Compound reverse demulsifier as well as preparation method and application thereof

Abstract

The invention relates to a compound reverse demulsifier and a preparation method and application thereof, and relates to the technical field of oil and gas field applied chemistry and environmental protection, the compound reverse demulsifier comprises a polyether multi-quaternary ammonium salt and a flocculant, and the mass ratio of the polyether multi-quaternary ammonium salt to the flocculant is (7-8): (2-3). According to the compound reverse demulsifier provided by the invention, by neutralizing negative charges on the surfaces of oil drops in O / W emulsion, flocculation and coalescence of the oil drops are promoted, and the flocculant mainly solves the problems of flocculation, coalescence and floc sedimentation of the micro-drops after demulsification; the polyether polyquaternary ammonium salt and the flocculating agent are compounded to exert the synergistic interaction effect of displacement, charge neutralization, compression of double electric layers and flocculation and aggregation, so that the O / W type emulsified produced water is easy to destabilize, flocculate, settle and separate; the compound reverse demulsifier provided by the invention is stable in property at normal temperature, can be stored for a long time, is low in cost, good in water solubility and convenient to use, and can be used for quickly demulsifying gas field produced water under the conditions of low temperature and low dosage.

Description

Technical Field

[0001] The invention relates to the field of oil and gas field applied chemistry and environmental protection technology, and in particular to a compound reverse phase demulsifier and a preparation method and application thereof. Background Art

[0002] Unconventional natural gas refers to natural gas reservoirs that cannot be economically produced using traditional mining technology. It mainly includes three types: tight gas (TG), shale gas (SG) and coalbed methane (CBM). At present, the production of tight gas (TG) in my country accounts for 70.1% of the production of unconventional gas. The development of unconventional natural gas involves large water consumption and environmental pollution risks. For example, the produced water from the gas field forms a complex oil-water emulsion system - oil-containing emulsified produced water. The produced water has complex components, high salt and oil content, high suspended matter content, and complex organic components, making it difficult to treat the produced water.

[0003] The difficulty of treating oil-containing emulsified produced water from unconventional gas fields is destabilization, and the focus of treatment is to effectively remove oil and suspended solids. However, the "sedimentation (flotation) + filtration" process generally has problems such as low treatment load, poor treatment effect, and high cost. In order to ensure the treatment effect without substantially changing the existing water treatment process equipment of the gas field, the destabilization and sedimentation problems of oil-containing emulsified wastewater should be solved first. Chemical demulsification and oil removal is an important part of the conventional natural gas produced water treatment process.

[0004] At present, there are many types of reverse demulsifiers for treating oilfield produced water, and the effect is excellent, but there are still some problems. First, some cationic polymer reverse demulsifiers have fast demulsification speed and good oil removal effect, but the flocs formed will adhere to the pipes and tanks, and a lot of sludge may be produced during the demulsification process, thereby reducing the treatment efficiency; non-ionic reverse demulsifiers are not as good as cationic reverse demulsifiers in 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 will become worse for O / W emulsions with very low oil content. Second, some agents have high cost, high demulsification temperature, and long treatment time. Third, these reverse demulsifiers are currently aimed at the demulsification of O / W emulsions in conventional oil and gas fields, and there is no commercial demulsifier specifically for unconventional natural gas O / W emulsified produced water. Therefore, how to efficiently and low-costly solve the problem of treating oil-containing emulsified produced water in unconventional gas fields 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 and a preparation method and application thereof. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a composite reverse demulsifier and its preparation method and application. The purpose is to provide a composite reverse demulsifier suitable for the treatment of unconventional gas O / W type emulsified produced water, which has the advantages of low use environment requirements, fast deoiling speed, clear deoiled water, and low oil content after treatment.

