A polymer well wall protective agent and its preparation method

Abstract

The present invention provides a polymer well wall protective agent and a preparation method thereof, relating to the field of oilfield drilling technology. The polymer well wall protective agent of the present invention is obtained by copolymerization of a vinyl monomer, a silane coupling agent, and an anionic and nonionic composite surfactant under the action of a water-soluble initiator. The polymer well wall protective agent of the present invention can interact with the mineral salts on the surface of sodium bentonite to form a network structure, which wraps the sodium bentonite, prevents the clay from dispersing, and seals the gaps in the formation, thereby maintaining the stability of the well wall and effectively protecting the reservoir. The polymer well wall protective agent of the present invention has excellent stability and good temperature and pressure resistance during use.

Description

Technical Field

[0001] The invention provides a polymer well wall protective agent and a preparation method thereof, belonging to the technical field of petroleum drilling. Background Art

[0002] With the growing global demand for oil and gas resources, oil and gas drilling operations have significantly expanded in both geographic scope and depth. This results in the frequent encounter of complex and variable formation conditions during drilling, such as soft formations, salt formations, easily collapsed formations, and high-pressure zones. To meet the drilling demands of these extreme conditions, advances in drilling fluid technology are crucial, and this relies heavily on the development of new drilling fluid treatment agents. Wellbore instability can lead to complex conditions such as well collapse and lost circulation, seriously impacting drilling efficiency and safety and increasing drilling costs. To maintain wellbore stability, wellbore protectants are often added to the drilling fluid. Wellbore protectants enhance wellbore stability by forming a protective film on the wellbore.

[0003] Existing wellbore protection agents are mainly composed of various polymers (such as polyacrylamide, polyvinyl alcohol, etc.) and chemical additives (such as salts, alcohols, silicates, etc.). These protection agents can provide a certain wellbore stabilization effect under conventional formation conditions. However, under certain conditions, existing wellbore protection agents have the following problems and limitations: insufficient stability and poor temperature and pressure resistance. Some wellbore protection agents may pollute the environment, have high costs, and have insufficient overall performance. Therefore, the development of a wellbore protection agent with better performance to adapt to complex and changing geological conditions and environmental protection requirements has become a technical problem that needs to be urgently solved in the current oil and gas drilling field. Summary of the Invention

[0004] In view of this, the present invention aims to provide a polymeric well wall protective agent and a method for preparing the same. The polymeric well wall protective agent is obtained by copolymerizing a vinyl monomer, a silane coupling agent, and an anionic / nonionic composite surfactant in the presence of a water-soluble initiator. The polymeric well wall protective agent exhibits excellent stability and resistance to heat and pressure during use.

[0005] The technical solution adopted in the present invention is:

[0006] A method for preparing a polymer well wall protective agent comprises the following steps:

[0007] (1) Preparation of a monomer mixture: Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and a silane coupling agent are uniformly mixed at 30-40° C. to obtain 100 parts by weight of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and silane coupling agent is (45-60):(15-25):(5-10):(1-2):(2-8);

[0008] (2) Preparation of an initiator aqueous solution: Weigh 0.5 to 1 parts by weight of a water-soluble initiator, mix the water-soluble initiator with water, and prepare an initiator aqueous solution with a mass fraction of 1%;

[0009] (3) Preparation of anionic and nonionic compound surfactant solution: add 80 to 100 parts by weight of water to a reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of (1 to 2): (0.3 to 1): (0.2 to 1) respectively under stirring, stir evenly to obtain an anionic and nonionic compound surfactant solution with a mass fraction of 5% to 10%;

[0010] (4) Preparation of seed emulsion: 20-30 parts by weight of the monomer mixture in step (1) are added dropwise to the reaction flask in step (3), and stirred evenly in a constant temperature water bath at 60-80°C; 20%-30% of the initiator aqueous solution is weighed and slowly added dropwise to the reaction flask, and the addition is controlled to be completed within 20-30 minutes. After the addition is completed, stirring is continued for 20-30 minutes to obtain the seed emulsion;

