CN117362524A - Temporary plugging gel containing autocatalytic degradation structure and preparation method thereof - Google Patents

Abstract

The invention discloses a temporary plugging gel containing an autocatalytic degradation structure and a preparation method thereof, belonging to the technical field of oil and gas exploitation, and comprising the following preparation raw materials in percentage by mass: 4-15 parts of main monomer, 0.5-4 parts of functional cross-linking agent, 0.01-0.5 part of built-in degradation catalyst, 2-10 parts of reinforced and toughened monomer, 0.01-0.2 part of initiator and the balance of deionized water. According to the invention, a three-dimensional network structure is formed through chemical crosslinking, because the functional crosslinking agent contains a catalytic degradable chemical bond, weak bonds in the functional crosslinking agent are broken under the action of the built-in catalyst, the three-dimensional network structure disintegrates, and the generated linear low-molecular-weight water-soluble polymer is dissolved in stratum water to form low-viscosity fluid, so that flowback is not needed, and subsequent water injection is not influenced. The invention has the characteristics of low injection viscosity, controllable gel forming time, high blocking strength, low viscosity of degraded products and the like, and completely meets the temporary blocking process requirements of the water injection well suitable for string detection operation.

Description

Temporary plugging gel containing autocatalytic degradation structure and preparation method thereof

Technical Field

The invention belongs to the technical field of oil and gas exploitation, and particularly relates to a temporary plugging gel containing an autocatalytic degradation structure and a preparation method thereof.

Background

Along with the gradual entering of domestic oil fields into the later period of exploitation, the development, overhaul and maintenance operations of oil-gas wells and water injection wells become the primary tasks of various large oil fields, the quality of well repair operations is related to whether the oil fields can normally run and produce, and the quality of well repair operations plays a vital role in the economic benefits of the oil fields. The water injection development mode is generally adopted in the Changqing oilfield, the water injection well is nearly 2 ten thousand at present, more than 1 thousand pressurized water injection wells need to be checked and repaired each year along with the continuous deep development, and the operation demand is large.

The well control and the open flow are taken as two traditional operation modes, and although well repair operation can be completed, the operation period is long, the operation cost is high, and the underground oil-water channel is possibly blocked, so that the oil well yield and the water injection effect are affected. Compared with the traditional well repairing mode, the under-pressure well repairing is an operation technology for lifting and lowering a pipe for injection of an oil well under the conditions of no well killing and pressure relief, and the technology does not change the pressure in the well when the well repairing operation is carried out, so that the improvement of the water injection efficiency of an oil field and the stable production of the oil field are facilitated. For oil and gas wells, the biggest advantage of the well repair operation is that no foreign fluid enters, so that the oil and gas layers and the environment can be protected to the greatest extent; for the water injection well, the pressurized well repairing has the advantages that the pressurized well repairing is operated under the conditions of no blowout and no overflow, so that the energy in the stratum is not released. With further deep development of oil and gas fields, the maintenance frequency of an oil-water well is higher and higher, the requirement on the under-pressure well repairing technology is higher and higher, and the oil-water channel blockage can be caused due to high cost and long time consumption of well killing operation, so that the oil extraction yield and the water injection effect of the oil well can be influenced, and therefore, the development of the well repairing operation plugging technology is needed.

Polymer gels have unique advantages when performing plugging operations. Because the polymer has higher deformability, the polymer cannot be limited by a leakage channel, and after injection, the polymer or monomer solution which is easy to flow can be crosslinked and copolymerized to form non-flowable gel or gel, so that the plugging effect can be generated in an extremely tiny pore canal. The material is liquid before injection, and after injection, the material is converted into solid gel with a three-dimensional network structure under the stratum condition due to the crosslinking effect, so that the material has good plugging property. However, the existing gel-like plugging agent in China is difficult to apply to temporary plugging operation, has the problems of difficult gel breaking, incapability of spontaneous degradation, pollution to a reservoir and the like, and has high site construction difficulty and high risk.

Chinese patent CN113025292 a discloses a high-strength gel temporary plugging agent for plugging horizontal shaft before repairing thermal recovery horizontal well and its preparation method, the plugging agent system is composed of heat-resistant polymer, partially hydrolyzed polyacrylamide, phenolic aldehyde cross-linking agent, chromium cross-linking agent, deoxidizer, organic acid, sodium soil and the balance of water. The temporary plugging agent can be subjected to primary crosslinking at the temperature below 100 ℃ to form weak crosslinking gel solution with certain viscosity, and has pumpability, and meanwhile, the gel solution is prevented from being filtered to the stratum and being diluted by wellbore water. And the high-strength gel rubber plug can be formed by quick crosslinking at the temperature higher than 100 ℃ to seal the shaft, so that the formation hot fluid is prevented from overflowing. However, the use of chromium crosslinkers in the present invention presents a potential environmental risk.

