Reversed demulsifier for oilfield produced liquid and preparation method thereof

Abstract

This invention discloses a reverse demulsifier for oilfield produced fluid treatment, prepared using the following steps: N-(3-dimethylaminopropyl)methacrylamide, methyl chloroacetate, and the polymerization inhibitor p-hydroxyanisole are added to a solvent and reacted at a constant temperature for 10 hours. After cooling, dimethylaminopropylamine is added dropwise and reacted at room temperature for 1 hour. Then, p-hydroxyanisole is added and the reaction is heated for 4 hours. Next, etherifying agent Quat-188 with an effective content of 65% is added and the reaction is heated for 10 hours. After removing the solvent, a high cationic density monomer is obtained. Then, the high cationic density monomer and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid are dissolved in anhydrous ethanol and an initiator and reacted at a constant temperature and with stirring for 3 hours. Then, acrylate monomers are added, nitrogen is purged to remove oxygen, an initiator is added, and the reaction is heated for 3 hours to obtain the product. The reverse demulsifier for oilfield produced fluid treatment proposed in this invention has a stronger ability to neutralize the negative charge of oil droplets and can be applied to the demulsification treatment of high-concentration oily wastewater under more severe conditions.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to a reverse demulsifier for treating oilfield produced fluids and its preparation method. Background Technology

[0002] As offshore oilfields enter the mid-to-late stages of water injection production, the volume of produced fluid increases significantly. Due to limited space on offshore platforms, expanding equipment capacity is extremely difficult, leading to a substantial reduction in the residence time of produced fluid in existing treatment equipment. Therefore, to ensure normal production on offshore platforms, produced fluid treatment agents need to possess superior performance. Currently, the water content of produced fluids is high, typically exceeding 90%, resulting in a large amount of oil-in-water (O / W) emulsions. Reverse demulsifiers can act on O / W emulsions, promoting oil-water separation. Typically, the process for treating produced fluids on offshore platforms involves the produced fluid entering a three-phase separator, undergoing synergistic treatment with demulsifiers and reverse demulsifiers, and then the desorbed water enters the water system for further treatment with a cleaning agent. The better the reverse demulsifier's effect, the lower the treatment pressure in the water system.

[0003] Currently, cationic polymer reverse demulsifiers and polyacrylate emulsions are commonly used reverse demulsifiers. Cationic polymer reverse demulsifiers can effectively neutralize the negative charge on the surface of oil droplets, promoting droplet aggregation and coalescence, and are less affected by temperature, but they can produce sludge adhering to the oil walls. Polyacrylate emulsions have high demulsification efficiency and do not produce sludge adhering to the oil walls, but the emulsion is acidic and is mainly suitable for treating sodium bicarbonate aqueous produced fluids, thus limiting their application. For example, Chinese patent CN113698531A discloses a reverse demulsifier that combines the advantages of cationic reverse demulsifiers and polyacrylate emulsions by first polymerizing acrylates and N-(3-dimethylaminopropyl)methacrylamide as comonomers and then quaternizing them with 3-chloro-1-propanol. However, the reverse demulsifier is a random polymer, and its cationic structural unit contains only one quaternary ammonium salt, resulting in a low cationic density. Chinese patent CN114456307A also discloses a polymer with multiple cationic groups that can be used for air flotation of oily wastewater. However, due to its conventional polymerization method, the cationic groups in the polymer molecules are relatively evenly distributed, and the cationic density is still relatively limited. It is only suitable for the oil removal process of flotation wastewater with low oil content. Summary of the Invention

[0004] In view of this, in order to overcome the shortcomings of the existing technology, this invention proposes a reverse demulsifier for oilfield produced fluid treatment and its preparation method. A high cationic density reverse demulsifier with a block structure is synthesized. The quaternary ammonium salt units in its cationic structure are distributed according to the block structure, and the cationic groups are more concentrated. It has the advantages of low dosage, fast oil removal speed, and suitability for high-concentration oil-containing environments.

[0005] This invention discloses a method for preparing a reverse demulsifier for treating oilfield produced fluids, comprising the following steps:

[0006] Step S1: Add N-(3-dimethylaminopropyl)methacrylamide, methyl chloroacetate and the polymerization inhibitor p-hydroxyanisole to the solvent and react at 60-70℃ for 10 h to obtain intermediate A solution;

[0007] Step S2: After cooling to room temperature, add dimethylaminopropylamine dropwise to the intermediate A solution described in step S1 and react at room temperature for 1 hour. Then add the same amount of p-hydroxyanisole as in step S1 and heat to 60-70°C to react for 4 hours to obtain intermediate B solution.

