Salt-tolerant demulsifier system, applications, and methods for treating high-salinity shale oil production fluids

Abstract

The present application relates to the technical field of oilfield chemistry, in particular to a salt-tolerant demulsifier system, application and a high-salt shale oil produced liquid treatment method.The salt-tolerant demulsifier system comprises a salt-tolerant block polyether main agent, a zwitterionic surfactant and an organic acid complexing agent; the salt-tolerant block polyether main agent is a star-shaped block copolymer with polyethylene oxide as a hydrophilic head, polypropylene oxide as a hydrophobic chain and polyglycerol or pentaerythritol as a starter; and the zwitterionic surfactant is a sulfobetaine surfactant.The salt-tolerant demulsifier system has excellent salt tolerance, high demulsification efficiency, fast speed and clean water quality; and the high-salt shale oil produced liquid treatment method has wide applicability and good effects on not only high-salt shale oil but also conventional high-salt crude oil produced liquid.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and more specifically, to salt-resistant demulsifier systems, their applications, and methods for treating produced fluids from high-salt shale oil. Background Technology

[0002] The produced fluids generated during shale oil extraction are extremely stable water-in-oil (W / O) emulsions. Compared with conventional crude oil produced fluids, shale oil produced fluids have the following significant characteristics: First, they contain a large number of nano-sized clay particles, colloids, and asphaltenes, which act as natural emulsifiers to form a stable interfacial film at the oil-water interface; second, the formation water has extremely high salinity, with total dissolved solids (TDS) often exceeding 50,000 mg / L, and even reaching over 200,000 mg / L, and is rich in Ca. 2+ Mg 2+ Divalent cations.

[0003] High mineralization, especially high concentrations of divalent cations, poses a serious challenge to traditional demulsifiers.

[0004] First, high concentrations of inorganic salts will "salt out" traditional nonionic polyether demulsifiers (such as SP-169 and AE type), causing their solubility in the aqueous phase to decrease and precipitate out from the interfacial film, resulting in a sharp decrease or even failure of demulsification activity.

[0005] Meanwhile, divalent cations (Ca) 2+ Mg 2+ It can effectively shield the surface charge of demulsifier molecules and natural emulsion particles, compress the electric double layer, and even generate "ion bridging" between different negatively charged particles or molecules, which in turn enhances the strength and toughness of the interfacial film and makes the emulsion more stable.

[0006] In addition, salts, along with substances such as bitumen, may work together to form a denser interfacial network structure.

[0007] Currently, most demulsifiers on the market are designed for crude oil produced fluids with low to medium salinity. When used in high-salt shale oil systems, they generally suffer from poor adaptability, low dehydration rate, slow dehydration speed, and unclear dehydrated water.

[0008] For example, patent CN120173230A discloses a nonionic demulsifier of a combination phenol-primary polyamide amine resin and its preparation method. Although it mentions salt resistance, it targets a mineralization level (<80,000 mg / L) and divalent ion tolerance (Ca). 2+ +Mg 2+ Limited (<5000 mg / L), making it difficult to cope with extreme conditions.

[0009] For example, the patent with publication number CN118460241A uses nanomaterial composites, but the cost is high and the long-term dispersion stability is poor. Summary of the Invention

[0010] The technical problem to be solved by this invention is to provide a salt-resistant demulsifier system, its application, and a method for treating produced fluids from high-salt shale oil.

[0011] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0012] This invention provides a salt-resistant demulsifier system, wherein the components of the salt-resistant demulsifier system include a salt-resistant block polyether main agent, an amphoteric surfactant, and an organic acid decomplexing agent;

[0013] The salt-resistant block polyether main agent is a star-shaped block copolymer with polyethylene oxide as the hydrophilic head, polypropylene oxide as the hydrophobic chain, and polyglycerol or pentaerythritol as the initiator; the zwitterionic surfactant is a sulfobetaine-type surfactant.

[0014] Based on the above technical solution, the present invention can be further improved as follows.

[0015] Furthermore, the number-average molecular weight of the star-shaped block copolymer is 5000-15000.

[0016] Furthermore, the organic acid decomplexing agent is citric acid, ethylenediaminetetraacetic acid, or gluconic acid.

[0017] Furthermore, the composition and mass percentage of the salt-resistant demulsifier system are as follows: 40%-70% of the salt-resistant block polyether main agent, 10%-30% of the zwitterionic surfactant, 5%-15% of the organic acid decomplexing agent, and the remainder is solvent.

