A 200-degree-celsius salt-resistant temperature-responsive wall-cementing agent for water-based drilling fluid and a preparation method and application thereof

Abstract

The application provides a 200 DEG C salt-resistant temperature-responsive cementing solid wall agent for water-based drilling fluid and a preparation method and application thereof, and belongs to the technical field of drilling.The preparation method of the cementing solid wall agent comprises the following steps: adding gum arabic and an emulsifier into deionized water, stirring uniformly to obtain an aqueous phase; dissolving acrylic resin and polymethyl methacrylate in dichloromethane to obtain an oil phase; adding the obtained oil phase into the obtained aqueous phase, performing shearing emulsification to obtain an oil-in-water emulsion; removing organic solvents in the emulsion by warming evaporation to obtain a mixed liquid; adding tetraethyl silicate dropwise into the mixed liquid, stirring uniformly, then adding 3-aminopropyl triethoxysilane dropwise into the system and performing reaction; after the reaction is completed, filtration, washing and drying are performed to obtain the cementing solid wall agent.The temperature-responsive cementing solid wall agent adopts an organic inner shell layer and an inorganic rigid material as an outer shell layer, has temperature response characteristics and can quickly respond to complex downhole environmental conditions.

Description

Technical Field

[0001] This invention relates to a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent, its preparation method and application, belonging to the field of drilling technology. Background Technology

[0002] Wellbore instability is the most common and typical complex downhole situation. Its core is the disruption of the original mechanical balance of the formation, leading to instability phenomena such as cracking, collapse, or narrowing of the wellbore rock. This can result in serious consequences such as stuck pipe, lost circulation, and wellbore abandonment. Currently, the mechanisms of action of commonly used wellbore stabilizing materials can be mainly divided into three categories: The first is the hydration inhibition mechanism, which delays water molecule penetration into the formation by forming an adsorption film on the wellbore or adjusting the drilling fluid ion environment, inhibiting the hydration expansion and dispersion of clay minerals, and preventing wellbore spalling and collapse. The second is the pore sealing mechanism, which fills formation pores and microfractures with sealing materials of specific particle sizes, forming a dense, low-permeability barrier, reducing drilling fluid intrusion, mitigating formation pore pressure changes, and preventing pressure imbalance leading to wellbore instability. The third is the cementation strengthening mechanism, where the treatment agent in the material enhances the cementation force between mineral particles through chemical reaction or physical adsorption with rock minerals, allowing clay minerals to maintain structural integrity even after long-term immersion, thus improving wellbore strength and stability.

[0003] Currently, cementation and wall-stabilizing technology for water-based drilling fluids is still in its early stages. For example, Chinese patent document CN115057967A discloses a microgel-type wall-stabilizing agent synthesized using a reverse emulsion polymerization method. This wall-stabilizing agent has a particle size distribution of 8-50 micrometers. Under the action of formation bottom-hole pressure differential, it can both physically seal the micrometer-scale pores and fractures of the rock and achieve interfacial cementation by forming hydrogen bonds with the rock, maintaining wellbore stability with its strong cementation strength. Chinese patent document CN106634884A prepares a biomimetic wall-stabilizing agent through the free radical polymerization reaction of polyphenolic protein, acrylamide, and dimethyl diallyl ammonium chloride. Its core function is to enhance the compressive strength of the rock core, thereby achieving wellbore stability. Its design concept draws on biomimetic principles to improve the compatibility and effectiveness of the material with the rock. However, existing preparation processes mostly rely on free radical polymerization reactions as the core pathway, which has revealed many problems that urgently need to be solved in practical applications: First, the bonding effect is poor, making it difficult to form a uniform and high-strength bonding layer, resulting in limited wellbore reinforcement; Second, the adaptability to deep formations is poor. When facing complex formation environments such as high temperature, high pressure, and high salinity, the binder is prone to performance degradation and cannot meet the needs of deep drilling; Third, the compatibility with water-based drilling fluids is insufficient, which can easily lead to abnormal rheological properties of the drilling fluid, such as thickening, foaming, and sedimentation, interfering with normal drilling operations.

