Drilling fluid suspending agent, preparation method and application

Abstract

The invention provides a drilling fluid suspending agent as well as a preparation method and application thereof. The invention provides a drilling fluid suspending agent, the suspending agent is prepared from unsaturated sulfonate through thermal initiation polymerization, and the unsaturated sulfonate comprises 2-acrylamido-2-methylpropanesulfonate, alkyl alkenyl sulfonate and unsaturated benzene sulfonate. In the second aspect, the invention provides a preparation method of the suspending agent provided in the first aspect, and the preparation method comprises the following steps: unsaturated sulfonate is subjected to a thermal polymerization reaction to prepare the suspending agent. According to the drilling fluid suspending agent provided by the invention, when the provided drilling fluid suspending agent is applied to a drilling fluid, the sedimentation instability time of the drilling fluid is 10-12d, and the high temperature resistance of the drilling fluid suspending agent can reach 230 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of drilling fluid, in particular to a drilling fluid suspending agent, a preparation method and application thereof. BACKGROUND

[0002] With the deepening of exploration and development, the demand for ultra-high temperature drilling fluid is more intense in deep well and ultra-deep well drilling. In the process of ultra-deep well drilling, weighting materials such as barite are usually added to balance the formation pressure, when drilling through high temperature formation, various components in the drilling fluid will undergo physical changes and chemical reactions at ultra-high temperature, resulting in dramatic changes in the rheological properties, sedimentation stability and other properties of the drilling fluid, especially the high temperature degradation of polymer treatment agent in the drilling fluid, which causes the viscosity of the drilling fluid to decrease, resulting in poor suspension and carrying performance of the drilling fluid, and the drilling fluid may be seriously settled and the system performance may be deteriorated after long-term static, which causes the pipe string to be blocked or the pump to be difficult to start, increasing the risk of drilling and completion operation. Therefore, how to ensure that the weighting material is well dispersed and suspended in the drilling fluid under high temperature environment and maintain the suspension stability of the drilling fluid is one of the key technologies for ultra-high temperature drilling fluid in ultra-deep well.

[0003] In the prior art, there are generally two methods to improve the dispersibility and suspension stability of weighting materials such as barite in the drilling fluid under high temperature conditions: (1) using structure stabilizers, suspending agents or dispersants to enhance the spatial network structure of the drilling fluid, improve the supporting capacity of the drilling fluid to barite, and improve the dynamic stability of the weighted drilling fluid; (2) modifying the barite, using a certain surfactant to make the surface of the barite hydrophilic or oleophilic, hindering the barite from coalescing into a cluster, and improving the dispersibility and suspension stability of the barite in the drilling fluid.

[0004] Through the study of the influence of temperature on the stability of organic matter, it is found that the current synthesis method of drilling fluid treatment agent has the following problems: (1) aqueous solution initiation polymerization method: the aqueous solution initiation polymerization reaction temperature is relatively low, therefore, the further reaction / side reaction of the high molecular material under high temperature environment cannot be realized, causing the performance of the additive to be unstable; (2) explosive polymerization synthesis method: the performance of the high molecular material synthesized by explosive polymerization is unstable, and the molecular weight range of the additive is too large, which is caused by the non-uniformity of the system temperature and the raw materials during the explosive polymerization process, therefore, if the mixing is not sufficient, the performance of the additive will be unstable.

[0005] Therefore, there is an urgent need in the prior art for a drilling fluid suspending agent with excellent performance. SUMMARY

[0006] In order to solve the above problems in the prior art, the present application provides a drilling fluid suspending agent, a preparation method and application thereof.

[0007] In a first aspect, the present application provides a drilling fluid suspending agent, the suspending agent being prepared by thermal initiation polymerization of an unsaturated sulfonate, the unsaturated sulfonate including 2-acrylamido-2-methylpropane sulfonate, an alkenyl sulfonate and an unsaturated benzene sulfonate.

[0008] In an embodiment of the present application, the thermal initiation polymerization is performed at a temperature of 180-205℃.

[0009] Preferably, the pH of the mixture is adjusted to 7-9 before the thermal initiation polymerization.

[0010] In an embodiment of the present application, the thermal initiation polymerization is performed for 50-70 hours.