[0008] Step S3: Add 65% effective content of etherifying agent Quat-188 to the intermediate B solution described in step S2 and react at 60-70℃ for 10h. After removing the solvent by rotary evaporation, a high cationic density monomer is obtained.

[0009] Step S4: The high cationic density monomer and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid described in step S3 are dissolved in anhydrous ethanol. After nitrogen purging for 15 min to remove oxygen, the initiator azobisisobutyronitrile is added. The mixture is stirred and reacted at 60-85℃ for 3 h. Then, acrylate monomers are added, nitrogen purging for 15 min to remove oxygen, and the initiator azobisisobutyronitrile is added again. The temperature is maintained and the reaction continues for 3 h to obtain the reverse demulsifier for oilfield produced fluid treatment.

[0010] In one embodiment of the present invention, the solvent in step S1 is one or a combination of methanol, anhydrous ethanol, and n-propanol.

[0011] In one embodiment of the present invention, the molar ratio of methyl chloroacetate to N-(3-dimethylaminopropyl)methacrylamide in step S1 is 1.1-1.3:1, and the total mass concentration of the two in the solution is between 50-60%.

[0012] In one embodiment of the present invention, the total amount of p-hydroxyanisole in steps S1 and S2 is 0.2% of the mass of N-(3-dimethylaminopropyl)methacrylamide, by weight percentage.

[0013] In one embodiment of the present invention, the molar ratio of dimethylaminopropylamine to N-(3-dimethylaminopropyl)methacrylamide in step S2 is 1.1-1.3:1.

[0014] In one embodiment of the present invention, the molar ratio of the etherifying agent Quat-188 to N-(3-dimethylaminopropyl)methacrylamide is 1.1-1.3:1.

[0015] In one embodiment of the present invention, the acrylate monomer in step S4 is one or more of methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate.

[0016] In one embodiment of the present invention, the total amount of high cationic density monomer and acrylate monomer in step S4 accounts for 45-55% of the solution mass concentration, and the mass ratio of the two is 0.25-0.5:1.

[0017] In one embodiment of the present invention, the amount of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid added in step S4 is 0.6-1.0% of the mass of the high cationic density monomer, and the total amount of initiator added is 0.6-1.0% of the total mass of the high cationic density monomer and the acrylate monomer.

[0018] Furthermore, the present invention provides an anti-phase demulsifier for treating oilfield produced fluids, which is prepared according to the above method.

[0019] The technical advantages of this invention are as follows:

[0020] The present invention proposes a reverse demulsifier for treating oilfield produced fluids, which has the advantages of low dosage, fast oil removal speed and high efficiency. The cationic groups in the block polymer formed are more concentrated than the cationic groups in conventional random polymerization, and have a stronger ability to neutralize the negative charge of oil droplets. It can be applied to the demulsification treatment of high-concentration oily wastewater under more severe conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0022] Figure 1 This is a synthesis route diagram for the reverse demulsifier used in oilfield produced fluid treatment in this invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0024] Example 1

[0025] 20g of N-(3-dimethylaminopropyl)methacrylamide, 14.05g of methyl chloroacetate, and 0.02g of p-hydroxyanisole were added to 27.83g of methanol and reacted at 65℃ for 10h to obtain intermediate A solution. After intermediate A solution was cooled to 25℃, 13.21g of dimethylaminopropylamine was added dropwise, and after reacting at room temperature for 1h, 0.02g of p-hydroxyanisole was added. Then the temperature was raised to 65℃ and reacted for 4h to obtain intermediate B solution. 37.40g of Quat-188 solution with an effective content of 65% was added to intermediate B solution and reacted at 65℃ for 10h. After removing the solvent by rotary evaporation, a high cationic density monomer was obtained.

[0026] Then, 5g of the above-mentioned high cationic density monomer and 0.04g of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were dissolved in 24.76g of anhydrous ethanol. After purging with nitrogen for 15min, 0.04g of azobisisobutyronitrile was added. After reacting at 70℃ for 3h, 20g of methyl acrylate was added. After purging with nitrogen for 15min, 0.16g of azobisisobutyronitrile was added and the reaction was continued for 3h to obtain the reverse demulsifier for oilfield produced fluid treatment.

