Laponite-polymer large temperature difference constant flow rheological modifier, and preparation method and application thereof

Abstract

The application provides a hectorite-polymer large-temperature-difference constant-flow rheological modifier and a preparation method and application thereof. The rheological modifier comprises the following raw materials in parts by weight: 2-5 parts of nano hectorite, 4-10 parts of a silane coupling agent, 8-12 parts of a monomer containing an adsorption group, 10-15 parts of an anionic monomer, 5-8 parts of a cationic monomer, 2-5 parts of a temperature-sensitive monomer and 0.14-0.18 parts of an initiator. The preparation method of the rheological modifier is as follows: the nano hectorite is modified by using the silane coupling agent first, and then the modified nano hectorite is subjected to a copolymerization reaction with a mixed solution of various monomers under vacuum and in the presence of the initiator to prepare the hectorite-polymer large-temperature-difference constant-flow rheological modifier. The application also provides the application of the rheological modifier in a natural gas hydrate drilling fluid. The hectorite-polymer large-temperature-difference constant-flow rheological modifier provided by the application has good temperature resistance and salt resistance, excellent low-temperature regulation capacity and a wide temperature application range.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemistry technology in the petroleum industry, specifically to a lithium saponite-polymer large temperature difference constant flow variable flow regulator and its preparation method and application. Background Technology

[0002] In recent years, the oil and gas industry has developed rapidly. Natural gas hydrates possess advantages such as high energy density, wide distribution, large scale, shallow burial, and great resource potential. Widely distributed in seabed sediments and polar permafrost zones, they are considered an ideal alternative energy source for the new century. However, due to geographical and geological conditions, the application and development of natural gas hydrates face significant challenges and various problems. Most marine natural gas hydrate deposits are located in deep-sea areas with temperatures generally around 4°C (and even lower in some places); the temperature of natural gas hydrate formations in permafrost zones is even lower, although the upper strata may exhibit high temperatures and high salinity. Currently, the main technology for natural gas hydrate extraction is water-based drilling fluid technology. During the process of drilling fluid traveling from the hydrate formation to the surface, it undergoes a low-temperature-high-temperature-low-temperature cycle, with temperature variations over a wide range. Operating the drilling fluid in such complex temperature-varying formations causes drastic changes in its rheological properties.

[0003] Low temperatures cause a sharp increase in drilling fluid viscosity, increasing circulation resistance within the tubing string and impacting safe drilling in narrow density windows in deep-sea environments. Conversely, high temperatures decrease drilling fluid viscosity, making rheological properties difficult to control. Both significantly affect the suspension and proppant-carrying capacity of drilling fluids, greatly increasing drilling operation risks. Because drilling fluids are subjected to high and low temperature cycles during wellbore circulation, the chain structure of polymer treatment agents is prone to change, potentially leading to weakened or even lost functionality, thus drastically reducing the service life of the drilling fluid.

[0004] Recently developed deep-water water-based rheology modifiers, such as microemulsion polymers and thermosensitive polymers, have been used as key treatment agents to enhance the rheological stability of drilling fluids at low temperatures, but they lack the ability to cope with high-temperature and high-salinity conditions. Conventional rheology modifiers have excellent shear strength and shear stability at normal temperatures, but their low-temperature rheological control capabilities are insufficient. They are prone to causing significant changes in drilling fluid viscosity and shear stress at low temperatures, and they are also inadequate when facing high-temperature and high-salinity conditions. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a lithium saponite-polymer large-temperature-difference constant-flow variable-current regulator, its preparation method, and its application. The lithium saponite-polymer large-temperature-difference constant-flow variable-current regulator provided by the present invention exhibits good temperature and salt resistance, excellent low-temperature regulation capability, and a wide applicable temperature range.

[0006] To achieve the above objectives, the first aspect of the present invention provides a lithium saponite-polymer large temperature difference constant flow variable flow regulator, which, by weight, comprises the following raw materials: 2-5 parts of nano lithium saponite, 4-10 parts of silane coupling agent, 8-12 parts of monomer containing adsorption groups, 10-15 parts of anionic monomer, 5-8 parts of cationic monomer, 2-5 parts of thermosensitive monomer, and 0.14-0.18 parts of initiator.

[0007] According to a specific embodiment of the present invention, preferably, the above-mentioned lithium saponite-polymer large temperature difference constant flow variable flow regulator comprises the following raw materials in parts by weight: 3-5 parts of nano lithium saponite, 6-10 parts of silane coupling agent, 8-12 parts of monomer containing adsorption groups, 12-15 parts of anionic monomer, 5-8 parts of cationic monomer, 3-5 parts of thermosensitive monomer, and 0.14-0.18 parts of initiator.

[0008] In the above-mentioned lithium saponite-polymer large temperature difference constant current variable flow regulator, preferably, the average thickness of the nano lithium saponite (RD) is 1nm-10nm and the average diameter is 25nm-50nm.

[0009] In the above-mentioned lithium saponite-polymer large temperature difference constant current variable flow regulator, preferably, the silane coupling agent includes one or a combination of several of γ-methacryloyloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane (KH-171), and vinyltriethoxysilane (KH-151).

[0010] In the above-mentioned lithium saponite-polymer large temperature difference constant flow variable flow regulator, preferably, the monomer containing adsorption groups includes acrylamide (AM) and / or N,N-dimethylacrylamide (DMAA), etc.

[0011] In the above-mentioned lithium saponite-polymer large temperature difference constant current variable flow regulator, preferably, the anionic monomer includes one or a combination of several of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sodium p-styrene sulfonate (SSS), sodium vinyl sulfonate (VS), and styrene (St).

[0012] In the above-mentioned lithium saponite-polymer large temperature difference constant current variable flow regulator, preferably, the cationic monomer includes one or a combination of several of the following: dimethyl diallyl ammonium chloride (DMDAAC), 3-acrylamidopropyl-trimethylammonium chloride (TAC), and methacryloyloxyethyltrimethylammonium chloride (DMC).

[0013] In the above-mentioned lithium saponite-polymer large temperature difference constant flow variable flow regulator, preferably, the temperature-sensitive monomer includes one or a combination of several of N-vinylcaprolactam (NVCL), 4-acryloylmorpholine (ACMO), N-isopropylacrylamide (NIPAM), N,N-diethylacrylamide (DEA), and diacetone acrylamide (DAAM).

