Horizontal well high flexibility epoxy resin water shutoff agent and preparation method

Abstract

The application discloses a high-flexibility epoxy resin water shutoff agent for horizontal wells and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing and stirring epoxy resin, amine curing agent, active diluent and imidazole toughening agent in a mass ratio of 100:42-52:13-30:0.5-2.5, heating to obtain a resin plugging agent; performing vacuum defoaming treatment on the resin plugging agent; and performing a heating curing reaction on the resin plugging agent after the vacuum defoaming treatment to obtain the high-flexibility epoxy resin water shutoff agent for horizontal wells. Through indoor simulation tests on the water shutoff agent and field tests on oil wells in low-permeability oil reservoirs, the water shutoff agent shows good injectivity and plugging effect. The water shutoff agent has the characteristics of low viscosity, high curing strength, high tensile resistance and high flexibility, and has high salt resistance, temperature resistance and pressure resistance.

Description

Technical Field

[0001] This invention belongs to the field of water shut-off technology in the development of high water-cut oilfields, specifically relating to a highly flexible epoxy resin water shut-off agent for horizontal wells and its preparation method. Background Technology

[0002] With the increasing demand for oilfield resources, most oilfields have entered the later stages of extraction. To further improve recovery rates and reduce production costs, the application of horizontal wells is expanding. However, the application of horizontal wells has also brought about some technical challenges in water shut-off. These include issues such as fractures caused by long-term water injection, cracks in the casing due to formation water corrosion, and water leakage caused by high water cuts from flooding. Compared to directional wells, the unique characteristics of horizontal wells and the water production features of low-permeability reservoirs increase the difficulty of water shut-off technology. How to effectively shut off water in horizontal wells in low-permeability areas and improve recovery rates has gradually become a key focus for the petroleum industry.

[0003] Conventional water shut-off techniques all have various drawbacks, such as short effective periods for mechanical water shut-off, difficulty in tool maintenance, and poor salt resistance; cement plugging agents that are difficult to inject and retain, and uncontrollable thickening time; and gel-based water shut-off agents with insufficient gel strength, easy backflow, and poor temperature resistance and durability. Therefore, the research on novel horizontal well water shut-off technologies is urgently needed, and the development of high-performance water shut-off materials for horizontal wells is of paramount importance. Summary of the Invention

[0004] In response to the high water cut in horizontal wells caused by fractured reservoirs and long-term water injection, this invention aims to provide a highly flexible epoxy resin water shut-off agent and its preparation method for horizontal wells. This method simplifies the process, is easy to operate, ensures operational safety, and increases oil production while reducing water content. Furthermore, the water shut-off agent exhibits high strength, good adhesion, high flexibility, and good temperature and salt resistance after curing.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A highly flexible epoxy resin water shut-off agent for horizontal wells comprises epoxy resin, amine curing agent, reactive diluent, and imidazole toughening agent in a mass ratio of 100:42-52:13-30:0.5-2.5.

[0007] Furthermore, the epoxy resin selected is bisphenol A type epoxy resin E-51.

[0008] Furthermore, the amine curing agent is one or more of ethylenediamine, vinyltriamine, trivinyltetramine, phenolic amine, and polyamide.

[0009] Furthermore, the active diluent is a mixture of neopentyl glycol diglycidyl ether and dodecyl diglycidyl ether.

[0010] Furthermore, the mass ratio of neopentyl glycol diglycidyl ether to dodecyl diglycidyl ether is 3-20:10.

[0011] Furthermore, the mass ratio of neopentyl glycol diglycidyl ether to dodecyl diglycidyl ether is 10:10.

[0012] Furthermore, the imidazole toughening agent is a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole.

[0013] Furthermore, the mass ratio of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole is 1:1-2:0.8-1.4.

[0014] Furthermore, the mass ratio of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole is 1:1.2:1.

[0015] A method for preparing a highly flexible epoxy resin water-plugging agent for horizontal wells as described above includes the following steps:

[0016] 1) After heating, the epoxy resin, amine curing agent, reactive diluent and imidazole toughening agent are mixed and stirred evenly, and then heated to obtain resin plugging agent;

[0017] 2) The resin plugging agent is subjected to vacuum degassing treatment;

[0018] 3) The vacuum degassing treatment is then subjected to a heating and curing reaction to obtain a high-flexibility epoxy resin plugging agent for horizontal wells.

[0019] Furthermore, the vacuum degassing treatment temperature is 49.5-51.5℃, and the vacuum degree is -0.1MPa.

