A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid and its preparation method

Abstract

The invention relates to the technical field of fracturing fluid preparation, and specifically discloses a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid and a preparation method thereof. The micro-foam fracturing fluid is prepared with one of air, nitrogen and carbon dioxide as a gas phase and a base liquid as a liquid phase; the base liquid raw material comprises the following components in percentage by mass: a foaming agent, a foam stabilizer, a repairing agent, a cross-linking agent, a temperature stabilizer, and the balance is water; the preparation method comprises: mixing the foaming agent, the foam stabilizer, the cross-linking agent, the temperature stabilizer, the repairing agent and water for cross-linking reaction to obtain the base liquid; introducing gas into the base liquid and stirring to obtain the base liquid; the non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid provided by the invention has excellent system performance under high temperature (150°C), high salinity (2Wppm) and harsh formation fluid conditions, and is used in the production increase and transformation of low-pressure and low-permeability, easy to leak, water-deficient and water-sensitive formations.

Description

Technical Field

[0001] The invention relates to the technical field of fracturing fluid preparation, and more specifically, to a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid and a preparation method thereof. Background Art

[0002] With the continuous reduction of high-quality oil and gas reservoirs in China, the development of unconventional oil and gas reservoirs has become the focus of research for many experts and scholars. The development of unconventional oil and gas reservoirs mainly includes tight sandstone gas reservoirs, shale gas, coalbed methane, etc. In the development of such oil and gas reservoirs, hydraulic fracturing operations are generally used to increase production. Due to the complex geological characteristics of the reservoir, conventional water-based fracturing fluids have many problems, showing poor adaptability and negative transformation effects, such as low formation energy, low oil and gas recovery rate, formation water sensitivity, serious water lock damage, difficulty in returning a large amount of fracturing fluid after fracturing, and serious secondary pollution of hydraulic fracturing. The existence of these problems has led to unsatisfactory fracturing and production increase effects in the development of unconventional oil and gas fields, and a significant decline in oil and gas production. At the same time, after years of exploitation, the physical properties and pressure systems of the oil layers in major oil fields and other old oil areas have changed greatly. After long-term development, the reservoirs are seriously depleted, and problems such as low formation pressure coefficient and well leakage appear. It is difficult to complete effective transformation using conventional fracturing fluid systems.

[0003] Foam fracturing fluid technology is a new fracturing process developed to address the poor fracturing effect of low-pressure and low-permeability oil layers, the greater damage to the formation caused by water-based fracturing fluid, the difficulty in draining and carrying sand. This technology is based on conventional water-based fracturing fluid, adding foaming agent and carbon dioxide gas to form a foam fluid, and obtains a low-damage fracturing fluid system with gas as the inner phase and liquid as the outer phase. Foam fracturing fluid has the characteristics of strong sand carrying capacity, low filtration loss damage, automatic pressure boosting and drainage, good self-flowing and backflow, low damage rate, low density, etc. It is very suitable for the fracturing transformation of new wells and old wells in low-pressure and low-permeability oil and gas reservoirs and is widely used.

[0004] However, the existing foam fracturing fluids are all foamed by surfactants, which are highly dependent on surfactants and greatly affected by well conditions. They are thermodynamically unstable fluids, especially those with temperatures above 60°C, salinity greater than 1w, and poor formation fluids, which have a significant impact on the performance of foam fracturing fluids foamed by surfactants, restricting the application of foam fracturing fluids. Conventional foam fracturing fluids in the prior art are prone to cause large amounts of liquid loss, insufficient seam formation, low construction displacement, poor sand carrying performance, low sand addition, early sand removal, sand plugging, and other accidents during fracturing operations.

[0005] In order to avoid the above defects, my country has started to study foam fracturing fluid since the 1980s. The experimental application of foam fracturing fluid in some oil and gas fields has not been very ideal. At present, conventional foam fracturing fluid in China faces the following problems:

[0006] (1) The stability period of foam is short. At present, the stability time of foam fracturing fluid in the fracturing process of deep and ultra-deep wells is 10 minutes to 30 minutes, which is difficult to meet the time requirements from fluid preparation to fracturing construction;

[0007] (2) Foam fracturing fluid is not resistant to high temperatures and salt, has low pressure resistance, and has poor foam stability under high temperatures and high mineralization, resulting in a sudden change in fracturing fluid density.