[0014] In the above-mentioned lithium saponite-polymer large temperature difference constant current type regulator, preferably, the initiator includes one or a combination of several of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (AIVN), and dimethyl azobisisobutyrate (AIBME).

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned lithium saponite-polymer large temperature difference constant current variable flow regulator, which includes the following steps:

[0016] (1) According to the weight, 2-5 parts (preferably 3-5 parts) of nano lithium saponite and 4-10 parts (preferably 6-10 parts) of silane coupling agent are mixed in the first solvent, reacted for a period of time, and then separated, washed and dried to obtain modified nano lithium saponite.

[0017] (2) Mix 8-12 parts of monomers containing adsorption groups, 10-15 parts (preferably 12-15 parts) of anionic monomers, 5-8 parts of cationic monomers and 2-5 parts (preferably 3-5 parts) of thermosensitive monomers in a second solvent to obtain a monomer mixed solution;

[0018] (3) Disperse the modified nano-lithium saponite obtained in step (1) in a third solvent to obtain a modified nano-lithium saponite dispersion; then mix the modified nano-lithium saponite dispersion with the monomer mixed solution obtained in step (2) to obtain a mixed solution;

[0019] (4) After adjusting the pH value of the mixture obtained in step (3), the mixture is reacted for a period of time under vacuum, nitrogen atmosphere, at a certain temperature and in the presence of 0.14-0.18 parts of initiator. After separation, washing and drying, the lithium saponite-polymer large temperature difference constant flow variable flow regulator is obtained.

[0020] In the above preparation method, preferably, the first solvent in step (1) is an organic solvent. More preferably, the first solvent includes one or a combination of several of acetone, petroleum ether, diethyl ether, and toluene. Particularly preferably, the ratio of the first solvent to the nano-lithium saponite is 10 mL:(1-2) g.

[0021] In the above preparation method, preferably, step (1) involves mixing and reacting the nano-lithium saponite and the silane coupling agent in a first solvent using ultrasonic dispersion. More preferably, the ultrasonic power is 300-600 W, and the frequency is 20 kHz or 28 kHz.

[0022] In the above preparation method, preferably, the reaction temperature in step (1) is 25-35℃ and the reaction time is 0.5-1h.

[0023] In the above preparation method, after the reaction in step (1) is completed, the reaction product can be separated, washed, and dried. The separation can be performed using conventional methods in the art, such as centrifugation. The washing can be performed repeatedly using solvents such as ethanol or acetone (e.g., three times). The drying temperature is preferably 50-70°C, and the drying time is preferably 8-12 hours. More preferably, the drying is performed in a vacuum oven.

[0024] In the above preparation method, preferably, the second solvent in step (2) includes water, etc. The water used can be deionized water or distilled water, etc. More preferably, the ratio of the second solvent to all monomers is 10 mL: (2-5) g. Here, all monomers refer to the monomers containing adsorption groups, anionic monomers, cationic monomers, and thermosensitive monomers mentioned above in this invention.

[0025] In the above preparation method, preferably, the third solvent in step (3) includes ethanol or the like. More preferably, the ratio of the third solvent to the modified nano-lithium saponite is (2-6) mL: 1 g.

[0026] In the above preparation method, preferably, step (3) involves dispersing the modified nano-lithium saponite in a third solvent using ultrasonic dispersion for 5-10 minutes to obtain the modified nano-lithium saponite dispersion. More preferably, the ultrasonic power is 300-600 W and the frequency is 20 kHz or 28 kHz.

[0027] In the above preparation method, preferably, in step (4), the pH value of the mixture obtained in step (3) is adjusted to 6.0-8.0. More preferably, the pH value of the mixture is adjusted using a sodium hydroxide solution. The concentration of the sodium hydroxide solution can be 30 wt%.

[0028] In the above preparation method, preferably, in step (4), the vacuum condition is created by continuously stirring the mixture under a high-purity nitrogen stream for 0.2-1 h. In step (4) of the preparation method of the present invention, before adding the initiator, nitrogen is purged for a period of time, for example, 0.2-1 h (preferably 0.5 h), to create a vacuum environment.

[0029] In the above preparation method, preferably, in step (4), the reaction is carried out under vacuum conditions, a nitrogen atmosphere, at 60-75°C, and in the presence of 0.14-0.18 parts of initiator for 4-6 hours. The reaction in the presence of the initiator is also carried out under continuous nitrogen purging until the reaction is complete.

[0030] In the above preparation method, after the reaction in step (4) is completed, the reaction product can be separated, washed, and dried. The washing can be performed repeatedly using solvents such as ethanol or acetone (e.g., 3 times). The drying temperature is preferably 70-80℃, and the drying time is preferably 12-24 hours. More preferably, the drying is carried out in a vacuum oven.

[0031] According to a specific embodiment of the present invention, preferably, the above preparation method includes the following steps:

[0032] (1) According to the weight, 2-5 parts (more preferably 3-5 parts) of nano-lithium saponite are added to the first solvent and ultrasonically dispersed for 5-10 min (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano-lithium saponite; 4-10 parts (more preferably 6-10 parts) of silane coupling agent are added at 25-35℃, ultrasonic dispersion is continued, and the reaction is carried out for 0.5-1 h. After separation, washing and drying (drying temperature of 50-70℃, time of 8-12 h), modified nano-lithium saponite is obtained; the first solvent includes one or more of acetone, petroleum ether, diethyl ether and toluene, etc., and the ratio of its amount to the nano-lithium saponite is 10mL:(1-2)g.

[0033] (2) Mix 8-12 parts of monomer containing adsorption groups, 10-15 parts (more preferably 12-15 parts) of anionic monomer, 5-8 parts of cationic monomer and 2-5 parts (more preferably 3-5 parts) of thermosensitive monomer in a second solvent to obtain a monomer mixed solution; the second solvent includes water, and the ratio of water to all monomers is 10 mL: (2-5) g.

