CN116655488A - Preparation method of a small molecule recyclable self-cleaning fracturing fluid surfactant - Google Patents

Abstract

The invention discloses a preparation method of a small molecule recyclable self-cleaning fracturing fluid surfactant, which belongs to the technical field of petroleum exploitation. The method comprises: mixing long-chain animal and vegetable fatty acids with nucleophilic reagents and basic catalysts, performing condensation reaction to obtain intermediate AMD; mixing the intermediate AMD with chloroacetic acid, performing heating and reflux reaction, and forming emulsion; The sodium hydroxide solution is slowly added dropwise into the emulsion to form a weakly alkaline solution, which reacts to generate sodium chloroacetate and undergoes a quaternization reaction with the intermediate AMD to obtain the surfactant. In the present invention, the biomass raw material—long-chain animal and vegetable fatty acid is used as the raw material and the nucleophile reacts according to a certain ratio, and a catalyst is added to obtain the intermediate AMD. The intermediate AMD is first mixed with chloroacetic acid, and then mixed with sodium hydroxide , inhibit the hydrolysis of sodium chloroacetate, effectively overcome the heterogeneous reaction problem.

Description

Preparation method of a small molecule recyclable self-cleaning fracturing fluid surfactant

technical field

The invention relates to the technical field of petroleum exploitation, in particular to a preparation method of a small molecule recyclable self-cleaning fracturing fluid surfactant.

Background technique

The development of low-permeability oil and gas fields is a worldwide problem. The reservoirs of low-permeability oil and gas fields are relatively complex, with strong heterogeneity. Most formations are highly sensitive to low pressure and low permeability. Affecting the construction effect, there are generally technical bottlenecks that cannot be injected or produced. The transformation of reservoir measures is the most important technological measure to realize the increase in production and injection of low-permeability reservoirs, improve the development status, and confirm the reserves. Improving the fracturing fluid system has become a The main work content of the study on the improvement of low-permeability oil and gas fields.

Surfactant fracturing fluid, also known as viscoelastic surfactant (VES), is currently the traditional method of sodium chloroacetate + water medium method, that is, sodium chloroacetate and tertiary amine are reacted in water medium, but in this reaction, sodium chloroacetate It is easy to decompose under the reaction conditions.

Contents of the invention

In order to solve the problems of the prior art, the invention provides a preparation method of a small molecule recyclable self-cleaning fracturing fluid surfactant. The methods include:

Mix long-chain animal and vegetable fatty acids with nucleophiles and basic catalysts for condensation reaction to obtain intermediate AMD;

The intermediate AMD is mixed with chloroacetic acid, and heated to reflux to form an emulsion;

Slowly add sodium hydroxide solution dropwise into the emulsion to form a weak alkaline solution, react to generate sodium chloroacetate and perform quaternization reaction with the intermediate AMD to obtain the surfactant.

Further, the long-chain animal and vegetable fatty acids are selected from at least one of oleic acid and erucic acid.

Further, the basic catalyst is selected from at least one of potassium hydroxide, barium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, and zinc hydroxide;

The nucleophile is dimethylaminopropylamine.

Further, the condensation reaction conditions are:

The reaction temperature is 160-170°C, and the reaction time is 2-9 hours.

Further, the molar ratio of the long-chain animal and vegetable fatty acids to the nucleophile is 1:1-1.15.

Further, the mass of the basic catalyst is 0.05%-0.25% of the long-chain animal and vegetable fatty acids.

Further, the pH value of the weak alkaline solution is 7-8.

Further, the heating reflux temperature is 95-105°C.

Further, the molar ratio of the intermediate AMD to the sodium chloroacetate is 1:1-1.1.

Further, the quaternization reaction conditions are:

The reaction time is 4-9 hours, and the reaction temperature is 70-100°C.

