High-temperature-resistant filtrate reducer, preparation method thereof and drilling fluid

Abstract

The invention provides a high-temperature-resistant filtrate reducer which is a grafted copolymer comprising lignin sulfonate and acrylamide monomers, and the lignin sulfonate is crown ether modified lignin subjected to sulfonation treatment. The invention also provides a preparation method and application of the high-temperature-resistant filtrate reducer. According to the high-temperature-resistant filtrate reducer provided by the invention, the lignin sulfonate is crown ether modified lignin subjected to sulfonation treatment, crown ether is introduced into the lignin, the divalent salt resistance and temperature resistance of the filtrate reducer are greatly improved, and the filtrate reducer can resist 8.0 wt% of CaCl2 and can resist the temperature of 240 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of drilling technology, specifically relating to a high-temperature filtration loss reducing agent, its preparation method, and drilling fluid. Background Technology

[0002] As my country's conventional oil and gas resources dwindle, particularly the near depletion of shallow and medium-depth resources, the focus has shifted to unconventional resources such as heavy oil, oil sands, and shale oil and gas. While my country's deep oil and gas resources are widely distributed, their distribution is extremely uneven, and they are generally buried at considerable depths. The Tarim Basin, Sichuan Basin, and Bohai Bay Basin, in particular, possess relatively abundant deep oil and gas resources, with depths generally exceeding 5000 meters. In the Tarim Basin, the deepest strata even exceed 9000 meters, with temperatures generally exceeding 180°C and some reaching over 250°C. Drilling in these areas presents the primary challenges of extremely high temperature and pressure, as well as complex geological conditions. Drilling may encounter complex formations such as mudstone and shale formations, fractured formations, and large sections of salt-gypsum layers. Excessive drilling fluid loss during drilling in these formations can lead to wellbore collapse, stuck pipe, lost circulation, and well kicks, potentially even resulting in blowouts. Therefore, selecting high-performance filtration loss reducers is particularly important during deep drilling.

[0003] Most commonly used high-temperature and salt-resistant drilling fluid filtration reducers are temperature-resistant copolymers. They mainly achieve temperature and salt resistance by introducing different functional monomers, such as using CC chains as the main chain and using rigid groups or temperature- and salt-resistant side groups as the side chains.

[0004] Clapper et al. (US7651980B2) synthesized a high-temperature filtration loss reducer using monomers such as AM, AMPS, and N-NVP, which is resistant to 260℃ and 10.0 wt% NaCl. Chang Xiaofeng et al. (Drilling Fluids and Completion Fluids, 2019, 36(4):420-426) developed a 4-VP / N, N-DMAA / AMPS / N-NVCL quaternary copolymer filtration loss reducer, which is resistant to 260℃, saturates with NaCl, and is resistant to 2.0 wt% CaCl2.

[0005] Lignin is a cross-linked phenolic natural polymer. In the plant kingdom, its content is second only to cellulose. It is widely distributed in higher plants with tubular structures, such as ferns and above. It has a wide range of uses, mainly as a binder, corrosion inhibitor, cement slurry water-reducing agent, drilling fluid diluent, etc. In terms of lignin filtration loss reducers, Wang Zhonghua (Advances in Fine Petrochemicals, 2005, 11(6):1-3) synthesized an AM / AMPS / lignin sulfonate graft copolymer filtration loss reducer, which has a temperature resistance of up to 180℃, NaCl saturation resistance, and 2.0% CaCl2 resistance. Wang Zijun et al. (Synthesis and performance testing of lignin filtration loss reducers and flocculants, Master's thesis of Tianjin University, 2009) first sulfonated lignin and then synthesized a filtration loss reducer with sulfomethylphenol resin, which has a temperature resistance of up to 120℃, 4.0wt% NaCl resistance, and 2.5wt% CaCl2 resistance. Wang Pingquan et al. (Journal of Chongqing University of Science and Technology (Natural Science Edition), 2012, 14(2): 108-111) synthesized an AM / AOPS / lignin sulfonate graft copolymer filtration loss reducer, which has a temperature resistance of up to 180℃ and a NaCl saturation resistance. Wu Di et al. (CN106279709A) synthesized a filtration loss reducer using amylose and sulfonated alkali lignin, which has a temperature resistance of 220℃ and a resistance to 4.28wt% CaCl2. Wei Hua et al. (CN112210574A) obtained enzymatically hydrolyzed lignin through secondary enzymatic hydrolysis, and then prepared a lignin-phenolic resin filtration loss reducer by sulfonation reaction with benzoyl peroxide, formaldehyde, sulfonating agent, etc., which has a temperature resistance of 180℃, a BOD / CODCr of 4.52-49.88, and good biodegradability.