[0034] (3) Add the modified nano-lithium saponite obtained in step (1) to the third solvent and ultrasonically disperse for 5-10 min (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to obtain a modified nano-lithium saponite dispersion; then stir and mix the modified nano-lithium saponite dispersion with the monomer mixed solution obtained in step (2) to obtain a mixed solution; the third solvent includes ethanol, and the ratio of its amount to the modified nano-lithium saponite is (2-6) mL: 1g;

[0035] (4) After adjusting the pH value of the mixture obtained in step (3) to 6.0-8.0, it is continuously stirred under a high-purity nitrogen flow for 0.2-1h (more preferably 0.5h) to create a vacuum condition; then it is heated to 60-75℃ in a constant temperature water bath, and 0.14-0.18 parts of initiator are added. Under vacuum conditions, nitrogen atmosphere, 60-75℃ and in the presence of initiator, the reaction is carried out for 4-6h. After separation, washing and drying (drying temperature is 70-80℃, time is 12-24h), the lithium saponite-polymer large temperature difference constant flow variable flow regulator is obtained.

[0036] The third aspect of this invention provides the application of the above-mentioned lithium saponite-polymer large temperature difference constant flow variable flow regulator in natural gas hydrate drilling fluid.

[0037] The preparation method of the lithium saponite-polymer large temperature difference constant flow modulator of the present invention firstly involves graft modification of nano-lithium saponite, and then synthesizing the lithium saponite-polymer large temperature difference constant flow modulator by free radical aqueous solution polymerization. This flow modulator is formed by copolymerization of temperature-insensitive inorganic nano-lithium saponite and various specific monomers, possessing a unique network structure that can effectively regulate various rheological parameters of the drilling fluid system.

[0038] The polymerization monomers used in this invention include monomers containing adsorption groups and anionic monomers containing sulfonic acid groups. A small amount of cationic monomers and a certain amount of temperature-sensitive monomers are also introduced. Each monomer and its specific dosage, along with a specific dosage of silane coupling agent, produces a synergistic effect on the modified nano-lithium saponite. Specifically, the dosage of silane coupling agent specified in this invention allows for sufficient grafting of the polymer onto the surface of the nano-lithium saponite. The dosages of anionic and cationic monomers specified in this invention enable the prepared flow modifier to better promote clay hydration and dispersion, and to better promote the bonding between the material and the clay. Ultimately, the flow modifier of this invention exhibits improved temperature and salt resistance compared to existing materials, and also demonstrates excellent thickening and shearing effects at low temperatures, while inhibiting hydrate nucleation and growth. Due to its unique structure, the flow modifier of this invention effectively addresses the rheological deterioration caused by changes in external environmental factors such as high and low temperature variations and electrolyte intrusion; it is not easily degraded or ineffective at high temperatures, does not curl under high salt conditions, and does not precipitate at low temperatures. This flow modifier also possesses excellent rheological regulation capabilities, enabling it to address the deterioration of rheological properties in natural gas hydrate drilling fluids caused by large temperature variations, achieving a "one-dose-through" process throughout the entire natural gas hydrate drilling process. Therefore, the flow modifier provided by this invention overcomes the problems of insufficient temperature and salt resistance, and lack of low-temperature rheological regulation capabilities of existing flow modifiers.

[0039] This invention has the following superior technical effects:

[0040] (1) The lithium saponite-polymer large temperature difference constant flow variable flow regulator provided by the present invention has good temperature resistance.

[0041] The flow modifier of this invention incorporates heat-resistant nano-lithium saponite, enhancing its temperature resistance and improving its adsorption to clay in drilling fluid. Furthermore, it contains rigid groups and branched monomers with high-temperature resistant groups, forming a three-dimensional spatial network structure with good high-temperature stability, enabling it to cope with the complex conditions of different high-temperature formations.

[0042] (2) The lithium saponite-polymer large temperature difference constant flow variable flow regulator provided by the present invention has good salt resistance.

[0043] The flow pattern regulator of the present invention contains a small amount of cationic monomer, which gives the flow pattern regulator certain intramolecular ionic bonds and a certain salt response effect. In addition, due to the presence of nano-lithium saponite, it has a stable polymer network structure, low salt sensitivity, and improves the salt resistance of the flow pattern regulator.

[0044] (3) The lithium saponite-polymer large temperature difference constant flow variable flow regulator provided by the present invention has excellent low temperature regulation capability.

[0045] The flow modifier of the present invention contains a temperature-sensitive monomer. When the temperature is low, the polymer molecules expand, making it difficult for the flow modifier to precipitate from the drilling fluid. Furthermore, the flow modifier contains inorganic nano-lithium saponite, which is not sensitive to low temperatures and is sufficient to cope with the situation where the viscosity and shear stress of the drilling fluid increase sharply at low temperatures, and even obvious gelation occurs.

[0046] (4) The lithium saponite-polymer large temperature difference constant flow variable flow regulator provided by the present invention has a wide temperature application range.

[0047] (5) The lithium saponite-polymer thermostatic flow modulator provided by the present invention can inhibit the nucleation and growth of hydrates during drilling, and prevent hydrates from accumulating in the wellbore and inducing well-related complications.

[0048] In summary, this invention addresses the problems of narrow temperature adaptability and poor salt resistance of existing water-based constant rheological drilling fluid flow modifiers by developing a large temperature difference constant rheological flow modifier based on lithium saponite grafted polymer and its preparation method. During large temperature difference drilling, the flow modifier of this invention exhibits excellent rheological control capabilities at low temperatures while also possessing high-temperature and salt resistance, providing technical support for large temperature difference drilling engineering in oil and gas extraction. Attached Figure Description

[0049] Figure 1 Infrared spectra of the modified nano-lithium saponite and the lithium saponite-polymer large temperature difference constant current variable flow modulator provided in Example 1.

[0050] Figure 2 Thermogravimetric analysis-differential scanning calorimetry (DSC) of the lithium saponite-polymer large temperature difference constant current variable flow regulator provided in Example 1.

[0051] Figure 3 The effect of the flow pattern modifiers provided in Examples 1-3 and Comparative Examples 1-4 on the hydrate formation induction time is shown in the figure. Detailed Implementation

[0052] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0053] All raw materials used in the following examples and comparative examples are commercially available. Among them, the nano lithium saponite (RD) used is a synthetic trioctahedral layered colloidal material (purchased from Guangzhou Daixun Trading Co., Ltd.), with an average thickness of 1 nm and an average diameter of 25 nm-50 nm.

