Deep coal bed gas multifunctional integrated clean fracturing fluid and preparation method thereof

Abstract

This invention discloses a multifunctional integrated clean fracturing fluid for deep coalbed methane and its preparation method. The fracturing fluid, by weight (100%), comprises the following raw materials: 0.1-0.5% clean thickener, 0.3-0.5% coal powder dispersant, 0.2-0.5% cleavage 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. It has advantages such as low friction, anti-agglomeration, strong penetration, and antioxidant properties, meeting the requirements of high-volume fracturing operations. It enables uniform dispersion of coal powder in the fracturing fluid, alters the hydrophobic properties of coal and rock, and improves the permeability of the fracturing fluid.

Description

Technical Field

[0001] This invention belongs to the field of fracturing fluid technology, specifically relating to a multifunctional integrated clean fracturing fluid for deep coalbed methane and its preparation method. Background Technology

[0002] In recent years, the development of deep coalbed methane at a depth of 2,000 meters in the eastern edge of the Ordos Basin has achieved breakthroughs in industrial production capacity. Recognizing that deep coalbed methane is a natural gas resource that can be commercially developed, and following the breakthrough in the Daning-Jixian area, technological exploration and process trials have been carried out in areas such as Jiaxian South, Shenfu, Wushen Banner, Daniudi, Yichuan, Yanchang, and Yanchuan South in the Ordos Basin, all of which have yielded high-yield gas flows.

[0003] Hydraulic fracturing is a preferred and effective method for enhancing the production of deep coalbed methane. With the advancement of large-scale volumetric fracturing technology, the effectiveness of deep coalbed methane stimulation has been increasingly improved, initially realizing the economical development of deep coalbed methane. Deep coalbed methane is characterized by low pressure, low porosity, low permeability, and multiple cleavages. Currently, the stimulation effect mainly relies on opening multiple cleavage fractures with large amounts of fracturing fluid. However, during hydraulic scouring, and simultaneously due to the abrasive effect of proppant, a large amount of coal dust is formed within the coal seam. Based on geological data and engineering practice analysis, low-viscosity fracturing fluids present difficulties in proppant addition, while high-viscosity fracturing fluids are difficult to break up, causing significant damage to the reservoir. Coal dust easily accumulates and settles, causing pump blockage. Furthermore, the poor permeability of the fracturing fluid prevents the adsorbed gas from penetrating deep pores. Therefore, providing a clean fracturing fluid suitable for deep coalbed methane is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a multifunctional integrated clean fracturing fluid for deep coalbed methane and its preparation method. The fracturing fluid possesses characteristics of low friction, prevention of coal dust accumulation, strong permeability, and oxidation resistance. The low friction characteristic reduces the construction pressure during fracturing operations, the prevention of coal dust accumulation solves the problem of coal dust accumulating and blocking the pump during flowback, the strong permeability characteristic solves the problem of strong filtration of fracturing fluid and improves the permeability of cleavage fractures, and the oxidation resistance solves the problem of iron dust blockage caused by pyrite oxidation. This system has a multifunctional integrated function.

[0005] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in a 100% weight ratio: 0.1-0.5% clean thickener, 0.3-0.5% coal powder dispersant, 0.2-0.5% cleavage penetrant, 0.5-1.0% antioxidant, and the balance being water;

[0006] 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.

[0007] The antioxidant is composed of a mixture of ascorbic acid or sodium sulfite, carboxyl polyether modified silicone oil, and deionized water.

[0008] Preferably, the carboxyl polyether modified silicone oil is prepared by the following method: mixing hydrogen-containing silicone oil, polyether, and acrylic acid, purging with nitrogen for 1.5-2 hours, heating to 85-90°C, adding catalyst Pt, and carrying out the reaction at atmospheric pressure for 6-7 hours. The acrylic acid is then removed by vacuum distillation to obtain the carboxyl polyether modified silicone oil.

[0009] Preferably, the total weight of the hydrogen-containing silicone oil, polyether, and acrylic acid is calculated as 100%, and the weight percentage 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.

[0010] Preferably, the coal powder dispersant is based on 100% by weight, and the specific weight ratio of each component is as follows: alkylphenol polyoxyethylene ether 5-25%, fatty alcohol polyoxyethylene ether 10-25%, carboxyl polyether modified silicone oil 30-40%, and the balance being deionized water.

[0011] Preferably, the antioxidant is based on 100% by weight, and the specific weight ratio of each component is as follows: ascorbic acid or sodium sulfite 20-30%, carboxyl polyether modified silicone oil 20-30%, and the balance being deionized water.

[0012] Preferably, the cleaning thickener is cationic polyacrylamide or nonionic polyacrylamide.