[0011] In an embodiment of the present application, the mass ratio of the 2-acrylamido-2-methylpropane sulfonate, the alkenyl sulfonate, the unsaturated benzene sulfonate and the water is (3-4):(11-12):(2-6):(40-100).

[0012] In an embodiment of the present application, the alkenyl sulfonate is selected from at least one of vinyl sulfonate, allyl sulfonate, butenyl sulfonate and pentenyl sulfonate.

[0013] Preferably, the alkenyl sulfonate is allyl sulfonate.

[0014] In an embodiment of the present application, the unsaturated benzene sulfonate is selected from at least one of p-styryl sulfonate and (4-vinylphenyl)methyl sulfonate.

[0015] In an embodiment of the present application, the water is deionized water or distilled water.

[0016] In an embodiment of the present application, the pH of the mixture is adjusted by one or more of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide and sodium ethoxide.

[0017] Preferably, the pH of the mixture is adjusted by sodium carbonate aqueous solution.

[0018] In a second aspect, the present application provides a preparation method of the suspending agent of the first aspect, the preparation method including the following steps: thermal initiation polymerization of the unsaturated sulfonate to obtain the suspending agent; the unsaturated sulfonate including 2-acrylamido-2-methylpropane sulfonate, an alkenyl sulfonate and an unsaturated benzene sulfonate.

[0019] In an embodiment of the present application, the thermal initiation polymerization is performed at a temperature of 180-205℃.

[0020] As a specific embodiment of the present application, the conditions of the thermal initiation polymerization include: dissolving the unsaturated sulfonate in water to obtain a mixed solution, and the mixed solution is subjected to the thermal initiation polymerization to obtain the suspending agent.

[0021] Preferably, the pH of the mixed solution is adjusted to 7-9, and then the thermal initiation polymerization is performed to obtain the suspending agent.

[0022] As a specific embodiment of the present application, the temperature of the thermal initiation polymerization is 180-205℃.

[0023] As a specific embodiment of the present application, the time of the thermal initiation polymerization is 50-70h.

[0024] Preferably, the mass ratio of the 2-acrylamido-2-methylpropane sulfonate, the alkylalkenyl sulfonate, the unsaturated benzene sulfonate and the water is (3-4):(11-12):(2-6):(40-100).

[0025] As a specific embodiment of the present application, the alkylalkenyl sulfonate is selected from at least one of vinyl sulfonate, allyl sulfonate, alkenyl sulfonate, and alkyl sulfonate.

[0026] As a specific embodiment of the present application, the unsaturated benzene sulfonate is selected from at least one of p-styryl sulfonate and (4-vinylphenyl) methyl sulfonate.

[0027] As a specific embodiment of the present application, the water is deionized water or distilled water.

[0028] As a specific embodiment of the present application, one or more of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide, and sodium ethoxide is used to adjust the pH of the mixed solution.

[0029] As a specific embodiment of the present application, the conditions of the thermal initiation polymerization include: dissolving the unsaturated sulfonate in water to obtain a mixed solution, and the mixed solution is subjected to the thermal initiation polymerization to obtain the suspending agent.

[0030] Preferably, the stirring time is 15-30min.

[0031] As a specific embodiment of the present application, the mixed solution is subjected to the thermal initiation polymerization to obtain a solid product, and the solid product is subjected to pulverization and sieving to obtain the suspending agent.

[0032] In a third aspect, the present application provides a drilling fluid, which comprises the suspending agent provided in the first aspect of the present application or prepared by the preparation method provided in the second aspect of the present application.

[0033] Preferably, the content of the suspending agent in the drilling fluid is 1wt%-3wt%.

[0034] Further preferably, the settling instability time of the drilling fluid is 10-12d.

[0035] Compared with the prior art, the present invention achieves the following beneficial effects.

[0036] This invention provides a drilling fluid suspending agent. When applied to drilling fluid, the settling instability time of the drilling fluid is 10-12 days, and the high temperature resistance of the drilling fluid suspending agent can reach 230℃.

[0037] This invention optimizes the synthesis method of suspending agents by using the double bonds of unsaturated sulfonate monomer molecules for thermal polymerization, reducing the use of initiators and transfer agents, and increasing the effective solid content of the product.

[0038] The suspension synthesis process in this invention is more environmentally friendly and simpler to produce than initiator polymerization.

[0039] This invention prepares a suspending agent through a high-temperature thermal polymerization synthesis method, eliminating some side reactions of small monomer molecules. This reduces the impact of byproducts on the performance of the final product.

