A polymer viscosity reducer for water-based drilling fluid and a preparation method thereof

Abstract

The present invention provides a polymer viscosity reducer for water-based drilling fluid and a preparation method thereof, and relates to the technical field of oilfield chemistry for petroleum drilling engineering. The polymer viscosity reducer for water-based drilling fluid provided by the present invention comprises the following raw materials by mass: 100-150 parts of water, 30-50 parts of acrylic acid, 10-20 parts of maleic anhydride, 40-60 parts of allyl polyethylene glycol, 3-6 parts of initiator, 1-3 parts of pH adjuster, 10-20 parts of diamine, and 5-10 parts of saturated organic acid. The polymer viscosity reducer for water-based drilling fluid provided by the present invention has the characteristics of good viscosity reduction effect and high temperature resistance. At the same time, on the basis of having good viscosity reduction performance, it also has a strong filtration loss reduction effect, does not contain sulfur elements, is safe and environmentally friendly, and has a wide range of applications. The results of the embodiment show that the temperature resistance of the polymer viscosity reducer for water-based drilling fluid reaches 200°C, the viscosity reduction rate is more than 90%, and the filtration loss is less than 20mL.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry for petroleum drilling engineering, and in particular to a polymer viscosity reducer for water-based drilling fluid and a preparation method thereof. Background Art

[0002] Oil and gas exploration and development has gradually developed towards areas with high geological difficulties. The harsh geological conditions have brought great difficulties to drilling operations, and drilling fluid, which is known as the blood of the oil and gas engineering field, is the first to be affected. While facing complex formation lithology, drilling fluid is also facing a series of tests such as high temperature and high pressure, environmental protection, etc. Mudstone pollution, high temperature and high pressure, and environmental protection have become the three major problems restricting the progress of drilling fluid technology. In recent years, the drilling of tight oil and gas and 10,000-meter deep wells have all faced these problems, and drilling fluid thickening is an important factor in the regulation of drilling fluid performance. How to ensure that the drilling fluid maintains a stable viscosity during drilling requires drilling fluid viscosity reducers to solve. For a long time, the viscosity reducers for drilling fluids have been mainly composed of sulfonated tannins, sulfonated tannins and sulfonated polymers containing sulfur elements. Even earlier, they were mainly composed of iron-chromium lignin sulfonates containing heavy metals. These treatment agents have brought great difficulties to the post-treatment of drilling fluids and drill cuttings after drilling operations. Even though the technology of keeping drilling fluids and drill cuttings off the ground has been implemented at this stage, it is still inevitable that during the treatment process, due to the presence of sulfur elements and heavy metals, the treated sewage and sludge are difficult to discharge, resulting in the pile-up of treated wastes, which is difficult to solve.

[0003] Based on this, researchers have done a lot of research on environmentally friendly drilling fluid treatment agents, but either the temperature resistance effect is limited or the viscosity reduction effect is poor, which seriously restricts the progress of drilling fluid technology, especially in drilling fluid viscosity reducers. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a polymer viscosity reducer for water-based drilling fluid and a preparation method thereof. The polymer viscosity reducer for water-based drilling fluid provided by the present invention has good viscosity reducing effect, high temperature resistance, does not contain sulfur, and is safe and environmentally friendly.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a polymer viscosity reducer for water-based drilling fluid, comprising the following raw materials in parts by weight:

[0007] 100-150 parts of water, 30-50 parts of acrylic acid, 10-20 parts of maleic anhydride, 40-60 parts of allyl polyethylene glycol, 3-6 parts of initiator, 1-3 parts of pH adjuster, 10-20 parts of diamine, and 5-10 parts of saturated organic acid.

[0008] Preferably, the number average molecular weight of the allyl polyethylene glycol is 300-700.

[0009] Preferably, the initiator comprises ammonium persulfate and / or potassium persulfate.

[0010] Preferably, the pH adjuster includes one or more of sodium hydroxide, potassium hydroxide and triethanolamine.

[0011] Preferably, the diamine includes one or more of ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine.

[0012] Preferably, the saturated organic acid comprises one or more of formic acid, acetic acid and citric acid.

