A bactericide for oilfield water injection treatment and a preparation method thereof

Abstract

The application belongs to the technical field of oilfield water treatment, and particularly relates to a bactericide for oilfield water injection treatment and a preparation method thereof. 60 Coγ rays to obtain low-molecular-weight chitosan; S2, preparation of a quaternary ammonium salt etherification agent: drop a certain amount of epichlorohydrin into N,N-dimethyl long-chain alkyl tertiary amine, and constant-temperature reaction to obtain the quaternary ammonium salt etherification agent; S3, preparation of the bactericide: add acetic acid solution to the low-molecular-weight chitosan obtained in S1, stir uniformly to obtain a chitosan solution, then add the quaternary ammonium salt etherification agent obtained in S2, and constant-temperature reaction to obtain the low-molecular-weight chitosan quaternary ammonium salt bactericide. 60 The application degrades chitosan by Coγ rays, loads quaternary ammonium salt groups with long-chain alkyl groups having antibacterial properties to obtain an environmentally-friendly bactericide, and the bactericide has the advantages of small dosage, high bactericidal efficiency and environmental friendliness, and can meet the needs of oilfield production.

Description

Technical Field

[0001] This invention belongs to the field of oilfield water treatment technology, specifically relating to a bactericide for oilfield water injection treatment and its preparation method. Background Technology

[0002] As oil content in oilfields decreases, most oilfields in my country have entered the water-driven recovery stage of tertiary oil recovery. The water content of the produced fluids is increasing year by year. These high-water-content produced fluids require oil-water separation. The resulting wastewater is treated before being reinjected into the formation to maintain sufficient formation pressure. Due to the high water content of the produced fluids, the oilfield water injection system contains a large number of bacteria and microorganisms that are detrimental to water-driven oil recovery, such as sulfate-reducing bacteria, saprophytic bacteria, and iron bacteria. Research and analysis indicate that sulfate-reducing bacteria are one of the main factors contributing to microbial corrosion, and sulfate-reducing bacteria corrosion alone can cause significant economic losses to oilfield production and operation. Therefore, it is generally necessary to pretreat the wastewater with bactericides before reinjection to effectively control the number of microbial communities.

[0003] Currently, the most widely used bactericides in oilfields are surfactants, especially quaternary ammonium salt bactericides. Besides their bactericidal effect, these also reduce the surface tension of water and remove sludge. In addition, quaternary phosphate salt bactericides and bimolecular membrane surfactant-type bactericides have also been developed. However, prolonged use of the same bactericide leads to severe bacterial resistance, gradually weakening the bactericidal effect and requiring increasingly higher dosages, which no longer meets the needs of oilfield production. Furthermore, the chemical additives used in oilfield wastewater treatment in my country pollute the environment, increasing wastewater treatment costs. Therefore, there is an urgent need to develop green and efficient bactericides with good bactericidal properties and low environmental pollution. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a bactericide for oilfield water injection treatment and its preparation method. This invention solves the problems of existing oilfield bactericides, such as large dosage, difficulty in degradation, and poor bactericidal effect. It has the advantages of low cost, small dosage, high bactericidal efficiency, environmental friendliness, and wide range of applications, and can meet the production needs of oilfields and effectively protect oilfield system pipelines and equipment.

[0005] One objective of this invention is to provide a method for preparing a bactericide for oilfield water injection treatment, comprising the following steps:

[0006] S1. Preparation of low molecular weight chitosan: The chitosan sample was placed in a container, nitrogen gas was introduced to remove oxygen, and the container was sealed. The mixture was then incubated at room temperature. 60 Low molecular weight chitosan was obtained by irradiation degradation with Co γ rays;

[0007] S2. Preparation of quaternary ammonium salt etherifying agent: N,N-dimethyl long-chain alkyl tertiary amine is added to a container. During stirring and heating, epichlorohydrin is slowly added dropwise. After the temperature is raised and kept constant, the remaining epichlorohydrin is removed. The product is washed with anhydrous ethanol and dried to obtain the quaternary ammonium salt etherifying agent.

[0008] S3. Preparation of bactericide: Add acetic acid solution to the low molecular weight chitosan obtained in S1, stir evenly at room temperature to obtain chitosan solution, then add the quaternary ammonium salt etherifying agent obtained in S2, react at constant temperature, then precipitate with anhydrous ethanol, filter and dry to obtain low molecular weight chitosan quaternary ammonium salt bactericide.