Chinese patent CN201610210924 discloses a steering temporary plugging agent which is composed of a polymer, a surfactant and a cross-linking agent and is suitable for temporary plugging between seams. The temporary plugging agent has the characteristics of simple preparation, good solubility and the like, and the high-strength network formed by the mutual crosslinking between the polyacrylamide and the polyurethane improves the pressure-bearing performance of the temporary plugging agent, but the non-water-soluble polyurethane component and the metal aluminum crosslinking agent are adopted in the patent, so that the temporary plugging agent has certain damage to stratum and does not have a self-degradation function.

Chinese patent CN116103026a discloses a competitive crosslinking type high-density salt-resistant cured water microgel temporary plugging agent and a preparation method thereof, the gel temporary plugging agent is composed of phosphate compound, curing agent, crosslinking agent and the balance of water. The gel temporary plugging agent solves the problem that the density of the gel temporary plugging agent is difficult to be greatly improved through multistage crosslinking. Its maximum density can be up to 1.83g/cm3, and its temperature resistance is 180 deg.C. However, the plugging agent does not have a self-degradation function, and after temporary plugging, a gel breaking liquid is required to be added to accelerate gel breaking and flowback.

Disclosure of Invention

Aiming at the problems of high wellhead pressure of a long-day oilfield pressurized water injection well, large overflow amount during the tripping of a tubular column by conventional well killing measures, high well control risk, difficult treatment of flowback fluid, complex tripping operation procedure of a pressurized operation machine, long well occupation time, high operation cost and the like, a degradable temporary plugging agent system consisting of a main monomer, a functional cross-linking agent, a built-in degradation catalyst and a reinforcing and toughening agent is researched and developed, and the degradation speed of gel is adjusted by adjusting the addition amount of the built-in degradation catalyst so as to adapt to the requirements of different temperatures and different well conditions on degradation time.

The invention aims at realizing the following technical scheme:

a temporary plugging gel containing an autocatalytic degradation structure comprises the following preparation raw materials in percentage by mass:

preferably, the main monomer is one or more of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, sodium methallyl sulfonate, methacryloxyethyl trimethyl ammonium chloride, sodium p-styrenesulfonate, dimethyl diallyl ammonium chloride, itaconic acid or acrylic acid or maleic anhydride.

Preferably, the structural general formula of the functional crosslinking agent is shown as formula I:

wherein:

R ₁ ＝H，CH ₃ ；R ₂ ＝CH ₂ CH ₂ ，CH ₂ CH ₂ CH ₂ ，CH(CH ₃ )CH ₂ ，CH ₂ CH ₂ CH ₂ CH ₂ ；

X＝F、Cl、Br、I。

preferably, the built-in degradation catalyst is one or more of 2-amino-2-methyl-1-propanol, glycol amine, diisopropylethanolamine, diacetone acrylamide or cyclohexyl propylene glycol.

Preferably, the reinforcing and toughening monomer is one or more of chitosan, n-butyl isocyanate, calcium carbonate, bismaleimide or butyl acrylate.

Preferably, the initiator is one or more of ammonium persulfate, persulfuric acid, potassium persulfate-sodium thiosulfate, ammonium persulfate-sodium bisulfite or azo diisobutylamidine hydrochloride.

Preferably, the temporary plugging gel containing the self-catalytic degradation structure comprises the following preparation raw materials in percentage by mass:

preferably, the main monomer is acrylamide, 2-acrylamido-2-methylpropanesulfonic acid or sodium p-styrenesulfonate; the built-in degradation catalyst is 2-amino-2-methyl-1-propanol or ethylene glycol amine; the reinforcing and toughening monomer is chitosan or bismaleimide; the initiator is ammonium persulfate or azo diisobutylamidine hydrochloride.

A preparation method of temporary plugging gel containing an autocatalytic degradation structure comprises the following steps:

s1, dissolving a main monomer in water, and regulating to be alkalescent by using a regulator to obtain a polymer solution;

s2, sequentially adding a functional cross-linking agent, a built-in degradation catalyst and a reinforcing and toughening monomer into the polymer solution, and mixing and dissolving to obtain a mixed solution;

and S3, adding an initiator into the mixed solution, and heating for reaction to obtain a final product.

