A plugging agent for polar ultra-low temperature drilling fluid and a preparation method and application thereof

Abstract

The application provides a plugging agent for polar ultra-low temperature drilling fluid and a preparation method and application thereof. The preparation method of the plugging agent comprises the following steps: dispersing nano silicon dioxide into an ethanol aqueous solution, adjusting the pH of the system to 3-5, adding a silane coupling agent, performing reaction, separation and drying to obtain modified nano silicon dioxide; dispersing the modified nano silicon dioxide into isododecane or white oil, adding an oil-soluble monomer, and fully mixing to obtain a mixed solution; mixing the mixed solution and an emulsifier aqueous solution, performing shearing emulsification to obtain an emulsion; adding an initiator, performing reaction, and then performing demulsification, separation and drying to obtain the plugging agent for polar ultra-low temperature drilling fluid. The plugging agent has a core-shell structure, has strong low-temperature resistance, has good dispersibility in the polar ultra-low temperature drilling fluid, and has good plugging effect in the drilling process in the polar ultra-low temperature environment.

Description

TECHNICAL FIELD

[0001] The application relates to a plugging agent for polar ultra-low-temperature drilling fluid and a preparation method and application thereof, and belongs to the technical field of polar drilling. BACKGROUND

[0002] With the deepening of Antarctic scientific research, more than 220 mineral resources such as oil, natural gas, iron and coal have been found around the Antarctic coastal zone. It is of great significance to carry out drilling research on the geological environment under the Antarctic ice. In the Antarctic drilling, the phase change of ice in the ice-rock interlayer and the well wall causes the invasion of low-temperature drilling fluid into the Antarctic stratum, and the drilling fluid plugging agent must be used to maintain the stability of the well wall. However, the conventional plugging agent cannot be applied to the polar ultra-low-temperature drilling fluid and the complex geological environment under the Antarctic ice.

[0003] Chinese patent document CN111849441A discloses a three-component low-temperature oil layer perforation plugging agent. The invention uses calcium oxide as the core material of the microsphere particles, and modified N-isopropyl acrylamide polymer as the shell. By adding short fibers in the polyester structure, the strength of the plugging layer is enhanced. The plugging agent is only suitable for oil layer plugging at a temperature of 30-70 DEG C. Chinese patent document CN111363527A discloses a low-temperature high-strength oil and gas well plugging agent prepared from sulfoaluminate clinker, active admixture, water-soluble organic material and other raw materials. The invention uses sulfoaluminate clinker, active admixture, water-soluble organic material and other raw materials, and under a specific ratio, the plugging agent has the characteristics of fast hour strength development, strong underwater impact resistance, strong acid solubility and good thixotropic performance at 10-60 DEG C, and achieves the purpose of plugging by using its own characteristics. However, the plugging agent cannot be well dispersed in polar ultra-low-temperature drilling fluid, and there is a problem of particle aggregation in the polar ultra-low-temperature environment. Chinese patent document CN114805709A discloses an oil-based drilling fluid anti-ultra-high-temperature nano plugging agent with emulsion stability. The invention uses emulsion polymerization to synthesize a stable modified polystyrene latex as an oil-based drilling fluid nano latex plugging agent. However, the plugging agent has a problem of sedimentation and aggregation in polar ultra-low-temperature drilling fluid.

[0004] Therefore, it is of great significance to develop a plugging agent specially suitable for polar ultra-low-temperature drilling fluid. However, the research on the plugging agent for polar ultra-low-temperature drilling fluid is still in the blank stage, and it is urgent to invent a low-temperature-resistant polar ultra-low-temperature drilling fluid plugging agent for polar use. SUMMARY

[0005] In view of the deficiencies of the prior art, the main purpose of the present application is to solve the problems of poor low-temperature resistance of the drilling fluid plugging agent in the polar drilling process, and the unsuitability of the polar ultra-low-temperature drilling fluid system, and to provide a plugging agent for polar ultra-low-temperature drilling fluid, and a preparation method and application thereof. The plugging agent of the present application has a core-shell structure, has strong low-temperature resistance, has good dispersibility in the polar ultra-low-temperature drilling fluid, and has good plugging effect when applied in the polar ultra-low-temperature drilling process.

