High-temperature-resistant suspending agent for water-based drilling fluid as well as preparation method and application of high-temperature-resistant suspending agent

Abstract

The invention relates to the technical field of drilling fluid treatment admixtures, and discloses a high-temperature-resistant suspending agent for a water-based drilling fluid as well as a preparation method and application of the high-temperature-resistant suspending agent. The high-temperature-resistant suspending agent for the water-based drilling fluid is a polymer and comprises a repetitive unit A derived from unsaturated sulfonate and a repetitive unit B derived from unsaturated lactam, the unsaturated sulfonate comprises unsaturated sulfonate a and unsaturated sulfonate b; the unsaturated sulfonate a is unsaturated sulfonate without benzene; and the unsaturated sulfonate b is benzene-containing unsaturated sulfonate. According to the invention, a high-temperature-resistant suspending agent polymer formed by thermally initiating polymerization of unsaturated sulfonate and unsaturated lactam is adopted, the dispersity and good thixotropy of sulfonate are utilized to improve the suspension ability of the drilling fluid to a weighting material, and the temperature resistance of the polymer is improved by unsaturated lactam, so that the problem that the drilling fluid is not prone to cracking under a high-temperature condition is effectively solved. And the weighting material may severely settle.

Description

Technical Field

[0001] This invention relates to the technical field of drilling fluid treatment additives, and particularly to a high-temperature resistant suspending agent for water-based drilling fluids, its preparation method, and its application. Background Technology

[0002] With the deepening of exploration and development, the demand for ultra-high temperature drilling fluids in deep and ultra-deep well drilling is becoming increasingly strong. During ultra-deep well drilling, weighting materials such as barite are typically added to balance formation pressure. When encountering high-temperature formations, various components in the drilling fluid undergo physical changes and chemical reactions at ultra-high temperatures, leading to drastic changes in the drilling fluid's rheological properties and sedimentation stability. In particular, the high-temperature degradation of polymer treatment agents in the drilling fluid causes a decrease in viscosity, resulting in poor suspension and carrying capacity. Prolonged stasis can lead to severe sedimentation and deterioration of the system's performance, causing obstruction when running the tubing or difficulty in starting the pump, increasing the risks of drilling and completion operations. Therefore, ensuring that weighting materials are well dispersed and suspended in the drilling fluid under high-temperature conditions and maintaining the suspension stability of the drilling fluid is one of the key technologies facing ultra-deep well ultra-high temperature drilling fluids. Summary of the Invention

[0003] This invention addresses the technical problem of severe sedimentation of weighting materials in drilling fluids under high-temperature conditions, providing a high-temperature resistant suspending agent for water-based drilling fluids, its preparation method, and its application. The invention utilizes a high-temperature resistant suspending agent polymer formed by the thermally initiated polymerization of unsaturated sulfonates and unsaturated lactams. The dispersibility and good thixotropic properties of sulfonates enhance the suspending capacity of the drilling fluid for weighting materials, while the unsaturated lactams improve the polymer's temperature resistance, effectively solving the problem of severe sedimentation of weighting materials in drilling fluids under high-temperature conditions.

[0004] One objective of this invention is to provide a high-temperature resistant suspending agent for water-based drilling fluids, wherein the suspending agent is a polymer comprising repeating unit A derived from unsaturated sulfonate and repeating unit B derived from unsaturated lactam.

[0005] The unsaturated sulfonates include unsaturated sulfonate a and unsaturated sulfonate b; unsaturated sulfonate a is a benzene-free unsaturated sulfonate; and unsaturated sulfonate b is a benzene-containing unsaturated sulfonate.

[0006] The unsaturated sulfonate and unsaturated lactam of the present invention are thermally initiated to form a polymer, wherein the unsaturated sulfonate forms repeating unit A and the unsaturated lactam forms repeating unit B.

[0007] The suspending agent provided by this invention can effectively enhance the spatial network structure of drilling fluid, improve the drilling fluid's ability to support barite, and improve the dynamic stability of the weighted drilling fluid; it can also improve the dispersibility and suspension stability of weighting materials such as barite in drilling fluid under high temperature conditions.