[0027] Example 2

[0028] 20g of N-(3-dimethylaminopropyl)methacrylamide, 14.05g of methyl chloroacetate, and 0.02g of p-hydroxyanisole were added to 27.83g of methanol and reacted at 65℃ for 10h to obtain intermediate A solution. After intermediate A solution was cooled to 25℃, 13.21g of dimethylaminopropylamine was added dropwise, and after reacting at room temperature for 1h, 0.02g of p-hydroxyanisole was added. Then the temperature was raised to 65℃ and reacted for 4h to obtain intermediate B solution. 37.40g of Quat-188 solution with an effective content of 65% was added to intermediate B solution and reacted at 65℃ for 10h. After removing the solvent by rotary evaporation, a high cationic density monomer was obtained.

[0029] Then, 10g of high cationic density monomer and 0.08g of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were dissolved in 29.68g of anhydrous ethanol. After purging with nitrogen for 15 minutes, 0.08g of azobisisobutyronitrile was added. The mixture was reacted at 70℃ for 3 hours, and then 20g of methyl acrylate was added. After purging with nitrogen for 15 minutes, 0.16g of azobisisobutyronitrile was added, and the reaction was continued for 3 hours to obtain the reverse demulsifier for oilfield produced fluid treatment.

[0030] Example 3

[0031] The synthesis method and raw material dosage in this embodiment are the same as in Example 3, except that the acrylate monomer in this embodiment is ethyl acrylate.

[0032] To further illustrate the product's effectiveness, the performance of the product in this invention will be evaluated below in conjunction with specific examples.

[0033] The oil samples used in the performance evaluation process were all produced fluids from a certain oil field, with an oil content of 1552 mg / L in the aqueous phase.

[0034] I. Oil Removal Rate Test

[0035] 25 mL of the produced fluid was kept in a 65°C water bath for 10 min, 20 mg / L of reverse demulsifier was added, the mixture was shaken 50 times and then kept in a 65°C water bath for 5 min. Finally, 10 mL of the lower clear liquid was taken, and the oil yield was calculated based on the change in turbidity of the produced fluid before and after reverse demulsification. The results are shown in Table 1.

[0036] Table 1. Oil removal rate test results

[0037] Demulsifier group Example 1 Example 2 Example 3 Oil removal rate (%) 91.4 85.6 97.3

[0038] As shown in Table 1, the oil removal rate of the three reverse demulsifiers in the above examples all reached over 85%, and all had good oil removal effect. Among them, when the acrylate monomer is ethyl acrylate and the mass ratio of high cationic density monomer to ethyl acrylate is 0.5:1, the reverse demulsifier in Example 3 has the best oil removal performance.

[0039] II. Zeta potential test

[0040] The zeta potential of the produced fluid obtained after adding different groups of reverse demulsifiers in the above oil removal rate test was tested, and the results are shown in Table 2.

[0041] Table 2 Zeta potential test results

[0042] Demulsifier group blank Example 1 Example 2 Example 3 Zeta potential (mV) -32.72 -1.21 -2.35 -0.85

[0043] As shown in Table 2, the three groups of reverse demulsifiers in the above embodiments can greatly reduce the absolute value of the Zeta potential. This is because the reverse demulsifiers have a high cation density, which can effectively neutralize the negative charge on the surface of the oil droplets.

[0044] III. Performance Comparison of Existing Products

[0045] The demulsifiers disclosed in Example 2 and Example 9 of Chinese Patent CN113698531A also have a certain demulsification effect. Therefore, under the same test conditions as the degreasing rate of the present invention, their performance was compared with that of the demulsifiers disclosed in the examples of the present invention. The results are shown in Table 3.

[0046] Table 3 shows the performance comparison results between the product and the product in Chinese Patent CN113698531A.

[0047]

[0048]

[0049] Among them, Examples 2 and 9 of Chinese Patent CN113698531A correspond to Comparative Example 1 and Comparative Example 2, respectively. As can be seen from Table 3, at an addition of 20 mg / L, the oil removal rate for high oily wastewater with an oil content of 1552 mg / L is significantly higher than that in Comparative Example 1 and Comparative Example 2. The measurement results of Zeta potential show that the reverse demulsifier in this invention has a stronger ability to reduce the absolute value of Zeta potential. The reason is that the reverse demulsifier in this invention has more cationic groups than the product in Chinese Patent CN113698531A, which makes it easier for oil droplets to aggregate and coalesce, thus having a better reverse demulsification performance.

[0050] Chinese patent CN114456307A also discloses a high cationic density polymer, which is polymerized by solution random polymerization. The products in Example 2 and Example 3 are used as Comparative Example 3 and Comparative Example 4, respectively, and compared with the reverse demulsifier in this invention. The degreasing effect is tested under the same test conditions as the degreasing rate of the present invention, and the results are shown in Table 4.