[0008] (3) The foam of the foam fracturing fluid is affected by physical and chemical factors. Foam loss is inevitable during the construction process, which affects the construction effect.

[0009] (4) Under the action of pumping pressure and liquid column pressure, the foam volume of the foam fracturing fluid decreases and its sand carrying capacity decreases.

[0010] (5) The core damage rate is large and the residue is high; the drag reduction rate is low, resulting in high construction pressure. Based on the above statements, the present invention provides a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid and a preparation method thereof. Summary of the invention

[0011] In order to solve the problems existing in the existing foam fracturing fluid, the present invention provides a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid and a preparation method thereof. The non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid provided by the present invention has excellent use effect under high temperature (150°C), high salinity (2Wppm) and formation fluid conditions.

[0012] In the first aspect, the present invention provides a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid, which adopts the following technical scheme:

[0013] A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid is prepared with one of air, nitrogen and carbon dioxide as a gas phase and a base liquid as a liquid phase; the volume fraction of foam in the micro-foam fracturing fluid is 40-80%; the base liquid raw material comprises the following components in mass percentage: 0.01-0.5% of a foaming agent, 0.02-0.05% of a foam stabilizer, 1-6% of a repair agent, 0.1-0.8% of a cross-linking agent, 0.01-0.2% of a temperature stabilizer, and the balance is water.

[0014] Preferably, the base liquid raw material includes the following components in percentage by mass: 0.2% of foaming agent, 0.03% of foam stabilizer, 2% of repair agent, 0.1% of cross-linking agent, 0.05% of temperature stabilizer, and the balance is water.

[0015] Preferably, the foaming agent is a non-surfactant polymer: β-cyclodextrin type polyoxyethylene ether, the molecular structure of which is as follows:

[0016] .

[0017] Preferably, the preparation method of the β-cyclodextrin type polyoxyethylene ether is:

[0018] Add β-cyclodextrin and catalyst to the dry reactor, install the reactor and seal it, purge the pipeline and the reactor with nitrogen for 3 times, stir and heat to 90-120°C, use a water pump to vacuum for 20-40 minutes, continue to heat to 125-135°C, introduce ethylene oxide, control the pressure to 0.2-0.3MPa, react for 1.5-2h, continue to stir until the pressure is 0MPa, cool and vacuum to the temperature in the reactor of 70-90°C, stop vacuuming, wait until the pressure in the reactor drops to negative pressure, cool and discharge the material, remove the precipitate by centrifugation, and dry to remove water to obtain β-cyclodextrin type polyoxyethylene ether.

[0019] Preferably, the catalyst is NaOH, and the amount of the catalyst added is 0.5% of the mass of β-cyclodextrin.

[0020] Preferably, the foam stabilizer is one or more of polyacrylamide, guar gum, xanthan gum, welan gum and diutan gum.

[0021] Preferably, the repair agent is a sodium carbonate, sodium bisulfate composition or a hydrogen peroxide, manganese dioxide composition.

[0022] Preferably, in the sodium carbonate and sodium bisulfate composition, the mass ratio of sodium carbonate to sodium bisulfate is 3-5:1; in the hydrogen peroxide and manganese dioxide composition, the mass ratio of hydrogen peroxide to manganese dioxide is 1:1-3.

[0023] Preferably, the cross-linking agent is one of an organic zirconium cross-linking agent, zirconium oxychloride or potassium chromium sulfate.

[0024] Preferably, the temperature stabilizer is sodium thiosulfate or ascorbic acid.

[0025] In a second aspect, the present invention provides a method for preparing a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid, which adopts the following technical scheme:

[0026] A method for preparing a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid comprises the following preparation steps:

[0027] S1, mixing a foaming agent, a foam stabilizer, a cross-linking agent, a temperature stabilizer, a repair agent and water to perform a cross-linking reaction to obtain a base liquid;

[0028] S2, introducing gas into the base fluid obtained in step S1, and stirring to obtain a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid.