[0009] Preferably, in S1, the irradiation dose is 50-150 kGy and the irradiation time is 17-50 h.

[0010] Preferably, in S1, the viscosity-average molecular weight of the degraded chitosan is 50-100 kDa.

[0011] Preferably, in S2, the molar ratio of epichlorohydrin to N,N-dimethyl long-chain alkyl tertiary amine is 2-5:1.

[0012] Preferably, the N,N-dimethyl long-chain alkyl tertiary amine is N,N-dimethyldodecyl tertiary amine or N,N-dimethyltetradecyl tertiary amine.

[0013] Preferably, in S2, the dropping time is less than 30 minutes; the constant temperature reaction temperature is 40-70°C, and the reaction time is 3-6 hours; the drying is vacuum drying, with a temperature of 40-55°C and a time of 6-12 hours.

[0014] Preferably, in step S3, the acetic acid solution has a volume fraction of 2%.

[0015] Preferably, in S3, the mass concentration of the chitosan solution is 1-3%; the molar ratio of the quaternary ammonium salt etherifying agent to chitosan is 0.3-0.9:1.

[0016] Preferably, in step S3, the isothermal reaction is carried out at a temperature of 60-80°C for 5-8 hours; the drying is carried out under vacuum at a temperature of 55-70°C for 6-12 hours.

[0017] The second objective of this invention is to provide a bactericide for oilfield water injection treatment prepared by the above method.

[0018] Compared with the prior art, the advantages of this invention are as follows:

[0019] (1) Chitosan is the only alkaline polysaccharide in nature containing amino groups. Its wide availability, environmental friendliness, easy biodegradability, good biocompatibility, and antibacterial and bacteriostatic properties have led to its widespread application in biomedicine, food, and wastewater treatment. However, because chitosan is only soluble in a few acidic aqueous solutions, its application is greatly limited. This invention addresses this issue by… 60 Co-γ irradiation degrades chitosan without altering its molecular structure. The resulting low-molecular-weight chitosan exhibits low viscosity, low toxicity, and improved antibacterial and solubility. By loading long-chain alkyl quaternary ammonium salt groups with antibacterial properties onto the chitosan, an environmentally friendly bactericide can be obtained. This bactericide is characterized by its wide availability of raw materials, broad applicability, high efficiency, easy degradation, and lack of pollution. Compared with existing oilfield bactericides, it demonstrates significant effectiveness.

[0020] (2) The bactericide prepared by the present invention has the advantages of low dosage and good bactericidal effect. When the dosage of the bactericide is 30-60 mg / L, the bactericidal rate can reach more than 99%. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0023] Example 1

[0024] A method for preparing a bactericide for oilfield water injection treatment includes the following steps:

[0025] S1. Preparation of low molecular weight chitosan: A completely dried chitosan powder sample was placed in an irradiation tube, nitrogen gas was introduced for 5 minutes to remove oxygen, and then the tube was sealed. The irradiation was carried out at room temperature. 60 The chitosan was degraded by gamma irradiation in a Co radioactive source chamber with an irradiation dose of 150 kGy and an irradiation time of 50 h, resulting in low molecular weight chitosan with a viscosity-average molecular weight of 50 kDa.

[0026] S2. Preparation of quaternary ammonium salt etherifying agent: 0.1 mol of N,N-dimethyldodecyl tertiary amine was added to a four-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. Heating and mechanical stirring were turned on. 0.3 mol of epichlorohydrin was placed in a dropping funnel and slowly added to the four-necked flask. After the addition was completed within 30 min, the temperature was raised to 60 °C and the reaction was kept at a constant temperature for 4 h. After the reaction was completed, the unreacted epichlorohydrin was removed by rotary evaporation under reduced pressure. The flask was washed three times with anhydrous ethanol and dried under vacuum at 45 °C for 12 h to obtain the quaternary ammonium salt etherifying agent epichlorohydrin dimethyldodecyl ammonium chloride.

