Biological flocculant, preparation method thereof and application of biological flocculant in treatment of fracturing flow-back fluid

Abstract

The invention provides a biological flocculant, a preparation method thereof and application of the biological flocculant in treatment of fracturing flow-back fluid. The biological flocculating agent disclosed by the invention comprises a fermentation product of Providencia retinii sp. Hong 1 Xiao Zong, and can also selectively comprise a fermentation product of bacillus sp. JS Xiao Bai, and the biological flocculating agent disclosed by the invention can be used for preparing the biological flocculating agent. The biological flocculant disclosed by the invention has relatively good salt-resistant and alkali-resistant properties, and is suitable for flocculation treatment of the fracturing flow-back fluid.

Description

Technical Field

[0001] The present invention relates to a biological flocculant, a preparation method thereof, and an application thereof in treating fracturing flowback fluid. Specifically, the present invention relates to a biological flocculant prepared by microbial fermentation, a preparation method of the biological flocculant, and a method for treating fracturing flowback fluid using the flocculant, belonging to the field of fracturing flowback fluid treatment. Background Art

[0002] Hydraulic fracturing, a technique used in unconventional oil and gas field extraction, produces large quantities of frac flowback fluid. This fluid is a complex mixture containing a variety of substances, including naturally occurring radioactive materials, inorganic substances, metals, hydrocarbons, and various chemical additives added to enhance the fluid's performance. These additives include drag reducers like polyacrylamide, biocides, clay stabilizers, antiscalants, and drainage aids. Oil and gas field frac flowback fluid typically has a high pH, high salinity, high suspended solids, high color, high stability, and a complex pollutant profile, making it difficult to treat. Discharge of frac flowback fluid without treatment can have harmful impacts on ecosystems, such as soil salinization, vegetation degradation, drinking water contamination, and human health risks. Treating frac flowback fluid and reusing it in frac fluid formulation is crucial for reducing wastewater volume, lowering operational costs, and mitigating environmental hazards.

[0003] Existing fracturing flowback fluid treatment technologies primarily rely on physical and chemical processes such as coagulation, flotation, and activated carbon adsorption. However, existing physical treatment processes suffer from high costs and limited pollutant removal capabilities. Chemical treatments, such as the use of chemical flocculants like polyacrylamide and polyaluminum chloride, are also costly and prone to secondary environmental pollution.

[0004] Bioflocculation utilizes extracellular polymers produced during microbial fermentation to flocculate and settle pollutants. Compared to physical / chemical treatment processes, bioflocculation treatment processes have advantages such as being environmentally friendly, free of secondary pollution, and low cost. However, there are currently few studies on the treatment of pollutants such as suspended solids in fracturing flowback fluids using microbial flocculants. The main reasons for this may be that, on the one hand, the production of microbial flocculants in existing technologies is generally low, and the flocculation activity is not high, which limits their industrial application; on the other hand, the presence of suspended solids in fracturing flowback fluids is relatively stable, making flocculation relatively difficult. In addition, fracturing flowback fluids have high salinity (approximately 10,000-20,000 mg / L or higher in terms of chloride and sodium ions) and a high pH (approximately pH 8-11). Generally, the flocculation activity of bioflocculants is unstable at high salinity and high pH, thus limiting their application. Summary of the Invention

[0005] An object of the present invention is to provide a bioflocculant.

[0006] Another object of the present invention is to provide the use of the bioflocculant in treating oilfield fracturing flowback fluid.

[0007] Another object of the present invention is to provide a method for treating oilfield fracturing flowback fluid.

[0008] In one aspect, the present invention provides a bioflocculant, comprising: a fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong.

[0009] Providencia rettgeri sp. Hong 1 Xiao Zong is a strain published in the prior art CN109437470B, and its deposit number is CGMCC No.16545.

[0010] According to a specific embodiment of the present invention, in the bioflocculant of the present invention, the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong includes one or more of the following substances:

[0011] Providencia rettgeri sp. Hong 1 Xiao Zong was inoculated into a fermentation medium for fermentation to obtain a fermentation liquid;

[0012] Providencia rettgeri sp. Hong 1 Xiao Zong was inoculated into a fermentation medium for fermentation to obtain a fermentation supernatant;

[0013] Providencia rettgeri sp. Hong 1 Xiao Zong is inoculated into a fermentation medium for fermentation, and the obtained fermentation liquid and / or fermentation supernatant is subjected to alcohol precipitation to obtain a solid substance.

[0014] According to a specific embodiment of the present invention, the bioflocculant of the present invention further comprises a fermentation product of Bacillus sp. JS Xiao Bai.