[0054] Example 1

[0055] This embodiment provides a lithium saponite-polymer large temperature difference constant current flow regulator, which is prepared through the following steps:

[0056] (1) Add 5g of nano lithium saponite to 50mL of acetone and ultrasonically disperse at room temperature for 5min (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano lithium saponite; heat the stable suspension of nano lithium saponite to 30℃, add 10g of silane coupling agent KH570, continue ultrasonic dispersion, react for 1h to obtain a white solid product, then separate the solid product, wash it 3 times with anhydrous ethanol, and dry it at 65℃ for 12h to obtain 5g of modified nano lithium saponite;

[0057] (2) Take 8g of acrylamide, 12g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of dimethyldiallylammonium chloride, and 4g of 4-acryloylmorpholine, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution.

[0058] (3) Take 5g of the modified nano lithium saponite obtained in step (1) and dissolve it in 10mL of ethanol. Disperse it by ultrasonication for 5min (the power of ultrasonication is 300-600w and the frequency is 20KHz or 28KHz) to obtain the modified nano lithium saponite dispersion. Then add the monomer mixed solution obtained in step (2) and stir to mix evenly to obtain a mixed solution.

[0059] (4) Adjust the pH of the mixture obtained in step (3) to 7 using 30wt% sodium hydroxide solution. Then, transfer the pH-adjusted mixture to a four-necked flask and stir continuously for 0.5h under a high-purity nitrogen flow to create a vacuum environment. Heat the mixture from ambient temperature to 65°C using a constant temperature water bath. Then, add 0.15g of azobisisobutyronitrile and react for 5h under vacuum conditions, nitrogen atmosphere, 65°C and in the presence of azobisisobutyronitrile to obtain a white product. Separate the white product and wash it three times with ethanol and acetone to remove unreacted monomers. Then, dry it in an 80°C vacuum oven for 24h. After drying, take it out and pulverize it to obtain the lithium saponite-polymer large temperature difference constant flow modulator of this embodiment.

[0060] The modified nano-lithium saponite from step (1) of this embodiment and the lithium saponite-polymer large temperature difference constant current converter prepared in this embodiment were analyzed by infrared spectroscopy using a Thermo Fisher Scientific Nicolet iS50 infrared spectrometer (KBr pellet). The results are as follows: Figure 1 As shown. Figure 1 The infrared (FTIR) spectra of the modified nano-lithium saponite and the lithium saponite-polymer large temperature difference constant current variable flow modulator provided in this embodiment.

[0061] pass Figure 1It can be seen that the modified nano-lithium saponite at 3450 cm⁻¹ -1 and 1648cm -1 Stretching and bending vibrations of -OH groups were observed nearby, which were caused by the hydroxyl groups on the adsorbed water and the nano-lithium saponite; 3690 cm⁻¹ -1 A small peak exists at 1010, 650, and 460 cm⁻¹, which may correspond to the stretching vibration of Mgs-OH on the surface of lithium saponite; -1 Characteristic peaks of Si-O tensile vibration, Mg-OH-Mg bending vibration, and Si-O-Mg deformation vibration were detected nearby. After grafting KH570, nano-lithium saponite showed peaks at 1706 cm⁻¹. -1 A sharp band at the site was observed, attributed to hydrogen-bonded carbonyl groups. Lithium saponite-polymer large-difference constant-fluid modulator (i.e., Figure 1 (Lithium saponite polymer) at 3450cm -1 The increased peak area is due to the stretching vibrations of -OH groups on adsorbed water and nano-lithium saponite, as well as the presence of NH bonds in -CONH2; 2930 cm⁻¹ -1 The area near the morpholine ring is the absorption band of saturated C-H bonds (CH), at 1110 cm⁻¹. -1 The absorption peak at 1450 cm⁻¹ is generated by the carbon-oxygen bond (CO) in the morpholine ring; then, at 1450 cm⁻¹... -1 The absorption peak at 1190 cm⁻¹ indicates the bending vibration of CH in the DMDAAC chain segment; finally, the absorption peak at 1190 cm⁻¹... -1 1044cm -1 The absorption peaks at these locations correspond to the stretching vibrations of the C=O and SO bonds in the -SO3H group of the AMPS repeating unit. Infrared spectroscopy confirmed the successful modification of nano-lithium saponite and the successful synthesis of lithium saponite-polymer composite materials.

[0062] The thermal stability of the lithium saponite-polymer large temperature difference constant current converter of this embodiment was tested in a nitrogen atmosphere using a NETZSCH STA 449F5 thermogravimetric analyzer. The results are as follows: Figure 2 As shown. Figure 2 Thermogravimetric analysis-differential scanning calorimetry (TG-DSC) curve of the lithium saponite-polymer large temperature difference constant flow variable regulator provided in this embodiment.

[0063] pass Figure 2It can be seen that the thermal decomposition process of the lithium saponite-polymer large temperature difference constant current variable flow regulator at 50–800℃ can be roughly divided into four stages. The temperature decreases slowly before 317.3℃, due to the volatilization of a large amount of adsorbed and bound water, as well as trace monomers and small molecules. From the second stage onwards, the TG curve drops sharply, possibly due to the degradation of the amide bond and the opening of the morpholine ring on the molecular side chain and the breakage of the C / C bonds on the main chain at high temperatures. The TG-DSC curve shows that the lithium saponite-polymer large temperature difference constant current variable flow regulator of this embodiment has excellent thermal stability.

[0064] Example 2

[0065] This embodiment provides a lithium saponite-polymer large temperature difference constant current flow regulator, which is prepared through the following steps:

[0066] (1) Add 3g of nano-lithium saponite to 30mL of acetone solution and ultrasonically disperse for 5min at room temperature (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano-lithium saponite; heat the stable suspension of nano-lithium saponite to 30℃, add 9g of silane coupling agent KH570, continue ultrasonic dispersion, react for 1h to obtain a white solid product, then separate the solid product, wash it 3 times with anhydrous ethanol, and dry it at 65℃ for 12h to obtain 3g of modified nano-lithium saponite;

[0067] (2) Take 8g of N,N-dimethylacrylamide, 15g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of 3-acrylamidopropyl-trimethylammonium chloride, and 5g of 4-acryloylmorpholine, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution.

