Temperature-resistant thixotropic agent, and preparation method therefor and use thereof
A temperature-resistant thixotropic agent prepared by combining modified and optimized adhesive with magnesium aluminum silicate has solved the problem of plugging leakage in fractured reservoirs under high-temperature conditions using magnesium oxychloride cement, achieving stable plugging and reservoir protection, and improving the production efficiency of oil and gas wells.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- QINGDAO UNIV OF TECH
- Filing Date
- 2025-12-17
- Publication Date
- 2026-07-23
AI Technical Summary
Existing plugging materials are difficult to adapt to fracture aperture in fractured formations, resulting in low plugging efficiency and damage to the reservoir. There is limited research on thixotropic agents under high-temperature conditions, especially thixotropic agents suitable for magnesium oxychloride cement.
A temperature-resistant thixotropic agent was prepared by combining modified sizing agent with magnesium aluminum silicate. The sizing agent was grafted with acrylic acid and N-vinylpyrrolidone to form a modified polymer with good compatibility and stability. When mixed with magnesium aluminum silicate, the thixotropic and temperature-resistant properties of magnesium oxychloride cement were enhanced.
It significantly improves the thixotropic properties of magnesium oxychloride cement under high-temperature conditions, enhances the retention capacity of plugging cement slurry in fractures, forms a stable seal, and ensures the safe and efficient exploitation of oil and gas wells.
Smart Images
Figure CN2025143175_23072026_PF_FP_ABST
Abstract
Description
A temperature-resistant thixotropic agent, its preparation method and application Technical Field
[0001] This invention relates to the field of oil and gas well development technology, specifically to a temperature-resistant thixotropic agent, its preparation method, and its application. Background Technology
[0002] Loss of circulation is becoming increasingly prominent during oil and gas well drilling, especially in fractured formations. The abundance of natural and induced fractures creates large leakage channels and rapid leakage rates, making plugging operations extremely difficult. Traditional plugging materials, such as bridging plugs made of walnut shells and rubber, as well as conventional plugging cement slurries, all have significant drawbacks. Bridging plugs are difficult to adapt to fracture openings, resulting in low plugging efficiency and potential damage to the reservoir. While conventional plugging cement slurries offer high pressure resistance, they cause significant damage to the reservoir, have poor acid solubility, and result in slow recovery of reservoir flow capacity.
[0003] Magnesium oxychloride cement has certain advantages in reservoir plugging due to its rapid setting and good acid solubility. However, in plugging fractured reservoirs, the problem of magnesium oxychloride cement retention in fractures needs to be addressed, thus requiring magnesium oxychloride cement to have strong thixotropic properties. Furthermore, as oil and gas exploration and development expands to deeper formations, high temperatures have become one of the main challenges in drilling and plugging. Currently, there is limited research on thixotropic agents suitable for high-temperature oil and gas well conditions, and most studies are only applicable to silicate cements; research on thixotropic agents suitable for magnesium oxychloride cement is extremely limited. Summary of the Invention
[0004] To address the aforementioned problems, this invention proposes a temperature-resistant thixotropic agent, its preparation method, and its application. This thixotropic agent can significantly improve the thixotropic properties of magnesium oxychloride cement under high-temperature conditions in oil and gas wells.
[0005] The temperature-resistant thixotropic agent of the present invention is prepared by composite of modified sizing agent and magnesium aluminum silicate; the modified sizing agent is prepared by grafting sizing agent with acrylic acid and N-vinylpyrrolidone.
[0006] The specific steps are as follows:
[0007] (1) Mix the precipitate and deionized water and stir until the precipitate is completely dissolved to obtain solution I;
[0008] In this step, high-speed stirring is performed at a speed of 1000 rpm to 2000 rpm until the eutectic gel is completely dissolved to form a uniform solution system. This ensures that the starting materials for subsequent reactions are evenly dispersed, providing a good foundation for the grafting modification reaction.