[0015] Bacillus sp. JS Xiao Bai is a strain published in the prior art CN109437470B, and its deposit number is CGMCC No.16546.

[0016] According to a specific embodiment of the present invention, in the bioflocculant of the present invention, the fermentation product of Bacillus sp.JS Xiao Bai includes one or more of the following substances:

[0017] Bacillus sp.JS Xiao Bai is inoculated into a fermentation medium for fermentation to obtain a fermentation liquid;

[0018] Bacillus sp.JS Xiao Bai was inoculated into a fermentation medium for fermentation to obtain a fermentation supernatant;

[0019] Bacillus sp. JS Xiao Bai is inoculated into a fermentation medium for fermentation, and the fermentation liquid and / or the fermentation supernatant are obtained by alcohol precipitation to obtain a solid substance.

[0020] According to a specific embodiment of the present invention, in the biological flocculant of the present invention, based on the total dry matter content of the fermentation product of Providencia rettgeri sp. Hong 1Xiao Zong and the fermentation product of Bacillus sp. JS Xiao Bai in the flocculant, the amount of dry matter in the fermentation product of Providencia rettgeri sp. Hong 1Xiao Zong is 10% to 100%, and the amount of dry matter in the fermentation product of Bacillus sp. JS Xiao Bai is 0% to 90%.

[0021] According to a specific embodiment of the present invention, in the bioflocculant of the present invention, the mass ratio of the fermentation product of Bacillus sp.JS Xiao Bai and the fermentation product of Providencia rettgerisp. Hong 1 Xiao Zong, calculated on a dry matter basis, is 1:3 to 3:1, preferably 1:2 to 2:1.

[0022] According to a specific embodiment of the present invention, the bioflocculant of the present invention can be a liquid preparation or a solid preparation.

[0023] According to a specific embodiment of the present invention, the bioflocculant of the present invention may further include one or more of the following substances:

[0024] Coagulant aids;

[0025] Excipients and / or carriers.

[0026] According to a specific embodiment of the present invention, in the bioflocculant of the present invention, the coagulant aid may include but is not limited to calcium chloride. Preferably, the mass ratio of the dry matter in the fermentation product of Providencia rettgeris p. Hong1 Xiao Zong to calcium chloride in the bioflocculant is 1:10-10000.

[0027] On the other hand, the present invention also provides a method for preparing the bioflocculant, which comprises:

[0028] Providencia rettgeri sp. Hong 1Xiao Zong was inoculated into a liquid fermentation medium for fermentation;

[0029] The fermentation liquid obtained by fermentation is used directly, or after further separation and purification, with or without adding other substances to prepare the bioflocculant.

[0030] According to a specific embodiment of the present invention, in the preparation method of the bioflocculant of the present invention, the composition of the fermentation medium of Providencia rettgeri sp. Hong 1Xiao Zong may include glucose, (NH4)SO4, urea and yeast extract, and may optionally include one or more of KH2PO4, K2HPO4, NaCl, and MgSO4.

[0031] In some specific embodiments of the present invention, the fermentation medium of Providencia regtgerisp. Hong 1Xiao Zong includes: glucose 5-20 g / L, (NH4)SO4 0.2-3.6 g / L, urea 0.5-1 g / L, yeast extract 0.5-3.6 g / L, KH2PO4 2-5 g / L, K2HPO4 2-5 g / L, NaCl 0.1-1 g / L, MgSO4 0.2-1 g / L.

[0032] According to a specific embodiment of the present invention, in the method for preparing a bioflocculant of the present invention, the fermentation culture conditions of Providencia rettgeri sp. Hong 1 Xiao Zong are as follows: a seed solution with an OD600 of 0.8-1.2, an inoculum size of 1%-10%, a fermentation culture temperature of 10°C-43°C, and a fermentation culture time of 24h-96h, preferably 28h-72h. The preparation of the seed solution of Providencia rettgeri sp. Hong 1 Xiao Zong can be carried out according to conventional operations in the field. The culture medium of the seed solution can be the same as or different from the fermentation medium, for example, LB medium can be used. The fermentation culture process can be carried out in a shaking table with a shaking speed of 110-220r / min, or a stirring method with a speed of 800-220r / min.

[0033] According to a specific embodiment of the present invention, the method for preparing the bioflocculant of the present invention further includes: centrifuging the fermentation broth obtained by fermenting Providencia rettgeri sp. Hong 1Xiao Zong to obtain a supernatant, and further separating the supernatant by alcohol precipitation to obtain a solid substance as the active ingredient of the bioflocculant.

