Well cementation cement paste, high-temperature-resistant modified poly-p-phenylene terephthamide fiber toughening agent for well cementation and preparation method of toughening agent

Abstract

The invention belongs to the technical field of petroleum and natural gas exploration and development, and particularly discloses well cementation cement paste, a high-temperature-resistant modified poly-p-phenylene terephthamide fiber toughening agent for well cementation and a preparation method of the high-temperature-resistant modified poly-p-phenylene terephthamide fiber toughening agent. The high-temperature-resistant modified poly (p-phenylene terephthamide) fiber toughening agent for well cementation is prepared from the following raw materials in parts by weight: 1 to 5 parts of p-phenylenediamine, 5 to 10 parts of terephthaloyl chloride, 5 to 30 parts of calcium chloride, 5 to 30 parts of N-methyl pyrrolidone and 80 to 100 parts of deionized water. The well cementation cement slurry is prepared from the following raw materials in parts by weight: 1-3 parts of a high-temperature-resistant modified poly-p-phenylene terephthamide fiber toughening agent for well cementation, 100 parts of cement, 35-45 parts of quartz sand, 2-4 parts of a high-temperature-declining-resistant agent, 1-3 parts of a retarder, 2-4 parts of a suspension stabilizer, 2-4 parts of a fluid loss agent and 44-48 parts of clear water. The mechanical property of the set cement at the temperature of 180 DEG C or above is remarkably improved, particularly the toughness and plasticity of the set cement are enhanced, and the elastic modulus of the set cement is remarkably reduced, so that the purpose of enhancing the toughness of the set cement is achieved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development technology, specifically to a cementing slurry, a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, and their preparation methods. Background Technology

[0002] As oil and gas exploration continues to advance into deeper levels, the number of complex deep wells is increasing. The wellbore temperature in these deep and ultra-deep wells is rising continuously, with bottom hole temperatures even exceeding 180°C. Because oil well cement stone is inherently brittle, microcracks easily form in complex deep well environments, weakening its strength and compromising the integrity of the cement sheath. This affects the safe operation of oil and gas wells and can even lead to significant economic losses. Furthermore, the sealing performance of the cement sheath after curing under high-temperature conditions is often difficult to maintain, leading to increasingly serious sealing failure problems. Therefore, developing cementing slurry technology suitable for high-temperature environments is crucial for ensuring the safety of oil and gas exploration and development in complex deep wells.

[0003] Under high-temperature conditions, cement stone is brittle and prone to cracking, which may lead to a decrease in the sealing performance of the downhole cement sheath. To address this challenge, toughening agents are typically added to cement slurry in engineering to improve the toughness and ductility of the cement stone, thereby enhancing the long-term sealing capability of the cement sheath. For example, the invention patent "A Lightweight Toughened Cementing Material and Its Preparation Method" (CN 115872680 A) uses plant fiber, vacuum glass microspheres, and rubber powder as toughening materials to accelerate the initial setting strength development of the cement stone, enabling the early strength of the cement stone to reach 7.0 MPa, improving the toughness and impact resistance of the cement stone, with an elastic modulus of only 4.5–5.6 GPa. For example, the invention patent "A method for preparing an inorganic fiber toughening agent for cementing in oil and gas wells" (CN 11452119A) uses one or more fiber mixtures selected from nano-silica modified basalt fiber, carbon fiber, brucite fiber, and silicon carbide fiber as toughening materials, effectively reducing the brittleness of cement stone and improving its mechanical flexibility. However, this method is not suitable for cementing operations under ultra-high temperature conditions above 180℃. Another example is the invention patent "A cementing cement for ultra-high temperature deep wells and its preparation method and application" (CN 110563428A), which combines a first strength-reducing agent (silica powder) with a second strength-reducing agent to ensure that the compressive strength does not decrease at 200–240℃. However, this method does not modify the toughness of the cement stone.

[0004] While the existing technologies have achieved certain results in the mechanical modification of high-temperature cement, there are still some problems in the toughening of high-temperature cement stone, which cannot meet the cementing technology requirements of complex deep wells with bottom hole temperatures above 180℃. Summary of the Invention

[0005] This invention provides a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing stone and its preparation method, aiming to meet the cementing technology requirements of complex deep wells with bottom hole temperatures above 180℃.

[0006] The present invention is achieved through the following technical solution: a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, comprising the following raw materials in parts by weight: 1-5 parts of p-phenylenediamine, 5-10 parts of terephthaloyl chloride, 5-30 parts of calcium chloride, 5-30 parts of N-methylpyrrolidone, and 80-100 parts of deionized water.

[0007] Furthermore, a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 10 parts calcium chloride, 10 parts N-methylpyrrolidone, and 100 parts deionized water.

[0008] Furthermore, a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 20 parts calcium chloride, 20 parts N-methylpyrrolidone, and 100 parts deionized water.

[0009] Furthermore, a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 30 parts calcium chloride, 30 parts N-methylpyrrolidone, and 100 parts deionized water.

