A high-temperature stable microsphere matrix and microsphere derivative emulsion, a preparation method thereof and application thereof in drilling fluids

Abstract

This invention provides a high-temperature stable microsphere matrix and microsphere derivative emulsion, its preparation method, and its application in drilling fluids. The high-temperature stable microsphere matrix is ​​synthesized using styrene, sodium styrene sulfonate, emulsifier, and initiator as raw materials; the microsphere derivative is obtained by adding functional monomers during the microsphere matrix preparation process. The microsphere matrix and its derivatives of this invention maintain morphological and dispersion stability in a 200℃ aqueous dispersion system. In high-temperature drilling fluids, they can significantly reduce drilling fluid filtration loss and seal core pores, exhibiting excellent sealing and filtration loss reduction effects, and can be applied to deep and ultra-deep well drilling fluids.

Description

Technical Field

[0001] This invention relates to a high-temperature stable microsphere matrix and microsphere derivative emulsion, its preparation method and its application in drilling fluids, belonging to the field of drilling technology. Background Technology

[0002] With the gradual depletion of shallow oil and gas reserves, deep oil and gas has become a key focus for increasing reserves and production in my country. my country possesses abundant deep oil and gas resources, but the accompanying high temperatures, high pressures, and complex formation conditions severely restrict their development. Drilling fluid, the lifeblood of drilling, often fails to function properly due to high temperatures during deep drilling. This allows the drilling fluid to seep into the formation along fractures, leading to wellbore collapse, leakage, and reservoir damage, causing significant economic losses and severely impacting the progress of oil and gas exploration and development. Currently, plugging agents are mainly divided into rigid and flexible plugging agents. Rigid materials such as silica and calcium carbonate have strong high-temperature resistance but poor interaction with the formation and ineffective plugging. Flexible plugging agents are mainly microsphere polymer plugging agents, but polymer plugging agents suffer from high-temperature degradation and cross-linking repolymerization. At high temperatures, the polymer plugging agent shrinks or enlarges, making it unable to effectively seal the target pore fractures and causing economic instability. Chinese patent document CN112812245A proposes a high-temperature resistant pressure-bearing plugging agent for water-based drilling fluids and its preparation method, but its sand bed plugging performance is significantly reduced after exposure to 200℃. Chinese patent document CN111499790A proposes a high-temperature resistant polymer microsphere nano-plugging agent for water-based drilling fluids and its preparation method, but the microspheres exhibit a nearly 40% reduction in particle size at high temperatures.

[0003] Currently, the high-temperature stability of plugging microspheres has not been well resolved, and there is an urgent need to develop a high-temperature stable microsphere to solve the problem of plugging micropores in deep formations. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-temperature stable microsphere matrix and microsphere derivative emulsion, its preparation method, and its application in drilling fluids. The microsphere matrix and its derivatives of this invention maintain morphological and dispersion stability in an aqueous dispersion system at 200°C, and can effectively improve drilling fluid stability, reduce drilling fluid filtration loss, and regulate drilling fluid rheology, making it applicable to deep and ultra-deep oil and gas drilling.

[0005] The technical solution of the present invention is as follows:

[0006] A high-temperature stable microsphere matrix emulsion is prepared by polymerizing a comonomer, an emulsifier, and an initiator I in water; the comonomer is styrene and sodium styrene sulfonate; based on 100 parts by mass of water, the comonomer comprises 20-50 parts, the emulsifier comprises 0.1-1 parts, and the initiator I comprises 0.2-0.8% of the comonomer mass.

[0007] According to a preferred embodiment of the present invention, the mass ratio of styrene to sodium styrene sulfonate in the comonomer is 1:0.25-0.75, and more preferably 1:0.3-0.5.

[0008] According to a preferred embodiment of the present invention, the emulsifier is sodium alkylphenol ether sulfosuccinate (emulsifier MS-1) or disodium lauryl ether sulfosuccinate (MES).

[0009] According to a preferred embodiment of the present invention, the initiator I is ammonium persulfate and / or potassium persulfate.

[0010] According to a preferred embodiment of the present invention, the preparation method of the above-mentioned high-temperature stable microsphere matrix emulsion includes the following steps:

[0011] Comonomers and emulsifiers are added to water and shear emulsification is performed. The resulting emulsion is heated to 60-85°C under a nitrogen atmosphere. Initiator I is then added and the reaction is carried out under a nitrogen atmosphere. The resulting white emulsion is the high-temperature stable microsphere matrix emulsion.

