Clay stabilizer containing cationic polymer and preparation method thereof

Abstract

The invention relates to a clay stabilizer containing a cationic polymer and a preparation method thereof, and belongs to the technical field of oilfield chemistry. The preparation method comprises the following steps: uniformly mixing tetramethylethylenediamine, 1, 3-dichloro-2-propanol and a hydrogen bond donor, heating to a first temperature, reacting for a first time period at the first temperature, then heating to a second reaction temperature, reacting for a second time period at the second temperature, and stopping the reaction to obtain the clay stabilizer containing the cationic polymer. The clay stabilizer comprises a cationic polymer and a hydrogen bond donor which are formed by reacting tetramethylethylenediamine with 1, 3-dichloro-2-propanol, and the cationic polymer and the hydrogen bond donor form an ionic liquid solvent, so that the clay stabilizer disclosed by the invention does not need to use volatile, inflammable and explosive organic solvents; the preparation method is simple, the reaction process is safe and controllable, and the method is suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and particularly relates to a clay stabilizer containing a cationic polymer and a preparation method thereof. Background Art

[0002] During oil and gas production and water injection operations, clay minerals in the formation (such as montmorillonite, illite, and kaolinite) are prone to hydration swelling and dispersion migration upon contact with water. This can lead to decreased reservoir permeability, reduced wellbore stability, and in severe cases, even wellbore collapse or reduced oil production. According to statistics, approximately 70% of oil and gas reservoirs worldwide experience varying degrees of clay damage, directly impacting the efficiency and economic viability of oil and gas field development. Therefore, clay stabilizers are often added to wellbore fluids to prevent hydration swelling and dispersion migration. Clay particles typically have a negative surface charge, while the positively charged cations in clay stabilizers create a strong electrostatic attraction between the two, creating a strong adsorption effect that slows the penetration of water molecules and prevents hydration swelling, thereby inhibiting the clay particles' swelling.

[0003] Early clay stabilizers used inorganic salts such as KCl and NH₄Cl to inhibit clay hydration through ion exchange. However, these required large dosages, had short-lived effects, and high concentrations were prone to corrosion of equipment and could negatively impact wellbore fluid properties. Hydroxyaluminum or zirconium hydroxylates were used in the 1960s and 1970s, but these stabilizers suffered from poor heat and acid resistance. More recently, quaternary ammonium surfactants, polyamines, and polyquaternary ammonium salts have become common. While these stabilizers offer excellent anti-swelling properties, they also present certain challenges. Polyamine-based stabilizers are complex to produce, exhibit poor water washability, and have a short shelf life. Polyquaternary ammonium-based stabilizers have high molecular weights, making them unsuitable for use in low-permeability reservoirs and potentially exacerbating permeability issues. Quaternary ammonium surfactants can make the reservoir oil-wet, reducing oil-phase permeability and hindering crude oil recovery. Furthermore, these types of stabilizers, particularly polyacrylamide, exhibit poor compatibility with fracturing fluids, significantly reducing the viscosity of the fracturing fluid system, impacting sand-carrying performance, and increasing sand addition difficulties.

[0004] In recent years, researchers have focused on developing composite clay stabilizers to enhance performance through synergistic effects (e.g., cation-anion combinations and nanomaterial modification). However, existing composite systems still suffer from complex formulations, poor stability, and high costs. There is an urgent need for a new, highly effective, long-lasting, and environmentally friendly clay stabilizer. Summary of the Invention

[0005] In view of the above problems, the present invention provides a clay stabilizer containing a cationic polymer and a preparation method thereof.

[0006] The first object of the present invention is to provide a method for preparing a clay stabilizer containing a cationic polymer, comprising: After tetramethylethylenediamine, 1,3-dichloro-2-propanol and a hydrogen bond donor are uniformly mixed, the temperature is raised to a first temperature, and the reaction is carried out at the first temperature for a first time period. The temperature is then raised to a second reaction temperature, and the reaction is carried out at the second temperature for a second time period. The reaction is stopped to obtain a clay stabilizer containing a cationic polymer.