[0029] In summary, the present invention has the following beneficial effects:

[0030] The non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid proposed by the present invention is prepared by using a non-surfactant foaming agent, a foam stabilizer, a repair agent, a cross-linking agent, a temperature stabilizer and water as raw material components, and is coordinated and matched through a specific ratio and the selection of specific raw materials; wherein, the β-cyclodextrin type polyoxyethylene ether is a multi-claw radial multi-chain polymer, after the β-cyclodextrin type polyoxyethylene ether is stretched in water, the gas and liquid are quickly mixed by stirring, and the gas molecules are adsorbed on the radial long chains of the polymer, and the radial long chains of the polymer molecules have an inner cavity and an outer cavity structure, the inner cavity binds the gas, the outer cavity encapsulates the gas, the ends of the outer cavity long chains have associative functional groups, and the end groups lock the encapsulated gas through mutual association to form microbubbles. The higher the stirring rate, the more the microbubbles are subdivided and cut into smaller microbubbles due to high shear stress, which are not affected by surface tension, and the microbubble particle size can reach a range of 10um-200um; the stabilizer is selected from a specific ratio of high molecular anionic polyacrylamide and / or high viscosity guar gum, xanthan gum, welan gum, diutan gum, etc., which are used in combination to form a uniform, stable and reinforced thick-walled microfoam; according to the gas state equation and experimental confirmation, the foam liquid is a compressible fluid. After being injected into the wellbore, due to the effects of formation pressure and liquid column pressure, the foam volume becomes smaller, the density becomes larger, and the sand suspension capacity is reduced, which is easy to cause sand blockage and sand transportation difficulties. Based on this problem, the present invention also innovates a technology for repairing the volume of foam fracturing fluid. The present invention adds a repair agent into a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid system. The repair agent triggers a large amount of gas production reaction in the wellbore due to the increase in temperature, thereby continuously foaming in the wellbore, increasing the volume of the foam fracturing fluid, and compensating for the compressed foam volume. The defects of the use of conventional water-based foam fracturing fluid are completely solved, and the invention has the characteristics of strong sand carrying capacity, effective prevention of well leakage, protection of oil and gas layers, avoidance of reservoir damage and construction discontinuity, sand plugging accidents, etc. Since the preparation method proposed by the present invention is simple and the performance is stable, it has important promotion value, especially in low-pressure oil and gas layer fracturing operations and old well production increase operations with low formation pressure coefficients, the construction effect is remarkable.

[0031] The non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid provided by the present invention has excellent system performance under high temperature (150°C), high salinity (2Wppm) and harsh formation fluid conditions, and is used in the production enhancement and transformation of low-pressure, low-permeability, leak-prone, water-deficient and water-sensitive formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a graph showing the temperature and shear resistance test of the micro-foam fracturing fluid obtained in Example 1 of the present invention.

[0033] Figure 2 This is a diagram of the drag reduction experiment of the micro-foam fracturing fluid obtained in Example 1 of the present invention.

[0034] Figure 3 This is a diagram of the drag reduction experiment of the micro-foam fracturing fluid obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the embodiments.

[0036] Embodiment 1-2 provides a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid and a preparation method thereof.

[0037] Embodiment 1:

[0038] A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid is prepared with nitrogen as the gas phase and a base liquid as the liquid phase; the volume fraction of the foam in the micro-foam fracturing fluid is 50%; the base liquid raw material includes the following components in mass percentage: the base liquid raw material includes the following components in mass percentage: 0.2% of a foaming agent, 0.03% of a foam stabilizer, 2% of a repairing agent, 0.1% of a cross-linking agent, 0.05% of a temperature stabilizer, and the balance is water;

[0039] Wherein, the foaming agent is a non-surfactant polymer: β-cyclodextrin type polyoxyethylene ether, and its preparation method is as follows:

[0040] Add 0.1 mol of β-cyclodextrin and catalyst NaOH (the amount of catalyst added is 0.5% of the mass of β-cyclodextrin) to a dry 250 mL reactor, install the reactor and seal it, purge the pipeline and the reactor with nitrogen for 3 times, stir and heat to 100°C, vacuumize with a water pump for 30 minutes, close the vacuum exhaust valve, continue to heat to 130°C, and then slowly introduce 0.5 mol of ethylene oxide (EO) from the reactor feed pipe. During the reaction, the pressure is maintained at 0.2 MPa by controlling the feed valve. After reacting for 2 hours, the pressure in the reactor gradually decreases, continue to stir until the pressure is 0 MPa, cool and vacuumize to 80°C in the reactor, stop vacuuming, cool and discharge after the pressure in the reactor drops to negative pressure, and finally neutralize the catalyst NaOH with phosphoric acid, remove the precipitate by centrifugation and dry to remove water to obtain β-cyclodextrin type polyoxyethylene ether;

[0041] The foam stabilizer includes polyacrylamide and guar gum in a mass ratio of 2:1;

[0042] The repair agent is a combination of sodium carbonate and sodium bisulfate, and the mass ratio of sodium carbonate to sodium bisulfate is 4:1;

[0043] The cross-linking agent is zirconium oxychloride;

[0044] The temperature stabilizer is sodium thiosulfate.

