Multifunctional integrated clean fracturing fluid for deep coal bed gas and preparation method of multifunctional integrated clean fracturing fluid

Abstract

The invention discloses a multifunctional integrated clean fracturing fluid for deep coal bed gas and a preparation method of the multifunctional integrated clean fracturing fluid, and the fracturing fluid is prepared from the following raw materials in percentage by weight: 0.1-0.5% of a clean thickening agent, 0.3-0.5% of a pulverized coal dispersing agent, 0.2-0.5% of a cleat penetrant, 0.5-1.0% of an antioxidant and the balance of water, wherein the pulverized coal dispersing agent is formed by mixing alkylphenol polyoxyethylene ether, fatty alcohol-polyoxyethylene ether, carboxyl polyether modified silicone oil and deionized water; the antioxidant is formed by mixing one of ascorbic acid or sodium sulfite, carboxyl polyether modified silicone oil and deionized water. The coal powder fracturing fluid has the advantages of low friction resistance, coagulation prevention, strong permeability and oxidation resistance, can meet large-displacement construction, can uniformly disperse coal powder in the fracturing fluid, changes the hydrophobic property of coal rock, and improves the permeability of the fracturing fluid.

Description

Technical Field

[0001] The present invention belongs to the technical field of fracturing fluids, and in particular relates to a multifunctional integrated clean fracturing fluid for deep coalbed methane and a preparation method thereof. Background Art

[0002] In recent years, deep coalbed methane production in the eastern margin of the Ordos Basin has surpassed 2,000 meters in depth, achieving industrial production capacity. Recognizing that deep coalbed methane could be a commercially viable natural gas resource, following breakthroughs in the Daning-Jixian region, technical exploration and process trials have been conducted in areas such as Jiaxian South, Shenfu, Wushen Banner, Daniudi, Yichuan, Yanchang, and Yanchuan South in the Ordos Basin, all resulting in high-yield gas flows.

[0003] Hydraulic fracturing is a preferred and effective method for increasing production in deep coalbed methane (CBM). With advances in large-scale volume fracturing technology, the effectiveness of deep CBM transformation has been continuously improved, initially achieving profitable development of deep CBM. Deep CBM is characterized by low pressure, low porosity, low permeability, and multiple cleats. Currently, the main method for improving transformation effectiveness is to use large amounts of fracturing fluid to open multiple cleat fractures. However, during hydraulic flushing, the proppant abrasion and the formation of large amounts of coal dust within the coal seam occur simultaneously. Based on geological data and engineering practice, low-viscosity fracturing fluids present difficulties in adding sand, while high-viscosity fracturing fluids are difficult to break, causing significant damage to the reservoir. Coal dust easily aggregates and settles, causing pump blockage. Furthermore, fracturing fluids have poor permeability, preventing adsorbed gas from penetrating deep pores. Therefore, providing a clean fracturing fluid suitable for deep CBM is of great significance. Summary of the Invention

[0004] In response to the defects of the prior art, the present invention provides a deep coalbed methane multifunctional integrated clean fracturing fluid and a preparation method thereof. The fracturing fluid has the characteristics of low friction, prevention of coal powder accumulation, strong permeability and anti-oxidation. The low friction characteristic can solve the problem of reducing construction pressure during fracturing construction, the prevention of coal powder accumulation solves the problem of coal powder accumulation and pump jamming during the backflow process, the strong permeability characteristic can solve the problem of strong filtration loss of fracturing fluid and increased permeability of cleat cracks, and the anti-oxidation characteristic can solve the problem of iron powder blockage caused by oxidation of pyrite. This system has a multifunctional integrated function.

[0005] A multifunctional integrated clean fracturing fluid for deep coalbed methane, the fracturing fluid comprising the following raw materials in a 100% by weight ratio: 0.1-0.5% clean thickener, 0.3-0.5% coal powder dispersant, 0.2-0.5% cleat penetrant, 0.5-1.0% antioxidant, and the balance being water; The coal powder dispersant is composed of a mixture of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, carboxyl polyether modified silicone oil and deionized water; The antioxidant is composed of a mixture of ascorbic acid or sodium sulfite, carboxyl polyether modified silicone oil and deionized water.

