Degradable temperature-controlled delayed water absorption expansion plugging agent as well as preparation method and application thereof

Abstract

The invention discloses a degradable temperature-controlled delayed water absorption expansion plugging agent and a preparation method thereof, and belongs to the technical field of drilling plugging in the petroleum industry. Raw materials for preparing effective components of the plugging agent comprise hydroxyethyl acrylate, acrylamide, starch, bentonite, a cross-linking agent, an initiator and a rigid inert material. Wherein the rigid inert material is subjected to surface modification by adopting an aluminate coupling agent, so that the crosslinking mechanical property between the rigid material and polymer molecules is greatly improved. The raw materials are uniformly mixed and then subjected to a cross-linking reaction to prepare an elastic gel which is the degradable temperature-controlled delayed water absorption expansion plugging agent. The problems that a plugging agent is too high in water absorption expansion speed, has no delay characteristic, is low in compressive strength and cannot be degraded are solved, and the plugging agent is suitable for plugging operation of permeable leakage, fractured leakage, cave type leakage and the like.

Description

Technical Field

[0001] This invention belongs to the field of drilling and plugging technology in the petroleum industry, and relates to a temperature-controlled delayed water absorption and expansion plugging agent, specifically a biodegradable temperature-controlled delayed water absorption and expansion plugging agent, its preparation method, and its application. Background Technology

[0002] Drilling fluids play a crucial role in geological drilling and oil well drilling operations. However, in abnormal formations characterized by permeability and fractures, if drilling fluid leaks into the formation under pressure differentials, it can pose significant safety risks and economic losses to drilling operations. Therefore, plugging agents, as materials for effectively sealing formation leakage channels, have become one of the key factors affecting the effectiveness of plugging operations.

[0003] Currently, rapidly absorbing and expanding materials are commonly used as plugging agents. For example, Chinese invention patent CN104726078A uses sodium polyacrylate, cotton fibers, and polyacrylamide as its main components. These materials absorb water and quickly clump together, expanding extremely rapidly—tens of times within an hour, with a maximum expansion of hundreds of times. However, this rapid expansion also causes inconvenience in construction operations. In on-site plugging operations, preparing the plugging slurry and pumping it into the formation takes time. If expansion occurs before reaching the target leak layer, precise sealing at the target location becomes impossible, leading to plugging failure. Furthermore, excessively rapid expansion can cause pipeline blockage, hindering pumping operations. Also, the compressive strength of water-absorbing and expanding materials often decreases significantly with volume expansion, creating a risk of re-leakage in later drilling operations and compromising construction safety.

[0004] Regarding the principle of leakage sealing, existing technologies mostly employ a bridging process using multi-graded granular materials. Larger particles act as bridges in the leakage channels, while smaller particles fill the gaps to form a sealing layer. However, in actual construction, downhole leakage channels are diverse and complex, making it impossible to accurately grasp the formation's leakage channels. Therefore, the selection of particle size for the sealing material, as well as the comprehensive consideration of particle size distribution and concentration ratio at each level, is quite complex. If the particle size is too large, the sealing material cannot smoothly enter the leaking layer, creating a "sealing" effect. Conversely, if the particles are too small, the sealing material leaks directly. Therefore, this principle-based sealing method may fail to achieve effective sealing if the concentration ratio of each particle level is inappropriate.

[0005] In addition to the materials mentioned above, some gel-based materials can also be used as sealants, but they are difficult to degrade by microorganisms and have the problem of not being able to decompose for a long time, which may cause soil pollution and water pollution. Summary of the Invention

[0006] To address the problems of excessively rapid water absorption and expansion without delay in existing technologies, as well as low compressive strength and non-degradability, this invention aims to provide a biodegradable, temperature-controlled, delayed water absorption and expansion plugging agent. Through modification of rigid inert materials and graft crosslinking reactions, a plugging agent with a suitable expansion rate is obtained. This agent does not expand or has an extremely low expansion rate in a normal water environment, but only absorbs water and expands under the influence of formation temperature to form a high-strength, temperature-resistant, and biodegradable plugging material.

[0007] Another objective of this invention is to provide a method for preparing and applying the above-mentioned biodegradable temperature-controlled delayed water absorption and expansion sealant.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A biodegradable, temperature-controlled, delayed-absorption, swelling, and sealing agent, the raw materials for which its active ingredient is made, by weight, include 8-18 parts of hydroxyethyl acrylate, 2-12 parts of acrylamide, 0.5-8 parts of starch, 1-9 parts of bentonite, 0.01-0.4 parts of crosslinking agent, 0.01-0.2 parts of initiator, and 0-8 parts of rigid inert material;

[0010] The rigid inert material includes at least one of mica, nut shells, vermiculite, nano-silica, nano-cellulose, and ultrafine calcium carbonate. All of these rigid inert materials are biodegradable or environmentally friendly.

