A method for preparing a low-density material for cementing

Abstract

The application discloses a preparation method of low-density material for cementing, and comprises the following steps: S1, ball-milling and crushing Basham to obtain Basham powder; S2, modifying epoxy resin with an acrylic monomer mixed solution to obtain water-based acrylic modified epoxy resin, wherein the monomer mixed solution is prepared by mixing methyl methacrylate, acrylic acid, butyl acrylate and benzoyl peroxide tert-butyl ester according to weight portions; S3, diluting the water-based acrylic modified epoxy resin into a water-based acrylic modified epoxy resin solution with deionized water; S4, stirring the Basham powder and the water-based acrylic modified epoxy resin solution to make them uniformly mixed to obtain a mixed solution; and S5, spraying the mixed solution through a spray dryer to obtain the low-density material for cementing. The application can guarantee that the cement sheath of an easy-leakage formation has better integrity, meets the needs of cementing construction under complex conditions, raw materials are cheap and easy to obtain, the production process is controllable, and the application has a wide industrialization prospect.

Description

Technical Field

[0001] This invention relates to a low-density material for cementing, its preparation method and application, belonging to the field of oil well cementing technology. Background Technology

[0002] With the rapid development of the petroleum industry, the demand for cement in oil and gas well cementing projects is constantly increasing. This is especially true due to increased well depth, poor geological conditions, and the growing concern over deep wells, ultra-deep wells, low-pressure wells prone to leakage, and long cemented sections prone to leakage. Ordinary silicate cement is not recommended for interlayer sealing because it is prone to brittle fracture under external forces, leading to serious oil and gas water leakage, waste of oil and gas resources, and environmental impacts such as groundwater pollution and fluid spillage to the surface. Therefore, maintaining the integrity of the underground cement sheath is crucial for ensuring normal oil and gas production and extending the service life of oil and gas wells.

[0003] For blocks with low formation bearing capacity, it is difficult to meet the cementing requirements. To overcome this problem, low-density cement is often used. Low-density cement can reduce fluid column pressure, avoid leakage, and also has a positive effect on reducing pollution caused by setting time. At the same time, the use of low-density cement can also replace two-stage cementing operations to achieve long open hole sealing, which is beneficial to solving the problems of leakage and long sealing sections, and is of great significance to reservoir protection.

[0004] Currently, there are two methods for preparing low-density cement slurry: The first method involves adding hollow glass microspheres, fly ash, or cenospheres to oil well cement, thereby reducing the density of the cement slurry through the inherently low density of these materials. While this method is fast and effective in reducing density, hollow glass microspheres can affect the compressive strength of the cement slurry system at low temperatures, and it is also costly. Fly ash cement slurry has limited density and poor strength and water separation properties. Cenospheres have poor compressive strength and are easily broken under pressure, resulting in a true density that is relatively much higher than the ground density. The second method involves adding a single highly absorbent lightweight inorganic admixture, such as bentonite, diatomaceous earth, or expanded perlite, to the cement to increase the water-to-solid ratio of the cement slurry system, thereby reducing the density of the cement slurry system to 1.40–1.60 g / cm³. 3 However, low-density systems with a single admixture all have minimum density limits; for example, the minimum density of bentonite cement slurry is 1.6 g / cm³. 3 The minimum density of diatomaceous earth cement slurry is 1.5 g / cm³. 3 Furthermore, its compressive strength is relatively low. In addition, the density of the weight-reducing material in low-density cement slurry differs significantly from that of cement, resulting in unstable slurry performance. This leads to cement particles settling and weight-reducing materials floating, causing slurry stratification and severely affecting cementing quality. Therefore, the settling stability of ultra-low density cement slurry is an important performance indicator.

[0005] If blocks with low formation pressure capacity cannot meet cementing quality standards, they cannot meet the requirements for reservoir stimulation and perforation of oil and gas sections. Due to this constraint, blocks with low pressure capacity typically employ forward injection and reverse squeeze cementing techniques to ensure high cement return, which can easily result in empty sections in some wells and poor cementing quality in low-density sections.

[0006] Low-density cement rings experience complex alternating loads during subsequent production processes, causing stress variations. When the stress exceeds these limits, cracks and voids form inside and on the surface of the cement ring, potentially leading to its integrity failure.

[0007] Currently, many scholars both domestically and internationally are studying densities less than 1.40 g / m³. 3 Extensive research has been conducted on cement grout systems, but the problems of low cement stone performance, high application costs, and poor sealing effect have not been well resolved.

