Strong-adsorption hyperbranched filtrate reducer for 240 DEG C saturated salt water-based drilling fluid as well as preparation method and application of strong-adsorption hyperbranched filtrate reducer

Abstract

The invention relates to the technical field of drilling, and discloses a strong-adsorption hyperbranched filtrate reducer for 240 DEG C saturated salt water-based drilling fluid as well as a preparation method and application of the strong-adsorption hyperbranched filtrate reducer. The filtrate reducer comprises a first structural unit, a second structural unit, a third structural unit, a fourth structural unit, a fifth structural unit and a sixth structural unit, the first structural unit is provided by an anionic hydration enhancing monomer, the second structural unit is provided by a cationic positive electricity adsorption monomer, the third structural unit is provided by a cationic positive electricity adsorption monomer, and the sixth structural unit is provided by a cationic positive electricity adsorption monomer. The third structural unit is provided by a main chain monomer, the fourth structural unit is provided by a cyclic monomer, the fifth structural unit is provided by a polyether monomer, and the sixth structural unit is provided by a hyperbranched structural monomer. The filtrate reducer disclosed by the invention can keep good rheology and filtrate reduction performance of drilling fluid under the conditions of 240 DEG C and saturated salt, and is stable for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling, and in particular to a fluid loss reducer and a preparation method and application thereof, and more particularly to a highly adsorbable hyperbranched fluid loss reducer for 240°C saturated salt water-based drilling fluid and a preparation method and application thereof. Background Art

[0002] Drilling fluid is an indispensable key technology to ensure the safe and efficient exploration and development of ultra-deep and ultra-deep oil and gas. Its performance determines the safety, efficiency and success of drilling. However, ultra-deep drilling fluid faces unprecedented major challenges: ultra-high temperature (≥200℃), ultra-high pressure (≥140MPa), ultra-high salt (≥200000mg / L), and ultra-high stress (≥160MPa). These problems make it difficult to control the stability of drilling fluid performance, which is easy to cause accidents such as well collapse, well leakage, and blowout. The cost of ultra-deep and ultra-deep wells is high. Once an accident occurs, it will cause huge economic losses and even evolve into a catastrophic accident of "well destruction and death". The most critical factor in stabilizing the performance of drilling fluid is the fluid loss reducer, but there is currently a lack of drilling fluid fluid loss reducers that are resistant to ultra-high temperature and ultra-high pressure saturated salt (36% NaCl), especially a lack of fluid loss reducers that are resistant to 240℃ saturated salt. Therefore, it is urgent to develop a drilling fluid fluid loss reducer that is resistant to ultra-high temperature and ultra-high pressure saturated salt.

[0003] Patent application CN115850578A discloses a polymer fluid loss reducer with a temperature resistance of 240°C, but a salt resistance of only 4%, and cannot maintain good performance under saturated salt conditions. Patent application CN114989351A discloses a low molecular weight fluid loss reducer with a saturated salt resistance, but the ester monomers therein are easily degraded at high temperatures, and the temperature resistance of the polymer is only 200°C. Patent applications CN114716607A and CN106366243A both disclose novel zwitterionic copolymer fluid loss reducers, in which the cationic groups can enhance the adsorption capacity of the polymer at high temperatures, and the strong hydration groups can enhance the salt resistance of the polymer, but its K resistance is poor. + , Anti-Ca 2+ The performance cannot meet the requirements of deep formations, and the high-temperature and high-pressure filtration performance is poor. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that the water-based drilling fluid fluid loss reducer in the prior art cannot resist ultra-high temperature, ultra-high pressure and saturated salt at the same time, and to provide a strong adsorption hyperbranched fluid loss reducer for 240°C saturated salt water-based drilling fluid and its preparation method and application. The fluid loss reducer provided by the present invention can maintain good performance under 240°C and saturated salt conditions, and is stable for a long time (more than 10 days), which can provide technical support for ultra-deep oil and gas drilling.

[0005] In order to achieve the above object, the present invention provides a fluid loss reducer on one hand, the fluid loss reducer comprising:

[0006] The first structural unit is provided by an anionic hydration enhancing monomer;

[0007] The second structural unit is provided by a cationic positively charged adsorption monomer;

[0008] The third structural unit is provided by the main chain monomer;

[0009] The fourth structural unit is provided by the cyclic monomer;

[0010] The fifth structural unit is provided by a polyether monomer;

[0011] The sixth structural unit is provided by a hyperbranched structural monomer;

[0012] Wherein, the main chain monomer is N,N-dimethylacrylamide and / or N,N-diethylacrylamide, and the weight average molecular weight of the fluid loss reducer is 200,000 to 800,000.

[0013] Preferably, the weight ratio of the first structural unit, the second structural unit, the third structural unit, the fourth structural unit, the fifth structural unit and the sixth structural unit is (10-60):(5-40):(5-40):(2-20):(5-40):1, preferably (20-30):(10-20):(10-20):(5-10):(10-20):1.

[0014] Preferably, the anionic hydration enhancing monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, sodium allyl sulfonate and sodium methacrylic acid sulfonate.

[0015] Preferably, the cationic positively charged adsorption monomer is at least one of dimethylaminopropyl methacrylamide, dimethyldiallylammonium chloride and acryloyloxyethyltrimethylammonium chloride.

[0016] Preferably, the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the weight ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.1-1, preferably 1:0.3-0.5.

[0017] Preferably, the cyclic monomer is at least one of N-vinylpyrrolidone, 1-vinylimidazole, 4-vinylpyridine and 4-acryloylmorpholine.

[0018] Preferably, the polyether monomer is at least one of modified alkylene polyoxyethylene ether, hydroxybutyl polyoxyethylene ether, 4-hydroxybutyl vinyl ether polyoxyethylene ether and ethylene glycol monovinyl polyoxyethylene ether.

[0019] Preferably, the molecular weight of the polyether monomer is 1500-4000.

[0020] Preferably, the structural formula of the hyperbranched structure monomer is as shown in formula (I),

[0021]

[0022] A second aspect of the present invention provides a method for preparing a fluid loss reducer, the method comprising:

[0023] Under an inert atmosphere, an anion hydration enhancing monomer, a cationic positively charged adsorption monomer, a main chain monomer, a cyclic monomer and a polyether monomer are reacted once in the presence of a first initiator;

[0024] The product obtained after the primary reaction is subjected to a secondary reaction with a hyperbranched structure monomer in the presence of a second initiator;

[0025] Wherein, the main chain monomer is N,N-dimethylacrylamide and / or N,N-diethylacrylamide.

[0026] Preferably, the weight ratio of the anion hydration enhancing monomer, the cationic positive adsorption monomer, the main chain monomer, the cyclic monomer, the polyether monomer and the hyperbranched structure monomer is (10-60): (5-40): (5-40): (2-20): (5-40): 1, preferably (20-30): (10-20): (10-20): (5-10): (10-20): 1.

