Temporary plugging agent for fracturing, preparation method and application

Abstract

The application discloses a temporary plugging agent for fracturing, a preparation method and application, belongs to the technical field of oil field chemistry, and provides a temporary plugging agent for fracturing, a preparation method and application. The temporary plugging agent is constructed by using an acrylic blend and plant fibers to obtain a plant fiber reinforced double-network structure, and is endowed with an acid response synergistic degradation mechanism, overcomes the contradiction between high-temperature stability, plugging strength and plugging removal efficiency of the existing temporary plugging agent, and provides a temporary plugging agent which can maintain stable plugging in a 200 DEG C high-temperature environment, has a pressure-bearing capacity of more than 50 MPa, and can actively trigger plugging removal according to construction requirements, and provides technical support for further development of the temporary plugging agent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemistry, and more particularly to a temporary plugging agent for fracturing, a preparation method and application. BACKGROUND

[0002] With the development of oil and gas exploration and development to the deep and ultra-deep field, the temporary plugging fracturing technology has become a key means to improve the reservoir reconstruction effect. The technology blocks the formed fractures or high permeability channels through temporary plugging agent, forcing the fracturing fluid to divert to the area not fully reconstructed, thereby improving the reservoir producing degree. However, the existing temporary plugging agent has obvious technical bottlenecks in high temperature environment:

[0003] Insufficient high temperature resistance: conventional high molecular temporary plugging agent degrades or softens when the temperature exceeds 160℃, such as polyglycolic acid-based material, which reduces the compressive strength by more than 30% at 180℃, resulting in plugging failure.

[0004] Contradiction between plugging strength and deblocking efficiency: high-strength metal alloy temporary plugging agent (such as magnesium-aluminum alloy) can withstand 30MPa pressure, but needs strong acid to deblock and the residue rate is 10-15%, which seriously damages the reservoir; and the easily deblocked water-soluble polymer (such as starch / acrylic acid copolymer) has insufficient pressure-bearing capacity (<15MPa) and is difficult to plug wide cracks.

[0005] Insufficient deblocking controllability: the existing degradable temporary plugging agent has degradation behavior controlled by a single factor of temperature, which cannot accurately control the deblocking time according to the construction requirements, affecting the stimulation effect.

[0006] In view of the above problems, the existing technology focuses on material modification: the knot type temporary plugging agent developed by China Petroleum adopts a core-sheath structure design, and the temperature resistance is improved to 180℃, but its degradation rate is still dominated by temperature and cannot be actively controlled; the fully degradable temporary plugging agent of Southwest Petroleum Engineering Company has a temporary plugging efficiency of more than 80%, but it has insufficient stability in a 200℃ ultra-high temperature environment; and the intelligent controllable temporary plugging agent developed by China Petroleum can control the gel breaking time, but the plugging strength still cannot meet the requirements of ultra-deep wells.

[0007] Therefore, it is urgent to develop a new type of temporary plugging agent with ultra-high temperature stability, high pressure-bearing strength and precise controllable deblocking characteristics to meet the efficient development needs of deep unconventional oil and gas resources, which is a technical problem to be solved by the technical personnel in the field. SUMMARY

[0008] Therefore, the present application provides a temporary plugging agent for fracturing, a preparation method and application, which improves the high temperature stability of the temporary plugging agent, overcomes the contradiction between the plugging strength and the deblocking efficiency, and provides a temporary plugging agent that can maintain stable plugging in a 200℃ high temperature environment, has a pressure-bearing capacity of more than 50MPa, and can actively trigger deblocking according to the construction requirements.

[0009] Secondly, a method for preparing the temporary plugging agent is provided, which solves the compatibility problem between high-temperature deformation and controllable degradation through a dual-network gel construction and acid-responsive material composite process.

[0010] Third, it provides the application of this temporary plugging agent in oil and gas well fracturing to achieve precise temporary plugging of fractures and low-residue unblocking.

[0011] To solve the above-mentioned technical problems, this application adopts the following technical solution:

[0012] A temporary plugging agent for fracturing comprises the following components by weight percentage: 25-40% acrylic polymer, 8-15% plant fiber, 20-30% acid-responsive inorganic filler, 3-8% slow-release breaker, 2-5% heat stabilizer, 0.5-1.5% crosslinking agent, and 0.1-0.3% initiator, with the balance being water to make up 100%.