[0006] The technical scheme of the present application is as follows:

[0007] A plugging agent for polar ultra-low-temperature drilling fluid, which is a core-shell structure plugging agent with modified nano-silicon dioxide as the core and a polymer material as the shell.

[0008] According to the present application, the modified nano-silicon dioxide is prepared by surface modification of nano-silicon dioxide with γ-methacryloxypropyltrimethoxysilane or γ-aminopropyltriethoxysilane; and the particle size of the nano-silicon dioxide is 20-200 nm.

[0009] According to the present application, the polymer material is prepared by polymerization of oil-soluble monomers; and the oil-soluble monomers are one or a combination of two or more of styrene, lauryl methacrylate, methyl methacrylate, octadecyl methacrylate, or acrylic acid.

[0010] The preparation method of the above-mentioned plugging agent for polar ultra-low-temperature drilling fluid comprises the following steps:

[0011] (1) Disperse the nano-silicon dioxide into an ethanol aqueous solution, adjust the pH of the system to 3-5, add a silane coupling agent, react, separate, and dry to obtain modified nano-silicon dioxide;

[0012] (2) Disperse the modified nano-silicon dioxide into isododecane or white oil, add oil-soluble monomers, and mix thoroughly to obtain a mixed solution;

[0013] (3) Mix the mixed solution and an aqueous emulsifier solution, shear emulsify to obtain an emulsion, add an initiator, react, then demulsify, separate, and dry to obtain the plugging agent for polar ultra-low-temperature drilling fluid.

[0014] According to the present application, in step (1), the mass ratio of ethanol to water in the ethanol aqueous solution is 1:0.5-2; and the mass ratio of nano-silicon dioxide to the ethanol aqueous solution is 1:8-10.

[0015] According to the present application, in step (1), a 10%-20% hydrochloric acid aqueous solution is used to adjust the pH.

[0016] According to the application, preferably, in step (1), the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570) or γ-aminopropyltriethoxysilane.

[0017] According to the application, preferably, in step (1), the mass ratio of the nanosilica to the silane coupling agent is 20:1-6, preferably 20:1-5.

[0018] According to the application, preferably, in step (1), the reaction temperature is 80-120℃, preferably 80℃; the reaction time is 8-12h, preferably 8h, and the reaction is carried out under stirring.

[0019] According to the application, preferably, in step (2), the mass ratio of the nanosilica in step (1) to isododecane is 1:9-12, preferably 1:10.

[0020] According to the application, preferably, in step (2), the oil-soluble monomer is one of styrene, lauryl methacrylate, methyl methacrylate, octadecyl methacrylate or acrylic acid, or a combination of two or more thereof; preferably, the oil-soluble monomer is a combination of styrene, lauryl methacrylate and acrylic acid, wherein the mass ratio of styrene, lauryl methacrylate and acrylic acid is 1-5:1-3:1, preferably 2-5:1-3:1.

[0021] According to the application, preferably, in step (2), the mass ratio of the oil-soluble monomer to the nanosilica in step (1) is 1:1-3, preferably 1:2.

[0022] According to the application, preferably, in step (3), the emulsifier is Span80 or Span60; and in the aqueous emulsifier solution, the mass ratio of the emulsifier to water is 1:5-15.

[0023] According to the application, preferably, in step (3), the mass ratio of the emulsifier in the aqueous emulsifier solution to the nanosilica in step (1) is 1:1-3.

[0024] According to the application, preferably, in step (3), the shearing emulsification time is 10-20min, the shearing emulsification temperature is 50-70℃, and the shearing rate of the shearing emulsification is 2000-4000r / min.

[0025] According to the application, preferably, in step (3), the initiator is potassium persulfate; and the mass ratio of the initiator to the oil-soluble monomer in step (2) is 1:100-200.