[0027] Preferably, the anionic hydration enhancing monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, sodium allyl sulfonate and sodium methacrylic acid sulfonate.

[0028] Preferably, the cationic positively charged adsorption monomer is at least one of dimethylaminopropyl methacrylamide, dimethyldiallylammonium chloride and acryloyloxyethyltrimethylammonium chloride.

[0029] Preferably, the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the weight ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.1-1, preferably 1:0.3-0.5.

[0030] Preferably, the cyclic monomer is at least one of N-vinylpyrrolidone, 1-vinylimidazole, 4-vinylpyridine and 4-acryloylmorpholine.

[0031] Preferably, the polyether monomer is at least one of modified alkylene polyoxyethylene ether, hydroxybutyl polyoxyethylene ether, 4-hydroxybutyl vinyl ether polyoxyethylene ether and ethylene glycol monovinyl polyoxyethylene ether.

[0032] Preferably, the molecular weight of the polyether monomer is 1500-4000.

[0033] Preferably, the structural formula of the hyperbranched structure monomer is as shown in formula (I),

[0034]

[0035] Preferably, the first initiator is a combination of a persulfate and a reducing agent, and the weight ratio of the persulfate to the reducing agent is 1:0.1-0.5.

[0036] Preferably, the persulfate is at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0037] Preferably, the reducing agent is at least one of sodium bisulfite, ammonium bisulfite and potassium bisulfite.

[0038] Preferably, the second initiator is a combination of azobisisobutyramidine hydrochloride and a reducing agent, and the weight ratio of the perazobisisobutyramidine hydrochloride to the reducing agent is 1:0.1-0.5.

[0039] Preferably, the reducing agent is at least one of sodium bisulfite, ammonium bisulfite and potassium bisulfite.

[0040] Preferably, the temperature of the secondary reaction is 5-25°C higher than the temperature of the primary reaction.

[0041] Preferably, the temperature of the primary reaction is 65-75°C, and the temperature of the secondary reaction is 80-90°C.

[0042] A third aspect of the present invention provides a drilling fluid, which contains the fluid loss reducer described above.

[0043] The fluid loss reducer of the present invention is obtained by copolymerizing anionic hydration enhancing monomers, cationic positively charged adsorption monomers, main chain monomers, cyclic monomers, polyether monomers and hyperbranched structure monomers. When used in water-based drilling fluid, it can maintain good drilling fluid rheology and fluid loss reduction performance at 240° C. and saturated salt conditions, and is stable for a long time. The cationic structure can be strongly adsorbed on the surface of negatively charged clay, and the anionic structure can be strongly adsorbed on the end face of positively charged clay. It is not easy to desorb under ultra-high temperature conditions. The hyperbranched structure monomer enables the polymer to form a three-dimensional broom-shaped hyperbranched polymer. The polyether monomer can react with the hydroxyl group on the clay surface through its own alkyl ether structure to form multiple CO chemical bonds, which are more stable than other chemical bonds, hydrogen bonds, electrostatic effects and other adsorption. The unique three-dimensional broom-shaped hyperbranched structure molecular chain has stronger adsorption capacity than other micro-cross-linked structures, hydrophobic association structures and other molecular chains, and has stronger rigidity and greater steric hindrance. It not only ensures the long-term structural stability of the polymer under ultra-high temperature conditions, but also effectively resists the strong double-layer compression effect of high-valent salt ions on the molecular chain, so that the polymer can efficiently maintain the spatial extension state of the molecular chain under ultra-high temperature and saturated salt conditions, thereby bringing a thicker hydration film, stable performance under ultra-high temperature and ultra-high pressure saturated salt conditions, and effectively reduces the filtration loss.

[0044] As the curtain of exploration and development of 10,000-meter deep wells is opened, the ultra-high temperature saturated salt environment of 10,000-meter deep layers has brought great challenges to drilling fluid loss reducers. The use of the fluid loss reducer of the present invention can directly meet the actual engineering needs of 10,000-meter deep well drilling, and exhibits excellent fluid loss reduction performance under the ultra-high temperature and high mineralization conditions of 240°C saturated salt, and is stable for a long time, providing efficient technical support for 10,000-meter deep well drilling, and filling the gap of 240°C saturated salt resistant fluid loss reducer products. At the same time, the fluid loss reducer of the present invention has good compatibility with other oilfield chemical treatment agents, and can be used as a thickener in fracturing fluid and a fluid loss reducer in cementing fluid. DETAILED DESCRIPTION

[0045] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0046] The fluid loss reducer of the present invention comprises a first structural unit, a second structural unit, a third structural unit, a fourth structural unit, a fifth structural unit and a sixth structural unit, wherein the first structural unit is provided by an anionic hydration enhancing monomer, the second structural unit is provided by a cationic positive adsorption monomer, the third structural unit is provided by a main chain monomer, the fourth structural unit is provided by a cyclic monomer, the fifth structural unit is provided by a polyether monomer, and the sixth structural unit is provided by a hyperbranched structural monomer. According to the fluid loss reducer of the present invention, by combining the six types of structural units, the fluid loss reducer can maintain good drilling fluid rheology and fluid loss performance at 240°C and saturated salt conditions, and is stable for a long time when used in water-based drilling fluid.

[0047] In the fluid loss reducer of the present invention, the weight ratio of the first structural unit, the second structural unit, the third structural unit, the fourth structural unit, the fifth structural unit and the sixth structural unit can be (10-60): (5-40): (5-40): (2-20): (5-40): 1, preferably (12-55): (6-35): (6-35): (3-18): (6-35): 1, more preferably (15-50): (7-30): (7-30): (4-15): (7-30): 1, further preferably (18-40): (8-25): (8-25): (5-12): (8-25): 1, and even more preferably (20-30): (10-20): (10-20): (5-10): (10-20): 1. When the proportions of the six types of structural units in the fluid loss control agent are within the above range (especially the preferred range), the fluid loss control agent has better fluid loss control performance.

[0048] In the present invention, the weight average molecular weight of the fluid loss agent is 200,000 to 800,000, preferably 300,000 to 700,000, and more preferably 350,000 to 650,000. Herein, the weight average molecular weight of the fluid loss agent is obtained by gel permeation chromatography.

[0049] In the present invention, the main chain monomer is N,N-dimethylacrylamide and / or N,N-diethylacrylamide. In a preferred case, the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the weight ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.1-1, preferably 1:0.2-0.8, more preferably 1:0.3-0.7, and further preferably 1:0.3-0.5. In the above preferred case, the fluid loss reducer has better fluid loss reduction performance.

