An activation composition and breaker containing the same

Abstract

The application provides an activation composition and a breaker containing the same. The activation composition comprises an inorganic reducing agent, an organic reducing agent, a cationic surfactant, a stabilizer and water. The breaker comprises an oxidizing agent and the activation composition, which, after being formulated into a breaker fluid with a polymer fracturing fluid, has a gentle viscosity change gradient under the condition of a water bath at 35 DEG C, the viscosity at 3h is reduced to 1.5 mPa.s, the residue content of the breaker fluid after gel breaking is as low as 33.29 mPa.s, the breaker fluid is easy to flow back after pressure after high-efficiency gel breaking, and the damage to the reservoir is reduced.

Description

Technical Field

[0001] This invention belongs to the field of fracturing fluid breaker technology, and particularly relates to an activating composition and a breaker containing the same. Background Technology

[0002] Fracturing is a crucial method in oil extraction, and fracturing fluid is essential for its successful implementation. Ideally, the fracturing fluid should deliver proppant to the reservoir and then be completely drained back to the surface, leaving no impurities between the proppant particles in the formation fractures, allowing unobstructed flow of oil and gas from the reservoir into the wellbore. Breaker plays a vital role in the success of fracturing. After fracturing and sand filling, the fracturing fluid viscosity needs to be reduced, and the hydrated fluid should be drained back. Breakers are typically added to the fracturing fluid along with other fracturing additives and injected into the formation. Their function is to break the molecular chains. Therefore, an ideal breaker needs to maintain the high viscosity of the fracturing fluid during fracturing to achieve proppant carrying capacity, and after fracturing, breaker occurs, reducing the viscosity of the fracturing fluid.

[0003] Fracturing stimulation of low-temperature oil and gas reservoirs has always been one of the major challenges in oil and gas field development. When using conventional water-based fracturing fluid breaker to break the fracturing fluid, the formation temperature limits the effectiveness of post-fracturing fracturing, resulting in high viscosity of the hydrated fluid, low flowback rates, severe formation damage, and poor fracturing results. Traditional methods require increased breaker dosage, which not only increases costs but also easily leads to premature fracturing, causing the fracturing fluid to lose its proppant delivery capacity and resulting in fracturing failure. Since the beginning of the 21st century, my country has made significant progress in the development of special oil and gas reservoirs, achieving some advancements in fracturing fluid breaking technology for low-temperature, shallow oil and gas fields. These advancements mainly include bio-enzyme technology, latent acid technology, and redox technology. Bio-enzyme technology shows good breaking effects at low temperatures but is only suitable for low pH environments. Enzyme activity is affected by various factors such as temperature, pH, and fracturing fluid additives, making it difficult to achieve the expected results. Latent acid technology refers to some organic slow-release acids that slowly release H+ under low formation temperature conditions. + Lowering the pH of fracturing fluid and destroying the gel structure is only suitable for rock formations that do not react with acids, and there may be incompatibility issues with fracturing fluids. Oxidation-reduction technology mainly reduces the activation energy of the oxidation system through the reduction system, enabling the oxidation system to efficiently release free oxygen radicals to destroy the gel structure even at low temperatures. It has strong adaptability and is more valuable for promotion.

[0004] However, current reports on low-temperature breaker based on redox theory still show problems such as unstable breaker performance, high residue content, and low breaker efficiency during indoor testing. Therefore, there is an urgent need to develop a low-temperature breaker with better breaker performance stability, higher breaker efficiency, and lower residue content. Summary of the Invention

[0005] One aspect of the present invention provides an activating composition comprising an inorganic reducing agent, an organic reducing agent, a cationic surfactant, a stabilizer, and water.

[0006] According to one specific embodiment of the present invention, the activation composition comprises 8 wt% to 14 wt% inorganic reducing agent, 2 wt% to 6 wt% organic reducing agent, 3 wt% to 8 wt% cationic surfactant, 1 wt% to 3 wt% stabilizer and the balance being water.

[0007] According to a specific embodiment of the present invention, the inorganic reducing agent is a rhenium salt; and / or

[0008] The organic reducing agent is glucose; and / or

[0009] The cationic surfactant is a long-chain alkyltrimethylammonium chloride; and / or

[0010] The stabilizer is ethylenediaminetetraacetic acid.