[0026] According to the application, preferably, in step (3), the reaction temperature is 60-100℃, preferably 80℃; and the reaction time is 4-8h, preferably 8h.

[0027] Preferably, in step (3), the reaction is carried out under stirring in an inert gas atmosphere; preferably, the inert gas is nitrogen or argon.

[0028] The polar super-low temperature drilling fluid plugging agent is used for plugging in a polar stratum or in a polar super-low temperature drilling fluid.

[0029] Preferably, the polar super-low temperature drilling fluid plugging agent is added in an amount of 1-5 wt%.

[0030] Preferably, the polar region is the South Pole.

[0031] The technical features and advantages of the present application are as follows:

[0032] 1. The plugging agent has a core-shell structure, uses rigid inorganic nano-silica particles as the core, and uses a flexible polymer material as the shell; the plugging agent can prevent mass transfer and heat transfer between the drilling fluid and the ice-rock interlayer by adsorbing the stratum, thereby avoiding phase change of the ice layer in the ice-rock interlayer; the rigid core plays a supporting and bridging role, and plays a plugging role on the rock stratum in the ice-rock interlayer; the shell layer made of oil-soluble monomers can increase the deformability of the plugging agent to adapt to stratum pores of different sizes.

[0033] 2. The polar super-low temperature drilling fluid core-shell plugging agent has strong low-temperature resistance, good adaptability to existing polar super-low temperature drilling fluids, good dispersion in the polar super-low temperature drilling base fluid, and does not weaken the strength, can reach the target stratum with the drilling base fluid to achieve the plugging effect, and has good plugging effect.

[0034] 3. The polar super-low temperature drilling fluid core-shell plugging agent is simple and fast to synthesize, is green, safe, and environmentally friendly, has no irritation, toxicity, or allergic reaction to human tissues, meets the strict requirements of Antarctic drilling on environmental protection, and provides technical support for polar drilling.

[0035] 4. In the preparation method, the nano-silica particle size needs to be less than 500 nm, and a large particle size will cause the plugging agent to fail to form an effective shell layer. The oil phase in the solvent is selected as isododecane liquid, which facilitates the direct participation of the oil-soluble monomer in the reaction, thereby forming an effective plugging agent shell layer. The specific type and ratio of the shell monomers in the present application, combined with specific modified nano-silica and a specific preparation method, can achieve the excellent effects of the present application. DETAILED DESCRIPTION

[0036] The present application will be further described below through specific examples, but is not limited thereto.

[0037] In the examples, the experimental methods are conventional methods unless otherwise specified; and the reagents and materials used are commercially available unless otherwise specified.

[0038] Example 1

[0039] A preparation method of a plugging agent for polar ultra-low temperature drilling fluid, the steps are as follows:

[0040] (1) 10 g of nano-silicon dioxide with a particle size of 20 nm is fully dispersed in 90 g of an ethanol aqueous solution, wherein the mass ratio of ethanol to water is 1:1, a hydrochloric acid aqueous solution with a mass concentration of 15% is used to adjust the pH of the solution system to about 4, 1.5 g of silane coupling agent KH570 is added, stirring is performed at 80°C for 8 h, cooling, centrifugal separation, and drying are performed to obtain modified nano-silicon dioxide.

[0041] (2) The modified nano-silicon dioxide obtained in step (1) is fully dispersed in 100 g of isododecane liquid to obtain mixture A; oil-soluble monomers are added to mixture A, the oil-soluble monomers including 3 g of styrene, 1 g of lauryl methacrylate, and 1 g of acrylic acid, uniform stirring is performed at a rotation speed of 350 r / min, and heating is performed to 60°C to obtain mixture B;

[0042] (3) 4 g of emulsifier Span80 is added to 46 g of deionized water, stirring is performed at a rotation speed of 600 r / min, and heating is performed to 60°C to obtain an emulsifier aqueous solution; then mixture B is added to the emulsifier aqueous solution, and emulsification is performed by shearing to obtain an emulsion, the shearing emulsification time is 15 min, the shearing emulsification temperature is 60°C, and the shearing rate of shearing emulsification is 3000 r / min; the emulsion is heated to 80°C, nitrogen is introduced, 0.05 g of initiator potassium persulfate is added, reaction is performed for 8 h, demulsification is performed after reaction, the obtained reaction product is subjected to centrifugal separation and drying, and the obtained product is the plugging agent for polar ultra-low temperature drilling fluid.