[0013] The present invention provides a method for preparing a polymer viscosity reducer for water-based drilling fluid according to the above technical solution, comprising the following steps:

[0014] The diamine and maleic anhydride are mixed to carry out an amidation reaction to obtain an amidation product;

[0015] The amidation product, water, acrylic acid, allyl polyethylene glycol, a pH regulator and an initiator are mixed to carry out a polymerization reaction to obtain a polymerization product;

[0016] The polymer product is mixed with a saturated organic acid for neutralization reaction to obtain the polymer viscosity reducer for water-based drilling fluid.

[0017] Preferably, the amidation reaction is carried out at a temperature of 60 to 80° C. and for a time of 1 to 2 hours.

[0018] Preferably, the polymerization reaction temperature is 45-70° C. and the time is 2-3 hours.

[0019] Preferably, the neutralization reaction temperature is room temperature to 70° C., and the time is 1 to 2 hours.

[0020] The present invention provides a polymer viscosity reducer for water-based drilling fluid, comprising the following raw materials in parts by weight: 100-150 parts of water, 30-50 parts of acrylic acid, 10-20 parts of maleic anhydride, 40-60 parts of allyl polyethylene glycol, 3-6 parts of initiator, 1-3 parts of pH regulator, 10-20 parts of diamine, and 5-10 parts of saturated organic acid. In the present invention, the diamine undergoes amidation reaction with maleic anhydride and then undergoes polymerization reaction with acrylic acid and allyl polyethylene glycol to form a polymer with an amine extension chain. Maleic anhydride and acrylic acid polymers themselves have a certain dilution and viscosity reduction effect, but their viscosity reduction effect is still insufficient. The allyl polyethylene glycol introduced in the present invention provides a polyethylene glycol extension chain on this basis, which improves the hydrophilicity and enhances the expansion ability of the molecular chain, laying a foundation for further viscosity reduction of the polymer. The polymer with allyl polyethylene glycol can be adsorbed on the surface of each tiny particle and generate electrostatic repulsion to disperse the particles, and improve the lubrication effect between particles, weaken the internal friction, and achieve a reduction in macroscopic viscosity; and the present invention also introduces diamine, and provides an extension chain with an amine group in the polymer. The amine group has a strong adsorption capacity, can carry out directional adsorption on mudstone, inhibit and relieve the expansion and dispersion of clay, and improve the compatibility of the viscosity reducer with other treating agents in the drilling fluid, improve the viscosity reduction performance, and can further improve the temperature resistance.

[0021] The polymer viscosity reducer for water-based drilling fluid provided by the present invention has the characteristics of good viscosity reduction effect and high temperature resistance. At the same time, on the basis of having good viscosity reduction performance, it also has a strong filtration loss reduction effect, does not contain sulfur elements, is safe and environmentally friendly, and has a wide range of applications. The results of the embodiment show that the polymer viscosity reducer for water-based drilling fluid has a temperature resistance of 200°C, a viscosity reduction rate of more than 90%, and a filtration loss of less than 20mL. DETAILED DESCRIPTION

[0022] The present invention provides a polymer viscosity reducer for water-based drilling fluid, comprising the following raw materials in parts by weight:

[0023] 100-150 parts of water, 30-50 parts of acrylic acid, 10-20 parts of maleic anhydride, 40-60 parts of allyl polyethylene glycol, 3-6 parts of initiator, 1-3 parts of pH adjuster, 10-20 parts of diamine, and 5-10 parts of saturated organic acid.

[0024] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known in the art.

[0025] Calculated by weight, the raw materials for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention include 10 to 20 parts of maleic anhydride, preferably 15 to 20 parts.

[0026] Based on the mass fraction of the maleic anhydride, the raw material for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention includes 10 to 20 parts of diamine, preferably 15 to 20 parts. In the present invention, the diamine preferably includes one or more of ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine, more preferably ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine. When the diamine is ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine, the mass ratio of ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine is preferably 2:2:3:3. In the present invention, the diamine and maleic anhydride can undergo an amidation reaction, and the diamine provides an extension chain with an amine group in the polymer. The amine group has a strong adsorption capacity and can directionally adsorb mudstone, inhibit and relieve the expansion and dispersion of clay, and improve the compatibility of the viscosity reducer with other treatment agents in the drilling fluid, improve the viscosity reduction performance, and can further improve the temperature resistance.

