Preparation and application of thermal response phase change gel anti-channeling agent for high-temperature well cementation

Abstract

The invention designs and prepares a phase change gel channeling inhibitor based on a phase change gelation principle. In a stratum high-temperature environment, a strong gel network structure is formed through a transamide reaction between the polyacrylamide functional polymer and the polyamine, so that the gel performance of the cement paste during hydration at 150-200 DEG C is enhanced, the compactness of the cement paste is improved, and the static gel transition time is shortened. Meanwhile, the self-assembled temperature-resistant cross-linked polymer network reduces the pores of the filter cake, improves the filtration performance of the cement paste, and reduces the pressure loss of the liquid column. In addition, a silicon dioxide-coated whisker material is grafted on the functional polymer and is combined with an internal polymer network to achieve a synergistic effect, so that the elasticity, toughness and mechanical property of the cured cement paste are improved, and the later-stage anti-channeling capability of a cement sheath is improved. The phase change gel anti-channeling agent disclosed by the invention can strengthen the anti-channeling performance of high-temperature well cementation cement in the whole life cycle, ensure the well cementation quality of a high-temperature deep well and ensure the long-term sealing property and safety of a shaft.

Description

Technical Field

[0001] This invention relates to a thermally responsive phase change gel anti-channeling agent, which is suitable for improving the water loss and anti-channeling properties of high-temperature cement slurry during the hydration period, and improving the mechanical properties and elastic toughness of cement stone. Background Technology

[0002] As my country's oil and gas exploration and development advances into deeper, higher-temperature formations, the requirements for cementing slurry performance are increasingly stringent. Currently, gas channeling accounts for as much as 30% of cementing operations, severely restricting cementing progress and oil and gas development efficiency. The high-temperature downhole environment leads to significant degradation of cementing slurry performance, manifested in delayed early static gel strength development, insufficient compressive strength of the cement stone in the later stages, and decreased toughness. These factors collectively weaken the anti-channeling capability of the cement sheath throughout its entire life cycle. More seriously, the decrease in static fluid column pressure during the hydration stage can cause high-pressure gas to migrate vertically along the weak zones and cementation interfaces of the cementing slurry. If the gas enters heterogeneous layers, it will lead to a decrease in production capacity; if it channels to the wellhead, it may trigger a blowout. Therefore, improving the anti-channeling performance of high-temperature cementing slurries, optimizing the development law of static gel strength, and enhancing the elastic toughness of the cement stone have become core technical challenges for ensuring cementing quality and safety.

[0003] In oil well cementing engineering, the application of nanomaterials and fiber toughening technology provides an effective way to improve the anti-channeling ability of cement slurry and enhance the performance of cement stone. Polymer latex, as a nanoscale modifier, can fill the pore structure of cement slurry, making the cement more compact. Furthermore, under pressure differential, latex particles form a continuous, tough polymer film between cement particles. This microstructural change significantly improves the rate of cement stone gel strength development, while reducing the elastic modulus by 15-30% and increasing the flexural strength by more than 10%, thus effectively improving the mechanical adaptability of the cement sheath (Chinese Patent CN118063705 A, A temperature- and salt-resistant latex toughening and anti-channeling agent and its preparation method and application; Chinese Patent CN120040114 A, Low-temperature accelerating anionic styrene-butadiene latex for oilfield cementing and its preparation method). However, the practical application of latex materials still faces several technical bottlenecks. First, the latex dosage is generally large, and the zeta potential stability of particles in the alkaline cement slurry environment is insufficient, often leading to uneven particle size distribution, directly affecting the homogeneity of the slurry. Secondly, in high-temperature and high-pressure well sections (150℃ / 70MPa), the compressive strength retention rate of latex-modified cement stone decreases, significantly restricting the mechanical properties of the cement ring. In contrast, fiber and whisker toughening technology works through a physical bridging mechanism. When 1.5% additional carbon fiber is added, the elastic modulus of the cement stone decreases by more than 30% (Chinese Patent CN 110791265 A, Preparation Method of Carbon Fiber Toughening Agent for Oil Well Cement). This strengthening effect mainly originates from the energy dissipation mechanism at the fiber-matrix interface, including fiber pull-out, bridging cracks, and other toughening methods. However, the addition of fibers significantly reduces the fluidity of the cement slurry and has limited impact on the cement slurry's gel strength development curve, making it difficult to meet the special requirements of rapid gel strength development in high-temperature cementing. The main challenge of current research lies in how to simultaneously enhance the early static gel strength development of the cement slurry and improve the later mechanical properties of the cement stone, thereby enhancing the anti-channeling capability of the cement slurry throughout its entire life cycle. Summary of the Invention

[0004] This invention demonstrates the preparation and application of a thermally responsive phase change gel anti-channeling agent. The primary amide group of the anti-channeling agent and the amino group of the polyamine spontaneously undergo a transamide reaction at high temperature, forming a polymer network structure through in-situ cross-linking and gelation. This improves the thixotropic properties of cement slurry, shortens the static gelation transition time, and enhances its anti-channeling performance. Simultaneously, based on the interfacial bonding efficiency of silica-encapsulated whiskers, it enhances the compressive strength and toughness of cement stone, prevents the formation of microcracks in cement slurry, and ensures the cementing quality and long-term sealing performance of wellbore in high-temperature gas wells prone to channeling.

