Preparation method of salt-resistant anti-drag thickening agent

Abstract

The invention discloses a preparation method of a salt-resistant anti-drag thickening agent. The preparation method comprises the following steps: preparing an oil-phase mixture from kerosene and Span20 and Tween60 emulsifiers; preparing a water-phase emulsifier by using acrylic acid AM, acrylamide AA and a sodium vinyl benzene sulfonate monomer; the preparation method comprises the following steps: weighing an oil-phase mixture and a water-phase emulsifier according to a mass ratio of 100: (10-15), then pouring the oil-phase mixture into a high-speed stirrer, slowly adding the water-phase emulsifier, then adding the mixture of the oil-phase mixture and the water-phase emulsifier into an open reactor, finally introducing nitrogen, and cooling to 18 DEG C or below; adding 0.4% sodium hydrogen sulfite, raising the temperature to 33-35 DEG C within 2 hours at the temperature raising speed of 0.1-0.3 DEG C / min, and controlling the temperature to react until the reaction is complete; the temperature is not changed when the initiator is continuously added, and the reaction is complete.

Description

Technical Field

[0001] The present invention belongs to the technical field of enhanced oil and gas production, and particularly relates to a preparation method of a salt-resistant drag-reducing thickening agent. Background Art

[0002] At present, the fracturing fluid system applied in oil and gas fields is mainly based on guar gum. Compared with other fracturing fluid systems, it has a large mixing viscosity, a large liquid sand-carrying capacity, and a large sweep coefficient. However, compared with other fracturing fluid systems, guar gum has the disadvantages of a high content of gel-breaking residues that are likely to block pore throats, a high friction resistance; and great difficulty in reusing the fracturing fluid. The surfactant-based fracturing fluid has a good viscosity-increasing effect and good salt resistance. In a salt-containing liquid, the colloidal particles are transformed into micelles that entangle with each other, thereby increasing the liquid viscosity. The surfactant is prone to gel-breaking in the presence of oil and condensate. However, it is sensitive to temperature and is mostly used in shallow wells. The construction cost is high, so it is not applicable to wells with a large scale of fracturing construction, nor is it applicable to large-scale applications of shale gas fracturing. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of a salt-resistant drag-reducing thickening agent, so as to solve the problems that the existing surfactant has a high construction cost and is not applicable to wells with a large scale of fracturing construction, nor is it applicable to large-scale applications of shale gas fracturing.

[0004] In order to achieve the above purpose, the technical solution adopted by the present invention is: a preparation method of a salt-resistant drag-reducing thickening agent, which is specifically implemented according to the following steps:

[0005] Step 1, prepare an oil-phase mixture using kerosene and Span20 and Tween60 emulsifiers;

[0006] Step 2, prepare an aqueous-phase emulsifier using acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomers;

[0007] Step 3, weigh the oil-phase mixture and the aqueous-phase emulsifier according to a mass ratio of 100:10 - 15. Then pour the oil-phase mixture into a high-speed stirrer, slowly add the aqueous-phase emulsifier, then add the mixture of the two to an open reactor, and finally introduce nitrogen and cool down to below 18°C;

[0008] Step 4, add 0.4% sodium bisulfite, and raise the temperature to 33°C - 35°C within 2 hours at a heating rate of 0.1°C / min - 0.3°C / min, and control the temperature for reaction until the reaction is complete;

[0009] Step 5, continue to add the initiator until the temperature no longer changes and the reaction is complete.

[0010] As a preferred technical solution of the present invention, in the step 1, kerosene, Span20, and Tween60 emulsifiers are weighed in a beaker according to a mass ratio of 50:5:0.8, and stirred on a magnetic stirrer at a rate of 1000 r / min - 1400 r / min for 7 min - 9 min to uniformly mix the oil and the emulsifier, obtaining an oil-phase mixture.

[0011] As a preferred technical solution of the present invention, in the step 2, the mass ratio of acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomers is 1:2:1, stirred and dissolved in water, adjusted to a pH of 6.5 - 6.8 with sodium hydroxide, and 0.4 g of ammonium persulfate is added; 0.3 - 0.5 g of ammonium persulfate corresponds to every 500 g of water.

[0012] As a preferred technical solution of the present invention, in the step 3, the time for slowly adding the water-phase emulsifier is 2 min - 4 min.

[0013] As a preferred technical solution of the present invention, in the step 4, the temperature is controlled for reaction for 2 h - 4 h until the reaction is complete.

[0014] As a preferred technical solution of the present invention, in the step 4, if the temperature rises too fast during the temperature control process, cooling water is added for cooling.