[0050] In the present invention, preferably, the anionic hydration enhancing monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, sodium allyl sulfonate and sodium methacrylic sulfonate. When the anionic hydration enhancing monomer is selected from the above preferred monomer examples, the fluid loss control agent has better fluid loss control performance.

[0051] In the present invention, preferably, the cationic positively charged adsorption monomer is at least one of dimethylaminopropyl methacrylamide, dimethyldiallyl ammonium chloride and acryloyloxyethyl trimethyl ammonium chloride. When the cationic positively charged adsorption monomer is selected from the above preferred monomer examples, the fluid loss reducer has better fluid loss reduction performance.

[0052] In the present invention, preferably, the cyclic monomer is at least one of N-vinylpyrrolidone, 1-vinylimidazole, 4-vinylpyridine and 4-acryloylmorpholine. When the cyclic monomer is selected from the above preferred monomer examples, the fluid loss reducer has better fluid loss reduction performance.

[0053] In the present invention, preferably, the polyether monomer is at least one of modified alkylene polyoxyethylene ether, hydroxybutyl polyoxyethylene ether, 4-hydroxybutyl vinyl ether polyoxyethylene ether and ethylene glycol monovinyl polyoxyethylene ether. When the polyether monomer is selected from the above preferred monomer examples, the fluid loss reducer has better fluid loss reduction performance. The molecular weight of the polyether monomer can be 1000-10000, preferably 1500-6000, more preferably 1500-4000, and further preferably 1800-3000.

[0054] In the present invention, preferably, the structural formula of the hyperbranched structure monomer is as shown in formula (I),

[0055]

[0056] When the hyperbranched structure monomer is selected from the monomers represented by the above formula (I), the fluid loss control agent has significantly better fluid loss control performance.

[0057] In some embodiments, the monomers forming the fluid loss reducer are 2-acrylamido-2-methylpropanesulfonic acid, dimethylaminopropyl methacrylamide, a main chain monomer, a modified alkylene polyoxyethylene ether, 1-vinyl imidazole and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.3-0.5. The fluid loss reducer formed according to this embodiment has significantly higher fluid loss reduction performance.

[0058] In other embodiments, the monomers forming the fluid loss reducer are sodium p-styrene sulfonate, dimethyl diallyl ammonium chloride, a main chain monomer, hydroxybutyl polyoxyethylene ether, 4-acryloyl morpholine and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethyl acrylamide and N,N-diethyl acrylamide, and the ratio of N,N-dimethyl acrylamide to N,N-diethyl acrylamide is 1:0.3-0.5. The fluid loss reducer formed according to this embodiment has significantly higher fluid loss reduction performance.

[0059] In other embodiments, the monomers forming the fluid loss reducer are sodium allyl sulfonate, acryloyloxyethyl trimethyl ammonium chloride, a main chain monomer, 4-hydroxybutyl vinyl ether polyoxyethylene ether, N-vinyl pyrrolidone and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.3-0.5. The fluid loss reducer formed according to this embodiment has significantly higher fluid loss reduction performance.

[0060] In other embodiments, the monomers forming the fluid loss reducer are sodium methacrylic sulfonate, dimethyl diallyl ammonium chloride, a main chain monomer, ethylene glycol monovinyl polyoxyethylene ether, 4-vinyl pyridine and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethyl acrylamide and N,N-diethyl acrylamide, and the ratio of N,N-dimethyl acrylamide to N,N-diethyl acrylamide is 1:0.3-0.5. The fluid loss reducer formed according to this embodiment has significantly higher fluid loss reduction performance.

[0061] The fluid loss reducer of the present invention can be prepared by conventional polymerization methods. In some embodiments, the preparation method of the fluid loss reducer includes:

[0062] Under an inert atmosphere, an anion hydration enhancing monomer, a cationic positively charged adsorption monomer, a main chain monomer, a cyclic monomer and a polyether monomer are reacted once in the presence of a first initiator;

[0063] The product obtained after the primary reaction is subjected to a secondary reaction with a hyperbranched structure monomer in the presence of a second initiator.

[0064] In the method of the present invention, the weight ratio of the anion hydration enhancing monomer, the cationic positive adsorption monomer, the main chain monomer, the cyclic monomer, the polyether monomer and the hyperbranched structure monomer can be (10-60): (5-40): (5-40): (2-20): (5-40): 1, preferably (12-55): (6-35): (6-35): (3-18) : (6-35): 1, more preferably (15-50): (7-30): (7-30): (4-15): (7-30): 1, further preferably (18-40): (8-25): (8-25): (5-12): (8-25): 1, and further preferably (20-30): (10-20): (10-20): (5-10): (10-20): 1. The fluid loss reducer prepared according to the above ratio range (especially the preferred range) has better fluid loss reduction performance.

[0065] In the method of the present invention, the conditions of the primary reaction and the secondary reaction are such that the weight average molecular weight of the prepared fluid loss reducer is 200,000 to 800,000, preferably 300,000 to 700,000, and more preferably 350,000 to 650,000.

[0066] Preferably, the temperature of the secondary reaction is 5-25° C. higher than that of the primary reaction, preferably 8-20° C., more preferably 10-18° C. More preferably, the temperature of the primary reaction is 65-75° C., and the temperature of the secondary reaction is 80-90° C.

[0067] In the method of the present invention, preferably, the duration of the primary reaction is 4-6 hours, and the duration of the secondary reaction is 2-4 hours.

[0068] In the method of the present invention, the main chain monomer is N,N-dimethylacrylamide and / or N,N-diethylacrylamide. In a preferred case, the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the weight ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.1-1, preferably 1:0.2-0.8, more preferably 1:0.3-0.7, and further preferably 1:0.3-0.5. In the above preferred case, the prepared fluid loss reducer has better fluid loss reduction performance.

[0069] In the method of the present invention, preferably, the anionic hydration enhancing monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, sodium allyl sulfonate and sodium methacrylic sulfonate. When the anionic hydration enhancing monomer is selected from the above preferred monomer examples, the prepared fluid loss control agent has better fluid loss control performance.

[0070] In the method of the present invention, preferably, the cationic positively charged adsorption monomer is at least one of dimethylaminopropyl methacrylamide, dimethyldiallyl ammonium chloride and acryloyloxyethyl trimethyl ammonium chloride. When the cationic positively charged adsorption monomer is selected from the above preferred monomer examples, the prepared fluid loss reducer has better fluid loss reduction performance.

[0071] In the method of the present invention, preferably, the cyclic monomer is at least one of N-vinylpyrrolidone, 1-vinylimidazole, 4-vinylpyridine and 4-acryloylmorpholine. When the cyclic monomer is selected from the above preferred monomer examples, the prepared fluid loss reducer has better fluid loss reduction performance.