[0009] (2) Neutralize acrylic acid to a degree of neutralization of 80-85%, add N-vinylpyrrolidone and an initiator, stir to dissolve, and obtain solution II;
[0010] In this step, 17-19 parts of acrylic acid are neutralized to a degree of neutralization of 80-85% using a 5 mol / L sodium hydroxide solution. The neutralization process requires strict control of reaction conditions to ensure the accuracy and stability of the neutralization reaction. After the reaction solution cools to room temperature, 1-3 parts of N-vinylpyrrolidone and 0.10-0.12 parts of an initiator are added. The initiator is one or more of potassium persulfate, ammonium persulfate, and sodium persulfate. After thorough stirring and dissolution, solution II is obtained.
[0011] (3) Add solution II dropwise to solution I. After the dropwise addition is complete, heat the temperature to 65-75℃, keep the temperature and stir the reaction. After the reaction is complete, perform post-processing to obtain modified and optimized adhesive powder.
[0012] In this step, the dropwise addition method helps control the reaction rate, making the reaction more stable and avoiding side reactions or uneven product properties caused by excessively vigorous reaction. Subsequently, the system is heated to 65-75℃, maintained at this temperature, and stirred continuously for 3 hours. During this process, a graft polymerization reaction occurs in the system, generating a modified polymer with specific structure and properties, thereby obtaining the crude product.
[0013] After the reaction, the crude product is washed repeatedly with distilled water and ethanol solution 3-5 times. Distilled water removes water-soluble impurities, and ethanol solution removes organic impurities to thoroughly purify the product and ensure its purity and performance stability. Then, it is dried to constant weight at 50-60℃ to remove moisture. The dried sample is then pulverized into powder and sieved through a 100-300 mesh standard sieve to obtain modified, optimized adhesive powder with a particle size in the range of 48μm to 150μm. A suitable particle size helps it to mix better and more uniformly with magnesium aluminum silicate in subsequent compounding processes, thus exerting a synergistic effect.
[0014] (4) Mix the modified thixotropic adhesive powder with magnesium aluminum silicate evenly to obtain a temperature-resistant thixotropic agent.
[0015] In this step, the ratio of modified thixotropic adhesive powder to magnesium aluminum silicate is 1:(1-2) by mass. The mixing process adopts a sieving method, specifically, the two are placed in a 100-mesh sieve device, and the sieve is vibrated back and forth by a mechanical device. The sieving operation is repeated 5-8 times to ensure that the modified thixotropic adhesive powder and magnesium aluminum silicate can be mixed evenly and fully to obtain a temperature-resistant thixotropic agent.
[0016] In this invention, acrylic acid and N-vinylpyrrolidone are used to graft-modify the adhesive, thereby improving its temperature and salt resistance. The carboxylic acid groups of acrylic acid interact with the components of magnesium oxychloride cement, enhancing compatibility and stability, forming hydrogen bonds and cross-linking structures, strengthening temperature resistance and colloidal strength, and preventing high-temperature deterioration of the cement paste. N-vinylpyrrolidone has good thermal stability, and its five-membered ring structure can improve the temperature and salt resistance of the graft copolymer. Furthermore, its polar groups can form a complex three-dimensional network structure with acrylic acid and the adhesive, enhancing the thixotropic properties and temperature resistance of magnesium oxychloride cement. Magnesium aluminum silicate, with its unique layered crystal structure and large specific surface area, can further optimize the dispersion of modified adhesive in cement slurry and enhance the stability of the system. On the other hand, its excellent adsorption properties can work synergistically with the modified adhesive to better adhere to the fracture surface, forming a more stable and dense sealing structure. This significantly improves the efficiency of the entire system in fractured reservoir plugging operations, ensures the smooth progress of fractured reservoir plugging, and provides strong support for the safe and efficient development of oil and gas wells.
[0017] The thixotropic agent obtained using this invention can be applied to drilling plugging agents and used in conjunction with magnesium oxychloride cement to achieve stable sealing.