[0008] This invention utilizes unsaturated lactams. Unsaturated lactams possess significant steric hindrance, which can further reduce the molecular weight of the polymer, thereby improving its temperature resistance. Furthermore, the cyclic structure of lactams can reduce the damage to the polymer caused by shear forces in high-temperature water environments, enhancing the polymer's structural stability. The benzene ring in the unsaturated benzenesulfonate can improve the rigidity of the polymer molecule and its temperature resistance.

[0009] Drilling fluid systems are not composed of a single treatment agent; each agent has a different function. Suspension agents are used for shear enhancement, specifically increasing the dynamic shear force (YP), initial shear force (G"), and final shear force (G') of the drilling fluid. Suspension agents differ in function from filtration reducers and viscosifiers. Filtration reducers enhance the fluid's resistance to water loss, specifically API and HTHP losses. Viscosifiers increase the apparent viscosity (AV) and plastic viscosity (PV) of the drilling fluid. The testing methods for these different treatment agents differ significantly.

[0010] According to a preferred embodiment of the present invention, the unsaturated sulfonate b is selected from at least one of p-styrene sulfonate, vinyl phenyl sulfonate, and allylbenzene sulfonate;

[0011] And / or, the unsaturated sulfonate a is selected from at least one of 2-acrylamido-2-methylpropanesulfonate, vinyl sulfonate, allyl sulfonate, 2-acryloyloxy-2-methylpropanesulfonate and 2,3-epoxypropanesulfonate.

[0012] The sulfonic acid group in this invention is a high-temperature hydration resistant group, which can improve the thermal stability of the copolymer.

[0013] According to a preferred embodiment of the present invention, the unsaturated sulfonate a is selected from at least two of sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinylsulfonate, sodium 2-allylsulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate.

[0014] Preferably, the unsaturated sulfonate a includes unsaturated sulfonate a1 and unsaturated sulfonate a2, wherein unsaturated sulfonate a1 is sodium 2-acrylamido-2-methylpropanesulfonate; and unsaturated sulfonate a2 includes at least one of sodium vinylsulfonate, sodium 2-allylsulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate.

[0015] According to a preferred embodiment of the present invention, the unsaturated lactam is selected from at least one of N-vinylpyrrolidone and N-vinylcaprolactam.

[0016] In this invention, the carbonyl group in the unsaturated lactam forms hydrogen bonds with the hydroxyl and carboxyl groups on the drilling fluid suspending agent molecular chain, which increases the difficulty of desorbing physically adsorbed water; the rigid groups increase the molecular chain's resistance to high temperature and shear damage, thereby improving the drilling fluid's temperature resistance.

[0017] According to a preferred embodiment of the present invention, the suspending agent comprises repeating units derived from sodium 2-acrylamido-2-methylpropanesulfonate, repeating units derived from unsaturated sulfonate a2, repeating units derived from unsaturated sulfonate b, and repeating units derived from unsaturated lactam; preferably, the mass ratio of the repeating units derived from sodium 2-acrylamido-2-methylpropanesulfonate, the repeating units derived from unsaturated sulfonate a2, the repeating units derived from unsaturated sulfonate b, and the repeating units derived from unsaturated lactam is (3-4):(7-8):(4-6):(3-5).

[0018] The high-temperature suspending agent of the present invention is a multi-component copolymer formed by copolymerization in aqueous solution. Its molecular chain contains functional groups such as amide bonds (which hydrolyze into carboxyl groups at high temperature), sulfonic acid groups, cationic ammonium groups, and rigid groups. These functional groups all have strong hydrophilicity and high salt resistance.

[0019] The inventors of this invention previously attempted to replace p-styrene sulfonate with alkenyl carboxylic acids or quaternary ammonium salts, or to replace N-vinylcaprolactam with acrylamide. However, acrylamide exhibited poor temperature resistance, generally not exceeding 180°C; alkenyl carboxylic acids or quaternary ammonium salts showed resistance not exceeding 200°C. Therefore, it is impossible to prepare a suspending agent resistant to 240°C using alkenyl carboxylic acids, quaternary ammonium salts, or N-vinylcaprolactam.