[0043] Example 2

[0044] A preparation method of a plugging agent for polar ultra-low temperature drilling fluid, the steps are as follows:

[0045] (1) 10 g of nano-silicon dioxide with a particle size of 100 nm is fully dispersed in 90 g of an ethanol aqueous solution, wherein the mass ratio of ethanol to water is 1:1, a hydrochloric acid aqueous solution with a mass concentration of 15% is used to adjust the pH of the solution system to about 4, 1.5 g of silane coupling agent KH570 is added, stirring is performed at 80°C for 8 h, cooling, centrifugal separation, and drying are performed to obtain modified nano-silicon dioxide.

[0046] (2) The modified nano-silicon dioxide obtained in step (1) is fully dispersed in 100 g of isododecane liquid to obtain mixture A; oil-soluble monomers are added to mixture A, the oil-soluble monomers including 5 g of styrene, 3 g of lauryl methacrylate, and 2 g of acrylic acid, uniform stirring is performed at a rotation speed of 350 r / min, and heating is performed to 60°C to obtain mixture B;

[0047] (3) 4 g emulsifier Span 80 was added to 46 g deionized water, stirred at a speed of 600 r / min, heated to 60°C to obtain an emulsifier aqueous solution; then the mixture B was added to the emulsifier aqueous solution, and emulsification was performed to obtain an emulsion, the emulsification time was 15 min, the emulsification temperature was 60°C, and the emulsification shear rate was 3000 r / min; the emulsion was heated to 80°C, nitrogen was introduced, and 0.05 g of initiator potassium persulfate was added for reaction, the reaction time was 8 h, the reaction was completed, and demulsification was performed, the obtained reaction product was centrifuged and dried, and the obtained product was the plugging agent for polar ultra-low temperature drilling fluid.

[0048] Example 3

[0049] A preparation method of a plugging agent for polar ultra-low temperature drilling fluid, the steps being as follows:

[0050] (1) 10 g of nano-silicon dioxide with a particle size of 200 nm was fully dispersed in 90 g of an ethanol aqueous solution, the mass ratio of ethanol and water being 1:1, a 15% hydrochloric acid aqueous solution was used to adjust the pH of the solution system to about 4, 1.5 g of silane coupling agent KH570 was added, and stirring was performed at 80°C for 8 h, and then the mixture was cooled, centrifuged, and dried to obtain modified nano-silicon dioxide.

[0051] (2) The modified nano-silicon dioxide obtained in step (1) was fully dispersed in 100 g of isododecane liquid to obtain mixture A; oil-soluble monomers were added to the mixture A, the oil-soluble monomers including 5 g of styrene, 3 g of lauryl methacrylate, and 1 g of acrylic acid, and the mixture was stirred at a speed of 350 r / min and heated to 60°C to obtain mixture B;

[0052] (3) 4 g emulsifier Span 80 was added to 46 g deionized water, stirred at a speed of 600 r / min, heated to 60°C to obtain an emulsifier aqueous solution; then the mixture B was added to the emulsifier aqueous solution, and emulsification was performed to obtain an emulsion, the emulsification time was 15 min, the emulsification temperature was 60°C, and the emulsification shear rate was 3000 r / min; the emulsion was heated to 80°C, nitrogen was introduced, and 0.05 g of initiator potassium persulfate was added for reaction, the reaction time was 8 h, the reaction was completed, and demulsification was performed, the obtained reaction product was centrifuged and dried, and the obtained product was the plugging agent for polar ultra-low temperature drilling fluid.