[0027] Based on the mass fraction of the maleic anhydride, the raw materials for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention include 100 to 150 parts of water, preferably 120 to 150 parts of water, and the water is preferably deionized water.

[0028] Based on the mass fraction of maleic anhydride, the raw materials for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention include 30 to 50 parts of acrylic acid, preferably 40 to 50 parts.

[0029] Based on the mass fraction of maleic anhydride, the raw material for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention includes 40 to 60 parts of allyl polyethylene glycol, preferably 50 to 60 parts. In the present invention, the number average molecular weight of the allyl polyethylene glycol is preferably 300 to 700, more preferably 400 to 500.

[0030] Based on the mass fraction of the maleic anhydride, the raw materials for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention include 1 to 3 parts of pH adjuster, preferably 2 to 3 parts. In the present invention, the pH adjuster preferably includes one or more of sodium hydroxide, potassium hydroxide and triethanolamine.

[0031] Based on the mass fraction of the maleic anhydride, the raw material for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention includes 3 to 6 parts of initiator, preferably 5 to 6 parts. In the present invention, the initiator preferably includes ammonium persulfate and / or potassium persulfate; when the initiator includes ammonium persulfate and potassium persulfate, the mass ratio of ammonium persulfate to potassium persulfate is preferably 3:7 or 7:3.

[0032] In the present invention, the product of the amidation reaction of the diamine and maleic anhydride can undergo polymerization reaction with acrylic acid and allyl polyethylene glycol under the action of an initiator. Maleic anhydride and acrylic polymers themselves have a certain dilution and viscosity reduction effect. The introduced allyl polyethylene glycol provides polyethylene glycol extension chains on this basis, which improves the hydrophilicity and also enhances the expansion capacity of the molecular chain, laying a foundation for further viscosity reduction of the polymer. The polymer with allyl polyethylene glycol can be adsorbed on the surface of each tiny particle and generate electrostatic repulsion to disperse the particles, and improve the lubrication effect between particles, weaken the internal friction, and achieve a reduction in macroscopic viscosity.

[0033] Based on the mass fraction of the maleic anhydride, the raw materials for preparing the polymer viscosity reducer for water-based drilling fluid provided by the present invention include 5 to 10 parts of saturated organic acid, preferably 8 to 10 parts. In the present invention, the saturated organic acid preferably includes one or more of formic acid, acetic acid and citric acid, more preferably formic acid, acetic acid and citric acid. When the saturated organic acid includes formic acid, acetic acid and citric acid, the mass ratio of formic acid, acetic acid and citric acid is preferably 1:3:6. In the present invention, the saturated organic acid is used to neutralize the excess amine in the reaction.

[0034] The polymer viscosity reducer for water-based drilling fluid provided by the present invention has the characteristics of good viscosity reducing effect and high temperature resistance. At the same time, on the basis of having good viscosity reducing performance, it also has a strong filtration loss reduction effect, does not contain sulfur elements, is safe and environmentally friendly, and has a wide range of applications, thus overcoming the problem that existing sulfonated viscosity reducers are difficult to meet environmental protection requirements.

[0035] The present invention provides a method for preparing a polymer viscosity reducer for water-based drilling fluid according to the above technical solution, comprising the following steps:

[0036] The diamine and maleic anhydride are mixed to carry out an amidation reaction to obtain an amidation product;

[0037] The amidation product, water, acrylic acid, allyl polyethylene glycol, a pH regulator and an initiator are mixed to carry out a polymerization reaction to obtain a polymerization product;

[0038] The polymer product is mixed with a saturated organic acid for neutralization reaction to obtain the polymer viscosity reducer for water-based drilling fluid.

[0039] The present invention mixes a diamine and maleic anhydride to carry out an amidation reaction to obtain an amidation product. In the present invention, the temperature of the amidation reaction (hydrogen displacement amidation reaction) is preferably 60 to 80°C (reaction in a molten state), more preferably 70 to 80°C, and the time is preferably 1 to 2 hours, more preferably 1.5 to 2 hours. The present invention preferably adds the diamine to a reaction vessel under stirring conditions, heats to 60 to 70°C, slowly adds maleic anhydride thereto, and carries out an amidation reaction at a temperature of 60 to 80°C.

