A salt-resistant fluid loss reducer and its preparation method and application

Abstract

The present invention provides a salt-resistant fluid loss reducer and its preparation method and application, and specifically relates to the field of drilling technology. The preparation method provided by the present invention comprises: mixing refined cotton, a first alcohol solvent and an alkaline solution, performing an alkalization reaction, generating alkaline refined cotton, and obtaining an alkaline feed liquid; mixing the alkaline feed liquid with a chloroacetic acid aqueous solution and a quaternary ammonium salt organic compound, performing a condensation reaction, and obtaining a condensation product containing a quaternary ammonium salt; mixing the condensation product containing a quaternary ammonium salt with a second alcohol solvent and ethylene oxide, performing an etherification reaction, and obtaining an ethylene oxide-modified product; mixing the ethylene oxide-modified product with an epoxidized sulfonate, performing a substitution reaction, and obtaining a substitution product; adding an organic acid to the substitution product to adjust the pH value, adding a crosslinking agent, and performing a crosslinking reaction to obtain the salt-resistant fluid loss reducer. The present invention introduces a sulfonic acid group, a quaternary ammonium salt and a direct-linked hydroxyl group into a cellulose-based fluid loss reducer, and adopts a two-step substitution method to enhance the ability to resist high-price salts.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling, and in particular relates to a salt-resistant fluid loss reducer and a preparation method and application thereof. Background Art

[0002] As China's energy demand increases, shallow oil and gas resources are gradually exhausted, and oil and gas exploration and development are developing towards deep formations. The drilling depth in Xinjiang Uygur Autonomous Region, Sichuan Province and other places generally exceeds 6,000m, and the deepest is close to 9,000m. The temperature and pressure of deep formations are high, and the geological conditions are complex. During the drilling process, high-price salt formations are often encountered. The high-price salt and calcium formation environment is prone to cause drilling fluid contamination and treatment agent failure, causing drilling safety accidents and seriously affecting the drilling cycle. As one of the core treatment agents for drilling fluid, filtrate reducer plays a key role in reducing the intrusion of drilling fluid filtrate into the formation.

[0003] The fluid loss reducers currently used in the market include natural modified and polymer types. Natural modified types mainly include CMC (carboxymethyl cellulose), PAC (polyanionic cellulose), asphalt, etc., while polymer types mainly include acrylamide, acrylic acid, AMPS (2-acrylamido-2-methylpropane sulfonic acid) and other multi-linear polymers. Although these fluid loss reducers can resist monovalent salts such as sodium chloride, their effects are significantly reduced in formations containing divalent salts, and in severe cases, they even fail directly, causing the on-site drilling fluid loss to be out of control, leading to underground accidents. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a salt-resistant fluid loss reducer and a preparation method and application thereof. The salt-resistant fluid loss reducer prepared by the present invention has good fluid loss reduction effect, high-price salt resistance and temperature resistance.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a salt-resistant fluid loss reducer, comprising the following steps:

[0007] The refined cotton, the first alcohol solvent and the alkali solution are mixed to carry out an alkalization reaction to generate alkalized refined cotton and obtain an alkalized feed solution;

[0008] The alkalized feed liquid is mixed with a chloroacetic acid aqueous solution and a quaternary ammonium salt organic compound to carry out a condensation reaction to obtain a condensation product containing a quaternary ammonium salt;

[0009] The condensation product containing the quaternary ammonium salt is mixed with a second alcohol solvent and ethylene oxide to carry out an etherification reaction to obtain an ethylene oxide-modified product;

[0010] The ethylene oxide modified product is mixed with an epoxidized sulfonate to carry out a substitution reaction to obtain a substitution product;

[0011] An organic acid is added to the substituted product to adjust the pH value, and a cross-linking agent is added to cause a cross-linking reaction to obtain the salt-resistant fluid loss reducer.

[0012] Preferably, the fineness of the refined cotton is 200-300 mesh;

[0013] The mass fraction of chloroacetic acid in the chloroacetic acid aqueous solution is 45-55%;

[0014] The mass ratio of the refined cotton to chloroacetic acid is 1:0.4-1.2.

[0015] Preferably, the quaternary ammonium salt organic compound includes glycidyltrimethylammonium chloride;

[0016] The mass ratio of the refined cotton to the quaternary ammonium salt organic compound is 1:0.1-0.2;

[0017] The condensation reaction temperature is 55-70° C. and the reaction time is 1-3 hours.

[0018] Preferably, the first alcohol solvent includes propanol; the mass concentration of the alkaline solution is 45-50%, and the alkali in the alkaline solution is sodium hydroxide and / or potassium hydroxide;

[0019] The temperature of the alkalization reaction is 65-75° C. and the time is 1.5-3 hours.