[0018] Furthermore, the solvent is one or more of methanol, ethanol, and isopropanol.

[0019] The present invention also provides a method for preparing the salt-resistant demulsifier system as described above, wherein the salt-resistant block polyether main agent is first synthesized, and then the components are mixed, heated and stirred to obtain the salt-resistant demulsifier system.

[0020] Furthermore, the synthesis method of the salt-resistant block polyether main agent is as follows: under the conditions of 120°C and 0.3MPa, polyglycerol or pentaerythritol is used as the initiator, and propylene oxide is added first for polymerization under the action of a catalyst, and then the temperature is lowered to 100°C and ethylene oxide is added for end-capping.

[0021] Furthermore, the heating temperature is 40-60℃, and the stirring time is 2-4 hours.

[0022] The present invention also provides the application of the salt-resistant demulsifier system described above in the treatment of produced fluids from high-salt shale oil, wherein the produced fluid has a salinity TDS greater than 150,000 mg / L and a concentration of divalent metal cations greater than 10,000 mg / L.

[0023] The present invention also provides a method for treating produced fluid from high-salt shale oil, including a step of demulsification using a salt-tolerant demulsifier system as described above; the amount of the demulsifier system added per liter of the high-salt shale oil produced fluid is 50-200 mg, and the demulsification temperature is 50-70℃.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The salt-resistant demulsifier system of the present invention has a low critical micelle concentration of star-shaped PEO-PPO block polyether, which is not easy to precipitate in the presence of salt. The PEO segments can still maintain a certain hydration capacity in a high-salt environment and can strongly penetrate into the interior of the interface film composed of asphaltene and nanoparticles by relying on their multi-site adsorption.

[0026] (2) In the salt-resistant demulsifier system of the present invention, the zwitterionic surfactant has good charge stabilization and membrane displacement effect;

[0027] (3) The salt-resistant demulsifier system of the present invention has an ion chelating effect of organic acid decomplexing agent. The star-shaped PEO-PPO block polyether, amphoteric surfactant and organic acid decomplexing agent can work together on the interface film in the high salt environment through the synergistic mechanism of "penetration destruction - charge stabilization - ion chelation". The synergistic effect is strong and the overall performance is far superior to single component or conventional compound products, so as to achieve efficient demulsification.

[0028] (4) The salt-resistant demulsifier system of the present invention can effectively resist the negative effects of high mineralization (especially high content of divalent ions) and can efficiently destroy the novel demulsifier system of shale oil emulsion stabilized by nanoparticles and asphaltene.

[0029] (5) The high-salt shale oil produced fluid treatment method of the present invention has excellent salt resistance, high demulsification efficiency, fast speed and clear dewatering water quality;

[0030] (6) The method for treating high-salt shale oil produced fluid of the present invention has wide applicability. It is not only applicable to high-salt shale oil, but also has good effect on conventional high-salt crude oil produced fluid. Attached Figure Description

[0031] Figure 1 The dehydration rates of the various embodiments and comparative examples of the present invention are shown.

[0032] Figure 2The images show the dehydrated appearance of the salt-resistant demulsifier systems of various embodiments of the present invention after 2 hours of dehydration.

[0033] Figure 3 The images show the appearance of the salt-tolerant demulsifier systems of the present invention after 2 hours of dehydration (blank and comparative examples).

[0034] Figure 4 The images show the appearance of shale oil produced fluid before and after treatment with the salt-resistant demulsifier system in Example 1 of the present invention. Detailed Implementation

[0035] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0036] The salt-resistant demulsifier system of the present invention comprises a salt-resistant block polyether main agent, an amphoteric surfactant, and an organic acid decomplexing agent; wherein, the salt-resistant block polyether main agent is a star-shaped block copolymer with polyethylene oxide as the hydrophilic head, polypropylene oxide as the hydrophobic chain, and polyglycerol or pentaerythritol as the initiator; and the amphoteric surfactant is a sulfobetaine-type surfactant.

[0037] The salt-resistant demulsifier system of the present invention can effectively resist the negative effects of high mineralization (especially high divalent ion content) and can efficiently destroy shale oil emulsions stabilized by nanoparticles and asphaltene.