[0018] Compared with the prior art, the beneficial effects of the present invention are:
[0019] The thixotropic agent described in this invention possesses good solubility and resistance to temperature and salt, effectively enhancing the thixotropic properties of cement slurry. It exhibits good adaptability to magnesium oxychloride cement and can function stably in the high-temperature environment of oil and gas wells, enhancing the retention capacity of the plugging cement slurry in fractures and forming a stable seal. Furthermore, the preparation method is simple and efficient, and the raw materials are readily available, showing promising prospects for industrial production and promotion. It is expected to effectively solve the problem of well leakage in fractured reservoirs of oil and gas wells and promote the development of oil and gas extraction technology. Attached Figure Description
[0020] Figure 1 shows the infrared spectral analysis of the modified gluten;
[0021] Figure 2 shows the TGA curve of the modified optimized adhesive. Detailed Implementation
[0022] To make the technical advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0023] Comparative Example 1
[0024] Only the thixotropic adhesive was used as the thixotropic agent.
[0025] Comparative Example 2
[0026] Only magnesium aluminum silicate is used as a thixotropic agent.
[0027] Comparative Example 3
[0028] Commercially available bentonite was used as the thixotropic agent.
[0029] Example 1
[0030] The preparation method of the temperature-resistant thixotropic agent includes the following specific steps:
[0031] Add 3g of sorbitol and 150mL of water to a three-necked flask equipped with a stirrer, and stir at high speed until the sorbitol is completely dissolved to obtain solution I.
[0032] 18.18 g of acrylic acid was neutralized with 5 mol / L NaOH solution to achieve a neutralization degree of 82%. After the reaction solution was cooled to room temperature, 1.82 g of N-vinylpyrrolidone and 0.115 g of potassium persulfate were added and stirred to dissolve, resulting in solution II.
[0033] Solution II was slowly and uniformly added dropwise to solution I through a constant-pressure dropping funnel. After the addition was complete, the temperature was raised to 69°C, maintained at this temperature, and stirred continuously for 3 hours to obtain the crude product. After the reaction was completed, the crude product was washed three times successively with sufficient distilled water and ethanol solution to thoroughly remove impurities. Finally, it was dried to constant weight at 60°C, pulverized into powder, and sieved through a 100-mesh standard sieve to obtain modified optimized adhesive powder that met the particle size requirements, labeled as DG-1.
[0034] Place 10g of DG-1 and 10g of magnesium aluminum silicate powder into a sealed plastic bag and shake manually to initially mix the powders evenly. Transfer the initially mixed powder to a vibrating sieve and sieve it five times to achieve uniform and thorough mixing, obtaining the temperature-resistant thixotropic agent product, labeled as T-1.
[0035] Figure 1 shows a Fourier transform infrared (FTIR) spectroscopy scan of a portion of DG-1, indicating that the monomer was successfully grafted onto the optimal gum side chain. Specifically,
[0036] The infrared spectrum of the product shows a value of 3331.71 cm⁻¹. -1 The absorption peak at 2932.89 cm⁻¹ is the stretching vibration absorption peak of OH. -1 The peak at 1667.78 cm⁻¹ is the absorption peak of the asymmetric stretching vibration of CH. -1 The peak at 1454.15 cm⁻¹ is the absorption peak of the stretching vibration of the carbonyl group (C=O). -1 The absorption peak at 1403.21 cm⁻¹ is due to the bending vibration of -CH₂-. -1 The peak at 1289.70 cm⁻¹ represents the stretching vibration absorption peak of the amide group CN on N-vinylpyrrolidone, a characteristic absorption peak of the lactam structure in N-vinylpyrrolidone. -1The peak at 1042.07 cm⁻¹ represents the stretching vibration absorption peak of COC, indicating that the monomer was successfully grafted onto the optimal resin; -1 The absorption peak at this point is the stretching vibration of CO. Additionally, in the infrared spectrum, the absorption peak is located at 1650-1590 cm⁻¹. -1 The absence of an N-H bending vibration absorption peak indicates that the vinyl group in N-vinylpyrrolidone underwent addition polymerization rather than a ring-opening reaction. In conclusion, the monomers acrylic acid and N-vinylpyrrolidone were successfully grafted onto the eutectic resin.