The beneficial effects brought by the technical solutions provided by the embodiments of the present invention are: in the present invention, biomass raw materials—long-chain animal and plant fatty acids are used as raw materials, the ratio of hydrophilic groups and hydrophobic groups in surfactants is rationally configured, and stimuli-responsive groups are introduced. Reaction of fatty acid and nucleophile according to a certain ratio, and adding catalyst to obtain intermediate AMD. Intermediate AMD is mixed with chloroacetic acid first, and then mixed with sodium hydroxide, which inhibits the hydrolysis of sodium chloroacetate and effectively overcomes the To solve the problem of heterogeneous reaction, and change the synthesis factors, rationally prepare the molecular structure of surfactants, make them assemble in aqueous solution to form viscoelastic worm-like micelles macroscopically, and construct smart worm-like micelles with stimuli-responsiveness ; In addition, using the low-cost surfactant of the present invention as the thickener of the fracturing fluid can significantly reduce the damage of the fracturing fluid to the reservoir.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is the impact figure of reaction temperature provided by the present invention on fatty acid conversion rate;

Fig. 2 is the relationship figure of the amount ratio of substance provided by the present invention and fatty acid conversion rate;

Fig. 3 is the relationship diagram of different reaction times and fatty acid conversion rate provided by the present invention;

Fig. 4 is the infrared spectrogram of intermediate AMD provided by the present invention;

Fig. 5 is the NMR spectrum of the intermediate AMD provided by the present invention;

Fig. 6 is the relationship figure of the amount ratio of substance provided by the present invention and intermediate AMD conversion rate;

Fig. 7 is the relationship diagram of reaction temperature and intermediate AMD conversion rate provided by the present invention;

Fig. 8 is the relation of reaction time provided by the present invention and intermediate AMD transformation rate;

Fig. 9 is the FTIR spectrogram of surfactant provided by the present invention;

Fig. 10 is the ¹ HNMR spectrogram of surfactant provided by the present invention;

Figure 11 is the gamma-lgc test curves of surfactants at different concentrations provided by the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the following will further describe in detail the embodiments of the present invention in conjunction with the accompanying drawings.

Embodiment one

A method for preparing a small molecule recyclable self-cleaning fracturing fluid surfactant, comprising the following steps:

Step (101): Mix oleic acid and dimethylaminopropylamine with a substance ratio of 1:1, add KOH to the mixture, the mass of KOH is 0.05% of the mass of oleic acid, and carry out stirring reaction at a reaction temperature of 160°C , and the reaction time was 7 hours to obtain the intermediate AMD.

Step (102): Mix the intermediate AMD with chloroacetic acid, stir and heat to reflux at 95° C. to form an emulsion.

Step (103): Slowly add sodium hydroxide solution dropwise in the emulsion to form a weak alkaline solution with a pH value of 7, react to generate sodium chloroacetate and carry out quaternization reaction with intermediate AMD, the reaction time is 4 hours, The reaction temperature is 70°C to obtain a surfactant; wherein, the molar ratio of the intermediate AMD to sodium chloroacetate is 1:1.

Embodiment two

A method for preparing a small molecule recyclable self-cleaning fracturing fluid surfactant, comprising the following steps:

Step (201): mix oleic acid and dimethylaminopropylamine with a substance ratio of 1:1.1, add barium hydroxide in the mixture, the quality of barium hydroxide is 0.2% of the mass of oleic acid, carry out stirring reaction, and react The temperature is 170° C., and the reaction time is 8 hours to obtain the intermediate AMD.

Step (202): Mix the intermediate AMD and chloroacetic acid, stir and heat to reflux at 100° C. to form an emulsion.

Step (203): Slowly add sodium hydroxide solution dropwise in the emulsion to form a weakly alkaline solution with a pH value of 7.5, react to generate sodium chloroacetate and carry out quaternization reaction with intermediate AMD, the reaction time is 7 hours, The reaction temperature is 85° C. to obtain a surfactant; wherein, the molar ratio of the intermediate AMD to sodium chloroacetate is 1:1.05.