[0034] According to a specific embodiment of the present invention, the method for preparing a bioflocculant of the present invention comprises: fermenting Providencia rettgeri sp. Hong 1Xiao Zong, ultrasonicating the fermentation broth at a pH of 3-11 and a temperature of 20°C-80°C for 2-10 minutes, then centrifuging at 4°C and 5000-8000 rpm for 5-15 minutes to obtain a supernatant; adding 1-5 volumes of ethanol to the supernatant and refrigerating and precipitating the supernatant for 24-72 hours; separating the precipitated flocculent solids, and further drying or not drying as needed to serve as the active ingredient of the bioflocculant. Preferably, the ultrasonication conditions can be 40-100 Hz and the ultrasonication time can be 2-10 minutes. Preferably, the separated flocculent solids can be dried at no more than 80°C to obtain a dry powder for use in preparing the bioflocculant.

[0035] According to a specific embodiment of the present invention, the fermentation product of Providenciarettgeri sp. Hong 1 Xiao Zong obtained in the present invention has a polysaccharide content of about 30%-60% and a protein content of about 5%-15% based on solid content.

[0036] According to a specific embodiment of the present invention, the method for preparing the biological flocculant of the present invention further includes: inoculating Bacillus sp.JS Xiao Bai into a liquid fermentation medium for fermentation, and directly or after further separation and purification, combining the fermentation broth obtained as one of the raw materials with a fermentation product of Providencia rettgerisp. Hong 1 Xiao Zong to prepare the biological flocculant.

[0037] According to a specific embodiment of the present invention, in the preparation method of the biological flocculant of the present invention, the fermentation medium of Bacillus sp.JS Xiao Bai comprises glucose, (NH4)SO4, urea and yeast extract, and may optionally include one or more of KH2PO4, K2HPO4, NaCl and MgSO4.

[0038] In some specific embodiments of the present invention, the fermentation medium of Bacillus sp.JS Xiao Bai includes: glucose 5-20 g / L, (NH4)SO4 0.2-3.6 g / L, urea 0.5-1 g / L, yeast extract 0.5-3.6 g / L, KH2PO4 2-5 g / L, K2HPO4 2-5 g / L, NaCl 0.1-1 g / L, and MgSO4 0.2-1 g / L.

[0039] According to a specific embodiment of the present invention, in the preparation method of the biological flocculant of the present invention, the fermentation culture conditions of Bacillus sp.JS Xiao Bai are: seed liquid with OD600 0.8-1.2, inoculated with an inoculum size of 1%-10%, fermentation culture temperature of 10°C-43°C, and fermentation culture time of 24h-96h, preferably 28h-72h. The preparation of the seed liquid of Bacillus sp.JS Xiao Bai can be carried out with reference to conventional operations in the field. The culture medium of the seed liquid can be the same as or different from the fermentation medium, for example, LB culture medium can be used. During the fermentation culture process, a shaking table culture can be used with a shaking table speed of 110-220r / min, or a stirring method can be used with a speed of 800-220r / min.

[0040] According to a specific embodiment of the present invention, the method for preparing the bioflocculant of the present invention further comprises: centrifuging the fermentation broth obtained by fermenting Bacillus sp.JS Xiao Bai to obtain a supernatant, and further separating the supernatant by alcohol precipitation to obtain a solid substance as the active ingredient of the bioflocculant.

[0041] According to a specific embodiment of the present invention, the preparation method of the bioflocculant of the present invention comprises: fermenting the fermentation broth obtained by Bacillus sp.JS Xiao Bai, ultrasonicating it at pH 3-11 and temperature 20°C-80°C for 2-10 minutes, then centrifuging it at 4°C and 5000-8000 rpm for 5-15 minutes to obtain a supernatant, adding 1-5 volumes of ethanol to the supernatant and refrigerating it for alcohol precipitation for 24-72 hours, separating the precipitated flocculent solid material, and further drying or not drying it as needed to use it as the active ingredient of the bioflocculant. Preferably, the ultrasonic conditions can be 40-100 Hz and the ultrasonic time can be 2-10 minutes. Preferably, the separated flocculent solid material can be dried at no more than 80°C to obtain a dry powder for use in preparing the bioflocculant.

[0042] According to a specific embodiment of the present invention, the fermentation product of Bacillus sp. JS XiaoBai obtained in the present invention has a polysaccharide content of about 30%-60% and a protein content of about 5%-15% based on solid content.

[0043] In the present invention, the fermentation medium of Providencia rettgeri sp. Hong 1 Xiao Zong and the fermentation medium of Bacillus sp. JS Xiao Bai may have the same or different compositions. The fermentation culture conditions and subsequent treatment methods of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the fermentation culture conditions and subsequent treatment methods of the fermentation product of Bacillus sp. JS Xiao Bai may be the same or different.