[0004] In summary, developing high-temperature and high-salt resistant cemented wellbore consolidation materials to effectively address wellbore instability in deep and complex formations has become an urgent priority for advancing wellbore stabilization technology. Therefore, this invention is proposed. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, this invention provides a 200℃-resistant, salt-resistant temperature-responsive cementing and wall-stabilizing agent for water-based drilling fluids, along with its preparation method and applications. This temperature-responsive cementing and wall-stabilizing agent encapsulates strong cementing acrylic resin within tiny particles, ensuring the stability of the effective cementing components while achieving precise response and efficient action to the wellbore environment. The inorganic material of the outer shell of the particles resists mechanical erosion and chemical corrosion during drilling fluid circulation, preventing premature leakage or degradation of the acrylic resin. The organic material of the inner shell has a temperature-responsive structure; as the formation temperature rises, the inner wall swells, releasing the acrylic resin core material. The resin core material, with its excellent fluidity and permeability, can quickly penetrate into the pores and micro-cracks of the rock, forming a cementing layer through self-crosslinking. It can also form hydrogen bonds or chemical bonds with active sites such as hydroxyl groups and calcium ions on the rock surface. Simultaneously, the residual structure of the double shell can further assist in sealing micro-cracks, further strengthening the cementing strength and stability of the wellbore, avoiding wall-stabilizing failure caused by inaccurate response or insufficient protection of a single shell.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent includes the following steps:

[0008] (1) Add gum arabic and emulsifier to deionized water and stir until homogeneous to obtain an aqueous phase;

[0009] (2) Dissolve acrylic resin and polymethyl methacrylate in dichloromethane to obtain an oil phase;

[0010] (3) Add the oil phase obtained in step (2) to the aqueous phase obtained in step (1) and perform shear emulsification to obtain an oil-in-water emulsion; heat up and evaporate to remove the organic solvent in the emulsion to obtain a mixture;

[0011] (4) Add tetraethyl silicate (TEOS) dropwise to the mixture and stir evenly. Then add 3-aminopropyltriethoxysilane dropwise to the system and react. After the reaction is completed, filter, wash and dry to obtain a water-based drilling fluid 200℃ salt temperature responsive cementing wall agent.

[0012] According to a preferred embodiment of the present invention, the mass ratio of gum arabic to water in step (1) is 0.03-0.1:1, more preferably 0.04-0.06:1; the molecular weight of gum arabic is not specifically limited, and any molecular weight commonly used in the art is acceptable, such as the relative molecular mass of gum arabic being 100,000-250,000.

[0013] According to a preferred embodiment of the present invention, the emulsifier in step (1) is sodium dodecyl sulfonate, and the mass ratio of the emulsifier to deionized water is 0.0005-0.01:1, more preferably 0.001-0.008:1.

[0014] According to a preferred embodiment of the present invention, the acrylic resin in step (2) is a thermosetting acrylic resin, and the number average molecular weight of the acrylic resin is 10,000-20,000.

[0015] According to a preferred embodiment of the present invention, the polymethyl methacrylate in step (2) has a weight-average molecular weight of 800,000-1,200,000.

[0016] According to a preferred embodiment of the present invention, the mass ratio of acrylic resin to polymethyl methacrylate in step (2) is 1-2:1.

[0017] According to a preferred embodiment of the present invention, the mass ratio of acrylic resin to dichloromethane in step (2) is 0.02-0.1:1.

[0018] According to a preferred embodiment of the present invention, the mass ratio of dichloromethane in the oil phase to deionized water in the aqueous phase in step (3) is 0.1-0.6:1.

[0019] According to a preferred embodiment of the present invention, the shear emulsification in step (3) is performed by shear emulsification using a shear emulsifier at a rotation speed of 3000-5000 r / min for 5-15 min.

[0020] According to a preferred embodiment of the present invention, the evaporation temperature in step (3) is 40-50°C and the evaporation time is 1-3 hours.

[0021] According to a preferred embodiment of the present invention, the mass ratio of tetraethyl orthosilicate (TEOS) to the total mass of acrylic resin and polymethyl methacrylate in step (4) is 0.3-0.6:1, more preferably 0.35-0.5:1; and the dropping rate of the tetraethyl orthosilicate (TEOS) is 0.5-1 mL / min.

[0022] According to a preferred embodiment of the present invention, the mass ratio of 3-aminopropyltriethoxysilane to tetraethyl silicate (TEOS) in step (4) is 0.01-0.04:1; and the dropping rate of the 3-aminopropyltriethoxysilane is 0.1-0.3 mL / min.