[0038] The main component of this salt-resistant demulsifier system is a star-shaped PEO-PPO block polyether. This star-shaped block polyether has multiple hydrophilic ends (PEO) and hydrophobic ends (PPO), and its three-dimensional structure is more conducive to interfacial adsorption. Compared to linear polyethers, it has a lower critical micelle concentration (CMC) and is less prone to precipitation in the presence of salt. The PEO segments can maintain a certain level of hydration in high-salt environments and, relying on their multi-site adsorption, can strongly penetrate into the interfacial film composed of asphaltene and nanoparticles.

[0039] Amphoteric surfactants possess excellent charge stabilization and membrane replacement properties. Sulfobetaine molecules carry both positive and negative charges, exhibiting stability in high ionic environments and remaining unaffected by salting-out. They can compete with negatively charged natural emulsifiers for interfacial sites, and their "counter-ionic layer" structure effectively resists the charge shielding effect of divalent cations, disrupting their "bridging" stability structure, thereby replacing and weakening the original interfacial membrane.

[0040] In addition, organic acid decomposition agents have ion chelation effects. The above three components work together through a synergistic mechanism of "osmotic destruction - charge stabilization - ion chelation". Each component has a clear function and works together on the interfacial membrane in a high-salt environment. The synergistic effect is strong and the overall performance far exceeds that of single components or conventional compound products, achieving efficient demulsification.

[0041] Preferably, the number average molecular weight of the salt-resistant block polyether main agent is 5000-15000.

[0042] Preferably, the sulfobetaine-type surfactant is octadecyl dihydroxyethyl sulfobetaine.

[0043] Preferably, the organic acid decomplexing agent is citric acid, ethylenediaminetetraacetic acid (EDTA), or gluconic acid; these organic acid decomplexing agents can react with Ca... 2+ Mg 2+ When divalent cations form stable water-soluble complexes, the concentration of free divalent ions in the solution is effectively reduced. This can directly break down the "ion bridges" formed between divalent ions at the interface, fundamentally dismantling the stable structure enhanced by salt, while preventing the effective components of the demulsifier from being deactivated due to calcium and magnesium precipitation.

[0044] Preferably, the composition and mass percentage of each component of the salt-resistant demulsifier system are as follows: 40%-70% salt-resistant block polyether main agent, 10%-30% zwitterionic surfactant, 5%-15% organic acid decomplexing agent, and the balance being solvent.

[0045] Preferably, the solvent is one or more of methanol, ethanol, and isopropanol.

[0046] The method for preparing the salt-resistant demulsifier system of the present invention involves first synthesizing a salt-resistant block polyether main agent, then mixing the components, heating and stirring to obtain the salt-resistant demulsifier system.

[0047] Specifically, the preparation method of the present invention includes the following steps:

[0048] S1. Synthesis of the main agent: In a high-pressure reactor, polyglycerol or pentaerythritol is used as the initiator. In the presence of a catalyst, propylene oxide is added first for polymerization, and then ethylene oxide is added for end-capping to obtain the salt-resistant block polyether main agent, namely star-shaped PEO-PPO block polyether.

[0049] Preferably, the catalyst is KOH.

[0050] Preferably, the synthesis conditions are as follows: under the conditions of a temperature of 115℃-120℃ and a pressure of 0.25-0.3MPa, the initiator and the first added propylene oxide are polymerized under the action of a catalyst, and then the temperature is lowered to 100℃-105℃, and ethylene oxide is added for end-capping.

[0051] Preferably, the polyglycerol has a molecular weight of less than or equal to 400, and the reaction system with propylene oxide is introduced at a temperature of 120°C and a pressure of 0.3 MPa to synthesize PPO segments with a molecular weight of approximately 4000. After cooling to 100°C, ethylene oxide (molecular weight approximately 2000) is introduced for end-capping to obtain a star-shaped block copolymer.

[0052] S2. Compounding: According to the above ratio, the star-shaped PEO-PPO block polyether synthesized in step S1, the zwitterionic surfactant, and the organic acid decomplexing agent are added to the solvent together.

[0053] S3. Mixing and Dissolving: Stir continuously at 40-60℃ for 2-4 hours until all components are completely dissolved and mixed evenly to obtain a clear or slightly turbid homogeneous liquid product.

[0054] The salt-tolerant demulsifier system of the present invention can be applied to treat produced fluids from high-salt shale oil. Specifically, the produced fluid from high-salt shale oil has a total salinity (TDS) greater than 150,000 mg / L and a concentration of divalent cations greater than 10,000 mg / L.