[0010] The preparation method of the high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, as described above, includes the following steps:

[0011] Step a, obtain poly(p-phenylene terephthalamide) fibers;

[0012] Step b involves modifying the poly(p-phenylene terephthalamide) fiber obtained in step a to obtain a modified poly(p-phenylene terephthalamide) fiber toughening agent, including the following steps:

[0013] Step b1: Lay the poly(p-phenylene terephthalamide) fiber obtained in step a flat under a UV lamp for irradiation, and then cut it into short fibers of 1-5 mm in length to obtain preliminarily modified poly(p-phenylene terephthalamide) fiber.

[0014] Step b2: The preliminarily modified poly(p-phenylene terephthalamide) fiber is placed in a plasma instrument, and the surface of the preliminarily modified poly(p-phenylene terephthalamide) fiber is etched by high-energy particles in the plasma to form a rough structure, thereby obtaining the secondary modified poly(p-phenylene terephthalamide) fiber.

[0015] Step b3: Place the secondary modified poly(p-phenylene terephthalamide) fiber in a reaction vessel, and introduce SO3 gas into the vessel to introduce sulfonic acid bonds into the secondary modified poly(p-phenylene terephthalamide) fiber, thereby obtaining a modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0016] Furthermore, obtaining poly(p-phenylene terephthalamide) fibers in step a includes the following steps:

[0017] Step a1: Weigh the N-methylpyrrolidone and calcium chloride, dissolve them in a solvent, and stir until homogeneous to obtain a composite solution. The weight ratio of the N-methylpyrrolidone and calcium chloride to the solvent is 1:10-20.

[0018] Step a2: Weigh the terephthaloyl chloride and add it to the composite solution, then place it in a freezer bath to cool to -10 to -20°C and stir at high speed for 30 to 60 minutes to obtain a PPTA solution;

[0019] Step a3: Centrifuge the PPTA solution for 30-90 minutes to degas it and obtain the spinning solution. Then, use water at 25°C as a coagulation bath and use a micro-injection pump to squeeze the centrifuged spinning solution into the coagulation bath to obtain wet fibers.

[0020] Step a4: Place the wet fiber into a beaker containing deionized water and stir to clean it. Then, use a vacuum filter to filter and dry the cleaned fiber. Repeat the above steps several times. Place the filtered fiber in a refrigerator to cool for 3-6 hours, and then use a freeze dryer to dry the cooled fiber for 24-48 hours to obtain poly(p-phenylene terephthalamide) fiber.

[0021] Furthermore, the solvent is at least one of water and ethanol.

[0022] Furthermore, the solvent is ethanol, and the total weight ratio of N-methylpyrrolidone and calcium chloride to ethanol is 1:10.

[0023] Furthermore, the solvent is water, and the total weight ratio of N-methylpyrrolidone and calcium chloride to water is 1:15.

[0024] Furthermore, the solvent is a mixture of water and ethanol, and the total weight ratio of N-methylpyrrolidone and calcium chloride to the weight ratio of water and ethanol is 1:10:10.

[0025] A cementing slurry is made from the following raw materials in parts by weight: 1-3 parts of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing as described above, 100-120 parts of cement, 35-45 parts of quartz sand, 2-4 parts of anti-high-temperature degradation agent, 1-3 parts of retarder, 2-4 parts of suspension stabilizer, 2-4 parts of fluid loss reducing agent, and 44-48 parts of clean water.

[0026] Furthermore, a cementing slurry is prepared according to the following method, including the following steps:

[0027] Step c1: Dry mix cement, quartz sand and a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing to obtain a mixed dry material;

[0028] Step c2: Dissolve the anti-high temperature degradation agent, retarder, suspension stabilizer and water loss reducer in water and stir evenly to obtain a mixed wet material;

[0029] Step c3: Add the dry mixture from step c1 to the wet mixture obtained in step c2 and stir evenly to obtain a cementing slurry containing high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing cement stone.

[0030] Furthermore, the quartz sand is composed of 200-mesh acid-washed quartz sand and 400-mesh acid-washed quartz sand, and the mass ratio of 200-mesh acid-washed quartz sand to 400-mesh acid-washed quartz sand is 2:1.

[0031] Further, in step c3, the stirring process is first rotated at a low speed (4000±200r / min), and the weighed dry powder mixture is added within 10 to 20 seconds. Then, the lid of the stirrer is closed, and stirring is continued at a high speed (12000±500r / min) for 35 to 40 seconds to obtain a cementing slurry containing high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] In this invention, the mechanism by which modified poly(p-phenylene terephthalamide) fibers enhance their toughness includes: the modification process improves the surface properties of the fibers and increases their hydrophilicity, allowing the fibers to be distributed more uniformly in the cement matrix, thereby helping to reduce stress concentration points, enhance the adhesion between the fibers and the cement matrix, and improve their load-bearing capacity and modulus of elasticity. Furthermore, when the material is subjected to tensile force, the stress transfer between the fibers and the cement matrix is ​​more efficient, and the bonding force between the two is enhanced. Simultaneously, due to the inherent high modulus of elasticity of poly(p-phenylene terephthalamide) fibers, the enhanced interfacial adhesion allows the fibers to withstand more stress.

