Water-based drilling fluid filtrate reducer, its preparation method and application

Abstract

The application belongs to the technical field of drilling, and particularly relates to a water-based drilling fluid fluid loss additive, a preparation method thereof and application. The water-based drilling fluid fluid loss additive comprises the following raw materials in parts by weight: acrylamide 5-25 parts, zwitterionic monomer 1-15 parts, 2-acrylamido-2-methylpropanesulfonic acid 5-25 parts, initiator 0.1-0.5 parts, and deionized water 60-200 parts. The disclosed fluid loss additive is safe and environmentally friendly, has excellent fluid loss reduction performance under high-temperature and high-salt conditions, and can meet the drilling requirements of high-mineralization and water-sensitive formations.

Description

Technical Field

[0001] This invention belongs to the field of drilling technology and relates to a water-based drilling fluid filtration reducer, specifically a water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect, its preparation method and application. Background Technology

[0002] Maintaining drilling fluid performance under the prevalent high-temperature and high-salinity conditions in deep formations has become an unavoidable technical challenge. Extreme downhole conditions often degrade the performance of various drilling fluid additives, especially filtration loss reducers. High temperatures lead to polymer degradation and chain breakage, while high salinity causes polymer coiling and poor water solubility, severely impacting drilling fluid performance. This not only directly affects the drilling fluid's ability to build borehole walls and suspend cuttings in complex environments but can also potentially lead to serious downhole accidents.

[0003] Synthetic polymers, with their adjustable molecular weight and functional group ratios, represent a mainstream research direction. However, conventional copolymers often struggle to simultaneously possess excellent temperature and salt resistance. This is because, under high temperature and high salinity conditions, conventional copolymers frequently experience polymer chain breakage, structural alterations, and degradation, leading to performance decline. Therefore, seeking new synthetic routes and material design strategies to achieve stability and controllability of polymers under extreme conditions is a crucial direction in current polymer materials research. Zwitterionic copolymers are widely used due to their good thermal stability and salt resistance. However, with increasing drilling depth, conventional zwitterionic copolymers are prone to degradation, affecting the performance of fluid loss reducers and failing to effectively meet the needs of field applications. The situation worsens when encountering highly mineralized formations. Therefore, developing temperature- and salt-resistant, stable, and reliable water-based drilling fluid loss reducers has become a key technological guarantee for effective and safe drilling in deep formations. Summary of the Invention

[0004] In view of this, and in view of the shortcomings of the prior art, especially the low temperature and salt resistance of existing filtration loss reducers, the present invention provides a water-based drilling fluid filtration loss reducer, which is a water-based drilling fluid filtration loss reducer that is resistant to high temperature and has anti-polyelectrolyte effect, and discloses the preparation method and application of the water-based drilling fluid filtration loss reducer.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first objective of this invention is to provide a water-based drilling fluid filtration reducer that is resistant to high temperatures and polyelectrolyte effects, comprising the following raw materials in parts by weight:

[0007] Acrylamide 5-25 parts, zwitterionic monomer 1-15 parts, 2-acrylamido-2-methylpropanesulfonic acid 5-25 parts, initiator 0.1-0.5 parts, deionized water 60-200 parts.

[0008] Preferably, the zwitterionic monomer is prepared according to the following method:

[0009] (1) Sodium bicarbonate and imidazole were added to an aqueous acetone solution and stirred for 10 min to obtain solution 1. 4-Chloromethylstyrene was slowly added dropwise to solution 1 at a rate of 1 s / drop to carry out the reaction. After vacuum filtration, ether extraction, water washing, hydrochloric acid back-extraction, neutralization with sodium hydroxide solution, ether extraction, and drying, a yellow oily substance was obtained.

[0010] (2) The yellow oily substance and 1,3-propanesulfonic acid lactone were dissolved in anhydrous acetonitrile and reacted. The white solid obtained during the reaction was filtered and dried to obtain a zwitterionic monomer.

