Self-degradable gel temporary plugging agent as well as preparation method and use method thereof

Abstract

The invention provides a self-degradable gel temporary plugging agent and a preparation method and a use method thereof, and the self-degradable gel temporary plugging agent comprises the following components in percentage by mass: 7-9% of a monomer, 0.3-0.8% of polyethylene glycol diacrylate, 0.1-0.5% of an initiator, 0.2-1.8% of sodium silicate and the balance of water. The temporary plugging agent provided by the invention is in a liquid state before gelling, and is low in viscosity, good in fluidity and easy to pump; when the temporary plugging agent is pumped into a shaft, the temporary plugging agent is crosslinked under the temperature action of a target interval to form elastic gel with relatively high strength; as time goes on, the water-soluble cross-linking agent begins to degrade under the action of the weakly alkaline degradation aid, and the temporary plugging agent is degraded into a linear structure from a previous three-dimensional network structure, so that the viscosity of the temporary plugging agent is reduced, and the temporary plugging agent can flow back automatically. Therefore, the temporary plugging agent provided by the invention is easy to pump and good in gelling performance; and after the operation is finished, the plugging agent can be automatically degraded and can be efficiently used for plugging the shaft.

Description

Technical Field

[0001] The invention belongs to the technical field of gas field exploitation and relates to a self-degradable gel temporary plugging agent and a preparation method and a use method thereof. Background Art

[0002] During the oil and gas production process, the use of the wellbore will cause a series of damages, which requires repair to ensure stable production operations in the later stage. However, when using workover fluid to work over a gas well, the pressure difference will cause leakage to varying degrees, which not only hinders the normal workover operation, but also pollutes the formation. Therefore, how to take effective measures to achieve temporary plugging of the wellbore and successfully return the temporary plugging fluid after the workover operation is completed is of great practical significance.

[0003] For shielding temporary plugging technology, the quality of temporary plugging agents determines the degree of development of the technology. Liquid rubber plugs have gradually developed and been widely used in the past 30 years. The so-called liquid rubber plugs are non-Newtonian fluids that are resistant to heat and pressure and have a certain strength. After reaching the designated position, they are injected into the wellbore during the actual operation, and cross-linked to form temporary plugging. The temporary plugging agent is used to temporarily form gel and jelly in the cracks of the original production layer of the wellbore to prevent external liquid from flowing into the reservoir and causing pollution. The well repair operation is completed within the range of the temperature and pressure resistance of the rubber plug. After the operation is completed, the liquid rubber plug is discharged back to the ground by breaking the gel. CN202210446126.6 discloses a degradable temporary plugging agent for offshore large-loss oil and water well repair and a method of use. The formula uses rigid materials such as degradable fibers and degradable gel particles as temporary plugging agents, and uses the bridging effect of materials of different sizes to seal the blasthole. It is mainly suitable for the sealing of wells with large leakage. CN201410828250.4 discloses a low-damage temporary plugging gel for low-pressure gas well repair and a preparation method, and CN202111035970.1 discloses a pressure-bearing degradable plugging agent for well repair and a preparation method. Both are gel systems, but the formula systems are different. The amphoteric metal ions used in the cross-linking agent of CN201410828250.4 and the hypochlorite used in the gel breaker have low pressure strength. CN202111035970.1 has many types and a complex liquid system. CN202110215770.8 discloses a new type of well killing method and well killing fluid for well repair. The patent first uses an oil pipe to inject fracturing fluid, then mixes the well killing fluid and fine sand and injects it, forming a sealable liquid plug of a certain length in the wellbore, and finally adds a gel breaker to backwash and complete the well, which has poor practicality on site. In addition, the temporary plugging agents currently used generally have problems such as short cross-linking time, difficult to control temporary plugging strength and toughness, and incomplete gel breaking and flowback, resulting in poor operating results and secondary pollution of the reservoir. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a self-degradable gel temporary plugging agent and a preparation method and a use method thereof, thereby solving the technical problems of the temporary plugging agent in the prior art, such as short cross-linking time, difficulty in controlling temporary plugging strength and toughness, incomplete gel breaking and flowback, poor operation effect and secondary pollution of the reservoir.