[0040] The suspending agent synthesized by the present invention through high-temperature thermal polymerization reaction is a solid powder as the final product, which is convenient for transportation and effectively reduces transportation costs.

[0041] The suspending agent of this invention is copolymerized in an aqueous solution. The resulting multi-component copolymer molecular chain contains amide bonds, which can hydrolyze into carboxyl groups at high temperatures. In addition, the polymer also includes rigid groups such as sulfonic acid groups, cationic ammonium groups, and benzene rings. The presence of these groups gives the suspending agent hydrophilicity and high salt resistance. Simultaneously, the suspending agent also contains carbonyl groups, which form hydrogen bonds with hydroxyl and carboxyl groups on the suspending agent molecular chain, increasing the difficulty of desorbing physically adsorbed water. The sulfonic acid groups and benzene ring groups increase the molecular chain's resistance to high temperatures and shear failure, thereby improving the drilling fluid's temperature resistance. Attached Figure Description

[0042] Figure 1 The image shows the morphology of the suspension prepared in Example 2 dispersed in an aqueous solution. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0044] The raw materials used in all embodiments of the present invention are commercially available, wherein,

[0045] Sodium 2-acrylamido-2-methylpropanesulfonate was purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0046] Sodium allyl sulfonate was purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0047] Sodium 2-acrylamido-2-methylpropanesulfonate was purchased from Shandong Yousuo Chemical Technology Co., Ltd.;

[0048] Sodium p-styrenesulfonate was purchased from Japan Toagosei Co., Ltd., CAS No: 2695-37-6;

[0049] Sodium (4-vinylphenyl)methanesulfonate was purchased from Hubei Chengfeng Chemical Co., Ltd., CAS No: 10195-45-6;

[0050] DSP-1 was purchased from Shandong Deshengyuan Petroleum Technology Co., Ltd.;

[0051] Barite was purchased from Lai De Heavy Calcium Talc Powder Factory in Linyi, Shandong.

[0052] Example 1

[0053] (1) 300 g of deionized water was added to a 1 liter volume of a polytetrafluoroethylene cup, 15 g of sodium 2-acrylamido-2-methylpropanesulfonate, 60 g of sodium allylsulfonate, and 20 g of sodium p-styrenesulfonate were added to the polytetrafluoroethylene cup and stirred for 20 min to obtain a mixed solution;

[0054] (2) A 20wt% sodium carbonate aqueous solution was added to the polytetrafluoroethylene cup to adjust the pH value of the mixed solution to 7;

[0055] (3) The polytetrafluoroethylene cup containing the above mixed solution was placed in a roller furnace, and the roller furnace was heated to 180℃, and the temperature was kept constant for 60 h to initiate polymerization, and a white elastic solid product was obtained;

[0056] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was a drilling fluid suspending agent.

[0057] Example 2

[0058] (1) 500 g of deionized water was added to a 1 liter volume of a polytetrafluoroethylene cup, 20 g of sodium 2-acrylamido-2-methylpropanesulfonate, 55 g of sodium allylsulfonate, and 10 g of sodium p-styrenesulfonate were added to the polytetrafluoroethylene cup and stirred for 20 min to obtain a mixed solution;

[0059] (2) A 20wt% sodium carbonate aqueous solution was added to the polytetrafluoroethylene cup to adjust the pH value of the mixed solution to 7;

[0060] (3) The polytetrafluoroethylene cup containing the above mixed solution was placed in a roller furnace, and the roller furnace was heated to 180℃, and the temperature was kept constant for 65 h to initiate polymerization, and a white elastic solid product was obtained;

[0061] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was a drilling fluid suspending agent.

[0062] Example 3

[0063] (1) 500 g of deionized water was added to a 1 liter volume of a Teflon cup, 15 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 55 g of allyl sulfonic acid sodium salt, and 30 g of p-styrylsulfonic acid sodium salt were added to the Teflon cup and stirred for 20 min to obtain a mixed solution;

[0064] (2) A 20 wt% sodium carbonate aqueous solution was added to the Teflon cup to adjust the pH of the mixed solution to 7;

[0065] (3) The Teflon cup containing the above mixed solution was placed in a roller oven, the roller oven was heated to 180°C, and the temperature was kept constant for 65 h to heat initiate polymerization, obtaining a white elastic solid product;

[0066] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was a drilling fluid suspending agent.

