Early strength agent for improving mechanical properties of cementing cement and preparation method thereof

Abstract

The application belongs to the technical field of oil field chemistry, and particularly relates to an early strength agent for improving the mechanical properties of well cementing cement and a preparation method thereof. The early strength agent for improving the mechanical properties of well cementing cement comprises modified carbon nanomaterial, polycarboxylic acid polymer, inorganic salt, non-ionic surfactant and water. The early strength agent is a water-based suspension based on carbon nanomaterial, which can effectively promote the early compressive strength development of cement stone at a low dosage when used in well cementing cement slurry, and exhibits excellent early strength effect. Meanwhile, the early strength agent has no adverse effect on the long-term strength development of cement stone, and can improve the mechanical properties such as the elastic modulus of cement stone, so that the cement sheath can still obtain good comprehensive mechanical properties without additional elastic materials, and meet the application requirements of multifunctional early strength agent for deep water surface well cementing construction.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to an early-strength agent for improving the mechanical properties of cementing and its preparation method. Background Technology

[0002] As oil and gas exploration and development continue to advance into deeper water and deeper formations, higher requirements are placed on the performance of cement sheaths. On the one hand, it is necessary to accelerate the early hydration of cement, shorten the setting time, and improve the early compressive strength in 24 hours to meet the requirements of accelerated drilling construction. On the other hand, it is necessary to optimize the toughness of cement stone and reduce the elastic modulus to ensure the long-term sealing and isolation capabilities of cement sheaths.

[0003] Most existing technical solutions address these issues by simultaneously incorporating early-strength agents and elastomeric materials. However, traditional inorganic salts and organic early-strength agents only focus on accelerating early hydration, which can easily disrupt the hydration balance of cement throughout its life cycle, inducing long-term strength reduction in cement stone and deteriorating its long-term mechanical properties. While elastomeric materials can improve the elastic and toughness properties of cement rings, they can also easily lead to uneven defects in the cement ring, resulting in a decrease in both early and long-term strength.

[0004] Furthermore, existing technical solutions often suffer from problems in practical applications, such as poor cement slurry suspension stability, complex on-site slurry composition, and difficulty in construction control. Chinese invention patent CN106927752A discloses a rubber-based ultra-early strength concrete and its preparation method. By adding a certain amount of rubber powder, the prepared ultra-early strength concrete possesses advantages such as high strength and low elastic modulus. However, its material system and performance indicators cannot meet the requirements of oil and gas well cementing operations. Chinese invention patent CN120590088A discloses a nano-composite early strength agent for cementing and its preparation method, significantly improving the early compressive strength of oil well cement at low temperatures. However, the preparation process is complex and it does not have the function of regulating the toughness of cement stone or reducing the elastic modulus. How to conveniently achieve early strength and toughening of cementing sheaths remains a pressing technical problem to be solved.

[0005] Therefore, it is necessary to develop a new type of cementing early strength agent that combines improving the mechanical properties of cement, easy preparation, and balanced comprehensive performance. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an early-strength agent for improving the mechanical properties of cementing and its preparation method.

[0007] Specifically, the present invention is achieved through the following technical solutions: An early-strength agent for improving the mechanical properties of cementing materials comprises: modified carbon nanomaterials, polycarboxylic acid polymers, inorganic salts, nonionic surfactants, and water.

[0008] The aforementioned early strength agent, based on 100 parts by weight of water, comprises 12-20 parts by weight of the modified carbon nanomaterial, 4-8 parts by weight of the polycarboxylic acid polymer, 20-30 parts by weight of the inorganic salt, and 1-4 parts by weight of the nonionic surfactant.

[0009] The aforementioned early strength agent, wherein the modified carbon nanomaterial is a modified multi-walled carbon nanotube or carbon nanofiber with a diameter of 200~400nm and an aspect ratio of 5~20.

[0010] The aforementioned early strength agent, wherein the modified carbon nanomaterial is prepared by the following method: (1) Under heating conditions, dissolve sodium silicate in water to prepare sodium silicate solution, and add acid to adjust the pH to 2~3; (2) Add carbon nanomaterials, stir evenly, add hydrogen peroxide, heat and stir; (3) Add alkali, adjust the pH to 6-7, and heat and stir; (4) The reaction system is separated into solid and liquid phases, and after cleaning and drying, modified carbon nanomaterials are obtained.

[0011] In the aforementioned early-strength agent, the acid is a 1M hydrochloric acid solution; the hydrogen peroxide has a concentration of 30 wt.%; and the alkali is a 0.1M sodium hydroxide solution.

