Temporary plugging agent and preparation method thereof

Abstract

The invention provides a temporary plugging agent and a preparation method thereof. Raw materials of the temporary plugging agent comprise resin and modified particles, and raw materials of the modified particles comprise rigid particles wrapped by composite membranes and a modifier; the modifier is a mixture containing a silane coupling agent and a film-forming agent; the composite membrane is prepared from polyethyleneimine, polyallylamine hydrochloride and nano silicon dioxide. The preparation method of the temporary plugging agent comprises the following steps: sequentially immersing rigid particles into a polyallylamine hydrochloride solution, a nano silicon dioxide dispersion liquid, a polyethyleneimine solution and a nano silicon dioxide dispersion liquid, and repeating for 20-100 times to obtain rigid particles wrapped by a composite film; mixing the rigid particles wrapped by the composite film, a silane coupling agent and a film-forming agent, and heating to obtain modified particles; and mixing the modified particles with resin, and curing to obtain the temporary plugging agent. The temporary plugging agent provided by the invention has good toughness and relatively high strength, and can be used for plugging the interior of a crack through good deformability.

Description

A temporary plugging agent and its preparation method Technical Field

[0001] This invention relates to the field of oil drilling technology, specifically to a temporary plugging agent and its preparation method. Background Technology

[0002] Currently, fractured formations exhibit large leakage channels and rapid leakage rates, making it difficult to form a structurally stable, dense, and pressure-bearing sealing layer within the fractures. This results in significant challenges for on-site drilling fluid plugging operations, often leading to substantial economic losses. With the increasing prominence of drilling fluid leakage problems in complex formations, highly efficient leakage prevention and plugging materials have become crucial for the rapid and efficient treatment of well leakage. Domestic and international experts have conducted extensive research on leakage prevention and plugging materials. Existing plugging materials can be classified into bridging plugging materials, high-water-loss plugging materials, temporary plugging materials, chemical plugging materials, inorganic cementing plugging materials, and soft (hard) plugging materials according to different mechanisms and functions. However, the above-mentioned traditional plugging materials do not have intelligent characteristics and cannot deform according to formation temperature. When dealing with leakage in wells with large-aperture fractures, the use of conventional large-particle-size, high-density plugging materials has poor suspension stability, which leads to settling in the mud tank or in the wellbore when dealing with long open-hole sections. On the other hand, it may cause drill string blockage. In addition, traditional bridging plugging materials are highly sensitive to fractures and cannot effectively seal fractures adaptively. They also lack rigidity, high strength, and expansion properties.

[0003] With increasing understanding of new materials, more and more resin materials are being applied to drilling engineering plugging and leak sealing operations. In recent years, domestic and international scholars have conducted extensive research on the challenge of crack plugging during drilling. Intelligent leak sealing products made primarily from shape memory resin materials can achieve automatic bridging and plugging, reservoir protection, and the plugging time and start-up temperature can be controlled. Phase change resins possess phase change characteristics and shape memory functions, allowing them to better penetrate fractures. Some resins with deformation functions can adaptively and effectively plug fractures. For example, Wang Zhaohui et al. used thermosetting shape memory epoxy resin as the base material and improved compressibility by adding hollow glass microspheres, forming a shape memory epoxy resin composite foam. Finally, they successfully prepared a temperature-sensitive expandable intelligent leak sealing agent, SMP-LCM, with different response temperatures and expansion ratios. The developed shape memory foam plugging agent is a thermosensitive expansion plugging material. It can penetrate deep into the leakage layer at a relatively small size and expand at formation temperature. Through the recovery stress generated by its shape memory effect, it effectively reinforces the wellbore without fracturing the formation, thereby improving the pressure-bearing capacity of the weak formation. It is increasingly recognized that using phase change resin to coat plugging particles for sealing and plugging will effectively improve the sealing effect, especially for fracture-related leakage.

