Thixotropic rheological modifier for temperature-resistant water-based drilling fluid and preparation and application thereof

Abstract

The application provides a kind of thixotropic rheological modifier for temperature-resistant water-based drilling fluid and its preparation and application, and belongs to the technical field of oilfield drilling.The rheological modifier is prepared from the following raw materials: 2-acrylamido-2-methylpropane sulfonic acid, N,N-dimethyl acrylamide, octadecyl acrylate, 3-acrylamidophenylboronic acid, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methyl acrylamide, salting-out agent, initiator, deionized water, ethanol and methanol.When the drilling fluid experiences high shear rate at the water eye of the drill bit, the rheological modifier can sharply reduce the viscosity of the drilling fluid, greatly enhance the fluidity and prevent the water eye of the drill bit from being blocked.When the drilling fluid leaves the high shear zone and enters the annular low-speed zone or is completely static, the rheological modifier forms a high-strength network to tightly wrap and fix the solid particles in the drilling fluid, achieving efficient suspension and effectively preventing settling and sticking of the drill pipe.

Description

Technical Field

[0001] This invention relates to a thixotropic rheology modifier for heat-resistant water-based drilling fluids, its preparation and application, and belongs to the field of oilfield drilling technology. Background Technology

[0002] As oil and gas exploration and development extend into deeper formations, drilling operations face severe challenges such as high temperatures and high pressures, placing higher demands on drilling fluid performance. On the one hand, higher formation pressures require drilling fluids to be weighted to higher densities, necessitating good suspension capabilities for the weighting materials. On the other hand, due to limitations in current drilling technology, the upper sections of ultra-deep wells often require larger wellbore sizes to ensure the normal drilling of the lower sections. This results in larger cuttings and wellbore fragments at the same wellbore enlargement rate, demanding better cuttings carrying capacity from the drilling fluid. Cutting-lifting rheology modifiers are key agents for addressing these issues. However, existing traditional cutting-lifting rheology modifiers based on polymers (such as polyanionic cellulose and xanthan gum) or clay minerals often increase the viscosity of the drilling fluid while improving its suspension and cuttings carrying capacity. Large dosages can easily clog the drill bit's water channels, while small dosages are prone to failure at high temperatures, leading to problems such as insufficient static suspension capacity and poor rheological properties after high-temperature aging. This has become a long-standing contradiction: in high-shear areas downhole (such as drill bit water holes), low viscosity needs to be maintained to ensure smooth fluid flow and reduce pressure loss; while in low-shear or stagnant annular areas, a high-strength grid structure needs to be quickly established to effectively suspend cuttings and prevent settling and stuck drill bits.

[0003] Chinese patent document CN 120737821 A discloses a water-based drilling fluid for solidifying and preventing leakage in deep wells at depths of 10,000 meters, its preparation method and application, which involves a salt-responsive rheology modifier, which is copolymerized from acrylamide, 3-[(3-acrylamidopropyl)dimethylammonium]propane-1-sulfonate, a hydrophobic monomer (the hydrophobic monomer is octadecyl vinyl ether or dodecyl vinyl ether), and a rigid cyclic monomer (N-vinylcaprolactam, N-vinylpyrrolidone, 4-acryloylmorpholine or 4-vinylpyridine). The polymer possesses rigid isopropyl, sulfonic acid, long alkyl chains, and nitrogen-containing heterocycles, exhibiting strong temperature resistance and resistance to degradation at high temperatures. The 3-[(3-acrylamidopropyl)dimethylammonium]propane-1-sulfonate, containing a betaine structure, imparts anti-polyelectrolyte properties to the polymer, allowing the polymer chains to fully extend under high-temperature and high-salt conditions, increasing its hydrodynamic volume. The hydrophobic long alkyl chains form an associative structure, synergistically constructing a robust and dense three-dimensional cross-linked network with the clay, preventing the electrolyte from damaging the drilling fluid network structure. This ensures the drilling fluid maintains stable viscosity and shear force under high-temperature and high-salt conditions, facilitating the suspension of cuttings and cleaning of the wellbore, thus guaranteeing efficient drilling. However, it still cannot resolve the aforementioned long-standing contradictions and cannot reversibly regulate its own network structure under changes in external shear force.