[0068] (3) Take 3g of the modified nano lithium saponite obtained in step (1) and dissolve it in 10mL of ethanol. Disperse it by ultrasonication for 5min (the power of ultrasonication is 300-600w and the frequency is 20KHz or 28KHz) to obtain the modified nano lithium saponite dispersion. Then add the monomer mixed solution obtained in step (2) and stir to mix evenly to obtain a mixed solution.

[0069] (4) Adjust the pH of the mixture obtained in step (3) to 7 using 30wt% sodium hydroxide solution. Then, transfer the pH-adjusted mixture to a four-necked flask and stir continuously for 0.5h under high-purity nitrogen flow to create a vacuum environment. Heat the mixture from ambient temperature to 70°C using a constant temperature water bath. Then, add 0.15g of azobisisobutyronitrile and react for 4h under vacuum, nitrogen atmosphere, 70°C and in the presence of azobisisobutyronitrile to obtain a white product. Separate the white product and wash it three times with ethanol and acetone to remove unreacted monomers. Then, dry it in an 80°C vacuum oven for 24h. After drying, take it out and pulverize it to obtain the lithium saponite-polymer large temperature difference constant flow modulator of this embodiment.

[0070] Example 3

[0071] This embodiment provides a lithium saponite-polymer large temperature difference constant current flow regulator, which is prepared through the following steps:

[0072] (1) Add 5g of nano lithium saponite to 50mL of acetone solution and ultrasonically disperse for 5min at room temperature (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano lithium saponite; heat the stable suspension of nano lithium saponite to 30℃, add 10g of silane coupling agent KH570, continue ultrasonic dispersion, react for 1h to obtain a white solid product, then separate the solid product, wash it 3 times with anhydrous ethanol, and dry it at 65℃ for 12h to obtain 5g of modified nano lithium saponite;

[0073] (2) Take 8g of acrylamide, 12g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of dimethyldiallylammonium chloride, and 4g of N-vinylcaprolactam, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution.

[0074] (3) Take 5g of the modified nano lithium saponite obtained in step (1) and dissolve it in 10mL of ethanol. Disperse it by ultrasonication for 5min (the power of ultrasonication is 300-600w and the frequency is 20KHz or 28KHz) to obtain the modified nano lithium saponite dispersion. Then add the monomer mixed solution obtained in step (2) and stir to mix evenly to obtain a mixed solution.

[0075] (4) Adjust the pH of the mixture obtained in step (3) to 7 using 30wt% sodium hydroxide solution. Then, transfer the pH-adjusted mixture to a four-necked flask and stir continuously for 0.5h under high-purity nitrogen flow to create a vacuum environment. Heat the mixture from ambient temperature to 70°C using a constant temperature water bath. Then, add 0.15g of azobisisobutyronitrile and react for 6h under vacuum, nitrogen atmosphere, 70°C and in the presence of azobisisobutyronitrile to obtain a white product. Separate the white product and wash it three times with ethanol and acetone to remove unreacted monomers. Then, dry it in an 80°C vacuum oven for 24h. After drying, take it out and pulverize it to obtain the lithium saponite-polymer large temperature difference constant flow modulator of this embodiment.

[0076] Comparative Example 1

[0077] This comparative example provides a polymer flow modifier whose raw material composition does not contain modified nano-lithium saponite, and it is prepared through the following steps:

[0078] (1) Take 8g of acrylamide, 12g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of dimethyldiallylammonium chloride, and 4g of 4-acryloylmorpholine, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution.

[0079] (2) The pH of the monomer mixture obtained in step (1) was adjusted to 7 using 30wt% sodium hydroxide solution. Then, the pH-adjusted monomer mixture was transferred to a four-necked flask and stirred continuously for 0.5h under a high-purity nitrogen flow to create a vacuum environment. The mixture was heated from ambient temperature to 65℃ using a constant temperature water bath. Then, 0.15g of azobisisobutyronitrile was added. The mixture was reacted for 5h under vacuum conditions, nitrogen atmosphere, 65℃ and in the presence of azobisisobutyronitrile to obtain a white product. The white product was separated and washed three times with ethanol and acetone to remove unreacted monomers. The product was then dried in an 80℃ vacuum oven for 24h. After drying, the product was taken out and pulverized to obtain the polymer flow modifier of this comparative example.

[0080] Comparative Example 2

[0081] This comparative example provides a lithium saponite-polymer flow modifier, the raw material composition of which does not contain temperature-sensitive monomers, and it is prepared through the following steps:

[0082] (1) Add 5g of nano lithium saponite to 50mL of acetone solution and ultrasonically disperse for 5min at room temperature (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano lithium saponite; heat the stable suspension of nano lithium saponite to 30℃, add 10g of silane coupling agent KH570, continue ultrasonic dispersion, react for 1h to obtain a white solid product, then separate the solid product, wash it 3 times with anhydrous ethanol, and dry it at 65℃ for 12h to obtain 5g of modified nano lithium saponite;

[0083] (2) Take 8g of acrylamide, 12g of 2-acrylamido-2-methylpropanesulfonic acid and 6g of dimethyldiallylammonium chloride, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution.

[0084] (3) Take 5g of the modified nano lithium saponite obtained in step (1) and dissolve it in 10mL of ethanol. Disperse it by ultrasonication for 5min (the power of ultrasonication is 300-600w and the frequency is 20KHz or 28KHz) to obtain the modified nano lithium saponite dispersion. Then add the monomer mixed solution obtained in step (2) and stir to mix evenly to obtain a mixed solution.

[0085] (4) Adjust the pH of the mixture obtained in step (3) to 7 using 30wt% sodium hydroxide solution. Then, transfer the pH-adjusted mixture to a four-necked flask and stir continuously for 0.5h under a high-purity nitrogen flow to create a vacuum environment. Heat the mixture from ambient temperature to 65℃ using a constant temperature water bath. Then, add 0.15g of azobisisobutyronitrile and react for 5h under vacuum conditions, nitrogen atmosphere, 65℃ and in the presence of azobisisobutyronitrile to obtain a white product. Separate the white product and wash it three times with ethanol and acetone to remove unreacted monomers. Then, dry it in an 80℃ vacuum oven for 24h. After drying, take it out and pulverize it to obtain the lithium saponite-polymer flow modifier of this comparative example.

