Flocculating agent for oilfield produced water and preparation method thereof

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an oilfield produced water flocculant and a preparation method thereof. The preparation method comprises the following steps: in a nitrogen environment, in the presence of a buffer salt and under the action of an initiator and a reducing agent, 4-vinylpyridine, allyltriphenylphosphonium chloride and acryloyloxyethyl dimethyl benzyl ammonium chloride are subjected to a polymerization reaction. The flocculant has the advantages of wide raw material source, simple synthesis process, good flocculation effect, oil removal and sterilization, and when the use concentration is 5mg / L, the oil removal rate and the suspended solid removal rate respectively reach 90% and 80% or above, and the sterilization rate reaches 99% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to an oilfield produced water flocculant and a preparation method thereof. Background Art

[0002] As oilfield development enters the middle and late stages, the formation energy gradually decreases, and primary oil recovery technology can no longer meet production needs. Currently, oil recovery technologies mainly focus on secondary and tertiary oil recovery. Both secondary and tertiary oil recovery require the injection of a large amount of water into the formation to replenish the formation energy deficit and maintain a certain pressure in the oil layer. This water is usually produced water that is recycled and reused.

[0003] Recycled injection water usually contains more suspended matter, with more complex components and more and more difficult to handle. If these suspended matter are directly injected into the formation without treatment, it will cause the blockage of the injection well, reduce the pore permeability of the oil layer, hinder the water injection oil production, increase the water injection pressure, and damage the formation, seriously affecting the recovery rate and directly affecting the crude oil production.

[0004] Recycled reinjection water usually contains more crude oil, and its impact on reinjection is similar to that of suspended solids.

[0005] Recycled reinjection water can easily breed various bacteria, mainly including sulfate-reducing bacteria, saprophytes and iron bacteria. The growth, metabolism and reproduction of these bacteria can cause corrosion and damage to drilling equipment, water injection pipelines and other metal materials, blockage of pipelines and water injection wells, reduce the pore permeability of the oil layer, hinder water injection and oil production, directly affect crude oil production, and cause huge economic losses to oil field production and operation.

[0006] SYT 5329-2012 "Water Quality Indicators and Analysis Methods for Water Injection in Clastic Reservoirs" has strict regulations on the quality of water for injection. Sulfate-reducing bacteria, saprophytic bacteria, iron bacteria, suspended matter, and oil content are the main control indicators.

[0007] CN 107879447 A "A preparation method for a flocculant for treating oily sewage" discloses a preparation method for a flocculant for treating oily sewage, which mainly uses chitosan as the main raw material, and adds polyferric sulfate, polyaluminum sulfate, polydimethyldiallylammonium chloride and diphenylthiourea copper complex for modification during the preparation process. The flocculant contains an inorganic flocculant. Inorganic flocculants have the disadvantages of large usage, large mud production, easy corrosion of equipment, secondary pollution (such as iron salts easily increase the color of water quality, aluminum salts easily cause aluminum ions in water to exceed the standard), and will have adverse effects on humans and other organisms when entering the ecological environment, and the use process is relatively cumbersome and difficult to promote.

[0008] CN103224588A discloses a flocculant, which is prepared by free radical polymerization of acrylamide, acrylic acid, sodium carbonate, and sodium salt of maleic acid monohexadecyl ester in an aqueous phase; based on the total mass of water, acrylamide, acrylic acid, sodium carbonate, sodium salt of maleic acid monohexadecyl ester and initiator as 100: 10-20% acrylamide; 10-15% sodium carbonate; 7-8% acrylic acid; 1-3% sodium salt of maleic acid monohexadecyl ester; 0.01-0.1% initiator, the initiator is composed of sodium bisulfite and potassium persulfate in a mass ratio of 1:1; the balance is water. The invention also discloses a preparation method of the above flocculant. The invention has obvious flocculation effect and is easy to configure. However, the dosage is 2g / L, and the SS removal rate is only 80%, which is not ideal.