[0004] Therefore, developing a novel high-temperature and high-salt rheology modifier with intelligent response characteristics that can reversibly adjust its own network structure under changes in external shear force to solve the above contradictions has become an urgent need for the current development of drilling fluid technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a thixotropic rheology modifier for high-temperature water-based drilling fluids, along with its preparation and application. The rheology modifier of this invention is a "smart" polymer with shear-responsive properties. In drilling fluids, it forms a three-dimensional network structure that can reversibly break and regenerate in response to changes in external force fields through dynamic covalent chemical bonds and hydrophobic association. When the drilling fluid experiences high shear rates at points such as the drill bit's waterholes, the rheology modifier of this invention can drastically reduce the fluid viscosity, significantly enhance fluidity, and prevent blockage of the drill bit's waterholes. When the drilling fluid leaves the high-shear zone and enters the low-velocity annulus zone or becomes completely still, the rheology modifier reforms a high-strength network that firmly encapsulates and fixes solid particles (barite, rock cuttings) in the drilling fluid, achieving efficient suspension and effectively preventing drilling accidents such as settling and stuck pipe. The rheology modifier of this invention is resistant to temperatures above 220°C, saturated salts, and exhibits good compatibility with various water-based drilling fluid systems.

[0006] This invention is achieved through the following technical solution:

[0007] A thixotropic rheology modifier for hot-temperature water-based drilling fluids is prepared from the following raw materials in parts by weight:

[0008] 5-20 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5-15 parts of N,N-dimethylacrylamide, 0.1-2 parts of octadecyl acrylate, 0.5-2 parts of 3-acrylamidophenylboronic acid, 0.5-3 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 15-25 parts of salting-out agent, 1-8 parts of initiator, 100-140 parts of deionized water, 5-15 parts of ethanol, and 5-15 parts of methanol.

[0009] According to a preferred embodiment of the present invention, the thixotropic rheology modifier for heat-resistant water-based drilling fluid is prepared from the following raw materials in parts by weight:

[0010] 10-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8-10 parts of N,N-dimethylacrylamide, 0.5-1.5 parts of octadecyl acrylate, 1-1.5 parts of 3-acrylamidophenylboronic acid, 1-2 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent, 3-5 parts of initiator, 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol.

[0011] Preferably, the thixotropic rheology modifier for heat-resistant water-based drilling fluid is prepared from the following raw materials in parts by weight:

[0012] 12-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 9-10 parts of N,N-dimethylacrylamide, 1-1.5 parts of octadecyl acrylate, 1.2-1.5 parts of 3-acrylamidophenylboronic acid, 1.5-2 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent, 4-5 parts of initiator, 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol.

[0013] According to a preferred embodiment of the present invention, the salting-out agent is NaCl. The function of the salting-out agent is to promote the precipitation of the polymer after the reaction is completed. Without the addition of the salting-out agent, the precipitation rate is slow and the precipitation may be incomplete. The addition of the salting-out agent has no significant effect on the performance of the rheology modifier, but it can improve the production rate and yield.

[0014] According to a preferred embodiment of the present invention, the initiator is an aqueous solution of ammonium persulfate with a mass concentration of 5-15 wt% and an aqueous solution of sodium bisulfite with a mass concentration of 5-15 wt%; the mass ratio of the aqueous solution of ammonium persulfate to the aqueous solution of sodium bisulfite is 2-3:1-2.

[0015] The preparation method of the above-mentioned thixotropic rheology modifier for heat-resistant water-based drilling fluid includes the following steps:

[0016] (1) Dissolve 2-acrylamido-2-methylpropanesulfonic acid completely in deionized water, adjust the pH to 7.0-8.0 with sodium hydroxide aqueous solution with a mass concentration of 40-60%, add N,N-dimethylacrylamide, dissolve completely to obtain pre-dissolved solution 1;

[0017] (2) Dissolve octadecyl acrylate completely in ethanol to obtain pre-dissolved solution 2;

[0018] (3) Dissolve 3-acrylamidophenylboronic acid completely in methanol to obtain pre-dissolved solution 3;

[0019] (4) Under the protection of protective gas, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide is fully dissolved in deionized water, and pre-dissolving solution 1, pre-dissolving solution 2 and pre-dissolving solution 3 are added, followed by the addition of salting-out agent; the temperature is raised, an initiator is added, and after reaction, the solution is precipitated, filtered, washed, dried and pulverized to obtain a thixotropic rheology modifier for water-based drilling fluid with temperature resistance.