[0013] As a preferred technical solution, the acrylic polymer is composed of acrylamide and acrylic acid in a mass ratio of 4:6 to 5:5; under the action of the crosslinking agent, the acrylic polymer forms a three-dimensional crosslinked skeleton, giving the material high elasticity and deformation recovery ability.

[0014] The plant fiber is sisal fiber and / or bamboo fiber that has been treated with alkali.

[0015] The acid-responsive inorganic filler is a magnesium hydroxide and zinc oxide composite material; the acid-responsive inorganic filler is acid-soluble: the magnesium hydroxide / zinc oxide composite particles dissolve rapidly in acid (pH≤4.5) (reaction formula: Mg(OH)₂ + 2H₂O) + → Mg 2+ (+2H2O) forms microchannels inside the material, enabling acid-responsive unblocking;

[0016] The slow-release breaker is a silver-1,4-dicyanobenzene complex; the slow-release breaker releases silver ions within a certain time, catalyzing the oxidative degradation of the polymer blend, thus achieving time-controlled breaker breaking.

[0017] The heat stabilizer is hydrophobic fumed silica, which improves thermal stability;

[0018] The crosslinking agent is N,N'-methylenebisacrylamide, and the acrylic polymer forms a chemical crosslinking network through the crosslinking agent to strengthen the network crosslinking.

[0019] The initiator is ammonium persulfate.

[0020] The formulation described in this application successfully constructs a temporary plugging agent with a plant fiber-reinforced dual-network structure and an acid-responsive synergistic deblocking mechanism, as detailed below:

[0021] Plant fiber reinforced dual network structure:

[0022] Primary network: chemical crosslinking network of acrylic polymer formed by crosslinking agent, providing basic elasticity;

[0023] Secondary network: hydroxyl and carboxyl on the surface of plant fiber after alkali treatment are connected with polymer molecular chain through hydrogen bond and chemical bond to form physical crosslinking point. At high temperature (> 150℃), the plant fiber is gelatinized and hardened, effectively inhibiting excessive hydration of the gel and maintaining structural strength.

[0024] Acid-responsive synergistic plugging mechanism:

[0025] Acid-soluble filler: magnesium hydroxide / zinc oxide composite particles dissolve quickly in the presence of acid, forming microchannels inside the material;

[0026] Polymer network acid hydrolysis: hydrogen ion catalyzes amide group hydrolysis and chain scission, with a degradation rate higher than that under neutral conditions;

[0027] Slow-release gel breaker trigger: slow-release gel breaker releases silver ions over time, catalyzing oxidative degradation of the polymer and achieving "time-chemical" dual-regulation plugging.

[0028] As a preferred technical solution, the fiber length of the plant fiber is 0.5-2mm, and the aspect ratio is ≥20:1.

[0029] As a preferred technical solution, the particle size distribution of the magnesium hydroxide and zinc oxide composite is 1-10μm.

[0030] The molar mass ratio of silver ions to 1,4-dicyanobenzene in the slow-release gel breaker is 1:1.5-2.5.

[0031] Still another object of the present application is to provide a preparation method of the temporary plugging agent for fracturing, comprising the following steps:

[0032] (1) Plant fiber pretreatment: cut the plant fiber to a length of 1-2mm, immerse it in an 8-12wt% NaOH solution, and treat it at 85-95℃ for 1.5-2.5 hours. After washing to neutral, dry to obtain pretreated plant fiber; the plant fiber is alkali-treated sisal fiber and / or bamboo fiber; the plant fiber is pretreated under high temperature and high concentration of alkali (severe conditions), which has the following effects:

[0033] Increase the reactivity of the fiber surface: break the natural wax / hemicellulose barrier, exposing more hydroxyl (-OH) and carboxyl (-COOH);

[0034] Enhance fiber-polymer interface bonding: fiber surface -COOH forms amide bond (-CONH-) with polymer amide group; exposed -OH forms hydrogen bond network with polymer carboxyl group; stable double network structure is constructed through chemical bond and hydrogen bond;