[0007] In a specific embodiment of the present invention, the hydrogen bond donor is one or more of urea, ethylene glycol and glycerol; In a specific embodiment of the present invention, the first temperature is 40-60° C., and the first time period is 4-8 hours. Preferably, the first temperature is 50° C. or 60° C., and the first time period is 8 hours.

[0008] In a specific embodiment of the present invention, the second temperature is 80-100° C., and the second time period is 6-24 hours. Preferably, the second temperature is 80° C., 90° C., or 100° C., and the second time period is 12 hours or 24 hours.

[0009] In a specific embodiment of the present invention, the molar ratio of the 1,3-dichloro-2-propanol, tetramethylethylenediamine, and hydrogen bond donor is 0.8-1.0:1:1-4.

[0010] In a specific embodiment of the present invention, during the stopping reaction, water is added and stirred evenly.

[0011] In a specific embodiment of the present invention, the molar ratio of tetramethylethylenediamine to water is 1:0~2.

[0012] A second object of the present invention is to provide a clay stabilizer containing a cationic polymer, which is prepared by the following steps: After tetramethylethylenediamine, 1,3-dichloro-2-propanol and a hydrogen bond donor are uniformly mixed, the temperature is raised to a first temperature, and the reaction is carried out at the first temperature for a first time period. The temperature is then raised to a second reaction temperature, and the reaction is carried out at the second temperature for a second time period. The reaction is stopped to obtain a clay stabilizer containing a cationic polymer.

[0013] In a specific embodiment of the present invention, the clay stabilizer has an anti-swelling rate ≥85%, a water-washing anti-swelling rate ≥85%, a jelly viscosity retention rate ≥90%, and a temperature resistance of 300°C.

[0014] Beneficial effects of the present invention: The present invention provides a clay stabilizer containing a cationic polymer and a preparation method thereof. The clay stabilizer comprises a cationic polymer formed by reacting tetramethylethylenediamine with 1,3-dichloro-2-propanol and a hydrogen bond donor, wherein the cationic polymer and the hydrogen bond donor form an ionic liquid solvent. The preparation process of the stabilizer comprises directly mixing tetramethylethylenediamine, 1,3-dichloro-2-propanol and the hydrogen bond donor, reacting the tetramethylethylenediamine with 1,3-dichloro-2-propanol without the hydrogen bond donor participating in the reaction, and immediately reacting the cationic polymer generated by the reaction of the tetramethylethylenediamine and 1,3-dichloro-2-propanol with the hydrogen bond donor to form the ionic liquid solvent. It can be seen that the preparation process of the stabilizer is synchronized with the formation process of the cationic polymer, without the use of volatile, flammable, and explosive organic solvents. The preparation method is simple, the reaction process is safe and controllable, and the stabilizer is suitable for large-scale production. The cationic polymer in the present invention is a highly polar molecule containing multiple cations and hydroxyl groups, with a high charge density and a significant effect in preventing clay swelling; it has many adsorption sites and a strong ability to withstand water washing; In the present invention, water can be introduced into the preparation process of the stabilizer to form a water-containing stabilizer; The clay stabilizer of the present invention has strong temperature resistance and can be used in high-temperature and ultra-high-temperature reservoirs; The clay stabilizer of the present invention has little effect on the viscosity of the guar gum fracturing fluid, can ensure the sand-carrying performance of the fracturing fluid, and can be used for low-permeability and ultra-low-permeability reservoir reconstruction or water injection development.

[0015] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained by the structures pointed out in the description and claims. DETAILED DESCRIPTION

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0017] A method for preparing a clay stabilizer containing a cationic polymer according to an embodiment of the present invention includes: After tetramethylethylenediamine, 1,3-dichloro-2-propanol and a hydrogen bond donor are uniformly mixed, the temperature is raised to a first temperature, and the reaction is carried out at the first temperature for a first time period. The temperature is then raised to a second reaction temperature, and the reaction is carried out at the second temperature for a second time period. The reaction is stopped to obtain a clay stabilizer containing a cationic polymer.