[0020] According to a preferred embodiment of the present invention, the mass ratio of deionized water in step (1) to deionized water in step (4) is 4-6:1.

[0021] According to a preferred embodiment of the present invention, in step (4), the protective gas is nitrogen or argon; the temperature is raised to 30-40°C; the reaction conditions are as follows: under nitrogen or argon protection, the stirring reaction is initiated at 30-40°C until the system becomes viscous, and the temperature is raised to 40-45°C and the stirring reaction is carried out for 6-8 hours.

[0022] According to a preferred embodiment of the present invention, in step (4), the precipitation method is as follows: the reaction solution is added to ethanol, stirred for 5-15 min and then allowed to stand for 10-30 min to allow the polymer to precipitate completely.

[0023] The aforementioned thixotropic rheology modifier for water-based drilling fluids is applied in water-based drilling fluids. This invention's strong thixotropic rheology modifier, through dynamic covalent chemical bonds and hydrophobic association, enables drilling fluid to flow normally under high shear without clogging the drill bit's water channels, and efficiently lift suspended cuttings under low shear. This effectively resolves the contradiction between drilling fluid flowability and cuttings carrying capacity in practical engineering, improving the actual application effect of drilling fluids.

[0024] According to a preferred embodiment of the present invention, the mass of the rheology modifier is 1-5 wt% of the mass of the drilling fluid.

[0025] The technical features and beneficial effects of this invention are as follows:

[0026] 1. The strong thixotropic rheology modifier for ultra-high temperature water-based drilling fluid of the present invention is a "smart" polymer with shear response characteristics. It can form a three-dimensional network structure in drilling fluid through dynamic covalent chemical bonds and hydrophobic association physical interaction, which can reversibly break and regenerate with changes in external force field. When drilling fluid experiences high shear rates at the drill bit's waterholes, the "Hook and loop" bonds connecting polymer chains via borate ester bonds (dynamic covalent bonds) undergo reversible breakage. Simultaneously, the associated micro-regions formed by hydrophobic groups temporarily dissociate, and the physical "clamps" loosen. The polymer molecules mainly exist as independent, highly oriented linear chains, reducing friction and internal losses between them. This leads to a sharp decrease in drilling fluid viscosity and a significant increase in fluidity, preventing blockage of the drill bit's waterholes. When the drilling fluid leaves the high-shear zone and enters the low-velocity annulus zone or becomes completely still, the borate and catechol groups on the rheology modifier molecular chains collide with each other due to molecular thermal motion. With an extremely high reaction rate, they rapidly recombine to form borate ester bonds. At the same time, the hydrophobic groups re-aggregate to form hydrophobic micro-regions, restoring physical cross-linking points and reforming a high-strength network that firmly encapsulates and fixes solid particles (barite, cuttings) in the drilling fluid, achieving efficient suspension and effectively preventing drilling accidents such as settling and stuck pipe.

[0027] 2. The strong thixotropic rheology modifier for ultra-high temperature water-based drilling fluids of the present invention features an ingeniously designed molecular structure. By optimizing the monomer types, ratios, and controlling the synthesis conditions, a polymer with dynamic covalent bonds and hydrophobic association structures, and excellent water solubility, was obtained. Unlike conventional poorly water-soluble dynamic covalent polymer gels, the rheology modifier of the present invention can be fully dispersed in water-based drilling fluids, altering the overall rheological properties of the drilling fluid and thus enhancing its effectiveness.

[0028] 3. This invention provides a strong thixotropic rheology modifier for ultra-high temperature water-based drilling fluids, resistant to temperatures above 220℃ and saturated salts. It exhibits good compatibility with various water-based drilling fluid systems, and the dosage can be adjusted according to actual engineering needs to achieve suitable rheological properties in the drilling fluid. The rheology modifier of this invention operates under mild reaction conditions, allowing for large-scale industrial production. The production process does not generate toxic or hazardous waste, and the raw materials, intermediate products, and final products all possess good environmental compatibility, enabling its widespread use in various regions.

[0029] 4. The rheology modifier with excellent effects of the present invention is obtained by combining specific types of monomers in specific ratios; if the types and ratios of monomers are not suitable, or if a certain monomer is omitted, the performance of the obtained rheology modifier will be reduced. Attached Figure Description

[0030] Figure 1 Infrared spectrum of the rheology modifier prepared in Example 3;

[0031] Figure 2 Photographs of drilling fluids F3 (a) and DF4 (b) after adding 4-10 mesh sandstone cuttings and allowing them to stand for 20 minutes after aging. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described below. The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the embodiments are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims.