[0023] According to a preferred embodiment of the present invention, the temperature of the reaction in step (4) is 40-50°C and the reaction time is 10-15h.

[0024] According to a preferred embodiment of the present invention, the washing in step (4) is washing with deionized water 3-5 times, and the drying is drying at 40-60°C for 20-30 hours.

[0025] This invention provides a water-based drilling fluid 200℃ and salt-temperature responsive cementing and wall-stabilizing agent, which is obtained by the above preparation method.

[0026] According to the present invention, the above-mentioned water-based drilling fluid 200°C and salt-resistant temperature-responsive cementitious wall-stabilizing agent is used in water-based drilling fluid, wherein the concentration of the water-based drilling fluid 200°C and salt-resistant temperature-responsive cementitious wall-stabilizing agent in the water-based drilling fluid is 2-5 wt%.

[0027] The technical features and beneficial effects of this invention are as follows:

[0028] 1. The temperature-responsive cementing and wall-solidifying agent of the present invention is prepared by solvent evaporation and sol-gel reaction, and the preparation process is simple.

[0029] 2. This invention uses polymethyl methacrylate as the inner shell of a temperature-responsive cementitious wall-stabilizing agent and silica as the outer shell. The resulting temperature-responsive cementitious wall-stabilizing agent has good stability and temperature resistance, and good dispersibility in drilling fluid, without affecting the rheological properties of drilling fluid. Furthermore, the temperature-responsive cementitious wall-stabilizing agent of this invention uses an organic inner shell and an inorganic rigid material as the outer shell, which has temperature-responsive characteristics and can quickly cope with complex downhole environmental conditions.

[0030] 3. After the temperature-responsive cementitious wall-consolidating agent of this invention breaks, the strong cementitious resin of the core material is released. After the acrylic resin comes into contact with the rock particles, it first forms hydrogen bonds with the hydroxyl groups (-OH) on the rock surface through surface wetting; the active groups (carboxyl-COOH, hydroxyl-OH) in the resin and the active sites on the rock surface (Si-OH of silicate minerals, Ca of carbonate minerals) 2+ Chemical bonding or strong polarity occurs, enhancing the cementation strength, thereby achieving rock cementation and reinforcement, and significantly strengthening the stability of the wellbore.

[0031] 4. The proportion control of each raw material and the control of reaction conditions in the temperature-responsive cementing wall-stabilizing agent of the present invention directly determine the cementing and wall-stabilizing ability and rheological regulation performance of the wall-stabilizing agent; any replacement of raw materials or unsuitable adjustment of process parameters will lead to the performance degradation or weakening of the synergistic effect of the temperature-responsive cementing wall-stabilizing agent, which will fail to meet the drilling fluid stability requirements in deep composite extreme environments. Attached Figure Description

[0032] Figure 1 Scanning electron microscope image of the 200°C-resistant and salt-temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluid prepared in Example 1.

[0033] Figure 2 The particle size distribution diagram of the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluid prepared in Example 1 is shown.

[0034] Figure 3 The infrared spectrum of the water-based drilling fluid 200℃ salt-temperature responsive cementitious wall-stabilizing agent prepared in Example 1. Detailed Implementation

[0035] The present invention will be further described below through specific embodiments, but is not limited thereto.

[0036] Unless otherwise specified, the experimental methods described in the examples are conventional methods; the reagents and materials used are commercially available unless otherwise specified.

[0037] The relative molecular mass of gum arabic used in the examples is 100,000; the weight-average molecular weight of polymethyl methacrylate is 1,000,000.

[0038] The acrylic resin is a thermosetting acrylic resin with a number average molecular weight of 20,000.

[0039] Example 1

[0040] A method for preparing a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent includes the following steps:

[0041] (1) Aqueous phase preparation: Add 15g of gum arabic and 1.5g of sodium dodecyl sulfonate to 300g of deionized water and stir to dissolve under ultrasonic conditions to obtain the aqueous phase.

[0042] (2) Preparation of oil phase: Under stirring conditions, 2g of acrylic resin and 1g of polymethyl methacrylate were added to 30g of dichloromethane and stirred evenly to obtain the oil phase.

[0043] (3) Add the oil phase obtained in step (2) to the aqueous phase obtained in step (1), and then place it in a shear emulsifier and shear emulsify at 3000 r / min for 10 min to obtain an oil-in-water emulsion; evaporate at 42℃ for 2 h to remove dichloromethane and obtain a mixture.

