Oil well cement paste stability regulator and preparation method thereof
By using an oil well cement slurry stabilizer composed of gel particles and inhibitors, the stability problem of cement slurry was solved, the cement sheath bonding quality was improved and the construction was made more convenient. It is suitable for the drilling and completion process in oilfield development.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DAQING DRILLING ENGINEERING CO LTD
- Filing Date
- 2025-11-24
- Publication Date
- 2026-05-12
AI Technical Summary
Existing cement slurry stabilizers cannot absorb excess water in cement slurry after increasing the water-cement ratio and reducing density, resulting in a decline in the quality of cement ring bonding.
An oil well cement slurry stabilizer composed of gel particles and inhibitors is used. The gel particles do not absorb water in the early stage of hydration, but absorb excess water after hydration. The inhibitors are used to control the water absorption behavior of the gel particles in the early stage of hydration. The preparation method includes neutralization of acrylic monomers, polymerization, granulation and drying.
It improves the stability of cement slurry, prevents the slurry from thickening, ensures the quality of cement ring bonding, is suitable for dry-mixing methods, simplifies the construction process, and reduces the difficulty of transportation and environmental recycling.
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Abstract
Description
Technical Field
[0001] This disclosure relates to the technical field of oil well cement admixtures used in drilling and completion processes during oilfield development, specifically to oil well cement slurry stabilizers and their preparation methods. Background Technology
[0002] During drilling and completion operations in oilfield development, the increased annular size in the upper casing shoe and above results in a decreased annular return velocity and poorer displacement efficiency of the cement slurry upon reaching this area. Furthermore, severe mixing of the cement slurry with water-based isolation fluid in the casing shoe and above negatively impacts cementing quality. This is because mixing the cement slurry with water increases the water-cement ratio, lowers the slurry density, and results in a relatively high water content. This leads to a series of problems, such as uneven distribution of cement particles within the slurry, increasing the likelihood of sedimentation and stratification, and ultimately reducing the overall performance of the slurry. Simultaneously, excessive water affects the hydration rate and process of the cement, potentially leading to insufficient strength development, prolonged hardening time, and high cement stone volume shrinkage. These issues ultimately affect cementing quality. Therefore, ensuring the stability of the mixed cement slurry has become a key research focus to address these problems.
[0003] Currently, materials used as cement slurry stabilizers both domestically and internationally can be divided into two main categories: inorganic materials and organic polymer materials. Inorganic stabilizers mainly include ultrafine materials, clay-based substances, and some thixotropic substances. Ultrafine materials generally have very small particle sizes and large specific surface areas; when added to cement slurry, they typically have a thixotropic thickening effect, thus providing a certain degree of suspension capacity. Clay-based substances generally have high heat resistance and hydrate more completely at high temperatures, providing both thickening and the formation of a network structure, thus exhibiting good suspension capacity. However, inorganic stabilizers suffer from problems such as high initial consistency and difficulty in slurry mixing, which are unfavorable for on-site mixing and pumping. Therefore, the dosage must be strictly controlled during use, which to some extent limits their use as stabilizers. Organic polymer materials mainly include two categories: natural polymers and their modified forms, and synthetic polymers. Natural polymers and their modified forms used as cement slurry stabilizers mainly include plant gums and cellulose-based materials. Meanwhile, synthetic polymer materials are rapidly developing in cementing admixtures. Their performance is stable and easily controlled, allowing for molecular structure design based on product requirements, followed by the selection of suitable monomers to prepare the desired product. Synthetic polymer materials have relatively high molecular weights, effectively increasing the viscosity of the system and forming a certain network structure, thus exhibiting good suspension capacity. While all the above admixtures can address the stability issues of cement slurry to some extent, their main mechanism of action is through increasing the viscosity and suspension capacity of the cement slurry. However, none of them can absorb excess water in the cement slurry after increasing the water-cement ratio and reducing density. This excess water affects the cement hydration reaction and the volume of the cement paste, further impacting the cement sheath bonding quality. Summary of the Invention
[0004] In view of this, the present disclosure provides an oil well cement slurry stabilizer to solve the problem that existing cement slurry stabilizers cannot absorb excess water in the cement slurry after increasing the water-cement ratio and reducing the density, which affects the cement sheath bonding quality.
