A compound reverse demulsifier, its preparation method and application

Abstract

This invention relates to a compound reverse demulsifier, its preparation method, and its application, relating to the fields of oil and gas field applied chemistry and environmental protection technology. The compound reverse demulsifier comprises a polyether polyquaternary ammonium salt and a flocculant, wherein the mass ratio of the polyether polyquaternary ammonium salt to the flocculant is (7-8):(2-3). The compound reverse demulsifier provided by this invention promotes the flocculation and aggregation of oil droplets by neutralizing the negative charge on the surface of oil droplets in O / W emulsions. The flocculant mainly addresses the problems of droplet flocculation, aggregation, and floc sedimentation after demulsification. The combination of polyether polyquaternary ammonium salt and flocculant exerts a synergistic effect of "displacement, charge neutralization, compression of the double electric layer, and flocculation aggregation," making O / W type emulsion produced water easier to destabilize, flocculate, and separate. Furthermore, the compound reverse demulsifier provided by this invention is stable at room temperature, can be stored for a long time, is low in cost, has good water solubility, is easy to use, and can rapidly demulsify gas field produced water under low temperature and low dosage conditions.

Description

Technical Field

[0001] This invention relates to the fields of applied chemistry and environmental protection technology in oil and gas fields, specifically to a compound reverse demulsifier, its preparation method, and its application. Background Technology

[0002] Unconventional natural gas refers to natural gas reservoirs where conventional extraction techniques typically cannot yield economically viable yields. It mainly includes three types: tight gas (TG), shale gas (SG), and coalbed methane (CBM). Currently, tight gas (TG) production accounts for 70.1% of my country's unconventional gas production. Unconventional natural gas development carries risks of high water consumption and environmental pollution. For example, produced water from gas fields forms a complex oil-water emulsion system—oil-containing emulsion produced water—with a complex composition, high salt and oil content, high suspended solids content, and complex organic matter composition, making produced water treatment highly challenging.

[0003] The challenge in treating oil-bearing emulsified produced water from unconventional gas fields lies in destabilization, with the focus on effectively removing oil and suspended solids. However, the "sedimentation (flotation) + filtration" process generally suffers from low treatment load, poor treatment effect, and high cost. To ensure treatment effectiveness without substantially altering the existing water treatment processes and equipment in the gas field, priority should be given to addressing the destabilization and sedimentation of oil-bearing emulsified wastewater. Chemical demulsification and oil removal are crucial components of conventional natural gas produced water treatment processes.

[0004] Currently, there are many types of reverse demulsifiers for treating produced water from oil fields, and they are effective. However, some problems still exist. First, some cationic polymer reverse demulsifiers have a fast demulsification speed and good oil removal effect, but the resulting flocs can adhere to pipelines and tanks, and may generate a lot of sludge during the demulsification process, thus reducing treatment efficiency. Nonionic reverse demulsifiers are not as good as cationic reverse demulsifiers in terms of oil-water separation speed and deep water purification effect. Dendritic macromolecules are suitable for O / W emulsions with high oil content, but their demulsification effect is worse for O / W emulsions with very low oil content. Second, some reagents have high costs, high demulsification temperatures, and long treatment times. Third, these reverse demulsifiers are currently designed for demulsification problems of O / W emulsions in conventional oil and gas fields, and there are no commercial demulsifiers specifically for produced water from unconventional natural gas O / W emulsions. Therefore, how to efficiently and cost-effectively solve the problem of treating produced water from unconventional gas fields containing oil emulsions has become one of the urgent problems to be solved in gas field production. In view of this, the present invention provides a compound reverse demulsifier, its preparation method and application. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a compound reverse demulsifier, its preparation method, and its application. The aim is to provide a compound reverse demulsifier suitable for treating unconventional gas O / W type emulsion produced water, which has advantages such as low environmental requirements, fast oil removal speed, clear dewatering water, and low oil content after treatment.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] In a first aspect, a compound reverse demulsifier comprises a polyether polyquaternary ammonium salt and a flocculant, wherein the mass ratio of the polyether polyquaternary ammonium salt to the flocculant is (7-8):(2-3).