[0012] The weight ratio of the aforementioned early strength agent, water, sodium silicate, carbon nanomaterials, and hydrogen peroxide is 100:(20~40):(8~24):(6~8).

[0013] The heating temperature in steps (1) to (3) of the above-mentioned early strength agent is 30~50℃.

[0014] The aforementioned early-strength agent, wherein the polycarboxylic acid polymer is a polycarboxylic acid water-reducing agent.

[0015] The inorganic salt in the aforementioned early-strength agent is an alkali metal thiosulfate or thiocyanate.

[0016] The inorganic salt in the aforementioned early-strength agent is sodium thiosulfate or sodium thiocyanate.

[0017] The aforementioned early-strength agent, wherein the nonionic surfactant is a polyoxyethylene ether compound.

[0018] The aforementioned early-strength agent, wherein the nonionic surfactant is PEG10000.

[0019] The preparation method of the above-mentioned early strength agent includes: dissolving polycarboxylic acid polymer, inorganic salt, nonionic surfactant and modified carbon nanomaterial in water in sequence, stirring, and obtaining the early strength agent.

[0020] In the above preparation method, the stirring time is 2 to 4 hours.

[0021] The technical solution of the present invention has the following beneficial effects: (1) The early strength agent of the present invention is an aqueous suspension based on carbon nanomaterials. When used in cementing slurry, it can effectively promote the early compressive strength development of cement stone at low dosage, showing excellent early strength effect. At the same time, the early strength agent has no adverse effect on the long-term strength development of cement stone and can improve the elastic modulus and other mechanical properties of cement stone, so that cement sheath can still obtain good comprehensive mechanical properties without the need to add extra elastic materials, which meets the application requirements of multifunctional early strength agent in deep water surface cementing construction.

[0022] (2) The early strength agent preparation method of the present invention does not require ultrasonic or high-speed shearing treatment, the process is simple, and it is significantly different from the traditional carbon nanomaterial suspension processing method, which is easy to implement industrially.

[0023] (3) The early strength agent of the present invention can significantly improve the early strength of cement stone while also improving mechanical properties such as elastic modulus. It has multiple functions and the preparation process is simple. It has good application prospects and economic benefits in deep water surface cementing and other projects. Detailed Implementation

[0024] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0025] The technical concept of this invention is as follows: modified carbon nanomaterials achieve cement stone toughening and modulus reduction through micropore filling, crack bridging, and hydration crystal form optimization; inorganic salts significantly improve the early mechanical strength of cement by regulating the cement hydration kinetics and accelerating the rapid generation of hydration products. The two complement each other and achieve synergistic performance from the perspectives of microstructure modification and hydration rate regulation. Furthermore, the use of polycarboxylic acid polymers and nonionic surfactants makes the dispersion suspension system more stable, ensuring the uniformity and stability of the early strength agent suspension.

[0026] Specifically, the early-strength agent for improving the mechanical properties of cementing provided by this invention includes: modified carbon nanomaterials, polycarboxylic acid polymers, inorganic salts, nonionic surfactants, and water.

[0027] In the early-strength agent of this invention, the synergistic effects of each component are as follows: A mild modification process is employed to regulate the size of carbon nanomaterials, improving their wetting and dispersibility while retaining their nano-filling, bridging, and toughening properties, thereby reducing the elastic modulus of cement paste; by adapting the inorganic salt components, early cement hydration is promoted, stabilizing and enhancing early compressive strength, achieving a synergistic strengthening effect with carbon nanomaterials without compromising the product's suspension stability. The polycarboxylate polymer and nonionic surfactant synergistically ensure uniform product dispersion and long-term stability.

[0028] The components of the early strength agent of this invention will be described in detail below.

[0029] Modified carbon nanomaterials In some preferred embodiments, the modified carbon nanomaterial is a modified multi-walled carbon nanotube or carbon nanofiber.

[0030] More preferably, the modified carbon nanomaterial has a diameter of 200-400 nm and an aspect ratio of 5-20.

[0031] In some preferred embodiments, the modified carbon nanomaterials are prepared by the following methods: (1) Under heating conditions, sodium silicate is dissolved in water to prepare sodium silicate solution, and acid is added to adjust the pH to 2~3.

[0032] Sodium silicate hydrolyzes under acidic conditions to generate an active silicic acid precursor, providing a reaction basis for the subsequent in-situ grafting of silica active groups onto the surface of carbon nanomaterials.

[0033] In some preferred embodiments, the sodium silicate is sodium silicate nonahydrate.

[0034] In some preferred embodiments, the heating temperature is 30~50°C.