[0015] As a preferred technical solution of the present invention, in the step 4, if the temperature decreases, the initiator is continuously added for initiation.

[0016] The beneficial effects of the present invention are as follows: A preparation method of an anti-salt drag reduction and thickening agent of the present invention, according to the principle of cost reduction and efficiency improvement, through the optimization of functional monomers, sodium vinylbenzenesulfonate has good compatibility with the emulsion and can be used as a salt-resistant functional monomer. It optimizes the emulsification system, determines that alkanolamide oleic acid alcohol M83VG is the main emulsifier formula. On this basis, the emulsifier dosage, monomer molar ratio, molar number of polymerized monomers, initiator system and dosage, reaction temperature, and reaction time are optimized, which can be reused, reducing the environmental protection pressure and simultaneously reducing the cost. Description of the Drawings

[0017] Figure 1 It is a graph showing the change in the apparent viscosity of the anti-salt drag reduction and thickening agent prepared by the present invention in test water;

[0018] Figure 2 It is a graph showing the change in the apparent viscosity of the anti-salt drag reduction and thickening agent prepared by the present invention in mineral water. Detailed Embodiments

[0019] The technical solutions of the present invention will be further described in detail below in conjunction with the description of the drawings and specific embodiments.

[0020] Example 1

[0021] A preparation method of a salt - resistant drag - reducing thickener of the present invention is specifically implemented according to the following steps:

[0022] Step 1, Kerosene, Span20, and Tween60 emulsifiers are weighed in a beaker according to a mass ratio of 50:5:0.8, and stirred on a magnetic stirrer at a rate of 1000 r / min for 9 min to uniformly mix the oil and the emulsifier, obtaining an oil - phase mixture;

[0023] Step 2, The mass ratio of acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomers is 1:2:1. They are stirred and dissolved in water, the pH is adjusted to 6.5 with sodium hydroxide, and ammonium persulfate is added to prepare an aqueous - phase emulsifier; for every 500 g of water, 0.3 g of ammonium persulfate is used;

[0024] Step 3, Weigh the oil - phase mixture and the aqueous - phase emulsifier according to a mass ratio of 100:10. Then pour the oil - phase mixture into a high - speed stirrer, slowly add the aqueous - phase emulsifier for 2 min, then add the mixture of the two into an open reactor, and finally introduce nitrogen and cool down to below 18 °C;

[0025] Step 4, Add 0.4% sodium bisulfite, and raise the temperature to 33 °C at a heating rate of 0.1 °C / min within 2 h, and control the temperature for reaction for 4 h until the reaction is complete. During the temperature - control process, if the temperature rises too fast, add cooling water to cool down; if the temperature drops, continue to add the initiator to initiate the reaction;

[0026] Step 5, Continue to add the initiator until the temperature no longer changes and the reaction is complete.

[0027] Example 2

[0028] A preparation method of a salt - resistant drag - reducing thickener of the present invention is specifically implemented according to the following steps:

[0029] Step 1, Kerosene, Span20, and Tween60 emulsifiers are weighed in a beaker according to a mass ratio of 50:5:0.8, and stirred on a magnetic stirrer at a rate of 1400 r / min for 7 min to uniformly mix the oil and the emulsifier, obtaining an oil - phase mixture;

[0030] Step 2, The mass ratio of acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomers is 1:2:1. They are stirred and dissolved in water, the pH is adjusted to 6.8 with sodium hydroxide, and ammonium persulfate is added to prepare an aqueous - phase emulsifier; for every 500 g of water, 0.5 g of ammonium persulfate is used;

[0031] Step 3: Weigh the oil-phase mixture and the aqueous-phase emulsifier according to a mass ratio of 100:15. Then pour the oil-phase mixture into a high-speed stirrer, slowly add the aqueous-phase emulsifier over 4 min, then add the mixture of the two into an open reactor, and finally introduce nitrogen and cool down to below 18°C.

[0032] Step 4: Add 0.4% sodium bisulfite and raise the temperature to 35°C at a heating rate of 0.3°C / min within 2 h, and control the temperature for reaction for 2 h until the reaction is complete. During the temperature control process, if the temperature rises too fast, add cooling water to cool down; if the temperature drops, continue to add the initiator to initiate the reaction.

[0033] Step 5: Continue to add the initiator until the temperature no longer changes, indicating that the reaction is complete.

[0034] Example 3

[0035] A preparation method of a salt-resistant drag-reducing thickener of the present invention is specifically implemented according to the following steps:

[0036] Step 1: Weigh kerosene, Span20, and Tween60 emulsifier in a beaker according to a mass ratio of 50:5:0.8, and stir at a rate of 1200 r / min on a magnetic stirrer for 8 min to mix the oil and the emulsifier evenly to obtain an oil-phase mixture.