[0006] In summary, the filtrate loss reducers prepared from the lignin used above are mainly obtained by combining with phenolic resin. Moreover, since resistance to high-valence ions can only be achieved through sulfonation groups, their calcium resistance is limited. Therefore, there is an urgent need to develop a filtrate loss reducer with high biodegradability and strong calcium resistance. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of commonly used high-temperature filtration loss reducing agents in terms of weak resistance to divalent salts. This invention proposes a high-temperature filtration loss reducing agent, its preparation method, and drilling fluid. This high-temperature filtration loss reducing agent can improve the drilling fluid's resistance to divalent salts and its auxiliary temperature resistance.

[0008] Therefore, in a first aspect, the present invention provides a high-temperature filtration loss reducing agent, wherein the high-temperature filtration loss reducing agent is a graft copolymer comprising sulfonated lignin and acrylamide monomers, wherein the sulfonated lignin is crown ether modified lignin after sulfonation treatment.

[0009] The high-temperature filtration loss reducer provided by this invention uses sulfonated lignin, which is crown ether modified lignin after sulfonation treatment. The crown ether is introduced into the lignin, which has stronger resistance to divalent salts and high temperatures, and can improve the drilling fluid's resistance to divalent salts and auxiliary temperature resistance.

[0010] As a specific embodiment of the present invention, the raw materials for the crown ether modified lignin, by weight, include:

[0011] Crown ether 150-300 parts,

[0012] Inorganic base 30-60 parts,

[0013] Formaldehyde 200-500 parts

[0014] Lignin 1000-2000 parts,

[0015] The first solvent is 4500-5500 parts.

[0016] In this invention, the components in the raw materials of crown ether modified lignin are limited to the above-mentioned range. In particular, the combination of formaldehyde, crown ether and inorganic alkali enhances the binding degree of lignin with crown ether, as well as the binding degree of the high-temperature filtration loss reducing agent with water.

[0017] In a specific embodiment of the present invention, the crown ether is preferably an aza crown ether. In the present invention, the aza crown ether induces high-valence metal ions to enter the hole for complexation, and cooperates with formaldehyde and inorganic bases to improve the ability of the high-temperature filtration loss reducer to resist divalent salts.

[0018] In a specific embodiment of the present invention, the azacrown ether is selected from at least one of aza-14-crown-4, diaza-14-crown-4, aza-15-crown-5, diaza-15-crown-5, aza-18-crown-6, and diaza-18-crown-6. In the present invention, the azacrown ether is preferably one of the above-mentioned azacrown ethers, which can match the size of high-valence metal ions, thereby promoting complexation between the two.

[0019] As a specific embodiment of the present invention, the lignin is selected from at least one of S-lignin, G-lignin and H-lignin.

[0020] As a specific embodiment of the present invention, the inorganic base is selected from at least one of NaOH and KOH.

[0021] As a specific embodiment of the present invention, the first solvent is selected from at least one of water and ethanol.

[0022] In a specific embodiment of the present invention, the lignin is derived from the black liquor of alkali-processed wheat straw pulp.

[0023] As a specific embodiment of the present invention, the method for preparing lignin includes: precipitating wheat straw pulp black liquor with 70-98 wt% sulfuric acid, removing the precipitate, washing it with a second solvent until neutral, and then drying and pulverizing the washed precipitate.