[0020] Preferably, the second alcohol solvent comprises ethanol;

[0021] The mass ratio of the refined cotton to ethylene oxide is 1:0.2-0.5;

[0022] The temperature of the etherification reaction is 20-30° C. and the time is 1-3 hours.

[0023] Preferably, the epoxidized sulfonate is one or more of epoxidized sodium propanesulfonate, epoxidized sodium butanesulfonate and epoxidized sodium pentanesulfonate;

[0024] The mass ratio of the refined cotton to the epoxidized sulfonate is 1:0.2-0.4;

[0025] The temperature of the substitution reaction is 20-30° C., and the time is 1-3 hours.

[0026] Preferably, the cross-linking agent is one or more of glyoxal, malondialdehyde and succinaldehyde;

[0027] The mass of the cross-linking agent accounts for 0.1-0.5% of the mass of the refined cotton;

[0028] The temperature of the cross-linking reaction is 40-50° C. and the time is 1-3 hours.

[0029] Preferably, the organic acid is formic acid, and the pH value is 4-6.

[0030] The present invention also provides a salt-resistant fluid loss reducer prepared by the preparation method described in the above technical scheme.

[0031] The present invention also provides the use of the salt-resistant fluid loss reducer described in the above technical solution in drilling fluid, wherein the mass concentration of the salt-resistant fluid loss reducer in the drilling fluid is 1-3%.

[0032] The invention provides a preparation method of a calcium salt resistant fluid loss reducer, comprising the following steps: mixing refined cotton, a first alcohol solvent and an alkali solution, performing an alkalization reaction, generating alkalized refined cotton, and obtaining an alkalized feed liquid; mixing the alkalized feed liquid with a chloroacetic acid aqueous solution and a quaternary ammonium salt organic compound, performing a condensation reaction, and obtaining a condensation product containing a quaternary ammonium salt; mixing the condensation product containing the quaternary ammonium salt with a second alcohol solvent and ethylene oxide, performing an etherification reaction, and obtaining an ethylene oxide modified product; mixing the ethylene oxide modified product with an epoxidized sulfonate, performing a substitution reaction, and obtaining a substitution product; adding an organic acid to the substitution product to adjust the pH value, adding a crosslinking agent, performing a crosslinking reaction, and obtaining the salt resistant fluid loss reducer. The invention introduces sulfonic acid groups, salt-resistant group quaternary ammonium salts and straight-chain hydroxyl groups (after ring opening, ethylene oxide undergoes nucleophilic substitution reaction with hydroxyl groups on cellulose side chains to form open chain hydroxyl groups) on the basis of a cellulose-based fluid loss reducer (refined cotton) containing a carboxyl group, thereby enhancing the salt resistance and temperature resistance of the fluid loss reducer; adopts a two-step substitution method, firstly adopts a chlorine band method to introduce quaternary ammonium salts, and then adopts epoxidation to introduce straight-chain hydroxyl groups and sulfonic acid groups, thereby greatly improving the degree of substitution on cellulose; and due to the two-step substitution method, two or more substitution groups exist on part of the ring structure in the main chain of the cellulose molecule, thereby greatly improving the water solubility of the fluid loss reducer and further improving the ability of the fluid loss reducer to resist divalent calcium salts; the introduction of the salt-resistant group not only enhances the salt resistance of the fluid loss reducer, but also improves the temperature resistance of the fluid loss reducer to a certain extent because the salt-resistant group has certain anti-oxidation and anti-degradation effects.

[0033] The heat-resistant and salt-resistant products on the market are all grafted with polymer molecules, and the proportion of polymer molecules is very high. It is the polymer that plays the role of heat and salt resistance. The present invention adds substitution groups to the cellulose chain, and increases the degree of substitution and the type of substitution groups through a two-step method. This not only makes the product have a high-price salt resistance effect, but also has good degradation ability, and the product is more environmentally friendly. Because the present invention adopts special groups and synthesis methods, the prepared fluid loss reducer has a much higher high-price salt resistance than the current fluid loss reducer products on the market. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a salt-resistant fluid loss reducer, comprising the following steps:

[0035] The refined cotton, the first alcohol solvent and the alkali solution are mixed to carry out an alkalization reaction to generate alkalized refined cotton and obtain an alkalized feed solution;

[0036] The alkalized feed liquid is mixed with a chloroacetic acid aqueous solution and a quaternary ammonium salt organic compound to carry out a condensation reaction to obtain a condensation product containing a quaternary ammonium salt;

[0037] The condensation product containing the quaternary ammonium salt is mixed with a second alcohol solvent and ethylene oxide to carry out an etherification reaction to obtain an ethylene oxide-modified product;

[0038] The ethylene oxide modified product is mixed with an epoxidized sulfonate to carry out a substitution reaction to obtain a substitution product;

[0039] An organic acid is added to the substituted product to adjust the pH value, and a cross-linking agent is added to cause a cross-linking reaction to obtain the salt-resistant fluid loss reducer.