[0020] Furthermore, the temperature for the heating and curing reaction is 49.5-51.5℃, and the time is 48-72h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The high-flexibility epoxy resin water-blocking agent provided by this invention comprises epoxy resin, amine curing agent, reactive diluent, and imidazole toughening agent. The diluent significantly reduces the viscosity of the water-blocking agent, ensuring its transportability. The epoxy groups in the epoxy resin and reactive diluent undergo a ring-opening reaction with the amine groups in the amine curing agent, forming a three-dimensional network structure, further enhancing the mechanical strength of the water-blocking agent. This results in a water-blocking agent with low viscosity, good adhesion, high flexibility, and high strength after curing. It exhibits good injection fluidity, wide applicability, and excellent plugging effect even in high-temperature and high-salt environments. Through indoor water-blocking simulation experiments and field plugging of horizontal wells in low-permeability reservoirs, the high-flexibility epoxy resin water-blocking agent of this invention demonstrates good fluidity and plugging effect. After plugging, the oil well production increases significantly, water cut decreases, and the utilization rate of the oil well is improved, leading to increased economic benefits.

[0023] Furthermore, the high-flexibility epoxy resin water-blocking agent of the present invention selects epoxy resin (E-51) as the base material of the multifunctional epoxy resin water-blocking material. It has high epoxy value, low viscosity, high strength and hardness, and high heat and corrosion resistance. It also has a lot of reactive epoxy groups. Because of these epoxy groups, the epoxy groups of the epoxy resin react with the amine groups of the amine curing agent. The reaction mechanism is as follows: the primary amine of the curing agent can react with the epoxy groups to generate secondary amines and hydroxyl groups. The secondary amine can also react with the epoxy groups to generate tertiary amines. The reaction proceeds in sequence, gradually forming a three-dimensional network structure, thereby having different excellent properties.

[0024] Furthermore, in the high-flexibility epoxy resin plugging agent of the present invention, the selected reactive diluent is a mixture of dodecyl diglycidyl ether (AGE) and neopentyl glycol diglycidyl ether (678). The differences among the selected reactive diluents mainly lie in their chain length and epoxy group equivalents, resulting in different advantages after being added to the epoxy resin plugging agent. Taking diluent 678 as an example, the mechanism by which the reactive diluent participates in the curing reaction of the epoxy resin plugging agent is as follows: the epoxy group and the amine group undergo a ring-opening reaction, thus the chain segment of diluent 678 is successfully linked to the network structure of the plugging agent. By changing the amount of diluent added, the performance of the plugging agent before and after curing can be effectively adjusted.

[0025] Furthermore, the high-flexibility epoxy resin plugging agent of the present invention uses a toughening agent derived from a compound of imidazole toughening agents 2-ethylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole. In the initial stage of the experiment, ester-based and silicone oil-based toughening agents were used as additives for investigation. The results showed that the temperature resistance and tensile shear properties of the plugging agent with these additives could not meet the technical specifications of the plugging agent. Therefore, the present invention selects imidazole toughening agents to further optimize the performance of the epoxy resin plugging agent system. The main reason is that the CN bond on the imidazole ring in the imidazole toughening agent also participates in the curing reaction, which can improve the flexibility of the cured product and further improve the performance of the plugging agent.

[0026] In the preparation process of the high-flexibility epoxy resin plugging agent of this invention, the amount of diluent and toughening agent added has a significant impact on the strength properties of the plugging agent after curing. Therefore, the mass ratio of epoxy resin, amine curing agent, reactive diluent, and imidazole toughening agent is 100:42-52:13-30:0.5-2.5. The compressive strength and tensile shear strength of the cured epoxy resin plugging agent both show a trend of first increasing and then decreasing with the addition of diluent and toughening agent. For the plugging agent system, the diluent participates in the curing reaction, increasing the crosslinking density of the system, and its post-curing compressive strength is also improved. However, the increased C-chains affect the rigid network, so the increase in compressive strength in the later stages is reduced. Imidazole toughening agents can promote the curing reaction and increase the crosslinking density of the plugging agent, but excessive imidazole will lead to an increase in stress concentration points and reduce the strength of the cured product. Therefore, in the preparation process of the plugging agent, the amount of diluent and toughening agent added should be reasonably adjusted to ensure the optimal performance of the plugging agent. Attached Figure Description

[0027] Figure 1 Viscosity curves of epoxy resin blockers modified with diluent 678 and AGE at different temperatures;

[0028] Figure 2 The initial setting time of the system containing diluent 678 and AGE modified epoxy resin plugging agent;

[0029] Figure 3 Density results for diluent 678 and AGE-modified epoxy resin plugging agent;

[0030] Figure 4 The tensile properties of diluent 678 and AGE modified epoxy resin plugging agent are shown in the results.

[0031] Figure 5 The compressive strength results are for diluent 678 and AGE modified epoxy resin plugging agent.

[0032] Figure 6 Figure 1 shows the tensile shear strength results of diluent 678 and AGE modified epoxy resin plugging agent.

[0033] Figure 7 The glass transition temperature of diluent 678 and AGE modified epoxy resin plugging agent;

[0034] Figure 8 Viscosity curves of the toughening agent XF-3 modified F3 system at different temperatures;

[0035] Figure 9 The initial setting time of the toughening agent XF-3 modified F3 system;

[0036] Figure 10The density results of the toughening agent XF-3 modified F3 system at room temperature;

[0037] Figure 11 The tensile properties of the F3 system modified by toughening agent XF-3;

[0038] Figure 12 The compressive strength of the F3 system modified by toughening agent XF-3;

[0039] Figure 13 To improve the shear properties of the F3 system modified by toughening agent XF-3;

[0040] Figure 14 The glass transition temperature of the toughening agent XF-3 modified F3 system;

[0041] Figure 15 The reaction mechanism is as follows: (a) is the reaction system of resin and curing agent; (b) is the reaction system after adding diluent.