The beneficial effects of this technical scheme are as follows:

1. the temporary plugging gel containing the self-catalytic degradation structure is synthesized by compounding various raw materials, has the characteristics of low injection viscosity, controllable gel forming time, high plugging strength, low viscosity of degraded products and the like, and completely meets the temporary plugging process requirements of a water injection well adapting to string detection operation; the temporary plugging gel system mainly comprises a main monomer, a functional cross-linking agent, a built-in degradation catalyst and a reinforcing and toughening agent. The system forms a three-dimensional network structure through chemical crosslinking, because the functional crosslinking agent contains a catalytic degradable chemical bond, the weak bond in the functional crosslinking agent is broken under the action of the built-in catalyst, the three-dimensional network structure disintegrates, and the generated linear low-molecular-weight water-soluble polymer is dissolved in stratum water to form low-viscosity fluid without flowback and influencing subsequent water injection. The crosslinking degree of the gel is adjusted by adjusting the addition of the initiator, the functional crosslinking agent and the monomer, so that the viscosity of degradation products is adjusted; the degradation speed of the gel is adjusted by adjusting the addition amount of the built-in degradation catalyst so as to adapt to the requirements of different temperatures and different well conditions on degradation time.

2. The temporary plugging gel containing the self-catalytic degradation structure provided by the invention has the advantages that the initial viscosity of the gel forming solution of the prepared gel plugging agent is extremely low, and the injectability is good; the gel plugging agent system has a self-degradation function by adopting a functional crosslinking agent, and can be automatically degraded under a certain temperature condition without additional conditions; the catalytic degradation agent is arranged in the gel system and is used cooperatively with the functional cross-linking agent, so that the gel system does not need to be externally added with gel breaker.

Drawings

FIG. 1 is an infrared spectrum of a functional crosslinking agent prepared according to the present invention;

FIG. 2 is a nuclear magnetic resonance spectrum of a functional cross-linking agent prepared by the present invention;

FIG. 3 is a thermogravimetric plot of a functional crosslinker prepared in accordance with the present invention;

FIG. 4 is a graph showing the comparison of the gel blocking agent prepared by the invention before and after degradation;

FIG. 5 is a graph showing the pressure-bearing performance test of the gel plugging agent prepared by the invention under different injection amounts.

Detailed Description

The present invention will be described in further detail with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1

The embodiment provides a preparation method of a functional cross-linking agent.

Wherein: r is R ₁ ＝H，CH ₃ ；R ₂ ＝CH ₂ CH ₂ ，CH ₂ CH ₂ CH ₂ ，CH(CH ₃ )CH ₂ ，CH ₂ CH ₂ CH ₂ CH ₂ ；

X＝F、Cl、Br、I；

The preparation method comprises the steps of weighing two monomers A and B (the molar ratio is 3:1), adding 0.1% -0.3% of polymerization inhibitor, uniformly stirring the polymerization inhibitor by using p-hydroxyanisole, 2-tertiary butyl hydroquinone or p-benzoquinone, and then placing the mixture in a constant-temperature water bath at 45 ℃ for stirring for 48 hours to fully react to obtain white paste. Washing for 3 times after cooling, recrystallizing, filtering, and drying to obtain white powder.

Performance test 1:

the following basic performance tests were carried out on the functional crosslinker prepared in example 1:

(1) Infrared spectroscopic testing of functional crosslinkers

The functional crosslinker was characterized by infrared spectroscopy and the results are shown in figure 1.

As can be seen from FIG. 1, 3010, 2967cm ^-1 The position is a stretching vibration peak of C-H in double bonds; 1725cm ^-1 The stretching vibration peak of C=O in ester bond; 1623cm ^-1 A vibration absorption peak at c=c; 1400. 869cm ^-1 The in-plane and out-of-plane bending vibration peaks of C-H in the double bond are respectively; 1274. 1193cm ^-1 The positions are respectively the anti-symmetrical vibration absorption peak and the symmetrical vibration absorption peak of C-O. The characteristic absorption peaks of the carbon-carbon double bond and the ester group can be found through an infrared spectrogram, which shows that the functional cross-linking agent is synthesized.