[0020] The second objective of this invention is to provide a method for preparing a high-temperature resistant suspending agent for water-based drilling fluid, comprising: obtaining a mixture comprising unsaturated sulfonate, unsaturated lactam and water, heating to carry out a polymerization reaction, and obtaining the high-temperature resistant suspending agent for water-based drilling fluid;

[0021] The unsaturated sulfonates include unsaturated sulfonate a and unsaturated sulfonate b; unsaturated sulfonate a is a benzene-free unsaturated sulfonate; and unsaturated sulfonate b is a benzene-containing unsaturated sulfonate.

[0022] According to a preferred embodiment of the present invention, the mass ratio of the unsaturated sulfonate, the unsaturated lactam, and water is (14-18):(3-5):(40-100);

[0023] And / or, the pH of the mixture is 5-7; preferably, the pH adjuster includes at least one selected from sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide, and sodium ethoxide;

[0024] And / or, the polymerization reaction temperature is 180-230℃, preferably 200-210℃; the reaction time is 16-100h, preferably 36-50h.

[0025] For example, the mass ratio of sodium 2-acrylamido-2-methylpropanesulfonate, unsaturated sulfonate a2, unsaturated sulfonate b, unsaturated lactam, and water is (3-4):(7-8):(4-6):(3-5):(40-100). In one embodiment, the mass ratio of sodium 2-acrylamido-2-methylpropanesulfonate, unsaturated sulfonate a2, unsaturated sulfonate b, unsaturated lactam, and water is 3:7:4:3:40, or 4:8:6:5:100, or 3:7:5:4:50, or 3:7:5:4:60, or 3:7:5:4:70, or 3:7:5:4:80, or 3:7:5:4:90.

[0026] Through research on the effect of temperature on the stability of organic compounds, the inventors discovered that: ① Aqueous solution-initiated polymerization: Aqueous solution-initiated polymerization occurs at relatively low temperatures, thus further reactions / side reactions of polymers at high temperatures are not possible. Therefore, various issues may arise when aqueous solution-initiated polymerization products are applied to high-temperature systems; ② Burst polymerization: Polymers synthesized through burst polymerization exhibit unstable properties, and the molecular weight range of additives is too large. This is due to the uneven temperature and uniformity of raw materials during burst polymerization. Therefore, if the additives are not thoroughly mixed, their performance will be unstable. To better balance the advantages of both polymerization methods and eliminate their shortcomings, a new polymer synthesis method, thermally initiated polymerization, was designed. This method utilizes high-temperature activation of monomers, making the monomers both raw materials and initiators. Thorough and uniform mixing in an aqueous solution ensures that the molecular weight range of the polymer does not increase while allowing the monomers to react fully at high temperatures, effectively avoiding the side effects caused by aqueous solution-initiated polymerization and burst polymerization. This invention employs thermal polymerization, where unsaturated double bonds are heated before polymerization, reducing the use of initiators and transfer agents and increasing the effective solid content of the product.

[0027] The olefin monomers (unsaturated sulfonates and unsaturated lactams) of the present invention are thermally initiated to form white or light yellow elastic solid products. The obtained elastic solid products are crushed and sieved to obtain white or light yellow powder products, which are the 240°C water-based drilling fluid suspensions.

[0028] The preparation method of this invention employs thermally initiated polymerization, eliminating the use of initiators and chain transfer agents, thus reducing the use of initiators and chain transfer agents and increasing the effective solid content of the product. Thermally initiated polymerization is more environmentally friendly and has a simpler production process compared to initiator-based polymerization. The high-temperature thermal polymerization synthesis method eliminates the impact of some side reactions of monomer small molecules on the final product's performance.

[0029] Before pH adjustment, the mixed aqueous solution of unsaturated sulfonate and unsaturated lactam is a strongly acidic environment with a pH less than 1.