[0045] A method for preparing a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid comprises the following steps:

[0046] S1, mixing a foaming agent, a foam stabilizer, a cross-linking agent, a temperature stabilizer, a repairing agent and water for cross-linking reaction for 2 hours to obtain a base liquid;

[0047] S2. Introduce gas into the base fluid obtained in step S1, stir at 3000 r / min for 20 min, and obtain a self-repairing high-quality micro-foam fracturing fluid with non-surfactant foaming.

[0048] The performance indicators of the micro-foam fracturing fluid obtained in this Example 1 are as follows in Table 1:

[0049] Table 1 Foam fracturing fluid performance indicators

[0050] ;

[0051] The micro-foam fracturing fluid obtained in Example 1 is subjected to a temperature and shear resistance test. Figure 1 , resistance reduction test diagram is shown in Figure 2 .

[0052] Embodiment 2:

[0053] A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid is prepared with air as the gas phase and base fluid as the liquid phase; the volume fraction of the foam in the micro-foam fracturing fluid is 40%; the base fluid raw material includes the following components in mass percentage: 0.3% foaming agent, 0.05% foam stabilizer, 3% repair agent, 0.2% cross-linking agent, 0.05% temperature stabilizer, and the balance is water;

[0054] Wherein, the foaming agent is a non-surfactant polymer: β-cyclodextrin type polyoxyethylene ether, and its preparation method is as follows:

[0055] Add 0.1 mol of β-cyclodextrin and catalyst NaOH (the amount of catalyst added is 0.5% of the mass of β-cyclodextrin) to a dry 250 mL reactor, install the reactor and seal it, purge the pipeline and the reactor with nitrogen for 3 times, stir and heat to 110°C, use a water pump to evacuate for 40 minutes, close the vacuum exhaust valve, continue to heat to 125°C, and then slowly introduce 0.5 mol of ethylene oxide (EO) from the reactor feed pipe. During the reaction, the pressure is maintained at 0.3 MPa by controlling the feed valve. After 1.5 hours of reaction, the pressure in the reactor gradually decreases, and stirring is continued until the pressure is 0 MPa, then the temperature is lowered and evacuated to 90°C in the reactor, and the evacuation is stopped. After the pressure in the reactor drops to negative pressure, the material is cooled and discharged, and finally the catalyst NaOH is neutralized with phosphoric acid, the precipitate is removed by centrifugation, and the water is removed by drying to obtain β-cyclodextrin type polyoxyethylene ether;

[0056] The foam stabilizer includes polyacrylamide and welan gum in a mass ratio of 3:1;

[0057] The repair agent is a combination of hydrogen peroxide and manganese dioxide, and the mass ratio of hydrogen peroxide to manganese dioxide is 1:2;

[0058] The cross-linking agent is potassium chromium sulfate;

[0059] The temperature stabilizer is ascorbic acid.

[0060] A method for preparing a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid comprises the following steps:

[0061] S1, mixing a foaming agent, a foam stabilizer, a cross-linking agent, a temperature stabilizer, a repairing agent and water for cross-linking reaction for 2 hours to obtain a base liquid;

[0062] S2. Introduce gas into the base fluid obtained in step S1, stir at 3000 r / min for 20 min, and obtain a self-repairing high-quality micro-foam fracturing fluid with non-surfactant foaming.

[0063] The performance indicators of the micro-foam fracturing fluid obtained in this Example 2 are as follows in Table 2:

[0064] Table 2 Foam fracturing fluid performance indicators

[0065] ;

[0066] The micro-foam fracturing fluid resistance reduction test diagram obtained in Example 2 is shown in Figure 3 .