[0044] On the other hand, the present invention also provides the use of the bioflocculant in preparing a treatment agent for treating fracturing flowback fluid to reduce its color and remove suspended matter.

[0045] On the other hand, the present invention also provides a method for treating fracturing flowback fluid, the method comprising:

[0046] The bioflocculant of the present invention is used to treat fracturing flowback fluid to reduce the chromaticity of the fracturing flowback fluid and remove suspended matter.

[0047] According to a specific embodiment of the present invention, in the method for treating fracturing flowback fluid of the present invention, the bioflocculant is added to the fracturing flowback fluid to be treated, stirred evenly, and then allowed to stand for 5 minutes to 2 hours to allow the suspended matter in the fracturing flowback fluid to settle, thereby reducing the color of the fracturing flowback fluid and removing the suspended matter. Preferably, the amount of the bioflocculant added to the fracturing flowback fluid is 0.005g-1g / L, based on the amount of dry matter in the fermentation product of Providenciarettgeri sp. Hong 1Xiao Zong. In specific implementation, the solid bioflocculant can first be prepared into a solution of a certain concentration, and then added to the fracturing flowback fluid to be treated.

[0048] The method for treating fracturing flowback fluid of the present invention has no special requirements on the performance indicators of the fracturing flowback fluid to be treated and has a wide range of adaptability. Generally, the method for treating fracturing flowback fluid of the present invention is applicable to fracturing flowback fluids having a pH value of 3-11, a salinity of 1-150 g / L, a suspended matter concentration of 100-2000 mg / L, and a chromaticity of 0.1-0.6 (absorbance value measured by ultraviolet spectrophotometry at a wavelength of 380 nm). According to a specific embodiment of the present invention, the method for treating fracturing flowback fluid of the present invention can also be adjusted as needed to adjust the indicators of the fracturing flowback fluid to be treated within the above range before adding the bioflocculant for treatment. Generally, the pH value of the fracturing flowback fluid to be treated can be adjusted to 7-11, more preferably 8-11, as needed; the salinity of the fracturing flowback fluid to be treated (in terms of chloride ions and sodium ions) can be adjusted to 1 g / L-150 g / L, preferably 10 g / L-125 g / L.

[0049] When the bioflocculant of the present invention is used to treat fracturing flowback fluid, the chroma removal rate of the fracturing flowback fluid can reach above 42%-80%, and the suspended matter removal rate can reach above 60%-87%. In addition, the treatment method of the present invention does not cause secondary pollution to the environment, has significant application effects, and is easy to operate. It has good application prospects in the bioflocculant treatment of oilfield fracturing flowback fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The figure shows the treatment effect of the bioflocculant in one embodiment of the present invention on fracturing flowback fluid.

[0051] Figure 2 The results show the treatment effect of the bioflocculant in one embodiment of the present invention on fracturing flowback fluid under different pH conditions.

[0052] Figure 3 The figure shows the treatment effect of the bioflocculant in one embodiment of the present invention on fracturing flowback fluid at different salinities. DETAILED DESCRIPTION

[0053] In order to have a clearer understanding of the technical characteristics, purposes and beneficial effects of the present invention, now in conjunction with specific embodiments and accompanying drawings, the technical scheme of the present invention is described in detail below, it should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. For those skilled in the art, various changes and / or modifications easily thought of within the spirit of the present invention are all identified as being encompassed within the protection scope of the present invention. In the embodiments, each raw reagent material is commercially available, and the experimental method without specifying specific conditions is conventional method and normal condition known in the art, or according to the conditions recommended by the instrument manufacturer.

[0054] In each embodiment, the suspended matter concentration was measured by weighing using a 0.45 micron membrane filtration method; the color was measured by ultraviolet spectrophotometry at a wavelength of 380 nm, and the color removal rate was: (color absorbance value after treatment - color absorbance value before treatment) / color absorbance value before treatment.