[0067] Example 4

[0068] The suspending agent was prepared by the same method as in Example 2, except that the unsaturated benzene sulfonate in step (1) was (4-vinylphenyl)methanesulfonic acid sodium salt.

[0069] Example 5

[0070] The suspending agent was prepared by the same method as in Example 2, except that the alkylalkenyl sulfonate in step (1) was vinyl sulfonic acid sodium salt.

[0071] Example 6

[0072] The suspending agent was prepared by the same method as in Example 2, except that the pH of the mixed solution was adjusted to 9 in step (2).

[0073] Comparative Example 1

[0074] (1) 500 g of deionized water was added to a 1 liter volume of a Teflon cup, 20 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 55 g of allyl sulfonic acid sodium salt, and 10 g of p-styrylsulfonic acid sodium salt were added to the Teflon cup and stirred for 20 min to obtain a mixed solution;

[0075] (2) The Teflon cup containing the above mixed solution was placed in a roller oven, and the roller oven was heated to 180°C, and the temperature was kept constant for 65 h to heat initiate polymerization, obtaining a solid product;

[0076] (3) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was a drilling fluid suspending agent.

[0077] Comparative Example 2

[0078] (1) Into a 1 liter volume of Teflon cup, 500g of deionized water was added, 20g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 55g of allyl sulfonic acid sodium salt, 10g of p-styrenyl sulfonic acid sodium salt were added into the Teflon cup and stirred for 20min to obtain a mixed solution;

[0079] (2) A 20wt% sodium carbonate aqueous solution was added to the Teflon cup to adjust the pH value of the mixed solution to 7;

[0080] (3) The Teflon cup containing the above mixed solution was placed in a roller oven, and the roller oven was heated to 150℃, and kept at 70h, and the polymerization was initiated by heat to obtain a solid product;

[0081] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was a drilling fluid suspending agent.

[0082] Comparative Example 3

[0083] (1) Into a 1 liter volume of Teflon cup, 150g of deionized water was added, 20g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 55g of allyl sulfonic acid sodium salt, 10g of p-styrenyl sulfonic acid sodium salt were added into the Teflon cup and stirred for 20min to obtain a dispersion;

[0084] (2) A 20wt% sodium carbonate aqueous solution was added to the Teflon cup to adjust the pH value of the dispersion to 7;

[0085] (3) The Teflon cup containing the above dispersion was placed in a roller oven, and the roller oven was heated to 180℃, and kept at 65h, and the polymerization was initiated by heat to obtain a solid product;

[0086] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was a drilling fluid suspending agent.

[0087] Comparative Example 4

[0088] (1) Into a 1 liter volume of Teflon cup, 500g of deionized water was added, 20g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 55g of allyl sulfonic acid sodium salt, 10g of p-styrenyl sulfonic acid sodium salt were added into the Teflon cup and stirred for 20min to obtain a mixed solution;

[0089] (2) A 20wt% sodium carbonate aqueous solution was added to the Teflon cup to adjust the pH value of the mixed solution to 7;

[0090] (3) The polytetrafluoroethylene cup containing the above mixture was placed in a roller oven, and the roller oven was heated to 85°C, 10 mL of 0.1 mol / L ammonium persulfate initiator solution was added dropwise, and the reaction was continued for 3 h to obtain a viscous liquid, which was dried in an oven at 180°C to obtain a solid product;

[0091] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was the drilling fluid suspending agent.

[0092] Comparative Example 5

[0093] (1) 500 g of deionized water was added to a 1 liter volume polytetrafluoroethylene cup, and 20 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 55 g of allyl sulfonic acid sodium salt, and 10 g of p-styryl sulfonic acid sodium salt were added to the polytetrafluoroethylene cup to obtain a dispersion liquid;

[0094] (2) A 20 wt% sodium carbonate aqueous solution was added to the polytetrafluoroethylene cup to adjust the pH value of the dispersion liquid to 7;

[0095] (3) The polytetrafluoroethylene cup containing the above dispersion liquid was placed in a roller oven, and the roller oven was heated to 180°C and kept at 65°C for 65 h to heat initiate polymerization, and a solid product was obtained;

[0096] (4) The solid product was crushed with a universal crusher and sieved through a 100 mesh sieve to obtain a white powder, which was the drilling fluid suspending agent.