[0072] In the method of the present invention, preferably, the polyether monomer is at least one of modified alkylene polyoxyethylene ether, hydroxybutyl polyoxyethylene ether, 4-hydroxybutyl vinyl ether polyoxyethylene ether and ethylene glycol monovinyl polyoxyethylene ether. When the polyether monomer is selected from the above preferred monomer examples, the prepared fluid loss reducer has better fluid loss reduction performance. The molecular weight of the polyether monomer can be 1000-10000, preferably 1500-6000, more preferably 1500-4000, and further preferably 1800-3000.

[0073] In the present invention, preferably, the structural formula of the hyperbranched structure monomer is as shown in formula (I),

[0074]

[0075] When the hyperbranched structure monomer is selected from the monomers represented by the above formula (I), the prepared fluid loss control agent has significantly better fluid loss control performance.

[0076] In the present invention, the hyperbranched structure monomer represented by formula (I) can be obtained by esterification reaction of N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine and maleic anhydride, and the reaction formula is shown below.

[0077]

[0078] In some embodiments, the monomers used to prepare the fluid loss reducer are 2-acrylamido-2-methylpropanesulfonic acid, dimethylaminopropyl methacrylamide, a main chain monomer, a modified alkylene polyoxyethylene ether, 1-vinyl imidazole and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.3-0.5. The fluid loss reducer prepared according to this embodiment has significantly higher fluid loss reduction performance.

[0079] In other embodiments, the monomers used to prepare the fluid loss reducer are sodium p-styrene sulfonate, dimethyl diallyl ammonium chloride, a main chain monomer, hydroxybutyl polyoxyethylene ether, 4-acryloyl morpholine and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethyl acrylamide and N,N-diethyl acrylamide, and the ratio of N,N-dimethyl acrylamide to N,N-diethyl acrylamide is 1:0.3-0.5. The fluid loss reducer prepared according to this embodiment has significantly higher fluid loss reduction performance.

[0080] In other embodiments, the monomers used to prepare the fluid loss reducer are sodium allyl sulfonate, acryloyloxyethyl trimethyl ammonium chloride, a main chain monomer, 4-hydroxybutyl vinyl ether polyoxyethylene ether, N-vinyl pyrrolidone and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.3-0.5. The fluid loss reducer prepared according to this embodiment has significantly higher fluid loss reduction performance.

[0081] In other embodiments, the monomers used to prepare the fluid loss reducer are sodium methacrylic acid sulfonate, dimethyl diallyl ammonium chloride, a main chain monomer, ethylene glycol monovinyl polyoxyethylene ether, 4-vinyl pyridine and a monomer represented by formula (I), wherein the main chain monomer is a combination of N,N-dimethyl acrylamide and N,N-diethyl acrylamide, and the ratio of N,N-dimethyl acrylamide to N,N-diethyl acrylamide is 1:0.3-0.5. The fluid loss reducer prepared according to this embodiment has significantly higher fluid loss reduction performance.

[0082] In the method of the present invention, the primary reaction is carried out in the presence of a first initiator, and the first initiator is preferably a combination of a persulfate and a reducing agent. More preferably, in the first initiator, the weight ratio of the persulfate to the reducing agent is 1:0.1-0.5, preferably 1:0.2-0.4, preferably 1:0.2-0.3. The persulfate may be at least one of ammonium persulfate, potassium persulfate and sodium persulfate. The reducing agent may be at least one of sodium bisulfite, ammonium bisulfite and potassium bisulfite.

[0083] In the method of the present invention, the secondary reaction is carried out in the presence of a second initiator, and the second initiator is preferably a combination of azobisisobutyramidine hydrochloride and a reducing agent. More preferably, the weight ratio of the perazobisisobutyramidine hydrochloride to the reducing agent is 1:0.1-0.5, preferably 1:0.2-0.4, preferably 1:0.2-0.3. Wherein, the reducing agent is at least one of sodium bisulfite, ammonium bisulfite and potassium bisulfite.

[0084] In a more preferred embodiment, the preparation method of the fluid loss reducer comprises:

[0085] (1) Dispersing the anionic hydration enhancing monomer in water, if the solution is acidic, using an alkaline solution (such as NaOH solution) to adjust the pH value to 5-7;

[0086] (2) adding the main chain monomer, cationic positive adsorption monomer, polyether monomer and cyclic monomer in sequence, stirring and mixing, then heating to 65-75° C., introducing nitrogen (or inert gas) for 10-30 minutes, adding the first initiator, and reacting at a constant temperature for 4-6 hours;

[0087] (3) Continue to raise the temperature to 80-90° C., add the hyperbranched structure monomer and the second initiator, and continue the reaction for 2-4 hours;

[0088] (4) After the reaction is completed, the reaction product is washed with acetone for 3-5 times, dried at 80-100° C. for 8-12 hours, and then crushed to obtain a white or light yellow powder, which is the fluid loss reducer suitable for use as a water-based drilling fluid fluid loss reducer of the present invention.

[0089] In the method of the present invention, the weight ratio of water to the hyperbranched structure monomer can be 60-400:1, preferably 80-200:1.

[0090] In the method of the present invention, the weight ratio of the first initiator to the hyperbranched structure monomer can be 0.05-0.6:1, preferably 0.1-0.5:1.

[0091] In the method of the present invention, the weight ratio of the second initiator to the hyperbranched structure monomer can be 0.025-0.2:1, preferably 0.05-0.1:1.

[0092] The drilling fluid of the present invention contains a fluid loss reducer, and the fluid loss reducer is the fluid loss reducer provided by the present invention. The drilling fluid of the present invention can maintain good drilling fluid rheology and fluid loss reduction performance under ultra-high temperature (such as 240° C.) and saturated salt conditions, and is stable for a long time.

[0093] The following examples further illustrate the highly adsorbent hyperbranched fluid loss reducer for 240°C saturated salt water-based drilling fluid and its preparation method and application. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0094] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0095] The 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, sodium allyl sulfonate, sodium methacrylic sulfonate, dimethylaminopropyl methacrylamide, dimethyldiallylammonium chloride, acryloyloxyethyltrimethylammonium chloride, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-vinylpyrrolidone, 1-vinylimidazole, 4-vinylpyridine, 4-acryloylmorpholine, N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine, maleic anhydride, N,N,N',N'-tetramethylethylenediamine, ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride and sodium bisulfite used in the following examples and comparative examples were all purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0096] The hyperbranched structure monomer TME was prepared by esterification reaction of analytically pure N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine and maleic anhydride.