[0004] However, currently used shape memory resin materials suffer from poor toughness, low strength, and poor thermodynamic properties in complex drilling fluid environments. They are easily worn away by the solid phase in the drilling fluid, deform under high formation pressure, leading to bridging failure of the sealing layer; and their shape memory performance deteriorates at high temperatures, resulting in a loss of deformation sealing effectiveness. These problems require further solutions. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention proposes a temporary plugging agent and its preparation method.

[0006] In a first aspect, the present invention proposes a temporary plugging agent, the raw materials of which include resin and modified particles. The raw materials of the modified particles include: rigid particles encapsulated in a composite membrane and a modifier; the modifier is a mixture containing a silane coupling agent and a film-forming agent; the composite membrane is prepared from polyethyleneimine (BPEI), polyallylamine hydrochloride (PAH), and nano-silica.

[0007] In a specific embodiment of the present invention, the mass ratio of resin to modified particles in the temporary plugging agent is 3-1:1-2.

[0008] In a specific embodiment of the present invention, the mass ratio of the rigid particles wrapped in the composite film, the silane coupling agent, and the film-forming agent in the modified particles is (75-90):(5-12):(5-13).

[0009] As a specific embodiment of the present invention, the mass ratio of the composite membrane to the rigid particles in the composite membrane-encapsulated rigid particles is (1:270-200).

[0010] As a specific embodiment of the present invention, the rigid particles are selected from at least one of calcium carbonate particles, quartz sand particles, and elastic graphite particles.

[0011] Preferably, the rigid particles have a particle size of 20–200 μm.

[0012] As a specific embodiment of the present invention, the film-forming agent is selected from at least one of polyethylene emulsion (PE), polyacrylamide emulsion (PAM), and polyvinyl pyrrolidone emulsion (PVP).

[0013] Preferably, the concentration of the polyethylene emulsion is 18wt% to 20wt%, the concentration of the polyacrylamide emulsion is 0.05wt% to 1wt%, and the concentration of the polyvinylpyrrolidone emulsion is 3wt% to 10wt%.

[0014] Specifically, the solvent in polyethylene emulsion, polyacrylamide emulsion, and ethylene-acrylic acid copolymer emulsion is water.

[0015] As a specific embodiment of the present invention, the silane coupling agent is selected from at least one of KH550, KH560, and KH580.

[0016] As a specific embodiment of the present invention, the glass transition temperature of the resin is 100℃~150℃.

[0017] Preferably, the resin is selected from at least one of epoxy resin, polypropylene resin, and polyvinyl chloride resin.

[0018] Specifically, the epoxy resin used in this invention is a bisphenol A type epoxy resin.

[0019] In a specific embodiment of the present invention, the temporary plugging agent is a particulate material with a particle size of 50 μm to 250 μm, a tensile strength of 37 to 43 MPa, a flexural modulus of 5 to 6.1 GPa, and a storage modulus of 4 to 6 GPa.

[0020] In a second aspect, the present invention provides a method for preparing the temporary plugging agent provided in the first aspect of the present invention, comprising the following steps:

[0021] (1) The rigid particles were sequentially immersed in polyallylamine hydrochloride solution, nano silica dispersion, polyethyleneimine solution and nano silica dispersion, and repeated 20 to 100 times to obtain rigid particles wrapped in a composite film.

[0022] The repetition of 20 to 100 times in this invention means that the complete immersion process in step (1) is repeated 20 to 100 times.

[0023] (2) The rigid particles wrapped in the composite membrane, the silane coupling agent and the film-forming agent are mixed and heated to obtain modified particles;

[0024] (3) The modified particles are mixed with resin and cured to obtain a temporary plugging agent.

[0025] As a specific embodiment of the present invention, the solubility of the polyallylamine hydrochloride solution is 0.1wt% to 0.5wt%, the pH value of the polyallylamine hydrochloride solution is 9.5 to 10.5, and the solvent of the polyallylamine hydrochloride solution is water.

[0026] As a specific embodiment of the present invention, the concentration of the polyethyleneimine solution is 0.1wt% to 0.5wt%, the pH value of the polyethyleneimine solution is 9.5 to 10.5, and the solvent of the polyethyleneimine solution is water.