[0008] The beneficial effects of this invention are:

[0009] (1) The compound reverse demulsifier provided by this invention promotes the flocculation and aggregation of oil droplets by neutralizing the negative charge on the surface of oil droplets in O / W emulsions; wherein the demulsifier polyether polyquaternary ammonium salt (PEPA-12) is a hydrophilic cationic reverse demulsifier, which mainly solves the problem of produced water emulsification. It has a large molecular weight, a large number of branched structures, a large oil-water interface area and high interfacial activity. It is easy to adsorb and replace various emulsifiers on the oil-water interface, reduce the stability of the interfacial film, and has strong environmental adaptability. It exhibits excellent low-temperature demulsification performance. The demulsifier PEPA-12 can also neutralize the negative charge on the surface of O / W droplets, weaken the repulsive force between oil droplets, and make it easier for small oil droplets to aggregate into large oil droplets. The flocculant (PAFC-01) mainly solves the problems of flocculation, aggregation, and floc sedimentation of microdroplets after demulsification. The combination of polyether polyquaternary ammonium salt PEPA-12 and flocculant (PAFC-01) plays a synergistic role in "displacement, charge neutralization, compression of the double electric layer, and flocculation aggregation", making O / W type emulsion produced water easier to destabilize, flocculate, settle, and separate.

[0010] (2) The compound reverse demulsifier provided by the present invention is stable at room temperature, can be stored for a long time, has low cost, good water solubility, and is easy to use. It can quickly demulsify gas field produced water under low temperature and low dosage conditions. When the compound ratio is 4:1 and the dosage is 500mg / L, the oil content of the treated water is <30mg / L and SS≤15mg / L.

[0011] Based on the above technical solution, the present invention can be further improved as follows.

[0012] Furthermore, the mass ratio of the polyether polyquaternary ammonium salt to the flocculant is 4:1.

[0013] Furthermore, the molecular structure of the polyether polyquaternary ammonium salt is shown in formula (1):

[0014] In formula (1), the value of a ranges from 30 to 99, the value of b ranges from 20 to 69, the value of m ranges from 10 to 90, and the value of n ranges from 10 to 90.

[0015] Furthermore, the flocculant is mainly made of acidified backflow solution, bauxite and ferric chloride, and the mass ratio of the acidified backflow solution, the bauxite and the ferric chloride is 10:(1.25-2.0):(0-0.2).

[0016] The beneficial effects of adopting the above-mentioned further solutions are as follows: The flocculant of the present invention can reuse the acidification backflow liquid of oil and gas fields. It can be acidified with hydrochloric acid. The hydrochloric acid acidification backflow liquid of oil and gas fields belongs to national hazardous waste (HW34). The total iron content of the hydrochloric acid acidification backflow liquid of oil and gas fields is generally about 0.1-100g / L and the aluminum content is 0.1-100g / L. In contrast, the total iron concentration of commercially available polyferric chloride products is generally 100-200g / L. When preparing PAFC-01 using waste acidification liquid as raw material, adding appropriate amounts of bauxite, iron salts and stabilizers can achieve 100 days of stability without gelation, thus realizing the treatment of waste with waste.

[0017] Furthermore, the acidification flowback solution comprises iron salts and aluminum salts, wherein the iron salt mass concentration is 1-100 g / L and the aluminum salt mass concentration is 0.1-100 g / L; the alumina mass content in the bauxite is 60-80%. The acidification flowback solution also contains Mg. 2+ Ca 2+ K + Cl - Due to the different acidified strata, some also contain heavy metal ions dissolved from the rocks and minerals of the strata, as well as residual acidification fluid additives, such as CuI, CuCl corrosion inhibitors, and drainage aids.

[0018] Secondly, a method for preparing a compound reverse demulsifier includes the following steps: mixing a polyether polyquaternary ammonium salt and a flocculant to obtain a compound reverse demulsifier.