[0024] In a specific embodiment of the present invention, the second solvent is selected from at least one of water and ethanol.

[0025] As a specific embodiment of the present invention, the drying conditions include: temperature 50-120°C and time 8-15 hours.

[0026] As a specific embodiment of the present invention, the mass concentration of the sulfuric acid is 80-98 wt%, preferably 90-98 wt%.

[0027] As a specific embodiment of the present invention, the preparation method of the crown ether modified lignin includes:

[0028] S1. Add the crown ether and the inorganic base to the first solvent to carry out the first reaction;

[0029] S2. Add formaldehyde and lignin to carry out the second reaction;

[0030] S3. Remove the remaining formaldehyde from the reaction product obtained from the second reaction.

[0031] As a specific embodiment of the present invention, the mass ratio of the crown ether, formaldehyde and lignin is 3:4-6:20-25.

[0032] As a specific embodiment of the present invention, the conditions for the first reaction include: a stirring speed of 100-300 rpm, a temperature of 10-40°C, and a time of 30-50 min.

[0033] As a specific embodiment of the present invention, the conditions for the second reaction include: a stirring speed of 1500-2500 rpm, a temperature of 50-100°C, and a time of 3-5 h.

[0034] As a specific embodiment of the present invention, the raw materials for sulfonation treatment, by weight, include: crown ether modified lignin, sulfonating agent and sulfonation catalyst.

[0035] As a specific embodiment of the present invention, the mass ratio of the sulfonating agent, the sulfonating catalyst and the lignin (the raw material for preparing crown ether modified lignin) is 50-160:1:62-200.

[0036] As a specific embodiment of the present invention, the sulfonating agent is selected from at least one of sodium sulfite, chlorosulfonic acid, and sulfur trioxide.

[0037] As a specific embodiment of the present invention, the sulfonation catalyst is selected from at least one of chloride and ferric bromide.

[0038] As a specific embodiment of the present invention, the sulfonation treatment includes: adding a sulfonating agent and a sulfonation catalyst to the crown ether modified lignin to carry out a sulfonation reaction.

[0039] As a specific embodiment of the present invention, the conditions for the sulfonation reaction include: a stirring speed of 800-1200 rpm, a temperature of 80-100°C, a time of 5-8 h, and a system pH of 10 or higher, preferably 10-13.

[0040] As a specific embodiment of the present invention, the raw materials of the graft copolymer, by weight, include: sulfonated lignin, acrylamide monomers and initiators.

[0041] As a specific embodiment of the present invention, the mass ratio of the acrylamide monomer, the initiator and the lignin (the raw material for preparing crown ether modified lignin) is 30-100:1:20-67.

[0042] As a specific embodiment of the present invention, the acrylamide monomer includes acrylamide and 2-acrylamide-2-methylpropanesulfonic acid.

[0043] In a specific embodiment of the present invention, the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2 to 8:1. The preferred mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is the above-mentioned ratio, which ensures that the polymer chain is sufficiently long while also providing sufficient temperature resistance and water solubility.

[0044] In a specific embodiment of the present invention, the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 3 to 4:1. The preferred mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is the above-mentioned ratio, which can further increase the chain length of the polymer while also ensuring sufficient temperature resistance and water solubility.

[0045] As a specific embodiment of the present invention, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, sodium bisulfite, benzoyl peroxide, and azobisisobutyronitrile.

[0046] Therefore, in a second aspect, the present invention provides a method for preparing a high-temperature resistant filtration loss reducer, comprising the following steps:

[0047] S10. Inert gas is introduced into the sulfonated lignin to remove oxygen;

[0048] S20, add acrylamide monomers and initiators to carry out graft polymerization reaction;

[0049] S30. The mixture obtained from the graft polymerization reaction is washed, dried, and pulverized with a third solvent.

[0050] In a specific embodiment of the present invention, the inert gas is nitrogen.

[0051] In a specific embodiment of the present invention, the inert gas is introduced for 20 to 40 minutes.