[0011] According to one specific embodiment of the present invention, the rhenium salt is a mixture of rhenium sulfate, rhenium nitrate, and rhenium carbonate;

[0012] and / or

[0013] The long-chain alkyltrimethylammonium chloride is dodecyltrimethylammonium chloride and / or hexadecyltrimethylammonium chloride.

[0014] According to one specific embodiment of the present invention, the rhenium salt is 100% by mass, and the rhenium salt comprises 42.8 wt% to 50 wt% rhenium sulfate, 8.3 wt% to 21.5 wt% rhenium nitrate, and 35.7 wt% to 41.7 wt% rhenium carbonate;

[0015] Preferably, the rhenium salt is 100% by mass, and the rhenium salt comprises 42.8 wt% to 50 wt% rhenium sulfate, 12.5 wt% to 21.4 wt% rhenium nitrate and 35.7 wt% to 37.5 wt% rhenium carbonate.

[0016] The second aspect of the present invention provides a desiccant, which comprises an oxidant and an activating composition stored separately;

[0017] The activating composition is the activating composition described in one of the present invention.

[0018] According to one specific embodiment of the present invention, the oxidant is an aqueous solution of persulfate.

[0019] According to one specific embodiment of the present invention, the volume ratio of the persulfate aqueous solution to the activating composition is 1:(1 to 3); and / or

[0020] The persulfate aqueous solution contains 16 wt% to 26 wt% persulfate.

[0021] According to one specific embodiment of the present invention, the persulfate includes ammonium persulfate, sodium persulfate, and potassium persulfate;

[0022] Preferably, the persulfate is 100% by mass, and the persulfate comprises 47.6 wt% to 71.5 wt% ammonium persulfate, 21.7 wt% to 42.2 wt% sodium persulfate, and 4.7 wt% to 14.3 wt% potassium persulfate;

[0023] Preferably, the persulfate is 100% by mass, and the persulfate comprises 57.7 wt% to 62.5 wt% ammonium persulfate, 30.8 wt% to 31.3 wt% sodium persulfate and 6.3 wt% to 11.5 wt% potassium persulfate.

[0024] The application of the activating composition according to one of the present inventions or the breaker according to another of the present invention in fracturing fluid breaker;

[0025] Preferably, the temperature of the application is not higher than 40°C.

[0026] In practical applications, the concentration of the breaker provided by this invention in the fracturing fluid can be adjusted according to the actual reservoir temperature and real-time fracturing fluid viscosity of the low-temperature oil and gas reservoir to control the breaker efficiency. For example, at 35°C, if the total mass of the water-based polymer fracturing fluid is taken as 100%, and the concentration of the emulsion thickener in the water-based polymer fracturing fluid is 0.1wt% to 0.2wt%, the amount of the breaker provided by this invention added is 0.1wt% to 0.2wt% of the total mass of the water-based polymer fracturing fluid. 2wt%; when the concentration of the emulsion thickener in the water-based polymer fracturing fluid is 0.2wt% to 0.3wt%, the amount of the breaker provided by the present invention is 0.15wt% to 0.18wt% of the total mass of the water-based polymer fracturing fluid; when the concentration of the emulsion thickener in the water-based polymer fracturing fluid is 0.3wt% to 0.45wt%, the amount of the breaker provided by the present invention is 0.2wt% to 0.3wt% of the total mass of the water-based polymer fracturing fluid.

[0027] The emulsion thickener referred to in this invention is an emulsion thickener with polyacrylamide as the main component.

[0028] The beneficial effects of this invention are:

[0029] To address the problems of unstable debonding performance, high residue content, and low debonding efficiency of existing low-temperature (specifically, not higher than 40°C) debonding agents, this invention provides an activating composition and a debonding agent containing the same. The activating composition comprises an inorganic reducing agent, an organic reducing agent, a cationic surfactant, a stabilizer, and water. The debonding agent comprises an oxidant and the activating composition. In the activating composition, the cationic surfactant, organic reducing agent, and inorganic reducing agent exhibit synergistic effects, resulting in extremely strong reducing properties. In the breaker, when the activating composition is mixed with the oxidant, a strong catalytic oxidation reaction effect can be ensured, achieving efficient breaker breaking. The stabilizer in the activating composition has a delaying effect, which can slow down the oxidation reaction rate during the breaker breaking process, resulting in a slow decrease in the viscosity of the breaker fluid and good sand carrying capacity. After the breaker breaking is completed, the viscosity of the breaker fluid is significantly reduced, which is beneficial to increase post-fracturing flowback and reduce reservoir damage. The breaker fluid prepared by the breaker provided by this invention and the polymer fracturing fluid under the water bath conditions of 35°C shows little viscosity change within 0 to 1 hour, a gradual viscosity change gradient within 3 hours, and a viscosity reduction to 1.5 mPa·s at 3 hours, with a viscosity reduction rate of 96%. The residue content of the breaker fluid after breaker breaking is as low as 33.29 mPa·s. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0031] Example 1