[0033] Unless otherwise specified, all materials used in the following examples and comparative examples are commercially available, and all methods used are conventional methods in the art.

[0034] Example 1

[0035] A highly thixotropic rheology modifier A1 for ultra-high temperature water-based drilling fluids is prepared from the following raw materials in parts by weight:

[0036] 12 parts of 2-acrylamido-2-methylpropanesulfonic acid, 9 parts of N,N-dimethylacrylamide, 1 part of octadecyl acrylate, 1.2 parts of 3-acrylamidophenylboronic acid, 1.5 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent NaCl, 4 parts of initiator (2.5 parts of 10wt% ammonium persulfate aqueous solution and 1.5 parts of 10wt% sodium bisulfite aqueous solution), 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol.

[0037] The preparation method of the above-mentioned strong thixotropic rheology modifier A1 for ultra-high temperature water-based drilling fluid includes the following steps:

[0038] (1) Add 2-acrylamido-2-methylpropanesulfonic acid to 100 parts of deionized water, stir until completely dissolved, then use 50% sodium hydroxide aqueous solution to adjust the pH of the solution to 7.0-8.0, then add N,N-dimethylacrylamide, stir until completely dissolved, and obtain pre-dissolved solution 1.

[0039] (2) Take anhydrous ethanol, add octadecyl acrylate to it, and stir until completely dissolved to obtain pre-dissolved solution 2.

[0040] (3) Take methanol, heat it to 45°C, add 3-acrylamidophenylboronic acid to it, stir until completely dissolved, and obtain pre-dissolved solution 3.

[0041] (4) Add 20 parts of deionized water to a three-necked flask equipped with a mechanical stirrer and a nitrogen inlet tube, then add N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, and stir with nitrogen until completely dissolved. Adjust the speed to 9000 rpm, keep nitrogen flowing, and add pre-dissolved solutions 1, 2 and 3 in sequence, then add the salting-out agent NaCl, transfer to a water bath and heat to 35°C, adjust the speed to 400 rpm, then add the initiator to initiate the reaction. After observing that the reaction system becomes viscous, raise the temperature to 43°C and continue stirring for 7 hours.

[0042] (5) After the reaction, the viscous paste product obtained is poured into anhydrous ethanol, stirred at 1000 rpm for 10 min, and then allowed to stand for 20 min until the polymer is completely precipitated. Then, the product is filtered and the filter cake is washed three times with anhydrous ethanol. The obtained polymer is placed in a vacuum oven at 60℃ and dried for 24 h. The powder obtained after pulverizing the dried solid is the strong thixotropic rheology modifier A1 for ultra-high temperature water-based drilling fluid.

[0043] Example 2

[0044] A highly thixotropic rheology modifier A2 for ultra-high temperature water-based drilling fluids is prepared from the following raw materials in parts by weight:

[0045] 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8 parts of N,N-dimethylacrylamide, 0.5 parts of octadecyl acrylate, 1 part of 3-acrylamidophenylboronic acid, 1 part of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent NaCl, 3 parts of initiator (2 parts of 10wt% ammonium persulfate aqueous solution and 1 part of 10wt% sodium bisulfite aqueous solution), 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol.

[0046] The preparation method of the above-mentioned strong thixotropic rheology modifier A2 for ultra-high temperature water-based drilling fluid is the same as that in Example 1.

[0047] Example 3

[0048] A highly thixotropic rheology modifier A3 for ultra-high temperature water-based drilling fluids is prepared from the following raw materials in parts by weight:

[0049] 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of N,N-dimethylacrylamide, 1.5 parts of octadecyl acrylate, 1.5 parts of 3-acrylamidophenylboronic acid, 2 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent NaCl, 5 parts of initiator (3 parts of 10wt% ammonium persulfate aqueous solution and 2 parts of 10wt% sodium bisulfite aqueous solution), 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol.

[0050] The preparation method of the above-mentioned strong thixotropic rheology modifier A3 for ultra-high temperature water-based drilling fluid is the same as in Example 1.