(2) Nuclear magnetic resonance characterization of functional crosslinkers

The functional crosslinker was characterized by nuclear magnetic resonance spectroscopy and the results are shown in figure 2.

As can be seen from fig. 2, the chemical shifts of the carbon-carbon double bonds at 6.41, 6.12 and 5.83, the chemical shifts of the protons of the connecting ester groups at 4.59, the chemical shifts of the protons of the connecting nitrogen atoms at 3.52, 3.30 and 4.50, and the chemical shifts of the protons on the benzene rings at 7.11, and the synthesized product can be seen by a spectrogram to conform to the structure of the functional cross-linking agent designed in advance.

(3) Thermogravimetric analysis of functional crosslinker

The functional crosslinker was characterized using a thermal analyzer and the results are shown in figure 3.

As can be seen from fig. 3, the decomposition of the crosslinking agent is mainly divided into three stages, the 1 st stage is room temperature to 210 ℃, the stage is mainly the process of losing the surface moisture of the crosslinking agent and other volatile substances, and the weight is reduced by 3%; the 2 nd stage is 210-380 ℃, and the stage is the main decomposition stage of the molecular chain of the cross-linking agent, mainly the decomposition of the ester group of the molecular chain leads to the breakage of the macromolecular chain, and the weight is reduced by 65%; stage 3 is 380 ℃ or higher, and is the final residue of partial char and other ash. The cross-linking agent has better thermal stability at 210 ℃ and meets the temperature requirement of gel plugging agent application.

Example 2

The embodiment provides a preparation method of temporary plugging gel containing an autocatalytic degradation structure.

Based on 100 parts by mass of each of the components, respectively weighing 10 parts of main monomer acrylamide, 2 parts of functional cross-linking agent (namely example 1), 0.2 part of degradation catalyst 2-amino-2-methyl-1-propanol, 8 parts of reinforcing and toughening monomer chitosan, 0.05 part of initiator ammonium persulfate and the balance of deionized water.

S1, adding 79.75 parts of deionized water into a 150ml beaker at room temperature, adding 10 parts of acrylamide into the deionized water, adjusting the pH of a gel solution to 7.5 by using a sodium hydroxide solution, and obtaining a polymer solution at a stirring speed of 600 r/min;

s2, slowly adding 2 parts of the functional crosslinking agent (namely, the embodiment 1) into a beaker, and uniformly stirring; uniformly adding 8 parts of chitosan and 0.2 part of 2-amino-2-methyl-1-propanol into water within 15 minutes under the stirring of an electric stirrer, adjusting the stirring speed to 300r/min, continuously stirring for 1h, and mixing and dissolving to obtain a mixed solution;

s3, adding 0.05 part of ammonium persulfate into a beaker to obtain gel blocking agent gel forming solution, transferring the gel forming solution into a 250ml wide-mouth bottle, and placing the flask into a water bath kettle at 50 ℃ for reaction and heating to obtain the temporary blocking gel.

Example 3

The embodiment provides a preparation method of temporary plugging gel containing an autocatalytic degradation structure.

Based on 100 parts by mass of the total weight, 4 parts of sodium p-styrenesulfonate serving as a main monomer, 0.5 part of a functional cross-linking agent (namely example 1), 0.01 part of ethylene glycol amine serving as a degradation catalyst, 2 parts of bismaleimide serving as a reinforcing and toughening monomer, 0.03 part of ammonium persulfate serving as an initiator and the balance of deionized water are weighed respectively.

S1, adding 93.46 parts of deionized water into a 150ml beaker at room temperature, adding 4 parts of sodium p-styrenesulfonate into the deionized water, adjusting the pH of a gel solution to 7.5 by using a sodium hydroxide solution, and obtaining a polymer solution at a stirring speed of 600 r/min;

s2, slowly adding 0.5 part of the functional crosslinking agent (namely, the example 1) into a beaker, and uniformly stirring; uniformly adding 2 parts of bismaleimide and 0.01 part of glycol amine into water within 15 minutes under the stirring of an electric stirrer, adjusting the stirring speed to 300r/min, continuously stirring for 1h, and mixing and dissolving to obtain a mixed solution;

s3, adding 0.03 part of ammonium persulfate into a beaker to obtain gel blocking agent gel forming solution, transferring the gel forming solution into a 250ml wide-mouth bottle, and placing the bottle into a water bath kettle at 60 ℃ for reaction and heating to obtain the temporary blocking gel.

Example 4

The embodiment provides a preparation method of temporary plugging gel containing an autocatalytic degradation structure.