[0052] As a specific embodiment of the present invention, the conditions for the graft polymerization reaction include: stirring at 1800-2200 rpm, at 80-100°C, and for 2-4 hours under an inert gas atmosphere.

[0053] As a specific embodiment of the present invention, the third solvent is selected from at least one of water and ethanol.

[0054] Therefore, in a third aspect, the present invention provides a drilling fluid comprising the above-mentioned high-temperature filtration reducing agent or the high-temperature filtration reducing agent prepared by the above-mentioned preparation method.

[0055] As a specific embodiment of the present invention, the amount of the high-temperature filtration loss reducing agent added to the drilling fluid is 1-5 wt%.

[0056] The present invention has the following beneficial effects:

[0057] The high-temperature filtration loss reducer provided by this invention uses sulfonated lignin, which is crown ether modified lignin after sulfonation treatment. The crown ether is introduced into the lignin, which greatly improves the filtration loss reducer's resistance to divalent salts and temperature resistance. It is resistant to 8.0 wt% CaCl2 and can withstand temperatures up to 240℃. Detailed Implementation

[0058] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0059] Example 1

[0060] 1) Weigh 150g of aza-14-crown-4 and 30g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 30min.

[0061] 2) Add 200g of formaldehyde and 1000g of lignin to the reactor in sequence, raise the temperature to 50℃, increase the stirring speed to 2000rpm, and continue the reaction for 3h.

[0062] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0063] 4) Add 800g sodium sulfite and 10g ferric chloride to the above reactor, adjust the temperature to 80℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 10.0 with NaOH, and carry out the sulfonation reaction for 5.5h.

[0064] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0065] 6) Add 1200g AM (acrylamide) and 300g AMPS (2-acrylamide-2-methylpropanesulfonic acid) sequentially to the above reactor, adjust the stirring speed to 500rpm, and after it is fully dissolved, add 30g ammonium persulfate, increase the stirring speed to 2000rpm, keep the temperature at 80℃, and carry out the graft polymerization reaction for 2h.

[0066] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0067] Example 2

[0068] 1) Weigh 150g of diaza-14-crown-4 and 30g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 30min.

[0069] 2) Add 200g of formaldehyde and 1000g of lignin to the reactor in sequence, raise the temperature to 50℃, increase the stirring speed to 2000rpm, and continue the reaction for 3h.

[0070] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0071] 4) Add 800g sodium sulfite and 10g ferric chloride to the above reactor, adjust the temperature to 80℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 10.0 with NaOH, and carry out the sulfonation reaction for 5.5h.

[0072] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0073] 6) Add 1200g AM and 300g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 30g potassium persulfate, increase the stirring speed to 2000rpm, keep the temperature at 80℃, and carry out the graft polymerization reaction for 2h.

[0074] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0075] Example 3

[0076] 1) Weigh 150g of aziro-15-crown-5 and 30g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 30min.

[0077] 2) Add 200g of formaldehyde and 1000g of lignin to the reactor in sequence, raise the temperature to 50℃, increase the stirring speed to 2000rpm, and continue the reaction for 3h.

[0078] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0079] 4) Add 800g sodium sulfite and 10g ferric chloride to the above reactor, adjust the temperature to 80℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 10.0 with NaOH, and carry out the sulfonation reaction for 5.5h.

[0080] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0081] 6) Add 1200g AM and 300g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after they are fully dissolved, add 30g sodium bisulfite, increase the stirring speed to 2000rpm, keep the temperature at 80℃, and carry out the graft polymerization reaction for 2h.

[0082] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0083] Example 4

[0084] 1) Weigh 180g of diaza-15-crown-5 and 40g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 35min.

[0085] 2) Add 300g of formaldehyde and 1300g of lignin to the reactor in sequence, raise the temperature to 65℃, increase the stirring speed to 2000rpm, and continue the reaction for 3.5h.

[0086] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0087] 4) Add 1000g sodium sulfite and 12g ferric chloride to the above reactor, adjust the temperature to 90℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 10.5 with NaOH, and carry out the sulfonation reaction for 6h.