[0097] Experimental Example 1

[0098] A base slurry of 500 mL fresh water + 20 wt% NaCl + 3.0 wt% DSP-1 was prepared, and the density of the base slurry was adjusted to 2.4 g / cm 3 using barite with a density of 4.2 g / cm 3 After stirring and sealing for 24 hours, 1.0 wt% of the drilling fluid suspending agent of Examples 1-6 and Comparative Examples 1-5 was added, respectively, and the slurry was stirred for 20 min to obtain a slurry, which was placed in a 500 mL graduated cylinder to measure the slurry settling performance.

[0099] The slurry was left to stand in an environment of 25±1°C, and the density difference between the upper and lower liquid phases of the slurry was tested using a drilling fluid densitometer. When the density difference was ≥0.02 g / cm 3 , it was recorded as the slurry settling instability time, and the test results are shown in Table 1.

[0100] Table 1 Influence of suspending agent on stability of base slurry

[0101]

[0102] From the data in Table 1, it can be seen that the suspending agent in the examples and the comparative examples is applied to the drilling fluid respectively, the suspending agent in the examples is applied to the drilling fluid, the settling stability of the drilling fluid is obviously better than that of the suspending agent in the comparative examples. Among them, the suspending agent prepared by redox initiation in the comparative example 4 has the worst settling stability when applied to the drilling fluid, which is because the polymer in the suspending agent prepared by redox initiation is a straight chain structure, and its supporting effect on the base slurry is much lower than that of the product synthesized by the thermal initiation polymerization method.

[0103] Figure 1 The morphology diagram of the suspending agent prepared in Example 2 dispersed in the aqueous solution is shown in Figure 1. Figure 1 It can be seen that the suspending agent is unfolded in the aqueous solution, showing a lamellar structure. This lamellar structure can better improve the static shear force of the drilling fluid, and maintain the suspending stability of the drilling fluid through the static shear force, so that the solid particles in the base slurry will not settle.

[0104] Experimental Example 2

[0105] A base slurry of 500 mL fresh water + 20 wt% NaCl + 3.0% wt DSP-1 was prepared, and barite with a density of 4.2 g / cm 3 was used to adjust the density of the base slurry to 2.4 g / cm 3 After stirring and sealing for 24 hours, 1.0 wt% of the drilling fluid suspending agent of Examples 1-6 and Comparative Examples 1-5 was added respectively, and after stirring for 20 min, a slurry was obtained. The slurry was placed in an aging tank, and the aging tank was placed in a high-temperature roller oven, and was heated and rolled at 230°C for 16h, and then cooled to room temperature. After stirring the slurry at 10000 rpm for 20 min, it was placed in a 500 mL measuring cylinder, and the settling performance of the slurry was tested.

[0106] The slurry was placed in an environment of 25±1°C, and the density difference between the upper and lower liquid phases of the slurry was tested by using a drilling fluid densitometer. When the density difference was ≥0.02 g / cm 3 , it was recorded as the settling instability time of the slurry, and the test results are shown in Table 2.

[0107] Table 2 Influence of suspending agent on the stability of base slurry at high temperature

[0108]

[0109] The suspending agent prepared in the embodiments 1-6 of the present application can still maintain the stability of the drilling fluid after high temperature treatment. The suspending agent prepared in the embodiment 2 can be applied to the drilling fluid, and the stability time of the drilling fluid can reach 12 days. In the comparative example 1, the polymer is polymerized in the acidic environment without adjusting the pH, and the polymerization degree is higher than that in the alkaline environment, the polymer chain is longer, and the thickening effect is obvious, but the effect of increasing the viscosity is not obvious, and the polymer chain is more likely to break during the high temperature aging process, so the settling stability after aging is poorer. In the comparative example 2, the heating temperature in step (3) is 150 DEG C, which leads to incomplete polymerization reaction, but further branch chain reaction occurs during the high temperature aging process, so the settling stability is improved. In the comparative examples 3 and 5, the monomers are not completely dissolved, so the participation of the monomers and the arrangement order of the monomers are affected during the thermal initiation polymerization process, the suspending agent has weak temperature resistance, the branch chain structure is relatively simple, and the settling stability is poorer. The straight chain structure of the comparative example 4 not only reduces the supporting effect of the polymer on the base slurry, but also greatly reduces the temperature resistance.