[0086] Comparative Example 3

[0087] This comparative example provides a lithium saponite-polymer flow modifier, the raw material composition of which does not contain cationic monomers, and it is prepared through the following steps:

[0088] (1) Add 5g of nano lithium saponite to 50mL of acetone solution and ultrasonically disperse for 5min at room temperature (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano lithium saponite; heat the stable suspension of nano lithium saponite to 30℃, add 10g of silane coupling agent KH570, continue ultrasonic dispersion, react for 1h to obtain a white solid product, then separate the solid product, wash it 3 times with anhydrous ethanol, and dry it at 65℃ for 12h to obtain 5g of modified nano lithium saponite;

[0089] (2) Take 8g of acrylamide, 12g of 2-acrylamido-2-methylpropanesulfonic acid and 4g of 4-acryloylmorpholine, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution;

[0090] (3) Take 5g of the modified nano lithium saponite obtained in step (1) and dissolve it in 10mL of ethanol. Disperse it by ultrasonication for 5min (the power of ultrasonication is 300-600w and the frequency is 20KHz or 28KHz) to obtain the modified nano lithium saponite dispersion. Then add the monomer mixed solution obtained in step (2) and stir to mix evenly to obtain a mixed solution.

[0091] (4) Adjust the pH of the mixture obtained in step (3) to 7 using 30wt% sodium hydroxide solution. Then, transfer the pH-adjusted mixture to a four-necked flask and stir continuously for 0.5h under a high-purity nitrogen flow to create a vacuum environment. Heat the mixture from ambient temperature to 65℃ using a constant temperature water bath. Then, add 0.15g of azobisisobutyronitrile and react for 5h under vacuum conditions, nitrogen atmosphere, 65℃ and in the presence of azobisisobutyronitrile to obtain a white product. Separate the white product and wash it three times with ethanol and acetone to remove unreacted monomers. Then, dry it in an 80℃ vacuum oven for 24h. After drying, take it out and pulverize it to obtain the lithium saponite-polymer flow modifier of this comparative example.

[0092] Comparative Example 4

[0093] This comparative example provides a lithium saponite-polymer large temperature difference constant flow modulator, in which the temperature-sensitive monomer is replaced with the polyene monomer divinylbenzene, and it is prepared through the following steps:

[0094] (1) Add 5g of nano-lithium saponite to 50mL of acetone and ultrasonically disperse for 5min at room temperature (ultrasonic power of 300-600w, frequency of 20KHz or 28KHz) to form a stable suspension of nano-lithium saponite; heat the stable suspension of nano-lithium saponite to 30℃, add 2.5g of silane coupling agent KH570, continue ultrasonic dispersion, react for 1h to obtain a white solid product, then separate the solid product, wash it 3 times with anhydrous ethanol, and dry it at 65℃ for 12h to obtain 5g of modified nano-lithium saponite;

[0095] (2) Take 30g of acrylamide, 20g of 2-acrylamido-2-methylpropanesulfonic acid, 2g of dimethyldiallylammonium chloride, and 0.2g of divinylbenzene, add them to 70mL of deionized water, stir and mix to dissolve, and obtain a monomer mixed solution;

[0096] (3) Take 5g of the modified nano lithium saponite obtained in step (1) and dissolve it in 10mL of ethanol. Disperse it by ultrasonication for 5min (the power of ultrasonication is 300-600w and the frequency is 20KHz or 28KHz) to obtain the modified nano lithium saponite dispersion. Then add the monomer mixed solution obtained in step (2) and stir to mix evenly to obtain a mixed solution.

[0097] (4) Adjust the pH of the mixture obtained in step (3) to 7 using 30wt% sodium hydroxide solution. Then, transfer the pH-adjusted mixture to a four-necked flask and stir continuously for 0.5h under high-purity nitrogen flow to create a vacuum environment. Heat the mixture from ambient temperature to 65℃ using a constant temperature water bath. Then, add 0.15g of azobisisobutyronitrile and react for 5h under vacuum, nitrogen atmosphere, 65℃ and in the presence of azobisisobutyronitrile to obtain a white product. Separate the white product and wash it three times with ethanol and acetone to remove unreacted monomers. Then, dry it in an 80℃ vacuum oven for 24h. After drying, take it out and pulverize it to obtain the lithium saponite-polymer large temperature difference constant flow modulator of this comparative example.

[0098] The flow pattern regulators provided in Examples 1, 2, and 3, and Comparative Examples 1, 2, 3, and 4 were subjected to performance tests using the following experimental methods.

[0099] 1. Low-temperature rheological property testing

[0100] Preparation of 4% bentonite freshwater-based slurry: Take 400mL of tap water into a high-speed stirring cup, add 16.0g of API standard evaluation soil under high-speed stirring at 5000r / min, stir at high speed for 20min, and cure in a sealed container at room temperature for 24h.

[0101] 0.5 wt% (based on the mass of water in the 4% bentonite brine-based slurry being 100%) of the flow pattern modifier to be tested was added to the above-mentioned 4% bentonite brine-based slurry. The slurry was aged at 150℃ for 16 hours using a roller furnace. The rheological parameters of the drilling fluid at 4-60℃ were tested according to GB / T29170-2012 "Laboratory Testing of Drilling Fluids for Petroleum and Natural Gas Industry". The results are shown in Table 1 below.

[0102] Table 1. Low-temperature rheological properties results

[0103]

[0104]

[0105] As shown in Table 1, the aged bentonite-based slurry exhibits slightly lower viscosity, shear stress, and initial / final shear rates, failing to effectively form a bentonite drilling fluid system with good rheological properties. However, the drilling fluid containing the flow modifiers from Examples 1-3 shows improved viscosity, shear stress, and initial / final shear rates after aging. Furthermore, the drilling fluid containing the flow modifiers from Examples 1-3 shows minimal changes in AV, PV, and YP from 4°C to 60°C, indicating that the flow modifiers provided in the examples have good constant rheological effects at lower temperatures. This demonstrates that the flow modifier of the present invention can stabilize the rheological properties of drilling fluid at low temperatures, which is beneficial for suspension and cuttings carrying, and helps reduce drilling risks such as wellbore instability, collapse, and diameter reduction. In contrast, the flow modifiers provided in the comparative examples do not show significant constant rheological effects. Comparative Example 1 did not contain nano-lithium saponite, and no network structure was formed between molecules, resulting in significant low-temperature thickening side effects; Comparative Example 2 did not contain a thermosensitive monomer, and could not synergize with other monomers to produce a thermosensitive effect, resulting in weak low-temperature compensation performance and poor temperature stability; Comparative Example 3 did not contain a cationic monomer, but had little impact on the stability of rheological properties at low temperatures; Comparative Example 4 did not contain a thermosensitive monomer, and could not produce a thermosensitive effect, resulting in weak low-temperature compensation performance.