[0053] Example 4

[0054] A preparation method of a plugging agent for polar ultra-low temperature drilling fluid, the steps being as follows:

[0055] (1) 10 g nano-silica with a particle size of 20 nm was dispersed into 90 g of an ethanol aqueous solution, wherein the mass ratio of ethanol to water was 1:1, the pH of the solution system was adjusted to about 4 using a 15% hydrochloric acid aqueous solution, 1.5 g of silane coupling agent KH570 was added, and the mixture was stirred at 80°C for 8 h, cooled, centrifuged, and dried to obtain modified nano-silica.

[0056] (2) The modified nano-silica obtained in step (1) was dispersed into 100 g of isododecane liquid to obtain mixture A; oil-soluble monomers were added to mixture A, the oil-soluble monomers including 5 g of styrene, 2 g of methyl methacrylate, and 1 g of acrylic acid, and the mixture was stirred at 350 r / min and heated to 60°C to obtain mixture B;

[0057] (3) 5 g of emulsifier Span80 was added to 45 g of deionized water, and the mixture was stirred at 600 r / min and heated to 60°C to obtain an emulsifier aqueous solution; then, mixture B was added to the emulsifier aqueous solution, and emulsification was performed by shearing to obtain an emulsion, the shearing emulsification time was 15 min, the shearing emulsification temperature was 60°C, and the shearing rate of shearing emulsification was 3000 r / min; the emulsion was heated to 80°C, nitrogen was introduced, 0.05 g of initiator potassium persulfate was added, and the mixture was reacted for 8 h; after the reaction was completed, the product was separated by centrifugation and dried, and the obtained product was a plugging agent for polar ultra-low temperature drilling fluid.

[0058] Example 5

[0059] A method for preparing a plugging agent for polar ultra-low temperature drilling fluid, the steps being as follows:

[0060] (1) 10 g nano-silica with a particle size of 200 nm was dispersed into 90 g of an ethanol aqueous solution, wherein the mass ratio of ethanol to water was 1:1, the pH of the solution system was adjusted to about 4 using a 15% hydrochloric acid aqueous solution, 1.5 g of silane coupling agent KH570 was added, and the mixture was stirred at 80°C for 8 h, cooled, centrifuged, and dried to obtain modified nano-silica.

[0061] (2) The modified nano-silica obtained in step (1) was dispersed into 100 g of isododecane liquid to obtain mixture A; oil-soluble monomers were added to mixture A, the oil-soluble monomers including 5 g of styrene, 2 g of methyl methacrylate, and 1 g of acrylic acid, and the mixture was stirred at 350 r / min and heated to 60°C to obtain mixture B;

[0062] (3) 4 g of emulsifier Span 80 was added into 46 g of deionized water, and stirred at a rotation speed of 600 r / min to heat to 60°C to obtain an emulsifier aqueous solution; then the mixture B was added into the emulsifier aqueous solution, and sheared to emulsify to obtain an emulsion, the shearing emulsification time was 15 min, the shearing emulsification temperature was 60°C, and the shearing rate of shearing emulsification was 3000 r / min; the emulsion was heated to 80°C, nitrogen was introduced, 0.05 g of initiator potassium persulfate was added for reaction, the reaction time was 8 h, demulsification was performed after the reaction was completed, the obtained reaction product was subjected to centrifugal separation and drying, and the obtained product was the plugging agent for polar ultra-low temperature drilling fluid.

[0063] Example 6

[0064] A preparation method of a plugging agent, as described in Example 5, except that no styrene was added in step (2); and the other steps and conditions were the same as in Example 1.

[0065] Example 7

[0066] A preparation method of a plugging agent, as described in Example 5, except that no lauryl methacrylate monomer was added in step (2); and the other steps and conditions were the same as in Example 1.

[0067] Example 8

[0068] A preparation method of a plugging agent, as described in Example 5, except that no acrylic acid monomer was added in step (2); and the other steps and conditions were the same as in Example 1.

