Salt-resistant antibacterial hydrophobic association fracturing thickening agent and preparation method thereof

Abstract

The invention relates to the technical field of oilfield chemical fracturing, and discloses a salt-resistant antibacterial hydrophobic association fracturing thickening agent and a preparation method thereof, and the thickening agent material comprises pure water, acrylamide, acrylic acid, sodium hydroxide, a quaternary phosphonium salt hydrophobic monomer, a salt-resistant monomer, a complexing agent, a chain transfer agent, an initiator, an oxidizing agent and a reducing agent. The preparation method comprises the following steps: uniformly mixing and stirring pure water, acrylamide, acrylic acid, sodium hydroxide, a quaternary phosphonium salt hydrophobic monomer and a salt-resistant monomer according to certain parts by mass, cooling, transferring into a reaction kettle, introducing nitrogen, sequentially adding a complexing agent, a chain transfer agent, an initiator, an oxidant and a reducing agent, granulating a rubber block after complete reaction, drying and grinding to obtain the salt-resistant polymer. The salt-resistant antibacterial hydrophobic association thickening agent for fracturing is obtained. The thickening agent has relatively good salt-resistant and antibacterial properties.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemical fracturing, and particularly relates to an anti-salt and antibacterial hydrophobic associating fracturing thickening agent and a preparation method thereof. Background Art

[0002] In the process of oil and gas field exploration and development, fracturing technology is a crucial means for enhancing production. By injecting fracturing fluid into underground rock formations under high pressure, fractures are generated, thereby increasing the flow channels of oil and gas and improving the oil and gas recovery rate. However, with the in-depth development of oil and gas fields, the formation environment has become increasingly complex, and problems such as high temperature, high salt, and high pollution have gradually become challenges in fracturing operations. Therefore, developing a new type of fracturing fluid dry powder that not only has antibacterial properties but also can maintain stability in high-temperature and high-salt environments is of great significance for improving the efficiency of oil and gas field development and reducing development costs.

[0003] Traditional fracturing fluid dry powder mainly consists of polymers, crosslinking agents, breaker agents, etc. These materials can better meet the requirements of fracturing operations in conventional environments. However, in high-temperature and high-salt environments, polymers are prone to degradation and crosslinking agents are prone to failure in a bacterial environment, resulting in a decline in the performance of fracturing fluid and affecting the fracturing effect. In addition, due to the possible presence of bacteria and other microorganisms in the formation, they will decompose the organic matter in the fracturing fluid, leading to unstable performance of the fracturing fluid and even the generation of precipitates that block the fractures, seriously affecting the oil and gas recovery rate. When facing a large number of bacteria, a certain amount of strong oxidizing bactericide is generally added to the fracturing fluid. Although it can effectively sterilize, it will break the bacterial cells and generate a large number of disinfection by-products, polluting the water environment. On the other hand, the strong oxidizing bactericide will reduce the viscosity of the fracturing fluid to a certain extent.

[0004] The purpose of this research is to synthesize a new type of antibacterial, anti-salt, and anti-high-temperature fracturing fluid dry powder to meet the requirements of fracturing operations in complex formation environments. Through laboratory simulation experiments and on-site application tests, the performance and effect of the new type of fracturing fluid dry powder are verified. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the fracturing fluid has poor stability in high-temperature and high-salt environments, and when the fracturing fluid is transferred underground, it will be degraded by bacteria existing underground, resulting in a decrease in viscosity and even failure. Therefore, the present invention proposes a new type of thickening agent with anti-salt, anti-high-temperature, and antibacterial properties. When the fracturing fluid reaches underground, the fracturing fluid has good antibacterial properties to prevent bacteria from decomposing the fracturing fluid.