[0018] Example 1: 12.0 g of tetramethylethylenediamine, 12.9 g of 1,3-dichloro-2-propanol and 12.0 g of urea were mixed evenly, reacted at 60° C. for 8 h and then at 100° C. for 24 h. 3.1 g of tap water was added to terminate the reaction, and the mixture was stirred evenly to obtain a clay stabilizer containing a cationic polymer.

[0019] Example 2: 12.0 g of tetramethylethylenediamine, 12.9 g of 1,3-dichloro-2-propanol and 12.4 g of ethylene glycol were mixed evenly, reacted at 60° C. for 8 h and then at 90° C. for 12 h. 2.7 g of tap water was added to terminate the reaction, and the mixture was stirred evenly to obtain a clay stabilizer containing a cationic polymer.

[0020] Example 3: 12.0 g of tetramethylethylenediamine, 12.9 g of 1,3-dichloro-2-propanol, 6.0 g of urea and 6.2 g of ethylene glycol were mixed evenly, reacted at 50° C. for 8 h and then at 90° C. for 12 h. 2.9 g of tap water was added to terminate the reaction, and the mixture was stirred evenly to obtain a clay stabilizer containing a cationic polymer.

[0021] Example 4: 12.0 g of tetramethylethylenediamine, 12.9 g of 1,3-dichloro-2-propanol, 12.0 g of urea and 12.4 g of ethylene glycol were mixed evenly, reacted at 50° C. for 6 h, then at 80° C. for 12 h, cooled to room temperature, and stirred evenly to obtain a clay stabilizer containing a cationic polymer.

[0022] Example 5: 12.0 g of tetramethylethylenediamine, 12.9 g of 1,3-dichloro-2-propanol, 9.2 g of propylene glycol and 6.2 g of ethylene glycol were mixed evenly, reacted at 50° C. for 6 h, then at 80° C. for 12 h, cooled to room temperature, and stirred evenly to obtain a clay stabilizer containing a cationic polymer.

[0023] Comparative Example 1: 12.0 g of tetramethylethylenediamine and 12.9 g of 1,3-dichloro-2-propanol were dissolved in 100 mL of anhydrous ethanol, and the mixture was refluxed at 60°C for 8 h and then at 80°C for 12 h. The solvent was recovered by rotary evaporation, precipitated with ethyl acetate, filtered, and vacuum dried to obtain a white solid, which was the cationic polymer, with a yield of 98.6%.

[0024] Performance Testing The evaluation method refers to SY / T5971-2024 "Performance Evaluation Method of Clay Stabilizers for Oil and Gas Field Fracturing, Acidizing and Water Injection", and the centrifuge method is used to test the anti-swelling rate, water washability and viscosity retention rate.

[0025] Test Example 1 Evaluation of the Anti-swelling Rate of Clay Stabilizer Take 0.5g of clay stabilizer and add 100g of distilled water and shake well to obtain a clay stabilizer solution. Weigh 0.50g of sodium bentonite and place it into a 10mL centrifuge tube. Add 10mL of clay stabilizer solution and shake well. Let it stand at room temperature for 2 hours. Place it in a centrifuge and centrifuge at 1500r / min for 15 minutes. Read the volume V1 of the expanded sodium bentonite.

[0026] The volume of sodium bentonite after expansion is V2 after replacing the clay stabilizer solution with distilled water.

[0027] The volume of sodium bentonite after expansion is V0 when kerosene is used to replace the clay stabilizer solution.

[0028] The calculation of the anti-swelling rate B is shown in formula (1): (1) Test Example 2 Evaluation of the water washability of clay stabilizers Discard the supernatant in the centrifuge tube after centrifugation in Test Example 1, add 10 mL of distilled water, shake thoroughly, let stand for 2 hours, put into a centrifuge, and centrifuge at a speed of 1500 r / min for 15 minutes. Repeat the above operation twice, read the volume of the sodium bentonite after expansion, and calculate the anti-swelling rate in the same way as in Test Example 1.

[0029] Test Example 3 Evaluation of Jelly Viscosity Retention of Clay Stabilizer 1000 mL of 0.4% hydroxypropyl guar gum fracturing fluid base fluid was prepared and divided into two equal parts, one of which was a blank sample and the other was added with 0.7% by mass of clay stabilizer.