[0034] Compared with the prior art, the high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent of the present invention and the cementing cement made using the toughening agent have the following beneficial effects:

[0035] (1) This invention utilizes and modifies the innovative material poly(p-phenylene terephthalamide) fiber to serve as a high-temperature toughening agent for cementing stone. This treatment effectively ensures the strength and toughness of the cement stone under high-temperature conditions, thereby guaranteeing the safe production of oil and gas wells. It can meet the cementing technology requirements of complex deep wells with bottom hole temperatures above 180°C, significantly improves the mechanical properties of the cement stone at temperatures above 180°C, especially enhancing its toughness and plasticity, and significantly reducing the elastic modulus of the cement stone, thereby achieving the purpose of enhancing the toughness of the cement stone.

[0036] (2) This invention modifies the surface of poly(p-phenylene terephthalamide) fibers by increasing the surface roughness. High-energy particles in plasma are used to etch the fiber surface, forming a rough structure. This structure enhances the bonding force between the fibers and the cement paste, making it more suitable for practical cementing applications.

[0037] (3) The cementing slurry system containing high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent provided by the present invention has excellent fluidity, excellent settling stability and low water loss, and has high practicality and a wide applicable temperature range. It can also overcome the adverse effects of high temperature on the strength of cement stone and meet the needs of cementing complex deep wells. Attached Figure Description

[0038] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 This is a thickening curve of the cement slurry in Example 1.

[0040] Figure 2 This is a thickening curve of the cement slurry in Example 2.

[0041] Figure 3 This is a thickening curve of the cement slurry in Example 3.

[0042] Figure 4 The image shows the thickening curve of the cement slurry in Comparative Example 1. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0044] Example 1

[0045] 1. Preparation of high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent

[0046] This embodiment 1 provides a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, which is made from the following raw materials in parts by weight: 1-5 parts of p-phenylenediamine (PPDA), 5-10 parts of terephthaloyl chloride (TPC), 5-30 parts of calcium chloride (CaCl2), 5-30 parts of N-methylpyrrolidone (NMP), and 80-100 parts of deionized water.

[0047] This embodiment describes a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, which is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 10 parts calcium chloride, 10 parts N-methylpyrrolidone, and 100 parts deionized water.

[0048] This embodiment describes a method for preparing a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, comprising the following steps:

[0049] Step a, obtain poly(p-phenylene terephthalamide) fibers;

[0050] In this embodiment, step a of obtaining poly(p-phenylene terephthalamide) fibers includes the following steps:

[0051] Step a1: Weigh N-methylpyrrolidone and calcium chloride, dissolve them in a solvent, and stir until homogeneous to obtain a composite solution. The total weight ratio of N-methylpyrrolidone and calcium chloride to the solvent is 1:10 to 20. The solvent is at least one of water and ethanol. In this example, the solvent is ethanol, and the total weight ratio of N-methylpyrrolidone and calcium chloride (NMP / CaCl2) to ethanol is 1:10.

[0052] Step a2: Weigh terephthaloyl chloride (TPC) and p-phenylenediamine (PPDA) and add them to the above composite solution. Place the solution in a freezer bath to cool to -10 to -20°C and stir at high speed for 30 to 60 minutes to obtain a PPTA solution (i.e., poly(p-phenylenediamine terephthaloyl chloride)). In this example, after weighing terephthaloyl chloride (TPC) and p-phenylenediamine (PPDA) and adding them to the above composite solution, place the solution in a freezer bath to cool to -10°C and stir at high speed for 30 minutes.

[0053] Step a3: Centrifuge the PPTA solution for 30-90 minutes to remove bubbles (in this example, centrifugation for 30 minutes is used as an example) to obtain the spinning solution. Then, use water at 25°C as a coagulation bath and use a micro-injection pump to squeeze the centrifuged spinning solution into the coagulation bath to obtain wet fibers.

[0054] Step a4: Place the wet fiber into a beaker containing deionized water and stir to clean it. Then, use a vacuum filter to filter and dry the cleaned fiber. Repeat the above steps 3 times. Place the filtered fiber in a refrigerator to cool for 3-6 hours (3 hours in this example). Then, use a freeze dryer to dry the cooled fiber for 24-48 hours (24 hours in this example) to obtain poly(p-phenylene terephthalamide) fiber.

[0055] Step b involves modifying the poly(p-phenylene terephthalamide) fibers obtained in step a to obtain a modified poly(p-phenylene terephthalamide) fiber toughening agent. This step modifies the poly(p-phenylene terephthalamide) fibers obtained in step a to enhance the bonding strength between the poly(p-phenylene terephthalamide) fibers and the cement matrix, and includes the following steps:

[0056] Step b1: Lay the poly(p-phenylene terephthalamide) fiber obtained in step a flat at 15cm below the UV lamp and irradiate it for 8min. Then cut it into short fibers of 1-5mm in length (in this embodiment, it is cut into short fibers of 3mm in length) to obtain the preliminarily modified poly(p-phenylene terephthalamide) fiber.