[0009] CN107593703B discloses a bactericide for oilfield water treatment system and its preparation method and application. The bactericide comprises 5wt.% to 60wt.% of dodecyl dimethyl benzyl ammonium halide, 0.5wt.% to 5wt.% of D-amino acid, 10wt.% to 30wt.% of surfactant, 3wt.% to 10wt.% of buffer and the balance of water. The bactericide of the present invention has high bactericidal efficiency, has high bactericidal effect on sulfate reducing bacteria (SRB) and saprophytic bacteria (TGB), has long duration of efficacy, simple production process and low cost. The main active ingredient of the invention is dodecyl dimethyl benzyl ammonium chloride, which is the common 1227. Since the agent has been used in oil fields for a long time, many bacteria have developed resistance to it and the bactericidal effect is getting worse and worse. Summary of the invention

[0010] In view of the deficiencies of the current existing technology, the present invention provides an oilfield produced water flocculant and a preparation method thereof. The flocculant has a wide source of raw materials, a simple synthesis process, and a good flocculation effect. It also has the advantages of oil removal and sterilization. When the use concentration is 5 mg / L, the oil removal rate and suspended solid removal rate reach 90% and 80% or more respectively, and the sterilization rate reaches more than 99%.

[0011] Therefore, in order to achieve the above-mentioned purpose, on the one hand, the present invention provides an oilfield produced water flocculant, the molecular formula of the flocculant is as follows:

[0012]

[0013] Where: x = 20000-200000;

[0014] y = 5000-100000;

[0015] z=5000-100000.

[0016] The viscosity average molecular weight of the flocculant is 10,000,000-20,000,000.

[0017] On the other hand, the present invention provides a method for preparing an oilfield produced water flocculant, the preparation method comprising: in a nitrogen environment, in the presence of a buffer salt, under the action of an initiator and a reducing agent, 4-vinylpyridine, allyltriphenylphosphonium chloride, and acryloyloxyethyldimethylbenzyl ammonium chloride undergo a polymerization reaction.

[0018] The third object of the present invention is to disclose the application of the above flocculant in the treatment of oilfield produced water.

[0019] The oilfield produced water flocculant provided by the present invention is a polymer product formed by the polymerization of three functional units, and the functional monomers are 4-vinylpyridine, allyltriphenylphosphonium chloride, and acryloyloxyethyl dimethylbenzyl ammonium chloride. The suspended matter in the sewage is usually colloidal particles, which usually carry a negative charge. Since the surface charge signs of the particles are the same, electrostatic repulsion is generated between the particles, so that the colloidal particles cannot form aggregations and are suspended in the water, resulting in an increase in the turbidity of the water body. The molecules of the present invention contain cationic groups such as quaternary ammonium, quaternary phosphonium, and pyridine, and have a positive charge on the surface, which generates electrostatic attraction with the suspended matter, and the electrostatic repulsion disappears, thereby destabilizing the colloidal particles and forming larger flocs to sink, thereby achieving the purpose of solid-liquid separation. The flocculant provided by the present invention is a high molecular polymer with a large molecular weight and a long molecular chain, and can adsorb multiple colloidal particles to the active molecular chains. The quaternary phosphonium and quaternary ammonium functional groups in the present invention play a bridging role. These macromolecules that have adsorbed multiple particles will be entangled with each other to produce larger-sized flocs. In the process of slow sinking, some fine particles remaining in the solution are rolled up inside the flocs, which plays a net-catching role and sinks with fine particles together, thereby achieving a better flocculation effect. The quaternary phosphonium and quaternary ammonium functional groups in the present invention are close to the benzene ring, and the benzene ring has a strong electron-withdrawing effect, which leads to the strengthening of the positive charge of the quaternary phosphonium and quaternary ammonium functional groups. The bacterial surface is negatively charged, and it is easier to adsorb on the positively charged molecules, thereby changing the permeability of the cell wall, causing the components in the bacterial cell to leak out and die. The quaternary phosphonium cation can form hydrogen bonds with the bases of deoxyribonucleic acid (DNA) in the protein in the bacterial body, adsorb on the bacterial cell, destroy the DNA structure of the bacteria, and make it lose its replication ability and die. Pyridine belongs to a bactericidal group and can also strengthen the bactericidal effect of the present invention.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) The present invention has a one-pot synthesis process, all products are effective ingredients, the yield is 100%, and no by-products are produced;