[0032] Activating composition:

[0033] 8.0 g of dodecyltrimethylammonium chloride was added to 69.0 g of distilled water, heated to approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 6.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 3.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 5.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 6.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 3.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0034] Demolder:

[0035] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 8.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 3.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0036] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 100 mL of the activating composition prepared in this embodiment, stored separately.

[0037] Example 2

[0038] Activating composition:

[0039] 8.0 g of dodecyltrimethylammonium chloride was added to 71.0 g of distilled water, heated at approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 6.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 1.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 5.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 6.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 3.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0040] Demolder:

[0041] Add 15.0g of ammonium persulfate to 77.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 5.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 3.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0042] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 100 mL of the activating composition prepared in this embodiment, stored separately.

[0043] Example 3

[0044] Activating composition:

[0045] 8.0 g of dodecyltrimethylammonium chloride was added to 75.0 g of distilled water, heated to approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 5.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 2.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 4.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 5.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 1.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0046] Demolder:

[0047] Add 10.0g of ammonium persulfate to 79.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 8.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 3.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0048] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 200 mL of the activating composition prepared in this embodiment, stored separately.

[0049] Example 4

[0050] Activating composition:

[0051] 6.0 g of dodecyltrimethylammonium chloride was added to 78.0 g of distilled water, heated to approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 5.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 2.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 4.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 4.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 1.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0052] Demolder:

[0053] Add 10.0g of ammonium persulfate to 81.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 8.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 1.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0054] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 200 mL of the activating composition prepared in this embodiment, stored separately.

[0055] Example 5

[0056] Activating composition:

[0057] 8.0 g of dodecyltrimethylammonium chloride was added to 74.0 g of distilled water, heated to approximately 45 °C and stirred for 20 minutes. After cooling, a first solution was obtained. 5.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 2.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 4.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 4.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 3.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0058] Demolder:

[0059] Add 15.0g of ammonium persulfate to 79.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 5.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 1.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0060] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 300 mL of the activating composition prepared in this embodiment, stored separately.

[0061] Example 6

[0062] Activating composition:

[0063] 3.0 g of dodecyltrimethylammonium chloride was added to 86.0 g of distilled water, heated to approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 4.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 1.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 3.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 2.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 1.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0064] Demolder:

[0065] Add 10.0g of ammonium persulfate to 84.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 5.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 1.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0066] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 300 mL of the activating composition prepared in this embodiment, stored separately.

[0067] Example 7

[0068] Activating composition:

[0069] 8.0 g of hexadecyltrimethylammonium chloride was added to 69.0 g of distilled water, heated to approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 6.0 g of rhenium sulfate was added to the first solution, and the mixture was stirred for 10 minutes to obtain a second solution. 3.0 g of rhenium nitrate was added to the second solution, and the mixture was stirred for 10 minutes to obtain a third solution. 5.0 g of rhenium carbonate was added to the third solution, and the mixture was stirred for 10 minutes to obtain a fourth solution. 6.0 g of glucose was added to the fourth solution, and the mixture was stirred for 20 minutes to obtain a fifth solution. 3.0 g of ethylenediaminetetraacetic acid was added to the fifth solution, and the mixture was stirred for 20 minutes to obtain the activated composition.

[0070] Demolder:

[0071] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 8.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 3.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0072] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 100 mL of the activating composition prepared in this embodiment, stored separately.

[0073] Example 8

[0074] Activating composition:

[0075] 5.0 g of dodecyltrimethylammonium chloride and 3.0 g of hexadecyltrimethylammonium chloride were sequentially added to 69.0 g of distilled water, heated at approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 6.0 g of rhenium sulfate was added to the first solution and stirred for 10 minutes to obtain a second solution. 3.0 g of rhenium nitrate was added to the second solution and stirred for 10 minutes to obtain a third solution. 5.0 g of rhenium carbonate was added to the third solution and stirred for 10 minutes to obtain a fourth solution. 6.0 g of glucose was added to the fourth solution and stirred for 20 minutes to obtain a fifth solution. 3.0 g of ethylenediaminetetraacetic acid was added to the fifth solution and stirred for 20 minutes to obtain the activated composition.