[0055] The method for treating high-salt shale oil produced fluid of the present invention includes the step of demulsification using a salt-resistant demulsifier system as described above; the amount of demulsifier system added to each high-salt shale oil produced fluid is 50-200 mg, and the demulsification temperature is 50-70°C.

[0056] The method for treating high-salt shale oil produced fluid of this invention utilizes a salt-resistant demulsifier system with excellent salt resistance. It not only exhibits good demulsification effects on high-salt crude oil produced fluids but also specifically targets high-salt produced fluids (TDS > 150,000 mg / L) and high concentrations of divalent ions (Ca). 2+ +Mg 2+ High-salt shale oil (>10000 mg / L) can still maintain high demulsification activity under these extreme conditions.

[0057] Meanwhile, this treatment method has high demulsification efficiency and speed, and can rapidly dehydrate high-salt shale oil emulsions, with a final dehydration rate of over 98%.

[0058] The dewatering water obtained using the treatment method of this invention is clear. Because this salt-resistant demulsifier system can effectively break down emulsions, the dewatered aqueous phase has a low oil content and is clearer, making it easier for subsequent treatment or reuse.

[0059] The effects of the present invention will be illustrated below through specific embodiments and comparative examples.

[0060] Example 1

[0061] This embodiment uses the method of the present invention to prepare the demulsifier system SE-1. The specific process is as follows:

[0062] S1. Using polyglycerol (molecular weight ~400) as a starting agent, PPO segments (molecular weight approximately 4000) were synthesized by introducing propylene oxide at 120°C and 0.3 MPa under KOH catalysis. Then, the temperature was lowered to 100°C, and ethylene oxide (molecular weight approximately 2000) was introduced for end-capping to obtain a star-shaped block copolymer.

[0063] The number-average molecular weight of the star-shaped block copolymer in this embodiment is 5000-7000.

[0064] S2. In a mixing vessel, add 50g of the above main agent, 20g of octadecyl dihydroxyethyl sulfobetaine, and 10g of citric acid, and then add 20g of ethanol to make up to 100g.

[0065] S3. Stir at 50℃ for 3 hours until homogeneous to obtain demulsifier system SE-1.

[0066] Example 2

[0067] In this embodiment, the demulsifier system SE-2 was prepared using the method of the present invention. The specific process was the same as in Example 1, except that the compounding ratio was changed in step S2 to: 60g of main agent, 15g of amphoteric surfactant, 8g of decomplexing agent, and 17g of solvent.

[0068] The zwitterionic surfactant is octadecyl dihydroxyethyl sulfobetaine, the decomplexing agent is EDTA, and the solvent is isopropanol.

[0069] Example 3

[0070] In this embodiment, the demulsifier system SE-3 was prepared using the method of the present invention. The specific process was the same as in Example 1, except that the compounding ratio was changed in step S2 as follows: 45g of main agent, 25g of amphoteric surfactant (cocamidopropyl hydroxysulfonyl betaine), 12g of decomplexing agent (gluconic acid), and 18g of solvent (methanol / ethanol = 1:1).

[0071] Example 4

[0072] In this embodiment, the demulsifier system SE-4 was prepared using the method of the present invention. The specific process was the same as in Example 1, except that in S1, pentaerythritol was used as the initiator to synthesize a star-shaped block copolymer (PPO molecular weight ~3000, PEO molecular weight ~1500).

[0073] The number-average molecular weight of the star-shaped block copolymer in this embodiment is 10,000-15,000.

[0074] Example 5

[0075] In this embodiment, the demulsifier system SE-5 was prepared using the method of the present invention. The specific process was the same as in Example 1, except that the compounding ratio was changed in step S2 to: 70g of main agent, 10g of amphoteric surfactant, 5g of decomplexing agent, and 15g of solvent.

[0076] The zwitterionic surfactant is octadecyl dihydroxyethyl sulfobetaine, the decomplexing agent is EDTA, and the solvent is isopropanol.

[0077] Comparative Example 1

[0078] This comparative example uses a traditional demulsifier, specifically a commercially available phenolic resin polyether type demulsifier (industrial grade SP-169).

[0079] Comparative Example 2

[0080] This comparative example uses only the star-shaped block copolymer synthesized in this invention as a demulsifier, without adding zwitterionic surfactants or decomplexing agents.