[0035] Inhibit high temperature creep: high temperature and high concentration alkali treatment for a long time, induce the formation of cellulose "alkali cellulose" (cellulose II crystal form), or by dissolving amorphous impurities and rearranging cellulose chains, increase the crystallinity, make the fiber paste harden at high temperature instead of degradation, inhibit the deformation of polymer network at high temperature;

[0036] (2) Slow-release breaker preparation: mix silver nitrate and 1,4-dicyanobenzene in ethanol according to the molar mass ratio, react at 45-55℃ for 3-6 hours, generate silver-1,4-dicyanobenzene complex precipitate, filter, dry and crush to 180-220 mesh to prepare slow-release breaker;

[0037] (3) Mix acrylic polymer, water and pretreated plant fiber, add crosslinking agent and initiator for polymerization reaction to prepare gel;

[0038] (4) Mix the gel after crushing with acid-responsive inorganic filler, slow-release breaker and heat stabilizer uniformly;

[0039] (5) Extrude and granulate the mixture under deep cooling.

[0040] As a preferred technical solution, the polymerization reaction in step (3) is carried out at 55-65℃ for 3h.

[0041] As a preferred technical solution, the deep cooling extrusion in step (5) is carried out at-40℃ to-60℃, and the screw length-diameter ratio is 12-18:1.

[0042] Still another purpose of the present application is to provide the application of the temporary plugging agent for fracturing or the temporary plugging agent prepared by the above method in oil and gas well fracturing.

[0043] As a preferred technical solution, the temporary plugging agent is added to the fracturing fluid at a concentration of 0.5-3wt%, and pumped to the target layer to form temporary plugging; when unblocking, an acidic solution with pH=3.5-5.0 is injected or the unblocking is automatically triggered by the slow-release breaker.

[0044] As a preferred technical solution, the acidic solution is formic acid, acetic acid and / or citric acid solution.

[0045] Through the above technical solution, compared with the prior art, the present application has the following beneficial effects: the present application provides a temporary plugging agent for fracturing, which has:

[0046] Super-high temperature stability: the synergistic effect of double network structure and heat stabilizer makes the temporary plugging agent maintain structural integrity at 200℃, and the compressive strength is ≥50MPa, breaking through the temperature resistance limit of existing temporary plugging agents;

[0047] Precise controllable plugging removal: through acid injection or slow-release breaker timed triggering, controllable plugging removal is realized, and the residue rate after plugging removal is less than or equal to 1%, which is much lower than that of metal alloy temporary plugging agent (>10%);

[0048] Small reservoir damage: all-organic-inorganic composite design, the degradation product is water-soluble small molecule (acrylic acid oligomer, magnesium ion, etc.), and there is no solid residue remaining in the reservoir.

[0049] Reduced construction cost: plugging does not require special setting tools, and can be pumped and put in, saving operation cost. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0051] The magnesium hydroxide / zinc oxide composite in the embodiments of the present application is prepared by the following method:

[0052] (1) Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and zinc nitrate (Zn(NO3)2) are dissolved in deionized water according to Mg:Zn=3:1 (molar ratio) to prepare a mixed salt solution with a concentration of 1.0 mol / L;

[0053] (2) Precipitating agent: sodium hydroxide and ammonia water are mixed according to a volume ratio of 1:1 (total concentration 2 mol / L);

[0054] (3) The precipitating agent is added dropwise to the mixed salt solution until the pH is pH=10-11, and then stirred uniformly at 50°C, and then aged at 70°C for 2h, washed by centrifugation until neutral, and then vacuum dried at 80°C, ground and sieved to prepare the magnesium hydroxide / zinc oxide composite (1-10μm).

[0055] Example 1

[0056] Acrylamide: 14%;

[0057] Acrylic acid: 21%;

[0058] Alkali-treated sisal fiber: 10%;

[0059] Magnesium hydroxide / zinc oxide composite: 25%;

[0060] Silver-1,4-dicyanobenzene complex: 5%;

[0061] Hydrophobic fumed silica: 4%;

[0062] N,N'-methylenebisacrylamide: 0.5%;

[0063] Ammonium persulfate: 0.1%;

[0064] Deionized water: balance.