Embodiment three

A method for preparing a small molecule recyclable self-cleaning fracturing fluid surfactant, comprising the following steps:

Step (301): Mix erucic acid and dimethylaminopropylamine with a substance ratio of 1:1.15, add calcium hydroxide to the mixture, the quality of calcium hydroxide is 0.25% of the mass of oleic acid, carry out stirring reaction, and react The temperature was 170° C., and the reaction time was 9 hours to obtain the intermediate AMD.

Step (302): Mix the intermediate AMD and chloroacetic acid, stir and heat to reflux at 105° C. to form an emulsion.

Step (303): Slowly add sodium hydroxide solution dropwise in the emulsion to form a weak alkaline solution with a pH value of 8, react to generate sodium chloroacetate and carry out quaternization reaction with intermediate AMD, the reaction time is 9 hours, The reaction temperature is 100°C to obtain a surfactant, and the molar ratio of the intermediate AMD to sodium chloroacetate is 1:1-1.1.

It should be noted that the condensation reaction generally uses a basic catalyst, and the synthesis uses a strong basic inorganic base as the catalyst for the condensation reaction; factors affecting the condensation reaction include the ratio of reactants, the amount of catalyst, the reaction temperature, and the reaction time; The conversion rate is a reference index, conversion rate=(acid value before reaction-acid value after reaction)/acid value before reaction×100%.

1. Effect of reaction temperature on fatty acid conversion rate.

According to the reaction kinetics, heating the endothermic reaction can not only speed up the reaction rate, but also increase the conversion rate of the reactant. When the reaction temperature rises to 130°C, bubbles are formed, and the reaction begins to generate water vapor. The product is a reddish-brown liquid. Fig. 1 is that the ratio of fatty acid and dimethylaminopropylamine substance is 1: 1.1, catalyzer 0.2%, the relational diagram of the influence of different temperatures on fatty acid conversion rate, Fig. 1 shows fatty acid and dimethylaminopropylamine in a certain period of time, according to certain formulating During the specific reaction, the higher the reaction temperature, the higher the conversion rate of the reactant with the increase of the reaction temperature, but when the temperature rises to 160 ° C, the conversion rate has tended to be stable. Considering that the temperature is too high for the product The color is affected, and the temperature is generally controlled at 160-170°C.

2. The effect of different molar ratios on the conversion rate of fatty acids.

It can be seen from the chemical balance that the reaction conversion rate of the intermediate AMD will increase by increasing the concentration of the reactant. If the concentration of the reactant fatty acid is increased, the raw materials that do not participate in the reaction cannot be removed in the later stage, and the residue in the product will have a negative impact on the subsequent reaction. Some side reactions affect the performance of its downstream products, so the content of its free fatty acids must be strictly controlled when the intermediate AMD is synthesized; in order to speed up the reaction speed of the intermediate, an excess of dimethylaminopropylamine is generally used to increase the conversion rate of fatty acids , but the price of dimethylaminopropylamine is relatively expensive; and the excess dimethylaminopropylamine will be removed from the intermediate after the reaction, otherwise it will also affect the quality of the final product. Choose the best experimental ratio for comparison with this experiment important. Integrating economic cost and other influencing factors, the different proportions of dimethylaminopropylamine and fatty acid were investigated, and the best raw material proportion was selected according to the experimental results.

Fig. 2 is 170 ℃, catalyst mass fraction is 0.5%, reaction time is the relationship diagram of fatty acid conversion rate and the amount ratio of different substances under the condition of 8h, condensation reaction is a reversible reaction, it can be known from chemical balance and Fig. 2 that fatty acid and When the optimum substance molar ratio of dimethylaminopropylamine was less than 1: 1.1, the reaction conversion rate improved along with the increase of the dimethylaminopropylamine ratio; Dimethylaminopropylamine will not only increase the difficulty of product degassing, but also increase the unit consumption of raw materials, because excessive dimethylaminopropylamine cannot be recycled, and will also increase its pollution to the environment. Therefore, the optimum substance ratio of fatty acid to N,N-dimethylaminopropylamine is 1:1.1.