[0011] Furthermore, in step (1), the mass ratio of sodium bicarbonate, imidazole, and 4-chloromethylstyrene is 10:20-30:15; the concentration of the acetone aqueous solution is 50%; the reaction temperature is 40-60℃, and the reaction time is 20-30h.

[0012] Preferably, in step (2), the mass ratio of the yellow oily substance, 1,3-propanesulfonic acid lactone, and anhydrous acetonitrile is 8:5:180; the reaction time is 12-36 h, the reaction temperature is 20-80 °C; and the drying is vacuum drying at 30-50 °C for 12-24 h.

[0013] According to the present invention, the preparation route of the zwitterionic monomer is as follows:

[0014]

[0015] Preferably, the initiator is azobisisobutyramidine hydrochloride, ammonium persulfate, potassium persulfate, or cerium ammonium nitrate.

[0016] The second objective of this invention is to provide a method for preparing a water-based drilling fluid filtration reducer as described above, which is resistant to high temperatures and has an anti-polyelectrolyte effect.

[0017] To achieve the above objectives, the present invention adopts the following technical solution:

[0018] A method for preparing a water-based drilling fluid filtration reducer that is resistant to high temperatures and polyelectrolytes includes the following steps:

[0019] Acrylamide, zwitterionic monomer and 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until fully dissolved. The pH was adjusted with sodium hydroxide solution. Then, nitrogen gas was blown into the solution to remove oxygen. An initiator was added and the temperature was raised to the reaction temperature to carry out the reaction. The solution was dried and pulverized to obtain the water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect.

[0020] Preferably, the concentration of the sodium hydroxide solution is 2 mol / L, and the reaction pH is 5-9.

[0021] Preferably, the nitrogen blowing time is 20-50 min; the reaction temperature is 45-65℃, the reaction time is 2-24 h; and the drying is carried out at 60-80℃ for 20-30 h.

[0022] According to the present invention, the structural formula of the water-based drilling fluid filtration reducer is as follows:

[0023]

[0024] The third technical objective of this invention is to provide an application of the high-temperature resistant and polyelectrolyte-resistant water-based drilling fluid filtration reducer described above in high-salinity and water-sensitive formations, with a concentration of 1-3 wt% in the drilling fluid.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. The water-based drilling fluid filtration reducer disclosed in this invention, which is resistant to high temperatures and has an anti-polyelectrolyte effect, is a polymer with an anti-polyelectrolyte effect, prepared by copolymerizing acrylamide, zwitterionic monomer, and 2-acrylamido-2-methylpropanesulfonic acid through free radical polymerization.

[0027] It should be noted that the water-based drilling fluid filtration reducer of the present invention, which exhibits high-temperature resistance and anti-polyelectrolyte effect, incorporates specific amounts and types of zwitterionic monomers. Currently, commercially available zwitterionic monomers, such as sulfobetaine methacrylate, are extensively studied, but are initially surrounded by a thick hydration shell composed of eight water molecules, severely hindering their salt-binding ability. Compared to sulfobetaine methacrylate, the zwitterionic monomer synthesized in this invention incorporates a phenylmethylene imidazole motif, which significantly enhances salt-binding ability and anti-polyelectrolyte effect, thereby strengthening hydration and improving temperature and salt resistance.

[0028] In addition, acrylamide has good water absorption and retention properties, which can help form a stable filter cake on the well wall during drilling, thereby effectively reducing filtration loss. The introduction of 2-acrylamido-2-methylpropanesulfonic acid not only enhances water solubility, but also significantly improves the salt resistance of the polymer. Since the sulfonic acid group has a negative charge, it can form an electrostatic shield with salt ions (such as Na+) to prevent salting out effect, thus ensuring the stable performance of the filtration loss reducer in high-salt environments.

[0029] 2. The components of the water-based drilling fluid filtration reducer disclosed in this invention work together in a specific ratio to achieve the excellent effect of this invention. That is, the filtration reducer of this invention has excellent rheological and filtration reduction properties under high temperature and high salinity conditions, which meets the drilling requirements of high salinity and water-sensitive formations. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 The image shows the infrared spectrum of the zwitterionic monomer.