[0027] S3. Preparation of bactericide: 3g (0.018mol) of low molecular weight chitosan obtained in S1 was placed in a three-necked flask, and 100mL of 2% acetic acid solution was added. The mixture was stirred at room temperature to obtain a chitosan solution. Then, 4g (0.012mol) of quaternary ammonium salt etherifying agent glycidyl dimethyl dodecyl ammonium chloride obtained in S2 was added. The mixture was reacted at 70℃ for 7h. After the reaction was completed, the product was precipitated with anhydrous ethanol, filtered repeatedly, and dried under vacuum at 60℃ for 12h to obtain the low molecular weight chitosan quaternary ammonium salt bactericide.

[0028] Example 2

[0029] A method for preparing a bactericide for oilfield water injection treatment includes the following steps:

[0030] S1. Preparation of low molecular weight chitosan: A completely dried chitosan powder sample was placed in an irradiation tube, nitrogen gas was introduced for 5 minutes to remove oxygen, and the tube was then sealed. The irradiation was carried out at room temperature. 60 The chitosan was degraded by gamma irradiation in a Co radioactive source chamber with an irradiation dose of 50 kGy and an irradiation time of 17 h, resulting in low molecular weight chitosan with a viscosity-average molecular weight of 100 kDa.

[0031] S2. Preparation of quaternary ammonium salt etherifying agent: 0.1 mol of N,N-dimethyldodecyl tertiary amine was added to a four-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. Heating and mechanical stirring were turned on. 0.2 mol of epichlorohydrin was placed in a dropping funnel and slowly added to the four-necked flask. After the addition was completed within 30 min, the temperature was raised to 60 °C and the reaction was kept at a constant temperature for 4 h. After the reaction was completed, the unreacted epichlorohydrin was removed by rotary evaporation under reduced pressure. The flask was washed three times with anhydrous ethanol and dried under vacuum at 45 °C for 12 h to obtain the quaternary ammonium salt etherifying agent epichlorohydrin dimethyldodecyl ammonium chloride.

[0032] S3. Preparation of bactericide: 3g (0.018mol) of low molecular weight chitosan obtained in S1 was placed in a three-necked flask, and 100mL of 2% acetic acid solution was added. The mixture was stirred at room temperature to obtain a chitosan solution. Then, 5.1g (0.016mol) of quaternary ammonium salt etherifying agent glycidyl dimethyl dodecyl ammonium chloride obtained in S2 was added. The mixture was reacted at 70℃ for 7h. After the reaction was completed, the product was precipitated with anhydrous ethanol, filtered repeatedly, and dried under vacuum at 60℃ for 12h to obtain the low molecular weight chitosan quaternary ammonium salt bactericide.

[0033] Example 3

[0034] A method for preparing a bactericide for oilfield water injection treatment includes the following steps:

[0035] S1. Preparation of low molecular weight chitosan: A completely dried chitosan powder sample was placed in an irradiation tube, nitrogen gas was introduced for 5 minutes to remove oxygen, and the tube was then sealed. The irradiation was carried out at room temperature. 60 The chitosan was degraded by gamma irradiation in a Co radioactive source chamber with an irradiation dose of 100 kGy and an irradiation time of 33 h, resulting in low molecular weight chitosan with a viscosity-average molecular weight of 65 kDa.

[0036] S2. Preparation of quaternary ammonium salt etherifying agent: 0.1 mol of N,N-dimethyltetradecyl tertiary amine was added to a four-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. Heating and mechanical stirring were turned on. 0.5 mol of epichlorohydrin was placed in a dropping funnel and slowly added to the four-necked flask. After the addition was completed within 30 min, the temperature was raised to 60 °C and the reaction was kept at a constant temperature for 4 h. After the reaction was completed, the unreacted epichlorohydrin was removed by rotary evaporation under reduced pressure. The flask was washed three times with anhydrous ethanol and dried under vacuum at 45 °C for 12 h to obtain the quaternary ammonium salt etherifying agent epichlorohydrin dimethyltetradecyl ammonium chloride.

[0037] S3. Preparation of bactericide: 3g (0.018mol) of low molecular weight chitosan obtained in S1 was placed in a three-necked flask, and 100mL of 2% acetic acid solution was added. The mixture was stirred evenly at room temperature to obtain a chitosan solution. Then, 1.8g (0.005mol) of ammonium salt etherifying agent glycidyl dimethyl tetradecyl ammonium chloride obtained in S2 was added. The mixture was reacted at 70℃ for 7h. After the reaction was completed, the product was precipitated with anhydrous ethanol, filtered repeatedly, and dried under vacuum at 60℃ for 12h to obtain the low molecular weight chitosan quaternary ammonium salt bactericide.

