Salt-responsive temperature-resistant salt-resistant tackifying filtrate reducer for water-based drilling fluid as well as preparation method and application of tackifying filtrate reducer

Abstract

The invention provides a salt-responsive temperature-resistant salt-resistant water-based drilling fluid tackifying filtrate reducer as well as a preparation method and application thereof, and belongs to the technical field of drilling. The tackifying filtrate reducer is prepared from the following raw materials in parts by mass: 30 to 50 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 20 to 40 parts of (3-(methacrylamido) propyl) dimethyl (3-thiopropyl) ammonium hydroxide inner salt, 35 to 55 parts of N, N-dimethylacrylamide, 10 to 25 parts of 4-vinylpyridine, 300 to 500 parts of water and 1 to 5 parts of an initiator. According to the filtrate reducer, cations and anions are concentrated on one monomer molecule, so that the synthesized product contains the cations and the anions with the same charge number, has good adsorption capacity and salt response characteristics, is compatible with salt essentially, can effectively resist high temperature and high salt, and can be recycled. And the viscosity-increasing and filtrate-reducing agent has good viscosity-increasing and filtrate-reducing effects on the drilling fluid.

Description

Technical Field

[0001] The invention relates to a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer, a preparation method and application thereof, and belongs to the technical field of drilling. Background Art

[0002] As oil and gas exploration progresses toward deep and ultra-deep wells, the bottomhole faces complex conditions of ultra-high temperature, ultra-high pressure, ultra-high salinity, and ultra-high stress, posing severe challenges to the performance and stability of drilling fluids. As one of the core treatment agents in drilling fluids, drilling fluid loss reducers must possess enhanced temperature and salt tolerance to maintain drilling fluid stability. However, traditional polymer-based fluid loss reducers have significant limitations. Most acrylamide-based polymers are susceptible to molecular chain breakage or desorption at high temperatures, resulting in ineffective control of drilling fluid rheology and fluid loss. Furthermore, existing polymer-based fluid loss reducers rely on the charge adsorption of polyelectrolytes on the molecular chain. However, in high-salinity environments, charge shielding effects cause the molecular chains to curl, resulting in a sharp decrease in fluid dynamics volume, poor rheology, and a sharp increase in fluid loss. Most high-performance products, such as hyperbranched polymers and 2-acrylamide-2-methylpropanesulfonic acid copolymers, focus solely on fluid loss control, ignoring the deterioration of drilling fluid rheological properties under high-temperature and high-salinity conditions.

[0003] To address these challenges, there is an urgent need to develop a viscosifying and fluid loss reducer that combines intelligent responsiveness, high efficiency, stability, and cost-effectiveness. While existing zwitterionic polymers have been explored for salt tolerance, their temperature tolerance is limited and they lack a mechanism for synergistically regulating both temperature and salinity. Furthermore, while humic acid-grafted materials are relatively low-cost, their lack of high-temperature stability makes them difficult to meet the demands of ultra-deep wells.

[0004] For example, Chinese patent document CN120020157A discloses a fluid loss reducer for ultra-high temperature resistant water-based drilling fluids, as well as its preparation method and application. The fluid loss reducer is obtained by copolymerization of unsaturated monomers. The molecular structure of the fluid loss reducer features a C-C bond as the main chain, and side chains comprise rigid cyclic functional groups, highly adsorbable amide groups, and highly hydrophilic sulfonic acid groups. Its high bond energy makes it less susceptible to decomposition and inefficiency in ultra-high temperature and high-salt calcium environments. Due to lattice substitution, the surface of clay particles becomes negatively charged. The fluid loss reducer adsorbs onto the surface of the clay particles through electrostatic interactions and hydrogen bonding, forming a spatial network structure between the clay particles and the fluid loss reducer macromolecules. This increases the hydration film thickness, zeta potential, and repulsion between the clay particles, making the clay particles less likely to aggregate. This maintains a certain degree of dispersion in the drilling fluid, resulting in smaller clay particles. Consequently, under the action of differential pressure, a dense, low-permeability filter cake forms, effectively reducing fluid loss in the drilling fluid. However, it only has good fluid loss reduction performance at 180°C under saturated salt conditions and cannot be effectively applied in high-temperature and high-salt formations above 210°C.