[0030] According to a preferred embodiment of the present invention, the unsaturated sulfonate b is selected from at least one of p-styrene sulfonate, vinyl phenyl sulfonate, and allylbenzene sulfonate;

[0031] And / or, the unsaturated sulfonate a is selected from at least one of 2-acrylamido-2-methylpropanesulfonate, vinyl sulfonate, allyl sulfonate, 2-acryloyloxy-2-methylpropanesulfonate, and 2,3-epoxypropanesulfonate, preferably from at least two of sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinyl sulfonate, sodium 2-allyl sulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate; preferably, the unsaturated sulfonate a comprises unsaturated sulfonate a1 and unsaturated sulfonate a2, wherein unsaturated sulfonate a1 is sodium 2-acrylamido-2-methylpropanesulfonate; and unsaturated sulfonate a2 comprises at least one of sodium vinyl sulfonate, sodium 2-allyl sulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate;

[0032] And / or, the unsaturated lactam is selected from at least one of N-vinylpyrrolidone and N-vinylcaprolactam.

[0033] The third objective of this invention is to provide a high-temperature resistant suspending agent for water-based drilling fluid prepared by the above-mentioned method.

[0034] The fourth objective of this invention is to provide the application of high-temperature resistant suspending agents in water-based drilling fluids resistant to 240°C.

[0035] The beneficial effects of this invention are as follows:

[0036] The suspending agent provided by this invention can effectively enhance the spatial network structure of drilling fluid, improve the drilling fluid's ability to support barite, and improve the dynamic stability of the weighted drilling fluid; it can also improve the dispersibility and suspension stability of weighting materials such as barite in drilling fluid under high temperature conditions.

[0037] This invention utilizes a high-temperature suspending polymer formed by the thermally initiated polymerization of unsaturated sulfonates and unsaturated lactams. By leveraging the dispersibility and good thixotropy of sulfonates, the suspending capacity of drilling fluids for weighting materials is improved, while the unsaturated lactams enhance the polymer's temperature resistance. Furthermore, the cyclic structure can reduce the damage to the polymer caused by shear forces in high-temperature water environments, thereby enhancing the stability of drilling fluids under high-temperature conditions. This effectively solves the problem of severe sedimentation of weighting materials in drilling fluids under high-temperature conditions. Attached Figure Description

[0038] Figure 1 The image shows the SEM image of the white elastic solid product obtained in step (3) of Example 2. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0040] In the following embodiments, the high-temperature resistant suspending agent for water-based drilling fluid comprises a polymer formed by thermally initiated polymerization of olefin monomers; the olefin monomers are of four types, namely ① two of the unsaturated sulfonates a (excluding benzene unsaturated sulfonates), ② unsaturated sulfonate b (containing benzene unsaturated sulfonates) and ③ unsaturated lactams.

[0041] Unsaturated sulfonate a (excluding benzene-free unsaturated sulfonate) contains unsaturated sulfonate a1 and unsaturated sulfonate a2; unsaturated sulfonate a1 is sodium 2-acrylamido-2-methylpropanesulfonate; unsaturated sulfonate a2 is at least one of sodium vinyl sulfonate, sodium 2-allyl sulfonate, 2-acryloyloxy-2-methylpropanesulfonic acid, and sodium 2,3-epoxypropanesulfonate.

[0042] Preparation method of high-temperature resistant suspending agent for water-based drilling fluid: After dissolving the above-mentioned olefin monomers in water, add a pH adjuster to adjust the pH of the solution to 5-7; heat to 180-230℃ and react at a constant temperature for 16-100h; the olefin monomers are polymerized by thermal initiation to form a high-temperature resistant suspending agent.

[0043] The mass ratio of sodium 2-acrylamido-2-methylpropanesulfonate, unsaturated sulfonate a2, unsaturated sulfonate b, unsaturated lactam to water is (3-4):(7-8):(4-6):(3-5):(40-100).

[0044]

Example 1

[0045] (1) Add 300g of deionized water to a 1-liter polytetrafluoroethylene cup, and add 15g of 2-acrylamido-2-methylpropanesulfonate, 35g of sodium 2-allylsulfonate, 20g of p-styrenesulfonate and 15g of N-vinylpyrrolidone to the beaker and stir to dissolve.

[0046] (2) Add a 20wt% sodium carbonate aqueous solution to adjust the pH of the solution to 6;

[0047] (3) Heat the polytetrafluoroethylene beaker containing the above solution to 200°C in a roller furnace to initiate polymerization. Maintain the temperature for 60 hours to obtain a white elastic solid product.

[0048] (4) The white elastic solid product is crushed with a universal pulverizer and passed through a 100-mesh sieve to obtain a white powder solid product, which is the 240℃ water-based drilling fluid suspension.