[0042] Figure 16 The initial setting time of the XF3 plugging agent system under different pressures;

[0043] Figure 17 Schematic diagram of the water shut-off process for well CLS-01;

[0044] Figure 18 This is the three-dimensional network structure of the water-blocking agent of the present invention. Detailed Implementation

[0045] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0046] The high-flexibility epoxy resin water plugging agent for horizontal wells of the present invention is composed of epoxy resin, amine curing agent, reactive diluent (epoxy ether diluent) and imidazole toughening agent, wherein the mass ratio of epoxy resin, amine curing agent, reactive diluent and imidazole toughening agent is 100:42-52:13-30:0.5-2.5.

[0047] The epoxy resin used is bisphenol A type epoxy resin E-51, with an epoxy value of 0.54 (0.54 mol of epoxy groups per 100g of resin). It has high epoxy value, high strength and hardness, and high heat and corrosion resistance.

[0048] The amine curing agent is one or more of ethylenediamine, vinyltriamine, trivinyltetramine, phenolic amine and polyamide.

[0049] The active diluent is a compounding agent composed of neopentyl glycol diglycidyl ether (678) and dodecyl diglycidyl ether (AGE). The mass ratio of neopentyl glycol diglycidyl ether (678) to dodecyl diglycidyl ether (AGE) is 3-20:10. Preferably, the mass ratio is 10:10.

[0050] The imidazole toughening agent is a mixture of 2-methylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole in a mass ratio of 1:1-2:0.8-1.4. Preferably, the mass ratio is 1:1.2:1.

[0051] The present invention discloses a method for preparing a highly flexible epoxy resin water-plugging agent for horizontal wells, comprising the following steps:

[0052] 1) Cleaning the mold: The stretching mold, compression mold and steel sheet used for shearing were prepared according to national standards. Before preparation, they were cleaned with organic solvent, dried by heating, coated with a layer of release agent (silicone oil), assembled according to the prototype, and heated in an oven at 50.0±0.5℃ for 30 minutes.

[0053] 2) Preparation of the plugging agent: According to the mass ratio of 100:42-52:13-30:0.5-2.5, the heated epoxy resin, amine curing agent, reactive diluent and imidazole toughening agent are mixed and stirred evenly in sequence, and then heated in an oven at 50.0±0.5℃ for 10min. After filtration by vacuum pump, the mixture is put back into the oven and heated for another 10min. This process is repeated three times to obtain the resin plugging agent, which is recorded as the epoxy resin plugging agent system.

[0054] 3) Casting: Pour resin sealant along the inner wall of the mold through the pouring gate, and try to avoid generating air bubbles as much as possible throughout the entire operation.

[0055] 4) Vacuum degassing: Place the membrane containing the plugging agent into the vacuum oven, close the vent valve, open the vacuum valve, and set the temperature to 50.0±0.5℃. Turn on the vacuum pump to start evacuating air. When the vacuum level inside the oven reaches -0.1MPa, close the vacuum valve and perform degassing.

[0056] 5) Heating and curing: The membrane is cured in a vacuum environment at a temperature of 50.0±0.5℃. After being placed in a vacuum oven for 48-72 hours, it is demolded to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

[0057] The application of a highly flexible epoxy resin water-plugging agent for horizontal wells according to the present invention includes the following steps:

[0058] The epoxy resin plugging agent XF3 system was used, and the plugging agent dosage was prepared as follows: epoxy resin (E51), amine curing agent, reactive diluent, and imidazole toughening agent, totaling 4.0 mg / L. 3 .

[0059] First, the product profile test method was selected to perform quantitative and qualitative analysis of the outlet point. The water plugging method was as follows: the pre-slug and post-slug used a polymer solution (the polymer solution was a 0.5% polyacrylamide aqueous solution by mass), and the main slug used an epoxy resin plugging agent XF3 system water plugging agent.

[0060] The pre-treatment section uses a 0.5% polymer solution, the main section uses the water-blocking agent of this invention, and the post-treatment section uses a 0.5% polymer solution. The volume ratio of the polymer solution used in the pre-treatment section, the water-blocking agent used in the main section, and the polymer solution used in the post-treatment section is 0.2:4.0:0.2.

[0061] Subsequently, the viscosity, density, initial setting time, and mechanical properties of the plugging agent system were tested and comprehensively analyzed and evaluated.

[0062] Specifically, one aspect is the optimized design of the high-flexibility epoxy resin plugging agent formulation for horizontal wells.

