A polyacrylamide coating agent for water-based drilling fluid and its preparation method

Abstract

This invention belongs to the field of oilfield drilling technology, specifically relating to a polyacrylamide coating agent for water-based drilling fluids and its preparation method. The coating agent is prepared by using an initiator to initiate a free radical polymerization reaction of acrylamide, a modifier, and monomer 2. The modifier contains a large number of unsaturated alkenyl substituents and a large number of sulfonic acid groups, which enables the prepared polyacrylamide molecular chain to exhibit a cross-linked structure, thereby improving the high temperature resistance and salt resistance of the coating agent. The quaternary ammonium cationic groups in the monomer 2 structure can generate a strong electrostatic adsorption effect with negatively charged clay mineral particles, while the large number of hydrophilic ether bonds in the structure can produce good compatibility with hydrophilic clay minerals, thereby highly coating the surface of clay mineral particles and effectively inhibiting rock cuttings dispersion.

Description

Technical Field

[0001] This invention belongs to the field of oilfield drilling technology, specifically relating to a polyacrylamide coating agent for water-based drilling fluids and its preparation method. Background Technology

[0002] Drilling fluid coating inhibitors are core chemical treatment agents used in oil and gas drilling to stabilize the wellbore and inhibit formation hydration and swelling. They maintain drilling fluid stability by forming a protective layer on the drill cuttings surface, preventing clay minerals from contacting water molecules. Polyacrylamide (PAM), as one of the most commonly used coating inhibitors, dominates in onshore and shallow-sea drilling due to its tunable molecular structure and diverse functions. Currently, as conventional oil and gas development gradually extends to deeper layers, drilling fluid loss is significant in deep and ultra-deep wells due to higher formation temperatures and salinity. Therefore, the temperature resistance and coating inhibition performance requirements for coating inhibitors are particularly stringent.

[0003] At present, the modification of polyacrylamide coating inhibitors is mainly achieved by designing their structure. For example, the invention patent with application number CN201410184206.4 shows that by selecting polymer monomers, the prepared polyacrylamide coating agent can exhibit good temperature resistance. Therefore, by adjusting the structure of polyacrylamide, its functionality can be enhanced to meet the usage requirements of deep well environments. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a polyacrylamide coating agent for water-based drilling fluids and its preparation method.

[0005] In a first aspect, the present invention provides a polyacrylamide coating agent for water-based drilling fluids, which is made from raw materials comprising the following parts by weight:

[0006] Acrylamide 50-65 parts, modifier 0.5-1.5 parts, monomer 1-3 parts, initiator 0.1-0.2 parts, deionized water 80-100 parts;

[0007] The modifier is prepared by reacting exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid.

[0008] The second monomer is prepared by first modifying 4-hydroxybutyl vinyl polyoxyethylene ether by carboxylation, and then reacting the product with dodecyl dihydroxyethyl methyl ammonium chloride.

[0009] As a preferred embodiment of the present invention, the modifier is prepared by the following method:

[0010] 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and dimethyl sulfoxide were added to a polymerization reactor and mechanically stirred until homogeneous. Nitrogen gas was then introduced for protection. N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid was added to the reactor. After addition, the mixture was stirred at 30-40°C for 2-4 hours. Next, the catalyst was added to the reactor, and the heating rate was controlled at 2-3°C / min. The temperature was raised to 80-90°C and continuously stirred for 12-16 hours. The nitrogen gas was then removed, the solvent was evaporated, and the product was collected. After washing and vacuum drying, the modifier was obtained.

[0011] As a preferred embodiment of the present invention, the molar ratio of exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid is 1:1.01-1.02.

[0012] As a preferred embodiment of the present invention, the catalyst is p-toluenesulfonic acid or aminosulfonic acid.

[0013] It should be noted that in the above technical solution, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid are used as raw materials. The anhydride groups and active hydroxyl substituents in their structures can undergo ring-opening esterification to obtain an intermediate containing both active hydroxyl and active carboxyl groups in its structure. Then, under the conditions of a catalyst and high temperature, the intermediate undergoes a self-condensation reaction to obtain the modifier.

[0014] As a preferred embodiment of the present invention, monomer two is prepared by the following method:

[0015] Step S1: Add 4-hydroxybutylvinyl polyoxyethylene ether to acetone and mix evenly by mechanical stirring. Then add the carboxylating agent to the formed homogeneous solution. After the addition is complete, keep the mixture at 30-40℃ and stir for 3-6 hours. Stop heating, evaporate and remove the solvent, cool down and discharge the material to obtain the intermediate material.

[0016] Step S2: Add the intermediate material to isopropanol, stir and mix evenly, add the composite catalyst, stir at room temperature for 2-4 hours, then add dodecyl dihydroxyethyl methyl ammonium chloride, continue stirring for 4-8 hours, evaporate to remove solvent, cool and discharge, collect the product, and obtain monomer II.