[0088] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0089] 6) Add 1600g AM and 400g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 40g benzoyl peroxide, increase the stirring speed to 2000rpm, keep the temperature at 90℃, and carry out the graft polymerization reaction for 3h.

[0090] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0091] Example 5

[0092] 1) Weigh 180g of aziro-18-crown-6 and 40g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 35min.

[0093] 2) Add 300g of formaldehyde and 1300g of lignin to the reactor in sequence, raise the temperature to 65℃, increase the stirring speed to 2000rpm, and continue the reaction for 3.5h.

[0094] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0095] 4) Add 1000g sodium sulfite and 12g ferric chloride to the above reactor, adjust the temperature to 90℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 10.5 with NaOH, and carry out the sulfonation reaction for 6h.

[0096] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0097] 6) Add 1600g AM and 400g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after they are fully dissolved, add 40g azobisisobutyronitrile, increase the stirring speed to 2000rpm, keep the temperature at 90℃, and carry out the graft polymerization reaction for 3h.

[0098] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0099] Example 6

[0100] 1) Weigh 180g of diaza-18-crown-6 and 40g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 35min.

[0101] 2) Add 300g of formaldehyde and 1300g of lignin to the reactor in sequence, raise the temperature to 65℃, increase the stirring speed to 2000rpm, and continue the reaction for 3.5h.

[0102] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0103] 4) Add 1000g sodium sulfite and 12g ferric chloride to the above reactor, adjust the temperature to 90℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 10.5 with NaOH, and carry out the sulfonation reaction for 6h.

[0104] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0105] 6) Add 1600g AM and 400g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 40g ammonium persulfate, increase the stirring speed to 2000rpm, keep the temperature at 90℃, and carry out the graft polymerization reaction for 3h.

[0106] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0107] Example 7

[0108] 1) Weigh 200g of aza-14-crown-4 and 50g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 40min.

[0109] 2) Add 400g of formaldehyde and 1500g of lignin to the reactor in sequence, raise the temperature to 80℃, increase the stirring speed to 2000rpm, and continue the reaction for 4h.

[0110] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0111] 4) Add 1200g sodium sulfite and 14g ferric chloride to the above reactor, adjust the temperature to 90℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 11.0 with NaOH, and carry out the sulfonation reaction for 7h.

[0112] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0113] 6) Add 1800g AM and 500g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after it is fully dissolved, add 40g potassium persulfate, increase the stirring speed to 2000rpm, keep the temperature at 90℃, and carry out the graft polymerization reaction for 3h.

[0114] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0115] Example 8

[0116] 1) Weigh 200g of diaza-14-crown-4 and 50g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 40min.

[0117] 2) Add 400g of formaldehyde and 1500g of lignin to the reactor in sequence, raise the temperature to 80℃, increase the stirring speed to 2000rpm, and continue the reaction for 4h.

[0118] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0119] 4) Add 1200g sodium sulfite and 14g ferric chloride to the above reactor, adjust the temperature to 90℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 11.0 with NaOH, and carry out the sulfonation reaction for 7h.

[0120] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0121] 6) Add 1800g AM and 500g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 40g sodium bisulfite, increase the stirring speed to 2000rpm, keep the temperature at 90℃, and carry out the graft polymerization reaction for 3h.

[0122] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0123] Example 9

[0124] 1) Weigh 200g of azira-15-crown-5 and 50g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 40min.

[0125] 2) Add 400g of formaldehyde and 1500g of lignin to the reactor in sequence, raise the temperature to 80℃, increase the stirring speed to 2000rpm, and continue the reaction for 4h.

[0126] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0127] 4) Add 1200g sodium sulfite and 14g ferric chloride to the above reactor, adjust the temperature to 90℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 11.0 with NaOH, and carry out the sulfonation reaction for 7h.

[0128] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0129] 6) Add 1800g AM and 500g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 40g benzoyl peroxide, increase the stirring speed to 2000rpm, keep the temperature at 90℃, and carry out the graft polymerization reaction for 3h.