[0008] To ensure the integrity of cement sheaths in easily lost formations, save costs, and maximize the economic benefits of exploration and development, researching new low-density cement materials is of great significance. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing low-density cementing materials. This method is based on reliable principles. By adding balsa wood to reduce the density of the cement slurry, the thickening time of the cement slurry can be adjusted, ensuring that the cement sheath has good integrity and meeting the needs of cementing construction under complex conditions. The raw materials are inexpensive and readily available, and the production process is controllable, thus having broad prospects for industrialization.

[0010] To achieve the above technical objectives, the present invention adopts the following technical solution.

[0011] A method for preparing a low-density cementing material includes the following steps:

[0012] S1. Balsa wood is ball-milled to obtain balsa wood powder;

[0013] S2. Modify epoxy resin with acrylic monomer mixture to obtain waterborne acrylic modified epoxy resin. The acrylic monomer mixture refers to a monomer mixture obtained by mixing methyl methacrylate, acrylic acid, butyl acrylate and tert-butyl peroxide in a certain weight ratio.

[0014] S3. Dilute the waterborne acrylic modified epoxy resin with deionized water to prepare a waterborne acrylic modified epoxy resin solution.

[0015] S4. Stir the balsa wood powder and the water-based acrylic modified epoxy resin solution until they are mixed evenly to obtain a mixed solution.

[0016] S5. The mixed solution is spray-dried using a spray dryer to obtain a low-density cementing material.

[0017] In the above preparation method, in step S1, the balsa wood powder has an average particle size of 100-400 mesh and a density of 0.05-0.15 g / cm³. 3 .

[0018] In the above preparation method, the preparation process of the waterborne acrylic modified epoxy resin in step S2 is as follows:

[0019] 1) Methyl methacrylate, acrylic acid, butyl acrylate, and tert-butyl peroxide are mixed in parts by weight of 120-200, 10-100, 120-225, and 3-15, respectively, to obtain a monomer mixture.

[0020] 2) Add 500-1000 parts by weight of epoxy resin to the reaction flask, heat to 120-130℃, then drop the monomer mixture into the reaction flask over a period of 2-3 hours, and then keep warm at 120-130℃ for 1-2 hours.

[0021] 3) Add 2-5 parts by weight of benzoyl tert-butyl peroxide, keep warm at 120-130℃ for 1-2 hours, and then lower the temperature to 60℃ to obtain waterborne acrylic modified epoxy resin.

[0022] In the above preparation method, in step S2, the viscosity of the waterborne acrylic modified epoxy resin is 200-600 mPa·s, the solid content is 70%, and the pH is 7-10.

[0023] In the above preparation method, in step S3, the mass ratio of deionized water to waterborne acrylic modified epoxy resin is 90-100:4-10.

[0024] In the above preparation method, in step S4, the mass ratio of the aqueous acrylic modified epoxy resin solution to balsa wood powder is 80-100:40-60; the stirring temperature is room temperature, and the stirring time is 60-80 min.

[0025] In the above preparation method, the spray drying conditions in step S5 are as follows:

[0026] The inlet air temperature is 100-120℃, the outlet air temperature is 30-40℃, and the maximum evaporation rate is 1500-2000 mL / h.

[0027] The feeding method is peristaltic pump regulation, and the maximum feed rate of the peristaltic pump is 500-800 mL / h;

[0028] The electric heater has a power rating of 3.5KW and operates on AC220V single-phase grounding.

[0029] Fan: Power 0.4KW, air flow rate 4.5m³ / h 3 / min, wind pressure is 500Pa;

[0030] The air compressor has a power of 0.6KW and an air production capacity of 3.2m³. 3 / h;

[0031] The compressed air working pressure is 2-5 Bar, and the nozzle diameter is 0.75 mm.

[0032] The low-density cementing material prepared by the above method is also within the scope of protection of this invention.

[0033] Adding the low-density material to oil well cement results in a low-density cement slurry system that effectively prevents leakage and solves the problem of cementing long sealing sections.

[0034] The amount of low-density material added is 5% to 25% of the mass of the oil well cement.

[0035] The oil well cement is either Grade G oil well cement or silicate cement, both of which are the most commonly used cements in oil and gas cementing operations.

[0036] In preparing cement slurry, conventional admixtures and additives, such as toughening agents, fluid loss reducers, defoamers, and self-healing agents, need to be added, depending on specific needs.