[0027] As a specific embodiment of the present invention, the content of nano-silica in the nano-silica dispersion is 0.1wt% to 0.5wt%, the pH value of the nano-silica dispersion is 9.5 to 10.5, and the dispersant of the nano-silica dispersion is water.

[0028] Preferably, the particle size of the nano-silica is 0.1–0.5 μm.

[0029] As a specific embodiment of the present invention, the immersion time in step (1) is 5 to 10 minutes each time.

[0030] As a specific embodiment of the present invention, the heating temperature in step (2) is 60℃~90℃.

[0031] As a specific embodiment of the present invention, the curing conditions in step (3) include: a temperature of 110℃~150℃ and a time of 2~6h.

[0032] As a specific embodiment of the present invention, step (3) further includes preheating and stirring before curing.

[0033] Preferably, the preheating temperature is 70℃~90℃ and the time is 1~2h.

[0034] As a specific embodiment of the present invention, the stirring conditions are a rotation speed of 100-500 r / min and a stirring time of 10-60 min.

[0035] In this invention, the modified resin coated with the composite membrane material is preheated at 70℃~90℃ for 1~2h, melted and stirred, and then heated to 110℃~150℃ and cured for 2~6h.

[0036] Thirdly, the present invention provides a drilling fluid comprising the temporary plugging agent provided in the first aspect of the present invention or the temporary plugging agent prepared by the preparation method provided in the second aspect of the present invention, wherein the content of the temporary plugging agent in the drilling fluid is 3wt% to 8wt%, the plugging pressure of the plugging layer formed by the drilling fluid is ≥7MPa, and the leakage of the plugging layer is 150 to 260mL.

[0037] Compared with the prior art, the present invention has the following beneficial effects.

[0038] The temporary plugging agent provided by this invention has good toughness and high strength, is not easily worn away by the solid phase in the drilling fluid, can be used to plug leaks inside the cracks through good deformation ability, improve the plugging effect, and is not easily squeezed and destroyed or broken under high formation pressure.

[0039] The temporary plugging agent provided by this invention, through coating and modification, greatly improves its compatibility and bonding ability with resin materials, significantly enhances the mechanical and thermodynamic properties (storage modulus) of the coating and plugging materials, and helps to better exert the plugging effect in complex drilling fluid environments.

[0040] This invention provides a temporary plugging agent, which incorporates materials such as BPEI, PAH, silica, and film-forming agents. This agent effectively strengthens the coating and sealing materials, significantly improving the adhesion and shearing properties of the plugging agent prepared from the coating material in the drilling fluid and enhancing its retention capacity in fractures. Consequently, it can further improve the plugging effect on larger fractures. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0042] PAH, BPEI, silica (particle size 0.1-0.5μm), epoxy resin, polypropylene resin, and polyvinyl chloride resin were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0043] Silane coupling agents KH550, KH560, and KH580 were purchased from Shandong Huachen New Materials Co., Ltd.

[0044] PE (polyethylene) emulsion (18wt%) was purchased from Shanghai Xinnuo Chemical Co., Ltd.

[0045] PAM (polyacrylamide) emulsion (1 wt%) was purchased from Wuxi Tianxin Chemical Co., Ltd.

[0046] PVP (polyvinylpyrrolidone) emulsion (10wt%) was purchased from Jiafeng Chemical Co., Ltd.

[0047] Calcium carbonate granules, with a particle size of 20–200 μm, were purchased from Qimei Minerals Co., Ltd.

[0048] Elastic graphite particles, with a particle size of 20–200 μm, were purchased from Qingdao Tianheda Graphite Co., Ltd.

[0049] Example 1

[0050] (1) Coating of rigid particles: PAH solution (0.1% wt, pH=10) and BPEI solution (0.1% wt, pH=10) and nano silica dispersion (0.1% wt, pH=10) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0051] Calcium carbonate particles were sequentially and completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion, with each immersion lasting 5 minutes. During the intervals, excess solution that had not been adsorbed onto the particles was rinsed off with deionized water, and the particles were dried with nitrogen gas. This process was repeated 80 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0052] (2) Modification of rigid particles coated with composite membrane: rigid particles coated with composite membrane, silane coupling agent KH550 and film-forming agent PE emulsion are mixed in a mass ratio of 80:10:10, then heated to 80℃ and stirred; cooled and dried to obtain modified particles.