[0005] To achieve the above-mentioned objectives, in a first aspect, the oil well cement slurry stabilizer disclosed herein comprises gel particles and an inhibitor, wherein the inhibitor is used to inhibit the absorption of water by the gel particles in the initial stage of cement slurry hydration; and the gel particles are used to absorb excess water in the cement slurry after the initial stage of hydration.
[0006] Preferably, the gel particles are polyacrylamide gel particles, and the inhibitor is formate.
[0007] Preferably, the formate is sodium formate, potassium formate, or calcium formate.
[0008] Secondly, the method for preparing the oil well cement slurry stabilizer according to any one of the first aspects includes:
[0009] After neutralizing the acrylic monomer, it is polymerized with a crosslinking agent to obtain polyacrylamide colloid. The polyacrylamide colloid is then granulated, dried, and pulverized to obtain the stabilizer.
[0010] Preferably, a reinforcing agent, namely methylene succinic acid, is also added during the polymerization reaction of the acrylic monomer.
[0011] Preferably, the raw material components for the polymerization reaction, by weight percentage, include:
[0012] Acrylic monomer 10%-30%, alkaline solution 10%-30%, crosslinking agent 5%-10%, water 10%-30%, reinforcing agent 2%-10%, initiator 0.05%-0.2%.
[0013] Preferably, the crosslinking agent is N,N-methylenebisacrylamide.
[0014] Preferably, the initiator is a mixture of sodium bisulfite and persulfate, or a mixture of sodium bisulfite and peroxide.
[0015] Preferably, the persulfate is potassium persulfate or ammonium persulfate, and the peroxide is hydrogen peroxide.
[0016] Preferably, the method for polymerizing acrylic monomers with crosslinking agents includes:
[0017] After adding the acrylic monomer to the reaction vessel, it is neutralized with an alkaline solution to obtain solution A;
[0018] After adding a crosslinking agent, a reinforcing agent, and water to solution A, solution B is obtained;
[0019] After deoxygenating solution B, an initiator is added, and polymerization is carried out at 30-80℃.
[0020] Preferably, the polymerization time is defined as the reaction starting point when the temperature begins to rise and the reaction ending point when the temperature stops rising.
[0021] Preferably, the polymerization time is 3-6 hours.
[0022] The present invention has the following beneficial effects:
[0023] The oil well cement stabilizer of this invention comprises gel particles that absorb excess water in the cement slurry after increasing the water-cement ratio and reducing density, and an inhibitor that suppresses the absorption of water by the gel particles in the early stages of cement slurry hydration, allowing them to absorb excess water only after a period of hydration. This stabilizer effectively absorbs excess water in the cement slurry, preventing the generation of free liquid and ensuring its stability. Compared to cement slurry mixed with water, the cement slurry with the stabilizer exhibits better stability. The effect is even more pronounced after increasing the water-cement ratio; for example, cement slurry with a water-cement ratio of 0.44 has a free liquid content of 3.8% at room temperature, which decreases significantly after adding the stabilizer. With the water-cement ratio increased to 0.54, the free liquid content of the cement slurry at room temperature was 5.3%, and after adding the stabilizer, the free liquid content was 0%. This achieved no thickening of the cement slurry at low temperatures and a significant stabilizing effect. In addition, the stabilizer of this invention does not contain harmful substances, and the cement slurry preparation method has been changed. Because the admixture system is prepared by a completely dry mixing method, dry mixing is convenient and widely applicable. In summary, the stabilizer for oil well cement of this invention has the characteristics of convenient cementing construction, stable cement slurry performance, and convenient transportation and environmental recycling. It has important practical significance for cementing construction safety and improving cementing quality, and has important economic and social significance for improving the cementing of oil and gas wells such as adjustment wells. Detailed Implementation
[0024] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.
[0025] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details.