[0055] Example 1: Preparation of bioflocculant and treatment of fracturing flowback fluid

[0056] Providencia rettgeri sp. Hong 1Xiao Zong (preserved in the laboratory of the inventor team, i.e., a strain with a deposit number of CGMCC No. 16545) was activated to prepare a seed solution. The activation medium was LB liquid medium (NaCl 10g / L, yeast extract 5g / L, tryptone 10g / L), and the culture was cultured to OD6000.8 to obtain a seed solution. The seed solution was inoculated with an inoculum size of 2% in 100mL of fermentation medium, wherein the fermentation medium composition was a glucose concentration of 10g / L, (NH4)SO4 0.2g / L, urea 0.5g / L, yeast extract 0.5g / L, KH2PO4 2g / L, K2HPO4 5g / L, NaCl 0.1g / L, and MgSO4 0.2g / L. Fermentation culture conditions: shaking speed 150r / min, temperature 30°C, and fermentation time 48h. After fermentation, the fermentation broth was centrifuged at 4°C and 6000 rpm for 10 minutes in a low-temperature refrigerated centrifuge to obtain a supernatant. The supernatant was then precipitated with two volumes of pre-cooled anhydrous ethanol (2-6°C) for 24 hours. The precipitated flocculent solid material was centrifuged and vacuum freeze-dried to obtain a fermentation product powder of Providencia rettgeri sp. Hong 1 Xiao Zong, which was used as the active ingredient in a bioflocculant. The yield of the fermentation product powder obtained from the supernatant was 1.5 g / L. Testing revealed a polysaccharide content of approximately 50.0% and a protein content of approximately 8.0%.

[0057] Bacillus sp.JS Xiao Bai (preserved in the laboratory of the inventor's team, i.e., a strain with a preservation number of CGMCC No.16546) was activated to prepare a seed solution. The activation medium was LB liquid medium (NaCl 10g / L, yeast extract 5g / L, tryptone 10g / L), and the seed solution was cultured to OD600 0.8. The seed solution was inoculated into 100mL fermentation medium at an inoculum size of 2%, wherein the fermentation medium composition was a glucose concentration of 10g / L, (NH4)SO4 0.2g / L, urea 0.5g / L, yeast extract 0.6g / L, KH2PO4 2g / L, K2HPO4 5g / L, NaCl 0.1g / L, MgSO4 0.2g / L. Fermentation culture conditions: shaker speed 120r / min, temperature 30°C, fermentation time 48h. After fermentation, the fermentation broth was centrifuged at 4°C and 5000 rpm for 10 minutes in a low-temperature refrigerated centrifuge to obtain a supernatant. The supernatant was then precipitated with 2 volumes of pre-cooled anhydrous ethanol (2-6°C) for 24 hours. The precipitated flocculent solid material was centrifuged and vacuum freeze-dried to obtain a powdered fermentation product of Bacillus sp. JS Xiao Bai, which was used as the active ingredient of a bioflocculant. The yield of the fermentation product powder obtained from the supernatant was 3.0 g / L. Testing revealed that the polysaccharide content was approximately 48.2% and the protein content was approximately 7.8%.

[0058] The dry powder of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the dry powder of the fermentation product of Bacillus sp. JS Xiao Bai are used as bioflocculants respectively; or the dry powder of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the dry powder of the fermentation product of Bacillus sp. JS Xiao Bai are mixed in a ratio of 1:3, 1:2, 1:1, 2:1 or 3:1 by mass to obtain a mixture as the bioflocculant.

[0059] The above-mentioned bioflocculants were respectively prepared into 5 g / L aqueous solutions with purified water and added at a 2% amount to Changqing Oilfield fracturing flowback fluid (pH 7.6, salinity 22790 mg / L, color absorbance of 0.43 at a wavelength of 380 nm as determined by ultraviolet spectrophotometry, and initial suspended matter concentration of 660 mg / L). The pH of the system was adjusted to 9, and the mixture was stirred for 30 seconds using a magnetic stirrer at 600 rpm. The mixture was allowed to stand for 20 minutes, and the color and suspended matter in the supernatant were detected.

[0060] In this embodiment, the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong was used to treat oilfield fracturing flowback fluid, with a color removal rate of 48% and a suspended solids removal rate of 65%.

[0061] The fermentation product of Bacillus sp.JS Xiao Bai was used to treat oilfield fracturing flowback fluid, with a color removal rate of 42% and a suspended matter removal rate of 60%.

[0062] The results of treating oilfield fracturing flowback fluid with bioflocculants prepared by compounding the fermentation products of Providencia rettgeri sp. Hong 1 Xiao Zong and Bacillus sp. JS Xiao Bai in different proportions can be found in Figure 1 Among them, the fermentation product of Providencia rettgerisp. Hong1 Xiao Zong and the fermentation product of Bacillus sp.JS Xiao Bai were mixed in a ratio of 2:1 to treat oilfield fracturing flowback fluid. Under the same dosage as that of a single fermentation substance, the color removal rate can be increased to 80%, and the suspended matter removal rate can be increased to 87%.