[0012] More preferably, the shear emulsification step is: shear emulsification at a shear rate of 2000-3000 r / min for 10-30 min using a shear emulsifier;

[0013] More preferably, the initiator I is added to the system in the form of an aqueous solution of initiator I, and the concentration of the aqueous solution of initiator I is 0.1-0.2 g / mL;

[0014] More preferably, the reaction time is 1-4 hours; the stirring rate during the reaction process is 1200-1800 r / min.

[0015] This invention also provides a method for preparing a high-temperature stable microsphere derivative emulsion, comprising the following steps:

[0016] (1) Preparation of high temperature stable microsphere matrix

[0017] Comonomers and emulsifiers are added to water and shear emulsification is performed. Under a nitrogen atmosphere, the resulting emulsion is heated to 60-85℃, then initiator I is added, and the reaction is carried out under a nitrogen atmosphere for 0.5-1h to obtain the reaction solution.

[0018] (2) Preparation of high temperature stable microsphere derivatives

[0019] Add a functional monomer solution containing initiator II to the reaction solution in step (1), and continue the reaction for 1-4 hours under a nitrogen atmosphere at 60-85°C. The resulting white emulsion is the high-temperature stable microsphere derivative emulsion.

[0020] According to the present invention, the types and proportions of raw materials and the shear emulsification conditions in step (1) are the same as those in the preparation of the aforementioned high-temperature stable microsphere matrix emulsion.

[0021] According to a preferred embodiment of the present invention, the functional monomer in step (2) is one or a combination of two or more of acrylamide, acrylic acid, dimethyl diallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and (3-acrylamidopropyl)trimethyl ammonium chloride.

[0022] According to a preferred embodiment of the present invention, the mass of the functional monomer in step (2) is 1-30% of the mass of the comonomer, and more preferably 6-15%.

[0023] According to a preferred embodiment of the present invention, the initiator II in step (2) is ammonium persulfate and / or potassium persulfate; the mass of the initiator II is 0.2-0.8% of the mass of the functional monomer.

[0024] According to a preferred embodiment of the present invention, the functional monomer solution containing initiator II in step (2) is obtained by adding the functional monomer and initiator II to water, wherein the concentration of the functional monomer in the functional monomer solution containing initiator II is 0.3-0.5 g / mL.

[0025] The present invention also provides a high-temperature stable microsphere derivative emulsion, which is prepared by the above preparation method.

[0026] According to the present invention, the application of the above-mentioned high-temperature stable microsphere matrix emulsion or high-temperature stable microsphere derivative emulsion in water-based drilling fluid is used for drilling fluid plugging.

[0027] A water-based drilling fluid comprising the above-mentioned high-temperature stable microsphere matrix emulsion or high-temperature stable microsphere derivative emulsion, and further comprising bentonite slurry, filtration loss reducer, and commonly used oilfield treatment agent; 20-50g of high-temperature stable microsphere matrix emulsion or high-temperature stable microsphere derivative emulsion is added to each 1L of drilling fluid.

[0028] More preferably, the filtration loss reducing agent is one of sulfonated phenolic resin, DSP-1, and DSP-2;

[0029] More preferably, the commonly used oilfield treatment agents include, but are not limited to, lubricants, viscosity improvers, viscosity reducers, speed-up agents, and plugging agents, such as RH-3, sulfonated asphalt, NP-1, etc.

[0030] According to the present invention, the preparation method of the above-mentioned water-based drilling fluid is a commonly used method in the art; preferably, the preparation method includes the following steps: under high-speed stirring at 6000-8000 r / min, add 4 parts of bentonite and 0.3 parts of anhydrous sodium carbonate to 100 parts of water, stir for 2 hours, and then cure naturally at room temperature for 24 hours to obtain bentonite slurry; after stirring the bentonite slurry at high speed at 6000-8000 r / min for 20 minutes, add a filtration loss reducer, stir for 20 minutes, then add a commonly used oilfield treatment agent and stir at high speed for 20 minutes, then add a high-temperature stable microsphere matrix emulsion or derivative emulsion and stir for 20 minutes.