[0053] (3) Blending and curing of resin material and modified particles: After mixing epoxy resin and modified particles (the mass ratio of epoxy resin to modified particles is 2:1), preheat at 90°C for 1 hour. After the resin material melts, stir at low speed (stirring speed 200 r / min) for 20 minutes. Then heat to 110°C and cure for 4 hours to obtain the cured material.

[0054] (4) The solidified material is crushed and granulated to obtain particles with a particle size of 150μm, thus obtaining a temporary plugging agent.

[0055] Example 2

[0056] (1) Coating of rigid particles: PAH solution (0.5% wt, pH=9.5) and BPEI solution (0.5% wt, pH=9.5) and nano silica dispersion (0.5% wt, pH=9.5) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0057] Calcium carbonate particles were completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion for 10 minutes each time. During the intervals, excess solution that had not been adsorbed onto the particles was washed off with deionized water, and the particles were dried with nitrogen gas. This step was repeated 20 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0058] (2) Modification of rigid particles coated with composite membrane: rigid particles coated with composite membrane, silane coupling agent KH550 and film-forming agent PE emulsion are mixed in a mass ratio of 75:12:13, then heated to 60℃ and stirred; cooled and dried to obtain modified particles.

[0059] (3) Blending and curing of resin material and modified particles: After mixing epoxy resin and modified particles (the mass ratio of epoxy resin to modified particles is 3:1), preheat at 70°C for 2 hours. After the resin material melts, stir at low speed (stirring speed 100r / min) for 60 minutes. Then heat to 150°C and cure for 2 hours to obtain the cured material.

[0060] (4) The solidified material is crushed and granulated to obtain particles with a particle size of 200μm, thus obtaining a temporary plugging agent.

[0061] Example 3

[0062] (1) Coating of rigid particles: PAH solution (0.2% wt, pH=10.5) and BPEI solution (0.2% wt, pH=10.5) and nano silica dispersion (0.2% wt, pH=10.5) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0063] Elastic graphite particles were sequentially and completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion, with each immersion time being 8 minutes. During the intervals, excess solution that had not been adsorbed onto the particles was washed off with deionized water, and the particles were dried with nitrogen gas. This step was repeated 100 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0064] (2) Modification of rigid particles coated with composite membrane: rigid particles coated with composite membrane, silane coupling agent KH550 and film-forming agent PE emulsion are mixed in a mass ratio of 90:5:5, then heated to 90℃ and stirred; cooled and dried to obtain modified particles.

[0065] (3) Blending and curing of resin material and modified particles: After mixing epoxy resin and modified particles (the mass ratio of epoxy resin to modified particles is 3:2), preheat at 80°C for 1.5h. After the resin material melts, stir at low speed (stirring speed 200r / min) for 30min. Then heat to 120°C and cure for 6h to obtain the cured material.

[0066] (4) The solidified material is crushed and granulated to obtain particles with a particle size of 50 μm, thus obtaining a temporary plugging agent.

[0067] Example 4

[0068] (1) Coating of rigid particles: PAH solution (0.1% wt, pH=10.5) and BPEI solution (0.1% wt, pH=10.5) and nano silica dispersion (0.1% wt, pH=10.5) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0069] Calcium carbonate particles were sequentially and completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion, with each immersion lasting 8 minutes. During the intervals, excess solution that had not been adsorbed onto the particles was rinsed off with deionized water, and the particles were dried with nitrogen gas. This process was repeated 100 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0070] (2) Modification of rigid particles coated with composite membrane: rigid particles coated with composite membrane, silane coupling agent KH580 and film-forming agent PVP emulsion are mixed in a mass ratio of 90:5:5, then heated to 90℃ and stirred; cooled and dried to obtain modified particles.