[0011] (5) Preparation of a polymer well wall protective agent: Maintain a constant temperature water bath at 60-80°C, dropwise add the remaining monomer mixture from step (1) to the seed emulsion from step (4), and control the addition to be completed within 40-60 minutes. Simultaneously, dropwise add the remaining initiator solution from step (2), and control the addition to be completed within 60-70 minutes. After the addition is completed, continue to keep the reaction in a constant temperature water bath at 60-80°C for 20-40 minutes, and cool to room temperature to obtain a polymer well wall protective agent.

[0012] Preferably, the silane coupling agent in step (1) is γ-methacryloxypropyltrimethoxysilane.

[0013] Preferably, the water-soluble initiator in step (2) is one of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride.

[0014] Compared with the prior art, the present invention has the following technical effects:

[0015] 1) High efficiency and stability: This type of polymer well wall protective agent can form a tough protective film on the well wall, significantly improving the stability of the well wall under complex geological conditions and effectively preventing drilling accidents such as well collapse and lost circulation.

[0016] 2) Good temperature and pressure resistance: This type of polymer well wall protective agent is adaptable to ultra-high temperature and ultra-high pressure formation environments, and can maintain its performance without degradation under extreme conditions, ensuring the safety and efficiency of drilling operations.

[0017] 3) Wide adaptability: This polymer wellbore protective agent is suitable for various types of drilling fluid systems and is not restricted by drilling fluid type and formulation, which enhances its application range in different drilling operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a particle size distribution diagram of the polymer well wall protective agent prepared in Example 1 of the present invention;

[0019] Figure 2 This is an infrared spectrum of the polymer well wall protective agent prepared in Example 1 of the present invention;

[0020] Figure 3 This is a photo of the sodium bentonite agglomeration after being soaked in an aqueous solution of a polymer well wall protective agent prepared in Example 1 of the present invention and centrifuged;

[0021] Figure 4 This is a scanning electron microscope photo of sodium bentonite after drying;

[0022] Figure 5 This is a scanning electron microscope photograph of sodium bentonite after being soaked in the polymer well wall protective agent solution prepared in Example 1 of the present invention, centrifuged, agglomerated, and dried. DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions and advantages of the present invention more clear, the preferred embodiments of the present invention are further described in detail below with reference to the examples. Based on the examples in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:20:10:1:6;

[0026] (2) Take 0.5 g of azobisisobutylamidine hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0027] (3) Add 100g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1:0.5:0.3 with stirring, and stir evenly to obtain a 10% mass fraction of anionic and nonionic composite surfactant solution; weigh 20g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 80°C; then slowly drip 20% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 20min, and continue stirring for 20min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be added dripping to be completed within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be added dripping to be completed within 60-70min. After all the additions were completed, the reaction was continued at 80° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0028] Example 2

[0029] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:20:10:1:6;

[0030] (2) Take 0.5 g of azobisisobutylamidine hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0031] (3) Add 100g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:0.5:0.3 with stirring, and stir evenly to obtain a 10% mass fraction of anionic and nonionic composite surfactant solution; weigh 20g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 80°C; then slowly drip 20% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 20min, and continue stirring for 20min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the reaction was continued at 80° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0032] Example 3

[0033] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:20:10:1:6;

[0034] (2) Take 0.5 g of azobisisobutylamidine hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0035] (3) Add 100g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 2:0.5:0.3 with stirring, and stir evenly to obtain a 10% mass fraction of anionic and nonionic composite surfactant solution; weigh 20g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 80°C; then slowly drip 20% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 20min, and continue stirring for 20min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be added dripping to be completed within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be added dripping to be completed within 60-70min. After all the additions were completed, the reaction was continued at 80° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0036] Example 4

[0037] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 55:15:5:1.5:5;