[0011] Furthermore, the raw materials, by weight, include 12-16 parts of hydroxyethyl acrylate, 6-10 parts of acrylamide, 1-2 parts of starch, 6-8 parts of bentonite, 0.05-0.2 parts of crosslinking agent, and 0.02-0.1 parts of initiator.

[0012] As a limitation of the present invention, the rigid inert material is a modified rigid inert material, obtained by surface modification with an aluminate coupling agent at a mass fraction of 0.5%-2%. That is, during surface modification, the mass ratio of the aluminate coupling agent to the rigid inert material to be modified is 0.5-2:100.

[0013] As a further limitation of the present invention, the rigid inert material is granular with a mesh size ≤ 60 mesh.

[0014] Furthermore, the mesh size of mica, nut shells, and vermiculite in the rigid inert material is 10 to 60 mesh.

[0015] As a further limitation of the present invention, the crosslinking agent is N,N-methylenebisacrylamide or a mixture of N,N-methylenebisacrylamide and triallylamine in a mass ratio of 4 to 6:1.

[0016] As a further limitation of the present invention, the initiator is a peroxide initiator or a redox system initiator.

[0017] As a further limitation of the present invention, the redox system initiator is composed of persulfate and sodium bisulfite in a mass ratio of 1:1 to 2.

[0018] Furthermore, the persulfate is ammonium persulfate or potassium persulfate.

[0019] As a limitation of the present invention, the raw materials also include 30 to 60 parts of water.

[0020] This invention also provides a method for preparing a biodegradable, temperature-controlled, delayed-expansion sealing agent, comprising the following steps performed sequentially:

[0021] Weigh the raw materials according to the stated weight proportions, mix them well, add the initiator at a reaction temperature of 55℃~70℃, mix well, and undergo a cross-linking reaction to obtain an elastic gel. After drying, a biodegradable temperature-controlled delayed water absorption and swelling sealant is obtained.

[0022] Furthermore, mixing can be achieved by stirring for 20 to 60 minutes, while controlling the temperature during stirring to not exceed the reaction temperature.

[0023] As a limitation of the present invention, the reaction time of the crosslinking reaction is 120 min to 240 min;

[0024] The biodegradable, temperature-controlled, delayed-absorption, swelling sealant is pulverized into granules.

[0025] Furthermore, it can be made into particles of different sizes, which has good adaptability and a good sealing effect on leakage channels of different sizes.

[0026] The present invention also provides an application of a biodegradable, temperature-controlled, delayed-expansion, leak-sealing agent, specifically for use in adding to drilling slurry at a mass fraction of 2% to 8% to seal leaks.

[0027] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0028] (1) The present invention provides a biodegradable temperature-controlled delayed water absorption and swelling sealant, which uses starch as the main graft skeleton and obtains water absorption and swelling material by graft copolymerization of hydroxyethyl acrylate, acrylamide, bentonite and rigid inert material through crosslinking agent and initiator. In particular, when the modified rigid inert material is obtained by surface modification with aluminate coupling agent, the bentonite and the modified rigid inert material serve as fillers to provide structural support. On the other hand, the modified rigid inert material is effectively combined with the molecular structure of the crosslinking product through intermolecular forces under the action of the crosslinking agent, and the resulting gel has good elasticity and higher strength.

[0029] (2) The present invention provides a biodegradable temperature-controlled delayed water absorption and expansion plugging agent with good compressive strength. It has low water absorption and expansion at normal temperature and pressure, and high water absorption rate in high temperature and weakly alkaline water environment. The expansion can reach 19.47 times. It is adaptable to various leakage channels, has high compressive strength, and the pressure resistance test is not less than 5MPa. In addition, since the raw materials are easy to make into particles of different sizes, it has better adaptability and has a good sealing effect on leakage channels of different sizes. It can enter the leakage channel with a small volume and stay in the leakage channel. It can absorb water and expand in the water environment, and it is not restricted by the shape of the channel. The expansion body has viscoelastic properties, which allows it to adhere well to the wall of the leakage channel. It has a certain expansion pressure. In addition, due to the mechanical strength, the interaction and compression between the particles gradually reduce the leakage pressure difference and gradually form a particle cluster, which forms a pressure-bearing sealing layer. In addition, this plugging agent has good temperature resistance. Thermogravimetric analysis shows that the molecules remain stable and do not decompose at 201℃, making it suitable for the high temperature and high pressure environment of the lost formation and achieving significant plugging effect.