[0035] In some preferred embodiments, the acid is a 1M hydrochloric acid solution.

[0036] (2) Add carbon nanotubes or carbon nanofibers, stir evenly, add hydrogen peroxide, and heat and stir.

[0037] The reactive oxygen free radicals generated by hydrogen peroxide under acidic conditions can activate inert sites on the surface of carbon nanomaterials; simultaneously, silicates in the system coat and modify the defect sites of carbon nanomaterials. This not only breaks down the original aggregated structure of carbon nanomaterials, significantly improving their water dispersibility, but also effectively preserves the material's complete skeletal structure and aspect ratio, thus ensuring its excellent toughening properties.

[0038] In some preferred embodiments, the heating temperature is 30~50°C.

[0039] In some preferred embodiments, the concentration of the hydrogen peroxide is 30 wt.%.

[0040] In some preferred embodiments, the weight ratio of water, sodium silicate, carbon nanomaterials, and hydrogen peroxide is 100:(20~40):(8~24):(6~8).

[0041] (3) Add alkali, adjust the pH to 6-7, and heat and stir.

[0042] This invention uses the addition of an alkali to the system to terminate the silicate coating modification of carbon nanomaterials.

[0043] In some preferred embodiments, the alkali is a 0.1M sodium hydroxide solution.

[0044] In some preferred embodiments, the heating temperature is 30~50°C.

[0045] (4) The reaction system is separated into solid and liquid phases, and after cleaning and drying, modified carbon nanomaterials are obtained.

[0046] In some preferred embodiments, the cleaning includes repeatedly washing the solid with deionized water 2 to 3 times.

[0047] In some preferred embodiments, the drying temperature is 80~110°C.

[0048] In the early strength agent of the present invention, the modified carbon nanomaterial is in the amount of 12 to 20 parts by weight.

[0049] In practice, when the proportion of modified carbon nanomaterials in the early strength agent is too small, it cannot effectively optimize the microstructure of cement stone, the toughening effect is not obvious, and the improvement of comprehensive mechanical properties is limited. When the proportion of modified carbon nanomaterials is too large, the excessive nanoparticles are prone to secondary agglomeration, which reduces the dispersion stability of the early strength agent and easily forms defect sites in the cement matrix, thus reducing the overall mechanical properties of the cement stone.

[0050] Polycarboxylic acid polymers In some preferred embodiments, the polycarboxylic acid polymer is a polycarboxylic acid water-reducing agent.

[0051] Optionally, the polycarboxylic acid polymers are all obtained through commercial purchase, such as polycarboxylic acid dispersants with the brand names 731A, 1618, or 1620 produced by Dow Chemical Company.

[0052] In the early strength agent of the present invention, the polycarboxylic acid polymer is in the amount of 4 to 8 parts by weight.

[0053] In practice, when the proportion of polycarboxylate polymers in the early-strength agent is too small, the electrostatic repulsion and steric hindrance of the system are insufficient, and the modified carbon nanomaterials and inorganic salt particles are prone to agglomeration and sedimentation, resulting in a significant decrease in suspension stability. When the proportion of polycarboxylate polymers is too large, the excess polycarboxylate polymers are prone to multilayer adsorption on the particle surface, causing a decrease in the stability of the early-strength agent. At the same time, it has a significant impact on the rheological parameters of cement slurry, affecting the adaptability of on-site cementing operations.

[0054] Inorganic salts In some preferred embodiments, the inorganic salt is an alkali metal sulfate or a thiocyanate.

[0055] More preferably, the inorganic salt is sodium sulfate or sodium thiocyanate.

[0056] In the early strength agent of the present invention, the inorganic salt is 20 to 30 parts by weight.

[0057] In practice, when the proportion of inorganic salts in the early strength agent is too small, it cannot effectively accelerate the early hydration reaction of cement, and the early strength improvement effect is weak. When the proportion of inorganic salts is too large, it will disrupt the charge balance of the dispersion system, causing the modified carbon nanomaterials to agglomerate and settle, and the suspension stability will decrease. In addition, excessive inorganic salts will cause the hydration products to grow disordered and have uneven structure, inducing the long-term strength reduction of cement stone and damaging the long-term mechanical stability of cement.

[0058] Nonionic surfactants In some preferred embodiments, the nonionic surfactant is a polyoxyethylene ether compound.

[0059] More preferably, the nonionic surfactant is PEG10000.

[0060] In the early strength agent of the present invention, the nonionic surfactant is present in 1 to 4 parts by weight.