[0031] The technical features and beneficial effects of this invention are as follows:

[0032] 1. The high-temperature stable microsphere matrix of this invention is prepared by copolymerizing styrene and sodium styrene sulfonate monomers in a specific ratio via an emulsion reaction. This invention utilizes the easy spheroidization characteristic of styrene emulsion polymerization and introduces sodium styrene sulfonate as a comonomer, enabling the microspheres to achieve hydrophilicity and stable dispersion in water. Furthermore, the introduction of benzenesulfonic acid groups enhances the stability of its molecular structure, preventing thermal degradation in an aqueous phase at 200°C and maintaining its morphology and dispersion stability, thus significantly improving the morphology and dispersion stability of styrene polymers in aqueous phase. Due to the inherent high-temperature stability of the microspheres, the high-temperature stable microsphere derivative can be applied in the development of deep and ultra-deep oil and gas reservoirs.

[0033] 2. This invention uses high-temperature stable microspheres as a matrix and further introduces specific functional monomers to obtain microsphere derivatives. These derivatives are mainly used in high-temperature and ultra-high-temperature drilling fluids. The introduction of more adsorption groups enhances the interaction strength between the microspheres and clay in the drilling fluid, making it easier for the microspheres to synergistically form mud cakes and seal mud cake pores, improving mud cake quality and the stability of microsphere plugging, and reducing drilling fluid filtration loss. Extensive experiments have shown that the introduced functional monomers, while improving plugging and filtration loss reduction performance, have minimal impact on the stability of the microspheres. Other commonly used drilling fluid treatment agents, such as 2-acrylamide-2-methylpropanesulfonic acid or propanesulfonic acid, as comonomers or functional monomers, can affect the dispersion and high-temperature stability of the microsphere matrix or microsphere derivatives, and have limited improvement on drilling fluid plugging and filtration loss reduction performance. Furthermore, an excessively high proportion of functional monomers increases the microsphere deformation rate and reduces stability, thus decreasing both plugging and filtration loss reduction performance.

[0034] 3. The microsphere derivative of this invention enters the rock pores under the pressure difference between drilling fluid and formation fluid, and is firmly adsorbed onto the rock surface through electrostatic attraction, preventing drilling fluid from invading the formation and thus stabilizing the wellbore. The particle size of the microspheres can be adjusted by the amount of monomer added, the amount of emulsifier added, and the rotation speed to adapt to different drilling fluids and formations.

[0035] 4. The emulsion polymerization method used in this invention is used to prepare high-temperature stable microsphere matrix and its derivatives. The preparation method is simple, and the emulsion can be used directly after preparation without further separation. The resulting emulsion itself is an aqueous dispersion phase, which has good dispersibility in the aqueous dispersion system and can maintain its morphology and dispersion stability in an environment of 200℃. Attached Figure Description

[0036] Figure 1 TEM images of the high-temperature stable microsphere matrix emulsion prepared in Example 1 before and after hot rolling at 200°C for 16 hours. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0038] Furthermore, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods; and unless otherwise specified, the reagents, materials and equipment are all commercially available.

[0039] Example 1

[0040] A method for preparing a high-temperature stable microsphere matrix emulsion includes the following steps:

[0041] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, and 0.2g emulsifier MS-1 to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat the mixture to 80℃ and stabilize it for 10min. Weigh 0.225g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system. After the addition is complete, maintain the reaction temperature at 80℃ for 2h. Allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere matrix emulsion, denoted as A1.

[0042] Example 2

[0043] A method for preparing a high-temperature stable microsphere matrix emulsion includes the following steps:

[0044] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, and 0.3g emulsifier MS-1 to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat the mixture to 80℃ and stabilize it for 10min. Weigh 0.225g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system. After the addition is complete, maintain the reaction temperature at 80℃ for 2h. Allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere matrix emulsion, denoted as A2.

[0045] Example 3

[0046] A method for preparing a high-temperature stable microsphere matrix includes the following steps:

[0047] Add 100g water, 30g styrene, 10g sodium styrene sulfonate, and 0.15g emulsifier MES to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat the mixture to 80℃ and stabilize it for 10min. Weigh 0.20g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system. After the addition is complete, maintain the reaction temperature at 80℃ for 2h. Allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere matrix emulsion, denoted as A3.

[0048] Example 4

[0049] A method for preparing a high-temperature stable microsphere derivative emulsion includes the following steps:

[0050] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, and 0.2g emulsifier MS-1 to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat to 80℃ and stabilize for 10min. Weigh 0.225g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system and react at 80℃ for 0.5h. Add the functional monomer solution containing the initiator (obtained by dissolving 3g methacryloyloxyethyltrimethylammonium chloride and 0.015g ammonium persulfate in 6.7mL of water) dropwise (2 drops / s) to the reaction system and continue the reaction at 80℃ for 4h. Allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere derivative emulsion, denoted as B1.