[0006] Preferably, the carboxyl polyether modified silicone oil is prepared by the following method: hydrogenated silicone oil, polyether and acrylic acid are mixed, nitrogen is introduced for 1.5-2 hours, the temperature is raised to 85-90°C, a Pt catalyst is added, the reaction is carried out at room temperature for 6-7 hours, and acrylic acid is removed by reduced pressure distillation to obtain the carboxyl polyether modified silicone oil.

[0007] Preferably, based on the total weight of the hydrogen-containing silicone oil, polyether and acrylic acid being 100%, the weight ratio of each component is as follows: 40-50% hydrogen-containing silicone oil, 20-30% polyether and 20-40% acrylic acid; the weight of the catalyst Pt is 1% of the total weight of the hydrogen-containing silicone oil, polyether and acrylic acid.

[0008] Preferably, based on 100% by weight of the coal powder dispersant, the weight ratios of the components are as follows: 5-25% of alkylphenol polyoxyethylene ether, 10-25% of fatty alcohol polyoxyethylene ether, 30-40% of carboxyl polyether modified silicone oil, and the balance of deionized water.

[0009] Preferably, based on 100% by weight of the antioxidant, the weight ratios of the components are as follows: 20-30% ascorbic acid or sodium sulfite, 20-30% carboxyl polyether modified silicone oil, and the balance deionized water.

[0010] Preferably, the cleaning thickener is cationic polyacrylamide or nonionic polyacrylamide.

[0011] Preferably, the viscosity-average molecular weight of the cleaning thickener is greater than or equal to 8 million.

[0012] Preferably, the cleat penetrant is a mixture of linear sodium alkylbenzene sulfonate, secondary sodium alkylbenzene sulfonate and deionized water.

[0013] Preferably, based on 100% by weight of the cleat penetrant, the weight ratios of the components are as follows: 25-30% of sodium linear alkylbenzene sulfonate, 20-25% of sodium secondary alkyl sulfonate, and the balance of deionized water.

[0014] Preferably, the antioxidant is a mixture of one selected from carboxyl polyether modified silicone oil, ascorbic acid or sodium sulfite and water.

[0015] Preferably, the weight ratio of the antioxidant is 100%, and the weight ratios of the components are as follows: 20-30% carboxyl polyether modified silicone oil, 20-30% ascorbic acid or 20-30% sodium sulfite, and the balance water.

[0016] A preparation method of a multifunctional integrated clean fracturing fluid for deep coalbed methane is as follows: adding a clean thickener to water, stirring evenly, then adding a coal powder dispersant, stirring evenly, then adding a cleat penetrant, stirring evenly, then adding an antioxidant, and stirring evenly.

[0017] The viscosity of the deep coalbed methane multifunctional integrated clean fracturing fluid prepared by the present invention is 10-120 mPa.s.

[0018] Advantages of the present invention: The present invention introduces a thickener, a dispersant containing carboxyl polyether silicone oil, a penetrant and an antioxidant to compound a fracturing fluid with low friction, anti-coagulation, strong penetration and oxidation resistance. The present invention can meet the needs of large-volume construction, can evenly disperse coal powder in the fracturing fluid, and prevent coal powder from agglomerating into clumps and getting stuck in the pump after migration; can change the hydrophobic properties of coal rock, improve the permeability of the fracturing fluid, and prevent pyrite in the coal seam from being oxidized. The present invention overcomes the problems of high construction friction, easy sedimentation of coal powder, low penetration efficiency and easy clogging by iron powder in existing fracturing fluids when used for deep coalbed methane. DETAILED DESCRIPTION