[0005] The present invention is achieved through the following technical solutions:

[0006] A self-degradable gel temporary plugging agent comprises, by weight percentage, 7-9% of monomers, 0.3-0.8% of polyethylene glycol diacrylate, 0.1-0.5% of initiator, 0.2-1.8% of sodium silicate, and the balance is water.

[0007] Preferably, based on mass percentage, it contains 8-9% monomer, 0.3-0.5% polyethylene glycol diacrylate, 0.2-0.5% initiator, 1-1.8% sodium silicate, and the balance is water.

[0008] Preferably, the monomer is acrylonitrile or acrylic acid.

[0009] Preferably, the initiator is ammonium persulfate or azobisisobutylamidine hydrochloride.

[0010] Preferably, the self-degradation and hydration starting time of the self-degradation gel temporary plugging agent is 5 to 9 days.

[0011] The method for preparing the self-degradable gel temporary plugging agent comprises mixing monomers, polyethylene glycol diacrylate, initiator and sodium silicate with water according to mass percentage, and stirring the mixture to obtain the self-degradable gel temporary plugging agent.

[0012] The method for using the self-degradable gel temporary plugging agent comprises the following steps:

[0013] S1: injecting polyacrylamide aqueous solution into the wellbore to be repaired;

[0014] S2: injecting the self-degradable gel temporary plugging agent into the wellbore where step S1 is completed, and making the self-degradable gel temporary plugging agent cross-link the reservoir section to achieve temporary plugging, and performing well repair operations;

[0015] S3: After the well repair operation is completed, the self-degradable gel temporary plugging agent self-degrades and hydrates and is discharged back into the wellbore.

[0016] Preferably, it is characterized in that the concentration of the polyacrylamide aqueous solution is 3‰ to 5‰.

[0017] Preferably, it is characterized in that the temperature of the reservoir section is 50-90°C.

[0018] Preferably, it is characterized in that the cross-linking time is 3 to 5 hours.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The present invention discloses a self-degradable gel temporary plugging agent, which comprises 7-9% monomer, 0.3-0.8% polyethylene glycol diacrylate, 0.1-0.5% initiator, 0.2-1.8% sodium silicate, and the balance is water, according to mass percentage. The temporary plugging agent provided by the present invention is in liquid form before gelation, has low viscosity, good fluidity, and is easy to pump; when pumped into the wellbore, the temporary plugging agent undergoes cross-linking under the temperature of the target layer to form an elastic gel with high strength; as time goes by, sodium silicate is used as a degradation aid, and since the degradation aid is weakly alkaline, the water-soluble cross-linking agent begins to degrade under the action of the weakly alkaline degradation aid, and the temporary plugging agent gradually degrades from the previous three-dimensional network structure to a linear structure, resulting in a decrease in the viscosity of the temporary plugging agent, and it can be self-flowing. Therefore, the temporary plugging agent provided by the present invention is easy to pump and has good gelation performance; and after the operation is completed, it can be self-degraded and can be efficiently used in wellbore plugging.

[0021] Furthermore, according to the mass percentage, it contains 8-9% monomer, 0.3-0.5% polyethylene glycol diacrylate, 0.2-0.5% initiator, 1-1.8% sodium silicate, and the balance is water. This component ratio can control the degradation time to 2-4 days, so that it can degrade quickly.

[0022] Furthermore, the monomer is acrylonitrile or acrylic acid, and the monomer can be cross-linked under the action of a cross-linking agent and an initiator to form an elastic gel with relatively high strength.

[0023] Furthermore, the initiator is ammonium persulfate or azobisisobutylamidine hydrochloride, which can effectively initiate free radical polymerization reaction.

[0024] In addition, the present invention also discloses a method for preparing a self-degradable gel temporary plugging agent, which comprises mixing monomers, crosslinking agents, initiators and degradation aids with water according to mass percentages, and stirring them evenly to obtain the self-degradable gel temporary plugging agent. The preparation method is simple and convenient, the process is simple, and it is easy to mass produce.