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

[0007] In a first aspect, a compound reverse demulsifier is provided, comprising 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 the present invention are:

[0009] (1) The composite reverse demulsifier provided by the present invention promotes the flocculation and coalescence of oil droplets by neutralizing the negative charge on the surface of oil droplets in the O / W emulsion; 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 a high interfacial activity, is easy to adsorb and replace a variety of emulsifiers on the oil-water interface, reduces the stability of the interface film, and has strong environmental adaptability. , good 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 small oil droplets easily aggregate into large oil droplets; the flocculant (PAFC-01) mainly solves the flocculation, coalescence and flocculent sedimentation problems of droplets after demulsification; the polyether polyquaternary ammonium salt PEPA-12 and the flocculant (PAFC-01) are compounded to play the synergistic effect of "displacement, electrical neutralization, compression of double electric layer and flocculation aggregation", making the O / W emulsified produced water easy to destabilize, flocculate and separate;

[0010] (2) The composite 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, is easy to use, and can quickly demulsify gas field produced water under low temperature and low dosage conditions; when the composite ratio is 4:1 and the dosage is 500 mg / L, the oil content of the treated water is <30 mg / L and SS ≤15 mg / L.

[0011] Based on the above technical solution, the present invention can also be 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), 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.

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

[0016] The beneficial effect of adopting the above further scheme is that the flocculant of the present invention can reuse the oil and gas field acidification return fluid, and hydrochloric acid can be used for acidification. The oil and gas field hydrochloric acid acidification return fluid belongs to the national hazardous waste (HW34). The oil and gas field hydrochloric acid acidification return fluid (generally has a total iron content of about 0.1-100g / L and an aluminum content of 0.1-100g / L), and the total iron mass concentration in the general commercially available polyferric chloride product is 100-200g / L. When PAFC-01 is prepared using the waste acidification liquid as a raw material, bauxite, iron salt and stabilizer are added in appropriate amounts, which can achieve 100 days of stability without gelation, thereby achieving waste treatment with waste.

[0017] Furthermore, the acidification flowback fluid includes iron salt and aluminum salt, the mass concentration of the iron salt is 1-100g / L, the mass concentration of the aluminum salt is 0.1-100g / L; the mass content of aluminum oxide in the bauxite is 60-80%. The acidification flowback fluid also contains Mg 2+ , Ca 2+ , K + , Cl - Because of the differences in acidified strata, some also contain heavy metal ions dissolved from stratum rock minerals, as well as residual acidizing fluid additives, such as CuI, CuCl corrosion inhibitors, drainage aids, etc.

[0018] In a second aspect, a method for preparing a compound reverse demulsifier comprises 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 comprises the following preparation steps: using five-membered copolymer polyether demulsifier X-75 as raw material, and obtaining it by quaternary ammonium cation modification. Among them, the five-membered copolymer polyether demulsifier X-75 is specifically disclosed in CN113416576 A.

[0020] Further, the polyether polyquaternary ammonium salt comprises the following specific preparation steps: dissolving the five-membered copolymer polyether demulsifier X-75 with a solvent (e.g., chloroform), adding a phosphorus tribromide solution (e.g., a phosphorus tribromide chloroform solution) dropwise at 5-10° C., wherein the ratio of the five-membered copolymer polyether demulsifier X-75 to phosphorus tribromide is (10-20) g: (0.25-0.75) mol, heating to 55-60° C. after the addition, performing a reflux reaction for 120-150 min, and then cooling After reaching room temperature, an alkaline aqueous solution (such as a sodium hydroxide aqueous solution) is added to separate the layers, and the obtained lower layer solution is distilled under reduced pressure to remove the solvent, or it can be dried with anhydrous sodium sulfate, and then refluxed with dodecyl dimethyl tertiary amine in anhydrous ethanol for 4-6 days, wherein the ratio of the five-membered copolymer polyether demulsifier X-75 to dodecyl dimethyl tertiary amine is (10-20) g: (0.25-0.75) mol, and the solvent is distilled under reduced pressure again to obtain a polyether polyquaternary ammonium salt.

[0021] Wherein, if sodium hydroxide aqueous solution is used for stratification, the sodium hydroxide concentration in the sodium hydroxide aqueous solution can meet the requirements, such as 0.1 mol / L.