[0051] Example 5

[0052] A method for preparing a high-temperature stable microsphere derivative emulsion includes the following steps:

[0053] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, and 0.2g emulsifier MS-1 to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat to 80℃ and stabilize for 10min. Weigh 0.225g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system and react at 80℃ for 0.5h. Add a functional monomer solution containing the initiator (obtained by dissolving 3g acrylamide, 3g methacryloyloxyethyltrimethylammonium chloride, and 0.03g ammonium persulfate in 13.3mL of water) dropwise (2 drops / s) to the reaction system and continue the reaction for 4h. Allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere derivative emulsion, denoted as B2.

[0054] Comparative Example 1

[0055] A method for preparing a microsphere matrix emulsion is as described in Example 1, except that 3g of sodium styrene sulfonate is added, and the resulting microsphere matrix emulsion is denoted as D1.

[0056] Comparative Example 2

[0057] A method for preparing a microsphere matrix emulsion is as described in Example 1, except that 20g of styrene and 20g of sodium styrene sulfonate are added, and the resulting microsphere matrix emulsion is denoted as D2.

[0058] Comparative Example 3

[0059] A method for preparing a microsphere matrix emulsion is as described in Example 1, except that 0.05 g of emulsifier MS-1 is added, and the resulting microsphere matrix emulsion is denoted as D3.

[0060] Comparative Example 4

[0061] A method for preparing a microsphere matrix emulsion is as described in Example 1, except that sodium styrene sulfonate is not added, and the resulting microsphere matrix emulsion is denoted as D4.

[0062] Comparative Example 5

[0063] A method for preparing a microsphere matrix emulsion is as described in Example 1, except that 15g of sodium styrene sulfonate is replaced with 15g of 2-acrylamide-2-methylpropanesulfonic acid, and the resulting microsphere matrix emulsion is denoted as D5.

[0064] Comparative Example 6

[0065] A method for preparing a microsphere matrix emulsion is as described in Example 1, except that 15g of sodium styrene sulfonate is replaced with 10g of acrylic acid, and the resulting microsphere matrix emulsion is denoted as D6.

[0066] Comparative Example 7

[0067] A method for preparing a microsphere derivative emulsion is described in Example 5, except that sodium styrene sulfonate is not added, and the resulting microsphere derivative emulsion is designated as D7.

[0068] Comparative Example 8

[0069] A method for preparing a microsphere derivative emulsion includes the following steps:

[0070] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, 0.2g emulsifier MS-1, and a functional monomer solution (obtained by dissolving 3g acrylamide and 3g methacryloyloxyethyltrimethylammonium chloride in 13.3mL water) to a 400mL beaker. Shear emulsify the mixture at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat the mixture to 80℃ and stabilize for 10min. Weigh 0.255g ammonium persulfate and dissolve it in 2mL water. Add the resulting initiator solution dropwise (1 drop / s) to the system. React at 80℃ for 4.5h. Allow the mixture to cool naturally to room temperature. The resulting white emulsion is a microsphere derivative emulsion, denoted as D8.

[0071] Comparative Example 9

[0072] A method for preparing a microsphere derivative emulsion includes the following steps:

[0073] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, and 0.2g emulsifier MS-1 to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat to 80℃ and stabilize for 10min. Weigh 0.225g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system and react at 80℃ for 0.5h. Add the functional monomer solution (obtained by dissolving 10g acrylamide, 6g methacryloyloxyethyltrimethylammonium chloride, and 0.08g ammonium persulfate in 35mL of water) dropwise to the reaction system (1-3 drops / s). Continue the reaction for 4h and allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere derivative emulsion, denoted as D9.