[0051] The infrared spectrum of the rheology modifier prepared in this embodiment is shown below. Figure 1 As shown, 3400 cm -1 The broad absorption peak at 2850 cm⁻¹ is attributed to the superposition of OH and NH stretching vibrations, indicating the presence of hydrogen bonds and secondary and tertiary amides; -1 Up to 2920 cm -1 The characteristic peaks at 1650 cm⁻¹ represent both asymmetric and symmetric CH stretching vibrations, indicating the presence of hydrophobic long carbon chains. -1 The peak at 1550 cm⁻¹ is a characteristic peak of C=O stretching vibration. -1 The characteristic peak at 1040 cm⁻¹ is a superposition of NH bending vibration and CN stretching vibration, indicating the presence of an amide group; -1 The peak at 1350 cm⁻¹ is a characteristic peak of the S=O asymmetric stretching vibration, indicating the presence of sulfonic acid groups; -1 and 650 cm -1The peaks at points 1 and 2 represent characteristic peaks of BO stretching and out-of-plane bending vibrations, respectively, indicating the presence of phenylboronic acid groups. The characteristic peaks of the marker groups of each monomer are visible in the infrared spectrum, indicating that the product is consistent with the design.

[0052] Comparative Example 1

[0053] A rheology modifier DA1 is as described in Example 1, except that ethanol and octadecyl acrylate are not added; the composition of other raw materials is the same as in Example 1.

[0054] The preparation method of the above rheology modifier is as described in Example 1, except that step (2) of preparing the pre-dissolving solution 2 is omitted, and step (4) does not add the pre-dissolving solution 2; the other steps and conditions are the same as in Example 1. Rheology modifier DA1 is obtained.

[0055] Comparative Example 2

[0056] A rheology modifier DA2 is as described in Example 1, except that methanol and 3-acrylamidophenylboronic acid are not added; the composition of other raw materials is the same as in Example 1.

[0057] The preparation method of the above rheology modifier is as described in Example 1, except that step (3) of preparing the pre-dissolving solution 3 is omitted, and step (4) does not add the pre-dissolving solution 3; the other steps and conditions are the same as in Example 1. Rheology modifier DA2 is obtained.

[0058] Comparative Example 3

[0059] A rheology modifier DA3 is as described in Example 1, except that N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide is not added; the composition of other raw materials is the same as in Example 1.

[0060] The preparation method of the above rheology modifier is as described in Example 1, except that N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide is not added in step (4); other steps and conditions are the same as in Example 1. Rheology modifier DA3 is obtained.

[0061] Comparative Example 4

[0062] A rheology modifier DA4, with the same raw material composition as in Example 1.

[0063] The preparation method of the above rheology modifier is as described in Example 1, except that in step (4), after adding the salting-out agent NaCl, the mixture is transferred to a water bath and heated directly to 43°C, with the rotation speed adjusted to 400 rpm. Then, an initiator is added to initiate the reaction. After observing that the reaction system becomes viscous, the reaction is stirred for another 7 hours. Other steps and conditions are the same as in Example 1.

[0064] Comparative Example 5

[0065] A rheology modifier DA5 is described in Example 1, except that octadecyl acrylate is replaced with an equal amount of butyl acrylate. The composition of other raw materials is the same as in Example 1.

[0066] The preparation method of the above rheology modifier is as described in Example 1, except that in step (2), octadecyl acrylate is replaced with an equal amount of butyl acrylate; other steps and conditions are the same as in Example 1. Rheology modifier DA5 is obtained.

[0067] Comparative Example 6

[0068] A rheology modifier DA6 is described in Example 1, except that N,N-dimethylacrylamide is replaced with an equal amount of acrylamide. The composition of other raw materials is the same as in Example 1.

[0069] The preparation method of the above rheology modifier is as described in Example 1, except that in step (1), N,N-dimethylacrylamide is replaced with an equal amount of acrylamide; other steps and conditions are the same as in Example 1. Rheology modifier DA6 is obtained.

[0070] Comparative Example 7

[0071] A rheology modifier DA7 is as described in Example 1, except that 2-acrylamido-2-methylpropanesulfonic acid is not added; the composition of other raw materials is the same as in Example 1.

[0072] The preparation method of the above rheology modifier is as described in Example 1, except that: in step (1), 2-acrylamido-2-methylpropanesulfonic acid is not added, and the pH adjustment step is omitted accordingly; the pre-dissolution solution 1 is an aqueous solution of N,N-dimethylacrylamide. Other steps and conditions are the same as in Example 1. Rheology modifier DA7 is obtained.