[0076] Demolder:

[0077] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the sixth solution; add 8.0g of sodium persulfate to the sixth solution and stir for 10 minutes to obtain the seventh solution; add 3.0g of potassium persulfate to the seventh solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0078] The de-gelling agent provided in this embodiment includes 100 mL of the oxidant aqueous solution prepared in this embodiment and 100 mL of the activating composition prepared in this embodiment, stored separately.

[0079] Comparative Example 1

[0080] Demolder:

[0081] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the first solution; add 8.0g of sodium persulfate to the first solution and stir for 10 minutes to obtain the second solution; add 3.0g of potassium persulfate to the second solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0082] The desiccant provided in this comparative example is 100 mL of the oxidant aqueous solution prepared in this comparative example.

[0083] Comparative Example 2

[0084] Activating composition:

[0085] Add 6.0 g of rhenium sulfate to 77.0 g of distilled water and stir for 10 minutes to obtain the first solution; add 3.0 g of rhenium nitrate to the first solution and stir for 10 minutes to obtain the second solution; add 5.0 g of rhenium carbonate to the second solution and stir for 10 minutes to obtain the third solution; add 6.0 g of glucose to the third solution and stir for 20 minutes to obtain the fourth solution; add 3.0 g of ethylenediaminetetraacetic acid to the fourth solution and stir for 20 minutes to obtain the activated composition.

[0086] Demolder:

[0087] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the fifth solution; add 8.0g of sodium persulfate to the fifth solution and stir for 10 minutes to obtain the sixth solution; add 3.0g of potassium persulfate to the sixth solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0088] The breaker provided in this comparative example comprises 100 mL of the oxidant aqueous solution prepared in this comparative example and 100 mL of the activating composition prepared in this comparative example, stored separately.

[0089] Comparative Example 3

[0090] Activating composition:

[0091] Add 6.0g rhenium sulfate to 80.0g distilled water and stir for 10 minutes to obtain the first solution; add 3.0g rhenium nitrate to the first solution and stir for 10 minutes to obtain the second solution; add 5.0g rhenium carbonate to the second solution and stir for 10 minutes to obtain the third solution; add 6.0g glucose to the third solution and stir for 20 minutes to obtain the activated composition.

[0092] Demolder:

[0093] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the fourth solution; add 8.0g of sodium persulfate to the fourth solution and stir for 10 minutes to obtain the fifth solution; add 3.0g of potassium persulfate to the fifth solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0094] The breaker provided in this comparative example comprises 100 mL of the oxidant aqueous solution prepared in this comparative example and 100 mL of the activating composition prepared in this comparative example, stored separately.

[0095] Comparative Example 4

[0096] Activating composition:

[0097] 8.0 g of dodecyltrimethylammonium chloride was added to 72.0 g of distilled water, heated to approximately 45°C and stirred for 20 minutes. After cooling, a first solution was obtained. 6.0 g of rhenium sulfate was added to the first solution and stirred for 10 minutes to obtain a second solution. 3.0 g of rhenium nitrate was added to the second solution and stirred for 10 minutes to obtain a third solution. 5.0 g of rhenium carbonate was added to the third solution and stirred for 10 minutes to obtain a fourth solution. 6.0 g of glucose was added to the fourth solution and stirred for 20 minutes to obtain the activated composition.

[0098] Demolder:

[0099] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the fifth solution; add 8.0g of sodium persulfate to the fifth solution and stir for 10 minutes to obtain the sixth solution; add 3.0g of potassium persulfate to the sixth solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0100] The breaker provided in this comparative example comprises 100 mL of the oxidant aqueous solution prepared in this comparative example and 100 mL of the activating composition prepared in this comparative example, stored separately.

[0101] Comparative Example 5

[0102] Activating composition:

[0103] Add 8.0 g of dodecyltrimethylammonium chloride to 89.0 g of distilled water, heat at about 45°C and stir for 20 minutes, then cool to obtain the first solution; add 3.0 g of ethylenediaminetetraacetic acid to the first solution and stir for 20 minutes to obtain the activated composition;

[0104] Demolder:

[0105] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the second solution; add 8.0g of sodium persulfate to the second solution and stir for 10 minutes to obtain the third solution; add 3.0g of potassium persulfate to the third solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0106] The breaker provided in this comparative example comprises 100 mL of the oxidant aqueous solution prepared in this comparative example and 100 mL of the activating composition prepared in this comparative example, stored separately.