[0037] The cement slurry with added low-density material is particularly suitable for cementing environments with stringent requirements for gas channeling prevention and cement sheath integrity, such as deep wells, ultra-deep wells, and low-pressure wells prone to leakage. It can not only seal wells prone to leakage and isolate long cementing sections prone to leakage for a long time, but also reduce the occurrence of gas channeling.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The low-density material involved in this invention uses balsa wood as raw material, which is lightweight and has a low density of only 0.05 to 0.15 g / cm³. 3 Balsa wood has a porous internal structure, which can absorb moisture from cement, thus producing a thickening effect. Balsa wood is also inexpensive and readily available.

[0040] (2) The low-density material involved in this invention uses water-based acrylic epoxy resin as a solvent, which has good hydrophilicity and good compatibility with cement slurry. It can fill the micropores of balsa wood to the maximum extent, reduce the density of cement slurry, and shorten the thickening time to 330 min.

[0041] (3) The low-density material involved in this invention is dried by spray dryer, which has a fast drying speed, good material dispersibility, and simple and controllable drying process, which enables the material to be better compatible with cement slurry, thereby preventing "gas channeling" and ensuring the integrity of the cement ring.

[0042] (4) The preparation method described in this invention is technically reliable, has a high yield, and has low requirements for the quality of raw materials. The prepared products have high uniformity, good chemical stability, and strong hydration ability, making them suitable for large-scale industrial production. Attached Figure Description

[0043] Figure 1 This is the cement slurry thickening curve of Example 1 at 104℃*50MPa*52min.

[0044] Figure 2 This is the cement slurry thickening curve of Example 2 at 104℃*50MPa*52min.

[0045] Figure 3 This is the cement slurry thickening curve of Example 3 at 104℃*50MPa*52min.

[0046] Figure 4 This is the cement slurry thickening curve of the blank group at 104℃*50MPa*52min. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and examples to enable those skilled in the art to understand the invention. However, it should be understood that the present invention is not limited to the specific embodiments described herein. For those skilled in the art, any variations that fall within the spirit and scope of the invention as defined and determined by the appended claims are all within the scope of protection.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0049] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0050] Example 1

[0051] (1) Crushing of balsa wood: Balsa wood with a density of 0.1 g / cm³ was selected. 3 Balsa wood was pulverized using a ball mill to control the particle size to 200 mesh.

[0052] (2) Preparation of waterborne acrylic modified epoxy resin: 1) Methyl methacrylate, acrylic acid, butyl acrylate and tert-butyl peroxide were mixed in weight parts of 140, 50, 120 and 3 respectively to obtain a monomer mixture; 2) 500 parts by weight of epoxy resin were added to the reaction bottle and heated to 120°C. Then the monomer mixture was added dropwise to the reaction bottle for 2 hours. The mixture was then kept at 120°C for 1 hour; 3) 2 parts by weight of tert-butyl peroxide were added. The mixture was kept at 120°C for 1 hour and then cooled to 60°C to obtain waterborne acrylic modified epoxy resin.

[0053] (3) Diluting the waterborne acrylic modified epoxy resin: The viscosity of the obtained waterborne acrylic modified epoxy resin is 250 mPa·s, the solid content is 70%, and the pH is 8. After mixing the waterborne acrylic modified epoxy resin with deionized water at a mass ratio of 4:90, the mixture is stirred at room temperature for 60 min to obtain the waterborne acrylic modified epoxy resin solution.

[0054] (4) Preparation of mixed solution: Pour balsa wood powder into water-based acrylic modified epoxy resin solution and mix evenly. The mass ratio of the two is 44:80.

[0055] (5) Spray drying: The mixed solution of balsa wood and water-based acrylic modified epoxy resin is placed into a spray dryer for drying to obtain a low-density material for cementing.

[0056] The relevant parameters are as follows:

[0057]

[0058]

[0059] Example 2

[0060] (1) Crushing of balsa wood: Balsa wood with a density of 0.08 g / cm³ was selected. 3 Balsa wood was pulverized using a ball mill to control the particle size to 300 mesh.

[0061] (2) Preparation of waterborne acrylic modified epoxy resin: 1) Methyl methacrylate, acrylic acid, butyl acrylate and benzoyl tert-butyl peroxide were mixed in weights of 200, 10, 180 and 10 respectively to obtain a monomer mixture; 2) 800 parts by weight of epoxy resin were added to the reaction bottle and heated to 125°C. Then the monomer mixture was added dropwise to the reaction bottle for 2.5 hours. The mixture was then kept at 125°C for 1.5 hours; 3) 3 parts by weight of benzoyl tert-butyl peroxide were added. The mixture was kept at 125°C for 1 hour and then cooled to 60°C to obtain waterborne acrylic modified epoxy resin.