[0006] The present invention provides a preparation method for an anti-salt and antibacterial hydrophobic associating fracturing thickening agent, and the preparation method includes the following steps: 1. By mass parts, 190 - 300 parts of tetradecene or hexadecene or octadecene are subjected to a substitution reaction with 80 - 130 parts of N-chlorosuccinimide (NCS) or 100 - 150 parts of N-bromosuccinimide (NBS) to obtain 1-chloro-tetradecene or 1-chloro-hexadecene or 1-chloro-octadecene or 1-bromo-tetradecene or 1-bromo-hexadecene or 1-bromo-octadecene. Then, 20 - 35 parts of 1-chloro-tetradecene or 1-chloro-hexadecene or 1-chloro-octadecene or 1-bromo-tetradecene or 1-bromo-hexadecene or 1-bromo-octadecene are dissolved in 40 - 50 parts of N,N-dimethylformamide, and then transferred to a four-necked flask. Nitrogen is introduced, and then 7 - 8 parts of trimethylphosphine are dissolved in 10 - 12 parts of N,N-dimethylformamide and transferred to a constant-pressure dropping funnel. The four-necked flask is placed in an oil bath at 130 - 160 °C. Under nitrogen gas flow and magnetic stirring, trimethylphosphine is slowly dropped into the flask through the constant-pressure dropping funnel, and the reaction is carried out for 10 - 12 h. After the reaction is completed, the product is filtered by suction, and then the obtained product is extracted with n-hexane. After separation, it is placed in a vacuum drying oven for drying to obtain the quaternary phosphonium salt hydrophobic monomer product.

[0007] 2. (1) Solution preparation: Pure water, acrylamide, acrylic acid, sodium hydroxide, quaternary phosphonium salt hydrophobic monomer, and salt-resistant monomer are mixed and stirred evenly, and then frozen to -2 °C and transferred to a heat preservation kettle. (2) Nitrogen is introduced into the solution in the reaction kettle, and a complexing agent and a chain transfer agent are added. (3) After 12 minutes, an initiator is added. (4) After 5 minutes, an oxidant is added. (5) After 0.5 minute, a reducing agent is added. After the polymerization reaction starts, the nitrogen pipe is removed and nitrogen gas flow is stopped. (6) After the reaction is complete, it is aged for 2 h, and then granulated, dried, and ground.

[0008] The salt-resistant and antibacterial hydrophobic associating fracturing thickening agent of the present invention comprises the following components by mass parts: 1000 - 1100 parts of pure water, 220 - 280 parts of acrylamide, 50 - 80 parts of acrylic acid, 25 - 45 parts of sodium hydroxide, 2 - 5 parts of quaternary phosphonium salt hydrophobic monomer, 40 - 50 parts of salt-resistant monomer, 0.01 - 0.02 parts of complexing agent, 0.01 - 0.06 parts of chain transfer agent, 0.2 - 0.5 parts of initiator, 0.002 - 0.006 parts of oxidant, and 0.002 - 0.006 parts of reducing agent.

[0009] The anti-salt monomer is one of 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone, the complexing agent is one of sodium citrate, sodium ethylenediaminetetraacetate and diethylenetriaminepentaacetic acid sodium salt, the chain transfer agent is one of sodium hypophosphite and sodium methallylsulfonate, the initiator is one or more of azodiisobutylamidine hydrochloride and azodiisobutimidazoline hydrochloride, the oxidant is one of tert-butyl hydroperoxide and sodium persulfate, and the reducing agent is one of ammonium ferrous sulfate and sodium metabisulfite.

[0010] Compared with the prior art, the present invention has the following benefits: (1) By copolymerizing a quaternary phosphonium salt hydrophobic monomer, an anti-salt monomer, acrylamide and acrylic acid, the present invention obtains an anti-salt and antibacterial hydrophobic associating fracturing thickening agent, which has good anti-salt and high-temperature resistance capabilities, has a relatively high viscosity in high salinity brine and relatively high stability.