[0130] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0131] Example 10

[0132] 1) Weigh 300g of diaza-15-crown-5 and 60g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 50min.

[0133] 2) Add 500g of formaldehyde and 2000g of lignin to the reactor in sequence, raise the temperature to 100℃, increase the stirring speed to 2000rpm, and continue the reaction for 5h.

[0134] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0135] 4) Add 1600g sodium sulfite and 16g ferric chloride to the above reactor, adjust the temperature to 100℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 11.5 with NaOH, and carry out the sulfonation reaction for 8h.

[0136] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0137] 6) Add 2400g AM and 600g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after they are fully dissolved, add 50g azobisisobutyronitrile, increase the stirring speed to 2000rpm, keep the temperature at 80-100℃, and carry out the graft polymerization reaction for 4h.

[0138] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0139] Example 11

[0140] 1) Weigh 300g of aziro-18-crown-6 and 60g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 50min.

[0141] 2) Add 500g of formaldehyde and 2000g of lignin to the reactor in sequence, raise the temperature to 100℃, increase the stirring speed to 2000rpm, and continue the reaction for 5h.

[0142] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0143] 4) Add 1600g sodium sulfite and 16g ferric chloride to the above reactor, adjust the temperature to 100℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 11.5 with NaOH, and carry out the sulfonation reaction for 8h.

[0144] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0145] 6) Add 2400g AM and 600g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 50g ammonium persulfate, increase the stirring speed to 2000rpm, maintain the temperature at 80-100℃, and carry out the graft polymerization reaction for 4h.

[0146] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0147] Example 12

[0148] 1) Weigh 300g of diaza-18-crown-6 and 60g of NaOH and add them to a 10L reactor. Slowly add 5000g of deionized water. After complete dissolution, set the stirring speed to 200rpm and continue the reaction for 50min.

[0149] 2) Add 500g of formaldehyde and 2000g of lignin to the reactor in sequence, raise the temperature to 100℃, increase the stirring speed to 2000rpm, and continue the reaction for 5h.

[0150] 3) Stop stirring and wait for the system temperature to drop to room temperature. Then transfer the reaction product to a low-temperature rotary evaporator to remove the remaining formaldehyde. Then return the product to the reactor mentioned above.

[0151] 4) Add 1600g sodium sulfite and 16g ferric chloride to the above reactor, adjust the temperature to 100℃, increase the stirring speed to 1000rpm, adjust the pH of the system to 11.5 with NaOH, and carry out the sulfonation reaction for 8h.

[0152] 5) Purge the reactor with nitrogen gas to remove oxygen for 30 minutes;

[0153] 6) Add 2400g AM and 600g AMPS to the reactor in sequence, adjust the stirring speed to 500rpm, and after fully dissolving, add 50g potassium persulfate, increase the stirring speed to 2000rpm, maintain the temperature at 80-100℃, and carry out the graft polymerization reaction for 4h.

[0154] 7) After the reaction is complete, place the gel-like product in a vacuum filtration device and rinse it with deionized water several times until the filtrate no longer contains the reactants. Place the product in an oven at 100°C to dry it, and then pulverize it through a 200-mesh sieve to obtain the powder, which is the sulfonated crown ether-lignin graft copolymer.

[0155] Based on the results of liquid phase permeation chromatography, the average molecular weights of Examples 1 to 12 were all in the range of 10 to 25 × 10⁻⁶. 4 Between, respectively 12.3×10 4 15.6×10 4 13.8×10 4 16.7×10 4 18.9×10 4 19.2×10 4 21.3×10 4 24.8×10 4 25.2×10 4 21.9×10 4 20.7×10 4 and 19.2×10 4 .

[0156] The average molecular weights of Examples 1 to 12 are all in the range of 10 to 25 × 10⁻⁶. 4 Between these molecular weights, the average viscosity is low and the polymer is in a viscoelastic state, which is beneficial for reducing filtration loss.