[0022] Furthermore, the flocculant includes the following specific preparation steps: taking the filtered acidified flowback liquid, oxidizing the divalent iron ions in the acidified flowback liquid into trivalent iron ions (for example, sodium hypochlorite can be added for oxidation, etc.), then adding bauxite and ferric chloride, stirring and reacting at 60-75° C. for 2-4 hours, controlling the basicity to 20-60% (in terms of aluminum and iron), then filtering while hot, adding a stabilizer (such as sodium phosphate, etc.) to the filtrate, reacting at 60-75° C. for 2-4 hours, cooling to room temperature and maturing to obtain a flocculant (PAFC-01).

[0023] In a second aspect, an application of a compound reverse demulsifier is provided, wherein the compound reverse demulsifier described above is used in the treatment of unconventional natural gas emulsified produced water.

[0024] When the above-mentioned compound reverse demulsifier is used in specific applications, the addition amount of the compound reverse demulsifier is 500 mg / L, the temperature of the produced water is controlled at 25-30°C, and after adding, it is mixed and kept at 25-30°C for more than 30 minutes to achieve demulsification and separation. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0028] Figure 4 This is a diagram of the demulsification effect in Example 4 of the present invention. DETAILED DESCRIPTION

[0029] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased through regular channels.

[0030] Example 1

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

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

[0033] Weigh 15g of five-membered copolymer polyether demulsifier X-75 and dissolve it in 150mL of chloroform. At 5°C, add phosphorus tribromide chloroform solution (0.5mol phosphorus tribromide dissolved in 50mL chloroform) to the above solution. After the addition is complete, gradually increase the reaction temperature to 55-60°C and reflux for 120min. After cooling to room temperature, add 50mL of 20mol / L sodium hydroxide aqueous solution. After standing and stratifying, separate the lower layer solution, dry it with anhydrous sodium sulfate, and evaporate the solvent under reduced pressure to 2kPa. The obtained product is refluxed with 0.5mol of dodecyl dimethyl tertiary amine in 100mL of anhydrous ethanol at 75-80°C for 5 days, and the quaternary ammonium copolymer cationic demulsifier PEPA-12 is obtained after the solvent is evaporated under reduced pressure. According to the principle of chemical reaction, the quaternary ammonium group is connected to the molecular structure of the five-membered polyether, and combined with infrared spectroscopy, the molecular structure deduced is as follows:

[0034] Among them, the value range of a is 30-99, the value range of b is 20-69, the value range of m is 10-90, and the value range of n is 10-90.

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

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

[0037] Take 500ml of the filtered gas field hydrochloric acid acidification return liquid into a three-necked flask and place it on a water bath. Add 14.0ml of sodium hypochlorite under stirring at room temperature to oxidize the divalent iron ions into trivalent iron ions. Then add 294.35g of bauxite containing 60% alumina to the three-necked flask, stir for 30 minutes to dissolve the aluminum in the material in the liquid phase to the maximum extent, add alkali to control the basicity to 53% (in terms of aluminum and iron), stir and react at 60℃ for 3h to make it polymerize with metal ions such as iron. Filter while hot, add 13.51g of phosphate stabilizer to the filtrate, react at 65℃ for 3h, cool to room temperature and mature for 24h, and you will get an inorganic polymer 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 demulsifier:

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

[0040] The mass ratio of PEPA-12 to PAFC-01 is 4:1 to obtain a composite reverse demulsifier (CQ-01). The infrared scanning results are shown in Figure 1 , observed at 3421.8cm -1 The strong and broad absorption peak at 1632.9 cm is attributed to the superposition of OH and NH in PEPA-12 and Fe-OH and Al-OH stretching vibration in PAFC-01. -1 The corresponding deformation vibration appears on the left and right; 1078.4cm -1 is the stretching vibration of CN bond; 983.1cm -1 The superposition of CO stretching vibration and Al-OH bending vibration at 1401.0cm -1 The obvious band at 620cm is the deformation vibration of -CH3 connected to N+ (quaternary ammonium nitrogen); -1 The location is the overall bending vibration of Al-OH.