[0005] Therefore, it is necessary to study a drilling fluid viscosity-enhancing and filtration-reducing agent that is salt-responsive, resistant to ultra-high temperatures, and resistant to high salt, to provide core material support for drilling in complex formations such as deep well salt-gypsum layers and ultra-deep high-pressure brine layers, and to promote the technological leap of drilling fluid treatment agents from "passive salt resistance" to "active response", which is of great significance for the safe and efficient development of deep oil and gas resources. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention aims to provide a salt-responsive, temperature- and salt-resistant, water-based drilling fluid viscosity-increasing and fluid-loss reducing agent, as well as its preparation method and application. The salt-responsive viscosity-increasing and fluid-loss reducing agent provided by the present invention concentrates cations and anions into a single monomer molecule, thereby ensuring that the synthesized product contains cations and anions of equal charge, exhibits good adsorption capacity and salt-responsive properties, is inherently salt-compatible, and is effectively resistant to high temperatures and high salt concentrations. It also exhibits excellent viscosity-increasing and fluid-loss reduction effects on drilling fluids.

[0007] The technical solutions of the present invention are as follows: A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by weight: 30-50 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 20-40 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 35-55 parts of N,N-dimethylacrylamide, 10-25 parts of 4-vinylpyridine, 300-500 parts of water, and 1-5 parts of an initiator.

[0008] Preferably, according to the present invention, the salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared by including the following raw materials in parts by mass: 40 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 30 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 40 parts of N,N-dimethylacrylamide, 20 parts of 4-vinylpyridine, 400 parts of water, and 1 part of initiator.

[0009] According to the present invention, the structure of 1-(2-carboxyethyl)-2-vinylpyridine is as follows: .

[0010] According to the present invention, 1-(2-carboxyethyl)-2-vinylpyridine is prepared according to existing methods. Preferably, the preparation method is as follows: 2-vinylpyridine and chloroacetic acid are dissolved in acetonitrile, reacted by reflux stirring, filtered, washed, and dried to obtain 1-(2-carboxyethyl)-2-vinylpyridine. The molar ratio of 2-vinylpyridine to chloroacetic acid is 1:1; the volume ratio of the molar amount of 2-vinylpyridine to acetonitrile is 0.8-1.2 mol / L; the reaction temperature is 60-75°C, and the reaction time is 20-24 hours.

[0011] According to the present invention, the structure of the (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt is as follows: .

[0012] Preferably, according to the present invention, the initiator is an aqueous solution of ammonium persulfate and sodium bisulfite; the mass ratio of ammonium persulfate and sodium bisulfite is 1:1, and the mass concentration of the aqueous solution of ammonium persulfate and sodium bisulfite is 0.1-1%.

[0013] The preparation method of the salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer comprises the following steps: 1-(2-carboxyethyl)-2-vinylpyridine, (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide and 4-vinylpyridine are fully dissolved in water, an initiator is added, and the mixture is reacted, dried and crushed to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

[0014] According to the present invention, the reaction temperature is preferably 60-80°C, the reaction time is 3-6 hours, and the reaction is carried out under protective gas with stirring. Preferably, the protective gas is nitrogen or argon.

[0015] The salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid-loss reducing agent is used for viscosity-increasing and fluid-loss reducing of deep well or ultra-deep well drilling fluid.

[0016] According to the present invention, preferably, the bottom hole temperature of deep well or ultra-deep well drilling is above 210°C.