[0081] Performance tests were conducted on the demulsifier systems of the above embodiments and the demulsifiers of the comparative examples, with no demulsifier added as a blank. The specific experimental procedures and results are as follows:

[0082] 1. Demulsification performance test: Take 100 mL of a high-salt shale oil produced fluid (water content 40%, TDS = 180000 mg / L, of which Ca...) 2+ +Mg 2+ =12000 mg / L, apparent viscosity at 50℃ >1000 mPa·s) was added to a stoppered graduated cylinder. 150 mg / L of the demulsifier to be tested was added to each cylinder. The cylinders were incubated in a 65℃ water bath, and the amount of water removed at different times was recorded, the color of the removed water was observed, and the dehydration rate was calculated. The results are shown in Table 1 and Table 2. Figure 1 The water removed after 2 hours appears as follows Figure 2 and 3 As shown.

[0083] Table 1. Dehydration rates of each example and comparative example

[0084]

[0085] According to Table 1 and Figure 1 As can be seen, under the extreme high-salt conditions described in this invention, the demulsifier system (SE-1 to SE-3) of this invention is far superior to the traditional demulsifier (Comparative Example 1) and the single main agent (Comparative Example 2) in both dehydration speed and final dehydration rate, and can obtain clear dehydrated water. Salt tolerance tests further demonstrate the broad applicable salinity range of the system of this invention.

[0086] 2. Salt tolerance comparison test: Simulated saline solutions with different mineralization (TDS from 50,000 mg / L to 250,000 mg / L) were prepared to prepare emulsions, and the final dehydration rates of Example 1 and Comparative Example 1 were tested under the same dosage.

[0087] Tests showed that when TDS > 100,000 mg / L, the dehydration rate of Comparative Example 1 decreased significantly to below 80%, while the dehydration rate of the product in Example 1 remained above 95% when TDS = 250,000 mg / L.

[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A salt-resistant demulsifier system, characterized in that, The components of the salt-resistant demulsifier system include a salt-resistant block polyether main agent, an amphoteric surfactant, and an organic acid decomplexing agent; The salt-resistant block polyether main agent is a star-shaped block copolymer with polyethylene oxide as the hydrophilic head, polypropylene oxide as the hydrophobic chain, and polyglycerol or pentaerythritol as the initiator; the zwitterionic surfactant is a sulfobetaine-type surfactant. The organic acid decomplexing agent is ethylenediaminetetraacetic acid or gluconic acid; The composition and mass percentage of the salt-resistant demulsifier system are as follows: 40%-70% salt-resistant block polyether main agent, 10%-30% zwitterionic surfactant, 5%-15% organic acid decomplexing agent, and the balance being solvent. The salt-resistant demulsifier system is used to treat produced fluid from high-salt shale oil, wherein the salinity (TDS) of the produced fluid is greater than 150,000 mg / L and the concentration of divalent metal cations is greater than 10,000 mg / L.

2. The salt-resistant demulsifier system according to claim 1, characterized in that, The number-average molecular weight of the star-shaped block copolymer is 5000-15000.

3. The salt-resistant demulsifier system according to claim 1, characterized in that, The solvent is one or more of methanol, ethanol, and isopropanol.

4. A method for preparing a salt-resistant demulsifier system as described in any one of claims 1-3, characterized in that, First, the salt-resistant block polyether main agent is synthesized, then the components are mixed, heated and stirred to obtain the salt-resistant demulsifier system.

5. The method for preparing a salt-resistant demulsifier system according to claim 4, characterized in that, The method for synthesizing the salt-resistant block polyether main agent is as follows: under the conditions of temperature of 115℃-120℃ and pressure of 0.25-0.3MPa, polyglycerol or pentaerythritol is used as the initiator, and propylene oxide is added first for polymerization under the action of a catalyst. Then, the temperature is lowered to 100℃-105℃ and ethylene oxide is added for end-capping.

6. The method for preparing a salt-resistant demulsifier system according to claim 4, characterized in that, After mixing all the ingredients, heat the mixture to 40-60℃ and stir for 2-4 hours.

7. The application of the salt-tolerant demulsifier system as described in any one of claims 1-3 in the treatment of produced fluids from high-salt shale oil, characterized in that, The produced fluid of the high-salt shale oil has a mineralization TDS greater than 150,000 mg / L and a concentration of divalent metal cations greater than 10,000 mg / L.

8. A method for treating produced fluid from high-salinity shale oil, characterized in that, The method includes the step of demulsification using a salt-tolerant demulsifier system as described in any one of claims 1-3; the amount of the demulsifier system added per liter of the high-salt shale oil produced fluid is 50-200 mg, and the demulsification temperature is 50-70°C.

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