[0157] Comparative Example 1

[0158] Same as Example 7, except that azira-14-crown-4 is replaced with 2,4-dimethyl-4-phenyltetrahydrofuran (cyclic ether CAS: 82461-14-1).

[0159] Comparative Example 2

[0160] Same as Example 7, except that the grafted monomer AM is replaced with AA (acrylic acid).

[0161] Comparative Example 3

[0162] Same as Example 7, except that the amount of aza-14-crown-4 added was replaced with 100g instead of 200g.

[0163] Comparative Example 4

[0164] Same as Example 7, except that the amount of AM added is replaced from 1800g to 800g, and the amount of AMPS added is replaced from 500g to 200g.

[0165] Test Example 1

[0166] Performance testing

[0167] The testing procedure includes the following steps:

[0168] 1) Preparation of bentonite-based slurry: Add 4.0 parts by weight of bentonite and 0.5 parts by weight of Na2CO3 to 100 parts by weight of deionized water. Stir and disperse at 5000 rpm for 30 min, then let stand at room temperature for 24 h for later use.

[0169] 2) The filtration loss reducers prepared in Examples 1-12 and Comparative Examples 1-4 were added to bentonite-based slurries at a rate of 2.0 wt% of the slurry. The mixture was stirred at 5000 rpm, and the performance before and after rolling aging at 240℃ for 16 h was measured. In addition, the high-temperature and high-pressure water loss (240℃ / 3.5 MPa) of the aged system was also measured. Performance tests were conducted according to the drilling fluid testing procedure of SY / T5621-1993. The filtration loss reduction and viscosity changes of Examples 1-12 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0170] 3) Using bentonite-based slurry as 100% by mass, 2.0 wt% of the filtration loss reducer prepared in Example 5 was added to the bentonite-based slurry, followed by the addition of CaCl2. The amounts of CaCl2 added were 0, 0.5 wt%, 1.0 wt%, 5.0 wt%, 8.0 wt%, 10.0 wt%, and 15.0 wt% of the bentonite-based slurry, respectively. The mixture was stirred at high speed at 5000 rpm, and the performance before and after rolling aging at 240℃ for 16 h was measured. The performance tests were conducted according to the drilling fluid testing procedures of SY / T5621-1993. The results of the drilling fluid performance changes with CaCl2 are shown in Table 2.

[0171] Table 1

[0172]

[0173] As shown in Table 1, the drilling fluid performance remained stable after adding the filtration loss reducers prepared in Examples 1-12, maintaining good viscosity and fluid loss even at 240℃. In contrast, the drilling fluids with the filtration loss reducers prepared in Comparative Examples 1-4 exhibited only average performance at room temperature, and their performance rapidly declined after aging at 240℃ for 16 hours.

[0174] Table 2

[0175]

[0176] As shown in Table 2, the present invention has strong resistance to calcium. When the amount of CaCl2 added is less than 10.0 wt%, its viscosity changes slowly and its water loss also changes very slowly, which indicates that the treatment agent can resist at least 8.0 wt% CaCl2.

[0177] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-temperature resistant filtration loss reducing agent, characterized in that, The high-temperature filtration loss reducing agent is a graft copolymer comprising sulfonated lignin and acrylamide monomers, wherein the sulfonated lignin is crown ether modified lignin after sulfonation treatment.

2. The filtration loss reducing agent according to claim 1, characterized in that, The raw materials for the crown ether modified lignin, by weight, include: Crown ether 150-300 parts, Inorganic base 30-60 parts, Formaldehyde 200-500 parts Lignin 1000-2000 parts, 4500-5500 parts of the first solvent; Preferably, the crown ether is an azacrown ether; more preferably, the azacrown ether is selected from at least one of aza14-crown-4, diaza14-crown-4, aza15-crown-5, diaza15-crown-5, aza18-crown-6, and diaza18-crown-6. Preferably, the lignin is selected from at least one of S-lignin, G-lignin, and H-lignin. Preferably, the inorganic base is selected from at least one of NaOH and KOH; Preferably, the first solvent is selected from at least one of water and ethanol.