3. Effect of catalyst concentration on fatty acid conversion rate.

Adding a small amount of catalyst during synthesis can speed up the experiment. As long as the amount of catalyst is well controlled, the color of the product can be reduced under the premise of increasing the reaction speed.

Table 1: Effect of Fatty Acid Catalyst Ratio on Product Appearance

It is found by Table 1 that the addition of catalyst should be controlled at 0.1%～0.2%. The influence of catalyst consumption on fatty acid conversion rate is more obvious. The catalyst consumption is low from 0.1wt% catalyst concentration, the reaction speed is slow, and the fatty acid conversion rate is low; but the catalyst concentration is too high If it is large, it will easily lead to excessive saponification of fatty acids and reduce the content of active substances in the product. The optimum mass fraction of catalyst addition is 0.2%.

4. Effect of reaction time on fatty acid conversion rate.

The amidation reaction is a condensation reaction, and the condensation reaction is reversible. In the reaction, an excess of small molecules is generally used to improve the conversion rate of large molecular weight substances. After the reaction is complete, the unreacted small molecule reactants are removed by vacuum distillation, so that The intermediate product is relatively pure; with the increase of reaction temperature, the rate of forward reaction and reverse reaction will increase, so there is an optimal reaction temperature; in addition, the temperature has an impact on the appearance of the intermediate product, the higher the temperature, the more color the product Deep, from khaki to reddish brown. Fig. 3 is when the molar ratio of reactant substance is 1: 1.1, and when catalyst mass fraction is 0.2%, the relation diagram of the influence of reaction time on fatty acid conversion rate, in general along with prolonging conversion rate of reaction time can improve to some extent, but After increasing to a certain level, the reaction reaches equilibrium, and continuing to prolong the reaction time has little effect on the conversion rate, but it will increase energy consumption. During the reaction process, the acid value was continuously sampled and tested. As can be seen from Figure 3, as the reaction time increases, the conversion rate of fatty acids increases. After 7 hours of reaction, the conversion rate increases slowly. After 8 hours of reaction, it basically remains unchanged, so the optimal reaction time is for 8h.

Next, carry out infrared spectrum analysis to the intermediate AMD prepared in embodiment two, Fig. 4 is the infrared spectrogram of the intermediate AMD of embodiment two, as can be seen from Fig. 4: 3290cm ^-1 is the NH stretching vibration absorption band of amide; The weak and sharp peak at 3081cm ^-1 is another NH stretching vibration absorption band, which is the characteristic peak of monoamide; the strong peak at 1642cm ^-1 is the C=O stretching vibration of secondary amide; 1552cm ^-1 is the NH bending vibration of amide; 1268cm ^-1 is CN stretching vibration; 716cm- ¹ is -(CH ₂ )n deformation vibration (n>4), which is a characteristic peak of long carbon chain.

In addition, infrared spectrum NMR analysis was performed on the intermediate AMD prepared in Example 2, and FIG. 5 is the NMR spectrum of the intermediate AMD prepared in Example 2.

Table 2: NMR analysis results of intermediate AMD

It should also be noted that in the present invention, the feeding method is changed. First, the tertiary amine is mixed with the chloroacetic acid solution, stirred vigorously, and heated to reflux temperature to form an emulsion. The emulsion has certain stability. The layers will be separated immediately, and then the sodium hydroxide solution will be slowly added dropwise through the dropping funnel to generate sodium chloroacetate on the spot and react with the tertiary amine. As the reaction progresses, the generated betaine will act as an emulsifier again. The hydrolysis of sodium chloroacetate is inhibited, and the problem of heterogeneous reaction is effectively overcome.

The influencing factors of the quaternization reaction include reaction temperature, reaction time, and the ratio of the reactants to substances, and the conversion rate of the intermediate AMD is used as the investigation index.