[0040] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known in the art.

[0041] The invention mixes refined cotton, a first alcohol solvent and an alkali solution, performs an alkalization reaction, generates alkalized refined cotton, and obtains an alkalized feed solution.

[0042] In the present invention, the mass content of α-cellulose in the refined cotton is preferably ≥98%, and the average polymerization degree of wood pulp powder and wood pulp fiber is 900-1600.

[0043] In the present invention, the fineness of the refined cotton is preferably 200-300 mesh. In the present invention, the mass ratio of the refined cotton to the first alcohol solvent is preferably 1:1-3. In a specific embodiment, the mass ratio of the refined cotton to the first alcohol solvent can be 1:1, 1:2 or 1:3.

[0044] In the present invention, the first alcohol solvent is preferably propanol, and the propanol is preferably n-propanol and / or isopropanol. In a specific embodiment, the present invention preferably uses isopropanol. Using isopropanol as a solvent, the salt-resistant fluid loss reducer obtained has a better effect.

[0045] In the present invention, the alkali in the alkaline solution is preferably sodium hydroxide and / or potassium hydroxide, and the mass concentration of the alkaline solution is preferably 45-50%. In a specific embodiment, the mass concentration of the alkaline solution may be 45%, 47% or 50%. In the present invention, the mass ratio of the refined cotton to the alkaline solution is preferably 1:1-3. In a specific embodiment, the mass ratio of the refined cotton to the alkaline solution may be 1:1, 1:2 or 1:3.

[0046] In the present invention, the temperature of the alkalization reaction is preferably 65-75°C. In a specific embodiment, the temperature of the alkalization reaction can be 65°C, 70°C or 75°C. The time of the alkalization reaction is preferably 1.5-3h. In a specific embodiment, the time of the alkalization reaction can be 1.5h, 2h, 2.5h or 3h. In the alkalization reaction, the fine cotton reacts with the alkali to obtain a cellulose alkalization product. Alkali cellulose is generated by alkalization, which makes it highly reactive.

[0047] The present invention has no special requirements on the mixing method, and can adopt the technical means known in the art, such as stirring, shaking, etc. In the present invention, it is preferred to first mix the refined cotton with the alcohol solvent, and then add the alkali solution to carry out the alkalization reaction.

[0048] After obtaining the alkalized feed liquid, the present invention mixes the alkalized feed liquid with a chloroacetic acid aqueous solution and a quaternary ammonium salt organic compound to carry out a condensation reaction to obtain a condensation product containing a quaternary ammonium salt.

[0049] In the present invention, the mass fraction of chloroacetic acid in the chloroacetic acid aqueous solution is preferably 45-55%. In a specific embodiment, the mass fraction of chloroacetic acid in the chloroacetic acid aqueous solution can be 45%, 47%, 50%, 53% or 55%.

[0050] In the present invention, the mass ratio of the refined cotton to the chloroacetic acid in the chloroacetic acid aqueous solution is preferably 1:0.4-1.2. In a specific embodiment, the mass ratio of the refined cotton to the chloroacetic acid in the chloroacetic acid aqueous solution can be 1:0.4, 1:0.6, 1:0.8, 1:1 or 1:1.2.

[0051] In the present invention, the quaternary ammonium salt organic compound is preferably epoxypropyl trimethyl ammonium chloride. The mass ratio of the refined cotton to the quaternary ammonium salt organic compound is preferably 1:0.1-0.2. In a specific embodiment, the mass ratio of the refined cotton to the quaternary ammonium salt organic compound can be 1:0.12, 1:0.14, 1:0.16, 1:0.18 or 1:0.2.

[0052] In the present invention, the temperature of the condensation reaction is preferably 55-70°C. In a specific embodiment, the temperature of the condensation reaction can be 55°C, 60°C, 65°C or 70°C. The time of the condensation reaction is preferably 1-3h. In a specific embodiment, the time of the condensation reaction can be 1h, 2h or 3h. In the condensation reaction, the hydroxyl group of the side chain on the alkalized cellulose condenses with the quaternary ammonium salt organic compound, and the quaternary ammonium salt is introduced into the molecular structure of the alkalized cellulose, which increases the degree of substitution and substitution groups of the cellulose and improves the salt resistance of the fluid loss reducer.

[0053] After the condensation reaction is completed, if the solid matter in the obtained condensation product liquid is not completely immersed, the present invention preferably adds an alkaline solution to the obtained condensation product liquid until all the solid products are immersed, squeezes out the excess alkaline water after soaking, and crushes the obtained residue to obtain a condensation product containing a quaternary ammonium salt.