[0041] The product comparison of PEPA-12 and compound reverse demulsifier (PEPA-12 and PAFC-01 mass ratio is 4:1) is shown in the figure. Figure 2 On the left is PEPA-12, which is a dark brown liquid. After shaking, the liquid surface has bubbles, which is a typical feature of surfactants. On the right is the compound reverse demulsifier (CQ-01, which is a light yellow liquid made by adding flocculant (PAFC-01) to PEPA-12 at a mass ratio of 4:1 and mixing evenly. It can be 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 groups of compound reverse demulsifiers with mass ratios of PEPA-12 to PAFC-01 of 1:4, 2:3, 1:1, 3:2, and 4:1 were set respectively.

[0044] Before the experiment, unconventional natural gas emulsified produced water was taken 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 emulsified produced water was placed in a beaker, and five groups were set up, with each group repeated at least 3 times; first, it was placed in a 30°C constant temperature water bath for preheating for 10 minutes; then, the compound reverse demulsifier was added to each of them at a volume of 500 mg / L, and it was vigorously stirred manually for 100 times. After the beaker with the added agent was placed in a 30°C constant temperature water bath and heated for 30 minutes, the supernatant was taken and its absorbance A was measured by a spectrophotometer and the turbidity was calculated (the equation for the turbidity calculation standard curve is: turbidity = (A-0 .0124)÷0.0034) and turbidity removal rate (turbidity removal rate = (initial turbidity - turbidity of treated water) ÷ initial turbidity × %); take another 25mL supernatant and place it in a separatory funnel, then add 50mL petroleum ether (boiling range 30-60°C) for extraction, repeat twice, use TU-1900 UV-visible spectrophotometer to measure its absorbance A to calculate the oil content (the equation of the oil content standard curve is: C = 4A ÷ 0.0114), and calculate the oil removal rate (oil removal rate = (C0-C) ÷ C0 × %). The specific results are shown in Table 1 below:

[0045] Table 1 Comparison of the demulsification effects of produced water at different ratios of PEPA-12 and PAFC-01

[0046]

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

[0048] The results show that when the ratio of PEPA-12 to PAFC-01 is 4:1, the turbidity removal and oil removal effects are the best. When mixed in other ratios, a large number of flocs are generated, which cannot be effectively settled within 30 minutes, resulting in increased turbidity and negative turbidity removal rates. Since the price of PAFC-01 is only about 30% of that of PEPA-12, and its addition helps to add fast aggregation and sedimentation, it is determined that it is feasible to partially replace PEPA-12 by adding PAFC-01.

[0049] Example 3

[0050] The composite reverse demulsifier in Example 2 with a mass ratio of PEPA-12 to PAFC-01 of 4:1 was used to study the effects of its use temperature and addition amount.

[0051] (1) Effect of temperature

[0052] Four temperature gradients of 15, 20, 25, and 30°C were set for demulsification and flocculation experiments. The raw water quality index and other methods were the same as those in Example 2. To avoid the randomness of the effect, two parallel tests were performed at each temperature. After 30 minutes, the supernatant was taken to measure the turbidity and oil content. The specific results are shown in Table 2. The demulsification state diagram is shown in Figure 3 .

[0053] Table 2 Effect of different temperatures on the effect of reverse demulsifier

[0054]

[0055] The results in Table 2 show that the change in temperature has little effect on the oil removal effect, and the oil content can be achieved at all temperatures <30 mg / L. Temperature mainly affects the reaction between the reagent and the colloid particles and oil droplets in the water, thereby affecting the water treatment effect. Generally, the higher the temperature, the easier the water treatment is, but the higher the temperature, the higher the energy consumption.