1. The effect of the ratio of reactants on the conversion rate of intermediate AMD.

There is a lone pair of electrons on the N atom of the intermediate AMD, which has strong nucleophilicity, and it is easy to undergo a nucleophilic substitution reaction with chlorinated compounds. If the amount of chloroacetic acid added is too low, the free amine contained in the product will be relatively large; If too much chloroacetic acid is added, the corrosiveness of the product will increase, especially the residual sodium monochloroacetate and sodium dichloroacetate are irritating to the human body, and the unreacted sodium monochloroacetate will be partially converted into Sodium glycolate will also cause the sodium glycolate content of the product to be too high, which will have a certain impact on the final product.

In order to investigate the influence of the molar ratio of raw materials on the synthesis reaction of acid liquid surfactants, the reaction was carried out at 85°C for 7 hours, and the relationship between the conversion rate of intermediate AMD and the amount ratio of different substances is shown in Figure 6; it can be seen from Figure 6 that the amount of substances After the ratio is greater than 1: 1.05, continue to increase the molar ratio of the substance, and the conversion rate of the intermediate AMD increases slowly. Therefore, the ratio of the substance of the intermediate AMD to sodium chloroacetate is 1: 1.05 is more suitable.

2. The influence of reaction temperature on the conversion rate of intermediate AMD.

The reaction temperature has a significant effect on the conversion rate, and the reaction conversion rate increases with the increase of reaction time. The reaction rate is slow at low temperature, and the reaction conversion rate is low. When the temperature increases from 70°C to 90°C, the quaternization reaction rate increases. The higher the temperature, the faster the reaction rate, but the color of the product will also deepen. Fig. 7 is a graph showing the relationship between the conversion rate of intermediate AMD and the reaction temperature when the molar ratio of substances is 1:1.10, the reaction time is 7 hours, and the optimum reaction temperature is 85°C.

3. The influence of reaction time on the conversion rate of intermediate AMD.

Fig. 8 is at 90 DEG C, when the amount ratio of substance is 1: 1.05, different reaction time is to intermediate AMD conversion rate relation figure, from 7 hours to 9 hours conversion rate changes little, considers that reaction time is selected as from energy saving aspect 7 hours.

Next, infrared spectrum analysis was performed on the surfactant prepared in Example 2, and FIG. 9 is an FTIR spectrum of the surfactant prepared in Example 2 provided by the present invention.

Table 3 FTIR characteristic peak assignment of surfactants

Furthermore, nuclear magnetic resonance analysis was performed on the surfactant prepared in Example 2. Figure 10 is the ¹ HNMR spectrum of the surfactant prepared in Example 2 provided by the present invention, and ^{the 1} HNMR spectrum analysis of the surfactant in Table 5, Figure 10 and Table 5 are respectively the 1HNMR spectrum of the surfactant and the chemical shift values of various H protons in the molecule. It can be seen from Figure 10 that the chemical shift δ is the peak corresponding to -CH at _0.89ppm ; δ is 1.27ppm It is the double peak formed by -CH ₂ - on the long-chain alkyl group; the chemical shift δ is the peak connected to the carbonyl group at 2.15ppm; the peak at 7.5ppm is the peak corresponding to the amino group connected to the carbonyl group; δ The single peak at 3.28ppm is the peak corresponding to the N ₊ linked methyl group.

1HNMR spectrogram analysis of table four surfactants

In addition, the surface tension of the surfactant under different conditions determines the dispersibility, that is, in different solutions, the lower the surface tension, the easier the gas-liquid system is dispersed and the better the performance. As the concentration increases, before the critical micelle concentration (CMC) is reached, the surface tension in the system containing the acidic surfactant solution will decrease as the concentration increases, and the surface tension will remain almost unchanged after the solution concentration reaches a certain value. This value is the cmc value of the acid surfactant solution, and Figure 11 shows the gamma-lgc test curves at different concentrations.