[0054] If the solid matter in the condensation product liquid obtained after the condensation reaction is completely submerged in the liquid, the present invention preferably directly squeezes the condensation product liquid to squeeze out excess alkaline water, and grinds the obtained residue to obtain a condensation product containing a quaternary ammonium salt.

[0055] In the present invention, the condensation product containing the quaternary ammonium salt is a solid-liquid mixture.

[0056] The present invention controls the water content in the solid-liquid mixture by controlling the addition of alkali solution and squeezing, thereby ensuring smooth progress of subsequent reactions.

[0057] The present invention has no special requirements on the method of pressing, and the commonly used technical means in the field can be adopted.

[0058] In the present invention, the mass of the liquid in the post-pressing control system is preferably such that the mass of the liquid accounts for 1 / 4 of the total mass of all substances in the system.

[0059] The present invention has no special requirements on the method of pulverizing, and the commonly used technical means in the art can be used.

[0060] After obtaining the condensation product containing the quaternary ammonium salt, the present invention mixes the condensation product containing the quaternary ammonium salt with a second alcohol solvent and ethylene oxide to carry out an etherification reaction to obtain an ethylene oxide modified product.

[0061] In the present invention, the second alcohol solvent is preferably ethanol, and the mass ratio of the refined cotton to the second alcohol solvent is preferably 1:0.5-0.7. In a specific embodiment, the mass ratio of the refined cotton to the second alcohol solvent can be 1:0.5, 1:0.6 or 1:0.7.

[0062] In the present invention, mixing the condensation product containing the quaternary ammonium salt with the second alcohol solvent and ethylene oxide preferably comprises: mixing the condensation product containing the quaternary ammonium salt with the second alcohol solvent, and then adding ethylene oxide to mix.

[0063] In the present invention, the step of vacuuming and filling with inert gas before adding ethylene oxide is preferred. The vacuum degree of the vacuuming is preferably -0.08 MPa, and the inert gas is preferably nitrogen. Specifically, the vacuuming and filling with inert gas are repeated 3 to 6 times until the air is completely removed.

[0064] In the present invention, the ethylene oxide is preferably precooled before mixing. The precooling temperature is preferably -5 to -10° C. The precooling allows the ethylene oxide to remain in a liquid state.

[0065] In the present invention, the mass ratio of the refined cotton to ethylene oxide is preferably 1:0.2-0.5. In a specific embodiment, the mass ratio of the refined cotton to ethylene oxide can be 1:0.2, 1:0.3, 1:0.4 or 1:0.5. In the present invention, the temperature of the etherification reaction is preferably 20-30°C. In a specific embodiment, the temperature of the etherification reaction can be 20°C, 25°C or 30°C; the time is preferably 1-3h. In a specific embodiment, the time can be 1h, 2h or 3h. During the etherification reaction, ethylene oxide preferentially undergoes a ring-opening reaction, and after the ring-opening, an etherification reaction occurs with the remaining hydroxyl groups on the side chains of the alkalized cellulose, and a linear hydroxyl group is introduced into the molecular structure of the alkalized cellulose, further increasing the degree of substitution and the substitution group of the cellulose, and improving the salt resistance of the fluid loss reducer.

[0066] After obtaining the ethylene oxide modified product, the present invention mixes the ethylene oxide modified product with an epoxidized sulfonate to carry out a substitution reaction to obtain a substitution product.

[0067] In the present invention, the epoxidized sulfonate is preferably one or more of epoxidized propane sulfonate sodium, epoxidized butylene sulfonate sodium and epoxidized pentane sulfonate sodium. In a specific embodiment, the epoxidized sulfonate may be epoxidized propane sulfonate sodium, epoxidized butylene sulfonate sodium or epoxidized pentane sulfonate sodium. In the present invention, the mass ratio of the refined cotton to the epoxidized sulfonate is preferably 1:0.2-0.4. In a specific embodiment, the mass ratio of the refined cotton to the epoxidized sulfonate may be 1:0.2, 1:0.25, 1:0.3, 1:0.36 or 1:0.4.

[0068] In the present invention, the temperature of the substitution reaction is preferably 20-30°C, and in a specific embodiment, the temperature of the substitution reaction can be 20°C, 25°C or 30°C; the time is preferably 1-3h, and in a specific embodiment, the time can be 1h, 2h or 3h. During the substitution reaction, the sulfonic acid group in the epoxidized sulfonate undergoes a substitution reaction with the remaining hydroxyl group on the side chain of the alkalized cellulose, and the sulfonic acid group is introduced into the molecular structure of the alkalized cellulose, further increasing the degree of substitution and the substitution group of the cellulose, and improving the salt resistance of the fluid loss reducer.