[0069] Example 9

[0070] A preparation method of a plugging agent, as described in Example 5, except that Span 60 was used as the emulsifier in step (3); and the other steps and conditions were the same as in Example 1.

[0071] Example 10

[0072] A preparation method of a plugging agent, as described in Example 5, except that the particle size of the nano-silicon dioxide used in step (1) was 100 nm; and the other steps and conditions were the same as in Example 1.

[0073] Example 11

[0074] A preparation method of a plugging agent, as described in Example 5, except that the silane coupling agent in step (1) was KH550 (or γ-aminopropyl triethoxysilane); and the other steps and conditions were the same as in Example 1.

[0075] Example 12

[0076] A method for preparing a plugging agent, as described in Example 5, except that in step (2) isododecane is replaced by white oil; other steps and conditions are the same as in Example 1.

[0077] Example 13

[0078] A method for preparing a plugging agent, as described in Example 5, except that in step (2) oil-soluble monomer lauryl methacrylate is replaced by octadecyl methacrylate; other steps and conditions are the same as in Example 1.

[0079] Example 14

[0080] A method for preparing a plugging agent, as described in Example 5, except that in step (1) the amount of silane coupling agent KH570 is 3 g; other steps and conditions are the same as in Example 1.

[0081] Example 15

[0082] A method for preparing a plugging agent, as described in Example 5, except that in step (2) the oil-soluble monomers include 3 g of styrene, 2 g of lauryl methacrylate, and 2 g of acrylic acid; other steps and conditions are the same as in Example 1.

[0083] Comparative Example 1

[0084] A method for preparing a plugging agent, as described in Example 5, except that the nano-silica is not modified, and the specific preparation steps are as follows:

[0085] (1) 10 g of nano-silica with a particle size of 200 nm is fully dispersed in 100 g of isododecane liquid to obtain a mixture A; oil-soluble monomers are added to the mixture A, the oil-soluble monomers include 3 g of styrene, 1 g of lauryl methacrylate, and 1 g of acrylic acid, and the mixture is stirred uniformly at a speed of 350 r / min and heated to 60°C to obtain a mixture B;

[0086] (2) 4 g of emulsifier Span80 is added to 46 g of deionized water, stirred at a speed of 600 r / min, and heated to 60°C to obtain an emulsifier aqueous solution; then the mixture B is added to the emulsifier aqueous solution, and emulsified by shearing to obtain an emulsion, the shearing emulsification time is 15 min, the shearing emulsification temperature is 60°C, and the shearing rate of shearing emulsification is 3000 r / min; the emulsion is heated to 80°C, nitrogen is introduced, 0.05 g of initiator potassium persulfate is added, and the reaction is carried out for 8 h, the reaction is finished, and the obtained reaction product is centrifuged, dried, and the obtained product is the plugging agent.

[0087] Comparative Example 2

[0088] A preparation method of a plugging agent, as described in Example 5, except that no emulsifier is added, and the specific preparation steps are as follows:

[0089] Step (1) is the same as in Example 5;

[0090] Step (2) is the same as in Example 5;

[0091] Step (3): Heat mixture B to 80°C, introduce nitrogen, and add 0.05 g of initiator potassium persulfate to react for 8 h. After the reaction is completed, demulsification is performed, and the obtained reaction product is separated by centrifugation and dried. The obtained product is the plugging agent.

[0092] Test Example

[0093] The plugging agents prepared in the examples and comparative examples are characterized and evaluated for performance as follows:

[0094] 1. Basic performance of the plugging agent

[0095] Contact angle measurement:

[0096] Weigh 10 g of the sample, and use a hydraulic press to press it into a thin sheet under the condition of 10 MPa for 10 min. The surface of the pressed sheet is polished smooth with fine sandpaper, and the contact angle of isododecane on the surface of the plugging agent at room temperature and -55°C is measured using a contact angle instrument. The isododecane needs to be frozen in a -55°C refrigerator for 24 hours before the contact angle at -55°C is measured. The test results are shown in Table 1.