[0071] (3) Blending and curing of resin material and modified particles: After mixing polyvinyl chloride resin and modified particles (the mass ratio of polyvinyl chloride resin to modified particles is 2:1), preheat at 80°C for 1.5h. After the resin material melts, stir at low speed (200r / min) for 30min. Then heat to 120°C and cure for 6h to obtain the cured material.

[0072] (4) The solidified material is crushed and granulated to obtain particles with a particle size of 50 μm, thus obtaining a temporary plugging agent.

[0073] Example 5

[0074] (1) Coating of rigid particles: PAH solution (0.1% wt, pH=10.5) and BPEI solution (0.1% wt, pH=10.5) and nano silica dispersion (0.1% wt, pH=10.5) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0075] Calcium carbonate particles were sequentially and completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion, with each immersion lasting 8 minutes. During the intervals, excess solution that had not been adsorbed onto the particles was rinsed off with deionized water, and the particles were dried with nitrogen gas. This process was repeated 100 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0076] (2) Modification of rigid particles coated with composite membrane: rigid particles coated with composite membrane, silane coupling agent KH560, and film-forming agent PAM emulsion are mixed in a mass ratio of 90:5:5, then heated to 90℃ and stirred; cooled and dried to obtain modified particles.

[0077] (3) Blending and curing of resin material and modified particles: After mixing polypropylene resin and modified particles (the mass ratio of polypropylene resin to modified particles is 2:1), preheat at 80°C for 1.5h. After the resin material melts, stir at low speed (stirring speed 200r / min) for 30min. Then heat to 120°C and cure for 6h to obtain the cured material.

[0078] (4) The solidified material is crushed and granulated to obtain particles with a particle size of 50 μm, thus obtaining a temporary plugging agent.

[0079] Comparative Example 1

[0080] Comparative Example 1 was set up based on Example 1. The difference between Comparative Example 1 and Example 1 is that the rigid particles are not coated with a composite film.

[0081] The preparation steps are as follows:

[0082] (1) Modification of rigid particles: Calcium carbonate particles, silane coupling agent KH550 and film-forming agent PE emulsion are mixed in a mass ratio of 80:10:10, then heated to 80℃ and stirred; cooled and dried to obtain modified particles.

[0083] (2) Blending and curing of resin material and modified particles: After mixing epoxy resin and modified particles (the mass ratio of epoxy resin to modified particles is 2:1), preheat at 90°C for 1 hour. After the resin material melts, stir at low speed (stirring speed 200 r / min) for 20 minutes. Then heat to 110°C and cure for 4 hours to obtain the cured material.

[0084] (3) The solidified material is crushed and granulated to obtain particles with a particle size of 150μm, thus obtaining a temporary plugging agent.

[0085] Comparative Example 2

[0086] Comparative Example 1 was set up based on Example 1. The difference between Comparative Example 1 and Example 1 is that the rigid particles wrapped in the composite film are not modified.

[0087] The preparation steps are as follows:

[0088] (1) Coating of rigid particles: PAH solution (0.1% wt, pH=10) and BPEI solution (0.1% wt, pH=10) and nano silica dispersion (0.1% wt, pH=10) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0089] Calcium carbonate particles were sequentially and completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion, with each immersion lasting 5 minutes. During the intervals, excess solution that had not been adsorbed onto the particles was rinsed off with deionized water, and the particles were dried with nitrogen gas. This process was repeated 80 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0090] (2) Blending and curing of resin material with rigid particles coated with composite film: After mixing epoxy resin with rigid particles coated with composite film (the mass ratio of epoxy resin to modified particles coated with composite film is 2:1), the mixture is preheated at 90°C for 1 hour. After the resin material melts, it is stirred at low speed (200 r / min) for 20 minutes. Then it is heated to 110°C and cured for 4 hours to obtain the cured material.

[0091] (3) The solidified material is crushed and granulated to obtain particles with a particle size of 150μm, thus obtaining a temporary plugging agent.