[0063] Example 2: Preparation of bioflocculant and treatment of fracturing flowback fluid

[0064] Providencia rettgeri sp. Hong 1Xiao Zong was activated and then fermented. The fermentation medium composition and fermentation conditions were the same as in Example 1. After the fermentation was completed, the pH value of the fermentation broth was adjusted to 9, heated to 60°C, ultrasonically treated at 40Hz for 4 minutes, and then centrifuged at 8000r / min for 15 minutes to obtain a supernatant. Thereafter, the supernatant was precipitated with alcohol under the same conditions as in Example 1, and the precipitated flocculent solid material was centrifuged and freeze-dried to obtain a fermentation product powder as the active ingredient of the bioflocculant. In this example, the yield of the fermentation product powder obtained from the supernatant was 3.5g / L. After testing, the polysaccharide content was approximately 50.2% and the protein content was approximately 8.2%.

[0065] Bacillus sp.JS Xiao Bai was activated and then fermented. The composition of the fermentation medium and the fermentation conditions were the same as in Example 1. After the fermentation, the pH value of the fermentation liquid was adjusted to 8, heated to 50°C, ultrasonically treated at 40Hz for 6 minutes, and then centrifuged at 8000r / min for 15 minutes to obtain a supernatant. Thereafter, the supernatant was obtained by alcohol precipitation under the same conditions as in Example 1, and the precipitated flocculent solid matter was centrifuged and freeze-dried to obtain a fermentation product powder as the active ingredient of the bioflocculant. In this embodiment, the yield of the fermentation product powder obtained from the supernatant was 4.5g / L. After testing, the polysaccharide content was about 53.6% and the protein content was about 7.5%.

[0066] The dry powder of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the dry powder of the fermentation product of Bacillus sp. JS Xiao Bai in this example are used separately as bioflocculants; or the dry powder of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the dry powder of the fermentation product of Bacillus sp. JS Xiao Bai in this example are compounded in a ratio of 2:1 by mass, and the obtained mixture is used as a bioflocculant.

[0067] The above bioflocculants were prepared into 5 g / L aqueous solutions with purified water and added to the Changqing Oilfield fracturing flowback fluid (same as in Example 1) at a concentration of 1%-8%. A coagulant aid, CaCl2, was also added at a concentration of 1%-8%. The mixture was stirred at a speed of 100-800 rpm for 30 seconds and allowed to stand for 5-30 minutes. The color and suspended matter in the treated supernatant were then detected.

[0068] In this example, the addition amount of the aqueous solution of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong was 4%, the addition amount of the coagulant CaCl2 was 5%, the magnetic stirrer speed was 600 rpm, and the standing time was 20 minutes. The color removal rate of the oilfield fracturing flowback fluid was 60%, and the suspended matter removal rate was 68%.

[0069] In this example, the addition amount of the aqueous solution of the fermentation product of Bacillus sp. JS Xiao Bai was 4%, the addition amount of the coagulant CaCl2 was 5%, the magnetic stirrer speed was 600 rpm, and the standing time was 15 minutes. The color removal rate of the oilfield fracturing flowback fluid was 55%, and the suspended matter removal rate was 60%.

[0070] In this example, a fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and a fermentation product of Bacillus sp. JS Xiao Bai were mixed in a ratio of 2:1 and used to treat oilfield fracturing flowback fluid. The addition amount was 4%, the coagulant aid CaCl2 was added in an amount of 4%, the magnetic stirrer speed was 600 rpm, and the standing time was 20 minutes. The color removal rate of the oilfield fracturing flowback fluid was 78.9%, and the suspended matter removal rate was 84.8%.

[0071] Example 3: pH environmental tolerance of bioflocculant-treated fracturing flowback fluid

[0072] This example explores the pH environmental tolerance of the composite flocculant of the present invention in treating fracturing flowback fluid.

[0073] Based on the fracturing flowback fluid of Changqing Oilfield (pH 7.6, salinity 22790 mg / L, colorimetric absorbance of 0.43 at 380 nm wavelength by ultraviolet spectrophotometry, initial suspended solids concentration 660 mg / L), HCl / NaOH was used to adjust the pH to 3-11. The fermentation product of Providencia rettgerisp. Hong 1 Xiao Zong and the fermentation product of Bacillus sp. JS Xiao Bai prepared in Example 2 were compounded in a ratio of 2:1, and the bioflocculant addition amount was 4%, the coagulant aid CaCl2 was added in an amount of 4%, and the mixture was stirred at a magnetic stirrer speed of 600 rpm for 30 seconds and then allowed to stand for 20 minutes. The color removal rate and suspended solids removal rate of the treated fracturing flowback fluid were detected. Results are shown in the table. Figure 2 It can be seen that the bioflocculant of the present invention is applicable to treating fracturing flowback fluid at different pH values, and is particularly suitable for alkaline environments, and has good alkali resistance.