[0026] To address the problem that existing cement slurry stabilizers cannot absorb excess water in cement slurry after increasing the water-cement ratio and reducing density, thus affecting the cement ring bonding quality, this disclosure provides a stabilizing regulator for oil well cement, composed of gel particles and inhibitors. The gel particles are used to absorb excess water in cement slurry after increasing the water-cement ratio and reducing density, while the inhibitors are used to inhibit the absorption of water by the gel particles in the early stage of cement slurry hydration, preventing the slurry from thickening. The inhibitors only begin to absorb excess water in the cement slurry after hydration has been carried out for a period of time, ensuring the stability of the cement slurry.
[0027] The technical principle of the stabilizer / conditioner for oil well cement is as follows:
[0028] Because the stabilizer of this invention contains gel particles, which, under the action of the inhibitor, do not absorb water in the early stage of cement slurry hydration, this avoids the slurry from thickening in the early stage of hydration, which would make it difficult to deliver cement and hinder on-site mixing and pumping. After the cement slurry has been hydrating for a period of time (when pumping is complete), the gel particles begin to absorb excess water in the cement slurry, thereby better improving the stability of oil well cement after scaling up the water-cement ratio. It can absorb excess water in the cement slurry with a small amount, control the free liquid in the cement slurry, improve the stability of the cement slurry, increase the volume retention rate of the cement slurry, ensure the cement sheath bonding quality, and improve the cementing quality.
[0029] In a specific embodiment, the gel particles are polyacrylamide gel particles, and the inhibitor is formate.
[0030] In a specific embodiment, the formate is sodium formate or potassium formate.
[0031] In a specific embodiment, the polyacrylamide gel particles are prepared by:
[0032] After neutralizing the acrylic monomer, it is polymerized with a crosslinking agent to obtain polyacrylamide colloid. The polyacrylamide colloid is then granulated, dried, and pulverized to obtain the stabilizer.
[0033] In a specific embodiment, a reinforcing agent, namely methylene succinic acid, is added during the polymerization reaction of the acrylic monomer to improve the water absorption capacity of the stabilizer.
[0034] In a specific embodiment, the raw material components for the polymerization reaction, by weight percentage, include:
[0035] Acrylic monomer 10%-30%, alkaline solution 10%-30%, crosslinking agent 5%-10%, water 10%-30%, reinforcing agent 2%-10%, initiator 0.05%-0.2%.
[0036] In a specific embodiment, the alkaline solution is a sodium hydroxide solution with a mass concentration of 25%-50%.
[0037] In a specific embodiment, the crosslinking agent is N,N-methylenebisacrylamide.
[0038] In a specific embodiment, the initiator is a combination of sodium bisulfite and persulfate, or a combination of sodium bisulfite and peroxide. The persulfate is potassium persulfate or ammonium persulfate, and the peroxide is hydrogen peroxide.
[0039] In a specific embodiment, the method for polymerizing the acrylic monomer with the crosslinking agent is as follows:
[0040] After adding the acrylic monomer to the reaction vessel, it is neutralized with an alkaline solution to obtain solution A;
[0041] After adding a crosslinking agent, a reinforcing agent, and water to solution A, solution B is obtained;
[0042] After deoxygenating solution B, an initiator is added, and polymerization is carried out at 30-80℃.
[0043] In a specific embodiment, the polymerization time is determined based on the actual reaction conditions. The determination method is to take the start of the reaction as the beginning of the temperature rise and the end of the reaction as the end of the temperature rise. The preferred polymerization time is 3-6 hours.
[0044] The following are preferred embodiments of this disclosure.
[0045] The raw materials used in each embodiment are all commercially available chemical reagents or industrial-grade products. The preparation process parameters can be adjusted according to actual production needs, but the core principle is consistent with the technical solution of this invention.
[0046] Example 1
[0047] Add 20 parts of the organic compound monomer acrylic acid to a reaction vessel, slowly add 25 parts of 30% sodium hydroxide solution, control the temperature to ≤40℃, and neutralize to pH=7-8 to obtain solution A.
[0048] Add 8 parts of crosslinking agent N,N-methylenebisacrylamide, 5 parts of reinforcing agent methylene succinic acid and 25 parts of water to solution A, stir well to obtain solution B.