[0005] To perfectly achieve the above-mentioned objectives, the specific preparation method is as follows:

[0006] The monomers that make up functionalized thermally responsive polymers include: primary amide monomers, alkyl acrylamide monomers, and sulfonic acid monomers.

[0007] The functionalized thermally responsive polymer is synthesized with the following monomer mass ratio: 4-12 parts by mass of primary amide monomer, 6-15 parts by mass of alkyl acrylamide monomer, and 8-20 parts by mass of sulfonic acid monomer.

[0008] The preparation method of the phase change gel antichanneling agent includes the following steps:

[0009] (1) Mix 6-18 parts by mass of ethyl silicate and 10 parts by mass of anhydrous ethanol to form an ethyl silicate solution. Add 68-136 parts by mass of anhydrous ethanol, 10-20 parts by mass of deionized water, 1-5 parts by mass of ammonia and 2-6 parts by mass of whiskers to a glass container. Stir at 300 rpm for 40 min, then sonicate for 30-40 min. Raise the temperature of the above solution to 40-60℃ at 300-450 rpm. Then inject the ethyl silicate solution into the glass container at an injection rate of 0.5-1.5 mL / min using a high-pressure injection pump. Continue the reaction for 10-12 h. Filter under reduced pressure and wash the solid three times with anhydrous ethanol to obtain silica-coated whiskers with a yield of 87-95%.

[0010] (2) Take 4-8 parts by mass of silica-coated whiskers, 68-136 parts by mass of anhydrous ethanol, 10-20 parts by mass of deionized water and 1-5 parts by mass of ammonia water and place them in a glass container. Stir at 300 rpm for 40 min, then sonicate for 30-40 min. Then raise the temperature of the solution to 50-60℃ at 400-600 rpm. Mix 0.2-0.8 parts by mass of silane coupling agent and 1 part by mass of deionized water to form a coupling agent solution. Then inject the coupling agent solution into the glass container at an injection rate of 0.1-1 mL / min using a high-pressure injection pump. Continue the reaction for 2-6 h. Filter under reduced pressure and wash the solid three times with anhydrous ethanol to obtain allyl whiskers with a yield of 90-94%.

[0011] (3) Add the primary amide monomer, alkyl acrylamide monomer and sulfonic acid monomer to a glass container, add 120-160 parts by weight of deionized water, adjust the pH of the monomer solution to 6-8 using sodium hydroxide solution, and then add 0.36-1.8 parts by weight of allyl whiskers and 0.1-0.4 parts by weight of initiator in sequence to prepare the monomer aqueous solution.

[0012] (4) Continuously introduce high-purity nitrogen into the reaction vessel to remove oxygen, control the stirring rate to 350-600 rpm, raise the temperature of the monomer aqueous solution to between 50-80℃, maintain the polymerization reaction for 6-10 hours, and obtain the phase change gel anti-channeling agent after natural cooling, with a solid content of 16.8-17.4%.

[0013] The functionalized thermally responsive polymer contains structural unit A of Formula 1, structural unit B of Formula 2, and structural unit C of Formula 3.

[0014]

[0015] The whiskers are one of calcium carbonate whiskers, calcium sulfate whiskers, magnesium hydroxide whiskers, potassium titanate whiskers, and silicon carbide whiskers.

[0016] The silane coupling agent is one of γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

[0017] The initiator is one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride, and azobisisobutylimidazoline hydrochloride.

[0018] In terms of currently available general technology, this invention has the following advantages:

[0019] 1. Alkyl acrylamide monomers and sulfonic acid monomers are common heat-resistant functional monomers that can significantly enhance the high-temperature hydrolysis resistance of phase change gel anti-channeling agents. When phase change gel anti-channeling agents and polyamines undergo cross-linking reactions at high temperatures, these functional monomers play a role by stabilizing the molecular structure. The polymer grafted with nano-scale whiskers maintains structural stability and mechanical strength at high temperatures through a stronger internal cross-linking network. Its excellent thermal stability and anti-deformation ability can effectively prevent the high-temperature collapse of phase change gel anti-channeling agents.