[0040] After obtaining the amidation product, the present invention mixes the amidation product, water, acrylic acid, allyl polyethylene glycol, pH regulator and initiator to carry out polymerization reaction to obtain a polymerization product. In the present invention, the method of mixing the amidation product, water, acrylic acid, allyl polyethylene glycol, pH regulator and initiator is preferably: cooling the reaction container containing the amidation product to room temperature, slowly adding water, acrylic acid, allyl polyethylene glycol thereto, and then adding pH regulator, stirring for 0.5 to 1 hour, and then adding initiator. In the present invention, the temperature of the polymerization reaction is preferably 45 to 70°C, and the time is 2 to 3 hours. The present invention preferably heats the mixed system obtained by mixing to 45 to 55°C, and controls the temperature not to exceed 70°C during the reaction.

[0041] After obtaining the polymer product, the present invention mixes the polymer product with a saturated organic acid for neutralization reaction to obtain the polymer viscosity reducer for water-based drilling fluid. The present invention preferably cools the reaction container containing the polymer product to room temperature, and slowly adds the saturated organic acid under stirring conditions. In the present invention, the temperature of the neutralization reaction is preferably room temperature to 70°C, and the time is preferably 1 to 2 hours. In the present invention, the neutralization reaction is a saturated organic acid neutralizing excess amine.

[0042] In the present invention, after the neutralization reaction, a liquid polymer viscosity reducer is obtained. In the present invention, the liquid polymer viscosity reducer can also be spray-dried to obtain a powdered polymer viscosity reducer.

[0043] In order to further illustrate the present invention, the polymer viscosity reducer for water-based drilling fluid and the preparation method thereof provided by the present invention are described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] A polymer viscosity reducer for water-based drilling fluid, prepared from the following raw materials (parts by mass):

[0046] 150 parts of water, 50 parts of acrylic acid, 20 parts of maleic anhydride, 60 parts of allyl polyethylene glycol, 6 parts of initiator, 3 parts of pH adjuster, 20 parts of diamine, and 10 parts of saturated organic acid, wherein the water is deionized water, the number average molecular weight of allyl polyethylene glycol is 400, the initiator is ammonium persulfate, the pH adjuster is sodium hydroxide, the diamine is ethylenediamine, and the saturated organic acid is acetic acid.

[0047] The preparation method of the polymer viscosity reducer for water-based drilling fluid is as follows;

[0048] First, a diamine is added to a three-necked flask under stirring conditions, and after the temperature is raised to 70°C, maleic anhydride is slowly added to carry out a hydrogen displacement amidation reaction. The temperature during the reaction process is controlled at 80°C and the reaction time is 2h to obtain an amidation product.

[0049] Then, cool the three-necked flask containing the amidation product to room temperature, slowly add water, acrylic acid, allyl polyethylene glycol, and then add pH adjuster, stir for 1 hour, add initiator to initiate polymerization, and heat to 55°C. At this time, the reaction is violent, and the temperature in the three-necked flask should be carefully observed to control the temperature not exceeding 70°C. The reaction time is 3 hours;

[0050] Afterwards, the three-necked flask was cooled to room temperature, and saturated organic acid was slowly added under stirring to neutralize excess amine. The temperature of the material in the three-necked flask was controlled not to be higher than 70° C. The reaction time was 2 h to obtain a liquid polymer viscosity reducer.

[0051] Example 2

[0052] A polymer viscosity reducer for water-based drilling fluid, prepared from the following raw materials (parts by mass):

[0053] 100 parts of water, 30 parts of acrylic acid, 10 parts of maleic anhydride, 40 parts of allyl polyethylene glycol, 3 parts of initiator, 1 part of pH adjuster, 10 parts of diamine, 5 parts of saturated organic acid, wherein the water is deionized water, the number average molecular weight of allyl polyethylene glycol is 700, the initiator is potassium persulfate, the pH adjuster is triethanolamine, the diamine is N,N-dimethylpropylenediamine, and the saturated organic acid is formic acid.