[0030] The fracturing fluid cross-linking fluid formula is prepared with a mass fraction of 3.0% sodium tetraborate and a mass fraction of 10.0% sodium hydroxide.

[0031] Two parts of fracturing fluid base fluid are prepared into fracturing fluid gel according to the cross-linking ratio required by the test or a cross-linking ratio of 100:1, and then the apparent viscosity of the two gel samples at 90°C is measured respectively.

[0032] The calculation of the jelly viscosity retention rate is shown in formula (2): (2) In formula (2), y1 is the viscosity retention rate, expressed as a percentage; η2 is the apparent viscosity after adding clay stabilizer, mPa·s; η1 is the apparent viscosity of the blank sample, mPa·s.

[0033] The test results of the jelly viscosity retention rate of the clay stabilizer of the present invention are shown in Table 1.

[0034] The clay stabilizer solution was placed in a sealed container for high temperature and high pressure heat treatment and heat treated at 300°C for 2 hours. The above operation was repeated to test the temperature resistance of the clay stabilizer. The test results are shown in Table 1.

[0035] Table 1 Test results

[0036] The test results show that the clay stabilizer prepared by the present invention has an anti-swelling rate of ≥85%, a water-washing anti-swelling rate of ≥85%, a jelly viscosity retention rate of ≥90%, and a temperature resistance of up to 300°C. It has excellent performance and can be used for fracturing and reconstruction of high-temperature, ultra-high-temperature low-permeability, and ultra-low-permeability reservoirs. Compared with the clay stabilizer in Comparative Example 1 (which is a pure cationic polymer), the clay stabilizer prepared by the present invention (including a cationic polymer and a hydrogen bond donor, or including a cationic polymer, a hydrogen bond donor, and water) has a simpler preparation method and a lower price. While reducing the amount of cationic polymer used, it still has good anti-swelling rate and water-washing anti-swelling rate, and has better compatibility with guar gum fracturing fluid.

[0037] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a clay stabilizer containing a cationic polymer, characterized in that: include: After uniformly mixing tetramethylethylenediamine, 1,3-dichloro-2-propanol and a hydrogen bond donor, heating to a first temperature, reacting at the first temperature for a first time period, then heating to a second reaction temperature, reacting at the second temperature for a second time period, and stopping the reaction to obtain a clay stabilizer containing a cationic polymer; The hydrogen bond donor is one or more of urea, ethylene glycol and glycerol; The first temperature is 40-60° C., and the first time period is 4-8 hours; The second temperature is 80-100° C., and the second time period is 6-24 hours.

2. The method for preparing a clay stabilizer containing a cationic polymer according to claim 1, wherein: The first temperature is 50°C or 60°C.

3. The method for preparing a clay stabilizer containing a cationic polymer according to claim 1, characterized in that: The first time period is 8 hours.

4. The method for preparing a clay stabilizer containing a cationic polymer according to claim 1, wherein: The second temperature is 80°C, 90°C or 100°C.

5. The method for preparing a clay stabilizer containing a cationic polymer according to claim 1, characterized in that: The second time period is 12 hours or 24 hours.

6. The method for preparing a clay stabilizer containing a cationic polymer according to claim 1, characterized in that: The molar ratio of the 1,3-dichloro-2-propanol, tetramethylethylenediamine and hydrogen bond donor is 0.8-1.0:1:1-4.

7. The method for preparing a clay stabilizer containing a cationic polymer according to any one of claims 1 to 6, characterized in that: During the stopping reaction process, water was added and the mixture was stirred evenly.

8. The method for preparing a clay stabilizer containing a cationic polymer according to claim 7, characterized in that: The molar ratio of tetramethylethylenediamine to water is 1:0-2.

9. A clay stabilizer containing a cationic polymer, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. The clay stabilizer containing a cationic polymer according to claim 9, characterized in that: The clay stabilizer has an anti-swelling rate of ≥85%, an anti-swelling rate after washing of ≥85%, and a jelly viscosity retention rate of ≥90%.

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