[0057] Step b2: The preliminarily modified poly(p-phenylene terephthalamide) fiber is placed in a plasma instrument. The gas pressure inside the plasma instrument is evacuated to a vacuum of 40 Pa, the working atmosphere is O2, the discharge power is 200 W, and the processing time is 1-3 min (1 min in this embodiment). The high-energy particles in the plasma are used to etch the surface of the preliminarily modified poly(p-phenylene terephthalamide) fiber to form a rough structure, which facilitates the improvement of the bonding force between the fiber and the cement matrix, thus obtaining the secondary modified poly(p-phenylene terephthalamide) fiber.

[0058] Step b3: Place the secondary modified poly(p-phenylene terephthalamide) fiber in a reaction vessel, and introduce SO3 gas into the vessel to introduce sulfonic acid bonds into the secondary modified poly(p-phenylene terephthalamide) fiber, further enhancing its hydrophilicity, and obtain the modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0059] All substances mentioned above are in parts by weight.

[0060] All of the substances mentioned above are commercially available.

[0061] 2. Preparation of cement slurry

[0062] A cementing slurry is made from the following raw materials in parts by weight: 1-3 parts of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing as described above, 100-120 parts of cement, 35-45 parts of quartz sand, 2-4 parts of anti-high-temperature degradation agent, 1-3 parts of retarder, 2-4 parts of suspension stabilizer, 2-4 parts of fluid loss reducing agent, and 44-48 parts of clean water.

[0063] The cement is Grade G oil well cement, and the quartz sand is composed of 200-mesh and 400-mesh acid-washed quartz sand, with a mass ratio of 200-mesh to 400-mesh acid-washed quartz sand of 2:1. The retarder can be 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, N-vinylpyrrolidone, or acrylamide polymers.

[0064] In this embodiment, a cementing slurry is prepared according to the following method, including the following steps:

[0065] Step c1: Dry mix cement, quartz sand and one of the above-mentioned high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agents for cementing to obtain a mixed dry material. Specifically: weigh 100 parts by weight of G-grade oil well cement, 35 parts by weight of 200-mesh quartz sand, and 1 part by weight of high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent, and mix them to obtain a dry material.

[0066] Step c2: Dissolve the anti-high temperature degradation agent, retarder, suspension stabilizer, and water loss reducer in water and stir evenly to obtain a mixed wet material. Specifically: Measure 44 parts by weight of water, weigh 0.3 parts by weight of anti-high temperature degradation agent, 2 parts by weight of retarder (2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / N-vinylpyrrolidone / acrylamide polymer), 2 parts by weight of suspension stabilizer, and 4 parts by weight of water loss reducer, dissolve in water and stir evenly to obtain a mixed solution (i.e., mixed wet material);

[0067] Step c3: Add the dry mixture from step c1 to the wet mixture obtained in step c2 and stir evenly to obtain a cementing slurry containing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing cement stone. In step c3, the stirring process is first rotated at a low speed (4000±200r / min), and the weighed dry powder mixture is added within 10-20s. Then, the lid of the stirrer is closed, and stirring is continued at a high speed (12000±500r / min) for 35-40s to obtain a cementing slurry containing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0068] Example 2

[0069] 1. Preparation of high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent

[0070] The difference between this embodiment and Embodiment 1 is that: a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine (PPDA), 5 parts terephthaloyl chloride (TPC), 20 parts calcium chloride (CaCl2), 20 parts N-methylpyrrolidone (NMP), and 100 parts deionized water.

[0071] This embodiment describes a method for preparing a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, comprising the following steps:

[0072] Step a, obtain poly(p-phenylene terephthalamide) fibers;

[0073] In this embodiment, step a of obtaining poly(p-phenylene terephthalamide) fibers includes the following steps:

[0074] Step a1: Weigh N-methylpyrrolidone and calcium chloride, dissolve them in a solvent, and stir until homogeneous to obtain a composite solution. In this example, the solvent is water, and the total weight ratio of N-methylpyrrolidone and calcium chloride (NMP / CaCl2) to water is 1:15.

[0075] Step a2: Weigh terephthaloyl chloride (TPC) and p-phenylenediamine (PPDA) and add them to the above composite solution. Place the solution in a freezer bath to cool to -15°C and stir at high speed for 40 minutes to obtain a PPTA solution.

[0076] Step a3: Centrifuge the PPTA solution for 40 minutes to remove bubbles and obtain the spinning solution. Then, use water at 25°C as a coagulation bath and use a micro-injection pump to squeeze the centrifuged spinning solution into the coagulation bath to obtain wet fibers.

[0077] Step a4: Place the wet fiber into a beaker containing deionized water and stir to clean it. Then, use a vacuum filter to filter and dry the cleaned fiber. Repeat the above steps 3 times. Place the filtered fiber in a refrigerator to cool for 4 hours, and then use a freeze dryer to dry the cooled fiber for 36 hours to obtain poly(p-phenylene terephthalamide) fiber.