[0038] (2) Take 1g of azobisisobutylamidine hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0039] (3) Add 80g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:0.5:0.5 with stirring, and stir evenly to obtain an anionic and nonionic composite surfactant solution with a mass fraction of 8%; weigh 25g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 70°C; then slowly drip 25% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 25min, and continue stirring for 25min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the mixture was kept warm (70° C.) and reacted for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0040] Example 5

[0041] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 45:25:5:1.5:2;

[0042] (2) Take 1g of azobisisobutylamidine hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0043] (3) Add 80g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:0.5:0.8 with stirring, stir evenly, and obtain an anionic and nonionic composite surfactant solution with a mass fraction of 8%; weigh 25g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 70°C; then slowly drip 25% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 25min, and continue stirring for 25min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the mixture was kept warm (70° C.) and reacted for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0044] Example 6

[0045] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 60:15:8:1.5:4;

[0046] (2) Take 1g of azobisisobutylamidine hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0047] (3) Add 80g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:0.5:1 under stirring, stir evenly, and obtain an anionic and nonionic composite surfactant solution with a mass fraction of 8%; weigh 25g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 70°C; then slowly drip 25% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 25min, and continue stirring for 25min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the mixture was kept warm (70° C.) and reacted for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0048] Example 7

[0049] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 30° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:20:5:2:5;

[0050] (2) Take 0.5 g of azobisisobutylimidazoline hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0051] (3) Add 80g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:0.8:0.8 under stirring, stir evenly, and obtain a 5% mass fraction of anionic and nonionic composite surfactant solution; weigh 20g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 60°C; then slowly drip 20% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 20min, and continue stirring for 20min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be added dripping to be completed within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be added dripping to be completed within 60-70min. After all the additions were completed, the reaction was continued at 60° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0052] Example 8

[0053] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 40° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:25:5:2:5;

[0054] (2) Take 0.5 g of azobisisobutylimidazoline hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0055] (3) Add 80g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:1:0.8 with stirring, stir evenly, and obtain a 5% mass fraction of anionic and nonionic composite surfactant solution; weigh 25g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 60°C; then slowly drip 25% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 25min, and continue stirring for 25min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the reaction was continued at 60° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0056] Example 9

[0057] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 40° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:25:5:2:8;

[0058] (2) Take 0.5 g of azobisisobutylimidazoline hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0059] (3) Add 80g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 1.5:1:1 under stirring, stir evenly, and obtain a 5% mass fraction of anionic and nonionic composite surfactant solution; weigh 30g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 60°C; then slowly drip 30% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 30min, and continue stirring for 30min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the reaction was continued at 60° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0060] Example 10

[0061] (1) Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane were mixed uniformly at 40° C. to obtain 100 g of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and γ-methacryloxypropyltrimethoxysilane was 50:25:5:1.5:8;

[0062] (2) Take 0.5 g of azobisisobutylimidazoline hydrochloride and add water to prepare a 1% initiator aqueous solution;

[0063] (3) Add 90g of water to the reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of 2:1:1 with stirring, stir evenly, and obtain a 5% mass fraction of anionic and nonionic composite surfactant solution; weigh 30g of the monomer mixture described in step (1), slowly drip it into the reaction flask with a constant pressure dropping funnel, and stir evenly in a constant temperature water bath at 60°C; then slowly drip 30% of the initiator aqueous solution prepared in step (2), control the dripping to be completed within 30min, and continue stirring for 30min; pour the remaining monomer mixture in step (1) into the constant pressure dropping funnel, control the monomer mixture to be dripped within 40-60min, and at the same time drip the remaining initiator solution in step (2), control the initiator aqueous solution to be dripped within 60-70min. After all the additions were completed, the reaction was continued at 60° C. for 30 minutes. The obtained product was cooled to room temperature to obtain a polymer well wall protective agent.

[0064] Comparative Example 1

[0065] Refer to Example 1, except that no methyl methacrylate is added.

[0066] Comparative Example 2

[0067] Refer to Example 1, except that no vinyl acetate is added.