[0011] (2) Thanks to the high antibacterial ability of the quaternary phosphonium salt, when the thickening agent reaches underground, it can effectively remove bacteria in formation water, and the thickening agent can kill bacteria without breaking bacterial cells, effectively reducing the outflow of substances inside bacterial cells. On the one hand, it reduces the influence of the outflow of the surfactant contained in the cells on the viscosity of the thickening agent, and on the other hand, it reduces the pollution to groundwater. Description of the Drawings

[0012] Figure 1 is the viscosity of the thickening agents of Examples 1-6 and Comparative Examples 1-3 in brine at different concentrations; Figure 2 is the viscosity of the thickening agents of Examples 1-6 and Comparative Examples 1-3 at high temperature; Figure 3 is the sand-carrying performance of the thickening agents of Examples 1-6 and Comparative Examples 1-3; Figure 4 is the antibacterial performance of the thickening agents of Examples 1-6 and Comparative Examples 1-3; Figure 5 is the content of disinfection by-products generated by Examples 1-6 and Comparative Examples 1-3. Detailed Embodiments

[0013] The following are specific embodiments of the present invention, which further describe the operation scheme of the present invention. However, the protection scope of the present invention includes but is not limited to these embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0014] Example 1: 1. 252 parts of octadecene were subjected to a substitution reaction with 120 parts of N-chlorosuccinimide (NCS) to obtain 1-chloro-octadecene. Then, 28.6 parts of 1-chloro-octadecene were dissolved in 50 parts of N,N-dimethylformamide and transferred to a four-necked flask. Nitrogen was introduced, and then 7 parts of trimethylphosphine were dissolved in 10 parts of N,N-dimethylformamide and transferred to a constant-pressure dropping funnel. The four-necked flask was placed in an oil bath at 150 °C, and trimethylphosphine was slowly dropped into the flask through the constant-pressure dropping funnel under nitrogen flow and magnetic stirring. The reaction was carried out for 10 h. After the reaction was completed, the product was filtered by suction, and the obtained product was extracted with n-hexane. After separation, it was placed in a vacuum drying oven for drying to obtain a quaternary phosphonium salt hydrophobic monomer product.

[0015] 2. (1) Solution preparation: 1040 parts of pure water, 260 parts of acrylamide, 70 parts of acrylic acid, 40 parts of sodium hydroxide, 3 parts of quaternary phosphonium salt hydrophobic monomer, and 45 parts of 2-acrylamido-2-methylpropanesulfonic acid were mixed and stirred evenly by mass fraction, then frozen to -2 °C and transferred to a heat preservation kettle; (2) Nitrogen was introduced into the solution in the reaction kettle, and 0.015 parts of diethylenetriaminepentaacetic acid sodium salt and 0.045 parts of sodium hypophosphite were added; (3) After 12 minutes, 0.05 parts of 2,2'-azobis(2-methylimidazoline) hydrochloride and 0.2 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride were added; (4) After 5 minutes, 0.003 parts of tert-butyl hydroperoxide were added; (5) After 0.5 minutes, 0.003 parts of ammonium ferrous sulfate were added. After the polymerization reaction started, the nitrogen pipe was removed and nitrogen flow was stopped; (6) After the reaction was complete, it was aged for 2 h, and then granulated, dried, and ground. The reaction process is as follows: 。

[0016] Example 2: 1. 250 parts of octadecene were subjected to a substitution reaction with 140 parts of N-bromosuccinimide (NBS) to obtain 1-bromo-octadecene. Then, 33.1 parts of 1-bromo-octadecene were dissolved in 45 parts of N,N-dimethylformamide and transferred to a four-necked flask. Nitrogen was introduced, and then 7.1 parts of trimethylphosphine were dissolved in 10.2 parts of N,N-dimethylformamide and transferred to a constant-pressure dropping funnel. The four-necked flask was placed in an oil bath at 151 °C, and trimethylphosphine was slowly dropped into the flask through the constant-pressure dropping funnel under nitrogen flow and magnetic stirring. The reaction was carried out for 11 h. After the reaction was completed, the product was filtered by suction, and the obtained product was extracted with n-hexane. After separation, it was placed in a vacuum drying oven for drying to obtain a quaternary phosphonium salt hydrophobic monomer product.