[0049]

Example 2

[0050] (1) Add 500g of deionized water to a 1-liter polytetrafluoroethylene cup, and add 20g of 2-acrylamido-2-methylpropanesulfonate, 40g of sodium 2-allylsulfonate, 20g of p-styrenesulfonate and 25g of N-vinylpyrrolidone to the beaker and stir to dissolve.

[0051] (2) Add a 20wt% sodium carbonate aqueous solution to adjust the pH of the solution to 6;

[0052] (3) Heat the polytetrafluoroethylene beaker containing the above solution to 200°C in a roller furnace, initiate polymerization by heat, and keep the temperature constant for 65 hours to obtain a white elastic solid product.

[0053] (4) The product is crushed with a universal pulverizer and passed through a 100-mesh sieve to obtain a white powder solid product, which is the 240℃ water-based drilling fluid suspension.

[0054]

Example 3

[0055] (1) Add 500g of deionized water to a 1-liter polytetrafluoroethylene cup, and add 15g of 2-acrylamido-2-methylpropanesulfonate, 35g of sodium 2-allylsulfonate, 30g of p-styrenesulfonate and 20g of N-vinylpyrrolidone to the beaker and stir to dissolve.

[0056] (2) Add a 20wt% sodium carbonate aqueous solution to adjust the pH of the solution to 6;

[0057] (3) Heat the polytetrafluoroethylene beaker containing the above solution to 200°C in a roller furnace, initiate polymerization by heat, and keep the temperature constant for 65 hours to obtain a white elastic solid product.

[0058] (4) The product is crushed with a universal pulverizer and passed through a 100-mesh sieve to obtain a white powder solid product, which is the 240℃ water-based drilling fluid suspension.

[0059]

Example 4

[0060] The only difference from Example 2 is that in step (1), "p-styrene sulfonate" is replaced with vinylphenyl sulfonic acid.

[0061]

Example 5

[0062] The only difference from Example 2 is that in step (1), "sodium 2-allyl sulfonate" is replaced with sodium vinyl sulfonate.

[0063]

Example 6

[0064] The only difference from Example 2 is that in step (1), “N-vinylpyrrolidone” is replaced with N-vinylcaprolactam.

[0065]

Example 7

[0066] The only difference from Example 2 is that in step (2), the pH value is adjusted from 6 to 7.

[0067]

Example 8

[0068] The only difference from Example 2 is that in step (2), the pH value is adjusted to 8 instead of 6.

[0069]

Example 9

[0070] The only difference from Example 2 is that in step (1), “20g p-styrene sulfonate” is replaced with “15g p-styrene sulfonate”.

[0071]

Example 10

[0072] The only difference from Example 2 is that in step (1), “20g p-styrene sulfonate” is replaced with “10g p-styrene sulfonate”.

[0073]

Comparative Example 1

[0074] The only difference from Example 2 is that the pH is not adjusted in step (2), and the pH of the solution is 0.7.

[0075] [Comparative Example 2]

[0076] The only difference from Example 2 is that the heating temperature in step (3) is 150°C and the temperature is kept constant for 70 hours.

[0077] [Comparative Example 3]

[0078] The only difference from Example 2 is that the amount of deionized water added in step (1) is 150 mL, and the unsaturated sulfonate cannot be completely dissolved.

[0079] [Comparative Example 4]

[0080] The only difference from Example 2 is that the polymerization method in step (3) is not "thermal polymerization", but redox initiation, with 0.5 wt% ammonium persulfate as the initiator; the reaction is carried out at room temperature, and the solid product is obtained by freeze drying after the polymerization reaction is completed.

[0081] [Comparative Example 5]

[0082] The only difference from Example 2 is that the stirring and dissolving step (1) is not performed, and the solid at the bottom of the cup is not completely dissolved before heating.

[0083] Comparative Example 6

[0084] The only difference from Example 2 is that step (1) does not contain "N-vinylpyrrolidone", that is, step (1) is replaced by "adding 500g of deionized water to a 1-liter polytetrafluoroethylene cup, and adding 20g of 2-acrylamido-2-methylpropanesulfonate, 40g of sodium 2-allylsulfonate, and 20g of p-styrenesulfonate to the beaker and stirring to dissolve".