[0025] At the same time, the present invention also discloses a method for using a self-degradable gel temporary plugging agent, firstly, injecting a polyacrylamide aqueous solution into the wellbore to be repaired, the polyacrylamide aqueous solution is used as a polymer solution and a pre-fluid to achieve the effect of cleaning the wellbore and isolating formation water, then injecting the self-degradable gel temporary plugging agent into the wellbore to complete the above-mentioned wellbore, and making the self-degradable gel temporary plugging agent reach the reservoir section cross-linking to achieve temporary plugging, and perform well repair operations; finally, after the well repair operations are completed, the self-degradable gel temporary plugging agent self-degrades and hydrates, and is discharged back into the wellbore. The temporary plugging agent is in a liquid state before gelation, has low viscosity, good fluidity, and is easy to pump; when pumped into the wellbore, the temporary plugging agent is cross-linked under the temperature of the target layer section to form an elastic gel with high strength; as time goes by, sodium silicate is used as a degradation aid, and because the degradation aid is weakly alkaline, the water-soluble cross-linking agent begins to degrade under the action of the weakly alkaline degradation aid, and the temporary plugging agent gradually degrades from the previous three-dimensional network structure to a linear structure, resulting in a decrease in the viscosity of the temporary plugging agent, so as to achieve self-return.

[0026] Furthermore, the concentration of the polyacrylamide aqueous solution is 3‰ to 5‰, which can allow the monomers to be fully and effectively cross-linked.

[0027] Furthermore, the temperature of the reservoir section is 50-80° C., which allows the monomers to be fully and effectively cross-linked.

[0028] Furthermore, the cross-linking time is 3 to 5 hours, which can allow the monomers to be fully and effectively cross-linked. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a schematic flow diagram of a method for using a self-degradable gel temporary plugging agent in the present invention;

[0031] Figure 2 This is a test diagram of the pressure bearing performance of the self-degradable gel temporary plugging agent in Example 11 of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0033] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0034] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0035] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0036] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0037] The invention provides a self-degradable gel temporary plugging agent, which comprises, by mass percentage, 7-9% of monomers, 0.3-0.8% of polyethylene glycol diacrylate, 0.1-0.5% of initiator, 0.2-1.8% of sodium silicate, and the balance is water.

[0038] In terms of mass percentage, the self-degradable temporary plugging agent provided by the present invention includes 0.3-0.8% of a crosslinking agent, preferably 0.3-0.5%. In the present invention, the crosslinking agent is polyethylene glycol diacrylate, preferably polyethylene glycol (200) diacrylate. The present invention has no special requirements on the source of the crosslinking agent, and commercially available products known to those skilled in the art can be used.

[0039] In terms of mass percentage, the self-degradable temporary plugging agent provided by the present invention includes 0.1-0.5% of an initiator, preferably 0.2-0.5%. In the present invention, the initiator is ammonium persulfate or azobisisobutylamidine hydrochloride, and the initiator is preferably ammonium persulfate. The present invention has no special requirements on the source of the initiator, and commercially available products known to those skilled in the art can be used.

[0040] In terms of mass percentage, the self-degradable temporary plugging agent provided by the present invention comprises 0.2-1.8%, preferably 1-1.8% of a degradation aid. In the present invention, the degradation aid is sodium silicate; in an embodiment of the present invention, the degradation aid is sodium silicate.

[0041] The self-degradable temporary plugging agent provided by the present invention also includes a water balance. The present invention has no special requirements for the water, and water well known to those skilled in the art can be used.

[0042] The self-degradation and hydration starting time of the self-degradation gel temporary plugging agent is 5 to 9 days.

[0043] The temporary plugging agent provided by the present invention is in liquid form before gelation, has low viscosity, good fluidity, and is easy to pump; when pumped into the wellbore, the temporary plugging agent cross-links in the target layer under the action of temperature and time to form an elastic gel with high strength; as time goes by, the water-soluble cross-linking agent begins to degrade under the action of the weak alkaline degradation aid, and the temporary plugging agent gradually degrades from the previous three-dimensional network structure to a linear structure, resulting in a decrease in the viscosity of the temporary plugging agent. Therefore, the temporary plugging agent provided by the present invention is easy to pump and has good gelation performance; and after the operation is completed, it can be self-degraded and can be efficiently used in wellbore plugging.