[0097] Modified alkylene polyoxyethylene ether (PCB7230-1800), hydroxybutyl polyoxyethylene ether (PSV7630-2000), 4-hydroxybutyl vinyl ether polyoxyethylene ether (VPEG-1800), and ethylene glycol monovinyl polyoxyethylene ether (EPEG-2000) were purchased from Wuhan Shanjiang Chemical Technology Co., Ltd. The number after “-” represents the molecular weight.

[0098] Sodium bentonite was purchased from Shandong Huawei Bentonite Co., Ltd.;

[0099] Fluid loss reducer DSP 1. Sulfonated asphalt FF-1, amino polyol AP-1, sulfonated methyl phenolic resin SMP-2, sulfonated lignite SMC, sulfonated lignite phenolic resin SPNH, lubricant RH-3, and plugging agent NP-1 were purchased from Shandong Deshunyuan Petroleum Technology Co., Ltd.;

[0100] High temperature resistant cementing fluid loss reducer HT-1 was purchased from Chengdu Chuanfeng Chemical Engineering Co., Ltd.;

[0101] The weight average molecular weight of the fluid loss reducer in the examples is obtained by gel permeation chromatography.

[0102] Example 1

[0103] The main chain monomer used in this embodiment is a mixture of N,N-dimethylacrylamide and N,N-diethylacrylamide in a mass ratio of 1:0.4.

[0104] (1) 20 g of 2-acrylamido-2-methylpropanesulfonic acid was added to 130 g of water, stirred until fully dispersed, and the pH value was adjusted to 6 using a 50 wt% NaOH solution;

[0105] (2) Add 10 g of main chain monomer, 15 g of dimethylaminopropyl methacrylamide, 15 g of polyether monomer PCB7230-1800 and 8 g of 1-vinyl imidazole in sequence, stir until fully dispersed, and transfer the liquid to a three-necked flask;

[0106] (3) The temperature was raised to 65°C and nitrogen was passed through for 20 min. Then, 0.25 g of ammonium persulfate and 0.05 g of sodium bisulfite were added to initiate the reaction. The reaction was continued at a constant temperature for 5 h.

[0107] (4) Continue to raise the temperature to 85° C., connect a condenser to the flask, add 0.8 g of hyperbranched structure monomer TME, 0.05 g of azobisisobutyramidine hydrochloride, and 0.02 g of sodium bisulfite, and continue the reaction for 3 h;

[0108] (5) After the reaction, the reaction product was washed with acetone three times, dried in an oven at 90° C. for 10 h, and then crushed. The obtained light yellow powder was the filtrate reducer A1 of the present invention, and its weight average molecular weight was 490,000.

[0109] Example 2

[0110] The main chain monomer used in this embodiment is a mixture of N,N-dimethylacrylamide and N,N-diethylacrylamide in a mass ratio of 1:0.3.

[0111] (1) Add 30 g of sodium p-styrene sulfonate to 180 g of water and stir until fully dispersed;

[0112] (2) Add 15 g of main chain monomer, 20 g of dimethyldiallylammonium chloride, 20 g of polyether monomer PSV7630-2000 and 9 g of 4-acryloylmorpholine in sequence, stir until fully dispersed, and transfer the liquid to a three-necked flask;

[0113] (3) The temperature was raised to 70°C and nitrogen was passed through for 20 min. Then, 0.3 g of ammonium persulfate and 0.1 g of sodium bisulfite were added to initiate the reaction. The reaction was continued at a constant temperature for 6 h.

[0114] (4) Continue to raise the temperature to 90° C., connect a condenser to the flask, add 1 g of hyperbranched structure monomer TME, 0.06 g of azobisisobutyramidine hydrochloride, and 0.02 g of sodium bisulfite, and continue the reaction for 4 h;

[0115] (5) After the reaction, the reaction product was washed with acetone three times, dried in an oven at 90° C. for 10 h, and then crushed. The obtained white powder was the filtrate reducer A2 of the present invention, and its weight average molecular weight was 410,000.

[0116] Example 3

[0117] The main chain monomer used in this embodiment is a mixture of N,N-dimethylacrylamide and N,N-diethylacrylamide in a mass ratio of 1:0.4.

[0118] (1) Add 30 g of sodium allyl sulfonate to 160 g of water and stir until fully dispersed;

[0119] (2) Add 20 g of main chain monomer, 10 g of acryloyloxyethyl trimethyl ammonium chloride, 15 g of polyether monomer VPEG-1800 and 6 g of N-vinyl pyrrolidone in sequence, stir until fully dispersed, and transfer the liquid to a three-necked flask;

[0120] (3) The temperature was raised to 70°C and nitrogen was passed through for 20 min. Then, 0.25 g of potassium persulfate and 0.15 g of sodium bisulfite were added to initiate the reaction. The reaction was continued at a constant temperature for 5 h.

[0121] (4) Continue to raise the temperature to 80° C., connect a condenser to the flask, add 2 g of hyperbranched structure monomer TME, 0.08 g of azobisisobutyramidine hydrochloride, and 0.02 g of sodium bisulfite, and continue the reaction for 2 h;

[0122] (5) After the reaction, the reaction product was washed with acetone three times, dried in an oven at 90° C. for 10 h, and then crushed. The obtained white powder was the filtrate reducer A3 of the present invention, and its weight average molecular weight was 580,000.

[0123] Example 4

[0124] The main chain monomer used in this embodiment is a mixture of N,N-dimethylacrylamide and N,N-diethylacrylamide in a mass ratio of 1:0.5.

[0125] (1) Add 25 g of sodium methacrylate sulfonate to 190 g of water and stir until fully dispersed;

[0126] (2) Add 10 g of main chain monomer, 10 g of dimethyldiallylammonium chloride, 10 g of dimethylaminopropyl methacrylamide, 20 g of polyether monomer EPEG-2000 and 8 g of 4-vinylpyridine in sequence, stir until fully dispersed, and transfer the liquid to a three-necked flask;

[0127] (3) The temperature was raised to 75°C and nitrogen was passed through for 20 min. Then, 0.35 g of potassium persulfate and 0.15 g of sodium bisulfite were added to initiate the reaction. The reaction was continued at a constant temperature for 6 h.

[0128] (4) Continue to raise the temperature to 85° C., connect a condenser to the flask, add 1 g of hyperbranched structure monomer TME, 0.04 g of azobisisobutyramidine hydrochloride, and 0.01 g of sodium bisulfite, and continue the reaction for 2 h;

[0129] (5) After the reaction, the reaction product was washed with acetone three times, dried in an oven at 90° C. for 10 h, and then crushed. The obtained light yellow powder was the filtrate reducer A4 of the present invention, and its weight average molecular weight was 360,000.

[0130] Comparative Example 1

[0131] A fluid loss control agent was prepared according to the method of Example 1, except that no anionic hydration enhancing monomer (ie, 2-acrylamido-2-methylpropanesulfonic acid) was added, to obtain a fluid loss control agent D1.