[0032] Figure 2 The infrared spectrum of the water-based drilling fluid filtration reducer prepared in Example 2, which is resistant to high temperatures and polyelectrolyte effects. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0035] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0036] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0037] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0038] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0039] It should be noted that the zwitterionic monomers used in the examples were prepared according to Preparation Example 1.

[0040] Preparation Example 1

[0041] Preparation of zwitterionic monomers:

[0042] (1) 10g sodium bicarbonate and 27g imidazole were added to 100g acetone aqueous solution and stirred for 10min to obtain solution 1. 15g 4-chloromethylstyrene was slowly added dropwise to solution 1 and reacted at 50℃ for 24h. After vacuum filtration, ether extraction, water washing, 2mol / L hydrochloric acid back-extraction, 2mol / L sodium hydroxide solution neutralization, ether extraction, and drying, a yellow oily substance was obtained.

[0043] (2) Dissolve 8g of a yellow oily substance and 5g of 1,3-propanesulfonic acid lactone in 180g of anhydrous acetonitrile and react at 50℃ for 48h. The resulting white solid was filtered and dried under vacuum at 30℃ for 24h to obtain an amphoteric monomer.

[0044] Example 1

[0045] A water-based drilling fluid filtration reducer with high-temperature resistance and anti-polyelectrolyte effect comprises the following raw materials:

[0046] Acrylamide 15g, 2-acrylamido-2-methylpropanesulfonic acid 16g, zwitterionic monomer 2g, initiator 0.2g, deionized water 100g; wherein the initiator is azobisisobutyramidine hydrochloride.

[0047] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect includes the following steps:

[0048] Acrylamide, zwitterionic monomer and 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until fully dissolved. The pH was adjusted to 7 with sodium hydroxide solution. Nitrogen gas was then blown into the solution for 30 minutes to remove oxygen. An initiator was added, and the mixture was heated to 65°C and reacted for 6 hours. The mixture was then dried at 80°C for 24 hours and pulverized to obtain a white powder, which is the water-based drilling fluid filtration reducer A1 with high temperature resistance and anti-polyelectrolyte effect.

[0049] Example 2

[0050] A water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is described in Example 1, except that the zwitterionic monomer is 5g.

[0051] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is as described in Example 1, and the water-based drilling fluid filtration reducer A2 with high temperature resistance and anti-polyelectrolyte effect is obtained.

[0052] Example 3

[0053] A water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is described in Example 1, except that the zwitterionic monomer is 10g.

[0054] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is as described in Example 1, and the water-based drilling fluid filtration reducer A3 with high temperature resistance and anti-polyelectrolyte effect is obtained.

[0055] Example 4

[0056] A water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is described in Example 1, except that the zwitterionic monomer is 15g.

[0057] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is as described in Example 1, and the water-based drilling fluid filtration reducer A4 with high temperature resistance and anti-polyelectrolyte effect is obtained.

[0058] To further demonstrate the beneficial effects of the present invention and to better understand it, the technical features disclosed in the present invention are further illustrated by the following comparative examples, but these should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above description of the invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0059] Comparative Example 1

[0060] A water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is described in Example 1, except that the zwitterionic monomer is 0g.

[0061] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is as described in Example 1, and the water-based drilling fluid filtration reducer D1 with high temperature resistance and anti-polyelectrolyte effect is obtained.

[0062] Comparative Example 2

[0063] A water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is described in Example 1, except that the zwitterionic monomer is 25g.

[0064] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is as described in Example 1, and the water-based drilling fluid filtration reducer D2 with high temperature resistance and anti-polyelectrolyte effect is obtained.

[0065] Comparative Example 3

[0066] A water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is described in Example 1, except that the zwitterionic monomer is replaced with commercially available sulfobetaine methacrylate.

[0067] The preparation method of the above-mentioned water-based drilling fluid filtration reducer with high temperature resistance and anti-polyelectrolyte effect is as described in Example 1, and the water-based drilling fluid filtration reducer D3 with high temperature resistance and anti-polyelectrolyte effect is obtained.