[0067] Embodiment 3:

[0068] A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid is prepared with nitrogen as the gas phase and base fluid as the liquid phase; the volume fraction of the foam in the micro-foam fracturing fluid is 70%; the base fluid raw material includes the following components in mass percentage: 0.4% foaming agent, 0.04% foam stabilizer, 4% repair agent, 0.5% cross-linking agent, 0.15% temperature stabilizer, and the balance is water;

[0069] The foaming agent is a non-surfactant polymer: β-cyclodextrin type polyoxyethylene ether, and its preparation method is as follows:

[0070] Add 0.1 mol of β-cyclodextrin and catalyst NaOH (the amount of catalyst added is 0.5% of the mass of β-cyclodextrin) to a dry 250 mL reactor, install the reactor and seal it, purge the pipeline and the reactor with nitrogen for 3 times, stir and heat to 100°C, vacuumize with a water pump for 30 minutes, close the vacuum exhaust valve, continue to heat to 130°C, and then slowly introduce 0.5 mol of ethylene oxide (EO) from the reactor feed pipe. During the reaction, the pressure is maintained at 0.25 MPa by controlling the feed valve. After 1.8 hours of reaction, the pressure in the reactor gradually decreases, continue to stir until the pressure is 0 MPa, cool and vacuumize to 80°C in the reactor, stop vacuuming, wait until the pressure in the reactor drops to negative pressure, cool and discharge, and finally neutralize the catalyst NaOH with phosphoric acid, remove the precipitate by centrifugation and dry to remove water to obtain β-cyclodextrin type polyoxyethylene ether;

[0071] The foam stabilizer includes polyacrylamide and welan gum in a mass ratio of 3:1;

[0072] The repair agent is a combination of sodium carbonate and sodium bisulfate, and the mass ratio of sodium carbonate to sodium bisulfate is 3:1;

[0073] The cross-linking agent is zirconium oxychloride;

[0074] The temperature stabilizer is sodium thiosulfate.

[0075] A method for preparing a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid comprises the following steps:

[0076] S1, mixing a foaming agent, a foam stabilizer, a cross-linking agent, a temperature stabilizer, a repairing agent and water for cross-linking reaction for 2 hours to obtain a base liquid;

[0077] S2. Introduce gas into the base fluid obtained in step S1, stir at 3000 r / min for 20 min, and obtain a self-repairing high-quality micro-foam fracturing fluid with non-surfactant foaming.

[0078] The performance indicators of the micro-foam fracturing fluid obtained in this Example 3 are as follows in Table 3:

[0079] Table 3 Foam fracturing fluid performance indicators

[0080] ;

[0081] Embodiment 4:

[0082] A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid is prepared with air as the gas phase and base fluid as the liquid phase; the volume fraction of foam in the micro-foam fracturing fluid is 80%; the base fluid raw material includes the following components in mass percentage: 0.5% foaming agent, 0.05% foam stabilizer, 6% repair agent, 0.8% cross-linking agent, 0.2% temperature stabilizer, and the balance is water;

[0083] The foaming agent is a non-surfactant polymer: β-cyclodextrin type polyoxyethylene ether, and its preparation method is as follows:

[0084] Add 0.1 mol of β-cyclodextrin and catalyst NaOH (the amount of catalyst added is 0.5% of the mass of β-cyclodextrin) to a dry 250 mL reactor, install the reactor and seal it, purge the pipeline and the reactor with nitrogen for 3 times, stir and heat to 120°C, evacuate with a water pump for 20 minutes, close the vacuum exhaust valve, continue to heat to 135°C, and then slowly introduce 0.5 mol of ethylene oxide (EO) from the reactor feed pipe. During the reaction, the pressure is maintained at 0.25 MPa by controlling the feed valve. After 1.8 hours of reaction, the pressure in the reactor gradually decreases, continue to stir until the pressure is 0 MPa, cool and evacuate to 70°C in the reactor, stop evacuating, wait until the pressure in the reactor drops to negative pressure, cool and discharge, and finally neutralize the catalyst NaOH with phosphoric acid, remove the precipitate by centrifugation and dry to remove water to obtain β-cyclodextrin type polyoxyethylene ether;

[0085] The foam stabilizer includes polyacrylamide and diutan gum in a mass ratio of 1:1;

[0086] The repair agent is a combination of hydrogen peroxide and manganese dioxide, and the mass ratio of hydrogen peroxide to manganese dioxide is 1:1;

[0087] The cross-linking agent is an organic zirconium cross-linking agent;

[0088] The temperature stabilizer is ascorbic acid.