[0069] After completing the substitution reaction, the present invention preferably performs solid-liquid separation and washing on the obtained product liquid to obtain the substitution product. The present invention has no special requirements on the method of the solid-liquid separation, and the commonly used technical means in the art can be adopted, such as centrifugation, suction filtration, etc. In the present invention, the washing preferably uses 70wt% ethanol aqueous solution, and the number of times is preferably 2 to 3 times. In the present invention, the ethanol aqueous solution is preferably recovered after the washing. By recovering the ethanol aqueous solution, the industrial cost is reduced. The ethanol aqueous solution is used to remove the chloride ions.

[0070] After obtaining the substitution product, the present invention adds an organic acid to the substitution product to adjust the pH value, adds a cross-linking agent, causes a cross-linking reaction, and obtains a salt-resistant fluid loss reducer.

[0071] In the present invention, the organic acid is preferably formic acid, and the pH value is preferably 4-6. In a specific embodiment, the pH value may be 4, 5 or 6.

[0072] In the present invention, the cross-linking agent is preferably one or more of glyoxal, malondialdehyde and succinaldehyde. In a specific embodiment, the cross-linking agent can be glyoxal, malondialdehyde or succinaldehyde. In the present invention, the mass of the cross-linking agent preferably accounts for 0.1-0.5% of the mass of the refined cotton. In a specific embodiment, the mass of the cross-linking agent can account for 0.1%, 0.2%, 0.3%, 0.4% or 0.5% of the mass of the refined cotton.

[0073] In the present invention, the temperature of the cross-linking reaction is preferably 40-50°C. In a specific embodiment, the temperature of the cross-linking reaction can be 40°C, 45°C or 50°C. The time is preferably 1-3h. In a specific embodiment, the time can be 1h, 2h or 3h.

[0074] After the cross-linking reaction is completed, the present invention preferably further comprises sequentially subjecting the obtained product liquid to solid-liquid separation, washing, distillation, drying and pulverization to obtain the salt-resistant fluid loss reducer.

[0075] The present invention has no special requirements on the distillation method, and the commonly used technical means in the art can be used. The residual propanol solvent is removed by distillation.

[0076] The present invention has no special requirements on the drying method and can adopt the commonly used technical means in the art.

[0077] The present invention has no special requirements on the method of pulverization, and the commonly used technical means in the field can be adopted.

[0078] The present invention also provides a salt-resistant fluid loss reducer prepared by the preparation method described in the above technical scheme.

[0079] The invention introduces sulfonic acid groups, salt-resistant quaternary ammonium salts and straight-chain hydroxyls on the basis of a cellulose-based fluid loss reducer containing a carboxyl group, thereby enhancing the high-price salt resistance and temperature resistance of the fluid loss reducer; a two-step method is adopted, wherein the quaternary ammonium salt is first introduced by a chlorine band method, and then the straight-chain hydroxyls and sulfonic acid groups are introduced by epoxidation, thereby greatly improving the degree of substitution; and due to the two-step substitution method, two substitution groups exist on some of the ring structures, thereby greatly improving the water solubility of the fluid loss reducer and further improving the high-price salt resistance of the fluid loss reducer; the introduction of the salt-resistant group not only enhances the salt resistance of the fluid loss reducer, but also improves the temperature resistance of the fluid loss reducer to a certain extent because the salt-resistant group has certain anti-oxidation and anti-degradation effects.

[0080] The invention also provides application of the anti-calcium salt fluid loss reducer in drilling fluid. The mass concentration of the anti-calcium salt fluid loss reducer in the drilling fluid is 1-3%.

[0081] In the present invention, the drilling fluid preferably includes anhydrous calcium chloride, sodium bicarbonate, evaluation soil, anti-high-price calcium salt fluid loss reducer and water. The mass concentration of the anti-high-price calcium salt fluid loss reducer in the drilling fluid is preferably 1-3%. In a specific embodiment, the mass concentration of the anti-high-price calcium salt fluid loss reducer in the drilling fluid can be 1%, 1.5%, 2%, 2.5% or 3%; the mass concentration of the anhydrous calcium chloride in the drilling fluid is preferably 0-20%. In a specific embodiment, the mass concentration of the anhydrous calcium chloride in the drilling fluid can be 0, 5%, 10%, 15% or 20%; the mass concentration of the sodium bicarbonate in the drilling fluid is preferably 0.25%; the mass concentration of the evaluation soil in the drilling fluid is preferably 8%.

[0082] The present invention has no special requirements for the preparation method of the drilling fluid, and a preparation method well known in the art can be used. In the embodiment of the present invention, specifically, anhydrous calcium chloride, sodium bicarbonate, and evaluation soil are added to distilled water in sequence, and each sample is stirred for 5 minutes before adding the next sample. After all are added, stir at 6000r / min for 20 minutes, and maintain at room temperature for 24 hours to obtain a base slurry. Salt-resistant fluid loss reducer is added to the base slurry, stirred at high speed for 20 minutes, aged at 120°C in an aging tank for 16 hours, and stirred at 6000r / min for 5 minutes after cooling.