[0017] As a preferred embodiment of the present invention, in step S1, the number-average molecular weight of the 4-hydroxybutylvinyl polyoxyethylene ether is 2000-3000.

[0018] As a preferred embodiment of the present invention, in step S1, the carboxylating agent is succinic anhydride or glutaric anhydride.

[0019] As a preferred embodiment of the present invention, in step S2, the composite catalyst is a mixture of dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.2-0.3.

[0020] In the above technical solution, firstly, a carboxylating agent is used to modify 4-hydroxybutylvinyl polyoxyethylene ether by carboxylation to obtain a polyoxyethylene ether derivative containing an active carboxyl substituent in its structure, namely, an intermediate material. Then, a composite catalyst is used to activate the carboxyl group of the intermediate material, and then it is esterified and condensed with the hydroxyl group in the dodecylbishydroxyethylmethylammonium chloride structure to obtain monomer II.

[0021] As a preferred embodiment of the present invention, the initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyramidine hydrochloride or azobisisobutyramidazolin hydrochloride.

[0022] A second aspect of the present invention provides a method for preparing a polyacrylamide-based coating agent for water-based drilling fluids, comprising the following steps:

[0023] Step 1: Add acrylamide and monomer II to deionized water, stir and mix evenly, raise the temperature to 70-75℃, and add two-thirds of the initiator. After the addition is complete, continue to keep warm and stir for 2-4 hours to form a prepolymer.

[0024] The second step is to add the modifier and the remaining initiator to the prepolymer, raise the temperature to 80-82℃, keep it warm and stir for 6-12 hours, stop heating, cool down and discharge the material, separate the product, and purify it.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The modifier structure prepared in this invention contains a large number of unsaturated alkenyl substituents, which enables the prepared polyacrylamide molecular chains to exhibit a cross-linked structure. This increase in molecular chain density leads to the obstruction of molecular chain movement, thereby improving the high-temperature resistance of the coating agent. At the same time, the modifier structure also contains rigid rings, which can further enhance the heat stability of the coating agent, thereby effectively improving the high-temperature resistance of the polyacrylamide coating agent. In addition, the modifier structure also contains a large number of sulfonic acid groups. The presence of sulfonic acid groups can enhance the sensitivity of polyacrylamide to mineral salts, enabling the coating agent to maintain high stability under high salinity conditions and exhibiting excellent salt resistance.

[0027] (2) The quaternary ammonium cation group in the monomer distructure prepared by the present invention can generate a strong electrostatic adsorption effect with the negatively charged clay mineral particles, and the large number of hydrophilic ether bonds in the structure can generate good compatibility with hydrophilic clay minerals, thereby highly coating the surface of clay mineral particles and effectively inhibiting the dispersion of rock fragments. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 Infrared analysis results of the modifier;

[0030] Figure 2 This is the infrared analysis test image of monomer two. Detailed Implementation

[0031] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0032] The modifiers used in the following examples and comparative examples were prepared using the following methods:

[0033] 0.2 g of exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and dimethyl sulfoxide were added to the polymerization reactor and mechanically stirred until homogeneous. Nitrogen gas was then introduced for protection. 0.26 g of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid was added to the polymerization reactor. After the addition was complete, the mixture was stirred at 35°C for 3 h. Then, 0.01 g of p-toluenesulfonic acid was added to the polymerization reactor, and the heating rate was controlled at 2°C / min. The temperature was raised to 90°C and stirred continuously for 16 h. The nitrogen gas was then removed, the solvent was evaporated, and the product was collected. After washing and vacuum drying, the modifier was obtained.

[0034] The preparation principle of this modifier is as follows:

[0035]

[0036] Figure 1 This is the infrared analysis test pattern of the modifier, where 3376 cm⁻¹... -1 and 3291cm -1 The characteristic absorption peak appearing at 3043 cm⁻¹ is the characteristic absorption peak of hydroxyl groups. -1The characteristic absorption peak appearing at 1786 cm⁻¹ is the characteristic absorption peak of CH in an unsaturated carbon-carbon double bond. -1 and 1706cm -1 The characteristic absorption peak appearing at 1592 cm⁻¹ is the characteristic C=O absorption peak of the ester group and carboxyl group. -1 The characteristic absorption peak appearing at 917 cm⁻¹ is the CN characteristic absorption peak. -1 The characteristic absorption peak appearing at this point is a characteristic absorption peak of the epoxy group.

[0037] In the following examples and comparative examples, monomer 2 was prepared using the following method:

[0038] Step S1: Add 1.2g of 4-hydroxybutylvinyl polyoxyethylene ether with a number average molecular weight of 2000 to acetone and mix evenly by mechanical stirring. Then add 0.06g of succinic anhydride to the formed uniform solution. After the addition is complete, keep the mixture at 35°C and stir for 4 hours. Stop heating, evaporate and remove the solvent, cool down and discharge the material to obtain the intermediate material.