[0017] 2. (1) Solution preparation: Mix 1060 parts of pure water, 265 parts of acrylamide, 72 parts of acrylic acid, 37.5 parts of sodium hydroxide, 3.2 parts of quaternary phosphonium salt hydrophobic monomer, and 47 parts of 2-acrylamido-2-methylpropanesulfonic acid by mass in parts and stir evenly. Then freeze it to -2°C and transfer it to a heat-insulating kettle. (2) Pass nitrogen into the solution in the reaction kettle and add 0.02 part of sodium citrate and 0.046 part of sodium hypophosphite. (3) After 12 minutes, add 0.065 part of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 0.21 part of 2,2'-azobis(2-methylpropionitrile) dihydrochloride. (4) After 5 minutes, add 0.0031 part of sodium persulfate. (5) After 0.5 minute, add 0.0032 part of ammonium ferrous sulfate. After the polymerization reaction starts, remove the nitrogen tube and stop passing nitrogen. (6) After the reaction is complete, cure for 2 h, then granulate, dry, and grind. The reaction process is as follows: .

[0018] Example 3: 1. React 224 parts of hexadecene with 125 parts of N-chlorosuccinimide (NCS) through a substitution reaction to obtain 1-chlorohexadecene. Then dissolve 25.8 parts of 1-chlorohexadecene in 43 parts of N,N-dimethylformamide, transfer it to a four-necked flask, pass nitrogen, and then dissolve 7.3 parts of trimethylphosphine in 12 parts of N,N-dimethylformamide and transfer it to a constant-pressure dropping funnel. Place the four-necked flask in an oil bath at 150°C. Under nitrogen passing and magnetic stirring, slowly drop trimethylphosphine into the flask through the constant-pressure dropping funnel and react for 11.5 h. After the reaction is completed, filter the product by suction, then extract the obtained product with n-hexane, separate it, and place it in a vacuum drying oven for drying to obtain the quaternary phosphonium salt hydrophobic monomer product.

[0019] 2. (1) Solution preparation: Mix 1055 parts of pure water, 280 parts of acrylamide, 73 parts of acrylic acid, 38 parts of sodium hydroxide, 4.1 parts of quaternary phosphonium salt hydrophobic monomer, and 48 parts of 2-acrylamido-2-methylpropanesulfonic acid by mass in parts and stir evenly. Then freeze it to -2°C and transfer it to a heat-insulating kettle. (2) Pass nitrogen into the solution in the reaction kettle and add 0.0155 part of diethylenetriaminepentaacetic acid sodium salt and 0.0455 part of sodium hypophosphite. (3) After 12 minutes, add 0.055 part of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 0.22 part of 2,2'-azobis(2-methylpropionitrile) dihydrochloride. (4) After 5 minutes, add 0.0032 part of sodium persulfate. After 0.5 minute, 0.0033 parts of sodium metabisulfite are added. After the polymerization reaction starts, the nitrogen pipe is removed and nitrogen supply is stopped. (6) After the reaction is complete, it is aged for 2 h, and then granulated, dried, and ground. The reaction process is as follows: 。

[0020] Example 4: 1. 224 parts of hexadecene are subjected to a substitution reaction with 125 parts of N-chlorosuccinimide (NCS) to obtain 1-chlorohexadecene. Then, 25.8 parts of 1-chlorohexadecene are dissolved in 43 parts of N,N-dimethylformamide, and then transferred to a four-necked flask. Nitrogen is introduced. Then, 7.3 parts of trimethylphosphine are dissolved in 12 parts of N,N-dimethylformamide and transferred to a constant-pressure dropping funnel. The four-necked flask is placed in an oil bath at 150 °C. Under nitrogen supply and magnetic stirring, trimethylphosphine is slowly dropped into the flask through the constant-pressure dropping funnel, and the reaction is carried out for 11.5 h. After the reaction is completed, the product is filtered by suction, and then the obtained product is extracted with n-hexane. After separation, it is placed in a vacuum drying oven for drying to obtain a quaternary phosphonium salt hydrophobic monomer product.