[0065] (1) Sisal fiber pretreatment: Sisal fibers (fiber length 1 mm, aspect ratio ≥ 20:1) were cut to 1-2 mm in length, immersed in a 10 wt% NaOH solution, treated at 90°C for 2 hours, washed to neutral, and dried to prepare pretreated sisal fibers;

[0066] (2) Slow-release breaker preparation: Silver nitrate and 1,4-dicyanobenzene were mixed in ethanol at a molar mass ratio of silver ion to 1,4-dicyanobenzene of 1:2, and reacted at 50°C for 4 hours to generate a silver-1,4-dicyanobenzene complex precipitate, which was filtered, dried, and pulverized to 200 mesh to prepare a silver-1,4-dicyanobenzene complex;

[0067] (3) The acrylic polymer, water, and pretreated sisal fibers were mixed, N,N'-methylenebisacrylamide was added, and the temperature was raised to 60°C, then ammonium persulfate was added, and the mixture was reacted at 60°C for 3 hours to prepare a gel block, which was mechanically broken into 5 mm particles;

[0068] (4) The broken gel was mixed with magnesium hydroxide / zinc oxide composite (5 μm), silver-1,4-dicyanobenzene complex, and hydrophobic fumed silica in a high-speed mixer at 800 rpm for 15 minutes;

[0069] (5) The mixture was granulated by a twin-screw extruder (-50°C deep cooling environment), and 0.8-1.2 mm particles were sieved out. Example 2

[0070] Acrylamide: 12.5%;

[0071] Acrylic acid: 12.5%;

[0072] Alkali-treated bamboo fibers: 8%;

[0073] Magnesium hydroxide / zinc oxide composite: 20%;

[0074] Silver-1,4-dicyanobenzene complex: 3%;

[0075] Hydrophobic fumed silica: 2%;

[0076] N,N'-methylenebisacrylamide: 0.5%;

[0077] Ammonium persulfate: 0.1%;

[0078] Deionized water: balance.

[0079] (1) Bamboo fiber pretreatment: Bamboo fibers (fiber length 0.5 mm, aspect ratio ≥ 20:1) were cut to 1-2 mm in length, immersed in an 8 wt% NaOH solution, treated at 85°C for 1.5 hours, washed to neutral, and dried to prepare pretreated bamboo fibers;

[0080] (2) Slow-release breaker preparation: Silver nitrate and 1,4-dicyanobenzene were mixed in ethanol at a molar mass ratio of silver ions to 1,4-dicyanobenzene of 1:1.5, and reacted at 45°C for 3 hours to form a silver-1,4-dicyanobenzene complex precipitate, which was filtered, dried, and pulverized to 180 mesh to prepare a silver-1,4-dicyanobenzene complex;

[0081] (3) The acrylic polymer, water, and pretreated bamboo fibers were mixed, N,N'-methylenebisacrylamide was added, and the temperature was raised to 60°C, then ammonium persulfate was added, and the mixture was reacted at 60°C for 3 hours to prepare a gel block, which was mechanically broken into 5 mm particles;

[0082] (4) The broken gel was mixed with magnesium hydroxide / zinc oxide composite (2 μm), silver-1,4-dicyanobenzene complex, and hydrophobic fumed silica in a high-speed mixer at 800 rpm for 15 minutes;

[0083] (5) The mixture was granulated by a twin-screw extruder (-40°C deep cooling environment), and 0.8-1.2 mm particles were sieved out. Example 3

[0084] Acrylamide: 20%;

[0085] Acrylic acid: 20%;

[0086] Alkali-treated sisal fibers: 15%;

[0087] Magnesium hydroxide / zinc oxide composite: 25%;

[0088] Silver-1,4-dicyanobenzene complex: 8%;

[0089] Hydrophobic fumed silica: 5%;

[0090] N,N'-methylenebisacrylamide: 1.5%;

[0091] Ammonium persulfate: 0.3%;

[0092] Deionized water: balance.