[0074] Example 4: Tolerance of salinity in fracturing flowback fluid treated with bioflocculants

[0075] This example explores the salinity tolerance of the composite flocculant of the present invention in treating fracturing flowback fluid.

[0076] Based on the fracturing flowback fluid from the Changqing Oilfield, NaCl was added to adjust the salinity and the pH to 9. A bioflocculant (4%) and a coagulant (4%) were added to the fracturing flowback fluid, prepared in Example 2, using a mixture of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the fermentation product of Bacillus sp. JS Xiao Bai in a ratio of 2:1. The fluid was stirred at 600 rpm for 30 seconds and then allowed to stand for 20 minutes. The color removal rate and suspended solids removal rate of the treated fracturing flowback fluid were tested. Results are shown in the table. Figure 3 As shown (the salinity coordinates in the figure are based on the additional added NaCl). It can be seen that the bioflocculant used in the treatment of fracturing flowback fluid is suitable for treatment environments with higher salinity and has good salt tolerance.

[0077] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A bioflocculant comprising: Fermentation products of Providencia rettgeri sp. Hong1Xiao Zong.

2. The bioflocculant according to claim 1, wherein The fermentation product of Providenciarettgeri sp. Hong 1 Xiao Zong includes one or more of the following substances: Providencia rettgeri sp. Hong 1 Xiao Zong was inoculated into a fermentation medium for fermentation to obtain a fermentation liquid; Providencia rettgeri sp. Hong 1 Xiao Zong was inoculated into a fermentation medium for fermentation to obtain a fermentation supernatant; Providencia rettgeri sp. Hong 1 Xiao Zong is inoculated into a fermentation medium for fermentation, and the obtained fermentation liquid and / or fermentation supernatant is subjected to alcohol precipitation to obtain a solid substance. The bioflocculant according to claim 1 or 2, further comprising a fermentation product of Bacillus sp. JS XiaoBai.

4. The bioflocculant according to claim 3, wherein The fermentation product of Bacillus sp.JS Xiao Bai includes one or more of the following substances: Bacillus sp.JS Xiao Bai is inoculated into a fermentation medium for fermentation to obtain a fermentation liquid; Bacillus sp.JS Xiao Bai was inoculated into a fermentation medium for fermentation to obtain a fermentation supernatant; Bacillus sp. JS Xiao Bai is inoculated into a fermentation medium for fermentation, and the fermentation liquid and / or the fermentation supernatant are obtained by alcohol precipitation to obtain a solid substance.

5. The bioflocculant according to any one of claims 1 to 4, wherein Based on the total dry matter content of the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong and the fermentation product of Bacillus sp. JS Xiao Bai in the flocculant, the amount of dry matter in the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong is 10% to 100%, and the amount of dry matter in the fermentation product of Bacillus sp. JS Xiao Bai is 0% to 90%.

6. The bioflocculant according to claim 5, wherein the mass ratio of the fermentation product of Bacillus sp.JS Xiao Bai to the fermentation product of Providencia rettgeri sp.Hong 1 Xiao Zong, calculated on a dry matter basis, is 1:3 to 3:1, preferably 1:2 to 2:

1.

7. The bioflocculant according to any one of claims 1 to 6, which is a liquid preparation or a solid preparation.

8. The bioflocculant according to any one of claims 1 to 7, further comprising one or more of the following substances: Coagulant aids; Excipients and / or carriers.

9. The bioflocculant according to claim 8, wherein The coagulant aid includes calcium chloride; Preferably, the mass ratio of the dry matter in the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong to calcium chloride in the bioflocculant is 1:10-10000.

10. A method for preparing the bioflocculant according to any one of claims 1 to 9, the method comprising: Providencia rettgeri sp. Hong 1Xiao Zong was inoculated into a liquid fermentation medium for fermentation; The fermentation liquid obtained by fermentation is used directly, or after further separation and purification, with or without adding other substances to prepare the bioflocculant.

11. The method according to claim 10, wherein: The fermentation medium of Providencia rettgerisp. Hong 1 Xiao Zong comprises glucose, (NH4)SO4, urea and yeast extract, and may optionally comprise one or more of KH2PO4, K2HPO4, NaCl and MgSO4; Preferably, the fermentation medium of Providencia rettgeri sp. Hong 1Xiao Zong comprises: glucose 5-20 g / L, (NH4)SO4 0.2-3.6 g / L, urea 0.5-1 g / L, yeast extract 0.5-3.6 g / L, KH2PO4 2-5 g / L, K2HPO4 2-5 g / L, NaCl 0.1-1 g / L, and MgSO4 0.2-1 g / L.