[0021] 2. (1) Solution preparation: 1020 parts of pure water, 255 parts of acrylamide, 68 parts of acrylic acid, 34 parts of sodium hydroxide, 4.3 parts of quaternary phosphonium salt hydrophobic monomer, and 44 parts of N-vinylpyrrolidone are mixed and stirred evenly according to mass parts, and then frozen to -2 °C and transferred to a heat preservation kettle; (2) Nitrogen is introduced into the solution in the reaction kettle, and 0.012 part of sodium citrate and 0.0153 part of sodium methallylsulfonate are added; (3) After 12 minutes, 0.054 part of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 0.21 part of 2,2'-azobis(2-methylpropionitrile) dihydrochloride are added; (4) After 5 minutes, 0.0033 part of tert-butyl hydroperoxide is added; (5) After 0.5 minute, 0.0033 part of sodium metabisulfite is added. After the polymerization reaction starts, the nitrogen pipe is removed and nitrogen supply is stopped. (6) After the reaction is complete, it is aged for 2 h, and then granulated, dried, and ground. The reaction process is as follows: 。

[0022] Example 5: 1. 196 parts of tetradecene were subjected to a substitution reaction with 115 parts of N-chlorosuccinimide (NCS) to obtain 1-chloro-tetradecene. Then, 23 parts of 1-chloro-tetradecene were dissolved in 41 parts of N,N-dimethylformamide and transferred to a four-necked flask. Nitrogen was introduced, and then 7.5 parts of trimethylphosphine were dissolved in 11.2 parts of N,N-dimethylformamide and transferred to a constant-pressure dropping funnel. The four-necked flask was placed in an oil bath at 148 °C, and trimethylphosphine was slowly dropped into the flask through the constant-pressure dropping funnel under nitrogen flow and magnetic stirring. The reaction was carried out for 11 h. After the reaction was completed, the product was filtered by suction, and then the obtained product was extracted with n-hexane. After separation, it was placed in a vacuum drying oven for drying to obtain a quaternary phosphonium salt hydrophobic monomer product.

[0023] 2. (1) Solution preparation: 1045 parts of pure water, 270 parts of acrylamide, 71 parts of acrylic acid, 36 parts of sodium hydroxide, 4.5 parts of quaternary phosphonium salt hydrophobic monomer, and 41 parts of N-vinylpyrrolidone were mixed and stirred evenly by mass fraction, and then frozen to -2 °C and transferred to a reaction kettle; (2) Nitrogen was introduced into the solution in the reaction kettle, and 0.0153 parts of sodium diethylenetriaminepentaacetate and 0.0155 parts of sodium methallylsulfonate were added; (3) After 12 minutes, 0.051 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 0.23 parts of 2,2'-azobis(2-methylpropionitrile) dihydrochloride were added; (4) After 5 minutes, 0.0035 parts of tert-butyl hydroperoxide were added; (5) After 0.5 minute, 0.0035 parts of ammonium ferrous sulfate were added. After the polymerization reaction started, the nitrogen tube was removed and nitrogen supply was stopped; (6) After the reaction was complete, it was aged for 2 h, and then granulated, dried, and ground. The reaction process is as follows: 。

[0024] Example 6: 1. 200 parts of tetradecene were subjected to a substitution reaction with 138 parts of N-bromosuccinimide (NBS) to obtain 1-bromo-tetradecene. Then, 27.5 parts of 1-bromo-tetradecene were dissolved in 47 parts of N,N-dimethylformamide and transferred to a four-necked flask. Nitrogen was introduced, and then 7.5 parts of trimethylphosphine were dissolved in 11.5 parts of N,N-dimethylformamide and transferred to a constant-pressure dropping funnel. The four-necked flask was placed in an oil bath at 152 °C, and trimethylphosphine was slowly dropped into the flask through the constant-pressure dropping funnel under nitrogen flow and magnetic stirring. The reaction was carried out for 11.5 h. After the reaction was completed, the product was filtered by suction, and then the obtained product was extracted with n-hexane. After separation, it was placed in a vacuum drying oven for drying to obtain a quaternary phosphonium salt hydrophobic monomer product.