[0019] Furthermore, the polyether polyquaternary ammonium salt includes the following preparation steps: using a pentagonal copolymer polyether demulsifier X-75 as raw material, it is obtained through quaternization cationic modification. The pentagonal copolymer polyether demulsifier X-75 is specifically disclosed in CN113416576 A.

[0020] Furthermore, the polyether polyquaternary ammonium salt comprises the following specific preparation steps: dissolving the pentagonal copolymer polyether demulsifier X-75 in a solvent (e.g., chloroform), and adding a phosphorus tribromide solution (e.g., phosphorus tribromide chloroform solution) dropwise at 5-10°C, wherein the ratio of the pentagonal copolymer polyether demulsifier X-75 to phosphorus tribromide is (10-20) g: (0.25-0.75) mol; after addition, heating to 55-60°C for reflux reaction for 120-150 min, and then cooling. After reaching room temperature, an alkaline aqueous solution (e.g., sodium hydroxide aqueous solution) is added to separate the layers. The solvent in the lower layer is removed by vacuum distillation or by drying with anhydrous sodium sulfate. Then, it is refluxed with dodecyl dimethyl tertiary amine in anhydrous ethanol for 4-6 days. The ratio of the demulsifier X-75 to dodecyl dimethyl tertiary amine is (10-20) g: (0.25-0.75) mol. The solvent is removed again by vacuum distillation to obtain the polyether polyquaternary ammonium salt.

[0021] When using an aqueous solution of sodium hydroxide for stratification, the concentration of sodium hydroxide in the aqueous solution only needs to meet the requirements, such as 0.1 mol / L.

[0022] Furthermore, the flocculant includes the following specific preparation steps: taking the filtered acidified backflow liquid, oxidizing the ferrous ions in the acidified backflow liquid to ferric ions (for example, adding sodium hypochlorite for oxidation), then adding bauxite and ferric chloride, stirring and reacting at 60-75℃ for 2-4 hours, controlling the basicity to 20-60% (calculated as aluminum and iron), then filtering while hot, adding a stabilizer (such as sodium phosphate) to the filtrate, reacting at 60-75℃ for 2-4 hours, cooling to room temperature and aging to obtain the flocculant (PAFC-01).

[0023] Secondly, the application of a compound reverse demulsifier involves using the aforementioned compound reverse demulsifier in the treatment of unconventional natural gas emulsion produced water.

[0024] In specific applications, the above-mentioned compound reverse demulsifier is added at a rate of 500 mg / L. The temperature of the produced water is controlled at 25-30℃. After addition, the mixture is stirred and kept at 25-30℃ for more than 30 minutes to achieve demulsification and separation. Attached Figure Description

[0025] Figure 1 This is an infrared scan of the main components in the compounded reverse demulsifier in Example 1 of the present invention.

[0026] Figure 2 This is a comparison of images of PEPA-12 and the compound reverse demulsifier product in Example 1 of the present invention. The left side shows PEPA-12, and the right side shows the compound reverse demulsifier.

[0027] Figure 3 This is a diagram showing the demulsification state in Embodiment 3 of the present invention.

[0028] Figure 4 This is a diagram illustrating the demulsification effect in Embodiment 4 of the present invention. Detailed Implementation

[0029] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0030] Example 1

[0031] This embodiment relates to a method for preparing a compound reverse demulsifier, comprising the following steps:

[0032] (1) Preparation of compound reverse demulsifier polyether polyquaternary ammonium salt PEPA-12:

[0033] Weigh 15g of the five-component copolymer polyether demulsifier X-75 and dissolve it in 150mL of chloroform. At 5℃, add a chloroform solution of phosphorus tribromide (0.5mol phosphorus tribromide dissolved in 50mL chloroform) dropwise to the above solution. After the addition is complete, gradually increase the reaction temperature to 55-60℃ and reflux for 120min. After cooling to room temperature, add 50mL of a 20mol / L sodium hydroxide aqueous solution. After standing and separating the layers, separate the lower layer, dry with anhydrous sodium sulfate, and remove the solvent under reduced pressure to 2kPa. React the obtained product with 0.5mol of dodecyl dimethyl tertiary amine in 100mL of anhydrous ethanol at 75-80℃ for 5 days. After removing the solvent under reduced pressure, obtain the quaternary ammonium salt copolymer cationic demulsifier PEPA-12. Based on the chemical reaction principle, a quaternary ammonium group is added to the molecular structure of the five-component polyether. Combined with infrared spectroscopy, the derived molecular structure is as follows:

[0034] Where a ranges from 30 to 99, b ranges from 20 to 69, m ranges from 10 to 90, and n ranges from 10 to 90.