[0085] Experimental Example 1

[0086] Prepare a base slurry of 500 mL fresh water + 20% NaCl + 3.0% PSP-1, using a density of 4.2 g / cm³. 3 The density of the base slurry was adjusted to 2.4 g / cm³ using barite. 3 After stirring and sealing for 24 hours, 1.0% of Examples 1-8 and Comparative Examples 1-5 were added respectively. After stirring for 20 minutes, the mixture was placed in a 500mL graduated cylinder to measure the sedimentation performance of the slurry.

[0087] The slurry was left to stand at 25±1℃. The density difference between the upper and lower liquid phases of the slurry was measured using a drilling fluid densitometer. When the density difference was ≥0.02g / cm³, the slurry was considered to have a density difference of ≥0.02g / cm³. 3 The time was recorded as the slurry settling instability time, and the test results are shown in Table 1.

[0088] Table 1. Effect of suspending agents on the stability of the base slurry.

[0089]

[0090]

[0091] As shown in Table 1, the product obtained by thermally initiated polymerization in Example 2 exhibits significantly better sedimentation stability than the product synthesized by the liquid-phase redox initiation method in Comparative Example 4. This is because the polymer product polymerized at high temperatures does not possess the linear structure generated by liquid-phase polymerization, and its supporting effect on the substrate is far lower than that of the product synthesized by thermally initiated polymerization. Figure 1As shown, the 240℃-resistant water-based drilling fluid suspending agent prepared in Example 2 exhibits a honeycomb structure when spread in aqueous solution. This structure can better enhance the static shear force of the drilling fluid, maintain the suspension stability of the drilling fluid through static shear force, and prevent solid particles in the slurry from settling.

[0092] Experiment Example 2

[0093] Prepare a base slurry of 500 mL fresh water + 20% NaCl + 3.0% PSP-1, using a density of 4.2 g / cm³. 3 The barite was used to increase the density of the base slurry to 2.4 g / cm³. 3 After stirring and sealing for 24 hours, 1.0% of Examples 1-8 and Comparative Examples 1-5 were added respectively. After stirring for 20 minutes, the slurry was placed in an aging tank and placed in a high-temperature roller heating furnace. The tank was heated at 240°C for 16 hours, cooled to room temperature, stirred at 10,000 rpm for 20 minutes, and then placed in a 500 mL graduated cylinder to test the slurry settling performance.

[0094] The slurry was left to stand at 25±1℃. The density difference between the upper and lower liquid phases of the slurry was measured using a drilling fluid densitometer. When the density difference was ≥0.02g / cm³, the slurry was considered to have a density difference of ≥0.02g / cm³. 3 The time was recorded as the sedimentation instability time of the slurry, and the test results are shown in Table 2.

[0095] Table 2. Effect of suspending agent on the stability of base slurry at 240℃

[0096]

[0097]

[0098] As shown in Table 2, in Comparative Example 4, which was obtained by adding redox initiation to the base slurry, barite rapidly sank after high-temperature treatment, causing slurry instability. This is mainly because the product obtained by room-temperature initiation polymerization has a simple linear structure, low temperature resistance, and low ability to further extend under high-temperature conditions, resulting in a sharp decrease in suspension capacity. The drilling fluid suspending agents developed in Examples 1-8 of this invention maintain the stability of the slurry well after high-temperature treatment. In Example 2, the stability time reached 8 days. Because the pH of Comparative Example 1 was not adjusted, the four polymer monomers contained in this invention had a high degree of polymerization in an acidic environment, resulting in a longer linear chain of the suspending agent. This resulted in a significant thickening effect but not a significant shearing effect. It was also more prone to chain breakage during high-temperature aging, thus resulting in poorer sedimentation stability after aging. In Comparative Example 2, the heating temperature in step (3) was 150°C. Even after 70 hours of constant temperature, the polymerization reaction could not be completed. The polymer further underwent a branching reaction during high-temperature aging, thus improving sedimentation stability. Therefore, the sedimentation stability of Comparative Example 2 was slightly better than that of Comparative Example 1. Due to incomplete monomer dissolution, the monomer participation and arrangement sequence were affected during the thermally initiated polymerization process in Comparative Examples 3 and 5, resulting in suspensions with weak temperature resistance, relatively simple branched structures, and poor sedimentation stability. The linear structure of Comparative Example 4 not only reduced the polymer's support for the slurry but also significantly decreased its temperature resistance.