Based on 100 parts by mass of each, 6 parts of main monomer 2-acrylamido-2-methylpropanesulfonic acid, 3 parts of functional cross-linking agent (namely example 1), 0.05 part of degradation catalyst ethylene glycol amine, 7 parts of reinforcing and toughening monomer chitosan, 0.02 part of initiator azo diisobutylamidine hydrochloride and the balance of deionized water are respectively weighed.

S1, adding 83.93 parts of deionized water into a 150ml beaker at room temperature, adding 6 parts of acrylamide-2-methylpropanesulfonic acid into the deionized water, adjusting the pH of a gel solution to 7.5 by using a sodium hydroxide solution, and obtaining a polymer solution at a stirring speed of 600 r/min;

s2, slowly adding 3 parts of the functional crosslinking agent (namely, the embodiment 1) into a beaker, and uniformly stirring; uniformly adding 7 parts of chitosan and 0.05 part of glycol amine into water within 15 minutes under the stirring of an electric stirrer, adjusting the stirring speed to 300r/min, continuously stirring for 1h, and mixing and dissolving to obtain a mixed solution;

s3, adding 0.02 part of azodiisobutylamidine hydrochloride into a beaker to obtain gel blocking agent gel forming solution, transferring the gel forming solution into a 250ml wide-mouth bottle, and putting into a water bath kettle at 80 ℃ for reaction and heating to obtain the temporary blocking gel.

Example 5

The embodiment provides a preparation method of temporary plugging gel containing an autocatalytic degradation structure.

10 parts of main monomers (sodium methallylsulfonate and methacryloyloxyethyl trimethyl ammonium chloride), 1 part of a functional crosslinking agent (i.e., example 1), 0.15 part of a degradation catalyst (diisopropylethanolamine and diacetone acrylamide), 6 parts of a reinforcing and toughening monomer (n-butyl isocyanate and calcium carbonate), 0.01 part of an initiator (persulphate and potassium persulfate-sodium thiosulfate) and the balance of deionized water are weighed respectively based on 100 parts by mass of each.

S1, adding 82.84 parts of deionized water into a 150ml beaker at room temperature, adding 10 parts of main monomers (sodium methallyl sulfonate and methacryloyloxyethyl trimethyl ammonium chloride) into the deionized water, adjusting the pH of a gel forming solution to 7.5 by using a sodium hydroxide solution, and obtaining a polymer solution at a stirring speed of 600 r/min;

s2, slowly adding 1 part of the functional crosslinking agent (namely, the embodiment 1) into a beaker, and uniformly stirring; under the stirring of an electric stirrer, uniformly adding 6 parts of reinforcing and toughening monomers (n-butyl isocyanate and calcium carbonate) and 0.15 part of degradation catalyst (diisopropylethanolamine and diacetone acrylamide) into water within 15 minutes, regulating the stirring speed to 300r/min, continuously stirring for 1 hour, and mixing and dissolving to obtain a mixed solution;

s3, adding 0.01 part of initiator (persulphate and potassium persulfate-sodium thiosulfate) into a beaker to obtain gel blocking agent gel forming solution, transferring the gel forming solution into a 250ml wide-mouth bottle, and putting into a water bath kettle at 90 ℃ for reaction and heating to obtain the temporary blocking gel.

Example 6

The embodiment provides a preparation method of temporary plugging gel containing an autocatalytic degradation structure.

15 parts of main monomers (dimethyl diallyl ammonium chloride, itaconic acid, acrylic acid and maleic anhydride), 4 parts of a functional cross-linking agent (i.e. example 1), 0.5 part of a degradation catalyst cyclohexyl propylene glycol, 10 parts of a reinforcing and toughening monomer butyl acrylate, 0.2 part of an initiator ammonium persulfate-sodium bisulphite and the balance of deionized water are respectively weighed according to 100 parts by mass of each.