[0092] Comparative Example 3

[0093] Comparative Example 1 was set up based on Example 1. The difference between Comparative Example 1 and Example 1 is that it does not include the step of blending and curing the modified particles with the resin material.

[0094] (1) Coating of rigid particles: PAH solution (0.1% wt, pH=10) and BPEI solution (0.1% wt, pH=10) and nano silica dispersion (0.1% wt, pH=10) were prepared with deionized water, and the pH value of the solution was adjusted with hydrochloric acid or sodium hydroxide.

[0095] Calcium carbonate particles were sequentially and completely immersed in PAH solution, nano-silica dispersion, BPEI solution, and nano-silica dispersion, with each immersion lasting 5 minutes. During the intervals, excess solution that had not been adsorbed onto the particles was rinsed off with deionized water, and the particles were dried with nitrogen gas. This process was repeated 80 times to complete the coating of the particles with the composite membrane material, resulting in rigid particles encapsulated by the composite membrane.

[0096] (2) Modification of rigid particles coated with composite membrane: rigid particles coated with composite membrane, silane coupling agent KH550 and film-forming agent PE emulsion are mixed in a mass ratio of 80:10:10, then heated to 80℃ and stirred; cooled and dried to obtain modified particles.

[0097] (3) The modified particles are further crushed into particles with a particle size of 150 μm to obtain a temporary plugging agent.

[0098] Performance testing

[0099] Experimental Example 1 - Tensile Strength Test:

[0100] Referring to the national standard GB / T 2567-2008 "Test Methods for Performance of Resin Castings", a universal testing machine (Jiangsu Tianyuan Testing Equipment Co., Ltd., model TY8000) was used to select dumbbell-shaped specimens to test the tensile properties of drilling fluid plugging agents at room temperature. The formula for calculating tensile strength is shown below.

[0101]

[0102] In the formula: σ t —Tensile strength, in megapascals (MPa); P—Destructive load (or maximum load), in newtons (N); b—Specimen width, in millimeters (mm); h—Specimen thickness, in millimeters (mm). The test results are shown in Table 1.

[0103] Table 1

[0104] Serial Number | Temporary Plugging Agent Tensile Strength (MPa) | 1 | Example 1 | 42.17 | 2 | Example 2 | 39.04 | 3 | Example 3 | 38.91 | 4 | Example 4 | 37.05 | 5 | Example 5 | 38.69 | 6 | Comparative Example 1 | 32.92 | 7 | Comparative Example 2 | 31.58 | 8 | Comparative Example 3 | 27.76 surface

[0105] The results in Table 1 show that the temporary plugging agents prepared in the embodiments of the present invention have high tensile strength. Furthermore, the tensile strength of the temporary plugging agents prepared in Examples 1-5 of the present invention is greater than that of the temporary plugging agents prepared in Comparative Examples 1-3. This indicates that the steps of encapsulating the rigid particles in the composite membrane, modifying the rigid particles encapsulating the composite membrane, and blending the modified particles with the resin material during the preparation of the temporary plugging agent have a very good effect on improving the tensile strength of the temporary plugging agent.

[0106] Experimental Example 2 - Flexural Modulus Test:

[0107] The flexural modulus of the temporary plugging agent was characterized by measuring the stress-strain at room temperature using a three-point bending test. The three-point bending test was conducted according to GB / T1449—2005 using a WDWT200 microcomputer-controlled electronic universal testing machine. According to the standard, the specimen dimensions were 50mm × 15mm × 2mm, with an effective span of 32mm. The flexural modulus was calculated based on the load-deflection curve obtained from the three-point bending test using the following formula:

[0108] E=LΔp / (4b×h 3 ×ΔS)

[0109] In the formula, E is the flexural modulus; L is the effective span of the specimen; Δp is the load increment of the initial straight segment on the load-deflection curve; b is the specimen width; h is the specimen thickness; and ΔS is the displacement increment corresponding to the load increment Δp. The experimental results are shown in Table 2.