[0083] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described in conjunction with specific embodiments below. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Any modification, equivalent replacement, improvement, etc. made to the implementation methods of the present invention based on the technical essence and general principles of the present invention without creative work should be within the scope of protection of the present invention.

[0084] Example 1

[0085] The α-cellulose in refined cotton is ≥98%, and the average polymerization degree of wood pulp powder and wood pulp fiber is 900-1600.

[0086] 50g of refined cotton with a fineness of 200-300 mesh and 100g of isopropanol were added to the reactor and mixed evenly, and 50g of 47wt% sodium hydroxide alkali solution was added to carry out alkalization reaction. After the alkalization reaction was completed, 40g of 50wt% chloroacetic acid aqueous solution and 6g of epoxypropyltrimethylammonium chloride were added to the reactor, and condensation reaction was carried out at 60°C for 2h, and the mass of the alkali water was controlled to account for 1 / 4 of the total mass of all substances in the reactor, and the pulverized material was obtained.

[0087] The crushed material was mixed evenly with 30g of anhydrous ethanol in a reactor, and vacuumed and filled with nitrogen repeatedly until the air in the reactor was completely removed, and then 14g of pre-cooled ethylene oxide liquid was added, and the reaction was carried out at 25°C for 2h, and then 10g of sodium epoxypropanesulfonate was added, and the reaction was carried out at 25°C for 2h. Filter and wash with ethanol to obtain the substitution product. The pH of the substitution product was adjusted to 4-6 with formic acid, and 0.05g of malondialdehyde was added, and the reaction was carried out at 45°C for 1h, and then filtered, and the solid was washed with 70wt% ethanol solution, distilled, dried, and crushed to obtain a salt-resistant fluid loss reducer.

[0088] Example 2

[0089] 50g of refined cotton with a fineness of 200-300 mesh and 100g of isopropanol were added to the reactor and mixed evenly, and 50g of 47wt% sodium hydroxide alkali solution was added to carry out alkalization reaction. After the alkalization reaction was completed, 60g of 50wt% chloroacetic acid aqueous solution and 8g of epoxypropyltrimethylammonium chloride were added to the reactor, reacted at 60°C for 2h, the mass of the alkali water was controlled to account for 1 / 4 of the total mass of all substances in the reactor, and crushed to obtain the crushed material.

[0090] The crushed material was mixed evenly with 30g of anhydrous ethanol in a reactor, and vacuumed and filled with nitrogen repeatedly until the air in the reactor was completely removed, and then 24g of pre-cooled ethylene oxide liquid was added, and the reaction was carried out at 25°C for 2h, and then 18g of sodium epoxybutanesulfonate was added, and the reaction was carried out at 25°C for 2h. Filter and wash with ethanol to obtain a polymerized product. The pH of the substituted product was adjusted to 4-6 with formic acid, and 0.15g of malondialdehyde was added, and the reaction was carried out at 45°C for 1h, and then filtered, and the solid was washed with 70wt% ethanol solution, distilled, dried, and crushed to obtain a high-price salt filtrate reducer.

[0091] Comparative Example 1

[0092] Only one-step substitution reaction:

[0093] 50g of refined cotton with a fineness of 200-300 mesh and 100g of isopropanol were added to the reactor and mixed evenly, and 50g of 47wt% sodium hydroxide alkali solution was added for alkalization reaction. After the alkalization reaction was completed, 40g of 50wt% chloroacetic acid aqueous solution and 6g of epoxypropyltrimethylammonium chloride were added to the reactor, reacted at 60℃ for 6h, filtered, washed the solid with 70wt% ethanol solution, distilled, dried, and crushed to obtain a high-price salt filtrate reducer

[0094] Comparative Example 2

[0095] No epoxidation modification groups:

[0096] 50g of refined cotton with a fineness of 200-300 mesh and 100g of isopropanol were added to the reactor and mixed evenly, and 50g of 47wt% sodium hydroxide alkali solution was added to carry out alkalization reaction. After the alkalization reaction was completed, 40g of 50wt% chloroacetic acid aqueous solution and 6g of epoxypropyltrimethylammonium chloride were added to the reactor, reacted at 60°C for 2h, the mass of the alkali water was controlled to account for 1 / 4 of the total mass of all substances in the reactor, and the pulverized material was obtained.

[0097] The crushed material was mixed evenly with 30g of anhydrous ethanol in a reactor, and vacuumed and filled with nitrogen repeatedly until the air in the reactor was completely removed, and then 14g of pre-cooled ethylene oxide liquid was added, and the reaction was carried out at 25°C for 2h. Filtered, washed with ethanol, and the substitution product was obtained. The pH of the substitution product was adjusted to 4-6 with formic acid, 0.05g of malondialdehyde was added, and the reaction was carried out at 45°C for 1h, filtered, and the solid was washed with 70wt% ethanol solution, distilled, dried, and crushed to obtain a high-price salt filtrate reducer.