[0063] 1. Diluent 678 and AGE compounded modified epoxy resin plugging agent

[0064] Diluent 678 and AGE were compounded and added to the epoxy resin plugging agent system; these systems were named the F1-F5 series in the experiment. The plugging agent system containing only epoxy resin and curing agent was named the X0 series. The specific formulations of the plugging agents and the dosages of each reagent are as follows:

[0065] 1) F1 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), diluent 678 and diluent AGE is 100:45:3:10.

[0066] 2) F2 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), diluent 678 and diluent AGE is 100:46:5:10.

[0067] 3) F3 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), diluent 678 and diluent AGE is 100:48:10:10.

[0068] 4) F4 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), diluent 678 and diluent AGE is 100:50:15:10.

[0069] 5) F4 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), diluent 678 and diluent AGE is 100:52:20:10.

[0070] Depend on Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 Analysis shows that the optimal overall performance of the plugging agent is achieved when both diluent 678 and AGE are added at 10% of the epoxy resin mass (F3 system). At this level, the tensile strength is 52.8 MPa, the tensile shear strength is 14.1 MPa, the glass transition temperature is 100.1℃, and the elongation at break is 1.7%, all of which are improved compared to the X0 system, indicating that the addition of the diluent further optimizes the mechanical properties of the plugging agent. However, the tensile shear strength does not fully meet the technical specifications; therefore, subsequent research will use the F3 system as a benchmark for toughening studies.

[0071] 2. Performance Study of Toughening Agent Modified Epoxy Resin Plugging Agent

[0072] Modification experiments were conducted on the F3 plugging agent system using an imidazole toughening agent (a mixture of 2-methylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole in a mass ratio of 1:1.2:1), the system being named as the XF1-XF5 series. The specific formulation of the plugging agent and the dosage of each reagent are as follows:

[0073] 1) Example 1: XF1 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), imidazole toughening agent, diluent 678 and diluent AGE is 100:42:0.5:10:10.

[0074] 2) Example 2: XF2 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), imidazole toughening agent, diluent 678 and diluent AGE is 100:44:1.0:10:10.

[0075] 3) Example 3: XF3 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), imidazole toughening agent, diluent 678 and diluent AGE is 100:46:1.5:10:10.

[0076] 4) Example 4: XF4 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), imidazole toughening agent, diluent 678 and diluent AGE is 100:48:2.0:10:10.

[0077] 5) Example 5: XF5 system: The mass ratio of epoxy resin (E-51), amine curing agent (phenolic amine), imidazole toughening agent, diluent 678 and diluent AGE is 100:50:2.5:10:10.

[0078] The XF system is modified and optimized using a self-made toughening agent, XF-3. Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 and Figure 14 Analysis shows that various properties of the system change with concentration. The density changes relatively little, remaining at 1.10 g / cm³. 3 The initial setting time is 4-5 hours. The mechanical properties, including elongation at break, compressive strength, and tensile shear strength, are significantly improved. Tensile strength also increases, but the increase is small. The glass transition temperature decreases slightly, but all remain above 90℃, maintaining good heat resistance. The best overall performance is achieved when the addition amount is 1.5 wt% (XF3 system). At this point, the compressive strength of the plugging agent is 101.8 MPa at 25℃ and 71.6 MPa at 50℃, the elongation at break is 2.7%, the tensile strength is 55.8 MPa, the tensile shear strength is 17.6 MPa, and the glass transition temperature is 94.3℃. The addition of imidazole toughening agents further improves the flexibility and performance of the plugging agent. All properties of the modified plugging agent meet the expected technical specifications.

[0079] 3. Salt and pressure resistance tests

[0080] 1) Salt resistance

[0081] The composition and concentration of the brine prepared in the experiment were based on the representative brine concentration of the studied block in the Longdong region. A CaCl2-type simulated formation brine with a salinity of 100,000 mg / L was prepared using MgCl2, CaCl2, NaHCO3, Na2SO4, and KCl. To study the salt tolerance of the numerical plugging agent, compression and shear test specimens of the resin plugging agent were soaked in the prepared brine for 3 days, followed by compression tests. The actual composition of the oilfield formation water used in the experiment and the results of the compression strength are shown in Table 1.

[0082] Table 1 Composition and compressibility of formation water in the oilfield

[0083]

[0084] As shown in Table 1, after soaking in salt water, the compressive strength of the plugging agent at room temperature is 99 MPa, and the compressive strength at 50℃ is 70 MPa. Compared with the compressive strength of the plugging agent measured in the XF3 system, the compressive strength decreases slightly regardless of temperature, but the decrease is small. The decreases at 25℃ and 50℃ are 2.7% and 2.2%, respectively, indicating that the XF3 epoxy resin plugging agent system has good salt resistance.

[0085] 2) Pressure resistance

[0086] In the experiment, 300 mL of XF3 system epoxy resin plugging agent was prepared, placed in a pressure chamber, the piston was closed, the pressure chamber was placed in a container with a water bath and then placed on a universal press. The test was conducted at a loading rate of 5 mm / min. The test results are as follows. Figure 16 As shown.