[0107] Comparative Example 6

[0108] Activating composition:

[0109] Add 8.0 g of dodecyltrimethylammonium chloride to 83.0 g of distilled water, heat at about 45°C and stir for 20 minutes, then cool to obtain the first solution; add 6.0 g of glucose to the first solution and stir for 20 minutes to obtain the second solution; add 3.0 g of ethylenediaminetetraacetic acid to the second solution and stir for 20 minutes to obtain the activated composition;

[0110] Demolder:

[0111] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the third solution; add 8.0g of sodium persulfate to the third solution and stir for 10 minutes to obtain the fourth solution; add 3.0g of potassium persulfate to the fourth solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0112] The breaker provided in this comparative example comprises 100 mL of the oxidant aqueous solution prepared in this comparative example and 100 mL of the activating composition prepared in this comparative example, stored separately.

[0113] Comparative Example 7

[0114] Activating composition:

[0115] 8.0 g of dodecyltrimethylammonium chloride was added to 75.0 g of distilled water, heated and stirred at approximately 45°C for 20 minutes, and cooled to obtain the first solution. 6.0 g of rhenium sulfate was added to the first solution, and stirred for 10 minutes to obtain the second solution. 3.0 g of rhenium nitrate was added to the second solution, and stirred for 10 minutes to obtain the third solution. 5.0 g of rhenium carbonate was added to the third solution, and stirred for 10 minutes to obtain the fourth solution. 3.0 g of ethylenediaminetetraacetic acid was added to the fourth solution, and stirred for 20 minutes to obtain the activated composition.

[0116] Demolder:

[0117] Add 15.0g of ammonium persulfate to 74.0g of distilled water and stir for 10 minutes to obtain the fifth solution; add 8.0g of sodium persulfate to the fifth solution and stir for 10 minutes to obtain the sixth solution; add 3.0g of potassium persulfate to the sixth solution and stir for 10 minutes to obtain the oxidizing agent aqueous solution.

[0118] The breaker provided in this comparative example comprises 100 mL of the oxidant aqueous solution prepared in this comparative example and 100 mL of the activating composition prepared in this comparative example, stored separately.

[0119] Evaluation of the breaking performance of the breaker

[0120] The breaker prepared in Examples 1 to 8 and Comparative Examples 1 to 7 were used to conduct polymer fracturing fluid breaker experiments. The breaker performance was evaluated by measuring the viscosity change of the breaker at different experimental times and the content of breaker residue after the experiment.

[0121] The emulsion thickener used in the experiment was purchased from Dongying Shipuri Petroleum Engineering Technology Co., Ltd., and its product name is emulsion thickener.

[0122] The specific steps are as follows:

[0123] i. Preparation of polymer fracturing fluid: Weigh 5000g of distilled water and place it in the mixing tank. Turn on the electric stirrer and slowly add 22.5g of emulsion thickener to the continuously stirred distilled water until fully dissolved and homogeneous to obtain polymer fracturing fluid.

[0124] ii. Preparation of breaker fluid: Weigh 15 portions of polymer fracturing fluid (300g each) and add them to 15 graduated beakers of equal size. Then weigh 0.9g of the breaker prepared in Examples 1 to 8 and Comparative Examples 1 to 7 and add them to the beakers containing polymer fracturing fluid to obtain 15 groups of breaker fluids. In each group of breaker fluids, the mass of the breaker accounts for 0.3wt% of the mass of the polymer fracturing fluid.

[0125] iii. First, the initial viscosity of the 15 groups of gel breaking solutions prepared in step ii was measured and recorded at room temperature using a ZNN-D6B electric six-speed rotational viscometer. Then, all beakers containing gel breaking solutions were immediately placed in a 35°C water bath for heating and gel breaking experiments. The viscosity of the gel breaking solution was measured and recorded every 0.5 hours, and the total experimental time was 3 hours.