[0110] It should be noted that the above-described embodiments are only used to explain the present application and do not constitute any limitation on the present application. The present application is described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. The present application can be modified within the scope of the claims, and the present application can be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein, on the contrary, the present application can be extended to all other methods and applications with the same function.

Claims

1. A drilling fluid suspending agent, characterized in that, The suspension agent is prepared by thermal initiation polymerization of unsaturated sulfonate, which includes 2-acrylamido-2-methylpropane sulfonate, alkyl alkenyl sulfonate and unsaturated benzene sulfonate.

2. The suspension concentrate according to claim 1, characterized in that, The thermal initiation polymerization conditions include: a mixture containing unsaturated sulfonate and water, which is subjected to thermal initiation polymerization to obtain the suspension agent. Preferably, the pH of the mixture is adjusted to 7-9 before the thermal initiation polymerization to obtain the suspension agent. And / or, the temperature of the thermal initiation polymerization is 180-205℃. And / or, the time of the thermal initiation polymerization is 50-70h.

3. The suspension concentrate according to claim 2, characterized in that, The mass ratio of 2-acrylamido-2-methylpropane sulfonate, alkyl alkenyl sulfonate, unsaturated benzene sulfonate and water is (3-4):(11-12):(2-6):(40-100).

4. The suspension according to any one of claims 1 to 3, characterized in that The alkyl alkenyl sulfonate is at least one of vinyl sulfonate, allyl sulfonate, alkenyl butyl sulfonate and alkenyl pentyl sulfonate; preferably, it is allyl sulfonate. And / or, the unsaturated benzene sulfonate is at least one of p-vinyl benzene sulfonate and (4-vinyl phenyl) methyl sulfonate. And / or, the water is deionized water or distilled water. And / or, the pH of the mixture is adjusted by one or more of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide and sodium ethoxide.

5. A method of preparing a drilling fluid suspending agent, characterized by, The preparation method includes the following steps: the unsaturated sulfonate is subjected to thermal polymerization to obtain the suspension agent; the unsaturated sulfonate includes 2-acrylamido-2-methylpropane sulfonate, alkyl alkenyl sulfonate and unsaturated benzene sulfonate.

6. The production method according to claim 5, wherein The thermal initiation polymerization conditions include: the unsaturated sulfonate is dissolved in water to obtain a mixture, which is subjected to thermal initiation polymerization to obtain the suspension agent. Preferably, the pH of the mixture is adjusted to 7-9 before the thermal initiation polymerization to obtain the suspension agent. And / or, the temperature of the thermal initiation polymerization is 180-205℃. And / or, the time of the thermal initiation polymerization is 50-70h.

7. The production method according to claim 5 or 6, characterized by, The mass ratio of 2-acrylamido-2-methylpropane sulfonate, alkyl alkenyl sulfonate, unsaturated benzene sulfonate and water is (3-4):(11-12):(2-6):(40-100).

8. The method of any one of claims 5 to 7, wherein the method further comprises, The alkyl alkenyl sulfonate is at least one of vinyl sulfonate, allyl sulfonate, alkenyl butyl sulfonate and alkenyl pentyl sulfonate; preferably, it is allyl sulfonate. And / or, the unsaturated benzene sulfonate is at least one of p-vinyl benzene sulfonate and (4-vinyl phenyl) methyl sulfonate. And / or, the water is deionized water or distilled water. And / or, the pH of the mixture is adjusted by one or more of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide and sodium ethoxide.

9. The method of any one of claims 5 to 8, wherein the method further comprises, The thermal initiation polymerization conditions include: the unsaturated sulfonate is dissolved in water to obtain a mixture, which is subjected to thermal initiation polymerization to obtain the suspension agent. Preferably, the stirring time is 15-30min. And / or, the mixture is subjected to thermal initiation polymerization to obtain a solid product, which is pulverized and sieved to obtain the suspension agent.

10. A drilling fluid, characterized by, The suspension agent contains the suspension agent of any one of claims 1-4 or the suspension agent prepared by the preparation method of any one of claims 5-9; preferably, The content of the suspending agent in the drilling fluid is 1wt%-3wt%; further preferably, The sedimentation instability time of the drilling fluid is 10-12d.

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