[0017] The technical features and beneficial effects of the present invention are as follows: 1. The salt-responsive, ultra-high-temperature, high-salt resistant water-based drilling fluid viscosity-increasing and fluid loss reducer of the present invention is a polymer made from amide monomers, zwitterionic monomers, and rigid heterocyclic monomers. This polymer utilizes the C—C chain of N,N-dimethylacrylamide as its backbone, resulting in extremely high thermal stability. 1-(2-carboxyethyl)-2-vinylpyridine, (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, and 4-vinylpyridine are used as functional monomers. Temperature- and salt-resistant structures such as pyridine rigid heterocyclic rings and sulfonic acid groups are introduced into the polymer side chains, further enhancing the polymer's thermal stability. Furthermore, the polymer possesses highly adsorbable and hydrating groups such as carboxyl, amide, and amine groups, enabling effective adsorption on clay surfaces. Since most conventional high-temperature resistant water-based drilling fluid fluid loss reducers contain charged groups such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and dimethyldiallyl ammonium chloride (DMDAAC), and the different molar ratios of anions and cations result in a non-zero net charge of the polymer molecules. The like-charge repulsion of the fixed charges on the polymer ion chain causes the molecular chain to stretch and the viscosity to increase. When salt ions invade, the charged groups on the molecular chain and the salt ions attract each other, forming an electrostatic attraction, which easily produces a polyelectrolyte effect, causing the molecular chain to curl and the viscosity to drop sharply. At the same time, the stability of the polymer itself decreases, and its solubility deteriorates or even becomes insoluble, thereby increasing the fluid loss. The water-based drilling fluid viscosity increasing and fluid loss reducer provided by the present invention introduces 1-(2-carboxyethyl)-2-vinylpyridine and (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt zwitterionic monomers as main functional monomers. The monomers not only have temperature-resistant and salt-resistant and adsorption groups such as pyridine heterocycle, sulfonic acid group, carboxyl group and amino group, but also carry positive and negative charges at the same time, which can truly achieve zero net charge in the molecular structure. Therefore, in a high-salt environment, the salt ions weaken the electrostatic cross-linking between the zwitterions through the shielding effect, release the hydration groups, cause the molecular chain to stretch, and exhibit an anti-polyelectrolyte effect, essentially realizing the transformation from "salt resistance" to "salt response", making the polymer essentially compatible with salt, thereby effectively improving the solubility and stability of the salt-responsive zwitterionic polymer in a high-salt environment, and further ensuring the viscosity increasing and fluid loss reduction performance of the fluid loss reducer in a high-temperature and high-salt environment.

[0018] 2. The various raw materials of the present invention work together as a whole to achieve the excellent effects of the present invention. If the monomer type is not suitable, or one or several monomers are not added, or the monomer ratio is not suitable, the performance of the resulting fluid loss reducer will be reduced. The salt-responsive ultra-high temperature and high salt resistant water-based drilling fluid viscosity-increasing fluid loss reducer provided by the present invention has a special anti-polyelectrolyte effect and a positive response to salt. It essentially realizes the transformation from "resisting salt" to "salt response" and is compatible with salt in nature. At the same time, the main functional groups are pyridine rigid heterocycles, sulfonic acid groups, amide groups, amino groups, carboxyl groups and other temperature-resistant and salt-resistant and strong adsorption groups, which further improve the temperature-resistant and salt-resistant and fluid loss reduction properties. Therefore, the water-based drilling fluid viscosity-increasing fluid loss reducer provided by the present invention has excellent salt resistance and temperature resistance, and can adapt to deep wells and ultra-deep well formations. The salt-responsive ultra-high temperature and high salt resistant water-based drilling fluid viscosity-increasing fluid loss reducer can resist ultra-high temperatures up to 210°C and can resist salt to saturation. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to specific examples, but is not limited thereto.

[0020] The experimental methods described in the examples are conventional methods unless otherwise specified; the reagents and materials used are commercially available unless otherwise specified.

[0021] 1-(2-Carboxyethyl)-2-vinylpyridine was prepared according to existing methods. The preparation method is as follows: 2-vinylpyridine and chloroacetic acid are dissolved in acetonitrile, reacted under reflux and stirring, filtered, washed, and dried to obtain 1-(2-carboxyethyl)-2-vinylpyridine. The molar ratio of 2-vinylpyridine to chloroacetic acid is 1:1; the volume ratio of 2-vinylpyridine to acetonitrile is 1 mol / L; the reaction temperature is 70°C, and the reaction time is 24 hours.

[0022] Example 1 A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by mass: 40 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 30 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 40 parts of N,N-dimethylacrylamide, 20 parts of 4-vinylpyridine, 400 parts of water, and 1 part of an initiator (an aqueous solution of ammonium persulfate and sodium bisulfite, with a mass ratio of ammonium persulfate to sodium bisulfite of 1:1 and a mass concentration of 0.5%).