[0030] (3) The present invention provides a method for preparing a biodegradable, temperature-controlled, delayed water absorption and expansion sealant. The process is simple and the cost is low. Among the raw materials selected, starch and nut shells can be naturally degraded. Bentonite, mica, vermiculite, silica, and ultrafine calcium carbonate are also environmentally friendly materials that do not require recycling. The starch, bentonite, and rigid materials selected as raw materials for the synthesis of this sealant are all common commercially available products, effectively reducing production costs.

[0031] In summary, this invention is applicable to the industrial production and application of a biodegradable, temperature-controlled, delayed-expansion sealing agent, suitable for sealing leaks such as permeable leaks, crack leaks, and cavern leaks. Attached Figure Description

[0032] Figure 1 The infrared spectrum of product 4# obtained in Example 4 of this invention;

[0033] Figure 2 The stress-strain curves of the products obtained in Examples 4 and 6 of the present invention after water absorption and expansion are shown in the performance test experiments of the present invention.

[0034] Figure 3 This is a graph showing the water absorption mass ratio of the product obtained in Example 4 of the performance test experiment of this invention;

[0035] Figure 4 This is a thermogravimetric analysis diagram of the product obtained in Example 4 of the performance test experiment of the present invention. Detailed Implementation

[0036] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustrative and understanding purposes only and are not intended to limit the scope of the invention.

[0037] Example 1

[0038] This embodiment describes a biodegradable, temperature-controlled, delayed-expansion sealing agent and its preparation method. The raw materials for the effective components of this sealing agent are: 15g hydroxyethyl acrylate, 6g acrylamide, 1.5g starch, 4g bentonite, 0.1g N,N-methylenebisacrylamide (crosslinking agent), 0.02g initiator composed of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, 2g 40-mesh mica powder for preparing modified rigid inert materials, and 40mL distilled water.

[0039] A biodegradable, temperature-controlled, delayed-expansion sealing agent was prepared using the above-mentioned raw materials. The specific preparation method is as follows:

[0040] I) Preparation of modified rigid inert material: Take the above mica powder and add aluminate coupling agent (1% by mass) at a mass ratio of 1:100 with the mica powder to be modified, and perform surface modification to obtain modified rigid inert material.

[0041] II) The above-mentioned hydroxyethyl acrylate, acrylamide, starch, bentonite, crosslinking agent, and modified rigid inert material are stirred and mixed thoroughly. The system temperature is gradually increased to a reaction temperature of 65°C. At this point, 5 mL of a mixed solution of ammonium persulfate and sodium bisulfite initiator is slowly added dropwise. Stirring is continued for 45 min, then stirring is stopped. The system temperature is maintained at 65°C, and the static reaction is allowed to proceed for 180 min to complete crosslinking and generate an elastic gel. This gel is then removed, cut into small pieces, air-dried at 80°C, and pulverized into granules to obtain a biodegradable, temperature-controlled, delayed-expansion sealing agent, designated as Product 1#. This product appears as light brown solid granules.

[0042] Example 2

[0043] This embodiment describes a biodegradable, temperature-controlled, delayed-expansion sealing agent and its preparation method. The raw materials for the effective components of this sealing agent are: 15g hydroxyethyl acrylate, 6g acrylamide, 3g starch, 4g bentonite, 0.1g N,N-methylenebisacrylamide (crosslinking agent), 0.02g initiator composed of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, 2g ultrafine calcium carbonate for preparing modified rigid inert materials, and 40mL distilled water.

[0044] A biodegradable, temperature-controlled, delayed-expansion sealing agent was prepared using the above-mentioned raw materials. The specific preparation method is as follows:

[0045] I) Preparation of modified rigid inert material: Take the above-mentioned ultrafine calcium carbonate, add aluminate coupling agent (mass fraction of 1%) at a mass ratio of 1:100 with the ultrafine calcium carbonate to be modified, and carry out surface modification to obtain modified rigid inert material.

[0046] II) The above-mentioned hydroxyethyl acrylate, acrylamide, starch, bentonite, crosslinking agent, and modified rigid inert material are stirred and mixed thoroughly. The system temperature is gradually increased to a reaction temperature of 65°C. At this point, 5 mL of a mixed solution of ammonium persulfate and sodium bisulfite initiator is slowly added dropwise. Stirring is continued for 45 min, then stirring is stopped. The system temperature is maintained at 65°C, and the static reaction is allowed to proceed for 180 min to complete crosslinking and generate an elastic gel. This gel is then removed, cut into small pieces, air-dried at 80°C, and pulverized into granules to obtain a biodegradable, temperature-controlled, delayed-expansion sealing agent, designated as Product 2#. This product appears as light brown solid granules.