[0110] Table 2

[0111] Serial Number | Temporary Plugging Agent | Flexural Modulus (GPa) | 1 | Example 1 | 6.1 | 2 | Example 2 | 5.7 | 3 | Example 3 | 5.9 | 4 | Example 4 | 5.0 | 5 | Example 5 | 5.4 | 6 | Comparative Example 1 | 2.5 | 7 | Comparative Example 2 | 2.2 | 8 | Comparative Example 3 | 1.6 surface

[0112] The results in Table 2 show that the temporary plugging agents prepared in the embodiments of the present invention have a large flexural modulus, indicating that the temporary plugging agents in the present invention have a high degree of internal cross-linking and can hinder crack propagation, thus resulting in a high flexural modulus. Furthermore, the flexural modulus of the temporary plugging agents prepared in Examples 1-5 of the present invention is greater than that of the temporary plugging agents prepared in Comparative Examples 1-3. This indicates that the steps of encapsulating the rigid particles in the composite film, modifying the rigid particles encapsulating the composite film, and blending the modified particles with the resin material in the preparation process of the temporary plugging agent have a very good effect on improving the flexural modulus of the temporary plugging agent.

[0113] Experiment Example 3 - Energy Storage Modulus Test:

[0114] The storage modulus of the temporary plugging agent at different temperatures was determined using a DMA Q850 dynamic thermomechanical analyzer to evaluate its dynamic thermo-mechanical properties. The specific test method was as follows: the sample size was 30mm × 10mm × 2mm, the clamping length was 17.5mm, a single cantilever mode was used, the frequency was 1Hz, the temperature range was 0–140℃, and the heating rate was 5℃ / min. The experimental results are shown in Table 3.

[0115] Table 3

[0116]

[0117] The results in Table 3 show that the temporary plugging agents prepared in the embodiments of the present invention have a large storage modulus, indicating that the materials prepared in the embodiments of the present invention have good thermodynamic properties. Furthermore, the storage modulus of the temporary plugging agents prepared in Examples 1-5 of the present invention is greater than that of Comparative Examples 1-3. This indicates that the steps of encapsulating the rigid particles with the composite membrane, modifying the rigid particles encapsulating the composite membrane, and blending the modified particles with the resin material during the preparation of the temporary plugging agent are beneficial to improving the thermodynamic properties of the temporary plugging agent.

[0118] Experiment Example 4 - Leak-stopping Performance Test:

[0119] The performance of the temporary plugging agent was evaluated. An evaluation experiment was conducted using a wedge-shaped long crack sealing test device to test the pressure-bearing capacity of the sealing layer and the leakage rate of the crack. The results of the plugging evaluation experiment are shown in Table 4.

[0120] The drilling fluid base formulation consists of bentonite slurry, walnut shells, sawdust, and calcium carbonate. Based on the weight of the bentonite slurry, the amount of walnut shells added is 3 wt%, the amount of sawdust added is 3 wt%, and the amount of calcium carbonate added is 4 wt%. Temporary plugging agents prepared in different embodiments are added to the plugging fluid base formulation at an amount of 5 wt%. Test results are shown in Table 4.

[0121] Table 4

[0122]

[0123] The results in Table 4 show that adding the temporary plugging agent prepared in the examples of this invention to the basic formulation of the plugging fluid results in a high pressure-bearing capacity of the sealing layer and a low leakage rate from the cracks, indicating that the temporary plugging agent prepared in the examples has a better plugging effect. Meanwhile, the temporary plugging agents prepared in Examples 1-5 have high pressure-bearing capacity, and the leakage rate from the cracks is significantly lower than that of the temporary plugging agents prepared in Examples 1-3. This indicates that the steps of encapsulating the composite membrane with rigid particles, modifying the rigid particles covering the composite membrane, and blending the modified particles with the resin material during the preparation of the temporary plugging agent are beneficial to improving the plugging effect.

[0124] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A temporary plugging agent, characterized in that, The raw materials of the temporary plugging agent include resin and modified particles; the raw materials of the modified particles include: rigid particles wrapped in a composite membrane and a modifier; the modifier is a mixture containing a silane coupling agent and a film-forming agent; the composite membrane is prepared from polyethyleneimine, polyallylamine hydrochloride and nano-silica.