S1, adding 70.3 parts of deionized water into a 150ml beaker at room temperature, adding 15 parts of main monomers (dimethyl diallyl ammonium chloride, itaconic acid, acrylic acid and maleic anhydride) into the deionized water, adjusting the pH of a gel forming solution to 7.5 by using a sodium hydroxide solution, and obtaining a polymer solution at a stirring speed of 600 r/min;

s2, slowly adding 4 parts of the functional crosslinking agent (namely, the embodiment 1) into a beaker, and uniformly stirring; uniformly adding 10 parts of butyl acrylate and 0.5 part of cyclohexyl propylene glycol into water within 15 minutes under the stirring of an electric stirrer, adjusting the stirring speed to 300r/min, continuously stirring for 1h, and mixing and dissolving to obtain a mixed solution;

s3, adding 0.2 part of ammonium persulfate-sodium bisulphite into a beaker to obtain gel blocking agent gel forming solution, transferring the gel forming solution into a 250ml wide-mouth bottle, and putting into a water bath kettle at 90 ℃ for reaction and heating to obtain the temporary blocking gel.

Performance test 2

The following gel forming property tests were performed on the temporary plugging gel samples prepared in examples 2-6:

and evaluating the gel forming performance of the temporary plugging gel by examining the gel forming time, the gel forming strength and the visual glue forming strength of the temporary plugging gel. In view of the high gel strength of the temporary plugging gel, the gel strength is difficult to test by using a rheometer, so the gel strength is tested by using a vicat penetration method, and the penetration depth of the gel is tested to express the strength of the gel. Visual gel strength of the temporary plugging gel is referenced in table 1.

TABLE 1 gel strength code table

Code	Description of the invention
		A	The viscosity of the system is the same as that of the polymer solution with the same concentration without adding the cross-linking agent
B	The viscosity of the system is slightly increased as that of the polymer solution with the same concentration without adding the cross-linking agent
		C	When the reagent bottle is inverted, most of gel flows to the bottle cap
D	When the reagent bottle is inverted, only a small part of gel is not easy to flow to the bottle cap
		E	When the reagent bottle is inverted, the gel slowly flows to the bottle cap or a large part flows to the bottle cap
F	When the reagent bottle is inverted, the gel cannot flow to the bottle cap
		G	When the reagent bottle is inverted, the gel flows downwards to about half of the position
H	When the reagent bottle is inverted, only the surface of the gel is slightly deformed
		I	When the reagent bottle is inverted, the surface of the gel does not deform

(1) The results of the gel forming performance test performed on the temporary plugging gel samples prepared in examples 2 to 6 are shown in Table 2.

Table 2 shows the gel forming property test of the temporary plugging gel samples prepared in examples 2 to 6

As shown in Table 2, the base solution viscosity of the degradable gel plugging agent is less than 10 mPa.s, the gel plugging agent has good injectability, the gel forming time is adjustable for 2-3 hours, the gel forming strength is I grade rigid gel, the penetration degree is 9-12mm, and the gel has good gel forming performance.

(2) On the basis of the embodiment 4, other conditions are kept unchanged, the concentration of the main monomer of the temporary plugging gel is changed to be 8 parts, 9 parts, 10 parts, 11 parts and 12 parts respectively, and the influence of the addition amount of the main monomer on the gel strength is explored, and the result is shown in the table 3;

TABLE 3 influence of Main monomer addition on blocking agent Performance

Monomer addition	Gel time/h	Gel strength/mm	Visual examination of gel strength
				8 parts of	3	15.38	H
9 parts of	3	13.95	H
				10 parts of	2	10.03	H
11 parts of	2	9.98	I
				12 parts of	2	9.55	I

As shown in Table 3, when the monomer concentration is lower than 9%, the gel forming time is about 3 hours, the gel forming strength is not high (the gel forming time is slow at 50 ℃ for 1 hour), and the requirement is difficult to meet; when the monomer concentration is higher than 10%, the gel forming time is shortened by 1h, the strength is basically consistent, and the main monomer concentration is selected to be 10%.

(3) On the basis of the embodiment 4, other conditions are kept unchanged, the concentration of the temporary plugging gel reinforcing and toughening monomer is changed to be 4 parts, 6 parts, 8 parts, 10 parts and 12 parts respectively, and the influence of the addition amount of the reinforcing and toughening monomer on the gel strength is explored, and the result is shown in the table 5;

TABLE 5 influence of the addition of reinforcing and toughening monomers on the gel blocking agent Performance

Reinforcing and toughening monomer addition amount	Gel time/h	Gel strength/mm	Visual examination of gel strength
				4 parts of	3	8.43	I
6 parts of	3	7.71	I
				8 parts of	3	6.86	I
10 parts of	3	6.05	I
				12 parts of	3	5.97	I

As can be seen from table 5, the concentration of the reinforcing and toughening monomer has no influence on the gelling time, the gelling strength becomes stronger with the increase of the reinforcing and toughening monomer, and when the reinforcing and toughening monomer is higher than 8%, the gelling strength is kept substantially consistent, and the concentration of the reinforcing and toughening monomer is selected to be 8%.