[0035] (2) Preparation of flocculant (PAFC-01):

[0036] It uses hydrochloric acid acidification flowback fluid from oil and gas fields as raw material. The total iron, aluminum, magnesium and calcium contents in the four hydrochloric acid acidification flowback fluids collected from the gas field in this application are 52.8 g / L, 82.3 g / L, 13.6 g / L and 16.7 g / L, respectively.

[0037] Take 500 ml of filtered gas field hydrochloric acid acidified flowback liquid into a three-necked flask and place it on a water bath. Add 14.0 ml of sodium hypochlorite while stirring at room temperature to oxidize ferrous ions to ferric ions. Then add 294.35 g of bauxite containing 60% alumina to the three-necked flask and stir for 30 min to maximize the dissolution of aluminum in the liquid phase. Add alkali to control the basicity to 53% (based on aluminum and iron), and stir at 60°C for 3 h to allow it to undergo complex polymerization with iron and other metal ions. Filter while hot, add 13.51 g of phosphate stabilizer to the filtrate, react at 65°C for 3 h, cool to room temperature and mature for 24 h to obtain an inorganic polymeric flocculant (PAFC-01) mainly composed of aluminum and iron and containing multiple metal ions. It is stable for 100 days without gelation.

[0038] (3) Preparation of compound reverse demulsifiers:

[0039] PEPA-12 and flocculant (PAFC-01) were directly mixed evenly at different mass ratios to obtain a compound reverse demulsifier.

[0040] A compound reverse demulsifier (CQ-01) was obtained by mixing PEPA-12 and PAFC-01 at a mass ratio of 4:1. The infrared scanning results are shown in the figure. Figure 1 It was observed that it was located at 3421.8cm -1 The strong and broad absorption peak at 1632.9 cm⁻¹ is attributed to the superposition of the stretching vibrations of OH and NH in PEPA-12 and Fe-OH and Al-OH in PAFC-01. -1 The corresponding deformation vibrations appear on the left and right sides; 1078.4cm -1 The point represents the stretching vibration of the CN bond; 983.1 cm. -1 The superposition of CO stretching vibration and Al-OH bending vibration; and 1401.0 cm -1 The distinct band at 620 cm⁻¹ represents the deformation vibration of -CH₃ bonded to N⁺ (quaternary ammonium nitrogen); -1 The point is where Al-OH undergoes overall bending vibration.

[0041] A comparison of images of PEPA-12 and the compound reverse demulsifier (PEPA-12 to PAFC-01 mass ratio of 4:1) can be found in the image below. Figure 2 On the left is PEPA-12, a dark brown liquid that exhibits typical surfactant characteristics—bubbles—on the surface after shaking. On the right is a compound reverse demulsifier (CQ-01), a light yellow liquid made by mixing PEPA-12 with flocculant (PAFC-01) at a mass ratio of 4:1. It is stable for a long time without stratification, discoloration, or precipitation.

[0042] Example 2

[0043] The compound reverse demulsifier was prepared according to the method in Example 1, wherein five compound reverse demulsifiers were set with mass ratios of PEPA-12 to PAFC-01 of 1:4, 2:3, 1:1, 3:2, and 4:1.