[0047] Example 3

[0048] This embodiment describes a biodegradable, temperature-controlled, delayed-expansion sealing agent and its preparation method. The raw materials for the effective components of this sealing agent are: 15g hydroxyethyl acrylate, 9g acrylamide, 3g starch, 4g bentonite, 0.1g N,N-methylenebisacrylamide (crosslinking agent), 0.02g initiator composed of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, 2g 20-mesh nut shells for preparing modified rigid inert materials, and 40mL distilled water.

[0049] A biodegradable, temperature-controlled, delayed-expansion sealing agent was prepared using the above-mentioned raw materials. The specific preparation method is as follows:

[0050] I) Preparation of modified rigid inert material: Take the above 20 mesh nut shells, add aluminate coupling agent (mass fraction of 1%) at a mass ratio of 1:100 with the 20 mesh nut shells to be modified, and carry out surface modification to obtain modified rigid inert material.

[0051] II) The above-mentioned hydroxyethyl acrylate, acrylamide, starch, bentonite, crosslinking agent, and modified rigid inert material are stirred and mixed thoroughly. The system temperature is gradually increased to a reaction temperature of 65°C. At this point, 5 mL of a mixed solution of ammonium persulfate and sodium bisulfite initiator is slowly added dropwise. Stirring is continued for 45 min, then stirring is stopped. The system temperature is maintained at 65°C, and the static reaction is allowed to proceed for 180 min to complete crosslinking and generate an elastic gel. This gel is then removed, cut into small pieces, air-dried at 80°C, and pulverized into granules to obtain a biodegradable, temperature-controlled, delayed-expansion sealing agent, designated as Product 3#. This product appears as light brown solid granules.

[0052] Example 4

[0053] This embodiment describes a biodegradable, temperature-controlled, delayed-expansion sealing agent and its preparation method. The raw materials for the effective components of this sealing agent are: 15g hydroxyethyl acrylate, 9g acrylamide, 3g starch, 8g bentonite, 0.1g N,N-methylenebisacrylamide (crosslinking agent), 0.02g initiator composed of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, 2g 40-mesh vermiculite for preparing modified rigid inert materials, and 40mL distilled water.

[0054] A biodegradable, temperature-controlled, delayed-expansion sealing agent was prepared using the above-mentioned raw materials. The specific preparation method is as follows:

[0055] I) Preparation of modified rigid inert material: Take the above 40 mesh vermiculite, add aluminate coupling agent (mass fraction of 1%) at a mass ratio of 1:100 with the 40 mesh vermiculite to be modified, and perform surface modification to obtain modified rigid inert material;

[0056] II) The above-mentioned hydroxyethyl acrylate, acrylamide, starch, bentonite, crosslinking agent, and modified rigid inert material were stirred and mixed thoroughly. The system temperature was gradually increased to 65°C. At this point, 5 mL of a mixed solution of ammonium persulfate and sodium bisulfite initiator was slowly added dropwise. Stirring was continued for 45 min, then stirring was stopped. The system temperature was maintained at 65°C, and the static reaction was allowed to proceed for 180 min to complete the crosslinking and generate an elastic gel. This gel was then removed, cut into small pieces, air-dried at 80°C, and pulverized into granules to obtain a biodegradable, temperature-controlled, delayed-expansion sealing agent, designated as Product 4#. This product appears as yellowish-brown solid granules.

[0057] Product #4 was characterized by infrared spectroscopy, and the results are as follows: Figure 1 As shown in the figure, at 1657cm -1 A characteristic absorption peak for C═O groups with amide groups appears nearby, at 3432 cm⁻¹. -1 The presence of a characteristic N-H absorption peak for amide groups nearby indicates the presence of amide groups in product #4; simultaneously, the C-N (1425cm) absorption peak is also present. -1The stretching vibration peak of the N,N′-methylenebisacrylamide bond indicates that it is linked to the molecule and plays a cross-linking role; 1735 cm⁻¹ -1 The presence of C═O absorption peaks near the ester group indicates the presence of ester groups in product #4; the C—C(═O)—O (1210 cm⁻¹) absorption peaks on the starch ring... -1 ) and C—O—C (1136cm -1 The absorption peaks indicate the success of starch grafting. Therefore, infrared spectroscopy characterization confirms that the polymer synthesized by the method of this invention is the target product.

[0058] Example 5

[0059] This embodiment describes a biodegradable, temperature-controlled, delayed-expansion sealing agent and its preparation method. The raw materials for the effective components of the sealing agent are: 15g hydroxyethyl acrylate, 9g acrylamide, 1g starch, 8g bentonite, 0.1g N,N-methylenebisacrylamide (crosslinking agent), 0.02g initiator composed of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, 2g nano-silica for preparing modified rigid inert materials, and 40mL distilled water.