Performance test 3

The experimental example is a self-degradation performance test of temporary plugging gel containing a self-catalytic degradation structure.

100g of gel sample is weighed and placed in a wide-mouth bottle, the wide-mouth bottle is placed in a water bath kettle with the temperature of 90 ℃ to react into gel, and the mass retention rate of the temporary plugging gel is tested according to the following formula for 1 d/time under the temperature of 90 ℃.

Wherein alpha is mass retention, m ₁ Residual mass, m ₀ -an initial mass.

Taking the temporary plugging gel prepared in example 2 as an example, the degradation performance of the temporary plugging gel is shown in table 6:

TABLE 6 self-degradation Properties of gel blocking Agents

TestingTime/d	0	1	2	4	6	8
							Mass retention/%	100	96.5	80.4	43.5	19.8	0

As can be seen from table 6 and fig. 4, the temporary plugging gel is completely degraded after 10 days at 90 ℃ without adding a breaker, and realizes the self-degradation function.

Performance test 4

The experimental example is a temporary plugging gel plugging and plugging removal experimental result containing a self-degradation catalytic structure.

(1) Core bearing performance

In order to test the pressure-bearing performance of the degradable gel plugging agent, the solution is prepared in advance and injected into the sand filling pipe, and the injection amount of the self-degradable isolation material is respectively tested to be 0.25PV,0.5PV, 0.75PV and 1PV of the total injection amount. The nitrogen cylinder is connected with the outlet end of the sand filling pipe, and the pressure-bearing performance of the self-degrading temporary plugging material under different injection amounts is tested by reverse injection.

The optimized formula is selected: 5% of main monomer, 0.6% of functional cross-linking agent, 1.5% of reinforcing toughening agent, 0.10% of initiator and 0.3% of degradation catalyst are injected into a sand filling pipe, are taken out after being glued in a constant temperature oven at 60 ℃, and then a displacement device is used for testing the pressure-bearing performance of temporary plugging gel by using a reverse injection method, and the pressure change is monitored and recorded in real time.

Table 7 experimental core parameters

As is clear from Table 7 and FIG. 5, the pressure-bearing performance of the gel plugging agent gradually increased as the injection amount increased from 0.25 to 1, and the pressure-bearing pressure increased from 8MPa to 30MPa. When the injection amount of the plugging agent is lower than 0.5PV, the bearing pressure only reaches 15MPa, but when the injection amount is more than or equal to 0.75PV, the bearing pressure of the plugging agent is more than 25MPa, which indicates that the prepared self-degrading gel plugging agent has good bearing performance. The pressure-bearing performance curve has only one breakthrough point, which indicates that the gas breaks through the gel instead of the gap between the gel and the pipe wall, and the adhesive force between the gel blocking agent and the pipe wall is very high, so that the gel blocking agent and the pipe wall can be well adhered to a shaft during construction operation.

(2) Plugging and deblocking properties

And evaluating the plugging capacity of the self-degrading temporary plugging gel in the porous medium by adopting a core displacement device. The specific experimental steps are as follows: (1) artificial sandstone crack core (core size is) Drying in a 90 deg.C oven for 24 hr, accurately weighing the dry weight of the core after the core is completely dried, and recording as m ₀ Then, the core is saturated with water for 24 hours, the wet weight of the core is accurately weighed and recorded as m, the radius r and the length l of the core are measured, the porosity of the core is calculated, and the calculation formula is as follows:

(2) placing the rock core in a rock core holder displacement device, injecting stratum water into the rock core at a water injection speed of 1ml/min by using a constant flow pump, and reading and injectingAfter the end pressure is stabilized as the displacement pressure, the original permeability k is calculated ₀ The calculation formula is as follows:

wherein k is the permeability, μm ² The method comprises the steps of carrying out a first treatment on the surface of the Q is the fluid flow rate, cm ³ S; mu is the viscosity of the fluid, 10 ^-3 Pa·s; Δl is core length, cm; a is the area of the core crack, cm ² The method comprises the steps of carrying out a first treatment on the surface of the ΔP is the differential pressure between the two ends of the core, 10 ⁵ Pa。