[0087] Depend on Figure 16 It can be seen that for the epoxy resin plugging agent XF3 system, the initial setting time under a certain pressure is slightly shorter than that under normal pressure, but the difference is small. As time increases, the viscosity difference widens, but remains within a reasonable range. Therefore, pressure has a relatively small impact on the initial setting time of the epoxy resin plugging agent, and the plugging agent exhibits excellent pressure resistance.

[0088] II. Application of high-flexibility epoxy resin water plugging agent in horizontal wells.

[0089] 1. Indoor simulation test

[0090] 1) Indoor plugging test model for plugging agent

[0091] A simulation device was built in the laboratory, referencing the downhole tubing structure of horizontal wells.

[0092] A bottom plug was installed at the lower part of the section where leakage needed to be sealed. Ceramsite with a particle size of 2.56 mm was filled at the toe of the simulated horizontal section where water was exiting the perforation. The porosity of the ceramsite at the toe of the horizontal section after filling was measured to be 48.6%. Tubing was inserted into the casing, and the model casing was filled with water. The previously studied epoxy resin plugging agent XF3 system was used to perform a plugging operation on the oil well model. The basic properties of the XF3 plugging agent system are shown in Table 2 below.

[0093] Table 2 Basic Properties of the XF3 Epoxy Resin Blocking System

[0094]

[0095] 2) Simulation of plugging process of plugging agent in horizontal well

[0096] (1) Trial squeezing: Turn on the water pump and squeeze out clean water. Open the valve under the toe. If the water can be squeezed out smoothly, close the valve. If the model does not puncture or leak, it is qualified.

[0097] (2) Preparation of the plugging agent: 3 kg of epoxy resin, curing agent, diluent and toughening agent;

[0098] (3) Injection of plugging agent: Open the valve at the root of the horizontal section, first pump water to fill the ceramic particles and overflow from the monitoring valve, then close the valve. Install a rubber plug in front of the oil pipe to replace the upper water plugging tool during construction, then start the pump to inject 3Kg of plugging agent, and then use polymer solution to replace the water until 3Kg of plugging agent is injected into the leak to be sealed, and then wait for it to solidify under pressure.

[0099] 3) Effect Analysis and Evaluation

[0100] (1) The design of the horizontal well plugging tooling can meet the test requirements;

[0101] (2) The plugging agent system can be fully injected into the horizontal well model and has good fluidity; under certain pressure, it can be fully injected into the simulated formation and achieve a good plugging effect.

[0102] 2. Horizontal well field test

[0103] 1) Current Production Status

[0104] During the initial production phase, CLS-01 typically produces 3.46 ml of liquid per day. 3 The well produces 2.43 tons of oil per day with a water cut of 17.3%. Currently, the well is producing 12.45 cubic meters of fluid per day. 3 The well produces 0.0 tons of oil per day with a water content of 100%. In order to restore the production capacity of the single well and tap the potential of the oil well, it was decided to carry out water plugging operations on the well.

[0105] 2) Determine the water outlet point

[0106] Based on the water production characteristics of the horizontal well, the production profile testing method was first used to quantitatively and qualitatively analyze the water production point of well CLS-01. The results showed a leak point (2569.50m) above the perforated section. The total production of this point was 14.243 cubic meters per day, with a daily water production of 14.243 cubic meters per day. This was identified as the main water-producing layer, leading to high water cut, high fluid volume, and high dynamic fluid level in the horizontal well. To restore the well's production capacity, a targeted epoxy resin plugging operation was planned at the water production leak point at 2569.50m.

[0107] 3) Test plan and procedure

[0108] See Figure 17 Based on the water production characteristics of CLS-01 well, the water production type is fracture-type water breakthrough. The water shut-off scheme involves injecting a maximum pressure of 27 MPa, using polymer solution for the pre- and post-slugs, and epoxy resin plugging agent for the main slug. The usage amounts for each segment during construction are shown in Table 3.

[0109] Table 3. Design and dosage of plugging slugs for well CLS-01

[0110]

[0111] (1) Construction preparation work: Install equipment, prepare materials, conduct safety inspections and complete the pre-positioning of downhole tools, etc., to ensure the smooth progress of the construction process.

[0112] (2) Construction process: Open the casing gate valve, inject clean water into the tubing until fluid returns to the casing, close the casing gate valve, and squeeze 0.2m of 0.5% polymer solution into the tubing. 3 4.0m 3 Resin plugging agent and 0.5% polymer solution 0.2m 3 Stop the pump, pull out the tubing, and simultaneously backwash the well at a high flow rate until the inlet and outlet water quality is consistent. Pull out the tubing, close the casing valve, install a pressure gauge, and shut in the well for 72 hours to allow the water to solidify, observing the changes in wellhead pressure.

[0113] (3) After construction: After the sealant has solidified, drilling will be carried out and production will resume according to the original work system.