[0106] 2. Temperature resistance test

[0107] Preparation of 4% bentonite freshwater-based slurry: Take 400mL of tap water into a high-speed stirring cup, add 16.0g of API standard evaluation soil under high-speed stirring at 5000r / min, stir at high speed for 20min, and cure in a sealed container at room temperature for 24h.

[0108] 2 wt% (based on the mass of water in the 4% bentonite brine-based slurry being 100%) of the flow pattern modifier to be tested was added to the above-mentioned 4% bentonite fresh water-based slurry. The slurry was aged for 16 hours at 150℃, 180℃, and 200℃ using a roller furnace. The rheological parameters and API filtration loss of the drilling fluid were tested according to GB / T 29170-2012 "Laboratory Testing of Drilling Fluids for Petroleum and Natural Gas Industry". The results are shown in Table 2 below.

[0109] Table 2 Temperature resistance performance results

[0110]

[0111]

[0112] As shown in Table 2, the addition of the flow modifier of this invention to 4% freshwater-based slurry, after aging at 150℃ / 16h, 180℃ / 16h, and 200℃ / 16h, significantly improved the rheological properties of the bentonite-based slurry. Furthermore, the viscosity, shear stress, and filtration properties remained relatively stable with increasing temperature, demonstrating good temperature resistance. This is because the flow modifier of this invention incorporates inorganic nano-lithium saponite combined with the polymer. Nano-lithium saponite possesses excellent temperature resistance, does not decompose due to temperature, and acts as a "crosslinking agent," copolymerizing with monomers to form a network structure that enhances temperature resistance. The molecular chain also contains cyclic rigid monomers. Moreover, hydrogen bonding and electrostatic adsorption allow the flow modifier to form a stable structure with bentonite particles, all of which enhance the temperature resistance of the flow modifier. Comparative Example 1 lacked nano-lithium saponite, thus failing to form a spatial network structure and lacking anchoring for the polymer. Although it had a strong ability to enhance rheology, its temperature resistance was poor. Comparative Example 2 lacked temperature-sensitive monomers, thus lacking the inhibition of molecular chains by cyclic rigid monomers, resulting in a decrease in temperature resistance. Comparative Example 3 lacked cationic monomers, which weakened the electrostatic adsorption with bentonite particles, resulting in weakened structural stability and insufficient temperature resistance. Comparative Example 4, although lacking temperature-sensitive monomers, contained polyene monomers that enhanced the cross-linking structure of the flow regulator, thereby improving temperature resistance to some extent.

[0113] 3. Salt resistance test

[0114] Preparation of 4% bentonite brine-based slurry: Take 400 mL of tap water into a high-speed stirring cup, add 16.0 g of API standard evaluation soil and 60 g of NaCl (15 wt%) under high-speed stirring at 5000 r / min, stir at high speed for 20 min, and cure in a sealed container at room temperature for 24 h.

[0115] 2 wt% (based on the mass of water in the 4% bentonite brine-based slurry being 100%) of the flow pattern modifier to be tested was added to the above-mentioned 4% bentonite brine-based slurry. The slurry was aged at 150℃ for 16 hours using a roller furnace. The rheological parameters of the drilling fluid were tested according to GB / T29170-2012 "Laboratory Testing of Drilling Fluids for Petroleum and Natural Gas Industry". The results are shown in Table 3 below.

[0116] Table 3 Salt tolerance results

[0117]

[0118]

[0119] As shown in Table 3, under a bentonite brine-based slurry environment with a 15% salt concentration, after aging at 150℃ for 16 hours, compared to Comparative Examples 1-4, the flow modifiers of Examples 1-3 effectively improved the apparent viscosity, plastic viscosity, and dynamic shear force of the bentonite brine-based slurry. They also improved the initial and final shear rates, indicating that the lithium saponite-polymer large-temperature-difference constant-flow flow modifier of this invention has good salt resistance. This is because the flow modifier of this invention is composed of lithium saponite-polymer with a spatial network structure, which suppresses the influence of electrolytes on the coiling of polymer molecular chains. Furthermore, it contains cations, forming intramolecular ionic bonds that resist external electrolyte ions. This demonstrates that the lithium saponite-polymer large-temperature-difference constant-flow flow modifier of this invention is suitable for certain saline formations.

[0120] 4. Hydrate Inhibition Performance Test

[0121] System preparation: Take 100 mL of distilled water into a beaker, add 0.5 wt% of the flow pattern regulator to be tested while stirring with a magnetic stirrer, and stir for 30 min until fully dissolved.

[0122] The hydrate formation simulation experiment apparatus was used to determine the hydrate induction time using a generalized method, i.e., the time from the start of the experiment to the appearance of hydrate crystal particles in the system (or a sudden drop in system pressure). The prepared system was added to the fully transparent reactor of the hydrate formation simulation experiment apparatus, and CH4 was injected under vacuum. The initial temperature / pressure conditions were set to 2.4℃ and 6.0MPa, with a mechanical stirring speed of 600rpm. The effect of the flow pattern regulators of Examples 1-3 and Comparative Examples 1-4 on the hydrate inhibition performance was evaluated by measuring the hydrate formation induction time of the system. The results are as follows: Figure 3 As shown.