[0054] The preparation method of the water-based drilling fluid polymer viscosity reducer is as follows:

[0055] First, a diamine is added to a three-necked flask under stirring conditions, and after the temperature is raised to 60°C, maleic anhydride is slowly added to carry out a hydrogen displacement amidation reaction. The temperature during the reaction process is controlled at 60°C and the reaction time is 1h to obtain an amidation product;

[0056] Then, cool the three-necked flask containing the amidation product to room temperature, slowly add water, acrylic acid, allyl polyethylene glycol, and then add pH adjuster, stir for 0.5h, add initiator to initiate polymerization, and heat to 45°C. At this time, the reaction is violent, and the temperature in the three-necked flask should be carefully observed to control the temperature not exceeding 70°C. The reaction time is 2h;

[0057] Afterwards, the three-necked flask was cooled to room temperature, and saturated organic acid was slowly added under stirring to neutralize excess amine. The temperature of the material in the three-necked flask was controlled not to be higher than 70° C. The reaction time was 1 hour to obtain a liquid polymer viscosity reducer.

[0058] Example 3

[0059] A polymer viscosity reducer for water-based drilling fluid, prepared from the following raw materials (parts by mass):

[0060] 150 parts of water, 30 parts of acrylic acid, 10 parts of maleic anhydride, 40 parts of allyl polyethylene glycol, 3 parts of initiator, 1 part of pH adjuster, 10 parts of diamine, and 5 parts of saturated organic acid, wherein the water is deionized water, the number average molecular weight of allyl polyethylene glycol is 300, the initiator is ammonium persulfate and potassium persulfate (the mass ratio of ammonium persulfate and potassium persulfate is 3:7), the pH adjuster is potassium hydroxide, the diamines are ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine (the mass ratio of ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine is 2:2:3:3), and the saturated organic acids are formic acid, acetic acid and citric acid (the mass ratio of formic acid, acetic acid and citric acid is 1:3:6).

[0061] The preparation method of the water-based drilling fluid polymer viscosity reducer is as follows:

[0062] First, a diamine is added to a three-necked flask under stirring conditions, and after the temperature is raised to 70°C, maleic anhydride is slowly added to carry out a hydrogen displacement amidation reaction. The temperature during the reaction process is controlled at 60°C and the reaction time is 1h to obtain an amidation product;

[0063] Then, cool the three-necked flask containing the amidation product to room temperature, slowly add water, acrylic acid, allyl polyethylene glycol, and then add pH adjuster, stir for 1 hour, add initiator to initiate polymerization, and heat to 55°C. At this time, the reaction is violent, and the temperature in the three-necked flask should be carefully observed to control the temperature not exceeding 70°C. The reaction time is 2 hours;

[0064] Afterwards, the three-necked flask was cooled to room temperature, and saturated organic acid was slowly added under stirring to neutralize excess amine, and the temperature of the material in the three-necked flask was controlled not to be higher than 70° C. The reaction time was 2 h to obtain a liquid polymer viscosity reducer; the obtained liquid polymer viscosity reducer was spray-dried to obtain a powdered polymer viscosity reducer.

[0065] Example 4

[0066] A polymer viscosity reducer for water-based drilling fluid, prepared from the following raw materials (parts by mass):

[0067] 120 parts of water, 40 parts of acrylic acid, 15 parts of maleic anhydride, 50 parts of allyl polyethylene glycol, 5 parts of initiator, 2 parts of pH adjuster, 15 parts of diamine, 8 parts of saturated organic acid, wherein the water is deionized water, the number average molecular weight of allyl polyethylene glycol is 500, the initiator is ammonium persulfate and potassium persulfate (the mass ratio of ammonium persulfate and potassium persulfate is 7:3), the pH adjuster is sodium hydroxide and potassium hydroxide (the mass ratio of sodium hydroxide and potassium hydroxide is 4:6), the diamine is hexamethylenediamine, and the saturated organic acid is citric acid.

[0068] The preparation method of the water-based drilling fluid polymer viscosity reducer is as follows:

[0069] First, the diamine was added into a three-necked flask under stirring conditions, and after the temperature was raised to 65°C, maleic anhydride was slowly added to carry out a hydrogen displacement amidation reaction. The temperature during the reaction process was controlled at 70°C and the reaction time was 1.5h to obtain an amidation product.