[0060] A biodegradable, temperature-controlled, delayed-expansion sealing agent was prepared using the above-mentioned raw materials. The specific preparation method is as follows:

[0061] I) Preparation of modified rigid inert material: Take the above-mentioned nano silica and add aluminate coupling agent (1% by mass) at a mass ratio of 1:100 with the nano silica to be modified, and perform surface modification to obtain modified rigid inert material.

[0062] II) The above-mentioned hydroxyethyl acrylate, acrylamide, starch, bentonite, crosslinking agent, and modified rigid inert material are stirred and mixed thoroughly. The system temperature is gradually increased to a reaction temperature of 65°C. At this point, 5 mL of a mixed solution of ammonium persulfate and sodium bisulfite initiator is slowly added dropwise. Stirring is continued for 45 min, then stirring is stopped. The system temperature is maintained at 65°C, and the static reaction is allowed to proceed for 180 min to complete crosslinking and generate an elastic gel. This gel is then removed, cut into small pieces, air-dried at 80°C, and pulverized into granules to obtain a biodegradable, temperature-controlled, delayed-expansion sealing agent, designated as Product 5#. This product appears as yellowish-brown solid granules.

[0063] By increasing the amount of raw materials by 100 times according to the above embodiments, a biodegradable temperature-controlled delayed water absorption and expansion sealing agent product 1# to product 5# was prepared for performance testing.

[0064] Infrared spectral characterization was performed on random samples of products 1#, 2#, 3#, and 5#, and all samples yielded [results]. Figure 1 Similar results indicate that the target polymer was successfully synthesized in both cases.

[0065] Example 6

[0066] This embodiment describes a biodegradable, temperature-controlled, delayed-expansion sealing agent and its preparation method. The difference from Example 4 is that the rigid, inert material vermiculite was not surface-modified using an aluminate coupling agent. The specific details are as follows:

[0067] The raw materials for the effective components of this sealant are: 15g hydroxyethyl acrylate, 9g acrylamide, 3g starch, 8g bentonite, 0.1g N,N-methylenebisacrylamide (crosslinking agent), 0.02g initiator composed of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, 2g vermiculite, and 40mL distilled water.

[0068] A biodegradable, temperature-controlled, delayed-expansion sealing agent was prepared using the above-mentioned raw materials. The specific preparation method is as follows:

[0069] The above-mentioned hydroxyethyl acrylate, acrylamide, starch, bentonite, crosslinking agent, and rigid inert material vermiculite were stirred and mixed thoroughly. The system temperature was gradually increased to a reaction temperature of 65°C. At this point, 5 mL of a mixed solution of ammonium persulfate and sodium bisulfite initiator was slowly added dropwise. Stirring was continued for 45 min, then stirring was stopped. The system temperature was maintained at 65°C, and the static reaction was allowed to proceed for 180 min to complete crosslinking and generate an elastic gel. This gel was then removed, cut into small pieces, air-dried at 80°C, and pulverized into granules to obtain a biodegradable, temperature-controlled, delayed-expansion sealing agent, designated as Product 6#. This product appears as yellowish-brown solid granules.

[0070] Comparative Example

[0071] This comparative example is a composite bridging and sealing agent, denoted as Composite Bridging and Sealing Agent 0#. The raw materials for its effective components are 2000-mesh ultrafine calcium carbonate, 20-mesh mica, and fruit shells with a particle size of 1-3 mm and 3-5 mm, in a weight ratio of 2:5:3:2.

[0072] Performance testing experiment

[0073] (I) Compression Deformation Performance Testing

[0074] The compression deformation properties of biodegradable temperature-controlled delayed water absorption and expansion sealant products 4# and 6# prepared in Examples 4 and 6 respectively were tested, as follows:

[0075] Equal amounts of product #4 and product #6 were placed in water with a pH of 10 and kept at a constant temperature of 85℃ to allow them to absorb water and swell. After 24 hours, they were removed and made into cubes with a side length of 10 mm. The compressive deformation properties of the two products were tested using an electronic universal testing machine with a loading rate of 15 mm / min. The stress-strain curves after water absorption and swelling were obtained, and the results are as follows. Figure 2 .

[0076] Depend on Figure 2 It can be seen that product #4 exhibits strong compressive strength after water absorption, reaching a maximum compressive strength of 2.14 MPa at a strain of 82.56%, while product #6, without surface modification of the vermiculite, only reaches a maximum compressive strength of 1.60 MPa at a strain of 80.90%. Therefore, surface modification of rigid inert materials using aluminate coupling agents can significantly improve their compressive deformation properties.