[0078] Step b involves modifying the poly(p-phenylene terephthalamide) fibers obtained in step a to obtain a modified poly(p-phenylene terephthalamide) fiber toughening agent. This step modifies the poly(p-phenylene terephthalamide) fibers obtained in step a to enhance the bonding strength between the poly(p-phenylene terephthalamide) fibers and the cement matrix, and includes the following steps:

[0079] Step b1: Lay the poly(p-phenylene terephthalamide) fiber obtained in step a flat 15cm below the UV lamp and irradiate it for 10min. Then cut it into short fibers with a length of 3mm to obtain the preliminarily modified poly(p-phenylene terephthalamide) fiber.

[0080] Step b2: The preliminarily modified poly(p-phenylene terephthalamide) fiber is placed in a plasma instrument. The pressure inside the plasma instrument is evacuated to a vacuum of 40 Pa. The working atmosphere is O2, the discharge power is 200 W, and the processing time is 2 min. The high-energy particles in the plasma are used to etch the surface of the preliminarily modified poly(p-phenylene terephthalamide) fiber to form a rough structure, which facilitates the improvement of the bonding force between the fiber and the cement matrix, thus obtaining the secondary modified poly(p-phenylene terephthalamide) fiber.

[0081] Step b3: Place the secondary modified poly(p-phenylene terephthalamide) fiber in a reaction vessel, and introduce SO3 gas into the vessel to introduce sulfonic acid bonds into the secondary modified poly(p-phenylene terephthalamide) fiber, further enhancing its hydrophilicity, and obtain the modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0082] All substances mentioned above are in parts by weight.

[0083] All of the substances mentioned above are commercially available.

[0084] 2. Preparation of cement slurry

[0085] A cementing slurry is made from the following raw materials in parts by weight: 1-3 parts of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing as described above, 100-120 parts of cement, 35-45 parts of quartz sand, 2-4 parts of anti-high-temperature degradation agent, 1-3 parts of retarder, 2-4 parts of suspension stabilizer, 2-4 parts of fluid loss reducing agent, and 44-48 parts of clean water.

[0086] The cement is Grade G oil well cement, and the quartz sand is composed of 200-mesh and 400-mesh acid-washed quartz sand, with a mass ratio of 200-mesh to 400-mesh acid-washed quartz sand of 2:1. The retarder can be 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, N-vinylpyrrolidone, or acrylamide polymers.

[0087] The cement slurry in this embodiment differs from that in Embodiment 1 in that it is prepared according to the following method, including the following steps:

[0088] Step c1: Dry mix cement, quartz sand and one of the above-mentioned high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agents for cementing to obtain a mixed dry material. Specifically: weigh 100 parts by weight of G-grade oil well cement, 35 parts by weight of 200-mesh quartz sand, and 2 parts by weight of high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent, and mix them to obtain a dry material.

[0089] Step c2: Dissolve the anti-high temperature degradation agent, retarder, suspension stabilizer, and water loss reducer in water and stir evenly to obtain a mixed wet material. Specifically: Measure 44 parts by weight of water, weigh 0.3 parts by weight of anti-high temperature degradation agent, 2 parts by weight of retarder (2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / N-vinylpyrrolidone / acrylamide polymer), 2 parts by weight of suspension stabilizer, and 4 parts by weight of water loss reducer, dissolve in water and stir evenly to obtain a mixed solution (i.e., mixed wet material);

[0090] Step c3: Add the dry mixture from step c1 to the wet mixture obtained in step c2 and stir evenly to obtain a cementing slurry containing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing cement stone. In step c3, the stirring process is first rotated at a low speed (4000±200r / min), and the weighed dry powder mixture is added within 10-20s. Then, the lid of the stirrer is closed, and stirring is continued at a high speed (12000±500r / min) for 35-40s to obtain a cementing slurry containing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0091] Example 3

[0092] 1. Preparation of high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent

[0093] The difference between this embodiment and Embodiment 1 is that: a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine (PPDA), 5 parts terephthaloyl chloride (TPC), 30 parts calcium chloride (CaCl2), 30 parts N-methylpyrrolidone (NMP), and 100 parts deionized water.

[0094] This embodiment describes a method for preparing a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, comprising the following steps:

[0095] Step a, obtain poly(p-phenylene terephthalamide) fibers;

[0096] In this embodiment, step a of obtaining poly(p-phenylene terephthalamide) fibers includes the following steps:

[0097] Step a1: Weigh N-methylpyrrolidone and calcium chloride, dissolve them in a solvent, and stir until homogeneous to obtain a composite solution. In this example, the solvent is a mixture of water and ethanol. The total weight of N-methylpyrrolidone and calcium chloride (NMP / CaCl2) is in the weight ratio of water and ethanol to 1:10:10.

[0098] Step a2: Weigh terephthaloyl chloride (TPC) and p-phenylenediamine (PPDA) and add them to the above composite solution. Place the solution in a freezer bath to cool to -20°C and stir at high speed for 50 minutes to obtain a PPTA solution.

[0099] Step a3: Centrifuge the PPTA solution for 50 minutes to remove bubbles and obtain the spinning solution. Then, use water at 25°C as a coagulation bath and use a micro-injection pump to squeeze the centrifuged spinning solution into the coagulation bath to obtain wet fibers.