[0022] (2) The oilfield produced water flocculant of the present invention has good oil removal rate and suspended solid removal rate. When the concentration is 5 mg / L, the oil removal rate and suspended solid removal rate reach 90% and 80% or more respectively;

[0023] (3) The oilfield produced water flocculant of the present invention also has good bactericidal function. When the concentration is 5 mg / L, the bactericidal rate reaches more than 99%. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] According to a first aspect of the present invention, the present invention provides an oilfield produced water flocculant, the molecular formula of the flocculant is as follows:

[0026]

[0027] Among them, x=20000-200000, preferably x=50000-200000; y=5000-100000, preferably y=25000-100000; z=5000-100000, preferably z=12000-50000.

[0028] The viscosity average molecular weight of the flocculant is 10,000,000-20,000,000, preferably 15,000,000-20,000,000.

[0029] In a second aspect, the present invention provides a method for preparing an oilfield produced water flocculant, the preparation method comprising: in a nitrogen environment, in the presence of a buffer salt, under the action of an initiator and a reducing agent, 4-vinylpyridine, allyltriphenylphosphonium chloride, and acryloyloxyethyl dimethylbenzyl ammonium chloride undergo a polymerization reaction.

[0030] In the present invention, preferably, the molar ratio of allyltriphenylphosphonium chloride, acryloyloxyethyldimethylbenzyl ammonium chloride and 4-vinylpyridine is 0.2-0.6:0.2-0.6:1.

[0031] More preferably, the molar ratio of allyltriphenylphosphonium chloride, acryloyloxyethyldimethylbenzyl ammonium chloride and 4-vinylpyridine is 0.3-0.5:0.3-0.5:1.

[0032] More preferably, the molar ratio of allyltriphenylphosphonium chloride, acryloyloxyethyldimethylbenzyl ammonium chloride and 4-vinylpyridine is 0.3-0.4:0.3-0.4:1.

[0033] In the present invention, preferably, the initiator is one of sodium persulfate, potassium persulfate and ammonium persulfate.

[0034] In the present invention, preferably, the weight ratio of the initiator to 4-vinylpyridine is 0.01-0.05:1.

[0035] In the present invention, preferably, the reducing agent is one of sodium sulfite, sodium bisulfite, sodium thiosulfate and ferrous sulfate.

[0036] More preferably, the reducing agent is sodium sulfite or sodium bisulfite.

[0037] In the present invention, preferably, the weight ratio of the reducing agent to 4-vinylpyridine is 0.004-0.02:1.

[0038] In the present invention, preferably, the buffer salt is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate.

[0039] More preferably, the buffer salt is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate.

[0040] In the present invention, preferably, the weight ratio of the buffer salt to 4-vinylpyridine is 0.03-0.05:1.

[0041] In the present invention, preferably, the polymerization reaction temperature is room temperature-75°C.

[0042] More preferably, the polymerization reaction comprises two stages carried out sequentially, the reaction temperature of the first stage is room temperature; the reaction temperature of the second stage is 70-75° C. and the reaction time is 20-30 min.

[0043] According to a more specific preferred embodiment, the preparation method of the oilfield produced water flocculant has the following specific steps:

[0044] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 4-vinylpyridine, allyltriphenylphosphonium chloride, acryloyloxyethyldimethylbenzyl ammonium chloride, buffer salt, and deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with sodium hydroxide solution;

[0045] (2) adding an initiator aqueous solution to the first high-position dropping tank, adding a reducing agent aqueous solution to the second high-position dropping tank, and simultaneously adding the two to the reactor, controlling the dropping time of the first high-position dropping tank to be 20-30 minutes, and the second high-position dropping tank lags behind the first high-position dropping tank by 10-15 minutes to complete the dropping, and the reaction system automatically heats up. When the temperature no longer changes, continue to heat up to 70-75° C., keep the temperature for reaction for 20-30 minutes, adjust the pH to 7-8 with a sodium hydroxide solution, and cool down to below 40° C. to obtain a viscous liquid;

[0046] (3) drying and granulating the viscous liquid to obtain particles of 0.5-2 mm, thereby obtaining a flocculant product.