[0049] Nitrogen gas was introduced into solution B for 10 minutes to remove oxygen and ensure an oxygen-free environment. 0.1 parts of an initiator, which is sodium bisulfite and potassium persulfate in a mass ratio of 1:1, were added. The temperature was raised to 50°C and the reaction was carried out for 4 hours. The reaction was considered complete when the temperature stopped rising.
[0050] After the reaction was completed, the colloid was granulated, dried at 80°C for 6 hours, and then pulverized through a 200-mesh sieve to obtain the oil well cement stabilizer of Example 1.
[0051] Example 2
[0052] Add 15 parts of the organic compound monomer acrylic acid to a reaction vessel, slowly add 20 parts of 40% sodium hydroxide solution, control the temperature to ≤40℃, and neutralize to pH=7-8 to obtain solution A.
[0053] Add 6 parts of crosslinking agent N,N-methylenebisacrylamide, 8 parts of reinforcing agent methylene succinic acid and 30 parts of water to solution A, stir well to obtain solution B.
[0054] Nitrogen gas was introduced into solution B for 15 minutes to remove oxygen and ensure an anaerobic environment. 0.15 parts of initiator were added. The initiator was sodium bisulfite and hydrogen peroxide in a mass ratio of 1:1. The temperature was raised to 60°C. Because hydrogen peroxide is more active, the reaction time was shortened to 3 hours. The reaction endpoint was determined by the temperature no longer rising.
[0055] After the reaction was completed, the colloid was granulated. To avoid product degradation due to high temperature, it was dried at 70°C for 8 hours and then pulverized through a 200-mesh sieve to obtain the oil well cement stabilizer of Example 2.
[0056] Example 3
[0057] 25 parts of the organic compound monomer acrylic acid were added to a reaction vessel, and 15 parts of a 25% sodium hydroxide solution were slowly added dropwise while controlling the temperature to ≤40℃. The mixture was then neutralized to pH 7-8 to obtain solution A.
[0058] Add 10 parts of crosslinking agent N,N-methylenebisacrylamide, 3 parts of reinforcing agent methylene succinic acid and 20 parts of water to solution A, stir well to obtain solution B. Due to the high acrylic acid content, the viscosity of solution B increases significantly.
[0059] Nitrogen gas was introduced into solution B for 15 minutes to remove oxygen and ensure an oxygen-free environment. 0.2 parts of an initiator, which is sodium bisulfite and ammonium persulfate in a mass ratio of 1:1, were added. The reaction was carried out at a low temperature of 40°C for 6 hours to ensure full cross-linking. The reaction endpoint was defined as when the temperature no longer rose.
[0060] After the reaction is complete, the colloid is granulated. To avoid product degradation due to high temperature, it is dried at 70°C for 8 hours and then pulverized through a 100-mesh sieve to obtain the oil well cement stabilizer of Example 3. Because the product particles are relatively coarse, it is suitable for high-density cement slurry systems.
[0061] The following tests, following the cement slurry stability test method in GB / T 19139 "Test Methods for Cement in Oil Wells", compare the stability of fully dry-mixed cement slurry with pure cement slurry after increasing the water-cement ratio, focusing on the addition of the stabilizing modifiers from Examples 1-3:
[0062] Cement slurry formulation: 100% Kunlun G-grade oil well cement + 2.0% stabilizer + 0.7% ketone condensate dispersant + 0.1% polycarboxylate dispersant + 0.6% polymer-based fluid loss reducer + 0.5% strength supplement + 54% water. Converted to actual mass formulation: 800g Kunlun G-grade oil well cement + 16g stabilizer + 5.6g ketone condensate dispersant SXY + 0.8g polycarboxylate dispersant SD + 4.8g polymer-based fluid loss reducer G307 + 4g strength supplement (fumed silica) + 432g water. Test data for cement slurry stability and compressive strength are shown in Table 1, according to GB / T 19139 "Test Methods for Oil Well Cement".
[0063] Table 1. Comparison of stability and compressive strength of four cement paste systems
[0064]
[0065] The data in Table 1 show that, by adjusting the proportions of monomers, crosslinking agents, and initiators, the stabilizers in Examples 1-3 are all adaptable to cement slurry systems with increased water-cement ratios, significantly improving the stability of the cement slurry. Furthermore, Examples 1-3 all achieved near-zero free liquid levels and had no negative impact on the strength of the cement paste, verifying the universality and reliability of the technology.