[0023] The preparation method of the above-mentioned salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer comprises the following steps: weighing 1-(2-carboxyethyl)-2-vinylpyridine according to parts by mass and adding it to water to dissolve it, adding (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide, and 4-vinylpyridine to the solution in sequence and mixing them thoroughly, while continuously introducing nitrogen and stirring for 20 minutes, then adding an initiator, heating to 80°C in a constant temperature water bath, reacting for 4 hours under the condition of a magnetic stirrer speed of 600 rpm, drying at 60°C, and then crushing to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

[0024] Example 2 A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by mass: 30 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 40 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 45 parts of N,N-dimethylacrylamide, 20 parts of 4-vinylpyridine, 400 parts of water, and 5 parts of an initiator (an aqueous solution of ammonium persulfate and sodium bisulfite, with a mass ratio of ammonium persulfate to sodium bisulfite of 1:1 and a mass concentration of 0.5%).

[0025] The preparation method of the above-mentioned salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer comprises the following steps: weighing 1-(2-carboxyethyl)-2-vinylpyridine according to parts by mass and adding it to water to dissolve it, adding (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide, and 4-vinylpyridine to the solution in sequence and mixing them thoroughly, while continuously introducing nitrogen and stirring for 20 minutes, then adding an initiator, heating to 80°C in a constant temperature water bath, reacting for 4 hours under the condition of a magnetic stirrer speed of 600 rpm, drying at 60°C, and then crushing to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

[0026] Example 3 A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by mass: 50 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 30 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 55 parts of N,N-dimethylacrylamide, 15 parts of 4-vinylpyridine, 400 parts of water, and 5 parts of an initiator (an aqueous solution of ammonium persulfate and sodium bisulfite, with a mass ratio of ammonium persulfate to sodium bisulfite of 1:1 and a mass concentration of 0.5%).

[0027] The preparation method of the above-mentioned salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer comprises the following steps: weighing 1-(2-carboxyethyl)-2-vinylpyridine according to parts by mass and adding it to water to dissolve it, adding (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide, and 4-vinylpyridine to the solution in sequence and mixing them thoroughly, while continuously introducing nitrogen and stirring for 20 minutes, then adding an initiator, heating to 80°C in a constant temperature water bath, reacting for 4 hours under the condition of a magnetic stirrer speed of 600 rpm, drying at 60°C, and then crushing to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

[0028] Example 4 A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by mass: 30 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 20 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 35 parts of N,N-dimethylacrylamide, 25 parts of 4-vinylpyridine, 400 parts of water, and 5 parts of an initiator (an aqueous solution of ammonium persulfate and sodium bisulfite, with a mass ratio of ammonium persulfate to sodium bisulfite of 1:1 and a mass concentration of 0.5%).

[0029] The preparation method of the above-mentioned salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer comprises the following steps: weighing 1-(2-carboxyethyl)-2-vinylpyridine according to parts by mass and adding it to water to dissolve it, adding (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide, and 4-vinylpyridine to the solution in sequence and mixing them thoroughly, while continuously introducing nitrogen and stirring for 20 minutes, then adding an initiator, heating to 80°C in a constant temperature water bath, reacting for 4 hours under the condition of a magnetic stirrer speed of 600 rpm, drying at 60°C, and then crushing to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

[0030] Example 5 A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by mass: 50 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 40 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 40 parts of N,N-dimethylacrylamide, 10 parts of 4-vinylpyridine, 400 parts of water, and 5 parts of an initiator (an aqueous solution of ammonium persulfate and sodium bisulfite, with a mass ratio of ammonium persulfate to sodium bisulfite of 1:1 and a mass concentration of 0.5%).