[0077] (II) Salt resistance test

[0078] Take seven 10g portions of product #4 (particle size 1.7–4mm) and soak them separately in water, 0.1% calcium chloride solution, 0.5% calcium chloride solution, 5% sodium chloride solution, 10% sodium chloride solution, 0.1% sodium carbonate solution, and 1% sodium carbonate solution. The temperature of all seven liquids is 85℃, and the pH is adjusted to 10. Record the water absorption ratio of the sealant at regular intervals over 24 hours to obtain the water absorption ratio curve. The results are shown below. Figure 3 .

[0079] Figure 3 This indicates that different types of salts and salt solutions of varying concentrations all have a certain impact on the water absorption performance of the sealant product. However, even in environments with high-concentration sodium chloride solution (10% by mass) and calcium chloride solution (0.5% by mass), the biodegradable, temperature-controlled, delayed-expansion sealant product #4 prepared in this invention still absorbs more than 14 times its original weight in 24 hours, demonstrating good water absorption and swelling performance and outstanding salt resistance. The water absorption ratio is relatively low within 3 hours, but the absorption rate accelerates between 3 and 6 hours, further confirming that the hydrophobic ester groups on the internal molecular chains of the gel in this invention hydrolyze into hydrophilic hydroxyl and carboxyl groups, promoting the sealant's water absorption rate and increasing its water absorption potential.

[0080] The biodegradable, temperature-controlled, delayed water absorption and expansion sealant products 1# to 5# prepared in Examples 1 to 5 above were subjected to water absorption and expansion performance tests and sealant effect evaluations.

[0081] (III) Water Absorption and Swelling Performance Test

[0082] Weigh out two portions of each of the sealant products #1 to #5, with equal mass, and record this mass as m0. Set up different water environment test conditions, placing one portion of each product in a water environment and letting it stand for 3 hours, while the other portion stands for 24 hours, allowing it to fully absorb water and reach saturation. After draining the water, weigh the expanded sealant mass m. t Calculate the water absorption ratio Q of the sealant = (m t / m0)-1, unit g / g.

[0083] The test conditions and results are shown in Table 1.

[0084] Table 1. Test conditions and results for water absorption and swelling performance.

[0085]

[0086] As shown in Table 1, the biodegradable, temperature-controlled delayed water absorption and expansion sealant of this invention exhibits low water absorption rate in a water environment with pH=7 and 30℃, with a minimum water absorption rate of 0.19 times after 3 hours; the water absorption rate remains low even in a water environment with pH=10 and 30℃, with a minimum of 0.27 times; the water absorption rate significantly increases with increasing temperature, reaching a maximum of 19.47 times, achieving delayed expansion with temperature changes; this facilitates the pumping and application of the sealant and allows it to smoothly enter the target leak layer.

[0087] (iv) Evaluation of the sealing effect of the plugging agent

[0088] The sealing effect of products 1# to 5# and composite bridging plugging agent 0# was tested using a Type 71 high-temperature and high-pressure fluid loss meter. During the test, drilling slurry was added to each of the six product groups according to different formulations to prepare a plugging slurry with a pH of 10. The specific formulations are as follows:

[0089] Formula 0#: 95% drilling base slurry by mass + 5% composite bridging and plugging agent by mass;

[0090] Formula 1#: Drilling base slurry comprising 95% by mass + Product 1# comprising 5% by mass;

[0091] Formula 2#: 95% drilling base slurry by mass + 5% product 2# by mass;

[0092] Formula 3#: 95% drilling base slurry by mass + 5% product 3# by mass;

[0093] Formula 4#: 95% drilling base slurry by mass + 5% product 4# by mass;

[0094] Formula 5#: Drilling base slurry with a mass fraction of 95% + Product 5# with a mass fraction of 5%.

[0095] Six portions (150g each) of quartz sand with mesh sizes of 10-20, 20-40, and 40-60 were spread evenly at the bottom of the mud cup of a high-temperature, high-pressure (HTHP) fluid loss tester to simulate formation porosity and fractures, thus testing the sealing effect of plugging agents formulated 0# to 5#. Three 300mL portions of each formula were taken and poured into the HTHP mud cups, the cups were capped, and placed in the HTHP base. The pressure was increased to 5MPa using nitrogen, and the fluid loss over 240 minutes was recorded to evaluate the sealing performance of the plugging agent. If the pressure did not drop during the test, it indicated that the plugging material could withstand the nitrogen pressure and form an effective sealing layer.

[0096] The corresponding quartz sand mesh size and test results for each group are shown in Table 2.

[0097] Table 2. Test conditions and results of the sealing effect of the plugging agent.