[0068] 1) Figure 1 The image shows the infrared spectrum of the zwitterionic monomer.

[0069] 1632cm in the picture -1 The peak at 1579 cm⁻¹ is a characteristic peak of C=C. -1 1500cm -1 and 1459cm -1 The peak at 1558 cm⁻¹ is a characteristic peak of the benzene ring. -1 The peak at 1040 cm⁻¹ is characteristic of imidazole. -1 The location is the characteristic peak of S=O.

[0070] Infrared spectral data indicate that zwitterionic monomers were successfully synthesized.

[0071] 2) Figure 2 The infrared spectrum of the water-based drilling fluid filtration reducer prepared in Example 2, which is resistant to high temperatures and polyelectrolyte effects.

[0072] 3425cm in the picture -1 The peak at 1400 cm⁻¹ is a characteristic peak for the NH bond in acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. -1 The signal peaks at 1040 cm⁻¹ are for acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and -CH₂- and -CH₃- in zwitterionic monomers; -1 The signal peak at point S=O is shown.

[0073] Infrared spectral data indicate that the target product was successfully synthesized.

[0074] Application Experiment Example

[0075] 1. Drilling fluid F1: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 4g Al, and stir at 11000r / min for 30min.

[0076] 2. Drilling fluid F2: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g Al, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0077] 3. Drilling fluid F3: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g Al, stir at 11000r / min for 30min, then add 140g CaCl2, and stir at 11000r / min for 30min.

[0078] 4. Drilling fluid F4: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g Al, stir at 11000r / min for 30min, then add 200g HCOONa, and stir at 11000r / min for 30min.

[0079] 5. Drilling fluid F5: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g A2, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0080] 6. Drilling fluid F6: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g A3, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0081] 7. Drilling fluid F7: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g A4, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0082] 8. Drilling fluid DF1: Add 16g bentonite and 1.2g sodium carbonate to 400g water and stir at 11000r / min for 20min.

[0083] 9. Drilling fluid DF2: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 144g NaCl and stir at 11000r / min for 30min.

[0084] 10. Drilling fluid DF3: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 140g CaCl2 and stir at 11000r / min for 30min.

[0085] 11. Drilling fluid DF4: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 200g HCOONa, and stir at 11000r / min for 30min.

[0086] 12. Drilling fluid DF5: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g D1, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0087] 13. Drilling fluid DF6: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g D2, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0088] 14. Drilling fluid DF7: Add 16g bentonite and 1.2g sodium carbonate to 400g water, stir at 11000r / min for 20min, then add 8g D3, stir at 11000r / min for 30min, then add 144g NaCl, and stir at 11000r / min for 30min.

[0089] 15. Drilling fluid DF8: Add 16g of bentonite and 1.2g of sodium carbonate to 400g of water, stir at 11000r / min for 20min, then add 8g of high temperature and salt resistance filtration reduction agent Driscal-D, stir at 11000r / min for 30min, then add 144g of NaCl, and stir at 11000r / min for 30min.

[0090] Test Example 1

[0091] 400 mL of drilling fluids F1-F4, DF1-DF4, and DF8 were stirred at 11000 r / min for 30 min, and then hot-rolled at 200℃ for 16 h. After aging, the mixture was cooled to room temperature and stirred at 11000 r / min for 30 min. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), shear force (YP, Pa), and API filtration loss (FL) of the above drilling fluids were determined according to the petroleum and natural gas industry standard GB / T 29170-2012 "Petroleum and Natural Gas Industry - Laboratory Testing of Drilling Fluids". API High temperature and high pressure filtration loss FL HTHP (180℃, 3.5MPa), the results are shown in Table 1.