[0074] Comparative Example 10

[0075] A method for preparing a high-temperature stable microsphere derivative emulsion includes the following steps:

[0076] Add 100g water, 30g styrene, 15g sodium styrene sulfonate, and 0.2g emulsifier MS-1 to a 400mL beaker. Shear emulsify the emulsion at a shear rate of 2000r / min for 20min using a shear emulsifier. Transfer the resulting emulsion to a three-necked flask, purge with nitrogen, and adjust the magnetic stirring speed to 1500r / min. Heat to 80℃ and stabilize for 10min. Weigh 0.225g ammonium persulfate and dissolve it in 2mL of water. Add the resulting initiator solution dropwise (1 drop / s) to the system and react at 80℃ for 0.5h. Add the functional monomer solution (obtained by dissolving 10g propanesulfonic acid and 0.05g ammonium persulfate in 25mL of water) dropwise (1-3 drops / s) to the reaction system and continue the reaction for 4h. Allow it to cool naturally to room temperature. The resulting white emulsion is the high-temperature stable microsphere derivative emulsion, denoted as D10.

[0077] Experimental Example 1

[0078] When transferring the microsphere emulsions obtained in the examples and comparative examples from the flasks to the sample vials, the precipitation at the bottom of the flasks was observed to analyze the dispersion and preparation of each sample. The results are shown in Table 1.

[0079] Table 1. Sample conditions obtained from the examples and comparative examples.

[0080]

[0081] As shown in Table 1, no solid precipitates appeared in the microsphere emulsions obtained in the embodiments of the present invention, indicating that the microsphere emulsions have good and relatively uniform dispersion. However, comparative examples D2, D3, D5, D8, and D9 showed partial precipitation after preparation. This indicates that higher sodium styrene sulfonate dosage, lower emulsifier dosage, type of comonomer, preparation method, and amount of functional monomer added all affect the dispersibility and uniformity of the high-temperature stable microspheres or their derivatives. If the above proportions are not within the scope of the present invention, it will be detrimental to the application of the product.

[0082] Experimental Example 2

[0083] At a stirring speed of 5000 r / min, 12 g of each of the emulsions obtained in the examples and comparative examples were added to 400 mL of water. After stirring for 20 min, the median particle size of each microsphere in the dispersion system was measured. Then, each microsphere dispersion system was placed in an aging tank, sealed, and hot-rolled at 200 °C for 16 h. After cooling to room temperature, the median particle size of the microspheres after hot rolling was measured, and the deformation rate was calculated. The results are shown in Table 2.

[0084]

[0085] Table 2. Microsphere particle size before and after hot rolling at 200℃ for 16 hours

[0086]

[0087]

[0088] As shown in Table 2, the deformation rates of the microspheres of different particle sizes and the derived microspheres obtained in the embodiments of the present invention are all less than 9.2%, which indicates that they can maintain long-term morphological stability in an aqueous dispersion system at 200°C. Furthermore, the type and ratio of comonomers, the amount of emulsifiers and functional monomers added have a significant impact on the deformation rate of the microsphere matrix or microsphere derivatives.

[0089] Experimental Example 3

[0090] 12g of each of the emulsions obtained in the examples and comparative examples were added to 400mL of water and stirred for 20min to ensure thorough dispersion. This emulsion was then used as a sealing fluid to seal the core. The artificial core was sealed using a core body device with a confining pressure of 5MPa, an upstream pressure of 5MPa, a downstream pressure of 0, a maximum displacement rate of 5mL / min, and constant pressure displacement for 16h. The permeability of the core before and after sealing was measured using gas chromatography, and the results are shown in Table 3.

[0091]

[0092] Table 3 Microsphere plugging capability test

[0093]

[0094]

[0095] As shown in Table 3, the microsphere matrix and its derivatives obtained in the embodiments of the present invention all exhibit good plugging performance, with the microsphere derivatives showing superior plugging performance compared to the microsphere matrix. This is attributed to the interaction between the surface charge and the core sample, which enhances their pressure-bearing plugging capacity. Both the microsphere matrix and its derivatives demonstrate higher plugging capabilities than inorganic plugging agents of the same particle size, resulting in excellent application effects.

[0096] Test Example 4

[0097] The preparation method of bentonite slurry is as follows: under high-speed stirring at 8000r / min, add 16g of bentonite and 1.2g of anhydrous sodium carbonate to 400g of water, stir for 2h, and then cure naturally at room temperature for 24h to obtain drilling fluid bentonite slurry.

[0098] The preparation method of DSP-1 drilling fluid is as follows: After stirring the bentonite slurry at 8000r / min for 20min, add 8g of DSP-1 and continue stirring for 20min to obtain DSP-1 drilling fluid.