[0025] 2. (1) Solution preparation: Mix 1025 parts of pure water, 260 parts of acrylamide, 70 parts of acrylic acid, 36 parts of sodium hydroxide, 4.7 parts of quaternary phosphonium salt hydrophobic monomer, and 45 parts of N-vinylpyrrolidone by mass in parts, stir evenly, then freeze to -2 °C and transfer to a heat preservation kettle; (2) Pass nitrogen into the solution in the reaction kettle and add 0.015 parts of sodium ethylenediaminetetraacetate and 0.015 parts of sodium methallylsulfonate; (3) After 12 minutes, add 0.052 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 0.205 parts of 2,2'-azobis(2-methylpropionitrile) dihydrochloride; (4) After 5 minutes, add 0.0031 parts of tert-butyl hydroperoxide; (5) After 0.5 minutes, add 0.0032 parts of ammonium ferrous sulfate. After the polymerization reaction starts, remove the nitrogen tube and stop passing nitrogen; (6) After the reaction is complete, cure for 2 h, then granulate, dry, and grind. The reaction process is as follows: .

[0026] Comparative Example 1: Comparative Example 1 is basically the same as Example 1, except that: when preparing the solution, the quaternary phosphonium salt hydrophobic monomer is replaced with cetyl dimethyl allyl ammonium chloride.

[0027] Comparative Example 2: Comparative Example 2 is basically the same as Example 1, except that when synthesizing polyacrylamide, the quaternary phosphonium salt hydrophobic monomer is not added, and when preparing the thickener, 10 parts of the quaternary phosphonium salt hydrophobic monomer are added as a bactericide.

[0028] Comparative Example 3: Comparative Example 3 is basically the same as Comparative Example 2, except that when preparing the thickener, 3% hydrogen peroxide is added as a bactericide.

[0029] Test Example: Evaluate the performance of Examples 1-6 and Comparative Examples 1-3.

[0030] (1) Thickening property: Preparation of 40000 salinity brine: Accurately weigh 6.93 g of calcium chloride, 4.67 g of magnesium chloride, 21.07 g of sodium sulfate, and 47.33 g of sodium chloride respectively, and then dilute to 2 L with pure water to obtain 40000 salinity brine.

[0031] The samples of Examples 1-6 and Comparative Examples 1-3 were respectively prepared into solutions with mass fractions of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% and 0.7% using brine with a salinity of 40,000, and the original solution of Bacillus was added to the thickener solution to make the bacterial concentration in the thickener solution reach 10 5 CFU / mL. After stirring, dissolving and standing for 30 min, the viscosities were measured respectively. The specific results are shown in the appendix Figure 1 As shown, the results indicate that for Examples 1-6, due to the presence of quaternary phosphonium salts in the thickener, there is a significant antibacterial effect, and the longer the carbon chain, the higher the viscosity at the same concentration. For Comparative Example 1, as the concentration of the thickener increases, the viscosity increases very slowly, indicating that bacteria have an obvious impact on the thickener, showing that quaternary ammonium salts have a weak resistance to Bacillus. The reason for the obvious decrease in viscosity in Comparative Example 2 is that when preparing the thickener, a quaternary phosphonium salt monomer is added again. Although it has an antibacterial effect, the quaternary phosphonium salt monomer, as a surfactant, affects the viscosity of the thickener. The viscosity of Comparative Example 3 increases steadily with the increase in concentration, indicating that the bactericide has an obvious effect on Bacillus, and there is no obvious phenomenon that bacteria affect the viscosity of the thickener