[0031] The preparation method of the above-mentioned salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer comprises the following steps: weighing 1-(2-carboxyethyl)-2-vinylpyridine according to parts by mass and adding it to water to dissolve it, adding (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide, and 4-vinylpyridine to the solution in sequence and mixing them thoroughly, while continuously introducing nitrogen and stirring for 20 minutes, then adding an initiator, heating to 80°C in a constant temperature water bath, reacting for 4 hours under the condition of a magnetic stirrer speed of 600 rpm, drying at 60°C, and then crushing to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

[0032] Comparative Example 1 A drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except that the monomer N,N-dimethylacrylamide is not added, and the other raw material compositions are consistent with those in Example 1.

[0033] The preparation method of the drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, with the same differences as above.

[0034] Comparative Example 2 A drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except that the monomer 1-(2-carboxyethyl)-2-vinylpyridine is not added, and the other raw material compositions are consistent with those in Example 1.

[0035] The preparation method of the drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except for the differences.

[0036] Comparative Example 3 A drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except that the monomer (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt is not added, and the other raw material compositions are consistent with Example 1.

[0037] The preparation method of the drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except for the differences.

[0038] Comparative Example 4 A drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except that the monomer 4-vinylpyridine is not added, and the other raw material compositions are consistent with those in Example 1.

[0039] The preparation method of the drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, with the same differences as above.

[0040] Comparative Example 5 A drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except that the monomer 1-(2-carboxyethyl)-2-vinylpyridine is replaced with 2-acrylamide-2-methylpropanesulfonic acid, and the other raw material compositions are consistent with those in Example 1.

[0041] The preparation method of the drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except for the differences.

[0042] Comparative Example 6 A drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except that the monomer (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt is replaced with 2-acrylamido-2-methylpropanesulfonic acid. The other raw material compositions are consistent with those in Example 1.

[0043] The preparation method of the drilling fluid viscosity increasing and fluid loss reducing agent is as described in Example 1, except for the differences.

[0044] Test Example 1 2 wt% of the drilling fluid viscosity increasing and fluid loss reducing agents prepared in the examples and comparative examples were added to the saturated brine base slurry, aged at 210°C for 16 h and stirred in a high-speed stirrer for 20 min. The apparent viscosity (AV), plastic viscosity (PV), dynamic shear force (YP) and fluid loss (FL) were measured. API )change.

[0045] The composition of the saturated salt water-based slurry is: 350 parts by mass of water + 1.75 parts by mass of sodium carbonate + 14 parts by mass of bentonite + 126 parts by mass of sodium chloride.

[0046] Table 1. Performance of different drilling fluid viscosity increasers and fluid loss reducers in saturated brine base slurry

[0047] As can be seen from Table 1, the salt-responsive ultra-high temperature and high salt resistant water-based drilling fluid viscosity-increasing and fluid loss control agents prepared in Examples 1 to 5 and the drilling fluid viscosity-increasing and fluid loss control agents prepared in Comparative Examples 1 to 6 all have viscosity-increasing and fluid loss-reducing effects in saturated salt water-based slurries, among which Example 1 has the best viscosity-increasing and fluid loss-reducing effects. However, the viscosity-increasing and fluid loss-reducing effects of the drilling fluid viscosity-increasing and fluid loss control agents prepared in Comparative Examples 1 to 6 in saturated salt water-based slurries are much lower than those of Examples 1 to 5, with the highest apparent viscosity being only 19 m·Pas and the lowest fluid loss being only 54 ml.

[0048] Test Example 2 2 wt% of the drilling fluid viscosity increasing and fluid loss reducing agents prepared in the examples and comparative examples were added to salt water-based slurries of different concentrations, aged at 210°C for 16 h, and stirred in a high-speed stirrer for 20 min. The apparent viscosity (AV), plastic viscosity (PV), dynamic shear force (YP) and fluid loss (FL) of the slurries were measured. API )change.

[0049] The base slurry comprises: 350 parts by mass of water + 1.75 parts by mass of sodium carbonate + 14 parts by mass of bentonite + 17.5-87.5 parts by mass of sodium chloride.