[0047] Preferably, the weight ratio of deionized water to 4-vinylpyridine in step (1) is 6-10:1.

[0048] The reaction equation for the synthesis of the oilfield produced water flocculant of the present invention is as follows:

[0049]

[0050] The third object of the present invention is to disclose the application of the above flocculant in the treatment of oilfield produced water. There is no special requirement for the specific application, and it can be a conventional application in the field, which will not be discussed in detail here.

[0051] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0052] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0055] In the following examples and comparative examples, unless otherwise specified, all reagents used were commercially available chemically pure reagents.

[0056] Example 1

[0057] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.2 mol of allyltriphenylphosphonium chloride, 0.4 mol of acryloyloxyethyldimethylbenzylammonium chloride, 3.15 g of sodium dihydrogen phosphate, and 630 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0058] (2) adding an initiator aqueous solution into the first high-position dropping tank, wherein the initiator aqueous solution is 1.05 g of sodium persulfate dissolved in 20 g of water, and adding a reducing agent aqueous solution into the second high-position dropping tank, wherein the reducing agent aqueous solution is 0.42 g of sodium sulfite dissolved in 10 g of water. The two are simultaneously added dropwise to the reaction kettle, and the addition time of the first high-position dropping tank is controlled to be 20 min. The second high-position dropping tank is 10 min later than the first high-position dropping tank in addition. The reaction system automatically heats up. When the temperature no longer changes, the temperature is continued to rise to 70° C., and the reaction is kept warm for 23 min. The pH is adjusted to 7-8 with a 1 mol / L sodium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid;

[0059] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 1 .

[0060] Example 2

[0061] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.25 mol of allyltriphenylphosphonium chloride, 0.35 mol of acryloyloxyethyldimethylbenzylammonium chloride, 3.44 g of sodium dihydrogen phosphate, and 780 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0062] (2) adding an initiator aqueous solution into the first high-position dropping tank, wherein the initiator aqueous solution is 1.45 g of sodium persulfate dissolved in 20 g of water, and adding a reducing agent aqueous solution into the second high-position dropping tank, wherein the reducing agent aqueous solution is 0.63 g of sodium sulfite dissolved in 10 g of water. The two are simultaneously added dropwise to the reaction kettle, and the addition time of the first high-position dropping tank is controlled to be 30 min. The second high-position dropping tank is 15 min later than the first high-position dropping tank in the addition. The reaction system automatically heats up. When the temperature no longer changes, the temperature is continued to rise to 75° C., and the reaction is kept warm for 27 min. The pH is adjusted to 7-8 with a 1 mol / L sodium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid;

[0063] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 2 .

[0064] Example 3

[0065] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.3 mol of allyltriphenylphosphonium chloride, 0.6 mol of acryloyloxyethyldimethylbenzylammonium chloride, 3.86 g of potassium dihydrogen phosphate, and 960 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0066] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 2.13 g of sodium persulfate dissolved in 20 g of water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 1.02 g of sodium sulfite dissolved in 10 g of water, and simultaneously adding the two into the reactor, the dropping time of the first high-position dropping tank being controlled to be 30 min, the second high-position dropping tank being 12 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, and when the temperature no longer changes, continuing to heating up to 75° C., keeping the temperature for reaction for 28 min, adjusting the pH to 7-8 with a 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0067] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 3 .