[0100] Step a4: Place the wet fiber into a beaker containing deionized water and stir to clean it. Then, use a vacuum filter to filter and dry the cleaned fiber. Repeat the above steps 3 times. Place the filtered fiber in a refrigerator to cool for 5 hours, and then use a freeze dryer to dry the cooled fiber for 48 hours to obtain poly(p-phenylene terephthalamide) fiber.

[0101] Step b involves modifying the poly(p-phenylene terephthalamide) fibers obtained in step a to obtain a modified poly(p-phenylene terephthalamide) fiber toughening agent. This step modifies the poly(p-phenylene terephthalamide) fibers obtained in step a to enhance the bonding strength between the poly(p-phenylene terephthalamide) fibers and the cement matrix, and includes the following steps:

[0102] Step b1: Lay the poly(p-phenylene terephthalamide) fiber obtained in step a flat at 15cm below the UV lamp and irradiate it for 12min. Then cut it into short fibers of 3mm in length to obtain the preliminarily modified poly(p-phenylene terephthalamide) fiber.

[0103] Step b2: The preliminarily modified poly(p-phenylene terephthalamide) fiber is placed in a plasma instrument. The gas pressure inside the plasma instrument is evacuated to a vacuum of 40 Pa. The working atmosphere is O2, the discharge power is 200 W, and the processing time is 3 min. The high-energy particles in the plasma are used to etch the surface of the preliminarily modified poly(p-phenylene terephthalamide) fiber to form a rough structure, which facilitates the improvement of the bonding force between the fiber and the cement matrix, thus obtaining the secondary modified poly(p-phenylene terephthalamide) fiber.

[0104] Step b3: Place the secondary modified poly(p-phenylene terephthalamide) fiber in a reaction vessel, and introduce SO3 gas into the vessel to introduce sulfonic acid bonds into the secondary modified poly(p-phenylene terephthalamide) fiber, further enhancing its hydrophilicity, and obtain the modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0105] All substances mentioned above are in parts by weight.

[0106] All of the substances mentioned above are commercially available.

[0107] 2. Preparation of cement slurry

[0108] A cementing slurry is made from the following raw materials in parts by weight: 1-3 parts of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing as described above, 100-120 parts of cement, 35-45 parts of quartz sand, 2-4 parts of anti-high-temperature degradation agent, 1-3 parts of retarder, 2-4 parts of suspension stabilizer, 2-4 parts of fluid loss reducing agent, and 44-48 parts of clean water.

[0109] The cement is Grade G oil well cement, and the quartz sand is composed of 200-mesh and 400-mesh acid-washed quartz sand, with a mass ratio of 200-mesh to 400-mesh acid-washed quartz sand of 2:1. The retarder can be 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, N-vinylpyrrolidone, or acrylamide polymers.

[0110] The cement slurry in this embodiment differs from that in Embodiment 1 in that it is prepared according to the following method, including the following steps:

[0111] Step c1: Dry mix cement, quartz sand and one of the above-mentioned high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agents for cementing to obtain a mixed dry material. Specifically: weigh 100 parts by weight of G-grade oil well cement, 35 parts by weight of 200-mesh quartz sand, and 3 parts by weight of high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent, and mix them to obtain a dry material.

[0112] Step c2: Dissolve the anti-high temperature degradation agent, retarder, suspension stabilizer, and water loss reducer in water and stir evenly to obtain a mixed wet material. Specifically: Measure 44 parts by weight of water, weigh 0.3 parts by weight of anti-high temperature degradation agent, 2 parts by weight of retarder (2-acrylamido-2-methylpropanesulfonic acid / itaconic acid / N-vinylpyrrolidone / acrylamide polymer), 2 parts by weight of suspension stabilizer, and 4 parts by weight of water loss reducer, dissolve in water and stir evenly to obtain a mixed solution (i.e., mixed wet material);

[0113] Step c3: Add the dry mixture from step c1 to the wet mixture obtained in step c2 and stir evenly to obtain a cementing slurry containing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing cement stone. In step c3, the stirring process is first rotated at a low speed (4000±200r / min), and the weighed dry powder mixture is added within 10-20s. Then, the lid of the stirrer is closed, and stirring is continued at a high speed (12000±500r / min) for 35-40s to obtain a cementing slurry containing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0114] Comparative Example 1

[0115] 1. Preparation of cement slurry

[0116] Weigh 100 parts by weight of Grade G oil well cement and 35 parts by weight of 200-mesh quartz sand to obtain a dry mixture. Measure 44 parts by weight of clean water, and weigh 0.3 parts by weight of anti-high temperature degradation agent, 2 parts by weight of retarder, 2 parts by weight of suspension stabilizer, and 4 parts by weight of fluid loss reducer. Dissolve them in water and stir evenly to obtain a mixed solution. Prepare a sand-added cement system according to standard GB / T 19139-2012. Pour the mixed solution into a mixing cup, use a stirrer to rotate at a low speed (4000±200) r / min, and add the weighed dry powder mixture within 10-20 seconds. Cover the stirrer and continue stirring at a high speed (12000±500) r / min for 35-40 seconds to obtain a cementing slurry without cementing high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent.