[0044] (4) 1.4 g of tetraethyl silicate (TEOS) was slowly added dropwise to the mixture at a rate of 0.8 mL / min and stirred until homogeneous. Then, 0.03 g of 3-aminopropyltriethoxysilane was added dropwise (at a rate of 0.2 mL / min) to the system to initiate a sol-gel reaction, promote the hydrolysis of TEOS, and form a dense silica shell. After the addition of 3-aminopropyltriethoxysilane, the mixture was reacted at 45 °C for 12 h. Afterward, the mixture was naturally cooled to room temperature, filtered, and the solid obtained from the filtration was washed four times with deionized water. The solid obtained from the washing was dried at 50 °C for 24 h to obtain a water-based drilling fluid 200 °C salt-temperature responsive cementing and wall-stabilizing agent.

[0045] Scanning electron microscope images of the water-based drilling fluid using the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent obtained in this embodiment are shown below. Figure 1 As shown, by Figure 1 It can be seen that the temperature-responsive cementitious wall-consolidating agent has good particle dispersibility, no agglomeration, and a particle size distribution of 25-45 micrometers. It exhibits a regular spherical structure, and the broken particles reveal a core-shell structure. Its particle size distribution diagram is shown below. Figure 2 As shown, by Figure 2 It can be seen that the median particle size of the temperature-responsive cementitious wall-consolidating agent particles is 39.75 micrometers.

[0046] The infrared spectrum of the water-based drilling fluid using the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent obtained in this embodiment is as follows: Figure 3 As shown, the absorption peaks of the CH stretching vibrations of methylene (-CH2-) and methyl (-CH3) groups can be observed in the infrared spectrum, and the absorption peak of the C=C bond appears at 1510 cm⁻¹. -1 The asymmetric stretching vibration of COC appears at 1030 cm⁻¹. -1 In addition, there are absorption peaks of Si-O-Si tensile vibration of silica, which confirm the successful preparation of the wall-solidifying agent.

[0047] Example 2

[0048] A method for preparing a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent includes the following steps:

[0049] (1) Aqueous phase preparation: Add 15g of gum arabic and 1.5g of sodium dodecyl sulfonate to 300g of deionized water and stir to dissolve under ultrasonic conditions to obtain the aqueous phase.

[0050] (2) Preparation of oil phase: Under stirring conditions, 2g of acrylic resin and 2g of polymethyl methacrylate were added to 30g of dichloromethane and stirred evenly to obtain the oil phase.

[0051] (3) Add the oil phase obtained in step (2) to the aqueous phase obtained in step (1), and then place it in a shear emulsifier and shear emulsify at 3000 r / min for 10 min to obtain an oil-in-water emulsion; evaporate at 42℃ for 2 h to remove dichloromethane and obtain a mixture.

[0052] (4) 1.4 g of tetraethyl silicate (TEOS) was slowly added dropwise to the mixture at a rate of 0.8 mL / min and stirred until homogeneous. Then, 0.03 g of 3-aminopropyltriethoxysilane was added dropwise (at a rate of 0.2 mL / min) to the system to initiate a sol-gel reaction, promote the hydrolysis of TEOS, and form a dense silica shell. After the addition of 3-aminopropyltriethoxysilane, the mixture was reacted at 45 °C for 12 h. Afterward, it was naturally cooled to room temperature, filtered, and the solid obtained from the filtration was washed four times with deionized water. The solid obtained from the washing was dried at 50 °C for 24 h to obtain a water-based drilling fluid 200 °C salt-temperature responsive cementing and wall-stabilizing agent.

[0053] Example 3

[0054] A method for preparing a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent includes the following steps:

[0055] (1) Aqueous phase preparation: Add 30g of gum arabic and 3g of sodium dodecyl sulfonate to 300g of deionized water and stir until completely dissolved to obtain the aqueous phase.

[0056] (2) Preparation of oil phase: Under stirring conditions, 2g of acrylic resin and 2g of polymethyl methacrylate were added to 180g of dichloromethane and stirred evenly to obtain the oil phase.

[0057] (3) Add the oil phase obtained in step (2) to the aqueous phase obtained in step (1), and then place it in a shear emulsifier and shear emulsify at 3000 r / min for 10 min to obtain an oil-in-water emulsion; evaporate at 45℃ for 2 h to remove organic solvent and obtain a mixture.

