Biological desulfurizer for removing organic sulfur in fracturing flowback fluid and application thereof

Abstract

The invention discloses a biological desulfurizer for removing organic sulfur in fracturing flowback fluid and application thereof. The biological desulfurizer includes a compound with a triazine structure formed by modifying chitosan with aldehydes and inorganic salts. The triazine structure has a good removal effect on hydrogen sulfide and organic sulfur such as mercaptan and sulfide. The biological desulfurizer of the invention has a sulfur capacity of up to 250 g/kg and a desulfurization efficiency of over 95% in 15 min. It can effectively remove the stink of sulfur-containing working water, improve the working environment of the well site, and reduce the impact of sulfur compounds on the atmospheric environment during the development of oil and gas fields.

Claims

1. A biological desulfurizer for removing organic sulfur in fracturing flowback fluid, comprising a compound with a triazine structure formed by modifying chitosan with aldehydes and inorganic salts; the preparation method of the biological desulfurizer includes the following steps: (1) preparing a chitosan solution; (2) adding aldehyde to the chitosan solution, adjusting the pH to 9-10, and quickly stirring at room temperature to obtain a reaction solution; (3) adding inorganic salts to the reaction solution, heating and stirring for 5-8 h to obtain a mixed solution; (4) steaming out the solvent in the mixed liquid under reduced pressure to obtain the biological desulfurizer.

2. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1, wherein the aldehyde is dialdehyde or multiple aldehyde.

3. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 2, wherein the dialdehyde is one or more of formaldehyde, glyoxal and glutaraldehyde, and the multiple aldehyde is paraformaldehyde.

4. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1, wherein the inorganic salts is one or more of iron chloride, ferrous chloride, aluminum chloride, iron sulfate, ferrous sulfate, and aluminum sulfate.

5. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1, wherein the dosage ratio of the chitosan to the aldehydes and the inorganic salts is 10 g: (100-300) mmol:(40-100) mmol.

6. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1, in the step (1), the chitosan is dissolved in a solution containing acetic acid and ethanol to obtain the chitosan solution.

7. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1, in the step (2), the stirring speed is 300-500 r/min, and the stirring time is 20-30 min.

8. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1, in the step (3), the temperature for heating and stirring is 80-90? C.

9. The biological desulfurizer for removing organic sulfur in fracturing flowback fluid according to claim 1 is used to remove organic sulfur from fracturing flowback fluid in oil and gas fields.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Accompanying drawings are for providing further understanding of embodiments of the disclosure. The drawings form a part of the disclosure and illustrate the principle of the embodiments of the disclosure along with the literal description. The drawings in the description below are merely some embodiments of the disclosure; a person skilled in the art can obtain other drawings according to these drawings without creative efforts. In the figures:

(2) FIG. 1 shows the desulfurization efficiencies at different processing times in Example 1;

(3) FIG. 2A is a gas chromatogram of organic sulfur detection in fracturing flowback fluid before treatment in Example 2;

(4) FIG. 2B is a gas chromatogram of organic sulfur detection in fracturing flowback fluid after treatment in Example 2;

(5) FIG. 3A is a gas chromatogram of organic sulfur detection in fracturing flowback fluid before treatment with desulfurizer s-triazine-1,3,5-triethanol in Comparative Example 1;

(6) FIG. 3B is a gas chromatogram of organic sulfur detection in fracturing flowback fluid after treatment with desulfurizer s-triazine-1,3,5-triethanol in Comparative Example 1;

(7) FIG. 4A is a gas chromatogram of organic sulfur detection in fracturing flowback fluid before treatment with desulfurizer 2-aminoethanol in Comparative Example 2;

(8) FIG. 4B is a gas chromatogram of organic sulfur detection in fracturing flowback fluid after treatment with desulfurizer 2-aminoethanol in Comparative Example 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(9) The following is a clear and complete description of the technical solution in conjunction with some embodiments of the present invention. Obviously, the following embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technical personnel in the art without creative labor fall within the scope of protection of the present invention.

Example 1

(10) Weighing 10 g of chitosan and dissolving it in 400 mL of a solution of acetic acid and ethanol to prepare a chitosan solution, wherein the mass percentage of acetic acid is 1%. And then adding 100 mmol of paraformaldehyde into the chitosan solution, and adjusting the pH of the reaction solution to 10 by using hydrochloric acid or sodium hydroxide. After stirring at 300 r/min for 20 min at room temperature, adding 50 mmol of ferric chloride and stirring for 5 hours under constant temperature water bath conditions of 80? C. After the completion of the reaction, the solvent is evaporated under reduced pressure to obtain a powdered biological desulfurizer, which is then dried at 50? C. for later use.