[0038] Example 4

[0039] A method for preparing a bactericide for oilfield water injection treatment includes the following steps:

[0040] S1. Preparation of low molecular weight chitosan: A completely dried chitosan powder sample was placed in an irradiation tube, nitrogen gas was introduced for 5 minutes to remove oxygen, and then the tube was sealed. The irradiation was carried out at room temperature. 60 The chitosan was degraded by gamma irradiation in a Co radioactive source chamber with an irradiation dose of 150 kGy and an irradiation time of 50 h, resulting in low molecular weight chitosan with a viscosity-average molecular weight of 50 kDa.

[0041] S2. Preparation of quaternary ammonium salt etherifying agent: 0.1 mol of N,N-dimethyldodecyl tertiary amine was added to a four-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. Heating and mechanical stirring were turned on. 0.3 mol of epichlorohydrin was placed in a dropping funnel and slowly added to the four-necked flask. After the addition was completed within 30 min, the temperature was raised to 40 °C and the reaction was kept at a constant temperature for 6 h. After the reaction was completed, the unreacted epichlorohydrin was removed by rotary evaporation under reduced pressure. The flask was washed three times with anhydrous ethanol and dried under vacuum at 55 °C for 6 h to obtain the quaternary ammonium salt etherifying agent epichlorohydrin dimethyldodecyl ammonium chloride.

[0042] S3. Preparation of bactericide: 3g (0.018mol) of low molecular weight chitosan obtained in S1 was placed in a three-necked flask, and 100mL of 2% acetic acid solution was added. The mixture was stirred at room temperature to obtain a chitosan solution. Then, 4g (0.012mol) of quaternary ammonium salt etherifying agent glycidyl dimethyl dodecyl ammonium chloride obtained in S2 was added. The mixture was reacted at 80℃ for 5h. After the reaction was completed, the product was precipitated with anhydrous ethanol, filtered repeatedly, and dried under vacuum at 55℃ for 10h to obtain the low molecular weight chitosan quaternary ammonium salt bactericide.

[0043] Example 5

[0044] A method for preparing a bactericide for oilfield water injection treatment includes the following steps:

[0045] S1. Preparation of low molecular weight chitosan: A completely dried chitosan powder sample was placed in an irradiation tube, nitrogen gas was introduced for 5 minutes to remove oxygen, and then the tube was sealed. The irradiation was carried out at room temperature. 60 The chitosan was degraded by gamma irradiation in a Co radioactive source chamber with an irradiation dose of 150 kGy and an irradiation time of 50 h, resulting in low molecular weight chitosan with a viscosity-average molecular weight of 50 kDa.

[0046] S2. Preparation of quaternary ammonium salt etherifying agent: 0.1 mol of N,N-dimethyldodecyl tertiary amine was added to a four-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. Heating and mechanical stirring were turned on. 0.3 mol of epichlorohydrin was placed in a dropping funnel and slowly added to the four-necked flask. After the addition was completed within 30 min, the temperature was raised to 70 °C and the reaction was kept at a constant temperature for 3 h. After the reaction was completed, the unreacted epichlorohydrin was removed by rotary evaporation under reduced pressure. The flask was washed three times with anhydrous ethanol and dried under vacuum at 40 °C for 10 h to obtain the quaternary ammonium salt etherifying agent epichlorohydrin dimethyldodecyl ammonium chloride.

[0047] S3. Preparation of bactericide: 3g (0.018mol) of low molecular weight chitosan obtained in S1 was placed in a three-necked flask, and 100mL of 2% acetic acid solution was added. The mixture was stirred at room temperature to obtain a chitosan solution. Then, 4g (0.012mol) of quaternary ammonium salt etherifying agent glycidyl dimethyl dodecyl ammonium chloride obtained in S2 was added. The mixture was reacted at 60℃ for 8h. After the reaction was completed, the product was precipitated with anhydrous ethanol, filtered repeatedly, and dried under vacuum at 70℃ for 6h to obtain the low molecular weight chitosan quaternary ammonium salt bactericide.