[0098] Comparative Example 3

[0099] No epoxypropyltrimethylammonium chloride anti-salt group:

[0100] 50g of 200-300 mesh refined cotton and 100g of isopropanol were added to the reactor and mixed evenly, and 50g of 47wt% sodium hydroxide alkali solution was added to carry out alkalization reaction. After the alkalization reaction was completed, 40g of 50wt% chloroacetic acid aqueous solution was added to the reactor, reacted at 60°C for 2h, the mass of the alkali water was controlled to account for 1 / 4 of the total mass of all substances in the reactor, and crushed to obtain the crushed material.

[0101] The crushed material was mixed evenly with 30g of anhydrous ethanol in a reactor, and vacuumed and filled with nitrogen repeatedly until the air in the reactor was completely removed, and then 14g of pre-cooled ethylene oxide liquid was added, and the reaction was carried out at 25°C for 2h, and then 10g of sodium epoxypropanesulfonate was added, and the reaction was carried out at 25°C for 2h. Filter and wash with ethanol to obtain the substitution product. The pH of the substitution product was adjusted to 4-6 with formic acid, and 0.05g of malondialdehyde was added, and the reaction was carried out at 45°C for 1h, and then filtered, and the solid was washed with 70wt% ethanol solution, distilled, dried, and crushed to obtain a high-price salt filtrate reducer.

[0102] Comparative Example 4

[0103] No ethylene oxide modification:

[0104] 50g of refined cotton with a fineness of 200-300 mesh and 100g of isopropanol were added to the reactor and mixed evenly, and 50g of 47wt% sodium hydroxide alkali solution was added to carry out alkalization reaction. After the alkalization reaction was completed, 40g of 50wt% chloroacetic acid aqueous solution and 6g of epoxypropyltrimethylammonium chloride were added to the reactor, reacted at 60°C for 2h, the mass of the alkali water was controlled to account for 1 / 4 of the total mass of all substances in the reactor, and the pulverized material was obtained.

[0105] The crushed material was mixed evenly with 30g of anhydrous ethanol in a reactor, and vacuumed and filled with nitrogen repeatedly until the air in the reactor was completely removed, and then 10g of sodium epoxypropanesulfonate was added and reacted at 25°C for 2h. Filtered and washed with ethanol to obtain a substituted product. The pH of the substituted product was adjusted to 4-6 with formic acid, and 0.05g of malondialdehyde was added and reacted at 45°C for 1h, filtered, and the solid was washed with 70wt% ethanol solution, distilled, dried, and crushed to obtain a high-price salt filtrate reducer.

[0106] Performance characterization:

[0107] The specific preparation method of the drilling fluid is as follows: take 400mL of distilled water, add anhydrous calcium chloride, 1g of sodium bicarbonate, and 32g of evaluation soil in sequence, stir for 5min after each sample is added, and then add the next sample. After all are added, stir at 6000r / min for 20min, and maintain at room temperature for 24h to obtain a base slurry, in which the mass concentration of anhydrous calcium chloride in the base slurry is 0-20%. Add 6g of the anti-high-price salt fluid loss reducer prepared in Examples 1-2 or Comparative Examples 1-4 to the base slurry, the mass concentration of the anti-high-price salt fluid loss reducer is 1.5%, stir at high speed for 20min, age at 120°C in an aging tank for 16h, stir at 6000r / min for 5min after cooling, and determine its fluid loss and apparent viscosity according to the provisions of 6.3, 7.2, and 7.3 in GB / T16783.1-2014 (LV-CMC and LV-PAC are both products of Chongqing Lihong Fine Chemical Co., Ltd.), and draw them into Tables 1 and 2.

[0108] Table 1 Apparent viscosity properties of high-price salt resistant fluid loss reducers prepared in Examples 1 to 2 and Comparative Examples 1 to 4 in high-price salt

[0109]

[0110] Table 2 Filtrate loss of high-price salt resistant filtrate reducers prepared in Examples 1 to 2 and Comparative Examples 1 to 4 in high-price salt

[0111]

[0112] It can be seen from the data in Table 1 and Table 2 that when there is no calcium chloride concentration, the viscosity of Example 1 and Example 2 is equivalent to that of LV-PAC and higher than that of LV-CMC, while the water loss is significantly lower than that of LV-CMC and LV-PAC, showing a good water loss reduction effect. Moreover, after the calcium chloride concentration is increased, the viscosity of Example 1 and Example 2 is reduced but the reduction is limited, and the water loss increases slowly, showing a good calcium resistance. However, for LV-PAC and LV-CMC, as the calcium chloride concentration increases, the viscosity decreases rapidly and the water loss increases rapidly, showing that the calcium resistance is not strong, which further shows the calcium resistance of the product of the present invention.