[0099] Experimental Example 3

[0100] Add 4.0g of the 1.0wt% suspension prepared in Example 2 to the prepared 5% Bohai Drilling Soil Slurry. After stirring at high speed for 10 min, adjust the pH value to 10 with saturated NaOH solution, and continue stirring at high speed for another 10 min. The apparent viscosity, dynamic shear force, initial shear force and final shear force were measured at 240℃ for 3 days, 5 days, 7 days and 10 days respectively, according to GB / T 16783.1. The test results are shown in Table 3.

[0101] Table 3 Performance test results after 3, 5, 7 and 10 days of aging.

[0102]

[0103]

[0104] As shown in Table 3, the suspension prepared in Example 2 still had an initial shear force of 2 Pa and a final shear force of 14 Pa after being left to stand for aging at 240°C for 10 days. The shear force retention rate (final shear force at 10 days / final shear force of curing slurry) was ≥80%. It can be seen that the suspension prepared by the present invention has excellent temperature resistance and excellent shearing performance of soil slurry.

[0105] Experiment Example 4

[0106] Add 4.0g of 1.0wt% of the suspending agent prepared in Example 2 and Comparative Example 6 to the prepared 5% Bohai Drilling Slurry. After stirring at high speed for 10 min, adjust the pH value to 10 with saturated NaOH solution, and continue stirring at high speed for another 10 min. The apparent viscosity, dynamic shear force, initial shear force and final shear force were measured at 240℃ for 3 days according to GB / T16783.1. The test results are shown in Table 4.

[0107] Table 4

[0108]

[0109] As shown in Table 4, the absence of N-vinylpyrrolidone in the suspension concentrate will seriously affect its high-temperature resistance, especially the initial and final shear forces of the aging suspension concentrate.

[0110] Experimental Example 5

[0111] Add 4.0g of 1.0wt% of the suspending agent prepared in Examples 2, 9 and 10 to the prepared 5% Bohai Drilling Slurry. After stirring at high speed for 10min, adjust the pH value to 10 with saturated NaOH solution, and continue stirring at high speed for another 10min. The apparent viscosity, dynamic shear force, initial shear force and final shear force after standing and aging at 240℃ for 3 days are determined according to GB / T 16783.1. The test results are shown in Table 5.

[0112] Table 5

[0113]

[0114] As shown in Table 5, the content of sodium styrene sulfonate has a significant impact on the suspending agent. In Example 9, the proportion of sodium styrene sulfonate added is only 75% of that in Example 2. The suspending agent prepared in Example 2 has significantly better apparent viscosity, plastic viscosity, dynamic shear force, initial shear force, and final shear force than those in Examples 9 and 10.

[0115] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component is stated, or the mass ratio of unsaturated sulfonates, unsaturated benzenesulfonates, unsaturated lactams, and deionized water is (3-4):(7-8):(4-6):(3-5):(40-100), in this specification it means specifically listing values ​​such as (3-4):(7-8):(4-6):(3-5):(41-99), (3-4):(7-8):(4-6):(3-5):(42-98)... and (3-4):(7-8):(4-6):(3-5):(60-61). For non-integer values, it may be appropriate to consider a unit of 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically cited examples. In this application, in a similar manner, all possible combinations of values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0116] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A high-temperature resistant suspending agent for water-based drilling fluids, characterized in that, The suspending agent is a polymer comprising repeating unit A derived from unsaturated sulfonate and repeating unit B derived from unsaturated lactam. The unsaturated sulfonates include unsaturated sulfonate a and unsaturated sulfonate b; unsaturated sulfonate a is a benzene-free unsaturated sulfonate; and unsaturated sulfonate b is a benzene-containing unsaturated sulfonate.