[0013] Preferably, the viscosity-average molecular weight of the cleaning thickener is greater than or equal to 8 million.

[0014] Preferably, the cleavage penetrant is a mixture of sodium linear alkylbenzene sulfonate, sodium secondary alkyl sulfonate, and deionized water.

[0015] Preferably, the weight of the permeation agent is calculated as 100%, and the specific weight ratio of each component is as follows: sodium linear alkylbenzene sulfonate 25-30%, sodium secondary alkyl sulfonate 20-25%, and the balance being deionized water.

[0016] Preferably, the antioxidant is a mixture of one of carboxylated polyether modified silicone oil, ascorbic acid, or sodium sulfite and water.

[0017] Preferably, the antioxidant is present in 100% by weight, and the specific weight ratio of each component is as follows: 20-30% carboxyl polyether modified silicone oil, 20-30% ascorbic acid or 20-30% sodium sulfite, with the balance being water.

[0018] A method for preparing a multifunctional integrated clean fracturing fluid for deep coalbed methane is described below: a clean thickener is added to water and stirred until homogeneous; then a coal powder dispersant is added and stirred until homogeneous; then a cleavage penetrant is added and stirred until homogeneous; finally, an antioxidant is added and stirred until homogeneous.

[0019] The viscosity of the multifunctional integrated clean fracturing fluid for deep coalbed methane prepared by this invention is 10-120 mPa·s.

[0020] Advantages of this invention:

[0021] This invention introduces a thickener, a dispersant containing carboxyl polyether silicone oil, a penetrant, and an antioxidant to formulate a fracturing fluid with low friction, anti-agglomeration, strong penetration, and antioxidant properties. This fluid can meet the requirements of large-volume operations, ensure uniform dispersion of coal powder in the fracturing fluid, and prevent coal powder from agglomerating and causing pump blockage. It can also change the hydrophobic properties of coal and rock, improve the permeability of the fracturing fluid, and prevent the oxidation of pyrite in the coal seam. This invention overcomes the problems of high construction friction, easy coal powder sedimentation, low permeability, and easy iron powder blockage when using existing fracturing fluids for deep coalbed methane. Detailed Implementation

[0022] Example 1

[0023] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in 100% by weight: 0.1% clean thickener, 0.5% coal powder dispersant, 0.5% cleavage penetrant, 1.0% antioxidant, and 97.9% water;

[0024] The cleaning thickener is cationic polyacrylamide with a viscosity-average molecular weight of 12 million.

[0025] The cleavage penetrant is composed of 25 wt% sodium linear alkylbenzene sulfonate, 25 wt% sodium secondary alkyl sulfonate, and 50 wt% water.

[0026] The coal powder dispersant is composed of 10 wt% alkylphenol polyoxyethylene ether, 10 wt% fatty alcohol polyoxyethylene ether, 30 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water.

[0027] The antioxidant is composed of a mixture of 20 wt% ascorbic acid, 30 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water.

[0028] The carboxyl polyether modified silicone oil is prepared by the following method: 40 wt% of hydrogen-containing silicone oil, 20 wt% of polyether, and 40 wt% of acrylic acid are mixed, nitrogen gas is introduced for 2 hours, the temperature is raised to 90°C, catalyst Pt is added, the weight of catalyst Pt is 1% of the total weight of hydrogen-containing silicone oil, polyether, and acrylic acid, the reaction is carried out at atmospheric pressure for 6 hours, and acrylic acid is removed by vacuum distillation to obtain carboxyl polyether modified silicone oil;

[0029] The preparation method of the deep coalbed methane multifunctional integrated clean fracturing fluid is as follows: add a clean thickener to water, stir evenly, then add a coal powder dispersant, stir evenly, then add a cleavage penetrating agent, stir evenly, then add an antioxidant, stir evenly, and it is ready.

[0030] The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 20 mPa·s.

[0031] Example 2

[0032] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in 100% by weight: 0.5% clean thickener, 0.3% coal powder dispersant, 0.2% cleavage penetrant, 1.0% antioxidant, and 98% water;

[0033] The cleaning thickener is a nonionic polyacrylamide with a viscosity-average molecular weight of 12 million.

[0034] The cleavage penetrant is composed of 30 wt% sodium linear alkylbenzene sulfonate, 20 wt% sodium secondary alkyl sulfonate, and 50 wt% water.

[0035] The coal powder dispersant is composed of 5 wt% alkylphenol polyoxyethylene ether, 10 wt% fatty alcohol polyoxyethylene ether, 40 wt% carboxyl polyether modified silicone oil and 45 wt% deionized water.