[0093] (1) Sisal fiber pretreatment: Sisal fibers (fiber length 2 mm, aspect ratio ≥ 20:1) were cut to 1-2 mm in length, immersed in a 12 wt% NaOH solution, treated at 95°C for 2.5 hours, washed to neutral, and dried to prepare pretreated sisal fibers;

[0094] (2) Preparation of slow-release gel breaker: silver nitrate and 1,4-dicyanobenzene were mixed in ethanol at a molar mass ratio of silver ion to 1,4-dicyanobenzene of 1:2.5, and reacted at 55°C for 6 hours to form a silver-1,4-dicyanobenzene complex precipitate, which was filtered, dried, and crushed to 220 mesh to prepare the silver-1,4-dicyanobenzene complex;

[0095] (3) The acrylic polymer, water, and pretreated sisal fibers were mixed, N,N'-methylenebisacrylamide was added, and the temperature was raised to 60°C, then ammonium persulfate was added, and the mixture was reacted at 60°C for 3 hours to prepare a gel block, which was mechanically broken into 5mm particles;

[0096] (4) The gel after breaking was mixed with magnesium hydroxide / zinc oxide complex (10μm), silver-1,4-dicyanobenzene complex, and hydrophobic fumed silica in a high-speed mixer at 800rpm for 15 minutes;

[0097] (5) The mixture was granulated by a twin-screw extruder (-60°C deep cooling environment), and 0.8-1.2mm particles were sieved out.

[0098] Comparative Example 1

[0099] The scheme was basically the same as that of Example 1, except that the sisal fibers were not pretreated, and the rest of the operations were the same as those of Example 1.

[0100] In order to study the effect of the plant fiber pretreatment operation of the present application, Comparative Example 1 was set for Example 1, and the difference between the two was that one was pretreated and the other was not pretreated. The surface morphology, specific surface area, and functional group density of the plant fibers of Example 1 (pretreated fiber) and Comparative Example 1 (untreated fiber) were measured, and the experimental results are shown in Table 1.

[0101] Table 1 Surface activation degree of plant fibers in different groups

[0102]

[0103] Result analysis: As can be seen from the content of Table 1, the surface of the plant fiber treated by alkali is fully activated, and the specific surface area, -OH, and -COOH functional group density are all improved, which provides a basis for the construction of plant fiber reinforced double network structure in the later stage.

[0104] The crystallinity of Example 1 and Comparative Example 1 was further measured, and the experimental results are shown in Table 2.

[0105] Table 2 Crystallinity and cellulose type of different groups

[0106]

[0107] Result analysis: crystallinity regulation (XRD verification), untreated sisal fiber: crystallinity of 63% (cellulose type I).

[0108] Example 1 after alkali treatment: crystallinity increased to 82% (all cellulose I type converted to high crystallinity cellulose II type), and high crystallinity cellulose pasted hardening (not melting) at > 150°C, inhibiting polymer network deformation at high temperature.

[0109] Performance test

[0110] (1) High temperature pressure test:

[0111] The temporary plugging agent for fracturing prepared from examples 1-3 and comparative example 1 was filled into a simulated fracture device (slit width 2 mm) to determine its temperature resistance and pressure bearing capacity, and the experimental results are shown in Table 3.

[0112] Table 3 Temperature resistance and pressure bearing capacity of temporary plugging agents in different groups

[0113]

[0114] Results: The temperature resistance and pressure bearing capacity of examples 1-3 are obviously better than those of comparative example 1. The reason is that the crystallinity of untreated cellulose is low, the cellulose type is mainly natural fiber type I, the adsorption mode of fiber and polymer is mainly physical adsorption, high temperature will cause thermal degradation, resulting in poor temperature resistance and weak pressure bearing capacity.

[0115] (2) Controllable plugging removal test:

[0116] The plugging removal time of examples 1-3 and comparative example 1 was determined under conditions 1 and 2, respectively, and the specific conditions are as follows:

[0117] Condition 1: Injecting a pH = 4.0 formic acid solution, and recording the complete plugging removal time;

[0118] Condition 2: Under the condition of no acid, test the plugging removal time triggered by the slow-release breaker.

[0119] The experimental results are shown in Table 4.

[0120] Table 4 Plugging removal time and residue rate under different conditions for different groups

[0121]

[0122] Result analysis: Compared with comparative example 1, the acid-triggered plugging removal time of comparative example 1 is significantly prolonged. The reason is that the -COOH density of alkali-treated fiber is high, and in an acidic environment:

[0123] Protonation shrinkage (-COO-→-COOH) triggers network disintegration;

[0124] acid-responsive packing material Synergistically accelerate channel formation.

