyrrolidone-co-methacrylamide) in Example 1, the adhesion force between hydrate and quartz was 2.39 times, 1.49 times, 1.61 times, and 1.45 times that of Comparative Examples 3, 4, 5, and 6, respectively; the adhesion force between hydrate and mica was 2.18 times, 2.03 times, 1.52 times, and 1.97 times that of Comparative Examples 3, 4, 5, and 6, respectively; and the adhesion force between hydrate and formation simulation samples was 1.86 times, 1.67 times, 1.43 times, and 1.51 times that of Comparative Examples 3, 4, 5, and 6, respectively. This indicates that the (N-vinylpyrrolidone-co-methacrylamide) of the present invention has excellent cementing properties for hydrate particles and formation minerals.

[0093] Performance Test 3

[0094] The effect of different embodiments on the bonding properties of the specimens was evaluated by lap shear test.

[0095] The treatment agent was evenly applied to the lap joint surface of the specimen and cured in water and air at 2°C for 24 hours respectively. After curing, the specimen was pulled apart at a constant test speed, and the maximum load was recorded as the failure load to evaluate the lap shear strength of different treatment agents.

[0096] The experimental results are shown in Table 3.

[0097] Table 3. Results of lap joint shear strength test

[0098]

[0099] As shown in Table 3, in Example 1, the overlap strength of the lapped sample under the action of 0.5 wt% poly(N-vinylpyrrolidone-co-methacrylamide) was 0.416 MPa in air and 0.224 MPa in water; in Example 2, the overlap strength of the lapped sample under the action of 0.3 wt% poly(N-vinylpyrrolidone-co-methacrylamide) was 0.298 MPa in air and 0.18 MPa in water. 7 MPa; In Example 3, the overlap strength of the lapped sample under the action of 0.8 wt% poly(N-vinylpyrrolidone-co-methacrylamide) was 0.477 MPa in air and 0.306 MPa in water; In Example 4, the overlap strength of the lapped sample under the action of 1.0 wt% poly(N-vinylcaprolactam-co-methacrylamide) was 0.528 MPa in air and 0.376 MPa in water. At the same concentration, 0.5 wt% poly(N-vinylpyrrolidone-co-methacrylamide) of Example 1 was compared with 0.5 wt% polyol (Comparative Example 3), 0.5 wt% emulsified bitumen (Comparative Example 4), 0.5 wt% aluminum humate (Comparative Example 5), and 0.5 wt% sodium silicate (Comparative Example 6), which are currently known to have a cementing and wall-strengthening effect. The results show that the lap shear strength of Comparative Examples 3 and 4 in water drops to 0; the lap shear strength in air under the action of Example 1 is 1.02 times and 1.02 times that of Comparative Examples 5 and 6, respectively, and the lap shear strength in water is 1.91 times and 12.4 times that of Comparative Examples 5 and 6, respectively. This indicates that the wellbore stabilizer for deep-water shallow hydrate-bearing formations of the present invention has excellent cementing properties for formation minerals.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A wellbore stabilizer for shallow hydrate-bearing formations in deep water, characterized in that, The structure is as follows: ； Ⅰ Among them, the monomer containing the ortho-phenolic hydroxyl structure has the following structure, formula II: ； Ⅱ Where R1 is an acryloyloxy or methacryloxy, and its structure is as follows: Formula III: 、 ； Ⅲ R2 has the same structure as R1, either –H or –CH3; The structure of R3 is as follows: (Form IV) 、 、 ； Ⅳ R4 is pyrrolidone or caprolactam, with the following formula V; 、 ； Ⅴ。 2. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water as described in claim 1, characterized in that, Includes the following steps: (1) Dissolve dopamine and its derivatives in a solvent and adjust the solution to alkaline to obtain a solution of dopamine and its derivatives; (2) The dopamine and its derivative solution is mixed with triethylchlorosilane and reacted. After the reaction is completed, an acrylic acid derivative with an acrylic acid or methacrylic acid group is added to obtain acryloyl dopamine and its derivative. (3) Dissolve the acryloyldopamine and its derivatives in a solvent to obtain a solution of acryloyldopamine and its derivatives; (4) Mix acryloyl dopamine and its derivative solutions, vinyl lactam monomers and initiators to carry out polymerization reaction. After the reaction is completed, add HCl solution to deprotect the product, add organic solvent to precipitate by-products or extract the product.

3. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 2, characterized in that, Step (1) is carried out under stirring and nitrogen protection conditions.

4. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 2, characterized in that, In step (1), the dopamine and its derivatives are dopamine hydrochloride, levodopa, norepinephrine or methyldopamine; The solvent is at least one of water, ethanol, N,N-dimethylformamide, and dichloromethane.

5. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 2, characterized in that, In step (2), the number of moles of triethylchlorosilane is 2 to 3 times the number of moles of dopamine and its derivatives, and the reaction is kept at 30°C.

6. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 2, characterized in that, In step (2), the acrylic acid derivative with an acrylic acid or methacrylic acid group is at least one of acryloyl chloride, methacryloyl chloride, acrylic anhydride and methacrylic anhydride; The molar number of acrylic acid derivatives with acrylic acid or methacrylic acid groups is 1.2 to 2 times that of dopamine and its derivatives, and the reaction is carried out at 45°C.

7. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 2, characterized in that, In step (3), the solvent is at least one of water, ethanol, and N,N-dimethylformamide.

8. The method for preparing a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 2, characterized in that, In step (4), the vinyl lactam monomer is at least one of N-vinylpyrrolidone and N-vinylcaprolactam; The initiator is one or more of azobisisobutyronitrile, ammonium persulfate, and hydrogen peroxide; The copolymerization reaction of the polymerization reaction is carried out at a temperature of 70~90℃ for a time of 6~12h; The organic solvent is one or more of diethyl ether, cyclohexane, and ethyl acetate.

9. The application of the wellbore stabilizer for shallow hydrate-bearing formations in deep water as described in claim 1, characterized in that, As a raw material in the preparation of drilling fluid.

10. The application of a wellbore stabilizer for shallow hydrate-bearing formations in deep water according to claim 9, characterized in that, The wellbore stabilizer for shallow hydrate-bearing formations in deep water has a content of 0.5% to 2.0 wt% in the drilling fluid.

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