2. The temporary plugging agent according to claim 1, characterized in that, The mass ratio of resin to modified particles in the temporary plugging agent is 3-1:1-2; and / or, the mass ratio of rigid particles wrapped in composite membrane, silane coupling agent, and film-forming agent in the modified particles is (75-90):(5-12):(5-13); and / or, the mass ratio of composite membrane to rigid particles in the rigid particles wrapped in composite membrane is (1:270-200).

3. The temporary plugging agent according to claim 1 or 2, characterized in that, The rigid particles are selected from at least one of calcium carbonate particles, quartz sand particles, and elastic graphite particles; preferably, the particle size of the rigid particles is 20 to 200 μm.

4. The temporary plugging agent according to claim 1 or 2, characterized in that, The film-forming agent is selected from at least one of polyethylene emulsion, polyacrylamide emulsion, and polyvinylpyrrolidone emulsion; preferably, the concentration of the polyethylene emulsion is 18wt% to 20wt%, the concentration of the polyacrylamide emulsion is 0.05wt% to 1wt%, and the concentration of the polyvinylpyrrolidone emulsion is 3wt% to 10wt%; and / or, the silane coupling agent is selected from at least one of KH550, KH560, and KH580; and / or, the glass transition temperature of the resin is 100℃ to 150℃; preferably, the resin is selected from at least one of epoxy resin, polypropylene resin, and polyvinyl chloride resin.

5. The temporary plugging agent according to any one of claims 1 to 4, characterized in that, The temporary plugging agent is a particulate material with a particle size of 50μm to 250μm. The tensile strength of the temporary plugging agent is 37 to 43 MPa, the flexural modulus of the temporary plugging agent is 5 to 6.1 GPa, and the storage modulus of the temporary plugging agent is 4 to 6 GPa.

6. A method for preparing the temporary plugging agent according to any one of claims 1 to 5, characterized in that, The process includes the following steps: (1) Immersing rigid particles sequentially in polyallylamine hydrochloride solution, nano silica dispersion, polyethyleneimine solution, and nano silica dispersion, repeating the process 20 to 100 times to obtain rigid particles coated with a composite membrane; (2) Mixing the rigid particles coated with the composite membrane, silane coupling agent, and film-forming agent, and heating the mixture to obtain modified particles; (3) Mixing the modified particles with resin and curing the mixture to obtain a temporary plugging agent.

7. The method for preparing the temporary plugging agent according to claim 6, characterized in that, The polyallylamine hydrochloride solution has a solubility of 0.1 wt% to 0.5 wt%, a pH value of 9.5 to 10.5, and is dissolved in water; and / or, the polyethyleneimine solution has a concentration of 0.1 wt% to 0.5 wt%, a pH value of 9.5 to 10.5, and is dissolved in water; and / or, the nano-silica dispersion has a nano-silica content of 0.1 wt% to 0.5 wt%, a pH value of 9.5 to 10.5, and is dissolved in water; preferably, the nano-silica has a particle size of 0.1 to 0.5 μm.

8. The preparation method according to claim 6 or 7, characterized in that, The immersion time in step (1) is 5 to 10 minutes each time; and / or the heating temperature in step (2) is 60°C to 90°C; and / or the curing conditions in step (3) include a temperature of 110°C to 150°C and a time of 2 to 6 hours.

9. The preparation method according to claim 8, characterized in that, Step (3) before curing also includes preheating and stirring; preferably, the preheating temperature is 70℃~90℃ and the time is 1~2h; the stirring conditions are a speed of 100~500r / min and a time of 10~60min.

10. A drilling fluid, characterized in that, The drilling fluid includes the temporary plugging agent as described in any one of claims 1 to 5 or the temporary plugging agent prepared by the preparation method described in any one of claims 6 to 9; the content of the temporary plugging agent in the drilling fluid is 3wt% to 8wt%; preferably, the plugging pressure of the sealing layer formed by the drilling fluid is ≥7MPa, and the leakage of the sealing layer is 150 to 260mL.

Images