[0126] iv. When the experiment time reaches 3 hours, the viscosity of the rupture liquid in each beaker is measured and recorded. After the experiment ends, all beakers containing the rupture liquid are removed from the water bath and cooled to room temperature. The volume of the rupture liquid in each beaker is recorded. Then, the rupture liquid in the beaker is filtered, the filter residue is collected, and it is dried to constant weight in a GW-50B high-temperature test chamber at 105℃ and weighed. The content of residue in the rupture liquid is calculated (specifically, the mass of residue per liter of rupture liquid). The specific results are shown in Table 1.

[0127] Table 1. Debriding performance of the debriding agent

[0128]

[0129] As shown in Table 1, the viscosity of the fracturing fluid containing the fracturing agents prepared in Examples 1 to 8 exhibited a gradual viscosity change every 0.5 hours during the experiment, with minimal viscosity change within 0 to 1 hour. The inventors believe this is because the oxidant in the fracturing agent was affected by the stabilizer in the activating composition, resulting in a slower reaction rate and a slower viscosity decrease. In practical applications, a relatively gradual viscosity change gradient is beneficial for ensuring good sand-carrying capacity of the fracturing fluid during construction. After 3 hours of experimentation, the viscosity of the fracturing fluid containing the fracturing agents prepared in Examples 1 to 8 decreased to 1.5 mPa·s, a 96.4% decrease compared to the viscosity before the experiment. The residue content in the fracturing fluid ranged from 33.29 mg to 56.17 mg, indicating that the oxidant in the fracturing agent underwent an oxidation reaction under the action of the activating composition, resulting in complete fracturing. The lower viscosity and less residue content after fracturing can effectively improve the flowback rate after fracturing and reduce the residue of fracturing fluid in the reservoir, thereby reducing reservoir damage. Combining the formulation analysis of Example 1 and Comparative Examples 1 to 7: Compared with Example 1, Comparative Example 1 only contained an aqueous oxidant solution and lacked an activating composition. It can be seen that the viscosity of the breaker solution with Comparative Example 1 added showed a very low decrease within 3 hours, with a viscosity reduction rate of only 14.3% at 3 hours. Furthermore, the residue content in the breaker solution after the experiment was as high as 354.23 mg / L, indicating that the aqueous oxidant solution alone could not achieve the purpose of breaker breaking. Compared with Example 1, the activating composition in Comparative Example 2 lacked a cationic surfactant, and Comparative Example 5 lacked both an organic reducing agent and an inorganic reducing agent. The viscosities of the breaker solutions with Comparative Examples 2 and 5 added at 3 hours were 9 mPa·s and 36 mPa·s, respectively, and the residue contents in the breaker solutions were 92.56 mPa·s and 298.55 mPa·s, respectively. The viscosity and residue content in the breaker solutions at 3 hours were significantly higher than those of the breaker solutions with Comparative Examples 2 and 5. The rupture solution prepared by Example 1 demonstrates that the cationic surfactant, organic reducing agent, and inorganic reducing agent in the activating composition synergistically enhance the rupture ability of the rupture agent and reduce the residue content in the rupture solution. Comparative analysis of Comparative Example 3 and Comparative Example 4 reveals that the activating composition of Comparative Example 4 lacks a stabilizer but still contains a cationic surfactant, organic reducing agent, and inorganic reducing agent. The rupture solution containing these components exhibits a rapid decrease in viscosity and a fast reaction rate during the experiment. In contrast, the activating composition of Comparative Example 3 lacks both a cationic surfactant and a stabilizer, containing only organic and inorganic reducing agents. The rupture solution containing these components shows a significantly slower decrease in viscosity during the experiment compared to Comparative Example 4. This indicates that the reaction rate of Comparative Example 3 during the rupture process is slower than that of Comparative Example 4, further demonstrating the synergistic effect between the cationic surfactant, organic reducing agent, and inorganic reducing agent, resulting in a stronger rupture performance of the rupture agent.Compared to Example 1, the activation composition in Comparative Example 4 lacked a stabilizer. During the experiment, the viscosity gradient of the breaker solution with the breaker prepared in Comparative Example 4 was significantly larger than that with the breaker prepared in Example 1. The excessively rapid viscosity decrease during the experiment indicates that without a stabilizer, there is no delay effect, and the breaker undergoes an excessively rapid oxidation reaction, leading to a rapid viscosity decrease. This is not conducive to maintaining the sand-carrying capacity of the breaker solution during construction. Furthermore, the residue content in its breaker solution is approximately twice that of Example 1, which is also detrimental to post-pressurization flowback and reducing reservoir damage. Compared to Example 1, the activation composition in Comparative Example 3 lacked a cationic surfactant and a stabilizer. The viscosity of the breaker solution with the breaker prepared in Comparative Example 3 was slightly higher than that with the breaker prepared in Example 1. After the experiment, the residue content in its breaker solution was also high, which is also detrimental to post-pressurization flowback and reducing reservoir damage. Compared to Example 1, the activator composition in Comparative Example 6 lacked an inorganic reducing agent. During the experiment, the viscosity decrease of the breaker solution with the breaker prepared in Comparative Example 6 was smaller, failing to achieve the purpose of breaker breaking. Compared to Example 1, the activator composition in Comparative Example 7 lacked an organic reducing agent. During the experiment, the viscosity change gradient of the breaker solution with the breaker prepared in Comparative Example 7 was slightly smaller than that with the breaker prepared in Example 1, but the residue content was significantly higher than that in Example 1, which is not conducive to post-pressurization flowback and causes greater damage to the reservoir. In summary, the activator composition and the breaker containing the activator composition provided by the present invention can ensure a strong catalytic oxidation reaction effect, achieve efficient breaker breaking while maintaining a slow decrease in the viscosity of the breaker solution, and after breaker breaking, the viscosity of the breaker solution is greatly reduced with less residue, which can increase post-pressurization flowback and reduce reservoir damage. The lack of any one of the stabilizer, cationic surfactant, inorganic reducing agent, or organic reducing agent in the activation composition provided by the present invention will affect the technical effect of the activation composition, thereby making it impossible for the breaker containing the activation composition lacking the raw materials to achieve efficient breakering with easy pressure return and low reservoir damage.