[0125] Non-alkali treated fibers lack -COOH, mainly rely on packing material dissolution, and the plug removal time should be significantly extended.

[0126] (3) Field test:

[0127] In the application of deep shale gas wells in southern Sichuan (well depth 4500m, temperature 195℃), 350kg of temporary plugging agent of Example 1 was pumped to plug the fractured cracks, and the construction pressure was increased from 45MPa to 68MPa, indicating effective diversion. After well completion, acidic plug removal fluid (pH=4.2) was injected, and after 6 hours, the flowback was restored, and the production was increased by 2.1 times compared with the state without fracturing.

[0128] Each of the embodiments in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0129] The above description of the disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A temporary plugging agent for fracturing, characterized by, The components include the following weight percentages: acrylic polymer monomer 25-40%, plant fiber 8-15%, acid-responsive inorganic filler 20-30%, slow-release breaker 3-8%, thermal stabilizer 2-5%, crosslinking agent 0.5-1.5%, and initiator 0.1-0.3%, with the balance being water to make up 100%; The acrylic polymer monomer is acrylamide and acrylic acid in a mass ratio of 4:6-5:5; The plant fiber has a fiber length of 0.5-2 mm and an aspect ratio of ≥20:1; The plant fiber is pretreated sisal fiber and / or bamboo fiber, and the pretreatment process is as follows: the plant fiber is cut to a length of 1-2 mm, immersed in an 8-12 wt% NaOH solution, treated at 85-95°C for 1.5-2.5 hours, washed to neutral, and then dried; The acid-responsive inorganic filler is a magnesium hydroxide and zinc oxide composite; The slow-release breaker is a silver-1,4-dicyanobenzene complex, with a molar mass ratio of silver ions to 1,4-dicyanobenzene of 1:1.5-2.5; The thermal stabilizer is hydrophobic fumed silica; The crosslinking agent is N,N'-methylenebisacrylamide; The initiator is ammonium persulfate.

2. The temporary plugging agent for fracturing of claim 1, wherein, The magnesium hydroxide and zinc oxide composite has a particle size distribution of 1-10 μm.

3. The method for preparing the temporary plugging agent for fracturing according to any one of claims 1-2, characterized in that, The method comprises the following steps: (1) Plant fiber pretreatment: the plant fiber is cut to a length of 1-2 mm, immersed in an 8-12 wt% NaOH solution, treated at 85-95°C for 1.5-2.5 hours, washed to neutral, and then dried to obtain pretreated plant fiber; (2) Slow-release breaker preparation: silver nitrate and 1,4-dicyanobenzene are mixed in ethanol at a molar mass ratio, reacted at 45-55°C for 3-6 hours to form a silver-1,4-dicyanobenzene complex precipitate, which is filtered, dried, and crushed to 180-220 mesh to obtain the slow-release breaker; (3) The acrylic polymer monomer, water, and pretreated plant fiber are mixed, and a crosslinking agent and an initiator are added for polymerization to obtain a gel; (4) The gel is crushed and mixed uniformly with acid-responsive inorganic filler, slow-release breaker, and thermal stabilizer; (5) The mixture is extruded and granulated under cryogenic conditions.

4. The method for preparing the temporary plugging agent for fracturing according to claim 3, characterized in that, The polymerization reaction in step (3) is carried out at 55-65°C for 3 hours. The cryogenic extrusion in step (5) is carried out at -40°C to -60°C, with a screw aspect ratio of 12-18:

1.

5. Use of the temporary plugging agent of any one of claims 1-2 or prepared by the method of any one of claims 3-4 in oil and gas well fracturing.

6. Use according to claim 5, characterized in that, The temporary plugging agent is added to the fracturing fluid at a concentration of 0.5-3 wt%, pumped to the target zone to form a temporary plug, and when the plug is broken, an acidic solution with a pH of 3.5-5.0 is injected or the slow-release breaker is used to automatically trigger the plug breaking.

7. Use according to claim 6, characterized in that, The acidic solution is a formic acid, acetic acid, and / or citric acid solution.

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