[0092] Table 1 Drilling Fluid Performance Tests

[0093]

[0094]

[0095] Experimental results show that adding 1% of the filtration loss reducer of this invention can reduce the API filtration loss of freshwater-based drilling fluid from 30.0 mL to 7 mL, and the high-temperature and high-pressure filtration loss from 120 mL to 23.5 mL. This is because the high-temperature and high-salt environment disrupts the colloidal stability of the drilling fluid, leading to a significant increase in filtration loss. The API filtration loss and high-temperature and high-pressure filtration loss of DF2, DF3, and DF4 after high-temperature aging are total filtration losses. The filtration losses of drilling fluids F2, F3, and F4 after high-temperature aging with the filtration loss reducer of this invention are 4.0 mL, 4.3 mL, and 2.3 mL, respectively, and the high-temperature and high-pressure filtration losses are 20 mL, 25 mL, and 18 mL, respectively. Under saturated salt conditions, the API filtration loss of drilling fluid with 2% Driscal-D after high-temperature aging is 21.5 mL, and the high-temperature and high-pressure filtration loss is 89.0 mL. The drilling fluid with the filtration loss reducer of this invention exhibited an API filtration loss of 4.5 mL under the same conditions and a high-temperature, high-pressure filtration loss of 25.5 mL, representing reductions of 79% and 71% respectively compared to Driscal-D. This demonstrates that the zwitterionic filtration loss reducer of this invention possesses excellent temperature and salt resistance, reaching salt saturation resistance, exhibiting 35% resistance to CaCl2, and 50% resistance to HCOONa.

[0096] Test Example 2

[0097] 400 mL of drilling fluids F2, F5-F7, and DF5-DF7 were stirred at 11000 r / min for 30 min, and then hot-rolled at 200℃ for 16 h. After aging, the mixture was cooled to room temperature and stirred at 11000 r / min for 30 min. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), shear force (YP, Pa), and API filtration loss (FL) of the above drilling fluids were determined according to the petroleum and natural gas industry standard GB / T29170-2012 "Petroleum and Natural Gas Industry - Laboratory Testing of Drilling Fluids". API High temperature and high pressure filtration loss FL HTHP (180℃, 3.5MPa), the results are shown in Table 2.

[0098] Table 2 Drilling Fluid Performance Tests

[0099] Drilling fluid AV / mPa·s PV / mPa·s YP / Pa <![CDATA[FL API / mL]]> <![CDATA[FL HTHP / mL]]> F2 21.0 17.0 4.0 4.5 25.5 F5 12.5 12 0.5 4 20 F6 9 9 0 6.1 31.5 F7 8 8 0 9.6 45 DF5 5 5 0 19.5 85 DF6 6 3 0 18.5 75 DF7 11.5 10.5 1 17.5 68

[0100] The test results in Table 2 show that appropriately increasing the proportion of zwitterionic monomers in the polymer can further reduce filtration loss. This is because the phenylmethylene imidazole motif significantly enhances salt-binding ability and anti-polyelectrolyte effect, thereby enhancing hydration and improving salt resistance. Furthermore, the phenylmethylene imidazole motif has a significant steric hindrance effect, which can improve the polymer's temperature resistance. The results from DF5 show that the filtration loss reduction and rheological properties of the polymer without added zwitterionic monomers decrease. The results from DF6 show that the polymer's filtration loss reduction performance decreases. This is because when the proportion of zwitterionic monomers further increases, the excessive amount of phenylmethylene imidazole motifs hinders polymerization between monomers due to their steric hindrance effect. Therefore, the proportion of zwitterionic monomers in the polymer needs to be controlled within the range of this invention. At this range, the polymerization effect of zwitterionic monomers with other monomers is good, resulting in excellent filtration loss reduction performance. Although commercially available sulfobetaine methacrylate is also a zwitterionic monomer, its temperature resistance is poor and its binding ability with salt ions is weak, therefore its performance is inferior to that of this invention.

[0101] In summary, the zwitterionic filtration reducer of the present invention has a temperature resistance of up to 200℃, a NaCl resistance of 36%, a CaCl2 resistance of 35%, and a HCOONa resistance of 50%. It exhibits excellent rheological and filtration reduction properties under high temperature and high salinity conditions, meeting the drilling requirements of highly mineralized and water-sensitive formations.