[0037] A portion of DG-1 was subjected to thermogravimetric analysis, and the TGA curves shown in Figure 2 were obtained. The results indicate that the modified, optimized adhesive exhibits good temperature resistance. Specifically,
[0038] The modified gluten undergoes significant mass loss after 400℃, with thermal weight loss mainly occurring in two stages. The first stage primarily involves the endothermic evaporation of free and bound water within the molecules, while the second stage mainly involves the breakage and decomposition of the polysaccharide backbone and branches, as well as the thermal decomposition of the grafted groups.
[0039] Example 2
[0040] The operation steps are basically the same as the preparation process of the modified precipitate powder in Example 1, except that: 17.4g of acrylic acid is neutralized to a degree of neutralization of 85%; 2.6g of N-vinylpyrrolidone is added and the reaction temperature is controlled at 75°C, and finally the modified precipitate powder DG-2 is obtained for later use.
[0041] Weigh 10g of DG-2 and 15g of magnesium aluminum silicate powder at a weight ratio of 1:1.5, and mix them using the same sieving and mixing method as in the preparation of the temperature-resistant thixotropic agent in Example 1 to obtain the finished temperature-resistant thixotropic agent T-2.
[0042] Example 3
[0043] The operation steps are basically the same as the preparation process of the modified precipitate powder in Example 1, except that: 19g of acrylic acid is neutralized to a degree of neutralization of 80%; 1g of N-vinylpyrrolidone is added and the reaction temperature is controlled at 70°C, and finally the modified precipitate powder DG-3 is obtained for later use.
[0044] Weigh 10g of DG-2 and 20g of magnesium aluminum silicate powder in a weight ratio of 1:2, and mix them using the same sieving and mixing method as in the preparation of the temperature-resistant thixotropic agent in Example 1 to obtain the finished temperature-resistant thixotropic agent T-3.
[0045] Test Example 1
[0046] The application effects of the thixotropic agents provided in Comparative Examples 1-3 and the temperature-resistant thixotropic agents prepared in Examples 1-3 in magnesium oxychloride cement were tested using Test Example 1. The specific operation is as follows:
[0047] Cement slurry was prepared according to the preparation method of oil well cement slurry in GB / T 19139-2012: 335 parts lightly calcined magnesium oxide, 243 parts magnesium chloride hexahydrate, 173 parts water, and 10 parts retarder. 1.625 parts of the thixotropic agent provided in Comparative Example 1 were added to the cement-based slurry to obtain cement slurry C1. 6.5 parts of the thixotropic agents provided in Comparative Examples 2 and 3 were added to the cement-based slurry to obtain cement slurries C2 and C3, respectively. 6.5 parts of the temperature-resistant thixotropic agent prepared in Examples 1-3 were added to the cement-based slurry to obtain cement slurries C4-C6.
[0048] The thixotropic properties of cement slurry were characterized by the increase in consistency after the thickener was stopped and restarted. A larger increase indicates better thixotropic properties. Cement slurries C1-C6 at 90℃ were tested using the consistency increase method, and the measurement results are shown in Table 1.
[0049] Table 1. Thixotropic properties of magnesium oxychloride cement slurry containing thixotropic agents at 90℃.
[0050] As shown in Table 1, although the thixotropic agent provided in Comparative Example 1 can significantly enhance the thixotropic properties of cement slurry, its thickening ability is too strong, causing the initial consistency of the cement slurry to reach above 30 Bc, which is not conducive to pumping. In addition, Comparative Example 1 has a high cost, which does not conform to the principle of economy. The thixotropic agents provided in Comparative Examples 2 and 3 have limited effects in the application of magnesium oxychloride cement, and the thixotropic properties of the cement slurry are generally poor.
[0051] The temperature-resistant thixotropic agent prepared in the embodiments of the present invention can not only enhance the thixotropic properties of cement slurry to achieve a good grade, but also ensure that the initial consistency of cement slurry meets the construction requirements, indicating that the temperature-resistant thixotropic agent of the present invention has a better application effect in magnesium oxychloride cement.