[0032] (2) Viscosity and retention rate at high temperature: To balance the viscosity and dissolution performance, a dosage concentration of 0.4% was selected, and then the viscosities of different thickeners at 60 °C were measured respectively. The results are shown in the appendix Figure 2 As shown, the results indicate that the viscosity retention rates of Examples 1-6 at 60 °C are all above 60%, indicating that in addition to good antibacterial and salt resistance properties, Examples 1-6 also have good high-temperature resistance. Due to the poor antibacterial ability of the thickener in Comparative Example 1, and the quaternary phosphonium salt added alone in Comparative Example 2, as a surfactant, affects the viscosity of the thickener at high temperature, so the viscosity retention rate at high temperature is very low. The viscosity retention rate of Comparative Example 3 is slightly lower than that of the examples because hydrogen peroxide has a degradation effect on the thickener at high temperature

[0033] (3) Sand-carrying performance: 0.8 g of the samples of Examples 1-6 and Comparative Examples 1-3 were respectively weighed and dissolved in 199.2 g of brine, and the original solution of Bacillus was added to make the bacterial content in the thickener solution reach 10 5 CFU / mL. After dissolution and standing for 30 min, 100 mL was taken and placed in a 250 mL beaker, 0.4 mL of a crosslinking agent (such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, etc.) and 25 mL of fine sand (20-40 mesh) were added. After stirring evenly, it was transferred to a graduated cylinder, and the sedimentation rate of the fine sand was observed and recorded. The specific results are shown in the following figure, as shown in the appendix Figure 3As shown, Examples 1-6 have good antibacterial and salt resistance properties, can fully react with the crosslinking agent, and have good proppant-carrying performance. In Comparative Example 1, the viscosity of the thickening agent was affected by bacteria, and the effect was significantly reduced, and it could not produce a strong crosslinking effect with the crosslinking agent. In Comparative Example 2, due to the absence of hydrophobic monomers, it was difficult to produce a crosslinking effect with the crosslinking agent, so the proppant-carrying ability was poor. The bactericide in Comparative Example 3 had a significant effect on bacteria, and the thickening agent and the crosslinking agent could act effectively. Therefore, the proppant-carrying ability was significantly better than that of Comparative Examples 1-2.

[0034] (4)Antibacterial performance: To further understand the antibacterial ability of the thickening agents of Examples 1-6 and Comparative Examples 1-3 against Bacillus subtilis, we separately weighed 0.8 g of the samples of Examples 1-6 and Comparative Examples 1-3 and dissolved them in 199.2 g of brine, and added the original Bacillus subtilis solution to make the bacterial content in the thickening agent solution reach 10 5 CFU / mL. After dissolution, it was left standing for 30 min, and the bacterial content in different thickening agents was detected respectively. The results are as shown in the appendix Figure 4 As shown, the results show that the thickening agents containing quaternary phosphonium salts in Examples 1-6 and Comparative Example 2 have strong antibacterial ability against Bacillus subtilis, the remaining bacteria count is less than 5000 CFU / mL, and the removal rate of bacteria is as high as about 95%. However, the thickening agent in Comparative Example 1 has poor antibacterial ability and cannot effectively antibacterial. Comparative Example 3 added a bactericide, further improving the bactericidal effect, and the removal rate of bacteria reached about 98%.

[0035] (5)Content of disinfection by-products: Although the bactericide has a significant removal rate of Bacillus subtilis, the bactericide directly breaks the bacterial cells to carry out sterilization, which will cause the substances inside the bacterial cells to flow out, generating disinfection by-products to pollute the formation water. The quaternary phosphonium salt thickening agent can sterilize without breaking the bacterial cells, so it can effectively reduce the generation of disinfection by-products. We detected some typical disinfection by-products of the thickening agents of Examples 1-6 and Comparative Examples 1-3. The results are as shown in the appendix Figure 5 As shown, taking the content of disinfection by-products produced in Comparative Example 3 as 100%, the content of disinfection by-products produced in Examples 1-6 and Comparative Example 2 is extremely low, effectively reducing the pollution of the formation water. In Comparative Example 1, the quaternary ammonium salt thickening agent damaged the bacterial cells to a certain extent, resulting in the generation of medium disinfection by-products, while Comparative Example 3 using the bactericide produced a large amount of disinfection by-products, which was easy to pollute the formation water.