[0123] from Figure 3The results showed that the hydrate induction time in distilled water was 19.25 min. However, after adding 0.5 wt% of the flow pattern regulators from Examples 1 to 3 to distilled water, the hydrate induction time was extended to over 380 min. This indicates that the flow pattern regulators of the present invention have a significant delaying effect on hydrate formation and can inhibit hydrate nucleation and growth. The 0.5 wt% flow pattern regulator of Comparative Example 1 extended the hydrate induction time by no more than 100 min, and the inhibitory effect was not significant. The 0.5 wt% flow pattern regulators of Comparative Examples 2 to 3 also extended the hydrate induction time, indicating an improved inhibitory effect. Comparative Example 1, which did not contain nano-lithium saponite, had no significant delaying effect on the hydrate induction time. Other lithium saponite-polymer flow pattern regulators containing nano-lithium saponite had a binding effect on water molecules, delaying the formation of the hydrate cage structure, thereby extending the induction time, which is reflected in the inhibition of hydrate nucleation and growth. Among them, Comparative Example 4 had a strong cross-linking structure, and the polymer layer formed a strong coating on the nano-lithium saponite, resulting in a decreased inhibitory effect.

[0124] In summary, the lithium saponite-polymer large temperature difference constant flow modifiers of Examples 1-3 of this invention have stable drilling fluid rheological properties over a large temperature difference range, and have good temperature and salt resistance and the ability to inhibit hydrate nucleation and growth. They can be used under complex temperature conditions, which helps to improve the drilling fluid suspension and cuttings carrying capacity, thereby reducing downhole complications such as solid phase sedimentation, wellbore instability, collapse and narrowing, and stuck pipe.

Claims

1. A lithium saponite-polymer large temperature difference constant flow variable flow regulator, comprising, by weight, the following raw materials: 2-5 parts of nano lithium saponite, 4-10 parts of silane coupling agent, 8-12 parts of monomer containing adsorption groups, 10-15 parts of anionic monomer, 5-8 parts of cationic monomer, 2-5 parts of thermosensitive monomer, and 0.14-0.18 parts of initiator; in, The monomers containing adsorption groups include acrylamide and / or N,N-dimethylacrylamide; The anionic monomer includes one or a combination of several of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, sodium vinylsulfonate, and styrene. The cationic monomer includes one or a combination of several of dimethyl diallyl ammonium chloride, 3-acrylamidopropyl-trimethyl ammonium chloride, and methacryloyloxyethyltrimethyl ammonium chloride; The temperature-sensitive monomer includes one or a combination of several of N-vinylcaprolactam, 4-acryloylmorpholine, N-isopropylacrylamide, N,N-diethylacrylamide, and diacetoneacrylamide.

2. The lithium saponite-polymer large temperature difference constant current converter according to claim 1, wherein, The average thickness of the nano-lithium saponite is 1nm-10nm, and the average diameter is 25nm-50nm.

3. The lithium saponite-polymer large temperature difference constant current converter according to claim 1, wherein, The silane coupling agent includes one or a combination of several of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

4. The lithium saponite-polymer large temperature difference constant current variable flow regulator according to claim 1, wherein, The initiator includes one or a combination of several of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

5. A method for preparing a lithium saponite-polymer large temperature difference constant current converter according to any one of claims 1-4, comprising the following steps: (1) According to the weight, 2-5 parts of nano lithium saponite and 4-10 parts of silane coupling agent are mixed in the first solvent, reacted for a period of time, and then separated, washed and dried to obtain modified nano lithium saponite. (2) Mix 8-12 parts of monomer containing adsorption groups, 10-15 parts of anionic monomer, 5-8 parts of cationic monomer and 2-5 parts of thermosensitive monomer in a second solvent to obtain a monomer mixed solution; (3) Disperse the modified nano-lithium saponite obtained in step (1) in a third solvent to obtain a modified nano-lithium saponite dispersion; then mix the modified nano-lithium saponite dispersion with the monomer mixed solution obtained in step (2) to obtain a mixed solution; (4) After adjusting the pH value of the mixture obtained in step (3), react it for a period of time under a nitrogen atmosphere, at a certain temperature and in the presence of 0.14-0.18 parts of initiator. Then, after separation, washing and drying, the lithium saponite-polymer large temperature difference constant flow variable flow regulator is obtained.

6. The preparation method according to claim 5, wherein, Step (1) involves mixing and reacting the nano-lithium saponite and the silane coupling agent in a first solvent using ultrasonic dispersion.

7. The preparation method according to claim 6, wherein, The power of ultrasound is 300-600W, and the frequency is 20KHz or 28KHz.

8. The preparation method according to claim 5, wherein, The reaction temperature in step (1) is 25-35℃ and the reaction time is 0.5-1h.

9. The preparation method according to claim 5, wherein, The drying temperature in step (1) is 50-70℃ and the drying time is 8-12h.

10. The preparation method according to claim 5, wherein, The first solvent in step (1) is an organic solvent; the first solvent includes one or a combination of acetone, petroleum ether, diethyl ether and toluene; the ratio of the first solvent to the nano lithium soapstone is 10 mL: (1-2) g.

11. The preparation method according to claim 5, wherein, The second solvent in step (2) includes water; the ratio of the second solvent to all monomers is 10 mL: (2-5) g.

12. The preparation method according to claim 5, wherein, Step (3) involves dispersing the modified nano-lithium soapstone in a third solvent using ultrasonic dispersion for 5-10 minutes to obtain the modified nano-lithium soapstone dispersion.

13. The preparation method according to claim 12, wherein, The power of ultrasound is 300-600W, and the frequency is 20KHz or 28KHz.

14. The preparation method according to claim 5, wherein, The third solvent in step (3) includes ethanol; the ratio of the third solvent to the modified nano lithium soapstone is (2-6) mL: 1 g.

15. The preparation method according to claim 5, wherein, In step (4), the pH of the mixture obtained in step (3) is adjusted to 6.0-8.

0.

16. The preparation method according to claim 15, wherein, In step (4), the pH value of the mixture is adjusted using sodium hydroxide solution.

17. The preparation method according to claim 5, wherein, In step (4), the reaction is carried out for 4-6 hours under a nitrogen atmosphere, at 60-75°C and in the presence of 0.14-0.18 parts of initiator.

18. The preparation method according to claim 5, wherein, The drying temperature in step (4) is 70-80℃ and the drying time is 12-24h.

19. The application of any one of claims 1-4 of the lithium saponite-polymer large temperature difference constant flow variable flow regulator in natural gas hydrate drilling fluid.

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