[0044] At the same time, the present invention also discloses a method for preparing the above-mentioned self-degradable gel temporary plugging agent, specifically, mixing monomers, cross-linking agents, initiators and degradation aids with water according to mass percentage, and stirring evenly to obtain the self-degradable gel temporary plugging agent. The present invention has no special requirements for the order of adding the monomers, cross-linking agents, initiators, and degradation aids, and they can be added in any order. The present invention has no special requirements for the mixing method, and it is sufficient to ensure that the components are fully mixed. The preparation method of the self-degradable temporary plugging agent provided by the present invention is simple in process, easy to operate, and convenient for large-scale production.

[0045] The present invention also provides the use of the self-degradable temporary plugging agent of the above technical solution or the self-degradable temporary plugging agent prepared by the preparation method of the above technical solution in wellbore plugging, and the application method comprises the following steps: before the temporary plugging agent is pumped into the wellbore, a section of polymer solution is first injected as a pre-fluid to achieve the effect of cleaning the wellbore and isolating formation water, and then the temporary plugging agent is injected into the wellbore, and the temporary plugging agent is displaced to the reservoir section by using the polymer solution, and the temporary plugging agent is cross-linked in the target layer section under the action of time and temperature; after the construction is completed, the temporary plugging agent self-degrades and hydrates and is discharged back into the wellbore.

[0046] Specifically, Figure 1 As shown, the present invention also discloses a method for using the above-mentioned self-degradable gel temporary plugging agent, comprising the following steps:

[0047] S1: injecting a polyacrylamide aqueous solution into the wellbore to be repaired; wherein the concentration of the polyacrylamide aqueous solution is 3‰ to 5‰.

[0048] S2: injecting the self-degradable gel temporary plugging agent into the wellbore where step S1 is completed, and making the self-degradable gel temporary plugging agent cross-link the reservoir section to achieve temporary plugging, and performing well repair operations;

[0049] The temperature of the reservoir section is 50-90° C., and the cross-linking time is 3-5 hours.

[0050] S3: After the well repair operation is completed, the self-degradable gel temporary plugging agent self-degrades and hydrates and is discharged back into the wellbore.

[0051] The temporary plugging agent provided by the present invention is in liquid form before gelation, has low viscosity, good fluidity, and is easy to pump; when pumped into the wellbore, the temporary plugging agent is cross-linked in the target layer under the action of temperature and time to form an elastic gel with high strength; as time goes by, the water-soluble cross-linking agent begins to degrade under the action of the weak alkaline degradation aid, and the temporary plugging agent gradually degrades from the previous three-dimensional network structure to a linear structure, resulting in a decrease in the viscosity of the temporary plugging agent. Therefore, the temporary plugging agent provided by the present invention is easy to pump and has good gelation performance; and after the operation is completed, it can be self-degraded and can be efficiently used in wellbore plugging. The results show that the temporary plugging agent provided by the present invention cross-links to form a plug in 3 to 5 hours, the gelation time is reasonable, the gel can withstand a pressure difference of more than 19MPa, and the gel strength can be maintained for 5 to 9 days, that is, it does not break the gel for 5 to 9 days, and the gelation performance is good; after the construction is completed, the temporary plugging agent can automatically degrade and hydrate in 2 to 3 days.

[0052] The present invention discloses a self-degradable gel temporary plugging agent for oil and gas well operation. The temporary plugging of the well using the self-degradable gel temporary plugging agent can solve the problems of serious low-pressure leakage and large high-pressure blowback during the operation of oil and gas wells. It can be used in the early wellbore treatment process such as side drilling, old well measures and overhaul operations. At the same time, the invention has a simple construction process, a small amount of applied materials, and has commercial value for large-scale promotion.

[0053] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0054] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0055] In various examples, the temporary plugging agent was reacted in a 60° C. water bath to simulate the cross-linking of the temporary plugging agent at the reservoir temperature.

[0056] Example 1

[0057] A degradable temporary plugging agent, the preparation method is as follows: 40g acrylonitrile, 2.5g polyethylene glycol (200) diacrylate, 1.5g ammonium persulfate, and 1g of degradation aid are weighed in sequence. 500mL of temporary plugging agent solution is prepared and placed in a blue-capped bottle; the obtained temporary plugging agent is a liquid aqueous solution, and its viscosity and density are basically the same as those of water, so it is easy to pump;

[0058] The temporary plugging agent solution is reacted in a 60° C. water bath to obtain a gelled temporary plugging agent product. The properties of the temporary plugging agent are shown in Table 1.