It can be seen from Figure 11 that initially, as the concentration gradually increased, the surface tension (γ) gradually decreased. When the concentration reached 4.7×10 ^-5 mol/L (0.19g/L), the γ value was 33.5mN/m, Afterwards, it remains constant, and this concentration is the CMC value of the surfactant. The reason why the surface tension remains constant is that when the concentration is lower than the CMC value, most of the surfactant molecules (or ions) in the solution exist alone. As the concentration of the solution increases, the amount of adsorption on the surface increases accordingly, and the accommodation space for molecules on the surface decreases, so the surface tension remains unchanged. The decrease of γ value is an important factor for the thickening of the solution.

Finally, the fracturing fluid system is prepared by using the surfactants of Example 1, Example 2, and Example 3 as the thickener of the fracturing fluid. The system includes 1wt%-6wt% surfactant and 0.1wt%- 0.6wt% additive, and the rest is water. The obtained three fracturing fluids are compared with the prior art to test the result of core damage.

Table 5: Results of fracturing fluid core damage

It can be seen from Table 5 that the matrix damage rate of the fracturing fluid of the present invention to the rock core is less than 20%. The core damage rate of cross-linked guar gum measured under the same conditions was 28.5%, and the core damage rate of clean fracturing fluid was 19.3%. Therefore, using the low-cost surfactant of the present invention as the thickener of the fracturing fluid can significantly reduce the damage of the fracturing fluid to the reservoir.

It is worth noting that in the present invention, biomass raw materials—long-chain animal and vegetable fatty acids are used as raw materials, the proportion of hydrophilic groups and hydrophobic groups in surfactants is reasonably configured, and stimulus-responsive groups are introduced to combine fatty acids with nucleophiles according to React in a certain proportion, and add catalyst to obtain the intermediate AMD. The intermediate AMD is first mixed with chloroacetic acid and then mixed with sodium hydroxide, which inhibits the hydrolysis of sodium chloroacetate, effectively overcomes the problem of heterogeneous reaction, and changes the synthesis Factors, rationally prepare the molecular structure of the surfactant, make it assemble in the aqueous solution to form worm-like micelles that show viscoelasticity macroscopically, and construct intelligent worm-like micelles with stimulus responsiveness; in addition, adopt the low-cost surface of the present invention The active agent used as the thickener of the fracturing fluid can significantly reduce the damage of the fracturing fluid to the reservoir.

The serial numbers of the above embodiments of the present invention are for description only, and do not represent the advantages and disadvantages of the embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. The preparation method of the small molecule recyclable self-cleaning fracturing fluid surfactant is characterized by comprising the following steps of:

mixing long-chain animal and plant fatty acid with a nucleophilic reagent and an alkaline catalyst, and performing condensation reaction to obtain an intermediate AMD;

mixing the intermediate AMD with chloroacetic acid, and carrying out heating reflux reaction to form emulsion;

slowly dripping sodium hydroxide solution into the emulsion to form weak alkaline solution, reacting to generate sodium chloroacetate, and carrying out quaternization reaction with the intermediate AMD to obtain the surfactant.

2. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the long-chain animal and plant fatty acid is at least one selected from oleic acid and erucic acid.

3. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the alkaline catalyst is at least one selected from potassium hydroxide, barium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide and zinc hydroxide;

the nucleophile is dimethylaminopropylamine.

4. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the condensation reaction conditions are as follows:

the reaction temperature is 160-170 ℃ and the reaction time is 2-9 h.

5. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the molar ratio of the long-chain animal and plant fatty acid to the nucleophile is 1:1 to 1.15.

6. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the mass of the alkaline catalyst is 0.05-0.25% of the mass of the long-chain animal and plant fatty acid.

7. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the pH value of the weakly alkaline solution is 7-8.

8. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, wherein the heating reflux temperature is 95-105 ℃.

9. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the molar ratio of the intermediate AMD to the sodium chloroacetate is 1:1-1.1.

10. The method for preparing the small molecule recyclable self-cleaning fracturing fluid surfactant according to claim 1, which is characterized in that,

the quaternization reaction conditions are as follows:

the reaction time is 4-9 h, and the reaction temperature is 70-100 ℃.