[0114] 4) Water-blocking effect

[0115] After drilling and grinding, the plugged wellbore was pressure tested at 15 MPa. The pressure did not drop after 30 minutes. Before plugging, the pressure was tested at 19 MPa, with a pressure drop of 10.5 MPa after 30 minutes. After plugging, the overflow rate decreased from 17 cubic meters per day to 0 cubic meters per day, and the overflow disappeared. After the water plugging operation, the oil production in well CLS-01 recovered. After water plugging, the daily fluid production of this horizontal well was 13.08 m³. 3 The daily oil production is 2.73 t / d, and the water content can be reduced to a minimum of 21.0%. This indicates that the epoxy resin plugging agent has a good plugging effect on the CLS-01 well.

[0116] The high-flexibility epoxy resin water-blocking agent of this invention selects epoxy resin (E-51) as the base material for the multifunctional epoxy resin water-blocking material. It possesses high epoxy value, low viscosity, high strength and hardness, and high heat and corrosion resistance, and has a large number of reactive epoxy groups. Because of these epoxy groups, the epoxy groups of the epoxy resin react with the amine groups of the amine curing agent. The reaction mechanism is as follows: Figure 15 As shown in (a), the primary amine of the curing agent can react with epoxy groups to generate secondary amines and hydroxyl groups. The secondary amine can also react with epoxy groups to generate tertiary amines. This reaction proceeds sequentially, gradually forming a three-dimensional network structure. See [reference needed]. Figure 18 Thus, they possess different superior properties.

[0117] The high-flexibility epoxy resin plugging agent of this invention uses dodecyl diglycidyl ether (AGE) and neopentyl glycol diglycidyl ether (678) as active diluents, the molecular structures of which are shown in Table 4. The main differences between the selected active diluents lie in their chain length and epoxy group equivalence, resulting in varying advantages when added to the epoxy resin plugging agent. Taking diluent 678 as an example, the mechanism by which the active diluent participates in the curing reaction of the epoxy resin plugging agent is as follows: Figure 15 As shown in (b), the epoxy groups and amine groups undergo a ring-opening reaction, allowing segments of diluent 678 to successfully connect to the network structure of the plugging agent. The properties of the plugging agent before and after curing can be effectively adjusted by changing the amount of diluent added.

[0118] Table 4. Molecular Structure of Diluents

[0119]

[0120] Example 6

[0121] 1) Cleaning the mold: The stretching mold, compression mold and steel sheet used for shearing were prepared according to national standards. Before preparation, they were cleaned with organic solvent, dried by heating, coated with a layer of release agent (silicone oil), assembled according to the prototype, and heated in an oven at 50.0±0.5℃ for 30 minutes.

[0122] 2) Preparation of the plugging agent: According to the mass ratio of 100:42:13:0.5, the heated epoxy resin (bisphenol A type epoxy resin E-51), amine curing agent (phenolic amine), reactive diluent (a mixture of neopentyl glycol diglycidyl ether (678) and dodecyl diglycidyl ether (AGE) in a mass ratio of 3:10) and imidazole toughening agent (a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole in a mass ratio of 1:2:0.8) are mixed and stirred evenly. Then, the mixture is placed in an oven at 50.0±0.5℃ and heated for 10 minutes. After filtration by vacuum pump, the mixture is placed back in the oven and heated for another 10 minutes. This process is repeated three times to obtain the resin plugging agent, which is recorded as the epoxy resin plugging agent system.

[0123] 3) Casting: Pour resin sealant along the inner wall of the mold through the pouring gate, and try to avoid generating air bubbles as much as possible throughout the entire operation.

[0124] 4) Vacuum degassing: Place the membrane containing the plugging agent into the vacuum oven, close the vent valve, open the vacuum valve, and set the temperature to 50.0±0.5℃. Turn on the vacuum pump to start evacuating air. When the vacuum level inside the oven reaches -0.1MPa, close the vacuum valve and perform degassing.

[0125] 5) Heating and curing: The membrane is cured in a vacuum environment at a temperature of 50.0±0.5℃. After being placed in a vacuum oven for 48 hours, it is demolded to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

[0126] Example 7

[0127] 1) Cleaning the mold: The stretching mold, compression mold and steel sheet used for shearing were prepared according to national standards. Before preparation, they were cleaned with organic solvent, dried by heating, coated with a layer of release agent (silicone oil), assembled according to the prototype, and heated in an oven at 50.0±0.5℃ for 30 minutes.

[0128] 2) Preparation of the plugging agent: According to the mass ratio of 100:52:20:1.5, the heated epoxy resin (bisphenol A type epoxy resin E-51), amine curing agent (a mixture of trivinyltetramine and phenolic amine in a mass ratio of 1:1), reactive diluent (a mixture of neopentyl glycol diglycidyl ether (678) and dodecyl diglycidyl ether (AGE) in a mass ratio of 20:10) and imidazole toughening agent (a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole in a mass ratio of 1:1:1) are mixed and stirred evenly. Then, the mixture is placed in an oven at 50.0±0.5℃ and heated for 10 minutes. After filtration by vacuum pump, the mixture is placed back in the oven and heated for another 10 minutes. This process is repeated three times to obtain the resin plugging agent, which is recorded as the epoxy resin plugging agent system.