[0068] Comparative Example 3

[0069] Refer to Example 1, except that pentaerythritol triacrylate is not added.

[0070] Comparative Example 4

[0071] Refer to Example 1, except that γ-methacryloxypropyltrimethoxysilane is not added.

[0072] Comparative Example 5

[0073] Refer to Example 1, except that no acrylamide is added.

[0074] Comparative Example 6

[0075] Refer to Example 1, the only difference is that the concentration of the anionic and nonionic composite surfactant solution is adjusted to 3%.

[0076] Comparative Example 7

[0077] Refer to Example 1, the only difference is that the concentration of the anionic and nonionic composite surfactant solution is adjusted to 12%.

[0078] Performance Testing

[0079] 1. Particle size test

[0080] The polymer well wall protective agent prepared in Example 1 was diluted with deionized water to a mass concentration of 0.1%, and after ultrasonic dispersion treatment for 30 minutes, the particle size was measured using a British Malvern Zetasizer Nano ZS laser scattering particle size analyzer at a test temperature of 25°C. The particle size test results are shown in Figure 1 .

[0081] Depend on Figure 1 It can be seen that the particle size of the polymer well wall protective agent prepared in Example 1 of the present invention presents a unimodal distribution, the particle size distribution range is narrow, the polydispersity coefficient is 0.221, and the particle size is 87.17 nm, indicating that the polymer well wall protective agent prepared by emulsion polymerization has high stability.

[0082] 2. Infrared test

[0083] The polymer well wall protective agent prepared in Example 1 was purified, dried, and ground into powder. The infrared structure was tested using a VECTOR-22 Fourier transform infrared spectrometer from Bruker, Germany, using the potassium bromide tablet method with a scanning range of 4000-500 cm -1 , resolution 4cm -1 . Infrared test results see Figure 2 .

[0084] Depend on Figure 2 It can be seen that 3226.83cm -1 The amino stretching vibration absorption peak is at 2933.37 cm -1 The absorption peak of C=O in the product is generally at 1720cm -1 Therefore, 1726.24cm -1 The characteristic bending vibration peaks around 1440.79 cm are determined to be the absorption peaks of C=O; -1 -CH2 bending vibration absorption peak; 1188.72cm -1 、1137.92cm -1 The C—O—C vibration absorption peak indicates the successful introduction of the ester group; -1 The Si-O-Si stretching vibration absorption peak is at 846.72 cm -1 The bending vibration absorption peak of Si-O is at 1675~1640cm -1 No characteristic absorption peaks of C=C stretching vibration were observed, indicating that there was no unreacted vinyl monomer in the sample and no residual monomer in the polymer product. The results show that the prepared polymer well wall protection agent contains the characteristic functional groups of various monomers in the molecular structure design.

[0085] 3. Application performance testing

[0086] The polymer well wall protective agent prepared in Examples 1 to 10 was tested for its application performance according to the following steps:

[0087] (1) The stability of the polymer well wall protective agent emulsions prepared in Examples 1 to 10 was determined using a centrifuge. The specific method was as follows: 10 mL of the polymer well wall protective agent emulsions prepared in Examples 1 to 10 were respectively transferred into 10 mL centrifuge tubes, placed in a centrifuge, and centrifuged at a speed of 1500 r / min for 15 min. The centrifuge was stopped and the emulsions were taken out. The state of the emulsions was observed, and it was recorded whether the emulsions had precipitation or stratification.

[0088] (2) Accurately weigh 2 g of the centrifuged polymer well wall protective agent emulsion (1) in a dry and clean 250 mL beaker, add 98 mL of accurately measured deionized water, and stir evenly with a glass for later use.

[0089] (3) Weigh 10 g of sodium bentonite and place it in an electric constant temperature drying oven at 105°C ± 1°C for 6 h. Then take it out and place it in a desiccator to cool to room temperature for use.