[0132] Comparative Example 2

[0133] A fluid loss control agent was prepared according to the method of Example 1, except that the cationic positively charged adsorption monomer (ie, dimethylaminopropyl methacrylamide) was not added, to obtain a fluid loss control agent D2.

[0134] Comparative Example 3

[0135] A fluid loss control agent was prepared according to the method of Example 1, except that the polyether monomer PCB7230-1800 was not added, to obtain a fluid loss control agent D3.

[0136] Comparative Example 4

[0137] A fluid loss control agent was prepared according to the method of Example 1, except that the cyclic monomer (ie, 1-vinylimidazole) was not added, to obtain a fluid loss control agent D4.

[0138] Comparative Example 5

[0139] A fluid loss control agent was prepared according to the method of Example 1, except that no main chain monomer was added, to obtain a fluid loss control agent D5.

[0140] Comparative Example 6

[0141] A fluid loss control agent was prepared according to the method of Example 1, except that the hyperbranched structure monomer TME was not added, to obtain a fluid loss control agent D6.

[0142] Comparative Example 7

[0143] A fluid loss reducer was prepared according to the method of Example 1, except that the hyperbranched structure monomer TME in step (4) was replaced by an equal mass of N,N,N',N'-tetramethylethylenediamine to obtain a fluid loss reducer D7.

[0144] Comparative Example 8

[0145] A fluid loss reducer was prepared according to the method of Example 1, except that sodium bisulfite was not added in steps (3) and (4), to obtain a fluid loss reducer D8.

[0146] Comparative Example 9

[0147] A fluid loss reducer was prepared according to the method of Example 1, except that the temperature was not increased in step (4) and the reaction temperature was maintained at 65° C., to obtain a fluid loss reducer D9.

[0148] Application Example 1

[0149] (1) Preparation of drilling fluid F1: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of fluid loss reducer A1 was added and stirred for 20 minutes to obtain drilling fluid F1.

[0150] (2) Preparation of drilling fluid F2: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of fluid loss reducer A2 was added and stirred for 20 minutes to obtain drilling fluid F2.

[0151] (3) Preparation of drilling fluid F3: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of fluid loss reducer A3 was added and stirred for 20 minutes to obtain drilling fluid F3.

[0152] (4) Preparation of drilling fluid F4: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of fluid loss reducer A4 was added and stirred for 20 minutes to obtain drilling fluid F4.

[0153] Application Comparative Example 1

[0154] (1) Preparation of drilling fluid DF0: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of a commercially available fluid loss reducer DSP-1 was added and stirred for 20 minutes to obtain drilling fluid DF0.

[0155] (2) Preparation of drilling fluid DF1: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D1 was added and stirred for 20 minutes to obtain drilling fluid DF1.

[0156] (3) Preparation of drilling fluid DF2: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D2 was added and stirred for 20 minutes to obtain drilling fluid DF2.

[0157] (4) Preparation of drilling fluid DF3: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D3 was added and stirred for 20 minutes to obtain drilling fluid DF3.

[0158] (5) Preparation of drilling fluid DF4: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D4 was added and stirred for 20 minutes to obtain drilling fluid DF4.

[0159] (6) Preparation of drilling fluid DF5: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D5 was added and stirred for 20 minutes to obtain drilling fluid DF5.

[0160] (7) Preparation of drilling fluid DF6: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D6 was added and stirred for 20 minutes to obtain drilling fluid DF6.

[0161] (8) Preparation of drilling fluid DF7: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D7 was added and stirred for 20 minutes to obtain drilling fluid DF7.

[0162] (9) Preparation of drilling fluid DF8: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D8 was added and stirred for 20 minutes to obtain drilling fluid DF8.

[0163] (10) Preparation of drilling fluid DF9: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer D9 was added and stirred for 20 minutes to obtain drilling fluid DF9.

[0164] Application Example 2

[0165] (1) Preparation of drilling fluid T1: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer A1, 3 parts by weight of sulfonated asphalt FF-1 and 3 parts by weight of lubricant RH-3 were added, and stirred for 20 minutes to obtain drilling fluid T1.

[0166] (2) Preparation of drilling fluid T2: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer A1, 2 parts by weight of sulfomethylphenolic resin SMP-2, 2 parts by weight of sulfonated lignite SMC and 1 part by weight of sulfonated lignite phenolic resin SPNH were added, and stirred for 20 minutes to obtain drilling fluid T2.

[0167] (3) Preparation of drilling fluid T3: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer A1, 3 parts by weight of plugging agent NP-1 and 2 parts by weight of amino polyol AP-1 were added, and stirred for 20 minutes to obtain drilling fluid T3.

[0168] (4) Preparation of drilling fluid T4: 4 parts by weight of sodium bentonite was added to 100 parts by weight of water, stirred for 20 minutes, and then allowed to stand at room temperature for 24 hours. After stirring for another 20 minutes, 3 parts by weight of filtrate reducer A1, 3 parts by weight of sulfonated asphalt FF-1, 3 parts by weight of lubricant RH-3, 3 parts by weight of plugging agent NP-1 and 2 parts by weight of amino polyol AP-1 were added, and stirred for 20 minutes to obtain drilling fluid T4.

[0169] Application Comparative Example 2

[0170] The fluid loss reducer A1 used in the process of preparing drilling fluids T1-T4 in Application Example 2 was replaced with an equal weight of fluid loss reducer DSP-1 to prepare comparative drilling fluids DT1-DT4, respectively.

[0171] Test Example 1

[0172] Take 400mL of drilling fluid F1-F4 and DF0-DF9, stir at 8000rpm for 20min, then add 36wt% NaCl, 5wt% CaCl2, 10wt% KCl and composite salt (15wt% NaCl+7wt% KCl+5wt% CaCl2), stir for 20min, put into stainless steel aging tank, and roll at 240℃ for 16 hours. After aging, cool to room temperature and take out, stir at 8000rpm for 20min. According to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 1: Water-based Drilling Fluids", the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear force (YP, Pa), API filtration loss FL of the above drilling fluids were measured. API And high temperature and high pressure filtration loss FL HTHP240℃ , the results are shown in Tables 1-4.