[0129] 3) Casting: Pour resin sealant along the inner wall of the mold through the pouring gate, and try to avoid generating air bubbles as much as possible throughout the entire operation.

[0130] 4) Vacuum degassing: Place the membrane containing the plugging agent into the vacuum oven, close the vent valve, open the vacuum valve, and set the temperature to 50.0±0.5℃. Turn on the vacuum pump to start evacuating air. When the vacuum level inside the oven reaches -0.1MPa, close the vacuum valve and perform degassing.

[0131] 5) Heating and curing: The membrane is cured in a vacuum environment at a temperature of 50.0±0.5℃. After being placed in a vacuum oven for 60 hours, it is demolded to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

[0132] Example 8

[0133] 1) Cleaning the mold: The stretching mold, compression mold and steel sheet used for shearing were prepared according to national standards. Before preparation, they were cleaned with organic solvent, dried by heating, coated with a layer of release agent (silicone oil), assembled according to the prototype, and heated in an oven at 50.0±0.5℃ for 30 minutes.

[0134] 2) Preparation of the plugging agent: According to the mass ratio of 100:45:15:2.3, the heated epoxy resin (bisphenol A type epoxy resin E-51), amine curing agent (polyamide), reactive diluent (a mixture of neopentyl glycol diglycidyl ether (678) and dodecyl diglycidyl ether (AGE) in a mass ratio of 10:10) and imidazole toughening agent (a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole in a mass ratio of 1:1.5:1.4) are mixed and stirred evenly. Then, the mixture is placed in an oven at 50.0±0.5℃ and heated for 10 minutes. After filtration by vacuum pump, the mixture is placed back in the oven and heated for another 10 minutes. This process is repeated three times to obtain the resin plugging agent, which is recorded as the epoxy resin plugging agent system.

[0135] 3) Casting: Pour resin sealant along the inner wall of the mold through the pouring gate, and try to avoid generating air bubbles as much as possible throughout the entire operation.

[0136] 4) Vacuum degassing: Place the membrane containing the plugging agent into the vacuum oven, close the vent valve, open the vacuum valve, and set the temperature to 50.0±0.5℃. Turn on the vacuum pump to start evacuating air. When the vacuum level inside the oven reaches -0.1MPa, close the vacuum valve and perform degassing.

[0137] 5) Heating and curing: The membrane is cured in a vacuum environment at a temperature of 50.0±0.5℃. After being placed in a vacuum oven for 72 hours, it is demolded to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

[0138] Example 9

[0139] 1) Cleaning the mold: The stretching mold, compression mold and steel sheet used for shearing were prepared according to national standards. Before preparation, they were cleaned with organic solvent, dried by heating, coated with a layer of release agent (silicone oil), assembled according to the prototype, and heated in an oven at 50.0±0.5℃ for 30 minutes.

[0140] 2) Preparation of the plugging agent: According to the mass ratio of 100:48:30:2.5, the heated epoxy resin (bisphenol A type epoxy resin E-51), amine curing agent (a mixture of vinyltriamine and ethylenediamine in a mass ratio of 1:1), reactive diluent (a mixture of neopentyl glycol diglycidyl ether (678) and dodecyl diglycidyl ether (AGE) in a mass ratio of 5:10), and imidazole toughening agent (a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole in a mass ratio of 1:1.2:1.2) are mixed and stirred evenly. Then, the mixture is placed in an oven at 50.0±0.5℃ and heated for 10 minutes. After filtration by vacuum pump, the mixture is placed back in the oven and heated for another 10 minutes. This process is repeated three times to obtain the resin plugging agent, which is recorded as the epoxy resin plugging agent system.

[0141] 3) Casting: Pour resin sealant along the inner wall of the mold through the pouring gate, and try to avoid generating air bubbles as much as possible throughout the entire operation.

[0142] 4) Vacuum degassing: Place the membrane containing the plugging agent into the vacuum oven, close the vent valve, open the vacuum valve, and set the temperature to 50.0±0.5℃. Turn on the vacuum pump to start evacuating air. When the vacuum level inside the oven reaches -0.1MPa, close the vacuum valve and perform degassing.

[0143] 5) Heating and curing: The membrane is cured in a vacuum environment at a temperature of 50.0±0.5℃. After being placed in a vacuum oven for 65 hours, it is demolded to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

[0144] Example 10

[0145] 1) Cleaning the mold: The stretching mold, compression mold and steel sheet used for shearing were prepared according to national standards. Before preparation, they were cleaned with organic solvent, dried by heating, coated with a layer of release agent (silicone oil), assembled according to the prototype, and heated in an oven at 50.0±0.5℃ for 30 minutes.