[0102] The preferred embodiments of the present invention have been described in detail in the description of the filtration loss reducing agent of the present invention. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A water-based drilling fluid filtration reducer with resistance to high temperature and polyelectrolyte effects, characterized in that, The raw materials include the following parts by weight: 5-25 parts acrylamide, 1-15 parts zwitterionic monomer, 5-25 parts 2-acrylamido-2-methylpropanesulfonic acid, 0.1-0.5 parts initiator, and 60-200 parts deionized water; Acrylamide, zwitterionic monomer and 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until fully dissolved. The pH was adjusted with sodium hydroxide solution. Then, nitrogen gas was blown into the solution to remove oxygen. An initiator was added and the temperature was raised to the reaction temperature to carry out the reaction. The solution was dried and pulverized to obtain the water-based drilling fluid filtration reducer with high temperature resistance and polyelectrolyte resistance. The zwitterionic monomer was prepared according to the following method: (1) Sodium bicarbonate and imidazole were added to an aqueous acetone solution and stirred to obtain solution 1. 4-chloromethylstyrene was added dropwise to solution 1 to carry out the reaction. After vacuum filtration, ether extraction, water washing, hydrochloric acid back-extraction, neutralization with sodium hydroxide solution, ether extraction, and drying, a yellow oily substance was obtained. (2) The yellow oily substance and 1,3-propanesulfonic acid lactone were dissolved in anhydrous acetonitrile and reacted; the white solid obtained during the reaction was filtered and dried to obtain the zwitterionic monomer.

2. The water-based drilling fluid filtration reducer with high-temperature resistance and polyelectrolyte resistance according to claim 1, characterized in that, The mass ratio of sodium bicarbonate, imidazole and 4-chloromethylstyrene in step (1) is 10:20-30:15; The concentration of the acetone aqueous solution is 50%; the reaction temperature is 40-60℃, and the reaction time is 20-30h.

3. The water-based drilling fluid filtration reducer with high-temperature resistance and polyelectrolyte resistance according to claim 1, characterized in that, The mass ratio of the yellow oily substance, 1,3-propanesulfonic acid lactone and anhydrous acetonitrile in step (2) is 8:5:180; the reaction time is 12-36 h and the reaction temperature is 20-80 °C; the drying is vacuum drying at 30-50 °C for 12-24 h.

4. The water-based drilling fluid filtration reducer with high-temperature resistance and polyelectrolyte resistance according to claim 1, characterized in that, The initiator is azobisisobutyramidine hydrochloride, ammonium persulfate, potassium persulfate, or cerium ammonium nitrate.

5. A method for preparing a water-based drilling fluid filtration reducer with high-temperature resistance and polyelectrolyte resistance as described in claim 1, characterized in that, The process includes the following steps: adding acrylamide, zwitterionic monomer and 2-acrylamido-2-methylpropanesulfonic acid to deionized water, stirring until fully dissolved, and adjusting the pH with sodium hydroxide solution; then blowing nitrogen gas into the solution to remove oxygen, adding an initiator, heating to the reaction temperature to carry out the reaction, drying and pulverizing to obtain the water-based drilling fluid filtration reducer with high temperature resistance and polyelectrolyte resistance.

6. The preparation method of the water-based drilling fluid filtration reducer with high-temperature resistance and polyelectrolyte resistance according to claim 5, characterized in that, The concentration of the sodium hydroxide solution is 2 mol / L, and the pH value of the reaction is 5-9.

7. The preparation method of the water-based drilling fluid filtration reducer with high-temperature resistance and polyelectrolyte resistance according to claim 5, characterized in that, The nitrogen blowing time is 20-50 min; the reaction temperature is 45-65℃ and the reaction time is 2-24 h; the drying is carried out at 60-80℃ for 20-30 h.

8. The application of the water-based drilling fluid filtration reducer with high temperature resistance and polyelectrolyte resistance as described in claim 1 in high-salinity and water-sensitive formations.

9. The application according to claim 8, characterized in that, The concentration of the water-based drilling fluid filtration reducer with anti-high temperature and anti-polyelectrolyte effect in the drilling fluid is 1-3 wt%.

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