[0173] Table 1: Drilling fluid performance test (36wt% NaCl)

[0174] Drilling Fluid AV,mPa.s PV,mPa.s YP,Pa <![CDATA[FL API ,mL]]> <![CDATA[FL HTHP 240℃ ,mL]]> Fl 34 30 4 1.4 14.8 F2 32.5 29 3.5 1.8 15.2 F3 36 32.5 3.5 1.6 15.0 F4 31 28 3 1.8 15.6 DF0 17 16.5 0.5 14.8 89.6 DF 20 18.5 1.5 9.4 56.4 DF2 29 26 3 6.0 32.5 DF3 25 23 2 7.2 44.8 DF4 22 21 1 6.8 46.8 DF5 26 24 2 6.2 43.8 DF6 30 27 3 5.4 29.6 DF7 31 27 4 4.4 30.8 DF8 28 26 2 6.2 36.6 DF9 26 25 1 7.4 41.6

[0175] Table 2: Drilling fluid performance test (5wt% CaCl2)

[0176] Drilling Fluid AV,mPa.s PV,mPa.s YP,Pa <![CDATA[FL API ,mL]]> <![CDATA[FL HTHP 240℃ ,mL]]> Fl 39 33 6 1.6 16.2 F2 37 31.5 5.5 1.8 17.4 F3 41.5 34 6.5 2.0 18.2 F4 36 31 5 1.8 16.6 DF0 19 18 1 16.5 96.8 DF 20 19 1 10.2 63.2 DF2 30 27 3 7.2 34.8 DF3 28 26.5 1.5 7.6 49.8 DF4 23 21 2 8.4 52.3 DF5 27 24.5 2.5 7.8 51.4 DF6 32 29.5 2.5 6.2 31.8 DF7 35 32 3 5.6 37.2 DF8 30 27 3 7.4 40.3 DF9 28 26.5 1.5 7.8 47.8

[0177] Table 3: Drilling fluid performance test (10wt% KCl)

[0178] Drilling Fluid AV,mPa.s PV,mPa.s YP,Pa <![CDATA[FL API ,mL]]> <![CDATA[FL HTHP 240℃ ,mL]]> Fl 40 34.5 5.5 1.2 14.2 F2 36 32 4 1.4 14.4 F3 37 33 4 1.6 15.8 F4 33.5 29 4.5 1.2 14.6 DF0 20 17.5 2.5 10.8 69.6 DF 23 20 3 8.6 45.6 DF2 31 27.5 3.5 5.2 30.4 DF3 28 25 3 6.4 39.2 DF4 25 23 2 5.6 38.8 DF5 27 25 2 5.2 37.6 DF6 31 28 3 4.6 27.4 DF7 34.5 30.5 4 4.2 28.6 DF8 31 28.5 2.5 5.8 32.8 DF9 29 27.5 1.5 6.8 36.4

[0179] Table 4: Drilling fluid performance test (compound salt)

[0180] Drilling Fluid AV,mPa.s PV,mPa.s YP,Pa <![CDATA[FL API ,mL]]> <![CDATA[FL HTHP 240℃ ,mL]]> Fl 39 34 5 1.4 16.8 F2 35 30.5 4.5 1.6 17.2 F3 38 33 5 1.8 17.6 F4 32 28 4 1.8 17.4 DF0 19 17 2 14.6 78.2 DF 21 18 3 9.2 47.6 DF2 32 28 4 5.6 34.2 DF3 27 24.5 2.5 6.6 43.4 DF4 24 22 2 6.8 40.6 DF5 26 23.5 2.5 6.2 38.8 DF6 30 27.5 2.5 5.4 31.8 DF7 35 31 4 4.8 31.2 DF8 30 27 3 6.4 38.2 DF9 28 26.5 1.5 7.4 39.6

[0181] It can be seen from the data in Tables 1-4 that the fluid loss reducer of the present invention has a significantly better fluid loss reduction effect. The fluid loss reducer of the present invention can play a good fluid loss reduction effect under the conditions of 240°C high temperature, 36wt% NaCl, 5wt% CaCl2 and 10wt% KCl, and can meet the needs of ultra-deep and ultra-deep drilling.

[0182] Test Example 2

[0183] Take 400mL of drilling fluid F1-F4 respectively, stir at 8000rpm for 20min, and then roll at 240℃ for 1 day, 3 days, 5 days, 7 days and 10 days. After aging, cool to room temperature, take out, and stir at 8000rpm for 20min. According to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 1: Water-based Drilling Fluids", the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear force (YP, Pa), API filtration loss FL of the above drilling fluids were measured. API And high temperature and high pressure filtration loss FL HTHP 240℃ , the results are shown in Table 5.

[0184] Table 5: Drilling fluid performance test (long-term aging)

[0185]

[0186] From the data in Table 5, it can be seen that the viscosity of the drilling fluid to which the fluid loss reducer of the present invention is added decreases after long-term aging, but it still has good rheological properties overall and still maintains low fluid loss. After aging at 240°C for 10 days, the high-temperature and high-pressure fluid loss of the drilling fluid is less than 25 mL, which reflects the ultra-long-term stability of the fluid loss reducer of the present invention, and can play a role in reducing fluid loss for a long time in field applications.

[0187] Test Example 3

[0188] Take 400mL of drilling fluid T1-T4 and DT1-DT4 respectively, stir at 8000rpm for 20min, put them into stainless steel aging tank, and roll at constant temperature at 240℃ for 16 hours. After aging, cool to room temperature, take out, and stir at 8000rpm for 20min. According to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 1: Water-based Drilling Fluids", the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear force (YP, Pa), API filtration loss FL of the above drilling fluids were measured. API And high temperature and high pressure filtration loss FL HTHP 240℃ , the results are shown in Table 6.

[0189] Table 6: Drilling fluid performance test

[0190] Drilling Fluid AV,mPa.s PV,mPa.s YP,Pa <![CDATA[FL API ,mL]]> <![CDATA[FL HTHP 240℃ ,mL]]> Tl 42 36 6 0.6 13.2 T2 48 41.5 6.5 0.2 13.6 T3 38.5 34 4 0.4 13.0 T4 45 39 6 0.2 11.2 DT1 28.5 26 2.5 8.8 68.2 DT2 30 29 1 17.6 97.4 DT3 28 26.5 1.5 14.2 77.4 DT4 29 26 3 7.4 59.4

[0191] It can be seen from the data in Table 6 that the fluid loss reducer of the present invention has good compatibility with common commercial drilling fluid treatment agents such as sulfonated asphalt FF-1, lubricant RH-3, plugging agent NP-1, etc., and can synergize when used in combination, which provides convenience for configuring the drilling fluid system and reflects the good compatibility and universality of the fluid loss reducer. In addition to its own performance being weaker than that of the fluid loss reducer of the present invention, the commercially available fluid loss reducer DSP-1 also has poor compatibility with some treatment agents, and its performance is further reduced when used together.

[0192] Test Example 4

[0193] The effect of the fluid loss reducer of the present invention as a fluid loss reducer for cementing fluid was tested.