[0037] Step 2: The mass ratio of acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomers is 1:2:1. Stir and dissolve them in water, adjust the pH to 6.6 with sodium hydroxide, and add ammonium persulfate to prepare an aqueous-phase emulsifier; 0.4 g of ammonium persulfate corresponds to every 500 g of water.

[0038] Step 3: Weigh the oil-phase mixture and the aqueous-phase emulsifier according to a mass ratio of 100:12. Then pour the oil-phase mixture into a high-speed stirrer, slowly add the aqueous-phase emulsifier over 3 min, then add the mixture of the two into an open reactor, and finally introduce nitrogen and cool down to below 18°C.

[0039] Step 4: Add 0.4% sodium bisulfite and raise the temperature to 34°C at a heating rate of 0.2°C / min within 2 h, and control the temperature for reaction for 3 h until the reaction is complete. During the temperature control process, if the temperature rises too fast, add cooling water to cool down; if the temperature drops, continue to add the initiator to initiate the reaction.

[0040] Step 5: Continue to add the initiator until the temperature no longer changes, indicating that the reaction is complete.

[0041] Example 4

[0042] A preparation method of a salt-resistant drag-reducing thickener of the present invention is specifically implemented according to the following steps:

[0043] Step 1: Weigh kerosene, Span20, and Tween60 emulsifiers in a beaker according to a mass ratio of 50:5:0.8, and stir them on a magnetic stirrer at a rate of 1300 r / min for 8 min to uniformly mix the oil and the emulsifiers, obtaining an oil-phase mixture;

[0044] Step 2: The mass ratio of acrylic acid AM, acrylamide AA, and sodium vinyl benzene sulfonate monomers is 1:2:1. Dissolve them by stirring in water, adjust the pH to 6.7 with sodium hydroxide, and add ammonium persulfate to prepare an aqueous-phase emulsifier; 0.4 g of ammonium persulfate corresponds to every 500 g of water;

[0045] Step 3: Weigh the oil-phase mixture and the aqueous-phase emulsifier according to a mass ratio of 100:10 - 15. Then pour the oil-phase mixture into a high-speed stirrer, slowly add the aqueous-phase emulsifier for 3 min, then add the mixture of the two into an open reactor, and finally introduce nitrogen and cool down to below 18 °C;

[0046] Step 4: Add 0.4% sodium bisulfite and raise the temperature to 34 °C within 2 h at a heating rate of 0.2 °C / min, and control the temperature for reaction for 3 h until the reaction is complete. During the temperature control process, if the temperature rises too fast, add cooling water to cool down. If the temperature drops, continue to add the initiator to initiate the reaction;

[0047] Step 5: Continue to add the initiator until the temperature no longer changes, and the reaction is complete.

[0048] The friction during the construction process of the polyacrylamide fracturing fluid is small, and it is easy to break the gel and flow back. However, the recycled flowback fluid can only be used as a preflush fluid, and the salt tolerance performance of this system is poor; moreover, the stability of the base fluid is poor, and stratification often occurs. Before on-site construction, it is necessary to manually roll the barrel to uniformly mix the emulsion. Otherwise, when the pipeline sucks the liquid, it will first suck the lower-layer high-concentration emulsion, resulting in uneven liquid preparation and easily causing accidents, bringing troubles to the construction. According to the principle of cost reduction and efficiency increase, in the present invention, through the optimization of functional monomers, sodium vinyl benzene sulfonate has good compatibility with the emulsion and can be used as a salt-tolerant functional monomer. The emulsification system is optimized, and it is determined that alkanolamide oleic alcohol M83VG is the main emulsifier formula. On this basis, the dosage of the emulsifier, the monomer molar ratio, the molar number of polymerized monomers, the initiator system and its dosage, the reaction temperature, and the reaction time are optimized to obtain the final formula, making it reusable, reducing the environmental protection pressure, and at the same time reducing the cost.

[0049] 1. Shear stability

[0050] Prepare a 1% solution of the salt-resistant drag reduction thickener with clear water and a 1.5% solution with 40,000 mg / L of mineralized water for shear stability evaluation. Use an RS6000 rheometer to test the change in the apparent viscosity of the above solutions under shear conditions at a temperature of 90 °C and a shear rate of 170 s⁻¹ for 1 h. The test results are shown in Figure 1 、 Figure 2。

[0051] It can be seen from Figure 1 and Figure 2 that when the shear rate is constant, the viscosity gradually decreases with the increase of temperature in both fresh water and mineralized water. When the temperature remains constant at 90 °C, the viscosity also basically remains unchanged. When shearing the 1% inverse emulsion in fresh water for 1 h, the viscosity decreases from 114 mPa·s to 92 mPa·s, and the viscosity loss rate is 19.3%. When shearing the 1.5% inverse emulsion in 40000 mg / L mineralized water at 90 °C for 1 h, the viscosity decreases from 71 mPa·s to 53 mPa·s, and the viscosity loss rate is 25%. The laboratory evaluation system has good shear resistance.