[0051] Table 4 shows the performance comparison results between the product and the product in Chinese Patent CN114456307A.

[0052] Demulsifier group Example 1 Example 2 Example 3 Comparative Example 3 Comparative Example 4 Increased dosage (mg / L) 20 20 20 20 20 Oil removal rate (%) 91.4 85.6 97.3 76.1 81.5

[0053] As shown in Table 4, the oil removal performance of the product in this invention is superior to that in the comparative examples under high oil content conditions. It is worth noting that the test conditions in this invention are for high oil content wastewater with an oil content of 1552 mg / L, which is about twice the oil content of the 822 mg / L oil content wastewater used in the test of Chinese Patent CN114456307A. Moreover, compared with the test methods of comparative examples 3 and 4, which use air flotation column aeration, the embodiment in this invention can achieve an oil removal rate of more than 85% under the test conditions of 50 shaking cycles, further proving that the demulsifier in this invention has better oil removal performance. The reason is that the block structure formed by the product in this invention makes the cationic groups more concentrated, with stronger charge performance and better performance in neutralizing the negative charge of oil droplets.

[0054] IV. Evaluation of Demulsifier Dosage

[0055] The amount of demulsifier used in Example 3 was varied to 10-30 mg / L for oil removal rate testing, and the results are shown in Table 5.

[0056] Table 5. Oil removal rate test results of demulsifier in Example 3 with different dosages.

[0057]

[0058] As shown in Table 5, the demulsifier product in Example 3 has excellent degreasing performance. When its dosage is only 10 mg / L, the degreasing rate can still be greater than 88%.

[0059] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims.

Claims

1. A method for preparing a reverse demulsifier for treating oilfield produced fluids, characterized in that, Includes the following steps: Step S1: Add N-(3-dimethylaminopropyl)methacrylamide, methyl chloroacetate and the polymerization inhibitor p-hydroxyanisole to the solvent and react at 60-70℃ for 10 h to obtain intermediate A solution; Step S2: After cooling to room temperature, add dimethylaminopropylamine dropwise to the intermediate A solution described in step S1 and react at room temperature for 1 hour. Then add the same amount of p-hydroxyanisole as in step S1 and heat to 60-70°C to react for 4 hours to obtain intermediate B solution. Step S3: Add 65% effective content of etherifying agent Quat-188 to the intermediate B solution described in step S2 and react at 60-70℃ for 10h. After removing the solvent by rotary evaporation, a high cationic density monomer is obtained. Step S4: The high cationic density monomer described in step S3 and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid are dissolved in anhydrous ethanol. After nitrogen purging for 15 min to remove oxygen, the initiator azobisisobutyronitrile is added. The mixture is stirred and reacted at 60-85℃ for 3 h. Then, acrylate monomers are added, nitrogen purging for 15 min to remove oxygen, and the initiator azobisisobutyronitrile is added again. The temperature is maintained and the reaction continues for 3 h to obtain the reverse demulsifier for oilfield produced fluid treatment.

2. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: The solvent in step S1 is one or a combination of methanol, anhydrous ethanol, and n-propanol.

3. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: In step S1, the molar ratio of methyl chloroacetate to N-(3-dimethylaminopropyl)methacrylamide is 1.1-1.3:1, and the total mass concentration of both in the solution is between 50-60%.

4. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: The total amount of p-hydroxyanisole in steps S1 and S2 is 0.2% of the mass of N-(3-dimethylaminopropyl)methacrylamide, by mass percentage.

5. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: The molar ratio of dimethylaminopropylamine to N-(3-dimethylaminopropyl)methacrylamide in step S2 is 1.1-1.3:

1.

6. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: The molar ratio of the etherifying agent Quat-188 to N-(3-dimethylaminopropyl)methacrylamide is 1.1-1.3:

1.

7. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: The acrylate monomers in step S4 are one or more combinations of methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

8. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: In step S4, the total amount of high cationic density monomers and acrylate monomers accounts for 45-55% of the solution mass concentration, and the mass ratio of the two is 0.25-0.5:

1.

9. The method for preparing an anti-phase demulsifier for oilfield produced fluid treatment according to claim 1, characterized in that: In step S4, the amount of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid added is 0.6-1.0% of the mass of the high cationic density monomer, and the total amount of initiator added is 0.6-1.0% of the total mass of the high cationic density monomer and the acrylate monomer.

10. A reverse demulsifier for treating oilfield produced fluids, characterized in that, It is prepared by the method described in any one of claims 1-9.

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