[0052] Test Example 2
[0053] The solubility of the thixotropic agent provided in Comparative Example 1 and the temperature-resistant thixotropic agents prepared in Examples 1-3 were tested using Test Example 2. The specific procedures are as follows:
[0054] Weigh 2g of sample and 100mL of deionized water, place them in a 200mL beaker, put the beaker on a magnetic stirrer, set the stirring speed to 300r / min, and record the time required for the sample to completely dissolve. The test results are shown in Table 2.
[0055] Table 2 Dissolution time of each thixotropic agent sample
[0056] As shown in Table 2, the thixotropic agent in Comparative Example 1 has extremely poor solubility. It not only failed to dissolve completely during the stirring time of 240 minutes, but also agglomerated. This indicates that the thixotropic agent has poor affinity with water and is difficult to disperse uniformly in the solution.
[0057] In contrast, the temperature-resistant thixotropic agents prepared in Examples 1-3 had a dissolution time between 14 and 17 minutes, which allowed for relatively complete dissolution and uniform dispersion within a reasonable time. This indicates that the temperature-resistant thixotropic agent prepared in this invention, while ensuring good compatibility with magnesium oxychloride cement, also has good dissolution performance and can stably exert its advantages in improving the thixotropic properties of cement paste and enhancing crack retention capacity in practical applications.
[0058] In summary, the thixotropic agent prepared by the method for preparing magnesium oxychloride cement temperature-resistant thixotropic agent provided in this embodiment of the invention has good solubility and temperature resistance, effectively solving the multiple requirements for thixotropic agents when plugging fractured formations during oil and gas well drilling, and demonstrating the innovation and practicality of this invention in the research and development of magnesium oxychloride cement thixotropic agents.
[0059] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims
1. A method for preparing a temperature-resistant thixotropic agent, characterized in that, The modified thixotropic resin was obtained by grafting acrylic acid and N-vinylpyrrolidone; the modified thixotropic resin was then combined with magnesium aluminum silicate to prepare a temperature-resistant thixotropic agent. By mass ratio, the ratio of ductile adhesive:acrylic acid:N-vinylpyrrolidone is (2-4):(17-19):(1-3); by mass ratio, the ratio of modified ductile adhesive powder:magnesium aluminum silicate is 1:(1-2).
2. The method for preparing the temperature-resistant thixotropic agent according to claim 1, characterized in that, The specific steps are as follows: (1) Mix the precipitate and deionized water and stir until the precipitate is completely dissolved to obtain solution I; (2) Neutralize acrylic acid to a degree of neutralization of 80-85%, add N-vinylpyrrolidone and an initiator, stir to dissolve, and obtain solution II; (3) Add solution II dropwise to solution I. After the dropwise addition is complete, heat the temperature to 65-75℃, keep the temperature and stir the reaction. After the reaction is complete, perform post-processing to obtain modified and optimized adhesive powder. (4) Mix the modified thixotropic adhesive powder with magnesium aluminum silicate evenly to obtain a temperature-resistant thixotropic agent.
3. The method for preparing the temperature-resistant thixotropic agent according to claim 2, characterized in that, By mass ratio, the ratio of ductile adhesive:deionized water:initiator is (2-4):(150-200):(0.10-0.12).
4. The method for preparing the temperature-resistant thixotropic agent according to claim 2, characterized in that, In step (1), the stirring speed is in the range of 1000 rpm to 2000 rpm.
5. The method for preparing the temperature-resistant thixotropic agent according to claim 2, characterized in that, In step (2), the acrylic acid is neutralized with a sodium hydroxide solution with a concentration of 5 mol / L.
6. The method for preparing the temperature-resistant thixotropic agent according to claim 2, characterized in that, The reaction time in step (3) is 3 hours.
7. The method for preparing the temperature-resistant thixotropic agent according to claim 2, characterized in that, In step (3), the particle size of the modified and optimized adhesive powder is 48μm to 150μm.
8. The method for preparing the temperature-resistant thixotropic agent according to claim 2, characterized in that, The mixing process in step (4) uses a sieve mixing method.
9. A temperature-resistant thixotropic agent, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The application of the temperature-resistant thixotropic agent according to claim 9 in well drilling plugging.