[0146] 2) Preparation of the plugging agent: According to the mass ratio of 100:50:25:0.7, the heated epoxy resin (bisphenol A type epoxy resin E-51), amine curing agent (a mixture of trivinyltetramine and phenolic amine in a mass ratio of 1:1), reactive diluent (a mixture of neopentyl glycol diglycidyl ether (678) and dodecyl diglycidyl ether (AGE) in a mass ratio of 15:10) and imidazole toughening agent (a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole in a mass ratio of 1:1.8:1) are mixed and stirred evenly. Then, the mixture is placed in an oven at 50.0±0.5℃ and heated for 10 minutes. After filtration by vacuum pump, the mixture is placed back in the oven and heated for another 10 minutes. This process is repeated three times to obtain the resin plugging agent, which is recorded as the epoxy resin plugging agent system.

[0147] 3) Casting: Pour resin sealant along the inner wall of the mold through the pouring gate, and try to avoid generating air bubbles as much as possible throughout the entire operation.

[0148] 4) Vacuum degassing: Place the membrane containing the plugging agent into the vacuum oven, close the vent valve, open the vacuum valve, and set the temperature to 50.0±0.5℃. Turn on the vacuum pump to start evacuating air. When the vacuum level inside the oven reaches -0.1MPa, close the vacuum valve and perform degassing.

[0149] 5) Heating and curing: The membrane is cured in a vacuum environment at a temperature of 50.0±0.5℃. After being placed in a vacuum oven for 55 hours, it is demolded to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

[0150] The high-flexibility epoxy resin plugging agent of this invention uses imidazole toughening agents, specifically 2-ethylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole, as a compound toughening agent. In the initial experimental stage, ester and silicone oil toughening agents were used as additives. The results showed that the temperature resistance and tensile shear properties of the plugging agent with these additives failed to meet the technical specifications. Therefore, this invention selects imidazole toughening agents to further optimize the performance of the epoxy resin plugging agent system. The main reason is that the CN bond on the imidazole ring in the imidazole toughening agent also participates in the curing reaction, which can improve the flexibility of the plugging agent and further improve its performance.

[0151] In the preparation process of the high-flexibility epoxy resin plugging agent of this invention, the amount of diluent and toughening agent added has a significant impact on the strength properties of the plugging agent after curing. The compressive strength and tensile shear strength of the cured epoxy resin plugging agent both show a trend of first increasing and then decreasing with the addition of diluent and toughening agent. For the plugging agent system, the diluent participates in the curing reaction, increasing the crosslinking density of the system, and its post-curing compressive strength is also improved. However, the increased number of C-chains affects the rigid network, so the increase in compressive strength in the later stages is reduced. Simultaneously, imidazole toughening agents can promote the curing reaction and increase the crosslinking density of the plugging agent, but excessive imidazole will lead to an increase in stress concentration points, reducing the strength of the plugging agent. Therefore, during the preparation of the plugging agent, the amount of diluent and toughening agent added should be reasonably adjusted to ensure optimal plugging agent performance.

[0152] The high-flexibility epoxy resin water-plugging agent system provided by this invention features low viscosity, good adhesion, high flexibility, and high strength after curing. It exhibits good injection fluidity, wide applicability, and excellent plugging effect even in high-temperature and high-salt environments. Through indoor water-plugging simulation experiments and field plugging of horizontal wells in low-permeability reservoirs, the high-flexibility epoxy resin water-plugging agent of this invention demonstrates good fluidity and plugging effect. After plugging, oil well production increases significantly, water cut decreases, and well utilization is improved, resulting in enhanced economic benefits.

[0153] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0154] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A highly flexible epoxy resin water-plugging agent for horizontal wells, characterized in that, It includes epoxy resin, amine curing agent, reactive diluent and imidazole toughening agent in a mass ratio of 100:42-52:13-30:0.5-2.5; The epoxy resin used is bisphenol A type epoxy resin E-51; The amine curing agent is one or more of ethylenediamine, vinyltriamine, trivinyltetraamine, phenolic amine, and polyamide; The active diluent is a mixture of neopentyl glycol diglycidyl ether and dodecyl diglycidyl ether prepared in a mass ratio of 3-20:10; The imidazole toughening agent is a mixture of 2-methylimidazole, 2-phenylimidazole and 1-benzyl-2-methylimidazole in a mass ratio of 1:1-2:0.8-1.

4.

2. A method for preparing a high-flexibility epoxy resin water-plugging agent for horizontal wells as described in claim 1, characterized in that, Includes the following steps: 1) After heating, the epoxy resin, amine curing agent, reactive diluent and imidazole toughening agent are mixed and stirred evenly, and then heated to obtain resin plugging agent; 2) The resin plugging agent is subjected to vacuum degassing treatment; 3) The vacuum degassing treatment is then subjected to a heating and curing reaction to obtain a high-flexibility epoxy resin water plugging agent for horizontal wells.

3. The method for preparing the high-flexibility epoxy resin water-blocking agent for horizontal wells according to claim 2, characterized in that, The temperature for vacuum degassing is 49.5-51.5℃, and the vacuum degree is -0.1 MPa.

4. The method for preparing the high-flexibility epoxy resin water-blocking agent for horizontal wells according to claim 2, characterized in that, The temperature for the heating and curing reaction is 49.5-51.5℃, and the time is 48-72 h.

Images