[0117] (1) Engineering performance testing of cement grout system

[0118] According to the national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells", the cementing slurries of Examples 1-3 and Comparative Example 1 were tested for engineering performance. The test results are shown in Table 1. The thickening curves of the cement slurries of Examples 1-3 and Comparative Example 1 are shown in the figure below. Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown.

[0119] Table 1

[0120]

[0121] As shown in Table 1, the toughening agent provided by this invention has minimal impact on the density and fluidity of the cement slurry. After incorporating the toughening agent, the cement slurry exhibits lower free fluid and water loss, a stable thickening curve without any core bulging, and controllable thickening time. The overall performance of the cement slurry system meets the requirements for cementing operations under high-temperature environments.

[0122] (2) Compressive strength test of cement stone at different ages

[0123] The cement slurries of Examples 1-3 and Comparative Example 1 were placed in a high-temperature and high-pressure curing autoclave at 180℃×115MPa for 3 days, 7 days, 14 days, and 28 days, respectively. The compressive strength, tensile strength, and Young's modulus of the cement stone were tested according to standard SY / T 6466-2000 "Evaluation Method for High-Temperature Resistance of Oil Well Cement Stone" to evaluate the reinforcing and toughening effect of the modified poly(p-phenylene terephthalamide) fiber oil well cement stone. The test results are shown in Tables 2, 3, and 4.

[0124] Table 2

[0125]

[0126] Table 3

[0127]

[0128] Table 4

[0129]

[0130] According to the test results in Tables 2-3, under high-temperature conditions, the compressive and tensile strengths of Comparative Example 1 are relatively low, which negatively impacts the integrity of the cement ring. Examples 1-3 of this invention successfully improved the elasticity and toughness of the cement stone and enhanced its compressive strength to a certain extent by adding different amounts of modified poly(p-phenylene terephthalamide) fiber to the cement slurry. Under high-temperature curing conditions of 180℃, compared with Comparative Example 1, the cement stone using the toughening formula of this invention exhibited significantly improved compressive and tensile strengths at different curing stages, and the rate of decline in compressive and tensile strength was low after 28 days of curing. In Examples 1-3, the compressive strength of the cement stone after 7 days of curing reached 1.5-2 times that of Comparative Example 1, and the compressive strength of the cement stone after 28 days of curing was still 50-70% higher than that of Comparative Example 1.

[0131] As shown in Table 4, compared to Example 1, the cement slurry prepared using this toughening agent produces cement stone with a lower elastic modulus, exhibiting good flexibility and strong elastic deformation capacity. This property helps reduce damage to the cement sheath during downhole operations, minimizes the impact of subsequent cementing operations on sealing quality, thereby extending the service life of oil and gas wells and improving recovery rates.

[0132] In summary, the modified poly(p-phenylene terephthalamide) fiber toughening agent of this invention exhibits excellent compatibility with cement slurry systems, significantly improving the toughness and high-temperature stability of cementitious stone. This toughening agent successfully solves the problem of unevenness that easily occurs when traditional cement toughening materials are mixed with cement slurry, significantly improving key mechanical properties such as the toughness and crack resistance of cement stone, without negatively impacting the workability of the cement slurry. Therefore, the toughening agent of this invention has broad application potential.

[0133] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0134] In the description of this invention, it should be noted that the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0135] In the description of this document, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the attached drawings. They are only used to describe the relative positional relationship between the components or parts and do not specifically limit the specific installation orientation of each component or part.

[0136] In the description of this document, some terms may be used to indicate not only orientation or positional relationship, but also other meanings. For example, the term "above" may also be used in some cases to indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances.

[0137] In the description of this document, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0138] The structures, proportions, sizes, etc., drawn in the accompanying drawings in this application are only used to complement the content disclosed in this technical disclosure for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modification of the structure, change of the proportion relationship, or adjustment of the size shall still fall within the scope of the technical content disclosed in this application, provided that it does not affect the effect and purpose that this application can produce.

[0139] The terminology used in this document is that which is currently widely used in the art in consideration of the functionality of this disclosure; however, these terms may vary depending on the intent, precedent, or new technology of those skilled in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of this disclosure. Therefore, the terminology used in this document should not be construed as simple names, but rather based on the meaning of the terms and the overall description of this disclosure.

[0140] This document uses flowcharts or text to illustrate the operational steps performed according to embodiments of this application. It should be understood that the operational steps in the embodiments of this application are not necessarily performed precisely in the order described. Instead, as needed, various steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more operations can be removed from these processes.

[0141] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing, characterized in that, It is made from the following raw materials in parts by weight: 1-5 parts p-phenylenediamine, 5-10 parts terephthaloyl chloride, 5-30 parts calcium chloride, 5-30 parts N-methylpyrrolidone, and 80-100 parts deionized water.

2. The high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 10 parts calcium chloride, 10 parts N-methylpyrrolidone, and 100 parts deionized water.

3. The high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 2, characterized in that, It is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 20 parts calcium chloride, 20 parts N-methylpyrrolidone, and 100 parts deionized water.