[0036] The antioxidant is composed of a mixture of 20 wt% sodium sulfite, 30 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water.

[0037] The carboxyl polyether modified silicone oil is the same as in Example 1;

[0038] The preparation method of the deep coalbed methane multifunctional integrated clean fracturing fluid is the same as that in Example 1;

[0039] The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 65 mPa·s.

[0040] Example 3

[0041] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in 100% by weight: 0.5% clean thickener, 0.4% coal powder dispersant, 0.5% cleavage penetrant, 0.5% antioxidant, and 98.1% water;

[0042] The cleaning thickener is a nonionic polyacrylamide with a viscosity-average molecular weight of 12 million.

[0043] The cleavage penetrant is composed of 28 wt% sodium linear alkylbenzene sulfonate, 22 wt% sodium secondary alkyl sulfonate, and 50 wt% water.

[0044] The coal powder dispersant is composed of 25 wt% alkylphenol polyoxyethylene ether, 25 wt% fatty alcohol polyoxyethylene ether, 35 wt% carboxyl polyether modified silicone oil and 15 wt% deionized water.

[0045] The antioxidant is composed of 30 wt% sodium sulfite, 20 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water.

[0046] The carboxyl polyether modified silicone oil is the same as in Example 1;

[0047] The preparation method of the deep coalbed methane multifunctional integrated clean fracturing fluid is the same as that in Example 1;

[0048] The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 55 mPa·s.

[0049] Example 4

[0050] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in 100% by weight: 0.1% clean thickener, 0.4% coal powder dispersant, 0.3% cleavage penetrant, 0.8% antioxidant, and 98.4% water;

[0051] The cleaning thickener is cationic polyacrylamide with a viscosity-average molecular weight of 12 million.

[0052] The cleavage penetrant is composed of 30 wt% sodium linear alkylbenzene sulfonate, 20 wt% sodium secondary alkyl sulfonate, and 50 wt% water.

[0053] The coal powder dispersant is composed of 10 wt% alkylphenol polyoxyethylene ether, 10 wt% fatty alcohol polyoxyethylene ether, 40 wt% carboxyl polyether modified silicone oil and 40 wt% deionized water.

[0054] The antioxidant is composed of 25 wt% sodium sulfite, 25 wt% carboxyl polyether modified silicone oil and 50 wt% deionized water.

[0055] The carboxyl polyether modified silicone oil is prepared by the following method: 50 wt% of hydrogen-containing silicone oil, 30 wt% of polyether, and 20 wt% of acrylic acid are mixed, nitrogen gas is introduced for 1.5 h, the temperature is raised to 85 °C, catalyst Pt is added, the weight of catalyst Pt is 1% of the total weight of hydrogen-containing silicone oil, polyether, and acrylic acid, the reaction is carried out at atmospheric pressure for 7 h, and acrylic acid is removed by vacuum distillation to obtain carboxyl polyether modified silicone oil;

[0056] The preparation method of the deep coalbed methane multifunctional integrated clean fracturing fluid is the same as that in Example 1;

[0057] The viscosity of the prepared deep coalbed methane multifunctional integrated clean fracturing fluid is 18 mPa·s.

[0058] Comparative Example 1

[0059] Compared to Example 1, neither the coal powder dispersant nor the antioxidant contains carboxyl polyether modified silicone oil.

[0060] The coal powder dispersant is composed of 10 wt% alkylphenol polyoxyethylene ether, 10 wt% fatty alcohol polyoxyethylene ether and 80 wt% deionized water.

[0061] The antioxidant is composed of a mixture of 20 wt% ascorbic acid and 80 wt% deionized water;

[0062] Everything else is the same as in Example 1;

[0063] The viscosity of the prepared fracturing fluid was 16 mPa·s.

[0064] Comparative Example 2

[0065] The carboxyl polyether modified silicone oil in the coal powder dispersant and antioxidant was replaced with polyether silicone oil, and the rest was the same as in Example 1; the viscosity of the fracturing fluid prepared was 19 mPa·s.

[0066] Comparative Example 3

[0067] The carboxyl polyether modified silicone oil in the coal powder dispersant and antioxidant was replaced with polyoxyethylene ether, and the rest was the same as in Example 1; the viscosity of the fracturing fluid prepared was 21 mPa·s.

[0068] Comparative Example 4

[0069] No coal powder dispersant is added, as detailed below:

[0070] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in 100% by weight: 0.1% clean thickener, 0.5% cleavage penetrant, 1.0% antioxidant, and 98.4% water;

[0071] Everything else is the same as in Example 1; the viscosity of the fracturing fluid prepared is 18 mPa·s.