[0020] 2. High-temperature environments can trigger a multi-site amide conversion reaction between the amide groups of the phase change gel anti-channeling agent and the amine groups of polyamine. Based on the temperature response mechanism, an in-situ phase change occurs in the cement slurry to form a temperature-resistant three-dimensional network structure, thereby significantly improving the static gel strength of the cement slurry and optimizing the transition time. By adjusting the ratio of the phase change gel anti-channeling agent to polyamine, the gel development time of the cement slurry system can be precisely controlled to meet the engineering requirements of high-temperature formations at different depths.

[0021] 3. Grafting technology of silica-encapsulated whiskers enhances the interfacial bonding performance between whisker materials and cement hydration products, and improves the later compressive strength of cement stone based on the whisker reinforcement principle; the synergistic effect of silica-encapsulated whiskers and polymer network structure can improve the elastic toughness of cement stone, reduce the elastic modulus, and achieve balanced optimization of mechanical properties.

[0022] 4. The raw materials for synthesizing phase change gel antiscanning agents are all common materials on the market, with wide and abundant sources and low prices, making them suitable for large-scale production and use. Furthermore, the synthesis process and conditions are simple, and the equipment requirements are low. Attached Figure Description

[0023] Figure 1This is a SEM image of silica-encapsulated whiskers in Embodiment S1 of the present invention.

[0024] Figure 2 The infrared spectrum of the phase change gel antiscanning agent in Embodiment S1 of the present invention is shown.

[0025] Figure 3 The thermogravimetric curve of the phase change gel anti-channeling agent in Embodiment S1 of the present invention.

[0026] Figure 4 This is an SEM image of the phase change gel antiscanning agent gel system in Embodiment S1 of the present invention. Detailed Implementation

[0027] I. Composition, Preparation and Application of Phase Change Gel Antiscanning Agents

[0028] The specific embodiments and comparative examples below will be used to describe in detail the specific implementation of the present invention, so as to facilitate a comprehensive understanding of the technical achievements of the present invention.

[0029] The sources and properties of the raw materials used in the following examples and comparative examples are as follows:

[0030] Acrylamide: Acrylamide from Shanghai Aladdin Biochemical Technology Co., Ltd. was used.

[0031] 2-Acrylamide-2-methylpropanesulfonic acid: 2-Acrylamide-2-methylpropanesulfonic acid from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0032] N-Vinylpyrrolidone: N-Vinylpyrrolidone from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0033] Potassium titanate whiskers: Potassium titanate whiskers from Jiangsu Nantong Aoxin Co., Ltd., with a diameter of 0.1-0.3 micrometers and a length of 3-5 micrometers.

[0034] Ethanol: 95% anhydrous ethanol from Shanghai McLean Biochemical Technology Co., Ltd. was used.

[0035] KH570: The silane coupling agent KH570 from Beijing Mairuida Technology Co., Ltd. is used.

[0036] Ethyl silicate: Ethyl silicate from Shanghai Maclean Biochemical Technology Co., Ltd.

[0037] Ammonia solution: 25-28% aqueous solution of ammonia solution from Shanghai Maclean Biochemical Technology Co., Ltd.

[0038] Sodium hydroxide: Sodium hydroxide from Shanghai Aladdin Biochemical Technology Co., Ltd. was used.

[0039] Ammonium persulfate: Ammonium persulfate from Shanghai Aladdin Biochemical Technology Co., Ltd. was used.

[0040] Polyethyleneimine: Polyethyleneimine from Shanghai Maclean Biochemical Technology Co., Ltd., with a molecular weight of 10,000, was used.

[0041] Oil well cement: Grade G oil well cement from Sichuan Jiahua Special Cement Co., Ltd.

[0042] Silica sand: Silica sand from Anxian Huaxi Mineral Powder Co., Ltd., particle size: 200 mesh.

[0043] Retarder: HX-36L retarder from Chengdu Omeke Petroleum Technology Co., Ltd. was used.

[0044] Defoamer: DF-B defoamer from Chengdu Omec Petroleum Technology Co., Ltd. was used.

[0045] Example 1

[0046] This example provides a phase change gel antichanneling agent, wherein the monomer formulation of the functionalized thermally responsive polymer is: 12 parts by mass of acrylamide, 6 parts by mass of N-vinylpyrrolidone, and 8 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid.

[0047] The preparation steps of silica-coated whiskers are as follows: 6 parts by mass of ethyl silicate and 10 parts by mass of anhydrous ethanol are mixed to form an ethyl silicate solution. 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water, 3 parts by mass of ammonia water, and 3 parts by mass of potassium titanate whiskers are added to a glass container. The mixture is stirred at 300 rpm for 40 min, then sonicated for 30 min. The temperature of the solution is raised to 40°C at 450 rpm. The ethyl silicate solution is then injected into the glass container at an injection rate of 0.5 mL / min using a high-pressure injection pump. The reaction continues for 12 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain silica-coated whiskers.