[0068] Example 4

[0069] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.35 mol of allyltriphenylphosphonium chloride, 0.55 mol of acryloyloxyethyldimethylbenzylammonium chloride, 4.15 g of potassium dihydrogen phosphate, and 940 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0070] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 2.87 g potassium persulfate dissolved in 20 g water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 1.38 g sodium bisulfite dissolved in 10 g water, and simultaneously adding the two into the reaction kettle, the dropping time of the first high-position dropping tank being controlled to be 20 min, the second high-position dropping tank being 10 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, when the temperature no longer changes, continuing to heating up to 70° C., keeping the temperature for reaction for 22 min, adjusting the pH to 7-8 with 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0071] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 4 .

[0072] Example 5

[0073] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.4 mol of allyltriphenylphosphonium chloride, 0.4 mol of acryloyloxyethyldimethylbenzylammonium chloride, 4.44 g of ammonium dihydrogen phosphate, and 1000 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0074] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 3.15 g of sodium persulfate dissolved in 20 g of water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 1.25 g of sodium bisulfite dissolved in 10 g of water, and simultaneously adding the two to the reactor, the dropping time of the first high-position dropping tank being controlled to be 25 min, the second high-position dropping tank being 15 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, when the temperature no longer changes, continuing to heating up to 72° C., keeping the temperature for reaction for 26 min, adjusting the pH to 7-8 with a 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0075] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 5 .

[0076] Example 6

[0077] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.45 mol of allyltriphenylphosphonium chloride, 0.3 mol of acryloyloxyethyldimethylbenzylammonium chloride, 4.83 g of disodium hydrogen phosphate, and 900 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0078] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 4.03 g potassium persulfate dissolved in 20 g water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 1.56 g sodium thiosulfate dissolved in 10 g water, and simultaneously adding the two into the reactor, the dropping time of the first high-position dropping tank being controlled to be 22 min, the second high-position dropping tank being 13 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, when the temperature no longer changes, continuing to heating up to 73° C., keeping the temperature for reaction for 22 min, adjusting the pH to 7-8 with a 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0079] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 6 .

[0080] Example 7

[0081] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.5 mol of allyltriphenylphosphonium chloride, 0.25 mol of acryloyloxyethyldimethylbenzylammonium chloride, 4.55 g of dipotassium hydrogen phosphate, and 880 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0082] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 4.84 g of ammonium persulfate dissolved in 30 g of water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 1.98 g of sodium thiosulfate dissolved in 20 g of water, and simultaneously adding the two to the reactor, the dropping time of the first high-position dropping tank being controlled to be 27 min, the second high-position dropping tank being 14 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, when the temperature no longer changes, continuing to heating up to 72° C., keeping the temperature for reaction for 25 min, adjusting the pH to 7-8 with a 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0083] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 7 .

[0084] Example 8

[0085] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.55 mol of allyltriphenylphosphonium chloride, 0.2 mol of acryloyloxyethyldimethylbenzylammonium chloride, 4.34 g of sodium dihydrogen phosphate, and 910 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0086] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 4.32 g of ammonium persulfate dissolved in 30 g of water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 1.84 g of ferrous sulfate dissolved in 20 g of water, and simultaneously adding the two to the reactor, the dropping time of the first high-position dropping tank being controlled to be 23 min, the second high-position dropping tank being 12 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, and when the temperature no longer changes, continuing to heating up to 71° C., keeping the temperature for reaction for 20 min, adjusting the pH to 7-8 with a 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0087] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 8 .

[0088] Example 9

[0089] (1) purging the reactor with nitrogen to maintain the nitrogen atmosphere in the reactor, adding 1 mol of 4-vinylpyridine, 0.6 mol of allyltriphenylphosphonium chloride, 0.4 mol of acryloyloxyethyldimethylbenzylammonium chloride, 5.25 g of diammonium hydrogen phosphate, and 1050 g of deionized water into the reactor in sequence, stirring evenly, and adjusting the pH to 7-9 with 1 mol / L sodium hydroxide solution;