4. The high-temperature modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 5 parts p-phenylenediamine, 5 parts terephthaloyl chloride, 30 parts calcium chloride, 30 parts N-methylpyrrolidone, and 100 parts deionized water.

5. A method for preparing a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing as described in any one of claims 1-4, characterized in that, Includes the following steps: Step a, obtain poly(p-phenylene terephthalamide) fibers; Step b involves modifying the poly(p-phenylene terephthalamide) fiber obtained in step a to obtain a modified poly(p-phenylene terephthalamide) fiber toughening agent, including the following steps: Step b1: Lay the poly(p-phenylene terephthalamide) fiber obtained in step a flat under a UV lamp and irradiate it for 8-12 minutes. Then cut it into short fibers with a length of 1-5 mm to obtain preliminarily modified poly(p-phenylene terephthalamide) fiber. Step b2: The preliminarily modified poly(p-phenylene terephthalamide) fiber is placed in a plasma instrument, and the surface of the preliminarily modified poly(p-phenylene terephthalamide) fiber is etched by high-energy particles in the plasma to form a rough structure, thereby obtaining the secondary modified poly(p-phenylene terephthalamide) fiber. Step b3: Place the secondary modified poly(p-phenylene terephthalamide) fiber in a reaction vessel, and introduce SO3 gas into the vessel to introduce sulfonic acid bonds into the secondary modified poly(p-phenylene terephthalamide) fiber, thereby obtaining a modified poly(p-phenylene terephthalamide) fiber toughening agent.

6. The preparation method of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 5, characterized in that, Step a involves obtaining poly(p-phenylene terephthalamide) fibers, including the following steps: Step a1: Weigh the N-methylpyrrolidone and calcium chloride, dissolve them in a solvent, and stir until homogeneous to obtain a composite solution. The total weight ratio of the N-methylpyrrolidone and calcium chloride to the weight of the solvent is 1:10-20. Step a2: Weigh the terephthaloyl chloride and p-phenylenediamine and add them to the composite solution, then place it in a freezer bath to cool to -10 to -20°C and stir at high speed for 30 to 60 minutes to obtain a PPTA solution; Step a3: Centrifuge the PPTA solution for 30-90 minutes to degas it and obtain the spinning solution. Then, using water as a coagulation bath, use a micro-injection pump to squeeze the centrifuged spinning solution into the coagulation bath to obtain wet fibers. Step a4: Place the wet fiber into a beaker containing deionized water and stir to clean it. Then, use a vacuum filter to filter and dry the cleaned fiber. Repeat the above steps several times. Place the filtered fiber in a refrigerator to cool for 3-6 hours, and then use a freeze dryer to dry the cooled fiber for 24-48 hours to obtain poly(p-phenylene terephthalamide) fiber.

7. The preparation method of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 6, characterized in that, The solvent is at least one of water and ethanol.

8. The preparation method of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 7, characterized in that, The solvent is ethanol, and the total weight ratio of N-methylpyrrolidone and calcium chloride to ethanol is 1:

10.

9. The preparation method of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 7, characterized in that, The solvent is water, and the total weight ratio of N-methylpyrrolidone and calcium chloride to water is 1:

15.

10. The preparation method of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing according to claim 7, characterized in that: The solvent is a mixture of water and ethanol, and the total weight ratio of N-methylpyrrolidone and calcium chloride to the weight ratio of water and ethanol is 1:10:

10.

11. A cementing slurry, characterized in that, It is made from the following raw materials in parts by weight: 1-3 parts of a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing as described in any one of claims 1-4, 100-120 parts of cement, 35-45 parts of quartz sand, 2-4 parts of anti-high-temperature degradation agent, 1-3 parts of retarder, 2-4 parts of suspension stabilizer, 2-4 parts of fluid loss reducing agent, and 44-48 parts of clean water.

12. The cementing slurry according to claim 11, characterized in that, The quartz sand is composed of 200-mesh acid-washed quartz sand and 400-mesh acid-washed quartz sand, and the mass ratio of 200-mesh acid-washed quartz sand to 400-mesh acid-washed quartz sand is 2:

1.

13. The cementing slurry according to claim 11, characterized in that, Configure it as follows, including the following steps: Step c1: Dry mix cement, quartz sand and a high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing to obtain a mixed dry material; Step c2: Dissolve the anti-high temperature degradation agent, retarder, suspension stabilizer and water loss reducer in water and stir evenly to obtain a mixed wet material; Step c3: Add the dry mixture from step c1 to the wet mixture obtained in step c2 and stir evenly to obtain a cementing slurry containing high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent for cementing cement stone.

14. The cementing slurry according to claim 13, characterized in that, In step c3, the stirring process is first rotated at a low speed (4000±200r / min), and the weighed dry powder mixture is added within 10 to 20 seconds. Then the lid of the stirrer is closed, and stirring is continued at a high speed (12000±500r / min) for 35 to 40 seconds to obtain a cementing slurry containing high-temperature resistant modified poly(p-phenylene terephthalamide) fiber toughening agent.

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