[0194] According to the relevant provisions of the petroleum and natural gas industry standard SY / T5504.2-2013 "Evaluation Method for Oil Well Cement Admixtures Part 2: Fluid Loss Reducers" and the national standard GB / T19139-2012 "Test Methods for Oil Well Cement", the performance of the fluid loss reducers A1-A4 prepared in Examples 1-4 and the commercially available high temperature resistant cementing fluid loss reducer HT-1 were evaluated, and the initial consistency, API water loss and free liquid were measured at a test temperature of 240°C and a dosage of 5wt% in the cement slurry. The results are shown in Table 7.

[0195] Table 7: Cementing fluid loss test

[0196] sample Initial consistency, Bc API water loss, mL Free liquid, % A1 30 24 0 A2 28 22 0 A3 31 26 0 A4 34 25 0 Commercially available HT-1 46 104 0.7

[0197] It can be seen from the data in Table 7 that the fluid loss reducer of the present invention can also play a good effect when used as a cementing fluid fluid loss reducer. Under ultra-high temperature conditions of 240°C, the cementing cement can maintain a low initial consistency, the API water loss is less than 26 mL, and no free liquid is precipitated. The performance is significantly better than the commercially available high temperature resistant cementing fluid loss reducer HT-1.

[0198] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A fluid loss reducer, characterized in that: The fluid loss additive includes: The first structural unit is provided by an anionic hydration enhancing monomer; The second structural unit is provided by a cationic positively charged adsorption monomer; The third structural unit is provided by the main chain monomer; The fourth structural unit is provided by the cyclic monomer; The fifth structural unit is provided by a polyether monomer; The sixth structural unit is provided by a hyperbranched structural monomer; Wherein, the main chain monomer is N,N-dimethylacrylamide and / or N,N-diethylacrylamide, and the weight average molecular weight of the fluid loss reducer is 200,000 to 800,000.

2. The fluid loss reducer according to claim 1, characterized in that: The weight ratio of the first structural unit, the second structural unit, the third structural unit, the fourth structural unit, the fifth structural unit and the sixth structural unit is (10-60):(5-40):(5-40):(2-20):(5-40):1, preferably (20-30):(10-20):(10-20):(5-10):(10-20):

1.

3. The fluid loss reducer according to claim 1 or 2, characterized in that: The anionic hydration enhancing monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, sodium allyl sulfonate and sodium methacrylic sulfonate.

4. The fluid loss reducer according to claim 1 or 2, characterized in that: The cationic positive adsorption monomer is at least one of dimethylaminopropyl methacrylamide, dimethyldiallyl ammonium chloride and acryloyloxyethyl trimethyl ammonium chloride.

5. The fluid loss reducer according to claim 1 or 2, characterized in that: The main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the weight ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.1-1, preferably 1:0.3-0.

5.

6. The fluid loss reducer according to claim 1 or 2, characterized in that: The cyclic monomer is at least one of N-vinyl pyrrolidone, 1-vinylimidazole, 4-vinyl pyridine and 4-acryloylmorpholine.

7. The fluid loss reducer according to claim 1 or 2, characterized in that: The polyether monomer is at least one of modified alkylene polyoxyethylene ether, hydroxybutyl polyoxyethylene ether, 4-hydroxybutyl vinyl ether polyoxyethylene ether and ethylene glycol monovinyl polyoxyethylene ether; Preferably, the molecular weight of the polyether monomer is 1500-4000.

8. The fluid loss reducer according to claim 1 or 2, characterized in that: The structural formula of the hyperbranched structure monomer is shown in formula (I), 9. A method for preparing a fluid loss reducer, characterized in that: The method includes: Under an inert atmosphere, an anion hydration enhancing monomer, a cationic positively charged adsorption monomer, a main chain monomer, a cyclic monomer and a polyether monomer are reacted once in the presence of a first initiator; The product obtained after the primary reaction is subjected to a secondary reaction with a hyperbranched structure monomer in the presence of a second initiator; Wherein, the main chain monomer is N,N-dimethylacrylamide and / or N,N-diethylacrylamide.

10. The method according to claim 9, characterized in that The weight ratio of the anionic hydration enhancing monomer, the cationic positive adsorption monomer, the main chain monomer, the cyclic monomer, the polyether monomer and the hyperbranched structure monomer is (10-60): (5-40): (5-40): (2-20): (5-40): 1, preferably (20-30): (10-20): (10-20): (5-10): (10-20):

1.

11. The method according to claim 9 or 10, characterized in that: The anionic hydration enhancing monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, sodium allyl sulfonate and sodium methacrylic sulfonate.

12. The method according to claim 9 or 10, characterized in that The cationic positive adsorption monomer is at least one of dimethylaminopropyl methacrylamide, dimethyldiallyl ammonium chloride and acryloyloxyethyl trimethyl ammonium chloride.

13. The method according to claim 9 or 10, characterized in that: The main chain monomer is a combination of N,N-dimethylacrylamide and N,N-diethylacrylamide, and the weight ratio of N,N-dimethylacrylamide to N,N-diethylacrylamide is 1:0.1-1, preferably 1:0.3-0.

5.

14. The method according to claim 9 or 10, characterized in that The cyclic monomer is at least one of N-vinyl pyrrolidone, 1-vinylimidazole, 4-vinyl pyridine and 4-acryloylmorpholine.

15. The method according to claim 9 or 10, characterized in that The polyether monomer is at least one of modified alkylene polyoxyethylene ether, hydroxybutyl polyoxyethylene ether, 4-hydroxybutyl vinyl ether polyoxyethylene ether and ethylene glycol monovinyl polyoxyethylene ether; Preferably, the molecular weight of the polyether monomer is 1500-4000.

16. The method according to claim 9 or 10, characterized in that The structural formula of the hyperbranched structure monomer is shown in formula (I), 17. The method according to claim 9 or 10, characterized in that The first initiator is a combination of a persulfate and a reducing agent, and the weight ratio of the persulfate to the reducing agent is 1:0.1-0.5; Preferably, the persulfate is at least one of ammonium persulfate, potassium persulfate and sodium persulfate; Preferably, the reducing agent is at least one of sodium bisulfite, ammonium bisulfite and potassium bisulfite.

18. The method according to claim 9 or 10, characterized in that The second initiator is a combination of azobisisobutyramidine hydrochloride and a reducing agent, and the weight ratio of the perazobisisobutyramidine hydrochloride to the reducing agent is 1:0.1-0.5; Preferably, the reducing agent is at least one of sodium bisulfite, ammonium bisulfite and potassium bisulfite.

19. The method according to claim 9 or 10, characterized in that The temperature of the secondary reaction is 5-25°C higher than the temperature of the primary reaction; Preferably, the temperature of the primary reaction is 65-75°C, and the temperature of the secondary reaction is 80-90°C.

20. A drilling fluid, characterized in that: The drilling fluid contains the fluid loss reducer according to any one of claims 1 to 8.

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