[0048] The preparation steps of allyl whiskers are as follows: 6 parts by mass of silica-coated whiskers, 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water and 3 parts by mass of ammonia are placed in a glass container and stirred at 300 rpm for 40 min, then sonicated for 30 min. Subsequently, the solution is heated to 60℃ at 400 rpm. 0.3 parts by mass of KH570 and 1 part by mass of deionized water are mixed to form a coupling agent solution. The coupling agent solution is then injected into the glass container at an injection rate of 0.1 mL / min using a high-pressure injection pump. The reaction continues for 4 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain allyl whiskers.

[0049] The preparation steps of the phase change gel anti-channeling agent are as follows: Acrylamide, N-vinylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution. Then, 1.3 parts by mass of allyl whiskers and 0.02 parts by mass of ammonium persulfate are added sequentially to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring rate is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to between 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent, labeled S1, is obtained.

[0050] Example 2

[0051] This example provides a phase change gel antichanneling agent, wherein the monomer formulation of the functionalized thermally responsive polymer is: 12 parts by mass of acrylamide, 6 parts by mass of N-vinylpyrrolidone, and 8 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid.

[0052] The preparation steps of silica-coated whiskers are as follows: 3 parts by mass of ethyl silicate and 10 parts by mass of anhydrous ethanol are mixed to form an ethyl silicate solution. 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water, 3 parts by mass of ammonia water, and 3 parts by mass of potassium titanate whiskers are added to a glass container. The mixture is stirred at 300 rpm for 40 min, then sonicated for 30 min. The temperature of the above solution is raised to 40°C at 450 rpm. Then, the ethyl silicate solution is injected into the glass container at an injection rate of 0.5 mL / min using a high-pressure injection pump. The reaction continues for 12 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain silica-coated whiskers.

[0053] The preparation steps of allyl whiskers are as follows: 6 parts by mass of silica-coated whiskers, 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water and 3 parts by mass of ammonia are placed in a glass container and stirred at 300 rpm for 40 min, then sonicated for 30 min. Subsequently, the solution is heated to 60℃ at 400 rpm. 0.3 parts by mass of KH570 and 1 part by mass of deionized water are mixed to form a coupling agent solution. The coupling agent solution is then injected into the glass container at an injection rate of 0.1 mL / min using a high-pressure injection pump. The reaction continues for 4 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain allyl whiskers.

[0054] The preparation steps of the phase change gel anti-channeling agent are as follows: Acrylamide, N-vinylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution. Then, 0.78 parts by mass of allyl whiskers and 0.02 parts by mass of ammonium persulfate are added sequentially to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring rate is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to between 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent, labeled S2, is obtained.

[0055] Example 3

[0056] This example provides a phase change gel antichanneling agent, wherein the monomer formulation of the functionalized thermally responsive polymer is: 6 parts by mass of acrylamide, 4 parts by mass of N-vinylpyrrolidone, and 16 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid.

[0057] The preparation steps of silica-coated whiskers are as follows: 6 parts by mass of ethyl silicate and 10 parts by mass of anhydrous ethanol are mixed to form an ethyl silicate solution. 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water, 3 parts by mass of ammonia water, and 3 parts by mass of potassium titanate whiskers are added to a glass container. The mixture is stirred at 300 rpm for 40 min, then sonicated for 30 min. The temperature of the solution is raised to 40°C at 450 rpm. The ethyl silicate solution is then injected into the glass container at an injection rate of 0.5 mL / min using a high-pressure injection pump. The reaction continues for 12 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain silica-coated whiskers.

[0058] The preparation steps of allyl whiskers are as follows: 6 parts by mass of silica-coated whiskers, 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water and 3 parts by mass of ammonia are placed in a glass container and stirred at 300 rpm for 40 min, then sonicated for 30 min. Subsequently, the solution is heated to 60℃ at 400 rpm. 0.3 parts by mass of KH570 and 1 part by mass of deionized water are mixed to form a coupling agent solution. The coupling agent solution is then injected into the glass container at an injection rate of 0.1 mL / min using a high-pressure injection pump. The reaction continues for 4 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain allyl whiskers.

[0059] The preparation steps of the phase change gel anti-channeling agent are as follows: Acrylamide, N-vinylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution. Then, 1.3 parts by mass of allyl whiskers and 0.02 parts by mass of ammonium persulfate are added sequentially to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring rate is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to between 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent is obtained, labeled as S3.

[0060] Example 4

[0061] This example provides a phase change gel antichanneling agent, wherein the monomer formulation of the functionalized thermally responsive polymer is: 12 parts by mass of acrylamide, 6 parts by mass of N-vinylpyrrolidone, and 8 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid.