[0058] (4) 1.4 g of tetraethyl silicate (TEOS) was slowly added dropwise to the mixture at a rate of 0.8 mL / min and stirred until homogeneous. Then, 0.056 g of 3-aminopropyltriethoxysilane was added dropwise (at a rate of 0.2 mL / min) to the system to initiate a sol-gel reaction, promote the hydrolysis of TEOS, and form a dense silica shell. After the addition of 3-aminopropyltriethoxysilane, the mixture was reacted at 45 °C for 12 h. Afterward, it was naturally cooled to room temperature, filtered, and the solid obtained by filtration was washed four times with deionized water. The solid obtained by washing was dried at 50 °C for 24 h to obtain a water-based drilling fluid 200 °C salt-temperature responsive cementing and wall-stabilizing agent.

[0059] Example 4

[0060] A method for preparing a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent includes the following steps:

[0061] (1) Preparation of aqueous phase: Add 9g of gum arabic and 0.15g of sodium dodecyl sulfonate to 300g of deionized water and stir until completely dissolved to obtain the aqueous phase.

[0062] (2) Preparation of oil phase: Under stirring conditions, 2g of acrylic resin and 2g of polymethyl methacrylate were added to 30g of dichloromethane and stirred evenly to obtain the oil phase.

[0063] (3) Add the oil phase obtained in step (2) to the aqueous phase obtained in step (1), and then place it in a shear emulsifier and shear emulsify at 3000 r / min for 10 min to obtain an oil-in-water emulsion; evaporate at 45℃ for 2 h to remove organic solvent and obtain a mixture.

[0064] (4) 1.4 g of tetraethyl silicate (TEOS) was slowly added dropwise to the mixture at a rate of 0.8 mL / min and stirred until homogeneous. Then, 0.014 g of 3-aminopropyltriethoxysilane was added dropwise (at a rate of 0.2 mL / min) to the system to initiate a sol-gel reaction, promote the hydrolysis of TEOS, and form a dense silica shell. After the addition of 3-aminopropyltriethoxysilane, the mixture was reacted at 45 °C for 12 h. Afterward, it was naturally cooled to room temperature, filtered, and the solid obtained by filtration was washed four times with deionized water. The solid obtained by washing was dried at 50 °C for 24 h to obtain a water-based drilling fluid 200 °C salt-temperature responsive cementing and wall-stabilizing agent.

[0065] Example 5

[0066] The preparation method of a water-based drilling fluid 200℃ salt-temperature responsive cementing wall-stabilizing agent is as described in Example 1, except that 0.9g of tetraethyl silicate (TEOS) is added in step (4).

[0067] Example 6

[0068] The preparation method of a water-based drilling fluid 200℃ salt-temperature responsive cementing and wall-stabilizing agent is as described in Example 1, except that 1.8g of tetraethyl silicate (TEOS) is added in step (4).

[0069] Comparative Example 1

[0070] A method for preparing a wall-stabilizing agent for water-based drilling fluid is described in Example 1, except that gum arabic is not added in step (1).

[0071] Comparative Example 2

[0072] A method for preparing a wall-stabilizing agent for water-based drilling fluid is described in Example 1, except that sodium dodecyl sulfonate is not added in step (1).

[0073] Comparative Example 3

[0074] A method for preparing a wall-solidifying agent for water-based drilling fluid is described in Example 1, except that: in step (2), an equal mass of urea-formaldehyde resin is used instead of acrylic resin.

[0075] Comparative Example 4

[0076] A method for preparing a wall-stabilizing agent for water-based drilling fluid is described in Example 1, except that polymethyl methacrylate is not added in step (2).

[0077] Comparative Example 5

[0078] A method for preparing a wall-stabilizing agent for water-based drilling fluid is described in Example 1, except that 3g of polymethyl methacrylate is added in step (2).

[0079] Comparative Example 6

[0080] A method for preparing a wall-stabilizing agent for water-based drilling fluid is described in Example 1, except that 3-aminopropyltriethoxysilane is not added in step (4).