[0019] Example 1 A multifunctional integrated clean fracturing fluid for deep coalbed methane, the fracturing fluid comprising the following raw materials in the following weight ratios, based on a 100% weight ratio: 0.1% clean thickener, 0.5% coal powder dispersant, 0.5% cleat penetrant, 1.0% antioxidant, and 97.9% water; Wherein, the cleaning thickener is cationic polyacrylamide with a viscosity average molecular weight of 12 million; The cleat penetrant is composed of a mixture of 25 wt% linear sodium alkylbenzene sulfonate, 25 wt% secondary sodium alkyl sulfonate, and 50 wt% water; The coal powder dispersant is composed of a mixture of 10 wt% of alkylphenol polyoxyethylene ether, 10 wt% of fatty alcohol polyoxyethylene ether, 30 wt% of carboxyl polyether modified silicone oil and 50 wt% of deionized water; The antioxidant is composed of a mixture of 20 wt% ascorbic acid, 30 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water; The carboxyl polyether modified silicone oil is prepared by the following method: 40 wt% of hydrogenated silicone oil, 20 wt% of polyether, and 40 wt% of acrylic acid are mixed, nitrogen is introduced for 2 hours, the temperature is raised to 90° C., a catalyst Pt is added, and the weight of the catalyst Pt is 1% of the total weight of the hydrogenated silicone oil, polyether, and acrylic acid. The mixture is kept warm for 6 hours under normal pressure, and the acrylic acid is removed by reduced pressure distillation to obtain the carboxyl polyether modified silicone oil. The preparation method of the multifunctional integrated clean fracturing fluid for deep coalbed methane is as follows: adding a clean thickener to water, stirring evenly, then adding a coal powder dispersant, stirring evenly, then adding a cleat penetrant, stirring evenly, then adding an antioxidant, and stirring evenly. The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 20 mPa.s.

[0020] Example 2 A multifunctional integrated clean fracturing fluid for deep coalbed methane, the fracturing fluid comprising the following raw materials in the following weight ratios, based on a 100% weight ratio: 0.5% clean thickener, 0.3% coal powder dispersant, 0.2% cleat penetrant, 1.0% antioxidant, and 98% water; Wherein, the cleaning thickener is non-ionic polyacrylamide with a viscosity average molecular weight of 12 million; The cleat penetrant is composed of a mixture of 30 wt% linear sodium alkylbenzene sulfonate, 20 wt% secondary sodium alkyl sulfonate, and 50 wt% water; The coal powder dispersant is composed of a mixture of 5wt% of alkylphenol polyoxyethylene ether, 10wt% of fatty alcohol polyoxyethylene ether, 40wt% of carboxyl polyether modified silicone oil and 45wt% of deionized water; The antioxidant is composed of a mixture of 20 wt% sodium sulfite, 30 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water; The carboxyl polyether modified silicone oil is the same as that in Example 1; The preparation method of the multifunctional integrated clean fracturing fluid for deep coalbed methane is the same as that in Example 1; The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 65 mPa.s.

[0021] Example 3 A multifunctional integrated clean fracturing fluid for deep coalbed methane, the fracturing fluid comprising the following raw materials in the following weight ratios, based on a 100% weight ratio: 0.5% clean thickener, 0.4% coal powder dispersant, 0.5% cleat penetrant, 0.5% antioxidant, and 98.1% water; Wherein, the cleaning thickener is non-ionic polyacrylamide with a viscosity average molecular weight of 12 million; The cleat penetrant is composed of a mixture of 28 wt% of linear sodium alkylbenzene sulfonate, 22 wt% of secondary sodium alkyl sulfonate, and 50 wt% of water; The coal powder dispersant is composed of a mixture of 25 wt% of alkylphenol polyoxyethylene ether, 25 wt% of fatty alcohol polyoxyethylene ether, 35 wt% of carboxyl polyether modified silicone oil and 15 wt% of deionized water; The antioxidant is composed of a mixture of 30 wt% sodium sulfite, 20 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water; The carboxyl polyether modified silicone oil is the same as that in Example 1; The preparation method of the multifunctional integrated clean fracturing fluid for deep coalbed methane is the same as that in Example 1; The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 55 mPa.s.