[0130] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. An activating composition comprising an inorganic reducing agent, an organic reducing agent, a cationic surfactant, a stabilizer and water; the inorganic reducing agent is a rhenium salt; the organic reducing agent is glucose; the cationic surfactant is long-chain alkyl trimethyl ammonium chloride; the stabilizer is ethylenediaminetetraacetic acid; the activating composition is used in combination with an oxidizing agent, and the oxidizing agent is an aqueous solution of persulfate.

2. The activating composition of claim 1, wherein, The activating composition comprises 8wt% to 14wt% of the inorganic reducing agent, 2wt% to 6wt% of the organic reducing agent, 3wt% to 8wt% of the cationic surfactant, 1wt% to 3wt% of the stabilizer and the balance of water, based on 100% by mass of the activating composition.

3. The activating composition of claim 1, wherein, the rhenium salt is a mixture of rhenium sulfate, rhenium nitrate and rhenium carbonate; and / or the long-chain alkyl trimethyl ammonium chloride is dodecyl trimethyl ammonium chloride and / or hexadecyl trimethyl ammonium chloride.

4. The activating composition of claim 3, wherein, The rhenium salt comprises 42.8wt% to 50wt% of rhenium sulfate, 8.3wt% to 21.5wt% of rhenium nitrate and 35.7wt% to 41.7wt% of rhenium carbonate, based on 100% by mass of the rhenium salt.

5. The activating composition of claim 1, wherein, The volume ratio of the aqueous solution of persulfate to the activating composition is 1: (1 to 3). 6.A breaker comprising an oxidizing agent and an activating composition separately stored. The activating composition is the activating composition according to any one of claims 1 to 5.

7. The gel breaker of claim 6, wherein, The oxidizing agent is an aqueous solution of persulfate.

8. The gel breaker of claim 7, wherein, The volume ratio of the aqueous solution of persulfate to the activating composition is 1: (1 to 3) ; and / or The content of the persulfate in the aqueous solution of persulfate is 16wt% to 26wt%.

9. The gel breaker of claim 8, wherein, The persulfate comprises ammonium persulfate, sodium persulfate and potassium persulfate.

10. The gel breaker of claim 9, wherein, The persulfate comprises 47.6wt% to 71.5wt% of ammonium persulfate, 21.7wt% to 42.2wt% of sodium persulfate and 4.7wt% to 14.3wt% of potassium persulfate, based on 100% by mass of the persulfate. 11.Use of the activating composition according to any one of claims 1 to 5 or the breaker according to any one of claims 6 to 10 in gel breaking of a fracturing fluid.

12. Use according to claim 11, characterized in that, The temperature of the use is not higher than 40℃.

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