[0062] (3) Diluting the waterborne acrylic modified epoxy resin: The viscosity of the obtained waterborne acrylic modified epoxy resin is 500 mPa·s, the solid content is 70%, and the pH is 8.5. After mixing the waterborne acrylic modified epoxy resin with deionized water at a mass ratio of 6:98, the mixture is stirred at room temperature for 70 min to obtain the waterborne acrylic modified epoxy resin solution.

[0063] (4) Preparation of mixed solution: Pour balsa wood powder into water-based acrylic modified epoxy resin solution and mix evenly. The mass ratio of the two is 40:90.

[0064] (5) Spray drying: The mixed solution of balsa wood and water-based acrylic modified epoxy resin is placed into a spray dryer for drying to obtain a low-density material for cementing.

[0065] The relevant parameters are as follows:

[0066]

[0067] Example 3

[0068] (1) Crushing of balsa wood: Balsa wood with a density of 0.12 g / cm³ was selected. 3 Balsa wood was pulverized using a ball mill to control the particle size to 150 mesh.

[0069] (2) Preparation of waterborne acrylic modified epoxy resin: 1) Methyl methacrylate, acrylic acid, butyl acrylate and tert-butyl peroxide were mixed in weight parts of 160, 30, 225 and 10 respectively to obtain a monomer mixture; 2) 1000 parts by weight of epoxy resin were added to the reaction bottle and heated to 130°C. Then the monomer mixture was added dropwise to the reaction bottle for 3 hours. The mixture was then kept at 125°C for 2 hours; 3) 5 parts by weight of tert-butyl peroxide were added. The mixture was kept at 130°C for 2 hours and then cooled to 60°C to obtain waterborne acrylic modified epoxy resin.

[0070] (3) Diluting the waterborne acrylic modified epoxy resin: The waterborne acrylic modified epoxy resin has a viscosity of 400 mPa·s, a solid content of 70%, and a pH of 9. After mixing the waterborne acrylic modified epoxy resin with deionized water at a mass ratio of 8:95, the mixture is stirred at room temperature for 80 min to obtain a waterborne acrylic modified epoxy resin solution.

[0071] (4) Preparation of mixed solution: Pour balsa wood powder into water-based acrylic modified epoxy resin solution and mix evenly. The mass ratio of the two is 50:95.

[0072] (5) Spray drying: The mixed solution of balsa wood and water-based acrylic modified epoxy resin is placed into a spray dryer for drying to obtain a low-density material for cementing.

[0073] The relevant parameters are as follows:

[0074]

[0075] The prepared cement slurry was tested for its basic properties, including density, fluidity, compressive strength at 92℃ for 48 hours, and API water loss at 104℃ for 6.9 MPa for 30 minutes. The results are shown in Table 1.

[0076] Table 1. Test results of basic properties of cement paste

[0077]

[0078] As cementing depth increases and geological conditions deteriorate, deep wells, ultra-deep wells, and low-pressure wells prone to leakage are more likely to occur. Under external forces, the cement slurry system is susceptible to brittle fracture, leading to severe oil, gas, and water leakage. Table 1 shows that the density of cement slurry without added low-density materials is 1.9 g / cm³. 3 The cement slurry exhibits a flowability of 240 mm, a compressive strength of 13.6 MPa, and an API fluid loss of 50 mL. Furthermore, the cement slurry containing the low-density material provided by this invention has a density of 1.2 g / cm³. 3 1.4g / cm 3 1.6g / cm 3 Compared to blank cement slurry (1.9 g / cm³), 3 The density is significantly reduced and adjustable, while the minimum limiting density of common low-density materials such as fly ash, slag, and bentonite is 1.5 g / cm³. 3 Although the density of the cenosphere cement slurry system can reach 1.3 g / cm³ 3 However, it is fragile and easily affected by raw materials, making it unsuitable for long cementing sections. Its 48-hour compressive strength increases with density, and its flowability is consistently above 200 mm, meeting construction requirements. Under conditions of 104℃*6.9MPa*30min, the API water loss is less than 50 mL, the mud cake is dense, and the permeability is low.