(3) Injecting temporary plugging gel with the volume of 0.3PV into the rock core at a constant flow rate of 1mL/min, and aging for 60 days at 90 ℃; setting the water injection flow rate to be 1mL/min, injecting water into the rock core again until the injection pressure is stabilized again, recording the real-time change of the pressure at the required time in the whole displacement process, and calculating the plugging rate, wherein the plugging rate has the following calculation formula:

wherein k is ₀ For the original permeability, μm ² K is the permeability after plugging, μm ² 。

(4) And (3) placing the core containing the residual temporary plugging gel in an oven at 90 ℃ for continuous aging until the temporary plugging gel is completely degraded, injecting water into the core at a flow rate of 1mL/min until the pressure is stable, and testing the permeability recovery rate of the core, wherein the calculation formula is as follows:

wherein k is ₀ For the original permeability, μm ² K' is the permeability after unblocking, μm ² 。

Taking the temporary plugging gel prepared in example 4 as an example, the plugging and unplugging properties are shown in table 7:

TABLE 8 blocking Properties of gel blocking agent

As shown in Table 8, the blocking rate of the temporary blocking gel to the core reaches 99.3% at 90 ℃, and the temporary blocking gel has excellent blocking performance, and the core permeability recovery rate reaches 91.4% after the temporary blocking gel is degraded, so that the temporary blocking gel has better blocking removal performance.

Finally, what should be said is: the above embodiments are only for illustrating, not limiting, the technical solutions of the present invention, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention, which is intended to be encompassed by the claims.

Claims (10)

1. The temporary plugging gel containing the self-catalytic degradation structure is characterized by comprising the following preparation raw materials in percentage by mass:

2. a temporary plugging gel containing an autocatalytic degradation structure according to claim 1, wherein: the main monomer is one or more of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, sodium methallyl sulfonate, methacryloxyethyl trimethyl ammonium chloride, sodium p-styrenesulfonate, dimethyl diallyl ammonium chloride, itaconic acid or acrylic acid or maleic anhydride.

3. A temporary plugging gel containing an autocatalytic degradation structure according to claim 1, wherein: the structural general formula of the functional cross-linking agent is shown as formula I:

wherein:

R ₁ ＝H，CH ₃ ；R ₂ ＝CH ₂ CH ₂ ，CH ₂ CH ₂ CH ₂ ，CH(CH ₃ )CH ₂ ，CH ₂ CH ₂ CH ₂ CH ₂ ；

X＝F、Cl、Br、I。

4. a temporary plugging gel containing an autocatalytic degradation structure according to claim 1, wherein: the built-in degradation catalyst is one or more of 2-amino-2-methyl-1-propanol, glycol amine, diisopropylethanolamine, diacetone acrylamide or cyclohexyl propylene glycol.

5. A temporary plugging gel containing an autocatalytic degradation structure according to claim 1, wherein: the reinforcing and toughening monomer is one or more of chitosan, n-butyl isocyanate, calcium carbonate, bismaleimide or butyl acrylate.

6. A temporary plugging gel containing an autocatalytic degradation structure according to claim 1, wherein: the initiator is one or more of ammonium persulfate, persulfuric acid, potassium persulfate-sodium thiosulfate, ammonium persulfate-sodium bisulfite or azo diisobutylamidine hydrochloride.

7. A temporary plugging gel containing an autocatalytic degradation structure according to claim 1, wherein: the temporary plugging gel containing the self-catalytic degradation structure comprises the following preparation raw materials in percentage by mass:

8. a temporary plugging gel containing an autocatalytic degradation structure as defined in claim 7 wherein: the main monomer is acrylamide, 2-acrylamide-2-methylpropanesulfonic acid or sodium p-styrenesulfonate; the built-in degradation catalyst is 2-amino-2-methyl-1-propanol or ethylene glycol amine.

9. A temporary plugging gel containing an autocatalytic degradation structure as defined in claim 8 wherein: the reinforcing and toughening monomer is chitosan or bismaleimide; the initiator is ammonium persulfate or azo diisobutylamidine hydrochloride.

10. The preparation method of the temporary plugging gel containing the self-catalytic degradation structure is characterized by comprising the following steps of:

s1, dissolving a main monomer in water, and regulating to be alkalescent by using a regulator to obtain a polymer solution;

s2, sequentially adding a functional cross-linking agent, a built-in degradation catalyst and a reinforcing and toughening monomer into the polymer solution, and mixing and dissolving to obtain a mixed solution;

and S3, adding an initiator into the mixed solution, and heating for reaction to obtain a final product.