[0022] Example 4 A multifunctional integrated clean fracturing fluid for deep coalbed methane, the fracturing fluid comprising the following raw materials in the following weight ratios, based on a 100% weight ratio: 0.1% clean thickener, 0.4% coal powder dispersant, 0.3% cleat penetrant, 0.8% antioxidant, and 98.4% water; Wherein, the cleaning thickener is cationic polyacrylamide with a viscosity average molecular weight of 12 million; The cleat penetrant is composed of a mixture of 30 wt% linear sodium alkylbenzene sulfonate, 20 wt% secondary sodium alkyl sulfonate, and 50 wt% water; The coal powder dispersant is composed of a mixture of 10 wt% of alkylphenol polyoxyethylene ether, 10 wt% of fatty alcohol polyoxyethylene ether, 40 wt% of carboxyl polyether modified silicone oil and 40 wt% of deionized water; The antioxidant is composed of a mixture of 25 wt% sodium sulfite, 25 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water; The carboxyl polyether modified silicone oil is prepared by the following method: 50 wt% of hydrogenated silicone oil, 30 wt% of polyether, and 20 wt% of acrylic acid are mixed, nitrogen is introduced for 1.5 hours, the temperature is raised to 85° C., a catalyst Pt is added, and the weight of the catalyst Pt is 1% of the total weight of the hydrogenated silicone oil, polyether, and acrylic acid. The mixture is kept warm for 7 hours under normal pressure, and the acrylic acid is removed by reduced pressure distillation to obtain the carboxyl polyether modified silicone oil. The preparation method of the multifunctional integrated clean fracturing fluid for deep coalbed methane is the same as that in Example 1; The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 18 mPa.s.

[0023] Comparative Example 1 Compared with Example 1, the coal powder dispersant and antioxidant do not contain carboxyl polyether modified silicone oil. The coal powder dispersant is composed of a mixture of 10 wt% of alkylphenol polyoxyethylene ether, 10 wt% of fatty alcohol polyoxyethylene ether and 80 wt% of deionized water; The antioxidant is composed of a mixture of 20 wt% ascorbic acid and 80 wt% deionized water; Other aspects are the same as in Example 1; The viscosity of the prepared fracturing fluid is 16 mPa.s.

[0024] Comparative Example 2 The carboxyl polyether modified silicone oil in the coal powder dispersant and the antioxidant was replaced by polyether silicone oil, and the rest was the same as in Example 1; the viscosity of the prepared fracturing fluid was 19 mPa·s.

[0025] Comparative Example 3 The carboxyl polyether modified silicone oil in the coal powder dispersant and the antioxidant was replaced by polyoxyethylene ether, and the rest was the same as in Example 1; the viscosity of the prepared fracturing fluid was 21 mPa·s.

[0026] Comparative Example 4 No coal powder dispersant is added, as follows: A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in the following weight ratios, based on a 100% weight ratio: 0.1% clean thickener, 0.5% cleat penetrant, 1.0% antioxidant, and 98.4% water; Other conditions were the same as those in Example 1; the viscosity of the prepared fracturing fluid was 18 mPa·s.

[0027] Comparative Example 5 No antioxidants added, specifically as follows: A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in the following weight ratios: 0.1% clean thickener, 0.5% coal powder dispersant, 0.5% cleat penetrant, and 98.9% water, based on a 100% weight ratio; Other conditions were the same as those in Example 1; the viscosity of the prepared fracturing fluid was 20 mPa·s.

[0028] Performance testing 1. Dispersion ability test The fracturing fluids obtained in Example 1 and Comparative Examples 1-7 were broken with 0.01 wt% persulfate at 80°C for 2 hours to obtain broken liquids. The dispersibility of the broken liquids in deep coalbed methane layers was determined using the suspension method, and the suspension time of the broken liquids in coal was determined using the static sand suspension method. The results are shown in Table 1. Table 1 Dispersion ability test results As can be seen from Table 1, the static settling velocity of the fracturing fluid of the present invention on coal powder is low, and the time required to complete the aggregation is long.

[0029] 2. Static stability test The static stability of coal-water slurry is evaluated by measuring the ability of pulverized coal to resist gravity in the absence of other external forces. At room temperature, the slurry was thoroughly mixed with fracturing fluid and pulverized coal in a volume ratio of 100:70. The static stability of the slurry was tested using the static stability test method specified in GB / T 18856.5-2008, "Test Methods for Coal-Water Slurries - Part 5: Determination of Stability." Results are shown in Table 2. Table 2 Static stability test results .