[0097] Table 1. Performance test of the plugging agent

[0098]

[0099]

[0100] As can be seen from the data in Table 1, the product of the example completely spreads with the oil phase isododecane, indicating that the plugging agent prepared in the example has good dispersibility in isododecane at room temperature and low temperature.

[0101] 2. Effect of the plugging agent on the performance of the polar drilling fluid base mud

[0102] (1) Preparation of the polar drilling fluid base mud

[0103] The drilling fluid base mud is prepared according to the following formula and steps, and the density is 0.9 g / cm 3 .

[0104] Formula: Add the weighting agent ENASOLV MC to the base fluid isododecane, and the mass ratio of the base fluid to the weighting agent is 7:3. Then add 2 wt% of organic bentonite relative to the weight of the base fluid, and mix well.

[0105] (2) Sand bed plugging experiment

[0106] The invasion depth of the above oil-based drilling fluid into a 140-160 mesh sand bed was tested using a visual sand bed plugging device equipped with a circulating refrigeration device, and the plugging performance of the plugging agent was studied at a temperature of -55°C. The drilling fluid was frozen and aged at -55°C for 16 hours before measurement. The test pressure was 0.7 MPa, and the test time was 30 minutes. The results are shown in Table 2.

[0107] Table 2 Plugging effect of plugging agent

[0108]

[0109]

[0110] As can be seen from Table 2, the invasion depth of the polar drilling fluid base slurry is deeper than that of the examples under the condition of -55°C, indicating that the products of the examples all have certain plugging performance. The results show that the results of Examples 6-8 show that the lack of a certain monomer will lead to a less tight structure of the shell part to the core part under polar ultra-low temperature conditions, thereby reducing the plugging effect; the results of Example 9 show that although the emulsifier does not participate in the synthesis reaction, it will affect the particle size and uniformity of the plugging agent, and has a certain influence on the plugging effect; the results of Example 10 show that the size of the nanoparticles has a certain influence on the effect of the plugging agent. The results of Examples 11-15 show that the type of silane coupling agent, the type of solvent, the type of oil-soluble monomer, the amount of silane coupling agent, and the amount of oil-soluble monomer affect the plugging effect of the plugging agent. Comparative Example 1 shows that the unmodified nano-silicon dioxide will reduce the plugging effect, and the results of Comparative Example 2 show that the plugging agent synthesized without emulsifier does not work.

[0111] 3. Drilling fluid rheological property experiment

[0112] (1) Preparation of polar drilling fluid base slurry

[0113] The drilling fluid base slurry was prepared according to the following formula and steps, and the density was 0.9 g / cm 3 .

[0114] Formula: Add weighting agent ENASOLV MC to base fluid isododecane, the mass ratio of base fluid to weighting agent is 7:3, then add 2wt% of organic bentonite relative to the weight of the base fluid, and mix thoroughly.

[0115] (2) Rheological property test

[0116] The plugging agent prepared in Example 5 was added to the above base slurry, and the rheological property of the drilling fluid was tested at room temperature and -55°C using a six-speed rotary viscometer to evaluate the compatibility of the plugging agent with the drilling fluid base fluid. The results are shown in Table 3.

[0117] Table 3 drilling fluid rheological property influence

[0118]

[0119]

[0120] As shown in Table 3, the viscosity and shear force of the drilling fluid are increased after the blocking agent is added under two conditions, and the viscosity and shear force of the drilling fluid are increased with the increase of the blocking agent, and the rheological property difference between-55 DEG C and room temperature is small, which indicates that the blocking agent has good compatibility with the drilling fluid under low temperature condition.

[0121] In conclusion, the polar drilling fluid blocking agent can keep good strength under polar ultra-low temperature, effectively block the formation, and meet the needs of drilling work under the Antarctic polar ultra-low temperature environment.

[0122] The above describes the preferred embodiments of the present application, but the present application is not limited to the specific details in the above-described embodiments, and within the technical concept of the present application, the technical solutions of the present application can be variously modified, and these simple modifications all belong to the protection scope of the present application.