[0059] Example 2

[0060] The difference from Example 1 is that the amount of the degradation aid added is 3 g, and the temporary plugging agent solution is reacted in a 60° C. water bath to obtain a gelled temporary plugging agent product. The properties of the temporary plugging agent are shown in Table 1.

[0061] Example 3

[0062] The difference from Example 1 is that the amount of the degradation aid added is 5 g, and the temporary plugging agent solution is reacted in a 60° C. water bath to obtain a gelled temporary plugging agent product. The properties of the temporary plugging agent are shown in Table 1.

[0063] Example 4

[0064] The difference from Example 1 is that the amount of the degradation agent added is 7 g, and the temporary plugging agent solution is reacted in a 60° C. water bath to obtain a gelled temporary plugging agent product. The properties of the temporary plugging agent are shown in Table 1.

[0065] Example 5

[0066] The difference from Example 1 is that the amount of the degradation agent added is 9 g, and the temporary plugging agent solution is reacted in a 60° C. water bath to obtain a gelled temporary plugging agent product. The properties of the temporary plugging agent are shown in Table 1.

[0067] Table 1 Effect of different amounts of degradation aids on the performance of temporary plugging agents

[0068]

[0069] As shown in Table 1, the addition amount of different degradation aids has a great influence on the degradation time of the temporary plugging agent, but has little effect on the gelation time and the final degradation viscosity, both of which gel in about 3 hours. With the increase of the addition amount of degradation aids, the initial degradation time of the temporary plugging agent is gradually shortened, but the strength can be maintained above 8 days. Finally, it is completely degraded at 10 to 14 days, and the viscosity of the temporary plugging agent return fluid after degradation is very low, all lower than 15 mPa·s, which is easy to return.

[0070] Example 6

[0071] A degradable temporary plugging agent, the preparation method is as follows: 35g acrylic acid, 1.5g polyethylene glycol (200) diacrylate, 0.5g ammonium persulfate, 5g sodium silicate are weighed in sequence, added into 454mL tap water, stirred to prepare a temporary plugging agent solution, the temporary plugging agent solution is placed in a 50°C water bath to react, and a gelled temporary plugging agent product is obtained, and the performance of the self-degradable temporary plugging agent is tested. The results are shown in Table 2.

[0072] Example 7

[0073] The difference from Example 6 is that the temporary plugging agent solution is placed in a 60° C. water bath to react and obtain a gelled temporary plugging agent product. The performance test of the temporary plugging agent is shown in Table 2.

[0074] Example 8

[0075] The difference from Example 6 is that the temporary plugging agent solution is placed in a 70° C. water bath to react and obtain a gelled temporary plugging agent product. The performance test of the temporary plugging agent is shown in Table 2.

[0076] Example 9

[0077] The difference from Example 6 is that the temporary plugging agent solution is placed in a water bath at 80° C. to react to obtain a gelled temporary plugging agent product. The performance test of the temporary plugging agent is shown in Table 2.

[0078] Example 10

[0079] The difference from Example 6 is that the temporary plugging agent solution is placed in a 90° C. water bath to react and obtain a gelled temporary plugging agent product. The performance test of the temporary plugging agent is shown in Table 2.

[0080] Table 2 Effect of different temperatures on the performance of self-degradable temporary plugging agent

[0081]

[0082] As shown in Table 2, the gelling time of temporary plugging agents at different temperatures is stable within 3 to 5 hours, and the strength after gelling is maintained for more than 5 days. As the temperature increases, the final degradation time of the temporary plugging agent is shortened, but the final degradation supervision is lower than 15mPa·s, indicating that the performance of the temporary plugging agent remains good at different temperatures.