[0090] (4) Pipette 5 mL of the aqueous solution of the polymer well wall protective agent prepared in (2) into a 10 mL centrifuge tube, weigh 0.5 g of the sodium bentonite in (3), put it into the centrifuge tube, then add 5 mL of the polymer well wall protective agent solution prepared in (2), shake well, store at room temperature for 2 h, put it into a centrifuge, centrifuge at a speed of 1500 r / min for 15 min, stop the machine and take it out to observe whether the sodium bentonite in the centrifuge tube is agglomerated.

[0091] Figure 3 This is a photo of the sodium bentonite agglomeration after being soaked in the aqueous solution of the polymer well wall protective agent prepared in Example 1 of the present invention and centrifuged. Figure 3 It can be seen that after being soaked in the aqueous solution of the polymer well wall protective agent, the polymer well wall protective agent can interact with the mineral salts on the surface of the sodium bentonite, wrap the sodium bentonite, and then prevent the clay from dispersing, seal the formation gaps, thereby maintaining the stability of the well wall and effectively protecting the reservoir.

[0092] The comparative example application performance test method is the same as above, observing the stability of the comparative example emulsion and whether the sodium bentonite in the centrifuge tube is agglomerated. The emulsion state after centrifugation of the embodiment and the comparative example and the agglomeration of the sodium bentonite are shown in Table 1.

[0093] Table 1

[0094] Example Emulsion state Sodium bentonite situation Comparative Example Emulsion state Sodium bentonite situation Example 1 Stable emulsion into a cohesive mass Comparative Example 1 Stable emulsion relatively loose Example 2 Stable emulsion into a cohesive mass Comparative Example 2 Stable emulsion relatively loose Example 3 Stable emulsion into a cohesive mass Comparative Example 3 Stable emulsion relatively loose Example 4 Stable emulsion into a cohesive mass Comparative Example 4 Stable emulsion relatively loose Example 5 Stable emulsion into a cohesive mass Comparative Example 5 Stable emulsion relatively loose Example 6 Stable emulsion into a cohesive mass Comparative Example 6 Emulsion is unstable and stratifies Unable to test Example 7 Stable emulsion into a cohesive mass Comparative Example 7 Stable emulsion Relatively loose, slightly clumped Example 8 Stable emulsion into a cohesive mass Example 9 Stable emulsion into a cohesive mass Example 10 Stable emulsion into a cohesive mass

[0095] As shown in Table 1, the polymer wellbore protective agent emulsion prepared in this application remains stable after centrifugation, exhibiting no delamination or precipitation. It is easy to store for a long time, exhibits a long shelf life, and can form aggregates of sodium bentonite. This is because the polymer wellbore protective agent prepared in this application comprises a polymer with a network-like crosslinked structure. Its raw material components include pentaerythritol triacrylate, a polymerizable crosslinking monomer that forms a network-like crosslinked structure; methyl methacrylate and γ-methacryloxypropyltrimethoxysilane are hard monomers. Their combination imparts rigid segments to the polymer molecule, resulting in sufficient strength and mechanical properties. Furthermore, the amide and ester groups, respectively, provided by acrylamide and vinyl acetate in the polymer structure can form hydrogen bonds with the mineral salts on the surface of the sodium bentonite. These hydrogen bonds form a network structure that encapsulates the sodium bentonite. Therefore, the polymer prepared in this application can prevent clay from dispersing, seal interstices in the formation, and thus maintain wellbore stability and effectively protect the reservoir. Comparative Examples 1 to 5, which adjusted the composition, failed to cause the sodium bentonite to agglomerate, meaning they were unable to maintain wellbore stability. Comparative Example 6, after reducing the ratio of the anionic and nonionic surfactants, failed to form a stable emulsion. Comparative Example 7, after increasing the ratio of the anionic and nonionic surfactants, although a relatively stable polymer emulsion was formed, the increased amount of surfactant resulted in poor water-resistant properties after the polymer film formed. Consequently, the sodium bentonite could not effectively form a film, and thus, wellbore stability could not be maintained.