[0044] Before the experiment, unconventional natural gas emulsion produced water was collected, and its original oil content, turbidity, and suspended solids were measured to be 72.63 mg / L, 158 NTU, and 185.5 mg / L, respectively. Then, 100 mL of unconventional natural gas emulsion produced water was placed in a beaker, and five groups were set up, with each group repeated at least three times. The beaker was first preheated in a 30°C constant temperature water bath for 10 min. Then, a compound reverse demulsifier was added at a concentration of 500 mg / L, and the mixture was manually stirred vigorously for 100 times. The beakers after adding the reagent were then heated in a 30°C constant temperature water bath for 30 min. The supernatant was then taken and its absorbance A was measured using a spectrophotometer, and the turbidity was calculated (the standard curve equation for turbidity calculation is: Turbidity = (A - 0) / (Turbidity ... The oil content was calculated by taking 25 mL of the supernatant and placing it in a separatory funnel. Then, 50 mL of petroleum ether (boiling range 30-60℃) was added for extraction. This was repeated twice. The absorbance A was measured using a TU-1900 UV-Vis spectrophotometer. The oil content was calculated (the standard curve equation for oil content is: C = 4A ÷ 0.0114), and the oil removal rate was calculated (oil removal rate = (C0 - C) ÷ C0 × %). The specific results are shown in Table 1 below:

[0045] Table 1. Comparison of the effects of different formulations of PEPA-12 and PAFC-01 on the demulsification effect in produced water.

[0046]

[0047] Note: Before treatment, the absorbance of turbidity A = 0.5496, and the turbidity is 158 NTU; before treatment, the absorbance of oil content A = 0.207, and the oil content is 72.63 mg / L.

[0048] The results showed that a 4:1 ratio of PEPA-12 to PAFC-01 yielded the best turbidity and oil removal effects. At other ratios, the formation of a large number of flocs, which failed to settle effectively within 30 minutes, led to increased turbidity and negative turbidity removal rates. Since PAFC-01 is only about 30% the price of PEPA-12, and its addition promotes rapid aggregation and sedimentation, it is feasible to partially replace PEPA-12 by adding PAFC-01.

[0049] Example 3

[0050] The effects of application temperature and dosage on the compounded reverse demulsifier with a mass ratio of PEPA-12 to PAFC-01 of 4:1 as described in Example 2 were studied.

[0051] (1) Effect of temperature

[0052] Demulsification and flocculation experiments were conducted at four temperature gradients: 15, 20, 25, and 30°C. The raw water quality indicators and other methods were the same as in Example 2. To avoid randomness in the results, each temperature was tested twice in parallel. After 30 minutes, the supernatant was collected to measure turbidity and oil content. Specific results are shown in Table 2. The demulsification state diagram is shown below. Figure 3 .

[0053] Table 2. Effect of different temperatures on the efficacy of reverse demulsifiers

[0054]

[0055] The results in Table 2 show that temperature changes have little impact on the oil removal effect; an oil content of <30 mg / L can be achieved at all temperatures. Temperature mainly affects the reaction between the reagent and colloidal particles and oil droplets in the water, thus affecting the water treatment effect. Generally, the higher the temperature, the easier the water treatment, but the higher the energy consumption.

[0056] (2) Effect of dosage

[0057] The effect of the dosage on the demulsification effect was studied using the 4:1 ratio of PEPA-12 to PAFC-01 compound reverse demulsifier from Example 2. Doses were 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, and 600 mg / L, with two groups for each dosage. Specific effects are shown in Table 3 below.

[0058] Table 3. Effects of different dosages of reverse demulsifier on the effect of the demulsifier

[0059]

[0060]

[0061] Table 3 shows that turbidity increased instead of decreased when the reagent dosage was low, indicating the formation of a large number of tiny flocs. However, due to the low concentration, these flocs were difficult to aggregate and settle. As the dosage of the compound reagent increased, the removal rates of turbidity and oil content in the water improved. The demulsification effect was best at a dosage of 500 mg / L, meeting the assessment criteria. Further increasing the reagent dosage did not significantly change the demulsification effect.