[0123] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0124] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the technical concept of the present application, and it should be considered as disclosed content of the present application.

Claims

1. The use of a polar ultra-low temperature drilling fluid plugging agent in plugging a polar formation or in a polar ultra-low temperature drilling fluid, characterized in that, The plugging agent is a core-shell structure plugging agent with modified nano-silica as the core and polymer material as the shell; The modified nano-silica is prepared by surface modification of nano-silica with γ-methacryloxypropyl trimethoxysilane or γ-aminopropyl triethoxysilane; the particle size of the nano-silica is 20-200 nm; the polymer material is prepared by polymerization of oil-soluble monomers; the oil-soluble monomers are one or a combination of more than two of styrene, lauryl methacrylate, methyl methacrylate, octadecyl methacrylate or acrylic acid; The preparation method of the plugging agent for polar ultra-low temperature drilling fluid comprises the following steps: (1) dispersing nano-silica into an ethanol aqueous solution, adjusting the pH of the system to 3-5, adding a silane coupling agent, reacting, separating, and drying to obtain modified nano-silica; (2) dispersing the modified nano-silica into isododecane or white oil, adding oil-soluble monomers, and mixing uniformly to obtain a mixed solution; (3) mixing the mixed solution and an emulsifier aqueous solution, shearing and emulsifying to obtain an emulsion, adding an initiator, reacting, then demulsifying, separating, and drying to obtain the plugging agent for polar ultra-low temperature drilling fluid.

2. Use according to claim 1, characterized in that, In step (1), one or more of the following conditions is included: i. In the ethanol aqueous solution, the mass ratio of ethanol to water is 1:0.5-2; the mass ratio of nano-silica to the ethanol aqueous solution is 1:8-10; ii. A 10%-20% mass concentration hydrochloric acid aqueous solution is used to adjust the pH; iii. The silane coupling agent is γ-methacryloxypropyl trimethoxysilane (KH570) or γ-aminopropyl triethoxysilane; iv. The mass ratio of nano-silica to the silane coupling agent is 20:1-6; v. The reaction temperature is 80-120°C; the reaction time is 8-12 h, and the reaction is carried out under stirring.

3. Use according to claim 1, characterized in that, In step (2), one or more of the following conditions is included: i. The mass ratio of the nano-silica in step (1) to isododecane is 1:9-12; ii. The oil-soluble monomers are one or a combination of more than two of styrene, lauryl methacrylate, methyl methacrylate, octadecyl methacrylate or acrylic acid; iii. The mass ratio of the oil-soluble monomers to the nano-silica in step (1) is 1:1-3.

4. Use according to claim 3, characterized in that, The oil-soluble monomers are a combination of styrene, lauryl methacrylate and acrylic acid, and the mass ratio of styrene, lauryl methacrylate and acrylic acid is 1-5:1-3:

1.

5. The use according to claim 1, characterized in that, In step (3), one or more of the following conditions is included: i. The emulsifier is Span80 or Span60; in the emulsifier aqueous solution, the mass ratio of the emulsifier to water is 1:5-15; ii. The mass of the emulsifier in the emulsifier aqueous solution and the mass of the nano-silica in step (1) are in a mass ratio of 1:1-3; iii. The shearing and emulsifying time is 10-20 min, the shearing and emulsifying temperature is 50-70°C, and the shearing rate of shearing and emulsification is 2000-4000 r / min.

6. Use according to claim 1, characterized in that, In step (3), one or more of the following conditions is included: i. The initiator is potassium persulfate; the mass ratio of the initiator to the oil-soluble monomer in step (2) is 1:100-200; ii. The reaction temperature is 60-100℃; the reaction time is 4-8h; iii. The reaction is carried out under the conditions of inert gas protection and stirring; the inert gas is nitrogen or argon.

7. Use according to claim 1, characterized in that, The addition amount of the plugging agent in the polar ultra-low temperature drilling fluid is 1-5wt%.

8. The use according to claim 1, characterized in that, The polar region is the South Pole.

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