[0056] (2) Effect of dosage

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

[0058] Table 3 Effect of different dosages of reverse demulsifier

[0059]

[0060]

[0061] As can be seen from Table 3, when the dosage of the agent is low, the turbidity does not decrease but increases, indicating that a large number of tiny flocs are formed at this time, but it is difficult to aggregate and settle due to the low concentration. As the dosage of the composite agent increases, the removal rate of turbidity and oil content in water increases. When the dosage is 500 mg / L, the demulsification effect is the best and can meet the assessment indicators. Continuing to increase the dosage of the agent, the demulsification effect remains basically unchanged.

[0062] Example 4

[0063] In order to verify the treatment effect, the experimental scale was appropriately enlarged, and the experimental wastewater volume was increased from 100ml to 200ml and 500ml respectively. 200mL of produced water from the third gas production plant of PetroChina Gas Field was placed in a beaker, first preheated in a 30℃ constant temperature water bath for 10min; then 500mg / L of reverse demulsifier (PEPA-12:PAFC-01 mass ratio of 4:1) was added, and it was vigorously stirred manually for 100 times. The beaker after adding the agent was placed in a 30℃ constant temperature water bath for 10min. After heating in a constant temperature water bath at 30°C for 30 minutes, take the supernatant and use a spectrophotometer to determine its absorbance A and calculate the turbidity; take another 25 mL of supernatant and place it in a separatory funnel, then add 50 mL of petroleum ether (boiling range 30-60°C) for extraction, repeat twice, and use a TU-1900 UV-visible spectrophotometer to determine its oil content and calculate the oil removal rate; determine the suspended matter in produced water according to "GB / T11901-1989 Gravimetric method for determination of suspended matter in water quality"; determine the chromaticity of produced water according to "HJ 1182-2021 Dilution multiple method for determination of chromaticity of water quality". See Table 4 for specific data. See the specific demulsification effect. Figure 4 :

[0064] Table 4 Detection results of the expanded experiment

[0065]

[0066] The experimental results in Table 4 show that the compound reverse demulsifier prepared by the method for preparing the compound reverse demulsifier of the present invention can still efficiently and quickly neutralize the negative charge of oil droplets and suspended matter in water in the amplified experiment, and has high efficiency in removing turbidity and suspended matter. After treatment, the suspended matter is 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)), which is the recommended water quality index 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 taken, and its original oil content and turbidity were measured to be 69.123 mg / L (absorbance A) and 158 NTU (absorbance A = 0.197). Then, X-75, PEPA-12, PAFC-01, commercially available polyaluminium chloride ferric (PAFC), commercially available PAC (polyaluminium chloride) and the composite reverse demulsifier of the present invention (PEPA-12, PAFC-01 mass ratio of 4:1) were used to treat the produced water, and the amount added to the produced water was 500 mg / L, and the emulsion was broken at room temperature of 25°C, and the sample was tested after standing for 30 minutes after stirring. The specific results are shown in Table 5 below:

[0069] Table 5 Results of control experiment

[0070]

[0071]

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

[0073] It can be seen from Table 5 that the flocculation effect is better when PAC is used alone. The inventors further studied the effect of compounding it with PEPA-12. PEPA-12, PAC and PEPA-12, PAC were compounded at 1:4, 3:7, 2:3, 1:1, 3:2, 7:3, 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 compounding

[0075]

[0076] As shown in Table 6, the combination of PEPA-12 and PAC significantly affects the sedimentation efficiency and demulsification and oil removal effect, which is worse than the effect of using a single agent. The combination of PEPA-12 and PAFC-01 has a synergistic effect.

[0077] In summary, the composite reverse demulsifier provided by the present invention promotes the flocculation and coalescence of oil droplets by neutralizing the negative charge on the surface of oil droplets in the O / W emulsion; wherein the demulsifier polyether polyquaternary ammonium salt (PEPA-12) is a hydrophilic cationic reverse demulsifier, which mainly solves the problem of produced water emulsification, has a large molecular weight, a large number of branched structures, a large oil-water interface area and a high interfacial activity, is easy to adsorb and replace a variety of emulsifiers on the oil-water interface, reduces the stability of the interfacial film, and has good environmental adaptability. Strong, good 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 small oil droplets easily aggregate into large oil droplets; the flocculant (PAFC-01) mainly solves the flocculation, agglomeration and floc sedimentation problems of droplets after demulsification; the polyether polyquaternary ammonium salt PEPA-12 and the flocculant (PAFC-01) are compounded to play the synergistic effect of "displacement, electrical neutralization, compression of double electric layer and flocculation aggregation", making the O / W emulsified produced water easy to destabilize, flocculate and separate.