[0062] Example 4

[0063] To verify the treatment effect, the experimental scale was appropriately increased, with the wastewater volume increased from 100ml to 200ml and then to 500ml. 200mL of produced water from the Third Gas Production Plant of PetroChina Gas Field was placed in a beaker and preheated in a 30℃ constant temperature water bath for 10 minutes. Then, a 500mg / L reverse demulsifier (PEPA-12:PAFC-01 mass ratio of 4:1) was added, and the mixture was manually stirred vigorously 100 times. The beakers after adding the reagent were then placed in a... After heating in a 30℃ constant temperature water bath for 30 min, the supernatant was taken and its absorbance A was measured by a spectrophotometer, and the turbidity was calculated. Another 25 mL of the supernatant was placed in a separatory funnel, and 50 mL of petroleum ether (boiling range 30–60℃) was added for extraction. This process was repeated twice. The oil content was measured using a TU-1900 UV-Vis spectrophotometer, and the oil removal rate was calculated. The suspended solids in the extracted water were determined according to GB / T11901-1989, "Determination of Suspended Solids in Water - Gravimetric Method". The color of the extracted water was determined according to HJ 1182-2021, "Determination of Color in Water - Dilution Factor Method". Specific data are shown in Table 4. Specific demulsification effects are shown in... Figure 4 :

[0064] Table 4. Detection results of the scaled-up experiment

[0065]

[0066] The experimental results in Table 4 show that the compound reverse demulsifier prepared by the method of the present invention for producing gas field emulsion water can still efficiently and rapidly neutralize the negative charge of oil droplets and suspended solids in the water in the scale-up experiment. It has high efficiency in removing turbidity and suspended solids. After treatment, the suspended solids are less than 15 mg / L and the oil content is less than 30 mg / L (China Petroleum and Natural Gas Industry Standard "Gas Field Water Reinjection Method" (SY-T6596-2004)). These are the recommended water quality indicators for gas field water reinjection, indicating that the compound reverse demulsifier has stable performance.

[0067] Example 5

[0068] Before the experiment, unconventional natural gas emulsified produced water was collected and its original oil content and turbidity were measured to be 69.123 mg / L (absorbance A) and 158 NTU (absorbance A = 0.197), respectively. The produced water was then treated with X-75, PEPA-12, PAFC-01, commercially available polyaluminum ferric chloride (PAFC), commercially available PAC (polyaluminum chloride), and the compound reverse demulsifier of this invention (PEPA-12 and PAFC-01 in a mass ratio of 4:1). The dosage added to the produced water was 500 mg / L. Demulsification was performed at room temperature (25°C), and after stirring, the mixture was allowed to stand for 30 minutes before sampling and testing. Specific results are shown in Table 5 below.

[0069] Table 5 Results of the control experiment

[0070]

[0071]

[0072] Because condensate oil is volatile, the specific condensate oil content and turbidity in the original water sample are based on the values ​​measured in each experiment, which is 69.123 mg / L (absorbance A = 0.197).

[0073] Table 5 shows that PAC alone has a good flocculation effect. The inventors further studied the effect of combining it with PEPA-12. PEPA-12, PAC, and PEPA-12, PAC were combined in ratios of 1:4, 3:7, 2:3, 1:1, 3:2, 7:3, and 4:1 for the treatment of produced water. The specific effects are shown in Table 6 below.

[0074] Table 6. Experimental results of PEPA-12 and PAC compound.

[0075]

[0076] As shown in Table 6, the combination of PEPA-12 and PAC significantly affects sedimentation efficiency and demulsification and oil removal effects, resulting in a worse effect compared to using the agents alone. However, the combination of PEPA-12 and PAFC-01 has a synergistic effect.

[0077] In summary, the compounded reverse demulsifier provided by this invention promotes the flocculation and aggregation of oil droplets by neutralizing the negative charge on the surface of oil droplets in O / W emulsions. The demulsifier, polyether polyquaternary ammonium salt (PEPA-12), is a hydrophilic cationic reverse demulsifier that primarily addresses the emulsification problem of produced water. It possesses a large molecular weight, numerous branched structures, a large oil-water interface area, and high interfacial activity, making it easy to adsorb and replace various emulsifiers at the oil-water interface, reducing the stability of the interfacial film, and exhibiting good environmental adaptability. It has strong demulsification performance at low temperatures; the demulsifier PEPA-12 can also neutralize the negative charge on the surface of O / W droplets, weaken the repulsive force between oil droplets, and make small oil droplets easier to aggregate into large oil droplets; the flocculant (PAFC-01) mainly solves the problems of flocculation, aggregation and sedimentation of microdroplets after demulsification; the polyether polyquaternary ammonium salt PEPA-12 and the flocculant (PAFC-01) play a synergistic role of "displacement, charge neutralization, compression of double electric layer and flocculation aggregation", making O / W type emulsion produced water easier to destabilize, flocculate and settle.