[0052] 2. Apparent viscosity

[0053] Measure 5 ml of the polymer emulsion generated in each example with a syringe and place it in a beaker. Add 495 ml of distilled water and stir it with a magnetic stirrer at a speed of 1200 r / min for 1 min at room temperature to prepare a 1% emulsion polymer solution. Measure the apparent viscosity of the solution respectively, and the results are shown in the table.

[0054]

[0055] It can be seen from the table that with the increase of the total concentration of reaction monomers, the apparent viscosity of the polymer solution increases. The main reason is that when the monomer concentration is low, there are fewer polymer monomers in the monomer droplets of the emulsion, and the chance of contact and collision between monomers is small, resulting in a slower polymerization rate, while the termination rate of free radicals is relatively large. Therefore, it is not easy to polymerize high-molecular-weight polymers. However, when the total monomer concentration exceeds 35%, with the increase of the total concentration of polymer monomers in the monomer droplets, the concentration of monomer free radicals in the solution becomes larger, the polymerization rate increases, and all monomers in the droplets can participate in the polymerization. Therefore, the molecular weight of emulsion polymerization is larger than that of free radical polymerization, and the viscosity of the system increases sharply. When the total monomer concentration is too high, reaching 40%, it is not easy to control the temperature during the temperature control stage, and the polymerization heat cannot be removed in time, resulting in too high a temperature rise in the system, intermolecular cross-linking, affecting the linear growth of molecular chains, and prone to explosive polymerization, resulting in a decrease in the viscosity of the polymer solution. Therefore, the preferred dosage of the total monomer concentration in this experiment is 35%.

Claims

1. Preparation method of salt-resistant drag reduction thickener, Characterized in that, It is specifically implemented according to the following steps: Step 1, prepare an oil-phase mixture using kerosene and Span20 and Tween60 emulsifiers; Step 2, prepare an aqueous-phase emulsifier using acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomer; Step 3, weigh the oil-phase mixture and the aqueous-phase emulsifier according to a mass ratio of 100:10 - 15. Then pour the oil-phase mixture into a high-speed stirrer, slowly add the aqueous-phase emulsifier, then add the mixture of the two into an open reactor, and finally introduce nitrogen and cool down to below 18°C; Step 4, add 0.4% sodium bisulfite and raise the temperature to 33°C - 35°C within 2 h at a heating rate of 0.1°C / min - 0.3°C / min, and control the temperature for reaction until the reaction is complete; Step 5, continue to add the initiator until the temperature no longer changes and the reaction is complete.

2. The preparation method of the salt-resistant drag reduction thickener according to claim 1, Characterized in that, In the said step 1, kerosene, Span20, and Tween60 emulsifier are weighed in a beaker according to a mass ratio of 50:5:0.8, and stirred at a rate of 1000 r / min - 1400 r / min on a magnetic stirrer for 7 min - 9 min to mix the oil and the emulsifier evenly to obtain an oil-phase mixture.

3. The preparation method of the salt-resistant drag reduction thickener according to claim 2, Characterized in that, In the said step 2, the mass ratio of acrylic acid AM, acrylamide AA, and sodium vinylbenzenesulfonate monomer is 1:2:1, stirred and dissolved in water, adjusted to pH 6.5 - 6.8 with sodium hydroxide, and 0.4 g of ammonium persulfate is added; for every 500 g of water, 0.3 - 0.5 g of ammonium persulfate corresponds.

4. The preparation method of the salt-resistant drag reduction thickener according to claim 3, Characterized in that, In the said step 3, the time for slowly adding the aqueous-phase emulsifier is 2 min - 4 min.

5. The preparation method of the salt-resistant drag reduction thickener according to claim 4, Characterized in that, In the said step 4, control the temperature for reaction for 2 h - 4 h until the reaction is complete.

6. The preparation method of the salt-resistant drag reduction thickener according to claim 5, Characterized in that, In the said step 4, if the temperature rises too fast during the temperature control process, add cooling water to cool down.

7. The preparation method of the salt-resistant drag reduction thickener according to claim 6, Characterized in that, In the said step 4, if the temperature drops, continue to drop the initiator to initiate.

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