[0073] Test case

[0074] The rheology modifiers prepared in the examples and comparative examples were added to 4 wt% bentonite-based water-based drilling fluid slurry to obtain test slurry, and performance tests were conducted.

[0075] The preparation process of the base slurry is as follows: add deionized water into a high-speed mixing cup, add 4% bentonite and 0.3% sodium carbonate by mass of water under low-speed stirring, and stir at low speed for 24 hours;

[0076] The test slurry preparation process is as follows: add a rheology modifier with a mass of 2% of the water in the base slurry to the base slurry at 11000 rpm, stir for 20 min, add NaCl (concentration of 36 wt% in the test slurry), and stir for another 20 min to obtain the test slurry.

[0077] The drilling fluid test slurries prepared using rheology modifiers A1-A3 were named F1-F3, and the drilling fluid test slurries prepared using rheology modifiers DA1-DA7 were named DF1-DF7.

[0078] 1. Drilling fluid performance testing

[0079] Take 400 mL of the above-mentioned drilling fluid base slurry, drilling fluid test slurries F1-F3 and DF1-DF7 respectively, stir at 5000 rpm for 20 min, then put them into an aging tank, place them in a roller furnace, and roll them at 220℃ for 16 hours. After cooling to room temperature, stir at 5000 rpm for another 20 min. Then, according to GB / T16783.1-2014, determine the apparent viscosity (AV, mPa.s), dynamic shear force (YP, Pa), and the reading Φ3 of the six-speed viscometer at 3 revolutions. The test temperature is room temperature, and the apparent viscosity is 1022 s. -1 The reading Φ3, obtained at a high shear rate, was 5.11 s at 3 revolutions. -1 The values ​​were measured at low shear rates, and the increases in AV, YP, and Φ3 of the test slurry compared to the drilling fluid-based slurry were calculated. The results are shown in Table 1.

[0080] Table 1 Drilling Fluid Performance Tests

[0081]

[0082] The apparent viscosity AV in the above data is 1022 s. -1 The values ​​were measured at high shear rates. It can be seen that compared to the base slurry, the increase in AV of the drilling fluid with the rheology modifier of this invention is not significant. This indicates that the network structure in the drilling fluid has undergone temporary disruption, resulting in lower viscosity, which is beneficial to the flow of the drilling fluid. The 3-turn reading Φ3 was obtained at 5.11 s. -1 The results, measured at low shear rates, show a significant increase in Φ3 in the drilling fluid with the rheology modifier of this invention. This indicates that the network structure in the drilling fluid recovers rapidly at low shear rates, leading to increased shear force and improved cuttings carrying capacity. This is also reflected in the change in dynamic shear force YP; the drilling fluid with the rheology modifier of this invention shows a greater increase in dynamic shear force, indicating a stronger network structure in the drilling fluid. These experimental results demonstrate that the rheology modifier of this invention can effectively improve the rheological properties of drilling fluids at 220℃ under saturated salt conditions.

[0083] Because rheology modifier DA1 does not introduce hydrophobic associative structures, the shear strength and thixotropy of DF1 are weaker than those of drilling fluids containing the rheology modifiers of this invention. Since rheology modifiers DA2 and DA3 cannot form dynamic covalent borate ester bonds, DF2 and DF3 have relatively higher viscosity under high shear and relatively weaker network structures (polymers and clays can form network structures). Inappropriate temperature settings during the synthesis of rheology modifier DA4 caused some of the catechol groups to lose their coordination ability with boric acid, resulting in a decrease in the performance of the shearing agent. Furthermore, DA5, DA6, and DA7 prepared by modifying the original formulation also exhibited poor performance. In summary, only rheology modifiers obtained according to the raw materials and methods disclosed in this invention can achieve the expected superior performance.

[0084] 2. Drilling fluid cuttings carrying capacity test

[0085] Take 400 mL of the above drilling fluid base slurry, F1-F3, and DF1-DF7 respectively, add 5 wt% sandstone cuttings of different sizes, stir at 5000 rpm for 20 min, then put into an aging tank, place it in a roller furnace, and roll it at 220℃ for 16 hours. After cooling to room temperature, open the tank and pour it into a transparent beaker. After standing for 20 min, observe whether the cuttings suspended in the drilling fluid have settled. The test results are shown in Table 2 and 3. Figure 2 As shown. Among them, Figure 2 Photographs of drilling fluids F3 (a) and DF4 (b) after adding 4-10 mesh sandstone cuttings and allowing them to stand for 20 minutes after aging.