12. The method according to claim 10, further comprising: Bacillus sp.JS Xiao Bai is inoculated into a liquid fermentation medium for fermentation. The fermentation liquid obtained is directly or after further separation and purification, combined as one of the raw materials with the fermentation product of Providenciarettgeri sp.Hong 1 Xiao Zong to prepare the bioflocculant.

13. The method according to claim 12, wherein: The fermentation medium of Bacillus sp.JS Xiao Bai comprises glucose, (NH4)SO4, urea and yeast extract, and may optionally comprise one or more of KH2PO4, K2HPO4, NaCl and MgSO4; Preferably, the fermentation medium of Bacillus sp.JS Xiao Bai Including: glucose 5-20g / L, (NH4)SO4 0.2-3.6g / L, urea 0.5-1g / L, yeast extract 0.5-3.6g / L, KH2PO4 2-5g / L, K2HPO42-5g / L, NaCl0.1-1g / L, MgSO4 0.2-1g / L.

14. The method according to any one of claims 10 to 13, wherein: The fermentation culture conditions of Providencia rettgeri sp. Hong 1Xiao Zong are as follows: a seed solution with an OD600 of 0.8-1.2, an inoculum size of 1%-10%, a fermentation temperature of 10°C-43°C, and a fermentation time of 24h-96h, preferably 28h-72h; The fermentation culture conditions of Bacillus sp.JS Xiao Bai are as follows: seed liquid with OD600 of 0.8-1.2, inoculated with an inoculum size of 1%-10%, fermentation culture temperature of 10°C-43°C, and fermentation culture time of 24h-96h, preferably 28h-72h.

15. The method according to any one of claims 10 to 14, further comprising: Centrifuging the fermentation broth obtained by fermenting Providencia rettgeri sp. Hong 1Xiao Zong to obtain a supernatant, and further subjecting the supernatant to alcohol precipitation to obtain a solid substance as an active ingredient of a bioflocculant; and / or The fermentation liquid obtained by fermenting Bacillus sp.JS Xiao Bai is centrifuged to obtain a supernatant, and the supernatant is further separated by alcohol precipitation to obtain a solid substance as an active component of a bioflocculant.

16. The method according to claim 15, comprising: The fermentation broth obtained by fermenting Providencia rettgeri sp. Hong 1Xiao Zong is ultrasonicated at pH 3-11 and temperature 20°C-80°C for 2-10 minutes, followed by centrifugation at 4°C and 5000-8000 rpm for 5-15 minutes to obtain a supernatant, 1-5 volumes of ethanol are added to the supernatant, and refrigerated for alcohol precipitation for 24-72 hours. The precipitated flocculent solid matter is separated and further dried or not as needed to use as the active ingredient of the bioflocculant; and / or The fermentation broth obtained by fermentation of Bacillus sp.JS Xiao Bai is ultrasonicated for 2-10 minutes at a pH of 3-11 and a temperature of 20-80°C, and then centrifuged at 4°C and 5000-8000 rpm for 5-15 minutes to obtain a supernatant. The supernatant is added with 1-5 times the volume of ethanol and refrigerated for alcohol precipitation for 24-72 hours. The precipitated flocculent solid matter is separated and further dried or not dried as needed to serve as the active ingredient of the bioflocculant.

17. Use of the bioflocculant according to any one of claims 1 to 9 in the preparation of a treatment agent for treating fracturing flowback fluid to reduce its color and remove suspended matter.

18. A method for treating fracturing flowback fluid, the method comprising: The bioflocculant according to any one of claims 1 to 9 is used to treat fracturing flowback fluid to reduce the color of the fracturing flowback fluid and remove suspended matter.

19. The method according to claim 18, wherein Add the bioflocculant to the fracturing flowback fluid to be treated, stir evenly, and then let it stand for 5 minutes to 2 hours to allow the suspended matter in the fracturing flowback fluid to settle, thereby reducing the color of the fracturing flowback fluid and removing the suspended matter; Preferably, the amount of the bioflocculant added to the fracturing flowback fluid is 0.005 g-1 g / L, calculated based on the amount of dry matter in the fermentation product of Providencia rettgeri sp. Hong 1 Xiao Zong.

20. The method according to claim 19, further comprising: The pH value of the fracturing flowback fluid to be treated is adjusted to 3-11 and the salinity is adjusted to 1g / L-150g / L, and then the bioflocculant is added for treatment.

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