[0079] The low-density materials used in the above-mentioned oil well cement slurry were formulated for cementing as shown in Table 2. In Table 2, all percentages are by mass relative to the oil well cement. High-sulfur-resistant G-grade cement was provided by Jiahua Special Cement Co., Ltd., while the fluid loss reducer FL-33, expansion agent FE-41, toughening agent FT-43, self-healing agent FS-46, drag reducer GD-1, anti-settling agent FA-2, anti-corrosion and anti-channeling resin FC-1, retarder FR-9, and defoamer FR-R were all provided by Henan Weihui Chemical Co., Ltd. Cement slurry and cement stone were prepared according to GB / T19139-2012 "Test Methods for Oil Well Cement".

[0080] Table 2. Cement Slurry Formulation for Oil Well Cement Cementing

[0081]

[0082] The thickening curves of Examples 1-3 are as follows: Figures 1-3 As shown, Figure 4 The thickening curve is shown without the addition of low-density materials.

[0083] Through analysis Figures 1-4 The results show that: without the addition of low-density materials, the cement slurry, under thickening conditions of 104℃*50MPa*52min, maintained stable temperature and pressure, and the thickening curve showed no obvious abnormalities, exhibiting a smooth trend and right-angle thickening. With the addition of low-density materials, the thickening time of the cement slurry could be shortened to 330min, and the thickening time was adjustable. Furthermore, the cement slurry showed no "flash setting" or "core formation" phenomena, indicating that the addition of this low-density material can maximize the filling of micropores, reduce the density of the cement slurry, effectively prevent "gas channeling," and ensure the integrity of the cement sheath.

Claims

1. A method for preparing a low-density cementing material, comprising the following steps: S1. Balsa wood is ball-milled to obtain balsa wood powder; S2. Modify epoxy resin with acrylic monomer mixture to obtain waterborne acrylic modified epoxy resin. The acrylic monomer mixture refers to a monomer mixture obtained by mixing methyl methacrylate, acrylic acid, butyl acrylate and tert-butyl peroxide in parts by weight. S3. Dilute the waterborne acrylic modified epoxy resin with deionized water to prepare a waterborne acrylic modified epoxy resin solution. S4. Stir the balsa wood powder and the water-based acrylic modified epoxy resin solution until they are mixed evenly to obtain a mixed solution. S5. The mixed solution is spray-dried using a spray dryer to obtain a low-density cementing material.

2. The method for preparing a low-density cementing material as described in claim 1, characterized in that, In step S1, the balsa wood powder has an average particle size of 100-400 mesh and a density of 0.05-0.15 g / cm³. 3 .

3. The method for preparing a low-density cementing material as described in claim 1, characterized in that, In step S2, the preparation process of the waterborne acrylic modified epoxy resin is as follows: 1) Methyl methacrylate, acrylic acid, butyl acrylate, and tert-butyl peroxide are mixed in parts by weight of 120-200, 10-100, 120-225, and 3-15, respectively, to obtain a monomer mixture. 2) Add 500-1000 parts by weight of epoxy resin to the reaction flask, heat to 120-130 ℃, then drop the monomer mixture into the reaction flask over a period of 2-3 h, and then keep warm at 120-130 ℃ for 1-2 h. 3) Add 2-5 parts by weight of benzoyl tert-butyl peroxide, keep warm at 120-130 ℃ for 1-2 h, and then lower the temperature to 60 ℃ to obtain waterborne acrylic modified epoxy resin.

4. A method for preparing a low-density cementing material as described in claim 3, characterized in that, In step S2, the waterborne acrylic modified epoxy resin has a viscosity of 200~600 mPa·s, a solid content of 70%, and a pH of 7~10.

5. The method for preparing a low-density cementing material as described in claim 1, characterized in that, In step S3, the mass ratio of deionized water to waterborne acrylic modified epoxy resin is 90~100:4~10.

6. The method for preparing a low-density cementing material as described in claim 1, characterized in that, In step S4, the mass ratio of the aqueous acrylic modified epoxy resin solution to balsa wood powder is 80~100:40~60.

7. The application of the low-density cementing material prepared by the preparation method according to any one of claims 1-6, characterized in that, The prepared low-density cementing material is added to oil well cement to obtain cementing slurry, which is suitable for deep wells, ultra-deep wells or low-pressure wells prone to leakage.

8. The application as described in claim 7, characterized in that, The amount of low-density material added is 5-25% of the mass of the oil well cement.

9. The application as described in claim 7, characterized in that, The oil well cement is Grade G oil well cement.

10. The application as described in claim 7, characterized in that, Conventional admixtures and additives also need to be added to the cement slurry, depending on specific needs.

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