[0081] Experimental Example 1

[0082] The wall-fixing agents prepared in the examples and comparative examples were evaluated for the following performance:

[0083] 1. Effect of wall-fixing agent on the rheological properties of the base slurry before and after aging

[0084] Preparation of 4% bentonite-based slurry: Add 16g bentonite and 0.56g anhydrous sodium carbonate to 400mL of water, stir thoroughly at room temperature, seal and hydrate for 24h to obtain 4% bentonite-based slurry;

[0085] Preparation of brine drilling fluid samples: Take 400 mL of 4% bentonite-based slurry, add 12 g of the wall-stabilizing agent prepared in the examples and comparative examples and 256 g (15%) of sodium chloride, and stir at 5000 r / min for 20 min at room temperature to obtain brine drilling fluid samples; the mass of the wall-stabilizing agent in the drilling fluid sample is 3% of the volume of the bentonite-based slurry.

[0086] Drilling fluid aging: The above drilling fluid samples were placed in a roller heating furnace and aged at 200℃ for 16 hours. The rheological properties of the drilling fluid were tested according to the American Petroleum Institute (API) standard (API RP 13B-1, 2019). The results are shown in Tables 1 and 2.

[0087] Table 1. Rheological property data of drilling fluid obtained by adding the wall-solidifying agent prepared in the examples.

[0088]

[0089] Table 2. Rheological property data of drilling fluids obtained by adding wall-solidifying agents prepared in the comparative example.

[0090]

[0091] As can be seen from the test results in Tables 1 and 2, after adding the temperature-responsive cementitious wall-stabilizing agent prepared in the examples, there was no significant increase in the apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP) of the drilling fluid before and after aging. It also had no effect on the rheological properties of the drilling fluid base slurry, and the filtration loss (FL) was [not specified]. API The filtration efficiency is significantly reduced. In summary, the temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluids prepared in this invention still exhibits excellent rheological properties and filtration loss reduction properties after aging, effectively enhancing wellbore stability.

[0092] 2. Tensile strength test of single lap joint

[0093] The strength of shale flakes bonded by temperature-responsive cementitious wall-consolidating agent was tested using a single-lap joint test. Shale flakes of 50×20×5mm were selected. After sanding the test area with sandpaper, a 3% (w / w) water solution of wall-consolidating agent was evenly applied to the single-lap joint surface of the shale flakes (water treatment served as a blank control group) and pressurized (5MPa for 10min). The flakes were then placed in an aging tank containing salt-based slurry and aged at 200℃ for 16h. The tensile strength in air was tested using a universal testing machine. The results are shown in Table 3.

[0094] Preparation of brine-based slurry: Add 16g of bentonite and 0.56g of anhydrous sodium carbonate to 400mL of water, stir thoroughly at room temperature, seal and hydrate for 24h to obtain 4% bentonite-based slurry; take 400mL of 4% bentonite-based slurry, add 256g (15%) sodium chloride, stir at 5000r / min for 20min at room temperature to obtain brine-based slurry.

[0095] Table 3 Shear strength of shale slices after treatment with different wall-stabilizing agents

[0096]

[0097] As can be seen from the experimental data in Table 3, the shale flakes coated with the temperature-responsive cementitious wall-stabilizing agent prepared in this invention exhibit significantly higher shear strength than the clean water group after immersion in a high-temperature (200℃) brine (15%) environment. This demonstrates that the temperature-responsive cementitious wall-stabilizing agent of this invention has strong wall-stabilizing ability, effectively improving the shear strength of shale, enhancing wellbore stability, and effectively reducing the occurrence of complex downhole conditions.

[0098] 3. High-temperature immersion experiment

[0099] Preparation of 4% bentonite-based slurry: Add 16g bentonite and 0.56g anhydrous sodium carbonate to 400mL of water, stir thoroughly at room temperature, seal and hydrate for 24h to obtain 4% bentonite-based slurry;

[0100] Preparation of brine drilling fluid samples: Take 400 mL of 4% bentonite-based slurry, add 12 g of the wall-solidifying agent prepared in the examples and comparative examples, and 256 g (15%) sodium chloride, and stir at 5000 r / min for 20 min at room temperature to obtain brine drilling fluid samples; the mass of the wall-solidifying agent in the drilling fluid sample is 3% of the volume of the bentonite-based slurry.

[0101] Take 30 grams of 10-mesh shale rock cuttings and place them in a molding press (D=15mm). Add 3 mL of distilled water and press for 10 minutes at 15 MPa. Remove the core. Place the core in different salt drilling fluid samples and soak at 200℃ for 16 hours. Observe the integrity of the artificial core. See Table 4.