[0062] The preparation steps of silica-coated whiskers are as follows: 6 parts by mass of ethyl silicate and 10 parts by mass of anhydrous ethanol are mixed to form an ethyl silicate solution. 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water, 3 parts by mass of ammonia water, and 3 parts by mass of potassium titanate whiskers are added to a glass container. The mixture is stirred at 300 rpm for 40 min, then sonicated for 30 min. The temperature of the solution is raised to 40°C at 450 rpm. The ethyl silicate solution is then injected into the glass container at an injection rate of 0.5 mL / min using a high-pressure injection pump. The reaction continues for 12 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain silica-coated whiskers.

[0063] The preparation steps of allyl whiskers are as follows: 6 parts by mass of silica-coated whiskers, 68 parts by mass of anhydrous ethanol, 10 parts by mass of deionized water and 3 parts by mass of ammonia are placed in a glass container and stirred at 300 rpm for 40 min, then sonicated for 30 min. Subsequently, the solution is heated to 60℃ at 400 rpm. 0.18 parts by mass of KH570 and 1 part by mass of deionized water are mixed to form a coupling agent solution. The coupling agent solution is then injected into the glass container at an injection rate of 0.1 mL / min using a high-pressure injection pump. The reaction is continued for 4 h. The mixture is filtered under reduced pressure and the solid is washed three times with anhydrous ethanol to obtain allyl whiskers.

[0064] The preparation steps of the phase change gel anti-channeling agent are as follows: Acrylamide, N-vinylpyrrolidone, and 2-acrylamido-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution. Then, 1.3 parts by mass of allyl whiskers and 0.02 parts by mass of ammonium persulfate are added sequentially to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring rate is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to between 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent, labeled S4, is obtained.

[0065] Comparative Example 1

[0066] Silica-coated whiskers, allyl whiskers, and phase change gel antiscanning agents were prepared using the same method as in Example S1.

[0067] The difference is that no acrylamide was added during the preparation of the phase change gel anti-channeling agent.

[0068] The monomer formulation of the functionalized thermally responsive polymer is: 6 parts N-vinylpyrrolidone and 8 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid.

[0069] The preparation steps of the phase change gel anti-channeling agent are as follows: N-vinylpyrrolidone and 2-acrylamide-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution. Then, 1.3 parts by mass of allyl whiskers and 0.02 parts by mass of ammonium persulfate are added sequentially to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring rate is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to between 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent is obtained, labeled as D1.

[0070] Comparative Example 2

[0071] Silica-coated whiskers, allyl whiskers, and phase change gel antiscanning agents were prepared using the same method as in Example S1.

[0072] The difference is that no whisker material is added during the preparation of the phase change gel antiscanning agent.

[0073] The preparation steps of the phase change gel anti-channeling agent are as follows: 12 parts by mass of acrylamide, 6 parts by mass of N-vinylpyrrolidone, and 8 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution, and then 0.02 parts by mass of ammonium persulfate is added to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring speed is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent is obtained, labeled as D2.

[0074] Comparative Example 3

[0075] Allyl whiskers and phase change gel antiscanning agents were prepared using the same method as in Example S1.

[0076] The difference is that allyl whiskers are not prepared using whiskers treated with ethyl silicate.

[0077] The preparation steps of the phase change gel anti-channeling agent are as follows: 12 parts by mass of acrylamide, 6 parts by mass of N-vinylpyrrolidone, and 8 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid are added to a glass container, along with 121 parts by mass of deionized water. The pH of the monomer solution is adjusted to 6-8 using sodium hydroxide solution, and then 0.02 parts by mass of ammonium persulfate is added to prepare an aqueous monomer solution. High-purity nitrogen is continuously introduced into the reaction vessel to purge oxygen. The stirring speed is controlled at 400 rpm, and the temperature of the monomer aqueous solution is raised to 75°C. The polymerization reaction is maintained for 6 hours, and after natural cooling, the phase change gel anti-channeling agent is obtained, labeled as D2.

[0078] II. Performance Comparison of Phase Change Gel Anti-channeling Agents in Cementing Slurry

[0079] Test Example 1

[0080] Examples S1, S2, S3, and S4, and Comparative Examples D1, D2, and D3, were prepared into aqueous solutions with different mass fractions of phase change gel inhibitor and polyethyleneimine, and then placed in an oven at 150°C for static phase change gelation. The gel strength was visually assessed using the Sydansk gel strength code, where AJ code levels indicate progressively increasing gel strength. The time required to reach gel strength level I was defined as the gel time. The storage modulus of each gel system was measured using an Anton Paar rheometer (MCR 302) to analyze the strength differences of the gel after curing under different conditions.