[0066] Further testing was conducted on the stabilizer of the present invention. Specifically, the stabilizer prepared in Example 1 was used to form a fully dry-mixed cement slurry system by combining it with other cement admixtures. The specific formula was: 100% Kunlun G-grade oil well cement + 2.0% stabilizer + 0.7% ketone condensate dispersant SXY + 0.1% polycarboxylate dispersant SD + 0.6% polymer-based water loss reducing agent G307 + 0.5% strength supplement precipitate silica + 44% water. The comparison and evaluation of the stability performance of the fully dry-mixed cement slurry and the original slurry after increasing the water-cement ratio is shown in Table 2. The comparison and evaluation of the comprehensive performance of the fully dry-mixed cement slurry and the original slurry is shown in Table 3.
[0067] Table 2. Comparison of stability properties of fully dry-mixed cement paste and original paste after increasing water-cement ratio.
[0068]
[0069] Table 3 Comparison of Comprehensive Performance between Dry-Mixed Cement Slurry and Original Cement Slurry
[0070]
[0071] As shown in Tables 2 and 3, the dry-mixed cement slurry system has better stability, lower water loss, and similar thickening time but shorter transition time compared to pure cement slurry. Overall, it has excellent comprehensive performance and is suitable for adjustment well construction.
[0072] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. An oil well cement slurry stabilizer, characterized in that, Its components consist of gel particles and inhibitors. The inhibitors are used to suppress the absorption of water by the gel particles in the early stage of cement slurry hydration. The gel particles are used to absorb excess water in the cement slurry after the initial stage of hydration.
2. The oil well cement slurry stabilizer according to claim 1, characterized in that: The gel particles are polyacrylamide gel particles, and the inhibitor is formate.
3. The oil well cement slurry stabilizer according to claim 1, characterized in that: The formate is sodium formate, potassium formate, or calcium formate.
4. The method for preparing the oil well cement slurry stabilizer according to any one of claims 1-3, characterized in that, include: After neutralizing the acrylic monomer, it is polymerized with a crosslinking agent to obtain polyacrylamide colloid. The polyacrylamide colloid is then granulated, dried, and pulverized to obtain the stabilizer.
5. The method for preparing the oil well cement slurry stabilizer according to claim 4, characterized in that: A reinforcing agent, namely methylene succinic acid, is also added during the polymerization reaction of the acrylic monomer.
6. The method for preparing the oil well cement slurry stabilizer according to claim 5, characterized in that, The raw material components for the polymerization reaction, by weight percentage, include: Acrylic monomer 10%-30%, alkaline solution 10%-30%, crosslinking agent 5%-10%, water 10%-30%, reinforcing agent 2%-10%, initiator 0.05%-0.2%.
7. The method for preparing the oil well cement slurry stabilizer according to claim 6, characterized in that: The crosslinking agent is N,N-methylenebisacrylamide.
8. The method for preparing the oil well cement slurry stabilizer according to claim 6, characterized in that: The initiator is a mixture of sodium bisulfite and persulfate, or a mixture of sodium bisulfite and peroxide.
9. The method for preparing the oil well cement slurry stabilizer according to claim 8, characterized in that: The persulfate is potassium persulfate or ammonium persulfate, and the peroxide is hydrogen peroxide.
10. The method for preparing the oil well cement slurry stabilizer according to any one of claims 6-9, characterized in that, Methods for polymerizing acrylic monomers with crosslinking agents include: After adding the acrylic monomer to the reaction vessel, it is neutralized with an alkaline solution to obtain solution A; After adding a crosslinking agent, a reinforcing agent, and water to solution A, solution B is obtained; After deoxygenating solution B, an initiator is added, and polymerization is carried out at 30-80℃.
11. The method for preparing the oil well cement slurry stabilizer according to claim 10, characterized in that: The polymerization time is defined as the reaction starting when the temperature begins to rise and ending when the temperature stops rising.
12. The method for preparing the oil well cement slurry stabilizer according to claim 11, characterized in that: The polymerization time is 3-6 hours.