[0048] Comparative Example 1

[0049] The preparation method of the bactericide is the same as in Example 1, except that the chitosan was not degraded by irradiation.

[0050] The bactericides obtained in Examples 1-3 and Comparative Example 1 were evaluated for their bactericidal effects. The water used was injection water from an oilfield polymer injection station. Sulfate-reducing bacteria (SRB) and saprophytic bacteria (TGB) were cultured in the laboratory and used as experimental strains. The evaluation was conducted according to the China National Petroleum Corporation enterprise standard Q / SY49-2010 "Technical Requirements for Bactericides Used in Oilfields." The bactericidal rate was calculated mainly by testing the bacterial content in water samples before and after adding the bactericide. The test results are shown in Table 1.

[0051]

[0052] As shown in Table 1, the bactericide obtained in this invention, at a concentration of 30-60 mg / L, effectively removes sulfate-reducing bacteria and saprophytic bacteria from oilfield injection water compared to the unirradiated chitosan quaternary ammonium salt bactericide in Comparative Example 1, achieving a bactericidal rate of over 99%. This invention, by irradiating chitosan and loading it with long-chain alkyl quaternary ammonium salt groups possessing antibacterial properties, yields an environmentally friendly bactericide with wide-ranging raw material sources, broad applicability, high efficiency, easy degradation, and no pollution. Compared to existing oilfield bactericides, it exhibits significant advantages.

[0053] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0054] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An application of a chitosan quaternary ammonium salt bactericide in oilfield water injection treatment to remove sulfate-reducing bacteria and saprophytic bacteria, characterized in that, The preparation method of the chitosan quaternary ammonium salt bactericide includes the following steps: S1. Preparation of low molecular weight chitosan: The chitosan sample was placed in a container, nitrogen gas was introduced to remove oxygen, and the container was sealed. The mixture was then incubated at room temperature. 60 Co γ Low molecular weight chitosan was obtained by irradiation degradation with X-rays. The viscosity-average molecular weight of the degraded chitosan is 50-100 kDa. S2. Preparation of quaternary ammonium salt etherifying agent: N,N-dimethyl long-chain alkyl tertiary amine is added to a container. During stirring and heating, epichlorohydrin is slowly added dropwise. After the temperature is raised and kept constant, the remaining epichlorohydrin is removed. The product is washed with anhydrous ethanol and dried to obtain the quaternary ammonium salt etherifying agent. The molar ratio of epichlorohydrin to N,N-dimethyl long-chain alkyl tertiary amine is 2-5:1; The N,N-dimethyl long-chain alkyl tertiary amine is N,N-dimethyldodecyl tertiary amine or N,N-dimethyltetradecyl tertiary amine; S3. Preparation of bactericide: Add acetic acid solution to the low molecular weight chitosan obtained in S1, stir evenly at room temperature to obtain chitosan solution, then add the quaternary ammonium salt etherifying agent obtained in S2, react at constant temperature, then precipitate with anhydrous ethanol, filter and dry to obtain chitosan quaternary ammonium salt bactericide. The acetic acid solution has a volume fraction of 2%; The mass concentration of the chitosan solution is 1-3%; the molar ratio of the quaternary ammonium salt etherifying agent to chitosan is 0.3-0.9:

1.

2. The application of the chitosan quaternary ammonium salt bactericide according to claim 1 in the removal of sulfate-reducing bacteria and saprophytic bacteria in oilfield water injection treatment, characterized in that, In S1, the irradiation dose is 50-150 kGy, and the time is 17-50 h.

3. The application of the chitosan quaternary ammonium salt bactericide according to claim 1 in the removal of sulfate-reducing bacteria and saprophytic bacteria in oilfield water injection treatment, characterized in that, In S2, the dropping time is less than 30 minutes; the constant temperature reaction temperature is 40-70℃ and the reaction time is 3-6 hours; the drying is vacuum drying at a temperature of 40-55℃ for 6-12 hours.

4. The application of the chitosan quaternary ammonium salt bactericide according to claim 1 in the removal of sulfate-reducing bacteria and saprophytic bacteria in oilfield water injection treatment, characterized in that, In S3, the isothermal reaction is carried out at a temperature of 60-80℃ for 5-8 hours; the drying is carried out under vacuum at a temperature of 55-70℃ for 6-12 hours.

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