[0081] Table 1. Gel properties of phase change gel antichanneling agents with different mass fractions

[0082]

[0083]

[0084] Note: "-" indicates that the gel strength has not reached Grade I.

[0085] The acrylamide group in the phase change gel anti-channeling agent molecule is a key functional group for constructing temperature-responsive polymer gels. The absence of this group will cause the polymer to lose its ability to form a gel network in response to temperature-stimulated phase change. The advantage of this invention lies in achieving precise control over the network gel strength and gelation time; that is, as the concentration of the phase change gel anti-channeling agent increases, the gelation time decreases accordingly, and the gel strength significantly increases within a certain concentration range. This controllable gelation time is a key parameter to ensure that the phase change gel anti-channeling agent achieves in-situ crosslinking in cement slurry to form a high-strength gel. Its controllable characteristics provide engineering feasibility for adapting to different well depth conditions and pumping process requirements. It is worth noting that the whisker material, as a cement reinforcing agent, can act as a rigid framework structure for the gel network, thereby effectively improving the mechanical strength of the temperature-responsive gel. After silica surface coating treatment, the density of active groups on the whisker surface increases significantly, which further improves the gel strength of the anti-channeling agent grafted with whiskers.

[0086] Test Example 2

[0087] Examples S1, S2, S3, S4 and comparative examples D1, D2, D3 were prepared into a 4% (w / w) aqueous solution of phase change gel antiscanning agent. The effect of polyethyleneimine concentration on the gelation performance of the phase change gel antiscanning agent system at 150°C was investigated based on parameters such as gelation time and gel strength. The experimental results are shown in Table 2.

[0088] Table 2. Effect of polyethyleneimine mass fraction on gel properties of phase change gel anti-channeling agent

[0089]

[0090]

[0091] Polyethyleneimine concentration is also a key factor for the controllable adjustment of gel time and gel strength. Results show that increasing the polyethyleneimine concentration can shorten the gel time of the phase change gel anti-channeling agent while enhancing the mechanical strength of the gel network. Furthermore, compared to anti-channeling agents without grafted whiskers or without silica coating, the advantage of this invention is that the silica-coated whisker surface has a higher density of active groups, enabling it to act as crosslinking nodes in the polymer gel, effectively increasing the storage modulus of the gel network, thereby further enhancing the overall strength of the gel. Increasing the polyethyleneimine concentration not only promotes gel network formation but also increases the crosslinking density, making the gel structure more compact and ultimately achieving higher mechanical properties.

[0092] Test Example 3

[0093] Using Examples S1, S2, S3, S4 and Comparative Examples D1, D2, D3 as the research objects, high-temperature anti-channeling cementing systems were prepared according to the API test standards for cement slurry. Based on the national standard GB / T 19139-2012 "Test Methods for Oil Well Cement" and the industry standard SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry", the effects of different concentrations of phase change gel anti-channeling agents on the API high-temperature and high-pressure water loss and thickening time of the high-temperature anti-channeling cementing system within the temperature range of 150-200℃ were systematically studied. Detailed experimental results are shown in Table 3.

[0094] The formula for the 150℃ high-temperature anti-channeling cementing system is: 100 parts by weight of oil well cement + 35 parts by weight of silica sand + 2 parts by weight of retarder + 0.3 parts by weight of defoamer + 52 parts by weight of water + 1-5 parts by weight of phase change gel anti-channeling agent + 2 parts by weight of polyethyleneimine.

[0095] The formula for the 180℃ high-temperature anti-channeling cementing system is: 100 parts by weight of oil well cement + 45 parts by weight of silica sand + 3 parts by weight of retarder + 0.3 parts by weight of defoamer + 52 parts by weight of water + 1-5 parts by weight of phase change gel anti-channeling agent + 2 parts by weight of polyethyleneimine.

[0096] The formula for the 200℃ high-temperature anti-channeling cementing system is: 100 parts by weight of oil well cement + 55 parts by weight of silica sand + 4 parts by weight of retarder + 0.3 parts by weight of defoamer + 52 parts by weight of water + 1-5 parts by weight of phase change gel anti-channeling agent + 2 parts by weight of polyethyleneimine.