Example 2

(11) Weighing 10 g of chitosan and dissolving it in 400 mL of a solution of acetic acid and ethanol to prepare a chitosan solution, wherein the mass percentage of acetic acid is 1%. And then adding 100 mmol of glutaraldehyde into the chitosan solution, and adjusting the pH of the reaction solution to 9 by using hydrochloric acid or sodium hydroxide. After stirring at 300 r/min for 30 min at room temperature, adding 40 mmol of ferric chloride and stirring for 5 hours under constant temperature water bath conditions of 85? C. After the completion of the reaction, the solvent is evaporated under reduced pressure to obtain a powdered biological desulfurizer, which is then dried at 50? C. for later use.

Application Example 1

(12) Adding the biological desulfurizer prepared in Example 1 to the fracturing back-flow fluid with a clear stink, and stirring at 1500 r/min for 30 min, where the concentration of the biological desulfurizer in the fracturing back-flow fluid is 200 mg/L. FIG. 1 shows the desulfurization efficiency of organic sulfur under different treatment times. From FIG. 1, it can be seen that the desulfurizer of the present invention has no stink in the fracturing back-flow fluid after 15 min of treatment, and the desulfurization efficiency reaches over 95%, indicating a significant removal effect on sulfides.

(13) Using a gas chromatograph to detect the gas chromatographic peaks of organic sulfur by headspace sampling method, and calculating the desulfurization efficiency of organic sulfur based on the changes in peak area before and after the addition of desulfurizer. The specific calculation method for the desulfurization efficiency of organic sulfur is as follows:

(14) $?=\left(1-\frac{A_2}{A_1}\right)?100\%$

(15) In the above equation: ? Is the desulfurization rate of organic sulfur; A.sub.1 and A.sub.2 are the gas chromatographic peak areas of organic sulfur pollutants in the fracturing back-flow fluid before and after treatment respectively. The analysis conditions for gas chromatography are as follows: HP-PLOT-Q capillary column; He serves as the carrier gas with a flow rate of 1.0 mL/min and a purge rate of 6.0 mL/min; the sample inlet temperature is 200? C., and the initial column oven temperature of the column temperature program is 60? C.; the temperature is raised at a rate of 20? C./min to 160? C., followed by a rate of 5? C./min to 190? C.; finally, the temperature is raised at a rate of 30? C./min to 220? C. and held for 12 min; headspace injection: using a headspace device, heating the sample to 80? C., and using nitrogen to drive out the volatile gas for detection; the detector is a pulse flame photometric detector (PFPD).

Application Example 2

(16) Adding the biological desulfurizer prepared in Example 2 to the fracturing back-flow fluid with a clear stink, and stirring at 1500 r/min for 20 min, where the concentration of the biological desulfurizer in the fracturing back-flow fluid is 300 mg/L. FIG. 2A shows the gas chromatography of organic sulfur detection in the fracturing back-flow fluid before treatment, and FIG. 2B shows the gas chromatography of organic sulfur detection in the fracturing back-flow fluid after treatment. From FIGS. 2A and 2B, it can be seen that the desulfurizer of the present invention can significantly remove hydrogen sulfide and organic sulfur such as mercaptan and sulfide. This indicates that the biological desulfurizer of the present invention can simultaneously remove multiple sulfides in the fracturing flowback fluid of oil and gas fields, and has strong removal ability for organic sulfur and high sulfur capacity.

Comparative Example 1

(17) Adding the desulfurizer s-triazine-1,3,5-triethanol to the fracturing back-flow fluid with a clear stink, and stirring at 1500 r/min for 30 min, where the concentration of the desulfurizer in the fracturing back-flow fluid is 300 mg/L. After treatment, the fracturing flowback fluid still has a stink. FIG. 3A shows the gas chromatography of the fracturing flowback fluid before treatment, and FIG. 3B shows the gas chromatography of the fracturing flowback fluid after treatment. From FIGS. 3A and 3B, it can be seen that the desulfurizer s-triazine-1,3,5-triethanol only has a good removal effect on hydrogen sulfide, but there is still a large amount of organic sulfur such as mercaptan and sulfide in the fracturing flowback fluid.

Comparative Example 2

(18) Adding the desulfurizer 2-aminoethanol to the fracturing back-flow fluid with a clear stink, and stirring at 1500 r/min for 30 min, where the concentration of the desulfurizer in the fracturing back-flow fluid is 300 mg/L. After treatment, the fracturing flowback fluid still has a stink. FIG. 4A shows the gas chromatography of the fracturing flowback fluid before treatment, and FIG. 4B shows the gas chromatography of the fracturing flowback fluid after treatment. From FIGS. 4A and 4B, it can be seen that hydrogen sulfide and organic sulfur compounds such as mercaptan and thioether can still be detected in the fracturing flowback fluid treated with the desulfurizer 2-aminoethanol.

(19) The results from all drawings indicate that the biological desulfurizer prepared by the present invention uses biomass chitosan as raw material and is modified with aldehydes and inorganic salts. The biological desulfurizer has a large triazine structure and high desulfurization efficiency, which can be used for the effective removal of hydrogen sulfide and organic sulfur in the fracturing flowback fluid of oil and gas fields, thereby solving the impact of stinks on the environment.

(20) The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc., made within the spirit and principle of the present invention shall be included in the protection of the present invention.