[0098]

[0099]

[0100] As shown in Table 2, the raw materials used to make the effective components in composite bridging sealant #0 are all unmodified rigid inert particles, which cannot achieve significant volume expansion in an aqueous environment and therefore cannot achieve sealing. All three experiments resulted in complete leakage, and the product could not withstand a pressure of 5 MPa. In contrast, the experimental samples prepared using formulations #1 to #5 of Examples 1 to 5 of this invention all achieved sealing, with a pressure resistance of not less than 5 MPa, and under experimental conditions, the product of this invention could withstand temperatures not lower than 165℃.

[0101] (V) Thermogravimetric Analysis Experiment

[0102] Further thermogravimetric analysis was performed on product #4, and the results are as follows: Figure 4 In the figure, TG refers to "thermogravimetric loss," representing the curve of sample mass change with temperature during heating; while TDG refers to "thermodynamic weight loss," representing the curve of sample mass change rate. The results show that before 201℃, free water molecules escape from the material of product #4, resulting in a slow decrease in mass, and no significant thermal degradation of the polymer molecular chain occurs. This indicates that the polymer in the product of this invention has good thermal stability under high-temperature conditions; at 201℃, its functional groups will not undergo thermal decomposition and become ineffective. This demonstrates that the biodegradable, temperature-controlled, delayed-expansion sealing agent prepared by the method of this invention has good high-temperature resistance and is suitable for high-temperature conditions.

[0103] The above performance tests were performed on products obtained from other embodiments besides product #4, and similar results were obtained.

[0104] Example 7

[0105] This embodiment is a biodegradable, temperature-controlled, delayed water absorption and expansion sealant and its preparation method. It is basically the same as that in Example 1, except that the rigid inert material in the raw material is nanocellulose, which is surface-modified with an aluminate coupling agent with a mass fraction of 0.5%, and the crosslinking agent used is N,N-methylenebisacrylamide. The reaction temperature is 55°C, the initiator is a peroxide initiator, and the reaction time is 120 min.

[0106] The raw materials used to make the effective components of this sealant include: 8g of hydroxyethyl acrylate, 12g of acrylamide, 0.5g of starch, 5g of bentonite, 0.01g of crosslinking agent, 0.01g of initiator, 2g of rigid inert material for modification, and 30mL of distilled water.

[0107] Example 8

[0108] This embodiment is a biodegradable, temperature-controlled, delayed water absorption and expansion sealant and its preparation method. It is basically the same as Example 1, except that the rigid inert material in the raw material is 60-mesh nut shell particles, which are surface-modified with 1.5% by mass of aluminate coupling agent. The crosslinking agent used is a mixture of N,N-methylenebisacrylamide and triallylamine in a mass ratio of 5:1. The reaction temperature is 60°C, the initiator is composed of potassium persulfate and sodium bisulfite in a mass ratio of 1:1.5, and the reaction time is 240 min.

[0109] The raw materials used to make the effective components of this sealant include: 9g of hydroxyethyl acrylate, 4g of acrylamide, 3g of starch, 1g of bentonite, 0.4g of crosslinking agent, 0.2g of initiator, 8g of rigid inert material for modification, and 50mL of distilled water.

[0110] Example 9

[0111] This embodiment is a biodegradable, temperature-controlled, delayed water absorption and expansion sealant and its preparation method. It is basically the same as Example 1, except that the rigid inert material in the raw materials is a mixture of equal amounts of nut shell particles with a mesh size of 60 and vermiculite. It is used after surface modification with an aluminate coupling agent with a mass fraction of 1%. The crosslinking agent used is a mixture of N,N-methylenebisacrylamide and triallylamine with a mass ratio of 6:1. The reaction temperature is 63°C. The initiator is composed of ammonium persulfate and sodium bisulfite with a mass ratio of 1:2. The reaction time is 220 min.

[0112] The raw materials used to make the effective components of this sealant include: 15g of hydroxyethyl acrylate, 2g of acrylamide, 8g of starch, 3g of bentonite, 0.3g of crosslinking agent, 0.18g of initiator, 4g of rigid inert material for modification, and 40mL of distilled water.

[0113] Example 10

[0114] This embodiment is a biodegradable, temperature-controlled, delayed water absorption and expansion sealant and its preparation method. It is basically the same as Example 1, except that the rigid inert material in the raw materials is a mixture of nano-silica, nano-cellulose, equal amounts of mica particles with a mesh size of 60 mesh, and vermiculite. It is used after surface modification with an aluminate coupling agent with a mass fraction of 2%. The crosslinking agent used is a mixture of N,N-methylenebisacrylamide and triallylamine with a mass ratio of 4:1. The reaction temperature is 70°C. The initiator is composed of potassium persulfate and sodium bisulfite with a mass ratio of 1:2. The reaction time is 190 min.