[0078] The compound reverse demulsifier provided by this invention is stable at room temperature, can be stored for a long time, is low in cost, has good water solubility, and is easy to use. It can rapidly demulsify gas field produced water under low temperature and low dosage conditions. When the compound ratio is 4:1 and the dosage is 500mg / L, the oil content of the treated water is <30mg / L and SS≤15mg / L.

[0079] 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 compound reverse demulsifier, characterized in that, The compound reverse demulsifier comprises a polyether polyquaternary ammonium salt and a flocculant, wherein the mass ratio of the polyether polyquaternary ammonium salt to the flocculant is (7-8):(2-3). The polyether polyquaternary ammonium salt is prepared by the following steps: using a five-component copolymer polyether demulsifier X-75 as raw material, it is obtained by quaternization cationic modification.

2. The compounded reverse demulsifier according to claim 1, characterized in that, The mass ratio of the polyether polyquaternary ammonium salt to the flocculant is 4:

1.

3. A compound reverse demulsifier according to claim 1 or 2, characterized in that, The flocculant is mainly made of acidified backflow solution, bauxite and ferric chloride, and the mass ratio of the acidified backflow solution, the bauxite and the ferric chloride is 10:(1.25-2.0):(0-0.2).

4. The compounded reverse demulsifier according to claim 3, characterized in that, The acidified flowback solution includes iron salts and aluminum salts, wherein the iron salt mass concentration is 1-100 g / L and the aluminum salt mass concentration is 0.1-100 g / L; the alumina mass content in the bauxite is 60-80%.

5. A method for preparing a compound reverse demulsifier according to any one of claims 1 to 4, characterized in that, The process includes the following steps: mixing polyether polyquaternary ammonium salt and flocculant to obtain a compound reverse demulsifier.

6. The method for preparing a compound reverse demulsifier according to claim 5, characterized in that, The polyether polyquaternary ammonium salt comprises the following specific preparation steps: dissolving the pentyl copolymer polyether demulsifier X-75 in a solvent, adding phosphorus tribromide solution dropwise at 5-10℃, wherein the ratio of the pentyl copolymer polyether demulsifier X-75 to phosphorus tribromide is (10-20) g: (0.25-0.75) mol, after addition, heating to 55-60℃ for reflux reaction for 120-150 min, then cooling to room temperature and adding alkaline aqueous solution for separation, removing the solvent from the lower layer solution by vacuum distillation, and then refluxing with dodecyl dimethyl tertiary amine in anhydrous ethanol for 4-6 days, wherein the ratio of the pentyl copolymer polyether demulsifier X-75 to dodecyl dimethyl tertiary amine is (10-20) g: (0.25-0.75) mol, removing the solvent again by vacuum distillation to obtain the polyether polyquaternary ammonium salt.

7. The method for preparing a compound reverse demulsifier according to claim 5, characterized in that, The flocculant comprises the following specific preparation steps: Take the filtered acidified backflow liquid, oxidize the ferrous ions in the acidified backflow liquid to ferric ions, then add bauxite and ferric chloride, stir and react at 60-75℃ for 2-4 hours, control the basicity to 20-60%, then filter while hot, add a stabilizer to the filtrate, react at 60-75℃ for 2-4 hours, cool to room temperature and mature to obtain the flocculant.

8. The application of a compounded reverse demulsifier, characterized in that, The compound reverse demulsifier according to any one of claims 1 to 4 is used in the treatment of unconventional natural gas emulsion produced water.

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