[0090] (2) adding an initiator aqueous solution into the first high-position dropping tank, the initiator aqueous solution being 5.25 g of ammonium persulfate dissolved in 30 g of water, adding a reducing agent aqueous solution into the second high-position dropping tank, the reducing agent aqueous solution being 2.1 g of ferrous sulfate dissolved in 20 g of water, and simultaneously adding the two to the reactor, the dropping time of the first high-position dropping tank being controlled to be 28 min, the second high-position dropping tank being 14 min later than the first high-position dropping tank in the dropping completion, the reaction system automatically heating up, and when the temperature no longer changes, continuing to heating up to 74° C., keeping the temperature for reaction for 30 min, adjusting the pH to 7-8 with a 1 mol / L sodium hydroxide solution, cooling down to below 40° C., and obtaining a viscous liquid;

[0091] (3) Drying and granulating the above viscous liquid to obtain particles of 0.5-2 mm to obtain the product flocculant N 9 .

[0092] Example 10 Evaluation of flocculation effect

[0093] The oil content of water delivered from a joint station of Shengli Oilfield is 75mg / L and the suspended solids is 46mg / L. 1 -N 9 A flocculation experiment was conducted with a dosage of 5 mg / L. The oil removal rate was tested using the method in 5.4 of QSH 1020 1356-2016 "General Technical Requirements for Flocculants for Conventional Produced Water Treatment in Oilfields", and the suspended solids removal rate was tested using the method in 5.5.

[0094] Polydimethyldiallylammonium chloride (PDMDAAC) of the same concentration was used as a comparative sample, and the test results are shown in Table 1.

[0095] Table 1 Flocculation test results

[0096]

[0097]

[0098] From Table 1 we can see that:

[0099] (1) Flocculant N of the present invention 1 -N 9When the concentration is 5mg / L, the oil removal rate reaches more than 90%, and the highest reaches 95% (N 8 、N 9 ), while the oil removal rate of the comparative example polydimethyldiallyl ammonium chloride (PDMDAAC) is 72%, which is significantly lower than that of the present invention;

[0100] (2) Flocculant N of the present invention 1 -N 9 When the concentration is 5mg / L, the suspended solid removal rate reaches more than 80%, and the highest reaches 88% (N 9 ), while the suspended solid removal efficiency of the comparative example polydimethyldiallylammonium chloride (PDMDAAC) is 56%, which is significantly lower than that of the present invention.

[0101] Example 11 Evaluation of Sterilization Rate

[0102] Take the water from a certain joint station and put it into a series of 250ml narrow-mouth bottles, add 5mg / L of the flocculant N of the present invention 1 -N 9 , placed in a 60℃ oven, sampled after 4h, and the number of SRB, TGB, and FB was detected by the extinction dilution method, and the bactericidal rate was calculated.

[0103] Dodecyl dimethyl benzyl ammonium chloride (1227) of the same concentration was used as a comparative sample. The test results are shown in Table 2.

[0104] Table 2 Sterilization test results (sterilization rate, %)

[0105]

[0106]

[0107] From Table 2 we can see that:

[0108] The flocculant N of the present invention 1 -N 9 When the concentration used is 5 mg / L, the bactericidal rates of SRB, TGB and FB all reach over 99%, with the highest reaching 100%; while the bactericidal rates of the comparative example dodecyl dimethyl benzyl ammonium chloride (1227) on SRB, TGB and FB are 66.7%, 75.6% and 91.1%, respectively, which are significantly lower than those of the present invention.

[0109] Example 12 Field Application

[0110] A field test was carried out at a water injection station in Gudao Oil Production Plant, with a treatment scale of 80m 3 / d, the SRB (sulfate reducing bacteria) content in the water is 45 / ml, the TGB (saprophytic bacteria) content is 45 / ml, the FB (iron bacteria) content is 11 / ml, the oil content is 132mg / L, and the suspended matter content is 105mg / L. 9 Treat oily wastewater from the joint station, N 9 The dosage is 0.48kg / d, and the dosage concentration is 5mg / L. After treatment, the SRB, TGB, and FB contents are all 0, and the sterilization rate is 100%; the oil content is 3.6mg / L, and the oil removal rate is 97.3%; the suspended matter content is 8.5mg / L, and the flocculation rate is 91.9%. The field test effect is good and meets the field test requirements.