[0115] The raw materials used to make the effective components of this sealant include: 18g of hydroxyethyl acrylate, 7g of acrylamide, 1.5g of starch, 9g of bentonite, 0.08g of crosslinking agent, 0.02g of initiator, 5g of rigid inert material for modification, and 60mL of distilled water.

[0116] Example 11

[0117] This embodiment is a biodegradable, temperature-controlled, delayed water absorption and expansion sealant and its preparation method, which is basically the same as that in Example 1, except that no rigid inert material is added to the raw materials.

[0118] The biodegradable, temperature-controlled, delayed water absorption and expansion plugging agents prepared in the above embodiments all exhibit good compressive strength after testing. They show low water absorption and expansion at normal temperature and pressure, but higher water absorption in high-temperature, weakly alkaline water environments. They are adaptable to various leakage channels, possess high compressive strength, and withstand pressure of no less than 5 MPa in pressure sealing tests. They also demonstrate good temperature resistance, making them suitable for high-temperature and high-pressure environments in leaky formations, resulting in significant plugging effects. Among these, the plugging agent prepared in Example 11 has relatively weaker compressive strength, but still possesses practical compressive strength suitable for practical applications.

[0119] Examples 12 to 16

[0120] Examples 12 to 16 describe the application of a biodegradable, temperature-controlled, delayed-expansion, water-absorbing plugging agent. The plugging agents prepared in Examples 1 to 5 are added to the drilling slurry at a mass fraction of 2%, 3%, 4%, 5%, or 8% to plug leaks.

[0121] In other embodiments, the plugging agent prepared in Examples 6 to 10 is used to be added to the drilling slurry at a mass fraction of 2%, 5%, 6%, 7.5% or 8% to plug leaks.

[0122] Verification has shown that the above applications have achieved good plugging results in the plugging of seepage leakage, crack leakage, and cavernous leakage.

[0123] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biodegradable, temperature-controlled, delayed-expansion, leak-sealing agent, characterized in that: The raw materials used to make its active ingredient, by weight, include 8-18 parts of hydroxyethyl acrylate, 2-12 parts of acrylamide, 0.5-8 parts of starch, 1-9 parts of bentonite, 0.01-0.4 parts of crosslinking agent, 0.01-0.2 parts of initiator, and 0-8 parts of rigid inert material; Among them, the rigid inert material includes at least one of mica, nut shell, vermiculite, nano silica, nano cellulose and ultrafine calcium carbonate.

2. The biodegradable, temperature-controlled, delayed water absorption and expansion sealant according to claim 1, characterized in that: The rigid inert material is a modified rigid inert material, obtained by surface modification with an aluminate coupling agent at a mass fraction of 0.5% to 2%.

3. The biodegradable, temperature-controlled, delayed-expansion sealing agent according to claim 2, characterized in that: The rigid inert material is in the form of particles with a mesh size ≤ 60 mesh.

4. The biodegradable, temperature-controlled, delayed-expansion sealing agent according to claim 3, characterized in that: The crosslinking agent is N,N-methylenebisacrylamide or a mixture of N,N-methylenebisacrylamide and triallylamine in a mass ratio of 4 to 6:

1.

5. The biodegradable, temperature-controlled, delayed-expansion sealing agent according to claim 4, characterized in that: The redox system initiator is composed of persulfate and sodium bisulfite in a mass ratio of 1:1 to 2.

6. A biodegradable, temperature-controlled, delayed-expansion sealant according to any one of claims 2 to 5, characterized in that: The raw materials also include 30 to 60 parts of water.

7. A method for preparing a biodegradable, temperature-controlled, delayed-expansion sealing agent as described in claim 6, characterized in that, Includes the following steps: Weigh the raw materials according to the stated weight proportions, mix them well, add the initiator at a reaction temperature of 55℃~70℃, mix well, and proceed with the cross-linking reaction until an elastic gel is obtained. After drying, a biodegradable temperature-controlled delayed water absorption and expansion sealing agent is obtained.

8. The method for preparing a biodegradable, temperature-controlled, delayed-expansion sealing agent according to claim 7, characterized in that: The reaction time for the crosslinking reaction is 120 min to 240 min; The biodegradable, temperature-controlled, delayed-absorption, swelling sealant is pulverized into granules.

9. The application of a biodegradable, temperature-controlled, delayed-expansion sealant according to any one of claims 1 to 6, characterized in that: The aforementioned biodegradable, temperature-controlled, delayed-expansion, and leak-sealing agent is used to be added to drilling slurry at a mass fraction of 2% to 8% to seal leaks.

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