3. The filtration loss reducing agent according to claim 2, characterized in that, The lignin is derived from the black liquor of alkali-process wheat straw pulp; preferably, the method for preparing the lignin includes: precipitating the black liquor of wheat straw pulp with 70-98 wt% sulfuric acid, removing the precipitate, washing it with a second solvent until neutral, and then drying and pulverizing the washed precipitate; Preferably, the second solvent is selected from at least one of water and ethanol; Preferably, the drying conditions include: a temperature of 50–120°C and a time of 8–15 hours; Preferably, the concentration of the sulfuric acid is 80-98 wt%, more preferably 90-98 wt%.

4. The filtration loss reducing agent according to claim 2 or 3, characterized in that, The preparation method of the crown ether modified lignin includes: S1. Add the crown ether and the inorganic base to the first solvent to carry out the first reaction; S2. Add formaldehyde and lignin to carry out the second reaction; S3. Remove the remaining formaldehyde from the reaction product obtained from the second reaction; Preferably, the mass ratio of the crown ether, formaldehyde, and lignin is 3:4-6:20-25.

5. The filtration loss reducing agent according to claim 4, characterized in that, The conditions for the first reaction include: a stirring speed of 100–300 rpm, a temperature of 10–40°C, and a time of 30–50 min; and / or The conditions for the second reaction include: a stirring speed of 1500–2500 rpm, a temperature of 50–100°C, and a time of 3–5 h.

6. The filtration loss reducing agent according to any one of claims 1-5, characterized in that, By weight, the raw materials for the sulfonation treatment include: crown ether modified lignin, sulfonating agent, and sulfonation catalyst. Preferably, the mass ratio of the sulfonating agent, the sulfonating catalyst, and the lignin is 50–160:1:62–200; Preferably, the sulfonating agent is selected from at least one of sodium sulfite, chlorosulfonic acid, and sulfur trioxide; Preferably, the sulfonation catalyst is selected from at least one of ferric chloride and ferric bromide; Preferably, the sulfonation treatment includes: adding a sulfonating agent and a sulfonation catalyst to the crown ether modified lignin to carry out a sulfonation reaction; More preferably, the conditions for the sulfonation reaction include: a stirring speed of 800-1200 rpm, a temperature of 80-100°C, a time of 5-8 h, and a system pH of 10 or higher, preferably 10-13.

7. The filtration loss reducing agent according to any one of claims 1-6, characterized in that, By weight, the raw materials for the graft copolymer include: sulfonated lignin, acrylamide monomers, and an initiator. Preferably, the mass ratio of the acrylamide monomer, the initiator, and the lignin is 30–100:1:20–67; Preferably, the acrylamide monomer includes acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and more preferably, the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 2 to 8:1, more preferably 3 to 4:1; Preferably, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, sodium bisulfite, benzoyl peroxide, and azobisisobutyronitrile.

8. The method for preparing the high-temperature filtration loss reducing agent according to any one of claims 1-7, characterized in that, Includes the following steps: S10. Inert gas is introduced into the sulfonated lignin to remove oxygen; S20, add acrylamide monomers and initiators to carry out graft polymerization reaction; S30. The mixture obtained from the graft polymerization reaction is washed, dried, and pulverized with a third solvent.

9. The preparation method according to claim 8, characterized in that, The inert gas is nitrogen; and / or The inert gas is introduced for 20–40 minutes; and / or The conditions for the graft polymerization reaction include: a stirring speed of 1800–2200 rpm, a temperature of 80–100°C, and a time of 2–4 h under an inert gas atmosphere; and / or The third solvent is selected from at least one of water and ethanol.

10. A drilling fluid, characterized in that, The high-temperature filtration reduction agent includes any one of claims 1-7 or the high-temperature filtration reduction agent prepared by the preparation method of claim 8 or 9. Preferably, the amount of the high-temperature filtration reduction agent added to the drilling fluid is 1-5 wt%.

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