[0070] Then, cool the three-necked flask containing the amidation product to room temperature, slowly add water, acrylic acid, allyl polyethylene glycol, and then add pH adjuster, stir for 1 hour, add initiator to initiate polymerization, and heat to 50°C. At this time, the reaction is violent, and the temperature in the three-necked flask should be carefully observed to control the temperature not exceeding 70°C. The reaction time is 2 hours;

[0071] Afterwards, the three-necked flask was cooled to room temperature, and saturated organic acid was slowly added under stirring to neutralize excess amine, and the temperature of the material in the three-necked flask was controlled not to be higher than 70° C. The reaction time was 1 hour to obtain a liquid polymer viscosity reducer; the obtained liquid polymer viscosity reducer was spray-dried to obtain a powder polymer viscosity reducer.

[0072] Comparative Example

[0073] Sulfonated tannins are used as viscosity reducers.

[0074] The performance test of the polymer viscosity reducer prepared in the example is as follows:

[0075] (i) The polymer viscosity reducer obtained in the above example was evaluated according to the following evaluation method in the base slurry, and the performance test was carried out according to the apparent viscosity test method of GB / T16783.1-2014 "Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids".

[0076] Test plan:

[0077] The basic formula composition is as follows: 100 mL of fresh water + 8 g of bentonite + 0.2 g of sodium hydroxide + 0.5 g of sodium carbonate + 2 g of the viscosity reducer of Examples 1 to 2 (or + 1 g of the viscosity reducer of Examples 3 to 4 and the comparative example); and compared with the basic formula without the viscosity reducer of the example;

[0078] Weighted formula composition: 100mL fresh water + 6g bentonite + 0.3g sodium hydroxide + 1.0g sodium carbonate + 3g viscosity reducer of Examples 1-2 (or + 1.5g viscosity reducer of Examples 3-4 and comparative examples) + barite weighted to a density of 2.0g / cm 3 ; and compared with the weighted formula without adding the viscosity reducer of the embodiment.

[0079] The test results are shown in Table 1:

[0080] Table 1 Viscosity reduction performance of polymer viscosity reducer in base slurry

[0081]

[0082] It can be seen from Table 1 that the polymer viscosity reducer of the embodiment of the present invention and the sulfonated tannin of the comparative example both have good viscosity reducing effects in the base slurry. The viscosity reducing and fluid loss reducing effects of the polymer viscosity reducer of the embodiment of the present invention are better than those of the sulfonated tannin of the comparative example. The sulfonated tannin of the comparative example is limited in application due to the sulfur element contained.

[0083] (ii) The polymer viscosity reducer obtained in the above embodiment was added to a high-temperature water-based drilling fluid system commonly used for drilling for evaluation, and the rheological properties and filtration loss properties of the drilling fluid were evaluated according to GB / T16783.1-2014 "Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids".

[0084] Test plan:

[0085] High temperature water-based drilling fluid system: 100 mL fresh water + 3 g bentonite + 0.3 g sodium hydroxide + 0.3 g sodium carbonate + 1.2 g high temperature viscosity enhancer + 2.5 g high temperature polymer fluid loss reducer + 2 g natural asphalt + 7 g potassium chloride + 10 g sodium chloride + 3 g viscosity reducer of Examples 1-2 (or + 1.5 g of Examples 3-4, or + 3 g of viscosity reducer of comparative example) + barite weighted to 2.0 g / cm 3 + 20g mudstone pollution (recorded as 20%); and compared with the high-temperature water-based drilling fluid system without adding the viscosity reducer of the embodiment and without adding mudstone pollution.