[0099] The microsphere emulsions obtained in the examples and comparative examples were added to bentonite slurry and DSP-1 drilling fluid, respectively. The drilling fluids were hot-rolled at 200°C for 16 hours and then cooled to room temperature. The rheological and filtration properties of the drilling fluids were measured according to GB / T16783.1-2006. The results are shown in Table 4.

[0100] Table 4. Performance of microspheres after hot rolling in drilling fluid at 200℃ for 16 hours

[0101]

[0102]

[0103] As shown in Table 4, the microspheres A1-A3 of different particle sizes obtained in the embodiments of the present invention all have a certain effect on reducing filtration loss in drilling fluid. However, there is an optimal particle size microsphere that can significantly reduce the filtration loss of drilling fluid at 200℃. Microspheres B1 and B2 modified with functional monomers have a more significant filtration loss reduction ability, have less impact on rheological properties, and their performance is far superior to that of inorganic plugging materials.

[0104] In summary, the high-temperature stable microsphere matrix and its derivatives of this invention exhibit excellent high-temperature stability, maintaining morphological and functional stability at 200°C. During deep formation drilling, they can effectively and stably seal formation pores and reduce high-temperature drilling fluid loss, thus stabilizing the wellbore and meeting the needs of deep and ultra-deep drilling.

[0105] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0106] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0107] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a high-temperature stable microsphere derivative emulsion, comprising the following steps: (1) Preparation of high temperature stable microsphere matrix Comonomers and emulsifiers are added to water and shear emulsified. Under a nitrogen atmosphere, the resulting emulsion is heated to 60-85°C, and then initiator I is added. The reaction is carried out under a nitrogen atmosphere for 0.5-1 hour to obtain a reaction solution. The comonomers are styrene and sodium styrene sulfonate; the mass ratio of styrene to sodium styrene sulfonate in the comonomers is 1:0.25-0.75; based on 100 parts by mass of water, the comonomers comprise 20-50 parts, and the emulsifier comprises 0.1-1 parts; the initiator I comprises 0.2-0.8% of the mass of the comonomers. (2) Preparation of high temperature stable microsphere derivatives Add a functional monomer solution containing initiator II to the reaction solution of step (1), and continue the reaction for 1-4 hours under a nitrogen atmosphere at 60-85°C. The resulting white emulsion is the high-temperature stable microsphere derivative emulsion. The functional monomer is one or a combination of two or more of acrylamide, acrylic acid, dimethyl diallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and (3-acrylamidopropyl)trimethyl ammonium chloride. The mass of the functional monomer is 6-15% of the mass of the comonomer.

2. The method for preparing the high-temperature stable microsphere derivative emulsion according to claim 1, characterized in that, In step (1), the mass ratio of styrene to sodium styrene sulfonate in the comonomer is 1:0.3-0.

5.

3. The method for preparing the high-temperature stable microsphere derivative emulsion according to claim 1, characterized in that, The emulsifier in step (1) is sodium alkylphenol ether sulfosuccinate or disodium lauryl ether sulfosuccinate; the initiator I is ammonium persulfate and / or potassium persulfate.

4. The method for preparing the high-temperature stable microsphere derivative emulsion according to claim 1, characterized in that, The shear emulsification step in step (1) is as follows: shear emulsification is performed for 10-30 minutes at a shear rate of 2000-3000 r / min using a shear emulsifier; the initiator I is added to the system in the form of an aqueous solution of initiator I, and the concentration of the aqueous solution of initiator I is 0.1-0.2 g / mL; The reaction time is 1-4 hours; the stirring rate during the reaction is 1200-1800 r / min.

5. The method for preparing the high-temperature stable microsphere derivative emulsion according to claim 1, characterized in that, Initiator II in step (2) is ammonium persulfate and / or potassium persulfate; the mass of initiator II is 0.2-0.8% of the mass of the functional monomer; The functional monomer solution containing initiator II is obtained by adding the functional monomer and initiator II to water, and the concentration of the functional monomer in the functional monomer solution is 0.3-0.5 g / mL.

6. A high-temperature stable microsphere derivative emulsion, characterized in that, It was prepared using the preparation method described in claim 1.

7. The application of the high-temperature stable microsphere derivative emulsion of claim 6 in water-based drilling fluids for drilling fluid plugging.

8. A water-based drilling fluid, characterized in that, The water-based drilling fluid comprises the high-temperature stable microsphere derivative emulsion as described in claim 6; 20-50g of high-temperature stable microsphere derivative emulsion is added to each 1L of drilling fluid.

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