[0097] Table 3 Comparison of performance of different high-temperature anti-channeling cementing systems

[0098]

[0099]

[0100] The phase change gel anti-channeling agent of this invention belongs to the sulfonic acid polymer family. Based on the electrostatic adsorption between sulfonic acid groups and cement particles and the polymer film-forming mechanism, different types of phase change gel anti-channeling agents possess strong high-temperature and high-pressure water loss reduction performance. The advantage of this invention lies in the fact that the phase change gel anti-channeling agent in the cement slurry begins to cross-link with polyethyleneimine under high-temperature stimulation during the thickening stage. Subsequently, during the settling period, it undergoes an in-situ phase change to form a polymer network structure with higher strength. This network structure is a closed polymer gel layer, improving the porosity of cement particles and thus significantly reducing cement slurry filtration loss and filter cake thickness. Experimental results show that the whisker-grafted phase change gel anti-channeling agent possesses a denser gel network, thus significantly reducing cement slurry filtration loss and filter cake thickness. Furthermore, the electrostatic adsorption principle of the sulfonic acid groups and the water-binding mechanism of the gel structure delay cement solidification to a certain extent, and the strong temperature resistance of the phase change gel anti-channeling agent also exhibits a retarding effect at 200℃. However, phase change gel anti-channeling agents have a weak retarding effect; even if a strong gel network has thickening properties, it will not cause abnormal thickening.

[0101] Test Example 4

[0102] Each high-temperature anti-channeling cementing system was aged for 120 minutes in a high-temperature, high-pressure thickener at 150℃, 180℃, and 200℃, respectively. The gas permeability before initial setting was then determined according to the national standard GB / T 19139-2003, "Test Methods for Oil Well Cement". In addition, each system was aged for 20 minutes in a 90℃ atmospheric pressure thickener, and the static gel strength transition time at 150℃, 180℃, and 200℃ was determined according to the industry standard SY / T 5504.5-2010, "Test Methods for Performance of Oil Well Cement Slurry Part 5". All experimental results are summarized in Table 4.

[0103] Table 4 Anti-channeling performance of different high-temperature anti-channeling cementing systems

[0104]

[0105] During the cementing stage, high-temperature conditions trigger the formation of a strong and tough gel network structure within the cement slurry by the phase change gel anti-channeling agent. This gel network, in synergy with nano-scale toughening whiskers, constructs a sealed gel layer, effectively reducing the permeability of the cement slurry during hydration and significantly increasing the flow resistance of high-pressure formation gas penetrating the slurry. The gel-sealing structure effectively prevents gas migration along weak points in the cement slurry by enhancing the sealing performance of the micropores within the slurry. Experimental data show that the whisker-grafted modified gel network has higher mechanical strength, further reducing the permeability of the cement slurry and significantly shortening the transition time of the cement slurry through rapid formation of a high-strength gel. Thanks to the precise controllability of the gelation time of the phase change gel anti-channeling agent and the highly efficient activity of the cross-linking reaction under high-temperature conditions, the static gelation strength of the cement slurry can be rapidly formed in a very short time, and its static gelation transition time can be shortened to approximately 1 minute.

[0106] Test Example 5

[0107] High-temperature anti-channeling cementing cement was prepared by mixing according to API standards and filled into 25mm×50mm cylindrical molds and 40mm×40mm×160mm prismatic molds. The cement was then cured at 150-200℃ and 20MPa for 72 hours. After demolding and polishing, the compressive strength, flexural strength, and modulus of elasticity of the cured cement samples were tested using an E45.605 electronic universal testing machine and a WDW-10 flexural testing machine, respectively, to examine the anti-channeling performance of the high-temperature anti-channeling cementing cement system in the later stages.

[0108] Table 5 Mechanical properties of different high-temperature anti-channeling cementing systems

[0109]

[0110] The phase change gel anti-channeling agent exhibits significant technical advantages through grafting nanocrystals. This high-strength, high-toughness cement additive can simultaneously achieve multiple performance improvements, enhancing the compressive and flexural strength of cementing cement at different temperatures while effectively reducing the elastic modulus. More importantly, its self-assembled gel network structure further endows the cured cement with excellent elastic and tough properties, also contributing to reducing the elastic modulus of the cement stone. Furthermore, silica-encapsulated whiskers, based on the volcanic ash reaction, strengthen the bonding strength between hydration products and whiskers, further improving the mechanical properties of the cement stone. Compared to conventional cement stone without additives, non-in-situ cross-linked cement stone, and whiskerless cement stone, the cement stone cured based on the gel-reinforced anti-channeling agent of this invention can achieve compressive strength increases of 13%, 2%, and 18%, respectively; flexural strength increases of 166%, 14%, and 43%, respectively; and elastic modulus reductions of 43%, 42%, and 28%. This unique combination of high strength and low elastic modulus enables cured cement to better adapt to complex underground environments and heterogeneous stress conditions, effectively suppressing crack formation and thus preventing gas leakage through cracks in the cement sheath.