[0086] The test results are shown in Table 2:

[0087] Table 2 Performance of polymer viscosity reducer in drilling fluid

[0088] Mudstone contamination Viscosity reducer sample T state PV YP Φ3 API HTHP Opening status 0％ 0％ 200 After aging for 48h 55 10 9 5.2 14.8 20％ 0％ 200 After aging for 48h 100 42 36 20.2 51.4 Thick, difficult to flow 20％ Example 1 200 After aging for 48h 44 9 8 4.4 12.2 Uniform 20％ Example 2 200 After aging for 48h 48 11 10 5.0 13.8 Uniform 20％ Example 3 200 After aging for 48h 42 8 8 4.6 11.4 Uniform 20％ Example 4 200 After aging for 48h 45 9 7 4.8 11.6 Uniform 20％ Comparative Example 200 After aging for 48h 64 15 14 7.8 32.6 Very sticky

[0089] It can be seen from Table 2 that the polymer viscosity reducer of the embodiment of the present invention has good compatibility in the high-temperature water-based drilling fluid system. When the drilling fluid is contaminated by high-concentration mudstone, the viscosity of the drilling fluid increases sharply. Adding the polymer viscosity reducer can restore the viscosity of the drilling fluid and reduce filtration loss.

[0090] Note: The meanings of the parameters in Table 1 and Table 2 are as follows:

[0091] T: drilling fluid aging temperature, °C;

[0092] AV: drilling fluid apparent viscosity, mPa·s;

[0093] PV: drilling fluid plastic viscosity, mPa·s;

[0094] YP: dynamic shear force of drilling fluid, Pa;

[0095] Φ3: 3-turn reading of a six-speed rotary viscometer, dimensionless;

[0096] API: medium pressure water loss of drilling fluid (0.7MPa, 30min), mL;

[0097] HTHP: high temperature and high pressure water loss of drilling fluid (3.5MPa, T, 30min), mL;

[0098] JNL: AV reduction rate before and after adding the sample to the formula, %.

[0099] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A polymer viscosity reducer for water-based drilling fluid, characterized in that: Prepared from the following raw materials in parts by weight: 100-150 parts of water, 30-50 parts of acrylic acid, 10-20 parts of maleic anhydride, 40-60 parts of allyl polyethylene glycol, 3-6 parts of initiator, 1-3 parts of pH adjuster, 10-20 parts of diamine, 5-10 parts of saturated organic acid; The method for preparing the polymer viscosity reducer for water-based drilling fluid comprises the following steps: Mixing diamine and maleic anhydride for amidation reaction to obtain an amidation product; the amidation reaction temperature is 60 to 80° C. and the time is 1 to 2 hours; The amidation product, water, acrylic acid, allyl polyethylene glycol, a pH regulator and an initiator are mixed to carry out a polymerization reaction to obtain a polymerization product; The polymer product is mixed with a saturated organic acid for neutralization reaction to obtain the polymer viscosity reducer for water-based drilling fluid.

2. The polymer viscosity reducer for water-based drilling fluid according to claim 1, characterized in that: The number average molecular weight of the allyl polyethylene glycol is 300-700.

3. The polymer viscosity reducer for water-based drilling fluid according to claim 1, characterized in that: The initiator includes ammonium persulfate and / or potassium persulfate.

4. The polymer viscosity reducer for water-based drilling fluid according to claim 1, characterized in that: The pH regulator includes one or more of sodium hydroxide, potassium hydroxide and triethanolamine.

5. The polymer viscosity reducer for water-based drilling fluid according to claim 1, characterized in that: The diamine includes one or more of ethylenediamine, N,N-dimethylpropylenediamine, hexamethylenediamine and polyetheramine.

6. The polymer viscosity reducer for water-based drilling fluid according to claim 1, characterized in that: The saturated organic acid includes one or more of formic acid, acetic acid and citric acid.

7. The method for preparing the polymer viscosity reducer for water-based drilling fluid according to any one of claims 1 to 6, characterized in that: The following steps are involved: Mixing diamine and maleic anhydride for amidation reaction to obtain an amidation product; the amidation reaction temperature is 60 to 80° C. and the time is 1 to 2 hours; The amidation product, water, acrylic acid, allyl polyethylene glycol, a pH regulator and an initiator are mixed to carry out a polymerization reaction to obtain a polymerization product; The polymer product is mixed with a saturated organic acid for neutralization reaction to obtain the polymer viscosity reducer for water-based drilling fluid.

8. The preparation method according to claim 7, characterized in that: The polymerization reaction temperature is 45-70° C. and the reaction time is 2-3 hours.

9. The preparation method according to claim 7, characterized in that: The neutralization reaction temperature is room temperature to 70° C., and the reaction time is 1 to 2 hours.

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