[0050] Table 2. Properties of saltwater-based slurries with different concentrations

[0051] Table 3. Performance of different drilling fluid viscosity increasers and fluid loss reducers in brine-based slurries with different concentrations

[0052] Table 4. Performance of different drilling fluid viscosity increasers and fluid loss reducers in brine-based slurries with different concentrations

[0053] Table 5. Performance of different drilling fluid viscosity increasers and fluid loss reducers in brine-based slurries with different concentrations

[0054] As shown in Tables 2-5, the salt-responsive ultrahigh-temperature, high-salinity resistant water-based drilling fluid viscosity-increasing and fluid-loss control agents prepared in Examples 1-5 exhibit significant salt-responsiveness and demonstrate excellent viscosity-increasing and fluid-loss reduction effects in saltwater-based slurries. The drilling fluid viscosity-increasing and fluid-loss control agents prepared in Comparative Examples 1-6 exhibited relatively poor viscosity-increasing and fluid-loss reduction effects in saltwater-based slurries.

[0055] In summary, the salt-responsive, ultra-high-temperature, high-salinity resistant water-based drilling fluid viscosity-increasing and fluid loss reducer provided by the present invention still has good viscosity-increasing and fluid loss reduction effects in salt-saturated drilling fluid under high-temperature conditions of 210°C, and can solve the two key problems of rheological control and fluid loss reduction of drilling fluid under ultra-high-temperature, high-salinity conditions.

[0056] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all fall within the scope of protection of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is any contradiction. In order to avoid unnecessary repetition, the present invention will no longer describe various possible combinations separately. In addition, the various different embodiments of the present invention can also be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A salt-responsive, temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer, characterized in that: The invention is prepared by comprising the following raw materials in parts by weight: 30-50 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 20-40 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 35-55 parts of N,N-dimethylacrylamide, 10-25 parts of 4-vinylpyridine, 300-500 parts of water, and 1-5 parts of initiator.

2. The salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity increasing and fluid loss reducing agent according to claim 1, characterized in that: The salt-responsive high-temperature and high-salt resistant water-based drilling fluid viscosity-increasing and fluid loss reducer is prepared from the following raw materials in parts by mass: 40 parts of 1-(2-carboxyethyl)-2-vinylpyridine, 30 parts of (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, 40 parts of N,N-dimethylacrylamide, 20 parts of 4-vinylpyridine, 400 parts of water, and 1 part of initiator.

3. The salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer according to claim 1, characterized in that: The preparation method of 1-(2-carboxyethyl)-2-vinylpyridine is as follows: 2-vinylpyridine and chloroacetic acid are dissolved in acetonitrile, reacted under reflux stirring, filtered, washed, and dried to obtain 1-(2-carboxyethyl)-2-vinylpyridine; the molar ratio of 2-vinylpyridine to chloroacetic acid is 1:1; the volume ratio of the molar amount of 2-vinylpyridine to acetonitrile is 0.8-1.2 mol / L; the reaction temperature is 60-75°C, and the reaction time is 20-24 hours.

4. The salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity increasing and fluid loss reducing agent according to claim 1, characterized in that: The initiator is an aqueous solution of ammonium persulfate and sodium bisulfite; the mass ratio of ammonium persulfate to sodium bisulfite is 1:1, and the mass concentration of the aqueous solution of ammonium persulfate and sodium bisulfite is 0.1-1%.

5. The method for preparing the salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer according to any one of claims 1 to 4, characterized in that: The steps are as follows: 1-(2-carboxyethyl)-2-vinylpyridine, (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt, N,N-dimethylacrylamide and 4-vinylpyridine are fully dissolved in water, an initiator is added, and the mixture is reacted, dried and crushed to obtain a salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer.

6. The method for preparing the salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity-increasing and fluid loss reducer according to claim 5, characterized in that: The reaction temperature is 60-80° C., the reaction time is 3-6 hours, and the reaction is carried out under protective gas protection and stirring conditions; the protective gas is nitrogen or argon.

7. Use of the salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity increasing and fluid loss reducing agent according to any one of claims 1 to 4, characterized in that: Used to increase viscosity and reduce filtration of deep or ultra-deep well drilling fluids.

8. The use of the salt-responsive temperature-resistant and salt-resistant water-based drilling fluid viscosity increasing and fluid loss reducing agent according to claim 7, characterized in that: The bottom hole temperature of deep or ultra-deep well drilling is above 210℃.

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