[0039] Step S2: Add 0.8g of intermediate material to isopropanol, stir and mix evenly, then add 0.1g of dicyclohexylcarbodiimide and 0.03g of 4-dimethylaminopyridine, stir at room temperature for 3h, then add 0.15g of dodecylbis(hydroxyethyl)methylammonium chloride, and continue stirring for 6h after the addition is complete. Evaporate to remove the solvent, cool down and discharge the material, collect the product, and obtain monomer II.

[0040] Figure 2 This is the infrared analysis test image of monomer II, where 3076 cm⁻¹ -1 The characteristic absorption peak appearing at 2800–3000 cm⁻¹ is the characteristic absorption peak of CH in unsaturated carbon-carbon double bonds. -1 The characteristic absorption peak appearing at 1728 cm⁻¹ is the characteristic absorption peak of CH in saturated aliphatic chains. -1 The characteristic absorption peak appearing at 1461 cm⁻¹ is the C=O characteristic absorption peak of the ester group. -1 The characteristic absorption peak appearing at 1098 cm⁻¹ is the CN characteristic absorption peak of quaternary ammonium salt. -1 The characteristic absorption peak appearing at this point is the CO characteristic absorption peak of the ether bond.

[0041] Example 1

[0042] This embodiment provides a polyacrylamide coating agent for water-based drilling fluids, which is made from raw materials comprising the following parts by weight:

[0043] Acrylamide 50 parts, modifier 0.5 parts, monomer 1 part, azobisisobutyronitrile 0.1 parts, deionized water 8 parts.

[0044] The preparation method of the coating agent includes the following steps:

[0045] Step 1: Add acrylamide and monomer II to deionized water, stir and mix evenly, raise the temperature to 70°C, and add two-thirds of the initiator. After the addition is complete, keep the temperature and stir for 2 hours to form a prepolymer.

[0046] The second step involves adding the modifier and the remaining initiator to the prepolymer, raising the temperature to 80°C, maintaining the temperature and stirring for 6 hours, stopping the heating, cooling down and discharging the material, separating the product, and purifying it.

[0047] Example 2

[0048] This embodiment provides a polyacrylamide coating agent for water-based drilling fluids, which is made from raw materials comprising the following parts by weight:

[0049] Acrylamide 55 parts, modifier 1.2 parts, monomer 2.5 parts, azobisisobutyronitrile 0.2 parts, deionized water 90 parts.

[0050] The preparation method of the coating agent includes the following steps:

[0051] Step 1: Add acrylamide and monomer II to deionized water, stir and mix evenly, raise the temperature to 75°C, and add two-thirds of the initiator. After the addition is complete, keep the temperature and stir for 3 hours to form a prepolymer.

[0052] The second step involves adding the modifier and the remaining initiator to the prepolymer, raising the temperature to 82°C, maintaining the temperature and stirring for 9 hours, stopping the heating, cooling down and discharging the material, separating the product, and purifying it.

[0053] Example 3

[0054] This embodiment provides a polyacrylamide coating agent for water-based drilling fluids, which is made from raw materials comprising the following parts by weight:

[0055] Acrylamide 65 parts, modifier 1.5 parts, monomer 3 parts, azobisisobutyronitrile 0.2 parts, deionized water 100 parts.

[0056] The preparation method of the coating agent includes the following steps:

[0057] Step 1: Add acrylamide and monomer 2 to deionized water, stir and mix evenly, raise the temperature to 75°C, and add two-thirds of the initiator. After the addition is complete, keep the temperature and stir for 4 hours to form a prepolymer.

[0058] The second step involves adding the modifier and the remaining initiator to the prepolymer, raising the temperature to 82°C, maintaining the temperature and stirring for 12 hours, stopping the heating, cooling down and discharging the material, separating the product, and purifying it.

[0059] Comparative Example 1

[0060] This comparative example provides a polyacrylamide coating agent for water-based drilling fluids, which is made from raw materials comprising the following parts by weight:

[0061] Acrylamide 55 parts, modifier 1.2 parts, azobisisobutyronitrile 0.2 parts, deionized water 90 parts.

[0062] The preparation method of the coating agent includes the following steps:

[0063] Step 1: Add acrylamide to deionized water, stir and mix evenly, raise the temperature to 75°C, and add two-thirds of the azobisisobutyronitrile. After the addition is complete, keep the temperature and stir for 3 hours to form a prepolymer.

[0064] The second step involves adding the modifier and the remaining amount of azobisisobutyronitrile to the prepolymer, further raising the temperature to 82°C, continuously maintaining the temperature and stirring for 9 hours, stopping the heating, cooling down and discharging the material, separating the product, and purifying it.