[0111] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing an oilfield produced water flocculant, characterized in that: The preparation method comprises the following steps: in a nitrogen environment, in the presence of a buffer salt, under the action of an initiator and a reducing agent, 4-vinyl pyridine, allyl triphenyl phosphonium chloride and acryloyloxyethyl dimethyl benzyl ammonium chloride undergo a polymerization reaction.

2. The method for preparing an oilfield produced water flocculant according to claim 1, characterized in that: The molar ratio of allyltriphenylphosphonium chloride, acryloyloxyethyl dimethylbenzyl ammonium chloride and 4-vinylpyridine is 0.2-0.6:0.2-0.6:

1.

3. The method for preparing an oilfield produced water flocculant as claimed in claim 2, characterized in that: The molar ratio of allyltriphenylphosphonium chloride, acryloyloxyethyl dimethylbenzyl ammonium chloride and 4-vinylpyridine is 0.3-0.5:0.3-0.5:

1.

4. The method for preparing an oilfield produced water flocculant as claimed in claim 3, characterized in that: The molar ratio of allyltriphenylphosphonium chloride, acryloyloxyethyl dimethylbenzyl ammonium chloride and 4-vinylpyridine is 0.3-0.4:0.3-0.4:

1.

5. The method for preparing an oilfield produced water flocculant according to claim 1, characterized in that: The initiator is one of sodium persulfate, potassium persulfate and ammonium persulfate.

6. The method for preparing an oilfield produced water flocculant as claimed in claim 1 or 5, characterized in that: The weight ratio of the initiator to 4-vinylpyridine is 0.01-0.05:

1.

7. The method for preparing an oilfield produced water flocculant as claimed in claim 1, characterized in that: The reducing agent is one of sodium sulfite, sodium bisulfite, sodium thiosulfate and ferrous sulfate.

8. The method for preparing an oilfield produced water flocculant as claimed in claim 7, characterized in that: The reducing agent is sodium sulfite or sodium bisulfite.

9. The method for preparing an oilfield produced water flocculant as claimed in claim 1 or 7, characterized in that: The weight ratio of the reducing agent to 4-vinylpyridine is 0.004-0.02:

1.

10. The method for preparing an oilfield produced water flocculant according to claim 1, characterized in that: The buffer salt is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate.

11. The method for preparing an oilfield produced water flocculant according to claim 10, characterized in that: The buffer salt is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate and ammonium dihydrogen phosphate.

12. The method for preparing an oilfield produced water flocculant as claimed in claim 1 or 10, characterized in that: The weight ratio of the buffer salt to 4-vinylpyridine is 0.03-0.05:

1.

13. The method for preparing an oilfield produced water flocculant according to claim 1, characterized in that: The polymerization reaction temperature is room temperature-75°C.

14. The method for preparing an oilfield produced water flocculant as claimed in claim 13, characterized in that: The polymerization reaction includes two stages carried out sequentially. The reaction temperature of the first stage is room temperature; the reaction temperature of the second stage is 70-75° C. and the reaction time is 20-30 minutes.

15. An oilfield produced water flocculant, characterized in that: The molecular formula of the flocculant is as follows: Where: x = 20000-200000; y＝5000-100000； z＝5000-100000。 16. The oilfield produced water flocculant according to claim 15, characterized in that: The molecular formula of the flocculant is as follows: Where: x = 50000-200000; y＝25000-100000； z＝12000-50000。 17. The oilfield produced water flocculant according to claim 15, characterized in that: The viscosity average molecular weight of the flocculant is 10,000,000-20,000,000.

18. The oilfield produced water flocculant according to claim 17, characterized in that: The viscosity average molecular weight of the flocculant is 15,000,000-20,000,000.

19. Use of the oilfield produced water flocculant as claimed in any one of claims 15 to 18 in the treatment of oilfield produced water.

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