Claims

1. A salt-resistant and antibacterial hydrophobic associating fracturing thickener, characterized in that: The raw materials for preparing the thickener include: pure water, acrylamide, acrylic acid, sodium hydroxide, a quaternary phosphonium salt hydrophobic monomer, a salt-resistant monomer, a complexing agent, a chain transfer agent, an initiator, an oxidant and a reducing agent; the salt-resistant monomer is one of 2-acrylamido-2-methylpropanesulfonic acid and N-vinyl pyrrolidone, the complexing agent is one of sodium citrate, sodium ethylenediaminetetraacetate and sodium diethylenetriaminepentaacetate, the chain transfer agent is one of sodium hypophosphite and sodium methyl propylene sulfonate, the initiator is one or two of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride, the oxidant is one of tert-butyl hydroperoxide and sodium persulfate, and the reducing agent is one of ferrous ammonium sulfate and sodium pyrosulfite.

2. The salt-resistant and antibacterial hydrophobic associating fracturing thickener according to claim 1, characterized in that: By weight, 190-300 parts of tetradecene, hexadecene or octadecene are reacted with 80-130 parts of N-chlorosuccinimide (NCS) or 100-150 parts of N-bromosuccinimide (NBS) to obtain 1-chloro-tetradecene, 1-chloro-hexadecene, 1-chloro-octadecene, 1-bromo-tetradecene, 1-bromo-hexadecene or 1-bromo-octadecene; and 20-35 parts of 1-chloro-tetradecene, 1-chloro-hexadecene, 1-chloro-octadecene or 1-bromo-octadecene are reacted with 1-chloro-tetradecene, 1-chloro-hexadecene or 1-chloro-octadecene. 1-bromo-tetradecene or 1-bromo-hexadecene or 1-bromo-octadecene is dissolved in 40-50 parts of N,N-dimethylformamide, and then transferred to a four-necked flask, nitrogen is introduced, and then 7-8 parts of trimethylphosphine are dissolved in 10-12 parts of N,N-dimethylformamide and then transferred to a constant pressure dropping funnel, the four-necked flask is placed in an oil bath pot at 130-160° C., trimethylphosphine is slowly dripped into the flask through the constant pressure dropping funnel under nitrogen and magnetic stirring, and the reaction is carried out for 10-12 hours; after the reaction is completed, the product is filtered, and the obtained product is extracted with n-hexane, separated, and placed in a vacuum drying oven for drying to obtain the quaternary phosphine salt hydrophobic monomer product.

3. The salt-resistant and antibacterial hydrophobic associating fracturing thickener according to claim 1, characterized in that: The raw materials are calculated by weight: 1000-1100 parts of pure water, 220-280 parts of acrylamide, 50-80 parts of acrylic acid, 25-45 parts of sodium hydroxide, 2-5 parts of quaternary phosphonium salt hydrophobic monomer, 40-50 parts of salt-resistant monomer, 0.01-0.02 parts of complexing agent, 0.01-0.06 parts of chain transfer agent, 0.2-0.5 parts of initiator, 0.002-0.006 parts of oxidant and 0.002-0.006 parts of reducing agent.

4. A method for preparing a salt-resistant and antibacterial hydrophobic associating fracturing thickener according to any one of claims 1 to 3, characterized in that: The steps include: (1) Solution preparation: Mix pure water, acrylamide, acrylic acid, sodium hydroxide, quaternary phosphonium salt hydrophobic monomer, and salt-resistant monomer, stir evenly, then freeze to -2 °C and transfer to a heat preservation kettle; (2) nitrogen is introduced into the solution in the reactor to remove oxygen and a complexing agent and a chain transfer agent are added; (3) After 12 minutes, add the initiator; (4) After 5 minutes, add oxidant; (5) After 0.5 minutes, add the reducing agent, and after the polymerization reaction starts, remove the nitrogen tube and stop nitrogen flow; (6) After the reaction is complete, mature for 2 h, then granulate, dry and grind.

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