2. The high-temperature resistant suspending agent for water-based drilling fluid according to claim 1, characterized in that, The unsaturated sulfonate b is selected from at least one of p-styrene sulfonate, vinyl phenyl sulfonate and allyl benzene sulfonate; And / or, the unsaturated sulfonate a is selected from at least one of 2-acrylamido-2-methylpropanesulfonate, vinyl sulfonate, allyl sulfonate, 2-acryloyloxy-2-methylpropanesulfonate and 2,3-epoxypropanesulfonate.

3. The high-temperature resistant suspending agent for water-based drilling fluid according to claim 2, characterized in that, The unsaturated sulfonate a is selected from at least two of sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinylsulfonate, sodium 2-allylsulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate. Preferably, the unsaturated sulfonate a includes unsaturated sulfonate a1 and unsaturated sulfonate a2, wherein unsaturated sulfonate a1 is sodium 2-acrylamido-2-methylpropanesulfonate; and unsaturated sulfonate a2 includes at least one of sodium vinylsulfonate, sodium 2-allylsulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate.

4. The high-temperature resistant suspending agent for water-based drilling fluid according to any one of claims 1-3, characterized in that, The unsaturated lactam is selected from at least one of N-vinylpyrrolidone and N-vinylcaprolactam.

5. The high-temperature resistant suspending agent for water-based drilling fluid according to claim 4, characterized in that, The suspending agent comprises repeating units derived from sodium 2-acrylamido-2-methylpropanesulfonate, repeating units derived from unsaturated sulfonate a2, repeating units derived from unsaturated sulfonate b, and repeating units derived from unsaturated lactam; preferably, the mass ratio of the repeating units derived from sodium 2-acrylamido-2-methylpropanesulfonate, the repeating units derived from unsaturated sulfonate a2, the repeating units derived from unsaturated sulfonate b, and the repeating units derived from unsaturated lactam is (3-4):(7-8):(4-6):(3-5).

6. A method for preparing a high-temperature resistant suspending agent for water-based drilling fluid, characterized in that, include: A mixture comprising unsaturated sulfonate, unsaturated lactam and water is obtained, and then heated to carry out a polymerization reaction to obtain the water-based drilling fluid anti-high temperature suspension agent; The unsaturated sulfonates include unsaturated sulfonate a and unsaturated sulfonate b; unsaturated sulfonate a is a benzene-free unsaturated sulfonate; and unsaturated sulfonate b is a benzene-containing unsaturated sulfonate.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the unsaturated sulfonate, unsaturated lactam and water is (14-18):(3-5):(40-100); And / or, the pH of the mixture is 5-7; preferably, the pH adjuster includes at least one selected from sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide, and sodium ethoxide; And / or, the polymerization reaction temperature is 180-230℃, preferably 200-210℃; the reaction time is 16-100h, preferably 36-50h.

8. The preparation method according to claim 6 or 7, characterized in that, The unsaturated sulfonate b is selected from at least one of p-styrene sulfonate, vinyl phenyl sulfonate and allyl benzene sulfonate; And / or, the unsaturated sulfonate a is selected from at least one of 2-acrylamido-2-methylpropanesulfonate, vinyl sulfonate, allyl sulfonate, 2-acryloyloxy-2-methylpropanesulfonate, and 2,3-epoxypropanesulfonate, preferably from at least two of sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinyl sulfonate, sodium 2-allyl sulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate; preferably, the unsaturated sulfonate a comprises unsaturated sulfonate a1 and unsaturated sulfonate a2, wherein unsaturated sulfonate a1 is sodium 2-acrylamido-2-methylpropanesulfonate; and unsaturated sulfonate a2 comprises at least one of sodium vinyl sulfonate, sodium 2-allyl sulfonate, sodium 2-acryloyloxy-2-methylpropanesulfonate, and sodium 2,3-epoxypropanesulfonate; And / or, the unsaturated lactam is selected from at least one of N-vinylpyrrolidone and N-vinylcaprolactam.

9. A high-temperature resistant suspending agent for water-based drilling fluid, prepared by any one of claims 6-8.

10. The application of the high-temperature resistant suspending agent for water-based drilling fluid as described in any one of claims 1-5 or the high-temperature resistant suspending agent for water-based drilling fluid as described in claim 9 in water-based drilling fluid, especially water-based drilling fluid resistant to 240°C.

Images