[0086] Table 2 Settlement of rock cuttings of different sizes

[0087]

[0088] The data shows that after aging at 220℃, the drilling fluid with the rheology modifier of this invention has a significantly better ability to suspend rock cuttings and no obvious sedimentation occurs, thus fundamentally preventing accidents such as sand settling and stuck drill bits, and ensuring downhole safety.

[0089] In summary, the high-temperature resistant, water-based drilling fluid rheology modifier of this invention, through dynamic covalent chemical bonds and hydrophobic association, enables the drilling fluid to flow normally under high shear without clogging the drill bit's water channels, and efficiently lift suspended cuttings under low shear. This effectively resolves the contradiction between drilling fluid flowability and cuttings carrying capacity in practical engineering, improving the actual application effect of the drilling fluid. Furthermore, controlling the composition and proportion of raw materials within the range of this invention is necessary to obtain a rheology modifier with excellent performance.

[0090] 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 thixotropic rheology modifier for hot-temperature water-based drilling fluids, characterized in that, It is prepared from the following raw materials in parts by weight: 10-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8-10 parts of N,N-dimethylacrylamide, 0.5-1.5 parts of octadecyl acrylate, 1-1.5 parts of 3-acrylamidophenylboronic acid, 1-2 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent, 3-5 parts of initiator, 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol; The method for preparing the thixotropic rheology modifier for the temperature-resistant water-based drilling fluid is characterized by comprising the following steps: (1) Dissolve 2-acrylamido-2-methylpropanesulfonic acid completely in deionized water, adjust the pH to 7.0-8.0 with sodium hydroxide aqueous solution with a mass concentration of 40-60%, add N,N-dimethylacrylamide, dissolve completely to obtain pre-dissolved solution 1; (2) Dissolve octadecyl acrylate completely in ethanol to obtain pre-dissolved solution 2; (3) Dissolve 3-acrylamidophenylboronic acid completely in methanol to obtain pre-dissolved solution 3; (4) Under nitrogen or argon protection, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide is fully dissolved in deionized water, and pre-dissolving solution 1, pre-dissolving solution 2 and pre-dissolving solution 3 are added, followed by the addition of salting-out agent; the temperature is raised to 30-40℃, and the initiator is added. Under nitrogen or argon protection, the reaction is initiated at 30-40℃ and stirred until the system becomes viscous. The temperature is then raised to 40-45℃ and stirred for 6-8 hours; then, the mixture is precipitated, filtered, washed, dried and pulverized to obtain a thixotropic rheology modifier for water-based drilling fluid with temperature resistance.

2. The thixotropic rheology modifier for water-based drilling fluid according to claim 1, characterized in that, It is prepared from the following raw materials in parts by weight: 12-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 9-10 parts of N,N-dimethylacrylamide, 1-1.5 parts of octadecyl acrylate, 1.2-1.5 parts of 3-acrylamidophenylboronic acid, 1.5-2 parts of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-methylacrylamide, 20 parts of salting-out agent, 4-5 parts of initiator, 120 parts of deionized water, 10 parts of ethanol, and 10 parts of methanol.

3. The thixotropic rheology modifier for water-based drilling fluid according to claim 1, characterized in that, The salting-out agent is NaCl.

4. The thixotropic rheology modifier for water-based drilling fluid according to claim 1, characterized in that, The initiator is an aqueous solution of ammonium persulfate with a mass concentration of 5-15 wt% and an aqueous solution of sodium bisulfite with a mass concentration of 5-15 wt%; the mass ratio of the aqueous solution of ammonium persulfate to the aqueous solution of sodium bisulfite is 2-3:1-2.

5. The thixotropic rheology modifier for water-based drilling fluid according to claim 1, characterized in that, The mass ratio of deionized water in step (1) to deionized water in step (4) is 4-6:

1.

6. The thixotropic rheology modifier for water-based drilling fluid according to claim 1, characterized in that, In step (4), the precipitation method is as follows: add the reaction solution to ethanol, stir for 5-15 minutes and let stand for 10-30 minutes to allow the polymer to precipitate completely.

7. The application of the thixotropic rheology modifier for water-based drilling fluids as described in any one of claims 1-6 in water-based drilling fluids, characterized in that, The mass of the rheology modifier is 1-5 wt% of the drilling fluid mass.

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