[0061] In practice, when the proportion of nonionic surfactant in the early strength agent is too small, it cannot fully coat the modified carbon nanomaterial particles, resulting in insufficient surface wetting and modification of the material, poor anti-agglomeration and anti-settling ability of the system, and poor storage stability. When the proportion of nonionic surfactant is too large, the excess surfactant will disrupt the interfacial coating balance, which will also reduce the storage stability of the early strength agent.

[0062] On the other hand, the present invention also provides a method for preparing the above-mentioned early strength agent, comprising: dissolving a polycarboxylic acid polymer, an inorganic salt, a nonionic surfactant, and a modified carbon nanomaterial in water in sequence, stirring, and obtaining the early strength agent.

[0063] The early strength agent of this invention has a simple preparation method, which can simultaneously improve the early strength and elastic toughness of cement without the need for ultrasound or high-speed shearing. It also has good storage stability and a wide range of applications, which greatly meets the needs of cementing construction.

[0064] In some preferred embodiments, the stirring time is 2 to 4 hours.

[0065] The early strength agent prepared according to the method of the present invention can improve early strength while also improving the mechanical properties of cementing cement, such as elastic modulus. It has multiple functions and has great application prospects and economic benefits.

[0066] Example The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions. The raw materials used in the following embodiments were all commercially available.

[0067] Example 1 Preparation of modified carbon nanomaterials: 24g of sodium silicate nonahydrate was added to 100g of deionized water at 40℃ and stirred to dissolve. 1M hydrochloric acid was added to adjust the pH value to between 2 and 3. Then 12g of carbon nanotubes were added. After they were evenly dispersed, 8g of 30%wt hydrogen peroxide was added and the mixture was stirred for 2h. 0.1M sodium hydroxide solution was added to adjust the pH value to between 6 and 7 and stirring was continued for 1h. The reaction product was filtered out and washed repeatedly with deionized water 2-3 times. The product was dried at 90℃ to obtain the modified carbon nanomaterials.

[0068] Preparation of early strength agent: Add 8g of Dow polycarboxylate dispersant 731A, 24g of sodium thiosulfate, 2.4g of PEG10000 and 12g of modified carbon nanomaterials to 100g of water in sequence, stir to disperse evenly, and the early strength agent is obtained.

[0069] Example 2 Preparation of modified carbon nanomaterials: 30g of sodium silicate nonahydrate was added to 100g of deionized water at 30℃ and stirred to dissolve. 1M hydrochloric acid was added to adjust the pH value to between 2 and 3. Then 16g of carbon nanotubes were added. After they were evenly dispersed, 6g of 30%wt hydrogen peroxide was added and the mixture was stirred for 3h. 0.1M sodium hydroxide solution was added to adjust the pH value to 6-7 and stirring was continued for 1h. The reaction product was filtered out and washed repeatedly with deionized water 2-3 times. The product was dried at 100℃ to obtain the modified carbon nanomaterials.

[0070] Preparation of early strength agent: Add 6g of Dow polycarboxylate dispersant 1620, 28g of sodium thiosulfate, 3.2g of PEG10000, and 16g of modified carbon nanomaterials to 100g of water in sequence, and stir to disperse evenly to obtain early strength agent.

[0071] Example 3 Preparation of modified carbon nanomaterials: 36g of sodium silicate nonahydrate was added to 100g of deionized water at 50℃ and stirred to dissolve. 1M hydrochloric acid was added to adjust the pH value to between 2 and 3. Then 20g of carbon nanofibers were added. After they were evenly dispersed, 6g of 30%wt hydrogen peroxide was added and stirred for 3h. 0.1M sodium hydroxide solution was added to adjust the pH value to 6-7 and stirring was continued for 1h. The reaction product was filtered out and washed repeatedly with deionized water 2-3 times. It was dried at 100℃ to obtain the modified carbon nanomaterials.

[0072] Preparation of early strength agent: Add 6g of Dow polycarboxylate dispersant 1618, 24g of sodium thiocyanate, 2g of PEG10000, and 20g of modified carbon nanomaterials to 100g of water in sequence, and stir to disperse evenly to obtain the early strength agent.

[0073] Comparative Example 1 Preparation of early strength agent: Add 8g of Dow polycarboxylate dispersant 1620, 32g of sodium thiosulfate, 4g of PEG10000, and 12g of carbon nanotubes to 100g of water in sequence, and stir to disperse evenly to obtain the early strength agent.