[0072] Comparative Example 5

[0073] No antioxidants are added, as detailed below:

[0074] A multifunctional integrated clean fracturing fluid for deep coalbed methane, wherein the fracturing fluid is composed of the following raw materials in 100% by weight: 0.1% clean thickener, 0.5% coal powder dispersant, 0.5% cleavage penetrant, and 98.9% water;

[0075] Everything else is the same as in Example 1; the viscosity of the fracturing fluid prepared is 20 mPa·s.

[0076] Performance testing

[0077] I. Dispersion Ability Test

[0078] The fracturing fluids obtained in Example 1 and Comparative Examples 1-7 were broken up with 0.01 wt% persulfate at 80°C for 2 hours to obtain a broken fluid. The dispersion ability of the broken fluid on coal powder in deep coalbed methane reservoirs was determined by suspension method, and the suspension time of the broken fluid on coal powder was determined by static suspension property. The results are shown in Table 1.

[0079] Table 1. Results of Dispersion Ability Test

[0080]

[0081] As shown in Table 1, the fracturing fluid of the present invention has a low static settling velocity for pulverized coal and a long agglomeration time.

[0082] II. Static Stability Testing

[0083] The static stability of coal-water slurry was evaluated by assessing the ability of pulverized coal to resist gravity when no other external forces are applied. A coal-water slurry was prepared at room temperature by thoroughly mixing fracturing fluid and pulverized coal at a volume ratio of 100:70. The static stability of the slurry was then tested according to the static stability test method in GB / T18856.5-2008 "Coal-water slurry test methods - Part 5: Stability determination". The results are shown in Table 2.

[0084] Table 2 Static stability test results

[0085] .

[0086] III. Antioxidant Effect Testing

[0087] Pyrite-bearing coal and rock were ground into ultrafine powder with a pyrite content of 5%. 5g of the powder was thoroughly mixed with fracturing fluid at a mass ratio of 1:20. Nitrogen gas was introduced for 30 minutes, and the mixture was continuously stirred for 2 hours. The lower precipitate was collected by centrifugation, dried, and then the iron precipitate was floated to determine the amount of iron precipitate. The less precipitate, the stronger the oxidation resistance; the results are shown in Table 3.

[0088] Table 3 Antioxidant effect test

[0089] .

[0090] IV. Evaluation of Penetration Effect

[0091] The smooth surface of the coal and rock block, i.e. the natural bedding plane, was selected as the experimental surface. The contact angle of the coal and rock after contact with different fracturing fluids for 10 seconds was measured by dynamic contact angle. The smaller the contact angle, the stronger the wetting, spreading and penetration effect, as shown in Table 4.

[0092] Table 4. Test results of contact angle θ between fracturing fluid and coal / rock.

[0093] .

Claims

1. A multifunctional integrated clean fracturing fluid for deep coalbed methane, characterized in that: The fracturing fluid, by weight, consists of the following raw materials in 100% proportion: 0.1-0.5% cleaning thickener, 0.3-0.5% coal powder dispersant, 0.2-0.5% cleavage penetrant, 0.5-1.0% antioxidant, with 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. The cleavage penetrant is a mixture of sodium linear alkylbenzene sulfonate, sodium secondary alkyl sulfonate, and deionized water.

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

3. The multifunctional integrated clean fracturing fluid for deep coalbed methane as described in claim 2, characterized in that: The total weight of the hydrogen-containing silicone oil, polyether, and acrylic acid is calculated as 100%, and the weight percentage of each component is as follows: hydrogen-containing silicone oil 40-50%, polyether 20-30%, acrylic acid 20-40%; 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 as described in claim 1, characterized in that: The coal powder dispersant is calculated by weight as 100%, and the specific weight ratio of each component is as follows: alkylphenol polyoxyethylene ether 5-25%, fatty alcohol polyoxyethylene ether 10-25%, carboxyl polyether modified silicone oil 30-40%, and the balance being deionized water.

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

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

7. The multifunctional integrated clean fracturing fluid for deep coalbed methane as described in 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 as described in claim 1, characterized in that: The weight of the penetrant is calculated as 100%, and the specific weight ratio of each component is as follows: sodium linear alkylbenzene sulfonate 25-30%, sodium secondary alkyl sulfonate 20-25%, and the balance being deionized water.

9. The preparation method of the multifunctional integrated clean fracturing fluid for deep coalbed methane as described in claim 1, characterized in that: The specific preparation method is as follows: add a cleaning thickener to water, stir evenly, then add a coal powder dispersant, stir evenly, then add a cleavage penetrant, stir evenly, then add an antioxidant, stir evenly, and it is ready.

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