[0102] Table 4. Integrity of artificial core samples after high-temperature immersion in different drilling fluids for 16 hours.

[0103]

[0104] As can be seen from the test results in Table 4, after adding the temperature-responsive cementing and wall-stabilizing agent prepared in the example and aging at high temperature for 16 hours, the core can maintain a stable and intact morphology. This indicates that the temperature-responsive cementing and wall-stabilizing agent of the present invention has a strong wall-stabilizing ability under high temperature and high salinity conditions, which can significantly improve the cementing force of the rock and strengthen the stability of the well wall.

[0105] In summary, the temperature-responsive cementing and wall-stabilizing agent of the present invention has excellent cementing and wall-stabilizing capabilities and high-temperature resistance, and can effectively enhance wellbore stability.

[0106] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. In addition, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed by the present invention.

Claims

1. A method for preparing a water-based drilling fluid 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent, characterized in that, The steps include the following: (1) Add gum arabic and emulsifier to deionized water and stir evenly to obtain an aqueous phase; the mass ratio of gum arabic to water is 0.03-0.1:1; the emulsifier is sodium dodecyl sulfonate, and the mass ratio of emulsifier to deionized water is 0.0005-0.01:1; (2) Dissolve acrylic resin and polymethyl methacrylate in dichloromethane to obtain an oil phase; the mass ratio of acrylic resin to polymethyl methacrylate is 1-2:1, and the mass ratio of acrylic resin to dichloromethane is 0.02-0.1:1; the acrylic resin is a thermosetting acrylic resin; the number average molecular weight of the acrylic resin is 10,000-20,000; the weight average molecular weight of the polymethyl methacrylate is 800,000-1,200,000. (3) Add the oil phase obtained in step (2) to the aqueous phase obtained in step (1) and perform shear emulsification to obtain an oil-in-water emulsion; heat up and evaporate to remove the organic solvent in the emulsion to obtain a mixture; the mass ratio of dichloromethane in the oil phase to deionized water in the aqueous phase is 0.1-0.6:

1. (4) Add tetraethyl silicate dropwise to the mixture and stir evenly. Then add 3-aminopropyltriethoxysilane dropwise to the system and react. After the reaction is completed, filter, wash and dry to obtain a water-based drilling fluid 200℃ salt-temperature responsive cementing and wall-stabilizing agent. The mass ratio of tetraethyl silicate to the total mass of acrylic resin and polymethyl methacrylate is 0.3-0.6:

1. The mass ratio of 3-aminopropyltriethoxysilane to tetraethyl silicate is 0.01-0.04:

1. The reaction temperature is 40-50℃ and the reaction time is 10-15h.

2. The preparation method of the 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent for water-based drilling fluid according to claim 1, characterized in that, The mass ratio of gum arabic to water in step (1) is 0.04-0.06:

1.

3. The preparation method of the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluid according to claim 1, characterized in that, The mass ratio of the emulsifier to deionized water in step (1) is 0.001-0.008:

1.

4. The preparation method of the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluid according to claim 1, characterized in that, The shear emulsification in step (3) is performed by shear emulsifying for 5-15 minutes at a rotation speed of 3000-5000 r / min using a shear emulsifier; the evaporation temperature is 40-50℃ and the evaporation time is 1-3 hours.

5. The preparation method of the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluid according to claim 1, characterized in that, In step (4), the mass ratio of tetraethyl silicate to the total mass of acrylic resin and polymethyl methacrylate is 0.35-0.5:1; the dropping rate of tetraethyl silicate is 0.5-1 mL / min; and the dropping rate of 3-aminopropyltriethoxysilane is 0.1-0.3 mL / min.

6. The preparation method of the 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent for water-based drilling fluid according to claim 1, characterized in that, The washing in step (4) involves washing with deionized water 3-5 times, and the drying involves drying at 40-60℃ for 20-30 hours.

7. A water-based drilling fluid 200℃ and salt-temperature responsive cementitious wall-stabilizing agent, characterized in that, It is obtained by the preparation method described in any one of claims 1-6.

8. The application of the 200℃-resistant and salt-temperature-responsive cementitious wall-stabilizing agent for water-based drilling fluids according to claim 7 in water-based drilling fluids, characterized in that, The concentration of the water-based drilling fluid using a 200℃-resistant and salt-temperature-responsive cementing and wall-stabilizing agent is 2-5 wt%.

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