[0111] In summary, the phase change gel anti-channeling agent of this invention undergoes a phase transition reaction with polyethyleneimine induced by a high-temperature (150°C) in-situ crosslinking reaction to form a gel system. The gelation time and strength can be precisely controlled by adjusting the concentration of the anti-channeling agent and the amount of polyethyleneimine used. The phase change gel anti-channeling agent has advantages in improving the filtration properties of cement slurry at high temperatures of 150-200°C, and based on its thermally responsive phase change gelation characteristics, it reduces the permeability of the cement slurry and shortens its static gelation transition time. Through the synergistic effect of silica-encapsulated whisker grafts and the internal polymer network, the mechanical properties and elasticity of the cement slurry are comprehensively improved, thereby effectively inhibiting the formation of channeling fractures in the cement stone. This phase change gel anti-channeling agent provides a reliable solution for cementing operations in high-temperature lost circulation deep wells, ensuring both cementing quality and maintaining the long-term sealing integrity of the wellbore. Its excellent performance and wide applicability indicate significant commercial application prospects and market value.

Claims

1. A method for preparing a thermally responsive phase change gel anti-channeling agent, characterized in that, The phase change gel antichanneling agent is a functionalized thermally responsive polymer grafted whiskers, wherein the constituent monomers of the functionalized thermally responsive polymer are the primary amide monomer shown in Formula 1, the alkyl acrylamide monomer shown in Formula 2, and the sulfonic acid monomer shown in Formula 3. Among them, the R1 group of Formula 1, the R2 group of Formula 2 and the R3 group of Formula 3 in the monomer may be the same or different, and can be H, methyl, ethyl, or isopropyl. The functionalized thermally responsive polymer is synthesized with the following monomer mass ratio: 4-12 parts by mass of primary amide monomer, 6-15 parts by mass of alkyl acrylamide monomer, and 8-20 parts by mass of sulfonic acid monomer. The preparation method of the phase change gel antichanneling agent includes the following steps: (1) Mix 6-18 parts by mass of silicon source and 10 parts by mass of anhydrous ethanol, and after complete dissolution, form a silicon source solution. Add 68-136 parts by mass of anhydrous ethanol, 10-20 parts by mass of deionized water, 1-5 parts by mass of catalyst and 2-6 parts by mass of whiskers into a glass container, stir at 300 rpm for 40 min, and then sonicate for 30-40 min. Raise the temperature of the above solution to 40-60℃ at 300-450 rpm, and then inject the silicon source solution into the glass container at an injection rate of 0.5-1.5 mL / min using a high-pressure injection pump. Continue the reaction for 10-12 h, filter under reduced pressure and wash the solid three times with anhydrous ethanol to obtain silicon dioxide-coated whiskers with a yield of 87-95%. (2) Take 4-8 parts by weight of silica-coated whiskers, 68-136 parts by weight of anhydrous ethanol, 10-20 parts by weight of deionized water and 1-5 parts by weight of catalyst and place them in a glass container. Stir at 300 rpm for 40 min, then sonicate for 30-40 min. Then raise the temperature of the solution to 50-60℃ at 400-600 rpm. Mix 0.2-0.8 parts by weight of silane coupling agent and 1 part by weight of deionized water to form a coupling agent solution. Then inject the coupling agent solution into the glass container at an injection rate of 0.1-1 mL / min using a high-pressure injection pump. Continue the reaction for 2-6 h. Filter under reduced pressure and wash the solid three times with anhydrous ethanol to obtain allyl whiskers with a yield of 90-94%. (3) Add the primary amide monomer, alkyl acrylamide monomer and sulfonic acid monomer to a glass container, add 120-160 parts by weight of deionized water, adjust the pH of the monomer solution to 6-8 using sodium hydroxide solution, and then add 0.36-1.8 parts by weight of allyl whiskers and 0.1-0.4 parts by weight of initiator in sequence to prepare an aqueous solution of monomer; (4) Continuously introduce high-purity nitrogen into the reaction vessel to remove oxygen, control the stirring rate to 350-600 rpm, raise the temperature of the monomer aqueous solution to between 50-80℃, maintain the polymerization reaction for 6-10 hours, and obtain the phase change gel anti-channeling agent after natural cooling, with a solid content of 16.8-17.4%.

2. The method for preparing the phase change gel anti-channeling agent according to claim 1, characterized in that, The silicon source is ethyl silicate, one of sodium silicate.

3. The method for preparing the phase change gel anti-channeling agent according to claim 1, characterized in that, The catalyst is one of sodium hydroxide, ammonia, and hydrochloric acid.

4. The method for preparing the phase change gel anti-channeling agent according to claim 1, characterized in that, The whiskers are one of calcium carbonate whiskers, calcium sulfate whiskers, magnesium hydroxide whiskers, potassium titanate whiskers, and silicon carbide whiskers.

5. The method for preparing the phase change gel anti-channeling agent according to claim 1, characterized in that, The silane coupling agent is one of γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

6. The method for preparing the phase change gel anti-channeling agent according to claim 1, characterized in that, The initiator is one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride, and azobisisobutylimidazoline hydrochloride.

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