[0065] Comparative Example 2

[0066] This embodiment provides a polyacrylamide coating agent for water-based drilling fluids, which is made from raw materials comprising the following parts by weight:

[0067] Acrylamide 55 parts, monomer 2.5 parts, azobisisobutyronitrile 0.2 parts, deionized water 90 parts.

[0068] The preparation method of the coating agent includes the following steps:

[0069] Add acrylamide and monomer 2 to deionized water, stir and mix evenly, raise the temperature to 75°C, and add azobisisobutyronitrile. After the addition is complete, keep warm and stir for 12 hours.

[0070] The coating agents provided in the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows:

[0071] The coating agent was added to a 25% sodium chloride aqueous solution to prepare a 0.3% polymer solution. Then, 50g of shale rock fragments that had passed through a 10-mesh sieve were added to 300mL of the polymer solution and dispersed evenly. The solution was then hot-rolled at 200℃ for 16h. After complete cooling, the rock fragments were separated, completely dried, and weighed. The rock fragment recovery rate was calculated. The test data are shown in Table 1.

[0072] Table 1 - Test Results

[0073]

[0074] As can be seen from the above, the coating agent prepared in the embodiments of the present invention can still maintain a high rock cuttings recovery rate under high temperature and high salt conditions. Removing monomer II weakens the adsorption effect of the coating agent on clay minerals, resulting in a worse rock cuttings recovery rate. Removing the modifier weakens the high temperature and salt resistance of the coating agent, leading to a significant decrease in the rock cuttings recovery rate.

[0075] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A polyacrylamide-based coating agent for water-based drilling fluids, characterized in that, It is made from raw materials comprising the following parts by weight: Acrylamide 50-65 parts, modifier 0.5-1.5 parts, monomer 1-3 parts, initiator 0.1-0.2 parts, deionized water 80-100 parts; The modifier is prepared by reacting exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid. The second monomer is prepared by first modifying 4-hydroxybutyl vinyl polyoxyethylene ether by carboxylation, and then reacting the product with dodecyl dihydroxyethyl methyl ammonium chloride. The initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyramidine hydrochloride or azobisisobutyramidazolin hydrochloride; The modifier is prepared using the following method: 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and dimethyl sulfoxide were added to a polymerization reactor and mechanically stirred until homogeneous. Nitrogen gas was then introduced for protection. N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid was added to the reactor. After addition, the mixture was stirred at 30-40°C for 2-4 hours. Next, the catalyst was added to the reactor, and the heating rate was controlled at 2-3°C / min. The temperature was raised to 80-90°C and continuously stirred for 12-16 hours. The nitrogen gas was then removed, the solvent was evaporated, and the product was collected. After washing and vacuum drying, the modifier was obtained. The catalyst is p-toluenesulfonic acid or aminosulfonic acid.

2. The polyacrylamide coating agent for water-based drilling fluid according to claim 1, characterized in that, The molar ratio of exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid is 1:1.01-1.

02.

3. The polyacrylamide coating agent for water-based drilling fluid according to claim 1, characterized in that, The monomer 2 is prepared using the following method: Step S1: Add 4-hydroxybutylvinyl polyoxyethylene ether to acetone and mix evenly by mechanical stirring. Then add the carboxylating agent to the formed homogeneous solution. After the addition is complete, keep the mixture at 30-40℃ and stir for 3-6 hours. Stop heating, evaporate and remove the solvent, cool down and discharge the material to obtain the intermediate material. The carboxylating agent is succinic anhydride or glutaric anhydride; Step S2: Add the intermediate material to isopropanol, stir and mix evenly, add the composite catalyst, stir at room temperature for 2-4 hours, then add dodecyl dihydroxyethyl methyl ammonium chloride, continue stirring for 4-8 hours after the addition, evaporate to remove the solvent, cool down and discharge the material, collect the product, and obtain monomer II. The composite catalyst is a mixture of dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.2-0.

3.

4. The polyacrylamide coating agent for water-based drilling fluid according to claim 3, characterized in that, In step S1, the number average molecular weight of the 4-hydroxybutylvinyl polyoxyethylene ether is 2000-3000.

5. A method for preparing a polyacrylamide coating agent for water-based drilling fluid as described in claim 1, characterized in that, Includes the following steps: Step 1: Add acrylamide and monomer II to deionized water, stir and mix evenly, raise the temperature to 70-75℃, and add two-thirds of the initiator. After the addition is complete, continue to keep warm and stir for 2-4 hours to form a prepolymer. The second step is to add the modifier and the remaining initiator to the prepolymer, raise the temperature to 80-82℃, keep it warm and stir for 6-12 hours, stop heating, cool down and discharge the material, separate the product, and purify it.

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