[0083] Embodiment 11

[0084] A degradable temporary plugging agent is prepared as follows: 45g acrylic acid, 4g polyethylene glycol (200) diacrylate, 2.5g ammonium persulfate, and 3g sodium silicate are weighed in sequence and added into 445.5mL tap water to prepare a temporary plugging agent solution, which is injected into a core with a permeability of 101.6mD at a rate of 0.5mL / min, and then the core holder carrying the core is placed in a 60°C oven to wait for it to gel. After gelation, the pressure bearing performance of the self-degradable gel temporary plugging agent is tested by reverse injection method using gas drive. The experimental results are as follows: Figure 2 As shown by Figure 2 It can be seen that the self-degradable temporary plugging agent can withstand a maximum pressure of about 19 MPa after gelation, indicating that the self-degradable temporary plugging agent developed has good pressure resistance, and the curve has only one breakthrough point, indicating that the gas breaks through by penetrating the gel rather than through the gap between the gel and the inner wall of the core holder, indicating that the temporary plugging agent has a high degree of adhesion to the barrel wall.

[0085] Example 13

[0086] A degradable temporary plugging agent, the preparation method is as follows: 35g acrylic acid, 1.5g polyethylene glycol (200) diacrylate, 0.5g ammonium persulfate, 5g sodium silicate are weighed in sequence, added to 454mL tap water, stirred evenly, and placed in cores with different permeabilities. Before injection, the water permeability of different cores is tested by displacement, and the temporary plugging agent is gelled and degraded in the core and then discharged, and then the water permeability is tested again. The damage rate of the temporary plugging agent to the core is calculated by comparing the permeability of the core before and after temporary plugging. The experimental results are shown in Table 3:

[0087] Table 3 Core damage test before and after temporary plugging under different core conditions

[0088]

[0089]

[0090] It can be seen from Table 3 that the self-degradable gel temporary plugging agent has little damage to the cores at different permeabilities after degradation, all less than 8%, indicating that the prepared gel self-degradable temporary plugging agent can protect the reservoir well on the one hand and reduce pollution to the environment on the other hand during actual operation.

[0091] It can be seen from the above examples that the temporary plugging agent provided by the present invention is in liquid form before gelling, has low viscosity, good fluidity, and is easy to pump; it has good gelling performance and can be self-degraded.

[0092] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A self-degradable gel temporary plugging agent, characterized in that: According to mass percentage, it contains 7-9% monomer, 0.3-0.8% polyethylene glycol diacrylate, 0.1-0.5% initiator, 0.2-1.8% sodium silicate, and the balance is water.

2. A self-degradable gel temporary plugging agent according to claim 1, characterized in that: According to mass percentage, it contains 8-9% of monomers, 0.3-0.5% of polyethylene glycol diacrylate, 0.2-0.5% of initiator, 1-1.8% of sodium silicate, and the balance is water.

3. A self-degradable gel temporary plugging agent according to claim 1, characterized in that: The monomer is acrylonitrile or acrylic acid.

4. A self-degradable gel temporary plugging agent according to claim 1, characterized in that: The initiator is ammonium persulfate or azobisisobutylamidine hydrochloride.

5. The self-degradable gel temporary plugging agent according to claim 1, characterized in that: The self-degradation and hydration starting time of the self-degradation gel temporary plugging agent is 5 to 9 days.

6. The method for preparing a self-degradable gel temporary plugging agent according to any one of claims 1 to 5, characterized in that: The monomer, polyethylene glycol diacrylate, initiator and sodium silicate are mixed with water according to mass percentage and stirred evenly to obtain the self-degradable gel temporary plugging agent.

7. A method for using a self-degradable gel temporary plugging agent according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: injecting polyacrylamide aqueous solution into the wellbore to be repaired; S2: injecting the self-degradable gel temporary plugging agent into the wellbore where step S1 is completed, and making the self-degradable gel temporary plugging agent cross-link the reservoir section to achieve temporary plugging, and performing well repair operations; S3: After the well repair operation is completed, the self-degradable gel temporary plugging agent self-degrades and hydrates and is discharged back into the wellbore.

8. The method for using the self-degradable gel temporary plugging agent according to claim 7, characterized in that: The concentration of the polyacrylamide aqueous solution is 3‰ to 5‰.

9. The method for using a self-degradable gel temporary plugging agent according to claim 7, characterized in that: The temperature of the reservoir section is 50-90°C.

10. The method for using a self-degradable gel temporary plugging agent according to claim 7, characterized in that: The cross-linking time is 3 to 5 hours.

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