[0030] 3. Antioxidant Effect Testing Pyrite-bearing coal rock was ground into ultrafine powder with a pyrite content of 5%. 5g of the powder was thoroughly mixed with a fracturing fluid at a mass ratio of 1:20. Nitrogen was introduced for 30 minutes and stirred continuously for 2 hours. The lower sediment was centrifuged and weighed. After drying, the iron precipitate was flotated to determine its amount. The smaller the amount of sediment, the stronger the antioxidant property. The results are shown in Table 3. Table 3 Antioxidant effect test .

[0031] 4. Permeability effect evaluation The smooth surface of the coal rock block, i.e., the natural bedding surface, was selected as the experimental surface. The dynamic contact angle was used to measure the contact angle of the coal rock with different fracturing and gel-breaking fluids after 10 seconds of contact. The smaller the contact angle, the stronger the infiltration, spreading, and penetration effects, as shown in Table 4. Table 4 Test results of contact angle θ between fracturing fluid and coal rock .

Claims

1. A multifunctional integrated clean fracturing fluid for deep coalbed methane, characterized by: The fracturing fluid is composed of the following raw materials based on a weight ratio of 100%: 0.1-0.5% of a cleaning thickener, 0.3-0.5% of a coal powder dispersant, 0.2-0.5% of a cleat penetrant, 0.5-1.0% of an antioxidant, and the balance being water; The coal powder dispersant is composed of a mixture of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, carboxyl polyether modified silicone oil and deionized water; The antioxidant is composed of a mixture of ascorbic acid or sodium sulfite, carboxyl polyether modified silicone oil and deionized water.

2. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The carboxyl polyether modified silicone oil is prepared by the following method: hydrogenated silicone oil, polyether and acrylic acid are mixed, nitrogen is introduced for 1.5-2 hours, the temperature is raised to 85-90°C, a Pt catalyst is added, the reaction is carried out under normal pressure for 6-7 hours, and acrylic acid is removed by reduced pressure distillation to obtain the carboxyl polyether modified silicone oil.

3. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 2, characterized in that: The total weight of the hydrogen-containing silicone oil, polyether and acrylic acid is 100%, and the weight ratio of each component is as follows: 40-50% hydrogen-containing silicone oil, 20-30% polyether, and 20-40% acrylic acid; the weight of the catalyst Pt is 1% of the total weight of the hydrogen-containing silicone oil, polyether and acrylic acid.

4. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The weight of the coal powder dispersant is calculated as 100%, and the weight ratios of the components are as follows: 5-25% of alkylphenol polyoxyethylene ether, 10-25% of fatty alcohol polyoxyethylene ether, 30-40% of carboxyl polyether modified silicone oil, and the balance of deionized water.

5. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The weight of the antioxidant is calculated as 100%, and the weight ratios of the components are as follows: 20-30% of ascorbic acid or sodium sulfite, 20-30% of carboxyl polyether modified silicone oil, and the balance of deionized water.

6. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The cleaning thickener is cationic polyacrylamide or nonionic polyacrylamide.

7. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The viscosity average molecular weight of the cleaning thickener is greater than or equal to 8 million.

8. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The cleat penetrant is a mixture of linear sodium alkylbenzene sulfonate, secondary sodium alkyl sulfonate and deionized water.

9. The multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 8, characterized in that: The weight of the cleat penetrant is calculated based on 100%, and the weight ratios of the components are as follows: 25-30% of sodium linear alkylbenzene sulfonate, 20-25% of sodium secondary alkyl sulfonate, and the balance of deionized water.

10. The method for preparing the multifunctional integrated clean fracturing fluid for deep coalbed methane according to claim 1, characterized in that: The preparation method is specifically as follows: adding a cleaning thickener to water, stirring evenly, then adding a coal powder dispersant, stirring evenly, then adding a cleat penetrant, stirring evenly, then adding an antioxidant, stirring evenly, and the mixture is finished.

Images