[0074] Comparative Example 2 Preparation of modified carbon nanomaterials: 30g of sodium silicate nonahydrate was added to 100g of deionized water at 50℃ and stirred to dissolve. 1M hydrochloric acid was added to adjust the pH value to between 2 and 3. Then 28g of carbon nanotubes were added. After they were evenly dispersed, 6g of 30%wt hydrogen peroxide was added and the mixture was stirred for 3h. 0.1M sodium hydroxide solution was added to adjust the pH value to 6-7 and stirring was continued for 1h. The reaction product was filtered out and washed repeatedly with deionized water 2-3 times. The product was dried at 100℃ to obtain the modified carbon nanomaterials.

[0075] Preparation of early strength agent: Add 8g of Dow polycarboxylate dispersant 1620, 36g of sodium thiocyanate, 4.8g of PEG10000, and 28g of modified carbon nanomaterials to 100g of water in sequence, and stir to disperse evenly to obtain the early strength agent.

[0076] Performance testing The properties of the accelerators obtained in the above-mentioned embodiments and comparative examples, as well as their mechanical properties in cement paste systems of different densities, were tested according to the methods specified in GB10238. Simultaneously, their performance was compared with that of commercially available accelerator C-A95L (Lanhai Boda Technology Co., Ltd.), and the test results are shown in Table 1.

[0077] The cement slurry is composed of 100 parts of Grade G oil well cement (Jiahua Special Cement Co., Ltd.), 4 parts of oil well cement water loss reducer C-G80L (Lanhai Boda Technology Co., Ltd.), 0.25 parts of defoamer C-DF60L (Lanhai Boda Technology Co., Ltd.), and different types and quantities of early strength agents.

[0078] Table 1 Summary of performance test results of early strength agent

[0079] Note: The symbol "-" indicates that it has not been tested; The test results show that the early-strength agent prepared using this invention maintains stable properties after one month, without any abnormal phenomena such as gelation, sedimentation, or stratification. The compressive strength and elastic modulus of cement stone are effectively improved.

[0080] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0081] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0082] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. An early-strength agent for improving the mechanical properties of cementing, characterized in that, include: Modified carbon nanomaterials, polycarboxylic acid polymers, inorganic salts, nonionic surfactants, and water.

2. The early-strength agent according to claim 1, characterized in that, Based on 100 parts by weight of water, the modified carbon nanomaterial is 12-20 parts by weight, the polycarboxylic acid polymer is 4-8 parts by weight, the inorganic salt is 20-30 parts by weight, and the nonionic surfactant is 1-4 parts by weight.

3. The early-strength agent according to claim 1, characterized in that, The modified carbon nanomaterial is a modified multi-walled carbon nanotube or carbon nanofiber with a diameter of 200-400 nm and an aspect ratio of 5-20.

4. The early-strength agent according to claim 3, characterized in that, The modified carbon nanomaterials were prepared by the following method: (1) Under heating conditions, dissolve sodium silicate in water to prepare sodium silicate solution, and add acid to adjust the pH to 2~3; (2) Add carbon nanomaterials, stir evenly, add hydrogen peroxide, heat and stir; (3) Add alkali, adjust the pH to 6-7, and heat and stir; (4) The reaction system is separated into solid and liquid phases, and after cleaning and drying, modified carbon nanomaterials are obtained.

5. The early-strength agent according to claim 4, characterized in that, The acid is a 1M hydrochloric acid solution; the hydrogen peroxide has a concentration of 30 wt.%; and the alkali is a 0.1M sodium hydroxide solution.

6. The early-strength agent according to claim 4, characterized in that, The weight ratio of water, sodium silicate, carbon nanomaterials, and hydrogen peroxide is 100:(20~40):(8~24):(6~8).

7. The early-strength agent according to claim 4, characterized in that, The heating temperature in steps (1) to (3) is 30~50℃.

8. The early-strength agent according to claim 1, characterized in that, The polycarboxylic acid polymer is a polycarboxylic acid water-reducing agent.

9. The early-strength agent according to claim 1, characterized in that, The inorganic salt is an alkali metal thiosulfate or thiocyanate.

10. The early-strength agent according to claim 9, characterized in that, The inorganic salt is sodium thiosulfate or sodium thiocyanate.

11. The early-strength agent according to claim 1, characterized in that, The nonionic surfactant is a polyoxyethylene ether compound.

12. The early-strength agent according to claim 1, characterized in that, The nonionic surfactant is PEG10000.

13. The method for preparing the early-strength agent according to any one of claims 1 to 12, characterized in that, include: The polycarboxylic acid polymer, inorganic salt, nonionic surfactant, and modified carbon nanomaterial are dissolved in water in sequence and stirred to obtain the early strength agent.

14. The preparation method according to claim 13, characterized in that, The stirring time is 2 to 4 hours.

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