[0078] The composite reverse demulsifier provided by the present invention has stable properties at room temperature, can be stored for a long time, has low cost, good water solubility, is easy to use, and can quickly demulsify gas field produced water under low temperature and low dosage conditions; when the composite ratio is 4:1 and the dosage is 500 mg / L, the oil content of the treated water is less than 30 mg / L and SS is less than or equal to 15 mg / L.

[0079] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A composite reverse demulsifier, characterized in that: The compound reverse demulsifier comprises polyether polyquaternary ammonium salt and flocculant, and the mass ratio of the polyether polyquaternary ammonium salt to the flocculant is (7-8): (2-3).

2. A composite inverse 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 composite inverse demulsifier according to claim 1 or 2, characterized in that: The molecular structure of the polyether polyquaternary ammonium salt is shown in formula (1): The value range of a is 30-99, the value range of b is 20-69, the value range of m is 10-90, and the value range of n is 10-90.

4. A composite inverse demulsifier according to claim 1 or 2, characterized in that: The flocculant is mainly made of acidified flowback liquid, bauxite and ferric chloride, and the mass ratio of the acidified flowback liquid, the bauxite and the ferric chloride is 10:(1.25-2.0):(0-0.2).

5. A composite inverse demulsifier according to claim 4, characterized in that: The acidified flowback fluid comprises iron salt and aluminum salt, wherein the mass concentration of the iron salt is 1-100 g / L and the mass concentration of the aluminum salt is 0.1-100 g / L; and the mass content of aluminum oxide in the bauxite is 60-80%.

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

7. The method for preparing a composite reverse demulsifier according to claim 6, characterized in that: The polyether multi-quaternary ammonium salt comprises the following preparation steps: using five-membered copolymer polyether demulsifier X-75 as raw material and obtaining it through quaternary ammonium cation modification.

8. The method for preparing a composite reverse demulsifier according to claim 7, characterized in that: The polyether polyquaternary ammonium salt comprises the following specific preparation steps: dissolving the five-membered copolymer polyether demulsifier X-75 with a solvent, dripping a phosphorus tribromide solution at 5-10° C., wherein the ratio of the five-membered copolymer polyether demulsifier X-75 to the phosphorus tribromide is (10-20) g: (0.25-0.75) mol, heating to 55-60° C. after dripping, performing a reflux reaction for 120-150 min, cooling to room temperature, adding an alkaline aqueous solution for layering, removing the solvent from the obtained lower layer solution by reduced pressure distillation, and then performing a reflux reaction with dodecyl dimethyl tertiary amine in anhydrous ethanol for 4-6 days, wherein the ratio of the five-membered copolymer polyether demulsifier X-75 to the dodecyl dimethyl tertiary amine is (10-20) g: (0.25-0.75) mol, and removing the solvent by reduced pressure distillation again to obtain the polyether polyquaternary ammonium salt.

9. The method for preparing a composite reverse demulsifier according to claim 6, characterized in that: The flocculant comprises the following specific preparation steps: taking filtered acidified flowback liquid, oxidizing the divalent iron ions in the acidified flowback liquid into trivalent iron ions, then adding bauxite and ferric chloride, stirring and reacting at 60-75°C for 2-4 hours, controlling the basicity to 20-60%, then filtering while hot, adding a stabilizer to the filtrate, reacting at 60-75°C for 2-4 hours, cooling to room temperature and maturing to obtain the flocculant.

10. An application of a compound reverse demulsifier, characterized in that: The composite reverse demulsifier described in any one of claims 1 to 5 is used in the treatment of unconventional natural gas emulsified produced water.

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