[0096] 4. Scanning electron microscope test

[0097] (1) Weigh 10 g of sodium bentonite and place it in an electric constant temperature drying oven at 105°C ± 1°C for 6 h. Then take it out and place it in a desiccator to cool to room temperature for use.

[0098] (2) According to the test method of 3. Application performance, the polymer well wall protective agent prepared in Example 1 was soaked in sodium bentonite, centrifuged, and agglomerated, and then kept at a constant temperature of 105°C ± 1°C for 6 hours, taken out and placed in a desiccator to cool to room temperature for use.

[0099] (3) The micromorphology of sodium bentonite (1) and (2) was observed using a Japanese IT700HR non-leakage magnetic thermal field emission scanning electron microscope. The scanning electron microscope photos are shown in Figure 4 and Figure 5 .

[0100] Figure 4 This is a scanning electron microscope photo of sodium bentonite (magnification 500). Figure 5This is a scanning electron microscope photograph (magnification 500) of sodium bentonite after being soaked in the aqueous solution of the polymer well wall protectant and centrifuged to form agglomerates. It can be clearly seen that before soaking in the aqueous solution of the polymer well wall protectant, the sodium bentonite was granular, with no other material between the particles. After soaking in the aqueous solution, the polymer well wall protectant formed a dense film on the surface of the sodium bentonite, which almost completely covered the sodium bentonite particles. This indicates that the polymer well wall protectant prepared in this application has excellent film-forming properties, thereby maintaining well wall stability and effectively protecting the reservoir.

[0101] The embodiments described above are some embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer well wall protective agent, characterized in that: The following steps are involved: (1) Preparation of a monomer mixture: Methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and a silane coupling agent are uniformly mixed at 30-40° C. to obtain 100 parts by weight of a monomer mixture; wherein the mass ratio of methyl methacrylate, vinyl acetate, acrylamide, pentaerythritol triacrylate, and silane coupling agent is (45-60):(15-25):(5-10):(1-2):(2-8); the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; (2) Preparation of initiator aqueous solution: Weigh 0.5 to 1 parts by weight of a water-soluble initiator, mix the water-soluble initiator with water to form an initiator aqueous solution with a mass fraction of 1%; (3) Preparation of anionic and nonionic compound surfactant solution: add 80-100 parts by weight of water to a reaction flask, add sodium salt of alkylphenol ether sulfosuccinate, octylphenol polyoxyethylene ether-10 and allyloxy nonylphenol propanol polyoxyethylene (10) ether ammonium sulfate in a mass ratio of (1-2): (0.3-1): (0.2-1) respectively while stirring, stir evenly to obtain an anionic and nonionic compound surfactant solution with a mass fraction of 5%-10%; (4) Preparation of seed emulsion: 20-30 parts by weight of the monomer mixture in step (1) are added dropwise to the reaction flask in step (3), and stirred evenly in a constant temperature water bath at 60-80°C; 20%-30% of the initiator aqueous solution is weighed and slowly added dropwise to the reaction flask, and the addition is controlled to be completed within 20-30 minutes. After the addition is completed, stirring is continued for 20-30 minutes to obtain the seed emulsion; (5) Preparation of polymer well wall protective agent: maintain a constant temperature water bath at 60-80°C, add the remaining monomer mixture of step (1) to the seed emulsion of step (4), and control the addition to be completed within 40-60 minutes. At the same time, add the remaining initiator solution of step (2), and control the addition to be completed within 60-70 minutes. After the addition is completed, continue to keep the reaction in a constant temperature water bath at 60-80°C for 20-40 minutes, and cool to room temperature to obtain the polymer well wall protective agent.

2. The method for preparing a polymer well wall protective agent according to claim 1, wherein: The water-soluble initiator in step (2) is one of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride.

3. A polymer well wall protective agent, characterized in that: Prepared by any one of the methods of claims 1 to 2.

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