[0113] Compared with Example 1, there is only one step reaction in Comparative Example 1, which results in that the viscosity and high temperature and high pressure water loss of the fresh water and different calcium chloride salt slurries in the system are much greater than those in Example 1, thus reflecting the importance of the two-step method in the present invention.

[0114] Compared with Example 1, Comparative Example 2 does not add epoxidized modified groups in Comparative Example 2, so that the viscosity and filtration loss viscosity of the fresh water and calcium chloride salt slurries with different calcium chloride concentrations and high temperature and high pressure water loss of the system are greater than those of Example 1, reflecting the importance of epoxidized modified groups in the present invention.

[0115] Compared with Example 1, no salt-resistant group was added in Comparative Example 3, so that the viscosity and filtration loss viscosity of the fresh water and calcium chloride salt slurries with different calcium chloride concentrations and the high-temperature and high-pressure water loss of the system were greater than those of Example 1, reflecting the importance of the salt-resistant group in the present invention.

[0116] Compared with Example 1, Comparative Example 4 does not add ethylene oxide liquid modification in Comparative Example 4, so that the product does not contain a linear hydroxyethyl group. The viscosity and filtration loss viscosity of fresh water and calcium chloride salt slurries with different calcium chloride concentrations and high temperature and high pressure water loss of the system are greater than those of Example 1, reflecting the importance of the linear hydroxyethyl group in the present invention.

[0117] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a salt-resistant fluid loss reducer, characterized in that: The following steps are involved: The refined cotton, the first alcohol solvent and the alkali solution are mixed to carry out an alkalization reaction to generate alkalized refined cotton and obtain an alkalized feed solution; The alkalized feed liquid is mixed with a chloroacetic acid aqueous solution and a quaternary ammonium salt organic compound to carry out a condensation reaction to obtain a condensation product containing a quaternary ammonium salt; The condensation product containing the quaternary ammonium salt is mixed with a second alcohol solvent and ethylene oxide to carry out an etherification reaction to obtain an ethylene oxide-modified product; The ethylene oxide modified product is mixed with an epoxidized sulfonate to carry out a substitution reaction to obtain a substitution product; An organic acid is added to the substituted product to adjust the pH value, and a cross-linking agent is added to cause a cross-linking reaction to obtain the salt-resistant fluid loss reducer.

2. The preparation method according to claim 1, characterized in that: The fineness of the refined cotton is 200-300 mesh; The mass fraction of chloroacetic acid in the chloroacetic acid aqueous solution is 45-55%; The mass ratio of the refined cotton to chloroacetic acid is 1:0.4-1.

2.

3. The preparation method according to claim 1, characterized in that: The quaternary ammonium salt organic compound includes glycidyltrimethylammonium chloride; The mass ratio of the refined cotton to the quaternary ammonium salt organic compound is 1:0.1-0.2; The condensation reaction temperature is 55-70° C. and the reaction time is 1-3 hours.

4. The preparation method according to claim 1, characterized in that: The first alcohol solvent includes propanol; the mass concentration of the alkaline solution is 45-50%, and the alkali in the alkaline solution is sodium hydroxide and / or potassium hydroxide; The temperature of the alkalization reaction is 65-75° C. and the time is 1.5-3 hours.

5. The preparation method according to claim 1, characterized in that: The second alcohol solvent includes ethanol; The mass ratio of the refined cotton to ethylene oxide is 1:0.2-0.5; The temperature of the etherification reaction is 20-30° C. and the time is 1-3 hours.

6. The preparation method according to claim 1, characterized in that: The epoxidized sulfonate is one or more of epoxidized propane sulfonate sodium, epoxidized butyl sulfonate sodium and epoxidized pentane sulfonate sodium; The mass ratio of the refined cotton to the epoxidized sulfonate is 1:0.2-0.4; The temperature of the substitution reaction is 20-30° C., and the time is 1-3 hours.

7. The preparation method according to claim 1, characterized in that: The cross-linking agent is one or more of glyoxal, malondialdehyde and succinaldehyde; The mass of the cross-linking agent accounts for 0.1-0.5% of the mass of the refined cotton; The temperature of the cross-linking reaction is 40-50° C. and the time is 1-3 hours.

8. The preparation method according to claim 1, characterized in that: The organic acid is formic acid, and the pH value is 4-6.

9. The salt-resistant fluid loss reducer prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the salt-resistant fluid loss reducer according to claim 9 in drilling fluid, characterized in that: The mass concentration of the salt resistance fluid loss reducer in the drilling fluid is 1-3%.

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