[0089] A method for preparing a non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid comprises the following steps:

[0090] S1, mixing a foaming agent, a foam stabilizer, a cross-linking agent, a temperature stabilizer, a repairing agent and water for cross-linking reaction for 2 hours to obtain a base liquid;

[0091] S2. Introduce gas into the base fluid obtained in step S1, stir at 3000 r / min for 20 min, and obtain a self-repairing high-quality micro-foam fracturing fluid with non-surfactant foaming.

[0092] The performance indicators of the micro-foam fracturing fluid obtained in this Example 4 are shown in Table 4 below:

[0093] Table 4 Foam fracturing fluid performance indicators

[0094] ;

[0095] The performance of the non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid prepared in the embodiment of the present invention is compared with that of the conventional surfactant foam fracturing fluid system. The results are shown in Table 5 below.

[0096] Table 5 Performance comparison of two foam fracturing fluid systems

[0097] ;

[0098] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid, characterized in that: The micro-foam fracturing fluid is prepared with one of air, nitrogen and carbon dioxide as the gas phase and base liquid as the liquid phase; the volume fraction of the foam in the micro-foam fracturing fluid is 40-80%; the base liquid raw material includes the following components in mass percentage: 0.01-0.5% of foaming agent, 0.02-0.05% of foam stabilizer, 1-6% of repair agent, 0.1-0.8% of cross-linking agent, 0.01-0.2% of temperature stabilizer, and the balance is water; The foaming agent is a non-surfactant polymer: β-cyclodextrin type polyoxyethylene ether; The preparation method of the β-cyclodextrin type polyoxyethylene ether is as follows: Add β-cyclodextrin and a catalyst to a dry reactor, install the reactor and seal it, purge the pipeline and the reactor with nitrogen for 3 times, stir and heat to 90-120°C, evacuate with a water pump for 20-40 minutes, continue to heat to 125-135°C, introduce ethylene oxide, control the pressure to 0.2-0.3MPa, react for 1.5-2h, continue to stir until the pressure is 0MPa, cool and evacuate to the temperature in the reactor of 70-90°C, stop evacuating, cool and discharge after the pressure in the reactor drops to negative pressure, remove the precipitate by centrifugation, and dry to remove water to obtain β-cyclodextrin type polyoxyethylene ether; The repairing agent is a sodium carbonate, sodium bisulfate composition or a hydrogen peroxide, manganese dioxide composition.

2. The non-surfactant foamed self-repairing high-quality micro-foam fracturing fluid according to claim 1, characterized in that: The base liquid raw material includes the following components in percentage by mass: 0.2% of a foaming agent, 0.03% of a foam stabilizer, 2% of a repair agent, 0.1% of a cross-linking agent, 0.05% of a temperature stabilizer, and the balance is water.

3. The non-surfactant foamed self-repairing high-quality micro-foam fracturing fluid according to claim 1, characterized in that: The foam stabilizer is one or more of polyacrylamide, guar gum, xanthan gum, welan gum and diutan gum.

4. The non-surfactant foamed self-repairing high-quality micro-foam fracturing fluid according to claim 1, characterized in that: In the sodium carbonate and sodium bisulfate composition, the mass ratio of sodium carbonate to sodium bisulfate is 3-5:1; in the hydrogen peroxide and manganese dioxide composition, the mass ratio of hydrogen peroxide to manganese dioxide is 1:1-3.

5. The non-surfactant foamed self-repairing high-quality micro-foam fracturing fluid according to claim 1, characterized in that: The cross-linking agent is one of an organic zirconium cross-linking agent, zirconium oxychloride or potassium chromium sulfate.

6. The non-surfactant foamed self-repairing high-quality micro-foam fracturing fluid according to claim 1, characterized in that: The temperature stabilizer is sodium thiosulfate or ascorbic acid.

7. A method for preparing the non-surfactant foaming self-repairing high-quality micro-foam fracturing fluid according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, mixing a foaming agent, a foam stabilizer, a cross-linking agent, a temperature stabilizer, a repair agent and water to perform a cross-linking reaction to obtain a base liquid; S2, introducing gas into the base fluid obtained in step S1, and stirring to obtain a self-repairing high-quality micro-foam fracturing fluid with non-surfactant foaming.

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